DPLUS051

Water Security and Sustainable Cloud Forest Restoration on St Helena

Authors: Ben Sansom Alan Gray Mike Jervois Samantha Cherrett Connect Saint Helena

DPLUS051 Project Report

Contents

EXECUTIVE SUMMARY ...... I 1 INTRODUCTION ...... 1 1.1 BACKGROUND ...... 1 1.2 METHODOLOGY ...... 1 1.2.1 Desk Study ...... 2 1.2.2 Baseline Field Assessment ...... 2 1.2.3 Environmental Monitoring ...... 2 1.2.4 Interpretation of Data ...... 2 1.3 ACKNOWLEDGEMENTS ...... 3 1.4 PROJECT LOGFRAME ...... 3 2 SAINT HELENA ...... 5 2.1 LOCATION ...... 5 2.2 HISTORY ...... 5 3 TROPICAL MONTANE CLOUD FORESTS ...... 7 4 CLIMATE ...... 9 4.1 THE ISLAND ...... 9 4.2 DROUGHT ...... 11 4.3 EVAPORATION ...... 14 4.4 POTENTIAL EVAPOTRANSPIRATION (PE) ...... 14 4.5 ST HELENA’S CLOUD FOREST ...... 16 5 MIST CAPTURE AND RAINFALL HARVESTING ...... 18 5.1 MIST COLLECTION INSTRUMENTATION ...... 18 5.2 DPLUS051 INSTRUMENTATION ...... 20 5.3 MIST CAPTURE ON ST HELENA ...... 21 6 GEOLOGY ...... 23 6.1 ISLAND GEOLOGY ...... 23 6.2 GEOLOGY OF THE STUDY AREA ...... 25 7 SOIL ...... 26 7.1 ST HELENA’S SOIL ...... 26 7.2 SOILS IN THE STUDY AREA ...... 26 8 THE ECOLOGY OF ST HELENA ...... 29 8.1 HISTORIC ACCOUNTS ...... 29 8.2 THE CLOUD FOREST ...... 29 8.3 CLOUD FOREST VEGETATION AND PLANT SPECIES ...... 30 8.4 INVASIVE SPECIES ...... 32 9 WATER RESOURCES ...... 33 9.1 HYDROLOGY ...... 33 9.2 WATER DISTRIBUTION NETWORK ...... 34

DPLUS051 Project Report

9.2.1 Wells Gut and Grapevine Gut ...... 36 9.2.2 Combined Raw Water Abstraction ...... 38 9.2.3 Annual Treated Water Consumption ...... 39 9.3 HYDROGEOLOGY ...... 40 9.4 WATER BALANCE MODEL ...... 41 10 WATER FEATURES SURVEY ...... 43 10.1 GRAPEVINE GUT ...... 44 10.1.1 Catchpit 1 ...... 44 10.1.2 Catchpit 2 ...... 44 10.2 WELLS GUT ...... 46 10.2.1 Catchpit 1 ...... 46 10.2.2 Wells Gut Catchpit 2 ...... 47 10.2.3 Wells Gut Catchpit 3 ...... 47 10.3 BYRONS GUT ...... 49 10.3.1 Byrons Gut Spring Source ...... 49 10.3.2 Byrons Gut Catchpit ...... 49 10.4 SOURCES OF WATER ...... 51 11 REMOTE SENSING ...... 52 11.1 AERIAL SURVEYS ...... 52 11.1.1 Selection of a Drone ...... 53 11.1.2 Airspace Regulation ...... 55 11.1.3 Regulatory Permissions ...... 55 11.1.4 Flight Planning ...... 56 11.2 AERIAL IMAGES AND DATA PROCESSING ...... 57 11.2.1 Orthomosaic ...... 58 11.2.2 Digital Elevation Model (DEM) ...... 58 11.2.3 Calculated Watershed and Catchment Area ...... 59 12 VEGETATION SURVEY ...... 66 12.1 METHODOLOGY ...... 66 12.2 VEGETATION SURVEY CATEGORIES AND MAP ...... 66 12.2.1 Flax ...... 67 12.2.2 Tree fern thicket ...... 67 12.2.3 Black scale fern ...... 67 12.2.4 Mixed flax and Whiteweed ...... 67 12.2.5 Jellico ...... 67 12.2.6 Yam ...... 69 12.2.7 Pasture ...... 69 12.2.8 Forestry trees ...... 69 12.3 GRAPEVINE GUT PLANT ECOLOGY ...... 69 12.4 WELLS GUT PLANT ECOLOGY ...... 69 12.5 INVASIVE SPECIES CONTROL ...... 69 12.6 ENDEMIC PLANT RESTORATION TECHNIQUES ...... 70 12.7 LONG TERM CHANGES IN VEGETATION ...... 71

DPLUS051 Project Report

13 MONITORING NETWORK ...... 71 13.1 MONITORING LOCATION SELECTION ...... 71 13.2 MONITORING EQUIPMENT ...... 72 13.3 MEETINGS AND TRAINING ...... 73 13.4 DATA COLLECTION ...... 73 13.5 SITE SECURITY ...... 73 14 MONITORING DATA AND INTERPRETATION ...... 80 14.1 WIND SPEED AND DIRECTION ...... 84 14.1.1 Perkins Gut ...... 84 14.1.2 Grapevine Gut ...... 84 14.1.3 Wells Gut ...... 86 14.1.4 Wind Data Summary ...... 87 14.2 TEMPERATURE AND HUMIDITY ...... 87 14.3 BAROMETRIC PRESSURE ...... 94 14.4 RAINFALL AND MIST ...... 100 14.5 SOIL MOISTURE ...... 107 14.6 SURFACE WATER ...... 112 14.6.1 Grapevine Gut ...... 114 14.6.2 Wells Gut and Byrons Gut ...... 120 14.7 POTENTIAL EVAPOTRANSPIRATION (PE) ...... 127 14.8 THE 2016 TO 2017 DROUGHT ...... 129 14.8.1 Stream Level Response to Mist and Rainfall ...... 133 14.8.2 Soil Moisture Response to Mist and Rainfall ...... 134 15 SUB-CATCHMENT WATER BALANCE ...... 137 16 CLIMATE CHANGE ASSESSMENT ...... 140 16.1 CLIMATE CHANGE DATA ...... 140 16.1.1 University of Cape Town Climate Information Platform ...... 141 16.1.2 World Bank Climate Change Knowledge Portal ...... 144 16.2 CLIMATE CHANGE RISKS ...... 148 16.3 WATER DEMAND ...... 149 16.4 TOURISM AND WATER DEMAND ...... 151 16.5 CLIMATE CHANGE IMPACTS ON WATER SUPPLY ...... 153 17 OUTLINE CLOUD FOREST RESTORATION PLAN ...... 153 18 ECOSYSTEMS SERVICES ASSESSMENT ...... 156 19 INCREASING MIST AS RAINFALL FOR PUBLIC WATER SUPPLY ...... 159 20 CONCLUSIONS AND RECOMMENDATIONS ...... 161 20.1 AERIAL SURVEYS ...... 161 20.2 VEGETATION SURVEY ...... 162 20.3 WIND, TEMPERATURE AND HUMIDITY ...... 162 20.4 RAINFALL AND MIST ...... 163 20.5 SOIL MOISTURE ...... 163 20.6 STREAM FLOWS ...... 163

DPLUS051 Project Report

20.7 POTENTIAL EVAPOTRANSPIRATION ...... 164 20.8 WATER BALANCE ...... 164 20.9 CLIMATE CHANGE ...... 165 20.10 CLOUD FOREST RESTORATION ...... 166 20.11 ECOSYSTEMS SERVICES ASSESSMENT ...... 166 20.12 A FUTURE SOURCE OF WATER ...... 167 20.13 RECOMMENDATIONS ...... 167 BIBLIOGRAPHY ...... 169 APPENDIX A: PROJECT TASKS AND PROGRAMME ...... 173 APPENDIX B: SHG RESILIENCE FORUM DROUGHT NOTICES 2016 TO 2017 ...... 178 APPENDIX C: SPECIES NAMES MENTIONED IN THE TEXT ...... 200 APPENDIX D: DRONE OPERATIONS MANUAL ...... 202 APPENDIX E: TEMPLATE DRONE OPERATIONS MANUAL ...... 204 APPENDIX F: FLIGHT PLANS ...... 206 APPENDIX G: MONITORING MANUAL V1.1 ...... 208

Figures

Figure 1: St Helena Location Plan ...... 6

Figure 2: Saint Helena Long Term Average Rainfall and Temperature (1892 to 2014) ...... 10

Figure 3: Bottom Woods MET Station Rainfall ...... 10

Figure 4: St Helena's Weather Stations ...... 12

Figure 5: St Helena Long Term Mean Rainfall Isohyets ...... 13

Figure 6: Bottom Woods MET Station Monthly Evaporation 2016 to 2018 ...... 14

Figure 7: Bottom Woods PE (1978 to 1988) ...... 15

Figure 8: Hutts Gate PE (1971 to 1975) ...... 16

Figure 9: Hutts Gate Rainfall Record 1926 to 2017 ...... 17

Figure 10: Peaks National Conservation Area Rainfall Record ...... 17

Figure 11: Hutts Gate and Peaks Nursery Rainfall ...... 18

Figure 12: Hutts Gate Mist Capture ...... 22

Figure 13: Geology of St Helena ...... 24

DPLUS051 Project Report

Figure 14: Soil Map of St Helena ...... 27

Figure 15: Historic Spring and Stream Flows in Wells and Byrons Gut ...... 34

Figure 16: Hutts Gate Spring Water Collection and Distribution Network ...... 35

Figure 17: Upper Wells Gut Raw Water Flows (2007 to 2017) ...... 36

Figure 18: Lower Wells Gut Monthly Raw Water Flows (2007 to 2017) ...... 37

Figure 19: Average Monthly Flows: Upper and Lower Wells Gut (2007 to 2017) ...... 37

Figure 20: Grapevine Gut Monthly Pumped Raw Water Flows 2014 to 2017 ...... 38

Figure 21: Wells Gut and Grapevine Gut Monthly Pumped Raw Water 2014 to 2017 ...... 39

Figure 22: Saint Helena Annual Treated Water Consumption 2009 to 2017 ...... 39

Figure 23: Hydrogeology Conceptual Model of Saint Helena – Lawrence, 1983 ...... 40

Figure 24: Grapevine Gut Land Use, Mathieson 1990 ...... 43

Figure 25: Image Resolution Changing with Ground Level ...... 58

Figure 26: Wells Gut and Grapevine Gut Orthomosaic ...... 60

Figure 27: Wells Gut and Grapevine Gut Digital Elevation Model ...... 61

Figure 28: Long Profile and Cross Section Locations ...... 62

Figure 29: Sub-catchment Long Profiles and Cross Sections ...... 63

Figure 30: Study Area Calculated Watershed ...... 64

Figure 31: Study Area Catchment Areas ...... 65

Figure 32: Wells Gut and Grapevine Gut Vegetation Survey ...... 68

Figure 33: iButton, Barometric Logger and Weather Station Monitoring Locations ...... 75

Figure 34: Surface Water, Flow, Mist Capture and Soil Moisture Logger Monitoring Locations ...... 76

Figure 35: Perkins Gut Wind Rose ...... 85

Figure 36: Grapevine Gut Wind Rose ...... 85

Figure 37: Grapevine Gut Wind Speed Frequency ...... 86

Figure 38: Wells Gut Wind Rose ...... 86

Figure 39: iButton Temperature and Humidity ...... 90

Figure 40: Temperature Isohyet 2016 to 2017 ...... 91

DPLUS051 Project Report

Figure 41: Humidity Isohyet 2016 to 2017 ...... 92

Figure 42: Average 24h Temperature and Humidity ...... 93

Figure 43: Barometric Pressure Data ...... 96

Figure 44: Pearson’s R - BP01WG and Bottom Woods Met Station ...... 97

Figure 45: Pearson's R - WS02GVG and Bottom Woods Met Station ...... 97

Figure 46: Pearson's R - BP01GVG and Bottom Woods Met Station ...... 98

Figure 47: Hind Cast and Forecast Barometric Pressure ...... 99

Figure 48: Monthly Mist 2016 to 2018 ...... 103

Figure 49: Monthly Rainfall 2016 to 2018 ...... 104

Figure 50: Wells Gut Monthly Rainfall and Mist ...... 105

Figure 51: Pearson's R - MC01DP and RF01WG ...... 108

Figure 52: Mist and Elevation ...... 109

Figure 53: Soil Moisture ...... 110

Figure 54: Monthly Average Soil Moisture and Air Temperature ...... 111

Figure 55: SW01GVG Surface Water Levels ...... 115

Figure 56: SW02GVG Surface Water Levels ...... 116

Figure 57: Grapevine Gut Monthly Stream Flow ...... 117

Figure 58: SW01WG Surface Water Levels ...... 121

Figure 59: SW02WG Surface Water Levels ...... 122

Figure 60: SW03WG Surface Water Levels ...... 123

Figure 61: SW01BG Surface Water Levels ...... 124

Figure 62: Wells Gut and Byrons Gut Monthly Stream Flow ...... 125

Figure 63: Monthly PE, Rainfall and Mist ...... 130

Figure 64: Surface Water Level and Rainfall (November 2016 to March 2017) ...... 131

Figure 65: Surface Water Level, Mist and Rainfall (November 2016 to March 2017) ...... 132

Figure 66: Daily Stream Flow and Rainfall Hydrogaph SW03WG ...... 135

Figure 67: Rainfall, Mist and Soil Moisture (November 2016 to March 2017) ...... 136

DPLUS051 Project Report

Figure 68: Annual Average Temperature and Rainfall for St Helena ...... 141

Figure 69: St Helena Average Maximum Temperature RCP4.5 ...... 142

Figure 70: St Helena Average Minimum Temperature RCP4.5 ...... 142

Figure 71: St Helena Total Monthly Rainfall RCP4.5 ...... 143

Figure 72: St Helena Maximum Daily Rainfall RCP4.5 ...... 143

Figure 73: St Helena Number of Wet Days RCP4.5 ...... 144

Figure 74: Modelled Change in Temperature (2080-2090) ...... 145

Figure 75: Modelled Change in Rainfall (2080-2090) ...... 145

Figure 76: Change in Modelled Average Monthly Rainfall (2050) ...... 146

Figure 77: Modelled Days with Heavy Rainfall (2020 to 2100) ...... 147

Figure 78: Modelled Consecutive Dry Days (2020 to 2100) ...... 147

Figure 79: Saint Helena Water Treated Consumption Per Person Per Day ...... 150

Figure 80: St Helena Resident Population Census Data, 1901 to 2016 ...... 151

Figure 81: Proposed Restoration Area and Buffer Zone ...... 155

Tables

Table 1: Logframe and Report Sections ...... 3

Table 2: Saint Helena Long Term Average Rainfall and Temperature (1892 to 2014) ...... 10

Table 3: St Helena Catchment Areas* ...... 33

Table 4: Grapevine Gut Land Use, 1990 ...... 42

Table 5: Fixed Wing vs Multi-Rotor Drones ...... 54

Table 6: Area of Sub-catchments ...... 59

Table 7: Sub-Catchment Vegetation Classification ...... 66

Table 8: Monitoring Equipment ...... 74

Table 9: Staff Present at Fieldwork Inception Meeting ...... 77

Table 10: Project Field Data Collection Logbook ...... 77

Table 11: Field Monitoring Data Record ...... 80

Table 12: Climate Data Equipment ...... 83

DPLUS051 Project Report

Table 13: Temperature Data ...... 88

Table 14: Humidity Data ...... 89

Table 15: Monthly Mist Data ...... 101

Table 16: Monthly Rainfall Data ...... 102

Table 17: Long Term Mist and Rainfall ...... 106

Table 18: Pearson's R - Rainfall and Mist ...... 107

Table 19: Grapevine Gut Surface Water Flows ...... 114

Table 20: Grapevine Gut Stream Flow and Abstraction ...... 118

Table 21: Grapevine Gut Stream Flow and Reservoir Rates of Fill ...... 119

Table 22: Wells Gut and Byrons Gut Surface Water Flows ...... 120

Table 23: Wells Gut and Byron Gut Stream Flow and Abstraction ...... 126

Table 24: Monthly PE, Rainfall and Mist ...... 129

Table 26: Water Balance Climate Data ...... 138

Table 27: Grapevine Gut Water Balance ...... 138

Table 28: Wells Gut Water Balance ...... 139

Table 29: JNCC Climate Change Biodiversity Guiding Principals ...... 149

Table 30: Predicted Tourism Increase ...... 152

Table 31: St Helena Cloud Forest Ecosystem Services ...... 157

Table 32: Cloud Forest Restoration Cost Comparison ...... 160

Table 33: Project Partner Roles, Responsibilities and Deliverables ...... 174

Table 34: Project Programme ...... 176

Plates

Plate 1: Mist over the Peaks National Park ...... 8

Plate 2: Mist Collectors ...... 19

Plate 3: CEH Hybrid Mist Collector ...... 20

Plate 4: Hutts Gate Mist Collector ...... 22

DPLUS051 Project Report

Plate 7: Trachyte Dyke on the Central Peaks Road ...... 25

Plate 8: Neutron probe aluminium access tube ...... 28

Plate 5: Tree Fern Thicket Central Ridge ...... 30

Plate 6: Flax Blanketing Steep Faces of the Central Ridge Towards Halley’s Mount ...... 31

Plate 9: Grapevine Gut Catchpit 1 ...... 45

Plate 10: Grapevine Gut Catchpit 2 ...... 45

Plate 11: Wells Gut Catchpit 1 ...... 46

Plate 12: Wells Gut Catchpit 2 ...... 48

Plate 13: Wells Gut Above Ground Storage Header Tanks ...... 48

Plate 14: Wells Gut Catchpit 3 and V-Notch Weir ...... 49

Plate 15: Byrons Gut Spring Source ...... 50

Plate 16: Byrons Gut Catchpit ...... 50

Plate 17: Seepage Face in Wells Gut ...... 51

Plate 18: DJI Phantom 4 Drone ...... 55

Plate 19: Saint Helena Airport Drone Flying Zones ...... 56

Plate 20: Grapevine Gut Reservoir Stream Inflow Pipes ...... 113

DPLUS051 Project Report

Executive Summary

St Helena has experienced unpredictable weather in recent years, which has led to two droughts in the past five years. The island has a very high dependency on rainfall to replenish water supplies and with the planned increase in eco-tourism, water demand is expected to rise whilst climate change is likely to further impact on weather patterns.

The islands 20-Year Water Resource Masterplan outlines development and management of island water resources to provide security of supply and enable resilience to climate change. The preferred development approach is through rainwater harvesting. This Darwin Plus funded study has been designed to prove or disprove the following hypothesis:

Improving mist capture in the Peaks national park through restoring endemic cloud forest would increase available water resources and provide more cloud forest habitat for at risk endemic plants and invertebrates.

The study area comprised two sub-catchments, Grapevine Gut and Wells Gut (including Byrons Gut) within the Peaks National Conservation Area, which feed spring and stream water to Hutts Gate water treatment works. Field data was collected between October 2016 and June 2018. The study has been completed with the support of SHG, Connect Saint Helena, EMD, ANRD, Centre for Ecology and Hydrology, SHNT and Royal Botanical Gardens KEW.

KEY POINTS

• The study area provides 38% of the islands water supply;

• Mist comprises over 60% of precipitation (mist + rainfall) during the year (3,090mm mist and 2,048mm rainfall) and is the main source of precipitation for the island during the summer months;

• Rainfall recorded at Grapevine Gut is 3.9 times higher than at Bottom Woods Met Station in 2017;

• Mist forms at a higher elevation on the windward (south east) side of the Peaks in Perkins Gut than on the leeward side in Wells Gut. The minimum height above sea level that mist forms is 690mASL;

• Grapevine Guts catchment area is 32% larger than Wells Gut, but stream flows are only 1.9% of the total flows measured in Wells Gut, indicating that significantly more water leaves the Wells Gut sub-catchment as surface water flow;

• The higher flows in Wells Gut may be due to the larger proportion of endemic cloud forest vegetation and higher proportion of peaty subsoil beneath the endemic cloud forest, holding back rainfall runoff, reducing direct recharge to aquifers, and releasing water in a slower less “flashy” flow. The native cloud forest canopy of St Helena is structurally more complex than the other vegetation types found in Wells Gut. As canopy ‘roughness’ increases mist capture, it is not unreasonable to assume that restoration of cloud forest will increase mist capture and hence water supply whilst also safeguarding and increasing the biodiversity of the restored areas;

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DPLUS051 Project Report

• Stream flows as a proportion of each water balance vary significantly between the two sub- catchments indicating that the relationship between sub-catchment geology, soils, rainfall recharge, dry weather flow and spring flows is the key to understanding how water reaches the streams from mist and rainfall;

• The 18-month wind, temperature and humidity data set indicate that there are differences in micro-climate between each Gut. Wind direction is mainly from the south and south east however there are variations which are controlled by topography. Wells Gut maintained a more constant temperature through all seasons than Grapevine Gut, however Grapevine Gut had a more consistent humidity across the seasons; and

• The use of drones for aerial photography was successful and demonstrated that this technology can enhance conservation work as the data can be used to map vegetation, water catchments, measure the success of invasive species removal and cloud forest restoration programmes, reduce health and safety risks associated with remote field work, plan conservation work and assess changes in habitat over time.

CLIMATE CHANGE AND WATER SUPPLY

• Temperatures in the region are rising and will increase an average of 2oC by 2099. Changes in rainfall are predicted to fluctuate between -2.50mm and +2.05mm per month by 2099, with the number of consecutive dry days increasing up to 48% on the present day;

• The way the island receives its water is going to change due to climate change. The number and distribution of wet and dry days will change along with rainfall intensity;

• Encouraging a larger area of cloud forest and developing a richer peaty subsoil in the Peaks will help even out the islands yearly water supply by slowing rainfall runoff and releasing water in a slower less “flashy” flow. Stream data show that it only takes 3 days for rainfall to reach the streams in the Peaks, limiting the time that water stays within the catchments; and

• Data suggest that endemic native habitats are potentially more resilient to climate change than the introduced vegetation. The climate change assessment identified altitudinal shifts in the vegetation zone as being critical for the endemic plants and invertebrates within Grapevine Gut and Wells Gut, as a shift in the vegetation zone could significantly reduce the size of the cloud forest.

A FUTURE SOURCE OF WATER

The 20-Year Water Resource Masterplan outlines a preferred water supply development approach through rainwater harvesting (mist capture). The study has shown that mist is a significant source of water for the island and is the dominant source of water during the summer months.

Mist capture/rainwater harvesting should be used to improve the reliability of the island’s water supply.

Mist capture provides an opportunity of increasing the amount of water that reaches the island throughout the year, whilst also improving a significant source of rare biodiversity and habitat. There

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DPLUS051 Project Report are identifiable benefits for drinking water, food production, ecotourism, public health and mitigating the effects of climate change.

The water balance and ecosystems services assessment show that 1m2 of catchment within Wells Gut provides the equivalent of 2m3 water per annum. Costs of restoring 1m2 of cloud forest for water supply will be in the region of £58/m3. Ongoing costs of water should be significantly reduced as they will be limited to habitat maintenance.

The cost of water relationship with cloud forest restoration enables a staged restoration programme to be implemented based upon water demand and water resource planning, spreading the costs of restoration to the 690mASL contour.

The total costs of restoring both catchments to the 690m contour is estimated to be only 4% of the annual DEFRA biodiversity budget (2016 to 2017), presenting a very cost effective method of increasing globally important biodiversity. Essentially, this would protect up to 1/3 of the UK mainland and Overseas Territory endemic biodiversity, increase St Helena cloud forest habitat by 40% and would meet commitments to the convention on biological diversity and the global plant conservation strategy. The potential benefit to the island’s water supply could be up to an additional 146,886m3/a through additional mist capture. This is equivalent to 33% of water treated annually for public consumption.

Restoration of the cloud forest not only brings opportunities for improving the islands water supply, but also provides an opportunity to significantly enhance the islands international reputation for nature conservation. Cloud forest restoration would also support efforts to develop an eco-tourism economy by providing evidence of the island’s connection with its rich natural resource and desire to be climate change resilient.

Costs of restoring cloud forest indicate that bringing additional water to the island through improvements in mist capture is initially more expensive than the costs of water storage infrastructure. Planning for these costs will require a change in thinking across Government, the private sector and society.

Water is seen as a free commodity, with only the costs of abstraction, storage, treatment and distribution being considered. This has to change. If water is seen as a product, then the cost of production also needs to be accounted for. Mist capture is a means of increasing the production of water in a sustainable way. The calculation of the cost/benefits to society of securing habitat for 1/3 of the UK’s endemic biodiversity is almost impossible.

RECOMMENDATIONS

It is recommended that:

• Permanent surface water monitoring equipment should be installed in all water supply catchments on St Helena to measure stream flows, baseflow and to develop minimum low flows for supporting surface water habitats and ecosystems. The study confirmed that there were no long-term records of continuous stream or spring flow on the island;

• Mist, rainfall and stream flow measurements continue within Wells Gut and Grapevine Gut to support accurate long-term interpretation of sub-catchment climate and hydrology and to update the water balance;

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• A hydrogeology investigation of the island (including the Peaks) is needed to fully understand the relationship between geology, soils, rainfall recharge, dry weather flow and spring flows; • Grapevine Gut reservoir inflows and outflows should be measured using in-line flow meters to accurately record the reservoir water balance;

• Water infrastructure design and construction schemes need to ensure that built infrastructure measurements are accurately recorded (as-built drawings) and retained for future reference;

• Capital investment to reduce leakage in the water distribution network needs to continue to further improve the efficient use of the islands limited water resources;

• Treated water data and billed water consumption data are checked regularly to assess losses from leakage and to calculate accurate water consumption values (l/p/d) for comparison with other nations and to track water efficiency targets;

• A trial cloud forest restoration programme is agreed between Connect, SHG and stakeholders in Wells Gut (including Byrons Gut), to monitor and measure changes in stream flow associated with cloud forest restoration. The data will be used to accurately quantify the additional water that mist capture through restored cloud forest brings to the island and update costs of restoration;

• Future restoration programmes select the best available technique to restore the cloud forest, limit the potential for soil erosion during restoration of habitat and look for opportunities to limiting time consuming and costly habitat maintenance;

• Drones are used to monitor habitat change and the management of conservation habitat; and • JNCC climate change guiding principles for biodiversity conservation are used as a climate change mitigation and adaptation check-list for all proposed development and conservation work on the island.

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DPLUS051 Project Report

1 Introduction

1.1 Background

St Helena has experienced unpredictable weather in recent years, which has led to two droughts in the past five years. The island has a very high dependency on rainfall to replenish water supplies. With the planned increase in eco-tourism of up to 30,000 visitors per year, water demand is expected to rise, whilst climate change is likely to further impact on weather patterns.

The 20-Year Water Resource Masterplan outlines development and management of island water resources to provide security of supply and enable resilience to climate change. The preferred development approach is through rainwater harvesting.

Improving mist capture in the Peaks national park through restoring endemic cloud forest could potentially increase available water resources and provide more cloud forest habitat for at risk endemic plants and invertebrates.

This project has been designed to provide sub-catchment scale water balances to verify the relationship between cloud forest, mist capture and impact of invasive species on water supply. Outcomes will support development of a cloud forest restoration plan.

The project addresses National Goal 3: Effective Management of the Environment, and Sustainable Development Plan targets:

5.3 – Meeting predicted growth in demand for water;

8.1 – Safeguarding the terrestrial and marine environments for future generations; and

8.2 – Environment mainstreamed across Saint Helena Government and private sector.

The project is a collaboration between Saint Helena Government (Environmental Management Division and Agricultural and Natural Resource Division), Connect Saint Helena (the islands utility), the Centre for Ecology and Hydrology (CEH) and Arctium.

1.2 Methodology

Two sub-catchments in the Peaks cloud forest were chosen for their current habitat distribution and significance St Helena’s supply are:

• Grapevine Gut (exclusively invasive species); and • Wells Gut (partially endemic species).

The project was split into four key elements:

1. Desk study; 2. Baseline field assessment; 3. Environmental monitoring; and 4. Data interpretation.

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1.2.1 Desk Study

The desk study comprised the collation of all available reports and data associated with climate, the cloud forest and mist capture in associated with the study area; including a review of catchment management and catchment mist and flax clearing studies written by the Centre for Ecology and Hydrology (Gunston and Rosier, 1997, 2002; Gunston, 2001; Rosier, 2001).

1.2.2 Baseline Field Assessment

The baseline field assessment comprised the following activities:

Botanical survey – to confirm the assemblage of endemic and invasive species and coverage, including an evaluation of field survey data collected by the Darwin Plus project DPLUS029, Securing St Helena’s rare cloud forest trees and associated invertebrates (Malan and Darlow, 2018).

Aerial survey – using a small unmanned surveillance aircraft (drone) to assist the botanical survey with tree canopy orthomosiac mapping and to identify potential environmental monitoring locations.

Water features survey – to confirm the location of springs, streams, water control structures, stand pipes, boreholes etc. within the study area.

Digital Terrain Model (DTM), GIS and remote sensing – creation of a DTM for each sub-catchment and interpretation of soil moisture, geology, soil cover and vegetation mapping data with the support of research project DPLUS052.

Monitoring network - to identify locations for installation of 3 portable meteorological stations (to measure rainfall, temperature, barometric pressure, relative humidity, wind speed and direction) and additional locations for the installation of temperature and humidity loggers, barometric loggers, surface water loggers and soil moisture loggers.

1.2.3 Environmental Monitoring

Field monitoring equipment was installed by the Environmental Management Division (EMD) of Saint Helena Government (SHG), Arctium and Connect Saint Helena (Conenct). CEH provided support concerning the overall monitoring network design and the selection of monitoring equipment. In addition to equipment installation, EMD and Connect Saint Helena collected data on a quarterly basis, cleared vegetation which had grown around instrumentation and maintained equipment. Arctium supported the data collection on two occasions in October 2016 and November 2017. Staff in the Agricultural and Natural Resource Division (ANRD) of SHG also provided data from weather stations they monitor around the study area.

1.2.4 Interpretation of Data

The data collected in the field was then interpreted with the following outputs in mind:

• Trend analysis - Collation and graphing of all water level and flow data - trend analysis; • St Helena climate - Collation of meteorological data and comparison with long term data sets from Bottom Woods meteorological station operated by the UK Met Office;

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• Cloud Forest Habitat - Botanical survey data interpretation and drafting of an outline cloud forest restoration plan with support from the Conservation team in EMD; • Hydrology - Sub-catchment water balance; • Ecosystems Interactions - Determine relationships between micro-climate, vegetative cover (abundance of endemic plants vs invasive species) and ground conditions; • Ecosystem services assessment; • Climate change assessment; and • Recommendations for further studies and water management options.

1.3 Acknowledgements

This project has been a collaboration between EMD, ANRD, Connect and CEH. We would like to thank Derek Henry and Trevor Graham (Environment and Natural Resource Directorate) who directed the project and Barry Hubbard and Leon de Wet from Connect for supporting the project, alongside the Connect GIS team led by Ricardo Fowler.

We would also like to thank Elizabeth Cairns-Wickes, Lourens Malan, and Paul Cherrett in EMD; and Darren Duncan, Freddie Green and Martina Leo from ANRD for all their support, encouragement and knowledge.

A special thanks is also due to Colin Clubb and the remote sensing team at the Royal Botanic Gardens Kew for additional support with drone flying and Saint Helena’s endemic biodiversity and Jeremy Harris, Director of the Saint Helena National Trust for encouragement and advice.

1.4 Project Logframe

Table 1 summarises the project logical framework (logframe) and identifies report chapters and documents associated with each output of the logframe.

Table 1: Logframe and Report Sections

Logframe Outputs Measurable Indicators Report Sections

Outcome: 0.1 Desk study. Demonstrate that restoring the 0.2 Collection of microclimate cloud forest will increase data. harvested rainfall and meet the 0.3 Botanical survey of each sub- islands water demand, whilst catchment. improving climate change resiliency and significantly 0.4 Water balance. increase habitats for endemic plants and invertebrates. 0.5 Reporting and outline cloud forest restoration plan.

1. Desk Study - to collate 1.1 Visit Kew and CEH in the UK 2 Saint Helena archive data. to collate desk-based data. 3 Tropical Montane Cloud Forests Desk based assessment of 1.2 4 Climate ANRD archive in the 5 Mist Capture and Rainfall Harvesting

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Logframe Outputs Measurable Indicators Report Sections

Scotland library on Saint 6 The Ecology of St Helena Helena. 7 Geology 1.3 Desk study report. 8 Soil 9 Water Resources 16 Climate Change Assessment 18 Ecosystems Services Assessment 2. Baseline Field Assessment 2.1 Completion of botanical 10 Water Features Survey surveys. 11 Remote Sensing 2.2 Completion of remote 12 Vegetation Survey sensing/aerial surveys. Also, see flight Operation Manual and 2.3 Water features survey Flight Plans (provided separately from this report). 3. Environmental Monitoring 3.1 Installation of hydrology and 13 Monitoring Network hydrogeology monitoring Also, see DPLUS051 Monitoring locations. Network Manual v1.1 (provided 3.2 Installation of meteorological separately from this report). monitoring equipment and 14 Monitoring Data relative humidity loggers in both sub-catchments. Includes description of monitoring record and interpretation of field data. 3.3 Collection of meteorology data in the sub-catchments and a control catchment.

3.4 Monthly and quarterly monitoring of surface water and groundwater levels and flows and meteorological/micro-climate data.

4.1 Calculation of water balances 14 Monitoring Data Interpretation 4. Interpretation of Data from collated water level, flow, Interpretation of field data. meteorological and botanical survey data. 15 Sub-Catchment Water Balance 4.2 Interpretation of water 16 Climate Change Assessment balances – identify trends and/or 19 Increasing Mist as Rainfall for Public relationships between micro- Water Supply climate, vegetative cover and ground conditions. 20 Conclusions and Recommendations 5.1 Collation of all desk based 17 Outline Cloud Forest Restoration 5. Reporting and field data. Plan 5.2 Interpretation of data and 18 Ecosystems Services Assessment desk-based data and reporting of 19 Increasing Mist as Rainfall for Public an outline restoration plan. Water Supply 20 Conclusions and Recommendations

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The project team and program are presented in Appendix A.

2 Saint Helena

2.1 Location

St Helena is volcanic sub-tropical island in the South Atlantic Ocean. It lies 4000km east of Brazil and 1950m west of Namibia at 15056’S 005043’W. The island covers an area of 122km2 (47sq miles). The island’s greatest width between Sugar Loaf Hill and Long Range Point is 11.2km and its greatest length is from South Wet Point to Saddle Point, a distance of 17.4km (Brown, 1981b). The island rises steeply from sea level to a central ridge of peaks that form a rugged and highly eroded volcanic terrain. Habitats zone include semi desert at sea level through to cloud forest at a maximum height of 823m above sea level. A location plan is presented in Figure 1.

2.2 History

The island remained undiscovered until Portuguese Joao da Nova Castella discovered it on St Helena of Constantinople’s day 21st May 1502. He found a stream of fresh water and set out to explore the island. He described no inhabitants, but sea-birds, sea-lions, seals and turtles were plentiful. No other animals are said to be found. The interior of the island was covered by dense forest, and even some of the precipices the sea were covered in gumwood trees (Gosse, 1938). The island remained secret for another 80 years but from 1588 to 1633 the island was visited by many European mariners enroute to trade with India. Many of the visitors planted fruits and vegetables or introduced domestic livestock, including the goats that were to come to overrun the island. As described by Cavendish, an Englishman and Captain in 1588:

‘The island is altogether high mountains and steep valleys, and down below in some valleys, marvellous store of all these kinds of fruit before spoke of do grow: there is greater store (of trees) growing in the tops of the mountains than below in the valleys: but it is wonderful laboursome and also dangerous travelling up unto them and down again, by reason of the height and steepness of the hills….There are in this island thousands of goats, which are very wild: you shall see one or two hundred of them together, and sometimes you may behold them a mile long. Some of them are as big as an ass, with a mane like a horse and a beard hanging down to the very ground. They will climb the cliffs which are so steep that a man would think it a thing impossible for any living thing to go there. We took and killed many of them for all their swiftness, for there are thousands of them upon the mountains.’

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Figure 1: St Helena Location Plan

In 1633 the Dutch formally annexed the island but made no attempt to occupy it permanently. Jan Huyghen van Linschoten, a Dutch merchant and historian described the richness of the island and its plentiful supply of water (Gosse, 1938).

‘A very high and hilly country, so that it commonly reacheth unto the clouds. The country itself is very ashy and dry. Also all the trees (whereof there is great store, and grow themselves in the woods) that are therin, are little worth, but only to burn. The water is excellently good, and falleth down from the mountains and so runneth in great abundance by small channels into the sea, where the Portuguese fill their vessels full of water, and wash their clothes.’ In 1634 Peter Mundy ‘praised the lovely woods on the high hills, and described the now extinct ebony tree, the excellent grass, the thickets of tree ferns and the many running streams.’ And yet by 1683 even the East India Company was becoming alarmed at the rate of deforestation. In Gosse’s history of the island it notes that ‘The rainfall of a steep hilly country such as St Helena is dependent to a large extent on the forest which grows on the highest ridges. If this is destroyed, the rainfall, or in any case the humidity of the atmosphere, is lessened, and also, in a country such as St Helena, with a light sandy soil, it is the trees and the roots which prevent the erosion of soil which all the world over has turned rich agricultural land into dry desert. When the trees are destroyed on steep hillsides every heavy rain storm will wash tons of good soil into the sea, leaving only a barren, rock-covered surface.’ The East India Company of the time began to draw up regulations, but these were futile as planters ignored them. The worst offenders were the many small distilleries across the island. Taxes were raised in

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DPLUS051 Project Report response, but these did not curb use, but only fuelled unrest. By 1690 a proliferation of rats and vermin were recorded reducing the island’s productivity and driving the main population to eating yams. In 1802 Colonel Pattern became Governor making provision for the replacement of logged trees. At around this time Lord Valentia visited the island and as an enthusiastic botanist discovered an island more-or-less denuded of trees. He did encounter a diversity of species on the peaks including tree ferns 14 feet tall with 5 foot fronds, Cabbage trees and gumwoods. He observed: ‘The scenery is more like England than anything I have seen in the island, and is much admired by the natives for no reason that had no weight with us; it is more level, and was once covered with gumwood trees, but avenues were opened in it, which gave the South East wind a free entrance, the consequence was its destruction.’

3 Tropical Montane Cloud Forests

The cloudy, wet and generally difficult terrain of the world’s Tropical Montane Cloud Forests (TMCF) has not only made them hydrologically and ecologically unique, but has historically given them some protection compared to other tropical forests. This protection has reduced since the 1970s and in many parts of the world (including St Helena) they have become fragmented. By the early 1990’s TMCF were high on the list of the world’s most threatened terrestrial ecosystems and were being lost at a rate greater than lowland tropical forests (1.1% per year vs 0.8% per year) (Bruijnzeel, Scatena and Hamilton, 2011).

Due to their spatial distribution, the definition of TMCF has been challenging. It is generally accepted that TMCF are now classified based on forest structure, the degree of mossiness and leaf sclerophylly and the percentage of net precipitation that reaches the forest floor. An overarching definition of TCMF is “forests that are frequently covered in cloud or mist” (Bruijnzeel, Scatena and Hamilton, 2011).

TMCF altitude varies from 500mASL to 4000mASL depending upon the local climate which can be affected by distance from the sea and the latitude (from 23°N to 25°S). Typically, there is a relatively small band of altitude in which the atmospheric environment is suitable for cloud forest development. This is characterized by persistent fog at the vegetation level, resulting in the reduction of direct sunlight and evapotranspiration (Lawton et al., 2001).

Bruijnzeel et al.(2012) identified three recognised types of TMCF:

• Lower Montane Cloud Forest - LMCF (tree canopy 15m-33m); • Upper Montane Cloud Forest - UMCF (tree canopy 1.5m-18m); and • Sub-Alpine Cloud Forest - SACF (tree canopy 1.5m-9m).

On small oceanic island mountains, the change from lower to upper montane cloud forest zone may occur at lower altitudes. On large mountains in equatorial regions, the transition between LMCF and UMCF where persistent cloud occurs can be at an elevation between 2000-3000mASL (Bruijnzeel, Scatena and Hamilton, 2011). The maximum elevation of St Helena is 823mASL at Diana’s Peak, however the persistent cloud level starts above 650mASL. Based upon the cloud forest tree survey work of Malan & Darlow, 2018, the canopy height within the cloud forest of St Helena averaged 2.75m.

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The height of persistent cloud level and canopy height indicate that the St Helena cloud forest falls into the UMCF classification. The St Helena cloud forest is not considered sub-alpine, as the average maximum temperature is greater than 10oC with the presence of epiphytes which are usually absent from SACF. Mist covering the Peaks is shown in Plate 1.

Plate 1: Mist over the Peaks National Park

The presence of cloud forest is governed by the persistent cloud conditions, with the lower elevation determined by the moisture content and temperature of the atmosphere, such that the more humid the temperature of uplifted air, the sooner it will condense. As distance increases from the ocean, air tends to be drier and requires lower temperatures and higher elevations to reach condensation point (Bruijnzeel, Scatena and Hamilton, 2011). As a consequence, St Helena has a lower elevation cloud forest due to its proximity to the ocean.

Annual and seasonal rainfall regimes in TMCF can range from 500 to 10,000 mm/year (Hamilton, Juvik and Scatena, 1995). The high moisture content in TMCF promotes the development of a high biomass and biodiversity of epiphytes, particularly bryophytes, lichens, ferns (including filmy ferns), bromeliads and orchids. As a consequence, the number of endemic plants can be very high (Hamilton, Juvik and Scatena, 1995). Trees in TMCF regions are generally shorter with greater stem density. Canopy trees exhibit gnarled trunks and branches, forming dense, compact crowns. Their leaves become smaller, thicker and harder (Hamilton, Juvik and Scatena, 1995). This adaptation to the local microclimate also increases fog interception (wind-driven cloud moisture) where water droplets from the fog (or mist) adhere to leaves, fronds or needles of cloud forest trees, ferns, bryophytes and coalesce into larger

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DPLUS051 Project Report drops, falling to the ground. In some cases, tree crowns and leaf shape can direct the path of water droplet movement towards the centre of the tree crown.

Soils in TMCF are characteristically wet, frequently waterlogged and highly organic due to the presence of humus and peat (Hamilton, Juvik and Scatena, 1995).

Within cloud forests, much of the moisture available to plants arrives in the form of fog drip, where fog condenses on tree leaves and then drips onto the ground below. Water droplet size is an important element of fog water yield and is dependent on the characteristics of the air mass. Fog developing in continental regions have smaller droplets, higher concentrations and a narrow size spectrum whilst marine air fog generally has larger droplets and a wider size spectrum (Mcknight and Juvik, 1975). The most productive fogs (2-3mm/hr), occur in non-raining cloud decks formed in marine air masses (Mcknight and Juvik, 1975).

Local factors affecting the quantity of fog precipitation include canopy height, canopy architecture, wind velocity, foliar surfaces, hillslope orientation and orientation of foliage and branches (Holder, 2006).

The St Helena cloud forest has all the characteristics of a TMCF, with small trees, high biomass and biodiversity, high number of endemic trees, ferns, lichens and bryophytes showing adaptation for mist interception.

4 Climate

4.1 The Island

St Helena enjoys a mild sub-tropical climate due to the South Atlantic Anticyclone (SAA) which controls weather and climate over the central South Atlantic. The resulting wind-stress causes the anticyclonic gyre circulation in the Ocean, the South East Trade Winds, where the Benguela Current conveys relatively cold water from high to low latitudes along Namibian and South African west coasts. The latter continues westward to form the South Equatorial Current (Feistel, Hagen and Grant, 2003).

St Helena's sub-tropical latitude affords it fairly constant temperatures; the average annual temperature range at sea level is 21-28oC, this reduces by about 1.3 degrees every 100 m rise in elevation. Rainfall is often extremely localised, creating desert-like conditions of the outer part of the island where 175mm of rain falls per year, compared to the Peaks where cloud and mist accumulate bringing 290 days of overcast conditions and 1050mm of rain each year (Kew et al., 2017). Mean monthly temperatures since 1893 have rarely been below 15 °C or above 22 °C (iMC Worldwide, 2014).

The island has a single long-term manned weather station at Bottom Woods, which is operated by the UK Meteorological Office using local staff. The Bottom Woods Station is the only weather station on St Helena which reports to international data sets. Data from the weather station is commonly listed as St Helena Island, with records from 1892 to the present. However, it should be noted that the weather station at Bottoms Woods started operations in 1976, replacing the weather station at Hutts Gate. The weather station re-located from Hutts Gate in the centre of the island (620mASL) in 1976, to a lower elevation site on the drier western part of the island near Horse Point (436mASL). Other than one missing month in 1892, the islands long term climate record appears complete. Table 2 and

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Figure 2 summarise the long-term average rainfall and temperature record for the island.

Table 2: Saint Helena Long Term Average Rainfall and Temperature (1892 to 2014)

Month Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Dec Rainfall (mm) 33.8 49.4 64.2 49.5 49.4 58.7 60.5 50.1 36.3 24.9 18.3 22.6 Temperature (oC) 19.5 20.6 20.8 20.2 19.0 17.5 16.3 15.7 15.8 16.1 16.9 18.1

Figure 2: Saint Helena Long Term Average Rainfall and Temperature (1892 to 2014)

Long Term Average Annual Rainfall and Temperature 1892 to 2014 Source: German Weather Service (DWD) 70.0 25.0 C) o 60.0 20.0 50.0

40.0 15.0

30.0 10.0 20.0 5.0 Long Term Rainfall Long Term (mm) 10.0

0.0 0.0

Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Dec ( Average Long Term Temperature Month

Rainfall (mm) Temperature (oC)

Based on the long-term climate data presented in

Figure 2, the island has two distinct wet seasons centring on March and July. November is the driest month of the year. August and September are the coolest months with February and March the warmest. In general, humidity varies little, being in the mid-sixties (percent) in the warmer months and in the low to mid-seventies (percent) for the rest of the year (SAERI et al., 2016). Mean annual rainfall has been shown to increase with elevation across the island, with rainfall at altitudes greater than 656mASL being 61% greater than rainfall between sea level and 328mASL (Sir William Halcrow and Partners, 1969).

The long-term rainfall for Bottom Woods MET Station, located to the west of the island is presented in Figure 3 for the 40-year rainfall record between 1977 and 2017.

Average annual rainfall at Bottom Woods MET Station for the 40-year record is 485mm.The driest year was in 1984 (303mm) and the wettest in 2008 (735mm).

Figure 3: Bottom Woods MET Station Rainfall

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The Agricultural and Natural Resource Directorate (ANRD) of Saint Helena Government monitor all of the outlying climate stations across the island. ANRD currently record rainfall at 20 locations across the island (include data provided by Bottom Woods Met Station). The distribution of weather stations across the island is presented in Figure 4. Isohyets of the island’s rainfall are presented in Figure 5, using long term mean data collected by the Bottom Woods MET Office and ANRD over a 31-year period between 1986 and 2017.

4.2 Drought

In recent years the island has experienced several droughts, most notably in 2013 and 2016. The most recent drought of 2016 occurred during the first year of data collection for this project. As a consequence, the climate data collected may not be representative of the long-term average, should a longer-term data set be collected within the study area. However, the data do provide an opportunity to investigate water resource availability during a period of water scarcity.

A selection of press releases from SHG Resilience Forum between October 2016 and March 2017 are presented in Appendix B as a record of the 2016 to 2017 drought. During the drought, reservoir levels dropped to 9.3% of total capacity in November 2016, before the drought order was lifted on 27th February 2017 when reservoir levels increased above the 50% threshold for lifting the order (recorded as 62% of total capacity).

February 2017 was an exceptionally wet month with the MET Station and Bottom Woods recording the highest monthly rainfall at the weather station since February 2011 (115.2mm). This rainfall was the sixth highest monthly rainfall recorded in the island’s history and the third highest rainfall recorded during February. The drought and high rainfall in February 2017 are discussed in more detail in Section 14.8).

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Figure 4: St Helena's Weather Stations

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Figure 5: St Helena Long Term Mean Rainfall Isohyets

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4.3 Evaporation

Evaporation data from Bottom Woods MET Station collected between October 2016 and April 2018 are presented in Figure 6. Evaporation is measured using an open pan lysimeter, located within the grounds of the weather station.

Figure 6: Bottom Woods MET Station Monthly Evaporation 2016 to 2018

The data set indicates that at the Bottom Woods MET Station, rates of evaporation average 2.4 times higher than rainfall, resulting in a net rainfall deficit. The weather station is located in the drier north east of the island at an elevation of 436mASL. The highest rate of evaporation was 9.1mm, recorded on the 25th March 2018.

4.4 Potential Evapotranspiration (PE)

PE is defined as the amount of water used by a freely transpiring short grass crop (Mathieson, 1988), and is an important element of a catchment water balance. The measurement of PE is more complex than measuring losses from open water as plant transpiration must be considered alongside water availability and the ability of the atmosphere to absorb and carry away the water vapour (Shaw et al.,

2011). To establish Evapotranspiration loss (Et) in a catchment area draining to a gauging station on a river, is included in the water balance equation as:

! − #$ − % − & ± ∆) where P is precipitation, Q river discharge, G discharge of groundwater across basin divides and DS change in storage (Shaw et al., 2011).

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Evapotranspiration is technically difficult and expensive to measure, an alternative method is to calculate PE using the Penman-Monteith equation (Section 14.7), from weather data and treat a complex vegetated surface as a “big leaf”, which allows the separation of the soil-plant resistance and the plant to atmosphere resistance.

Potential evapotranspiration (PE) here calculated using the Penman formula for Jamestown and Hutts Gate (Sir William Halcrow and Partners, 1969). Using a reflection co-efficient of 0.2, the mean annual PE was calculated at 1880mm and 810mm at Jamestown and Hutts Gate respectively. The PE for Jamestown amounted to 860% of the mean annual rainfall. For Hutts Gate, PE was 95% of mean annual rainfall. High rates of evaporation were reported to occur between December and February, during the hottest months of the summer.

Mathieson (1988) dismissed the Halcrow PE data as suspect but published a table of PE data was published for Bottom Woods MET Station and Hutts Gate. The average PE for Bottom Woods was recorded as 1312mm for a 10-year record between 1978 and 1988 (Figure 7). The average PE at Hutts Gate was recorded as 862mm for a 22-year record between 1953 and 1975 (Mathieson, 1988) (Figure 8). PE reported by Mathieson was 6% greater than calculated by Sir William Halcrow and Partners.

Figure 7: Bottom Woods PE (1978 to 1988)

Annual Potential Evapotranspiration (1978 to 1988) Bottom Woods Weather Station, St Helena Mathieson, 1998 1500

1400

1300

1200

1100

Potential Evapotranspiration (mm) Evapotranspiration Potential 1000

900

800 1976 1978 1980 1982 1984 1986 1988 1990 Year

Annual PE (mm)

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Figure 8: Hutts Gate PE (1971 to 1975)

Annual Potential Evapotranspiration (1971 to 1975) Hutts Gate, St Helena (Mathieson, 1998) 960

940

920

900

880

860

840 Potential Evapotranspiration (mm) Evapotranspiration Potential

820

800

780 1971 1972 1973 1974 1975 Year

Annual PE (mm)

4.5 St Helena’s Cloud Forest

There is little historic data regarding the climate of St Helena’s cloud forest. The closest unmanned weather station is located at Hutts Gate (620mASL), which was the islands principal weather station until 1977 when the UK MET Office relocated the weather station to Bottom Woods in 1977. A rain gauge at the Hutts Gate Water Treatment works is now monitored by ANRD. Rainfall has been recorded at Hutts Gate since July 1925. A summary of the Hutts Gate rainfall record is presented in Figure 9 using data from (Brown, 1982), (Henry, 1974a), and (Green and Leo, 2018).

A long-term rainfall record for the Peaks National Conservation Area (Peaks NCA) has been maintained by ANRD and is presented in Figure 10. The 31-year rainfall record started in 1986 and comprises five locations, of which the longest record is associated with Hutts Gate. A 21-year rainfall record (1990 to 2011) was kept for Leggs Gut located between the Peaks Nursery and Wells Gut. The records for Taylors, the Peaks Nursery and Grapevine have only been kept for 1 to 2 years.

Maximum recorded annual rainfall was 1709mm in 2008 (Hutts Gate), with the driest year recorded in 2001 at Hutts Gate (148mm). Average annual rainfall at Hutts Gate is 1,021mm. Average long-term rainfall at Leggs Gut was 87% of the average rainfall recorded at Hutts Gate and is located approximately 950m south of the Hutts Gate water treatment works.

The rain gauge at the Peaks Nursery was installed in June 2015. The data record is too short to evaluate long term trends but has been used in later sections of this report when evaluating the project rainfall data collected within Perkins Gut, Wells Gut and Grapevine Gut.

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Figure 9: Hutts Gate Rainfall Record 1926 to 2017

Figure 10: Peaks National Conservation Area Rainfall Record

Peaks NCA Rainfall Record 1986 to 2017 1800 1600 1400 1200 1000 800

Rainfall (mm) 600 400 200 0 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 Year

Hutts Gate Leggs Gut Taylors Grapevine Gut Peaks Nursery

The rainfall record for the Peaks Nursery rain gauge between 2016 and 2017 is presented in Figure 11, alongside the long-term average rainfall for Hutts Gate rain gauge (1926 to 2016). The rain gauges are located 960m apart, with an elevation difference of 95m.

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Figure 11: Hutts Gate and Peaks Nursery Rainfall

The Peaks Nursery recorded 252 rain days in 2016 and 176 rain days in 2017.

Two automatic weather stations were installed in the Peaks at Black Gate and Taylors (Grapevine Gut) in 1997 as part of the Saint Helena Catchment Management Study (Gunston and Rosier, 2002). The weather stations did not perform as expected, so data from Hutts Gate was used for interpreting the studies soil moisture data, however the limited duration temperature, wind speed and rainfall data was reported for the period between September 1997 and October 1999. The range in average hourly temperature at Taylors was 14oC in the Peaks (10.5oC to 24.2oC), with a mean temperature of 15.5oC. Average daily wind speed at Taylors was 2.48m/s, with a maximum hourly wind speed of 8.5m/s.

5 Mist Capture and Rainfall Harvesting

The precise meaning of the words “fog” and “mist” cannot be easily separated, although there is a meteorological difference based upon visibility (Gunston and Rosier, 2002). If visibility is less than 1000m, then it is called fog. Where visibility is greater than 1000m then we call it mist (METOffice, 2017). Mist is generally favoured on St Helena however water captured from fogs and mists is often called fog water (Gunston and Rosier, 2002). For the purposes of this report, we will refer to mist in deference to fog.

5.1 Mist Collection Instrumentation

Mist collectors have less than 100% efficient collection due to fractional sampling of the air passing the gauge or by flow distortion around the gauge. As a consequence, mist during rain free periods can

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DPLUS051 Project Report be underestimated, especially for short intermittent events (Frumau, Tobón and Bruijnzeel, 2006). There are 3 main types of mist collectors (Plate 2):

• Wire harp; • Juvik-type; and • Daube-type.

The wire harp comprises 2500cm2 cross-sectional area using 0.8mm diameter nylon strings spaced 2mm apart. The design of the collector cannot prevent the capture of horizontal precipitation as well as mist and can overestimate mist.

The Daube-type tunnel gauge separates horizontal precipitation into wind driven rain and mist and rotates to align itself to the wind.

The Juvik-type fog mist collector is the oldest design and consists of a louvered cylindrical aluminium screen of 40.5cm height and 540cm2 cross-section. These collectors catch all mist and rain falling at an angle, although some are equipped with a cap to prevent vertical rain from entering the gauge.

Plate 2: Mist Collectors

Source: (Frumau, Tobón and Bruijnzeel, 2006) Figure II.7, Passive Fog Gauges. Left to right: Daube tunnel gauge, wire harp and modified Juvik-type

Hansen & Juvik, 2010 evaluated the performance of a Louvered Screen Fog Gauge (LSFG) as a proxy for canopy throughfall in a Hawaiian montane cloud forest. They concluded that an open-site LSFG provided the best measurement of tree canopy throughfall, confirming the findings of (Frumau, Tobón and Bruijnzeel, 2006) who tested the performance of various designs of wire harp, louvered gauge and tunnel gauge mist collectors. K. F. A. Frumau et al., 2010 conducted an assessment of for gauges (mist collectors) in a windward cloud forest in northern Costa Rica. The assessment concluded that a modified Juvik-type fog gauge had an efficiency close to 100%, independent of wind speed and direction.

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5.2 DPLUS051 Instrumentation

For the purposes of the DPLUS051 mist collection, a hybrid Juvik-type wire harp collector provided by CEH was used, which had been previously used by CEH in the UK. The CEH mist collector design follows the principal of a Juvik-type mist collector, which includes an integrated cap to prevent vertical rain from entering the gauge. The mist collector is cylindrical with a cone shaped bottom section and is 38cm tall and 21cm wide at the top, tapering to a cone which starts 30cm from the top of the collector and tapers to a point 3.5cm in diameter at the bottom (Plate 3).

Plate 3: CEH Hybrid Mist Collector

The mist collector provides a 3,566cm2 surface area for mist collection covered with 187 strands of 0.8mm diameter fishing wire in 47.5cm lengths (89m of fishing line). Mist collects on the fishing wire and under gravity, collects in a Hobo RG3 tipping bucket rain gauge data located below the mist collector. The design does not prevent horizontal rain being included in the measured mist, however the cap prevents vertical rain from entering the rain gauge. The mist collector was oriented with the open side of the rain gauge box facing away from the prevailing wind direction. It is accepted that mist collectors are very different in design from a natural tree canopy and understory and could be under reporting mist collected within the Peaks NCA by the natural vegetation.

Key considerations when using wire harp type mist collectors are the potential for high wind speeds to blow water droplets off wires due to wind drag and vibration of the strands. The interception of horizontal rain alongside fog can also provide misleading results. Lower wind speeds are also known to improve the collection efficiency of a wire harp mist collector. When comparing fog gauge designs,

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(Frumau et al., 2010) recorded fog collection efficiencies of between 20% and 60% of the modified Juvik-type, when using a wire harp design fog collector in increasing wind speeds.

5.3 Mist Capture on St Helena

The first documented reference made of mist capture/rainfall harvesting on St Helena was by Mathieson in 1990 in an End of Tour Report (Mathieson, 1990). In the report, Mathieson emphasised the importance of studying the effects of mist interception on stream flow at Grapevine Gut. The Institute of Hydrology completed a hydrological catchment consultancy for St Helena in 1997 to design a water balance model, quantify cloud water contribution to water balances and recommend land use and vegetation to improve water resource management (Gunston and Rosier, 1997). The report referenced two fog catchers that were installed at Taylors/Grapevine Gut (just below Cuckolds Point) and at Hutts Gate. The catchment consultancy final report (Gunston and Rosier, 2002) made reference to a 1992 Grapevine Gut pilot mist interception research programme, however the report is now lost and could not be consulted for this study. Presumably the pilot programme was instigated by recommendations made by Mathieson in 1990.

The amount of water captured from fogs or mists by vegetation and artificial collectors depend on a number of factors which can include:

• Wetness of the mist; • Speed at which the mist is moving (related to the measured wind speed); • Physical nature of the obstruction (vegetation or fog collectors); and • The land area of vegetation and surface ware of collectors which contribute to capturing of mist water (Gunston and Rosier, 2002).

Mathieson (1992) described the mist collector that remains at Hutts Gate being installed in 1989 and comprising a rectangle of metal gauze (83.5cm x 91.7cm) placed in a frame of angle iron. The square was placed in a diamond shape on legs over a normal 125mm diameter rain gauge and oriented to face the prevailing wind (Gunston and Rosier, 2002). The mist collector is still located at Hutts Gate Water Treatment Works but is no longer operational (Plate 4). It is very similar in design to the wire harp fog collector described in Section 5.1.

Mist data has been collected at Hutts Gate treatment works between 1990 and 2017. The mist record between 1990 and 2017 is presented in Figure 12. CEH and Mathieson have doubted the effectiveness of the mist collector and accuracy of the datasets as there was little difference between the mist intercepted for major and minor rainfall events and no mist was recorded on days when there was zero rainfall.

The mist record for Hutts gate highlights the concerns that Mathieson made in 1992. Figure 12 shows mist and rainfall for Hutts Gate, with rainfall for Leggs Gut provided as a cloud forest data set. The mist data start to tail off from 2007 and are less than recorded rainfall from 2010. The ratio of mist to rainfall is also low and averages 2:1 mist to rainfall. The Hutts Gate and Leggs Gut rainfall show a similar trend, save for Hutts Gate rainfall recorded in the year 2000 (148mm) which is uncharacteristically low. The data do not represent trends in earlier and later data for 2000. Correspondence with ANRD confirm that data is not being regularly or accurately at Hutts Gate and the data should be treated with caution.

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Plate 4: Hutts Gate Mist Collector

Figure 12: Hutts Gate Mist Capture

Hutts Gate Annual Mist (mm) 1990 to 2017 3000

2500

2000

1500 Mist (mm)

1000

500

0 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Year

Hutts Gate Mist (mm) Hutts Gate Rainfall (mm) Leggs Gut Rainfall (mm)

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6 Geology

6.1 Island Geology

St Helena is located approximately 240km east of a hot spot in the earth’s mantle and 500km east of the Mid-Atlantic Ridge, where new ocean floor is being created leading to gradual movement of the African plate to the east and the South American plate to the west. St Helena is located on the African plate which is moving eastwards at a rate of about 28mm per year (Ashmole, 2000).

A detailed summary of the islands geology from investigations completed by Baker (1967), Oliver (1869) and Mellis (1875) is presented in Sir William Halcrow and Partners, (1969). The island was formed from the coalescence of two basaltic shield volcanoes erupting approximately 15 million years ago, rising from a depth of approximately 4.24km below sea level to 823m above sea level. Olivine rich Basalt comprises the majority of the island’s geology, appearing as lava flows interbedded with volcanic ash and tuff. Trachy-basalts, trachy-andesites, phonoilites and basal breccias are also present. Baker identified a single block of limestone on the southern side of the Barn. Later volcanic intrusions formed dyke swarms. Ashmole & Ashmole (2000) considered that the age of the island and the speed of movement of the African plate indicated that St Helena would have been over the hot spot (located west of the island) approximately 13 million years ago.

The lower lying coastal areas consist of hard basalt lava beds, topped by scoriaceous and permeable layers of lava. Harder basalts are in places interbedded with softer, porous, pyroclastic tuffs. Inland, much of the surface material comprises friable, dark red to coffee coloured soil. The soil has been formed from weathered basaltic material containing clay minerals caused by very severe local hydrothermal activity (Baker, 1967). This highly weathered clay (described as laterite in some reports) can be seen in outcrop, including the “Paint Box” at Bottom Woods.

The active volcanic phase in the development of St Helena continued for approximately 7 million years, followed by a similar period of inactivity (Ashmole, 2000).

Extensive erosion has taken place across the island and is particularly severe on the eastern side in the Sandy Bay area where lava flows from the two main volcanic eruptions overlapped (Sandy Bay Complex). The erosion has formed a deep depression or bowl, which was partially infilled by lava flows from a third minor volcanic eruption which created smaller eroded valleys on the flanks of the older volcanoes.

The presence of softer beds of tuffs interbedded in flows of harder basalt has resulted in backward erosion of the stream beds to produce steep waterfalls, such as the Heart Shaped Waterfall above Jamestown. All of the stream valleys are steep sided, flaring and canyon-like, reaching depths of 300 metres or more. Nearly all of the principal valleys have been truncated by the inwardly marching sea- cliffs and are now mouthing at the summits of cliffs 100 to 200 meters above sea-level (Daly, 1922).

A summary of the island’s geology is presented in Figure 13.

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Figure 13: Geology of St Helena

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6.2 Geology of the Study Area

An investigation of the central Peaks geology has never been completed, or if it has, no documentation remains.

Ian Baker returned to St Helena in 2003/2004 on a walking trip and based on these walks, wrote a companion guide to the islands geology for visitors and walkers in 2010 (Baker & Thorpe, 2010). Ian Baker describes the DPLUS051 study area being located within the south-west volcano, where volcanic activity started 10 to 11 million years ago.

The lowers rocks comprise pyroclastic material and lava flows (Lower Shield), underlying sequences of lava flows (Main Shield) which starts approximately 1,500 feet above sea level. The lava flows are heavy, almost black and rich in crystals of augite and olivine. All of the rocks in the Lower and Main Shields are cut by light coloured masses (dykes and parasitic intrusions) of phonolite and trachyte, dating around 7.5 million years ago (Baker & Thorpe, 2010).

The rim of the Sandy Bay Complex (also known as the Central Ridge) includes Diana’s Peak, Mount Actaeon, High Peak, Hooper’s Ridge and White Hill. The weak basaltic rocks and bedded lavas have been highly eroded to form a broad amphitheatre valley, drained by several streams flowing into Sandy Bay (Daly, 1922).

The geology of the Peaks is mainly hidden beneath the dense tree canopy, its understorey and the peaty soil beneath. There is very little outcrop of lava and pyroclastic material to indicate the geological sequence within the study area, except for occasional exposed rock faces along the central ridge between Mount Actaeon and Cuckhold’s Point. An example of such an exposed rock face is the trachyte dyke found along the road between Mount Actaeon and Diana’s Peak shown in Plate 5.

Plate 5: Trachyte Dyke on the Central Peaks Road

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The geology map in Figure 13 indicates that the study is underlain by the Main Shield lava flows, trachyandesite and Upper Shield lava flows. The origin of this Upper Shield designation is unknown.

7 Soil

7.1 St Helena’s Soil

A detailed soil survey has not been completed for the island, however (Sir William Halcrow and Partners, 1969) reported that over thirty soil samples from across the island had been examined by Rothamsted Experimental Station. Soils were noted for their high acidity and potassium content. Some soils in the Longwood area of the island were reported to have a high content of soluble salts, with chloride being the most abundant.

The Halcrow report described soil behaviour as a heavy clay when wet, which is extremely difficult to work. When it dries rapidly, the soils form a hard baked crust. In general, soils were reported to have a low organic content and poor water retention properties.

The Ministry of Overseas Development commissioned a report on the management of St Helena's forestry. The report included an evaluation of the islands soils, geology, climate and water resources (Henry, 1974b). The report described additional soil samples taken within the vicinity of Longwood Farm, from a range of sites including some under forest cover. Trace element concentrations were reported as “average” with some samples reporting high or very high soluble sodium concentrations. pH was reported as fairly low in soils analysed.

A map of St Helena’s soils is presented in Figure 14, which originated from Land Survey Report 32 (Brown, 1981a) and (Brown, 1981b). The map indicates that the study area soils comprise Humic Cambisol, Dystric Histosol and Dystric Cambisol.

7.2 Soils in the Study Area

The inspiration for the DPLUS051 study was a Peaks catchment management study completed between 1997 and 2001 by the Institute of Hydrology (also known as the Centre for Ecology and Hydrology). The study was born out of the St Helena Water Plan 1990 to 2010, which recommended a research programme to investigate whether re-afforestation of the Peaks area would boost flow from springs by increasing the interception of water from mists by trees (Rosier, 2001).

The study was shortened to a 12-month assessment of soil moisture, rainfall and climate (including mist – Section 5.3) in the Peaks area due to delays in funding and logistical problems. The design of the climate and soil monitoring programme was completed during an earlier site visit in 1997 (Gunston and Rosier, 1997). Soil moisture was measured in five different land use types using a neutron probe and comprised:

• Permanent pasture at Black Gate; • Unmanaged Flax at Black Gate; • Cleared conservation are in Taylors (Grapevine Gut), comprising ferns, grass and herbs; • Pine plantation at Stitches Ridge; and • Tree fern thicket below Cuckholds Point.

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Figure 14: Soil Map of St Helena

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Several semi-permanent aluminium access tubes were installed at a range of depths (1.6m to 3.5m below ground level) in each land use type for the measurement of soil moisture using the neutron probe. Some of the aluminium tubes can still be found in the Peaks. An access tube used to measure soil moisture in an area of unmanaged flax is shown in Plate 6 and is located along a footpath behind the EMD Peaks Nursery.

Plate 6: Neutron probe aluminium access tube

Data was collected between 1998 and 2002 by staff from ANRD on behalf of CEH. The study concluded that soil moisture is less depleted under the tree fern thicket, planted endemics and controlled natural vegetation than under other vegetation types, including flax. The data implied that more water is available to drain below the soil profiles in wet periods to recharge groundwater and increase stream flow (Gunston and Rosier, 2002). Soil moisture measurement for a site at Black Gate which had been cleared of flax was reported to have a wetter soil profile after clearance.

The study had also installed automated weather stations at Black Gate and Taylors, but did not perform as well as expected. Daily rainfall from Hutts Gate was used for the analysis of soil moisture data.

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8 The Ecology of St Helena

8.1 Historic Accounts

The earliest accounts of the island ecology were made by the Portuguese, after Commodore Joao da Nova Castella on 21st May 1502 and are described in Section 2.2 Mellis (1875) recorded that there were 1,048 species of plants on the island, of which 77 were endemics (Henry, 1974b).

Colonisation of the island by microbes, plants and animals started as soon as the island emerged from the sea. Marine animals and seabirds would have visited the island almost immediately, however the first living organisms to colonise the land may have been bacteria capable of using hydrogen sulphide as a source of energy. The endemic flowering plants (i.e. those found nowhere else) are probably derived from about 25 colonising stocks. There are also a few non-endemic species that seem to be indigenous (native) to St Helena, but which also occur elsewhere (Ashmole, 2000).

The introduction of goats and pigs (and some cattle) to the island by mariners account for a significant amount of ecological destruction of St Helena. The animals were “harvested” by ships crews to supplement the ships food stocks. Subsequently, human settlement of the island contributed to the decline of the island’s biodiversity through the clearing of land for grazing, timber and firewood. By the middle of the 20th Century, almost all of the islands natural vegetation had retreated to the island’s highest ridges and cliffs.

Despite this long-term destruction of the island’s biodiversity, St Helena is home to over 612 endemic species (mostly invertebrates) which comprise almost a third of the endemic species in the UK Overseas Territories. However, the introduction of invasive mammals and plants has drastically changed the islands flora and led to the extinction of many species, particularly plants and animals (SAERI et al., 2016). The last documented extinction of a plant species was the Saint Helena olive tree in November 2003 (RSPB et al., 2014).

The most recent “stock take” of St Helena’s endemic and native species was completed in 2014 by the RSPB. The survey recorded 2,932 species recorded, of which 2,144 were native and 502 were known endemic species (RSPB et al., 2014). Since the survey the number of endemic species has increased due to work carried out during the completion of Darwin Plus projects Securing the future for St Helena’s endemic invertebrates, Mapping St Helena's marine biodiversity to create a Marine Management Plan and Laying the foundations for invertebrate conservation on St Helena. The island currently supports up to 1/3 of the total UK mainland and Overseas Territory endemic biodiversity.

8.2 The Cloud Forest

The cloud forest would have occupied much of the higher slopes across the island. However, the only areas of cloud forest left are at the two highest points on the island containing around 311 endemic species of plant and invertebrate (SAERI et al., 2016). The cloud forest is the only remaining densely vegetated habitat type on St Helena which can be considered predominantly native. Less than 40ha of this ecosystem remains on less than 0.3% of the total land area (Lambdon and Darlow, 2012). The cloud forest is confined to the island’s highest ridges, generally over 750m in altitude. Requiring high levels of precipitation and being resilient to the cool, windy conditions, the cloud forest was never extensive, but would have extended down to Halley’s Mount and Osbourne’s. It would have then been

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DPLUS051 Project Report continuous around the great crescent of the Central Ridge (Section 6.2), but the remaining fragments are now confined to Diana’s Peak National Park and High Peak (Lambdon and Darlow, 2012).

The cloud forest is dominated by tree fern thicket: a rich community, home to many of the island’s rarest endemics. Ferns, mosses and liverworts form a dense undergrowth and also hang from the damp branches. The trees are principally members of the family Asteraceae, comprising the Black Cabbage Tree, Whitewood and He Cabbage tree with a handful of the more shrubby False Gumwood remaining on exposed western rock outcrops (Lambdon and Darlow, 2012).

The tree fern canopy (Error! Reference source not found.) is now rare but is dark and layered with t hick musty litter. Little grows directly below it, but a vibrant understorey develops on the clearings. Many non-natives have penetrated the dense vegetation posing serious management issues. Whiteweed, Fuchsia and Cow Grass are amongst the most conspicuous. New Zealand Flax is another major feature of the uplands, with extensive abandoned flax-fields blanketing the steepest faces of the Central Ridge (Error! Reference source not found.),

Plate 7: Tree Fern Thicket Central Ridge

leaving a thin veneer of cloud forest at its summit. Flax grows slowly and almost no weeds can compete with it (Lambdon and Darlow, 2012).

8.3 Cloud Forest Vegetation and Plant Species

The cloud forest, which would originally have occupied most of the highest ridges on the island, still persists but is restricted to a small area of the central ridge and a relict fragment further west, at High Peak. The community contains a moderately diverse variety of endemic species. These include four

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DPLUS051 Project Report species of cabbage trees (all Astereaceae) and formerly, the now extinct stringwood Acalypha rubra (Euphorbiaceae) and St. Helena olive Nesotea eliptica (Rhamnaceae). The most exposed areas are dominated by the endemic St. Helena Tree Fern Dicksonia arborescens (Dicksoniaceae). A rich understory is also present, composed of herbs such as the lobelia Trimeris scaeivifolia and large bellflower Wahlenbergia linifolia (both Campanulaceae) together with circa 15 species of native and endemic ferns (Kew et al., 2017). A list of species names referenced in the report can be found in Appendix C.

Plate 8: Flax Blanketing Steep Faces of the Central Ridge Towards Halley’s Mount

Lourens Malan (EMD) and Andrew Darlow (Independent) recently completed Darwin Plus project DPLUS029 ‘Securing St Helena’s rare cloud forest trees and associated invertebrates’. As part of a survey of sites holding the remnant wild populations of four St Helenian endemic tree species within the DPLUS051 study area, where the project team undertook a visual survey of the plant community surrounding each tree. This provided a snapshot of baseline cloud forest condition to show the distribution of species across our study area. An assessment of each species abundance was calculated alongside a species list. The most widely distributed flowering plant and fern species across the study were:

1. Tree Fern*; 10. Bramble; 2. Brown Scale Fern*; 11. Creeping Fuscia; 3. Black Cabbage*; 12. Filmy Fern*; 4. Hen and Chick’s Fern; 13. Dogwood; and 5. Diana’s Peak Grass*; 14. Bilberry. 6. Whiteweed; 7. Black Scale Fern*; 8. New Zealand Flax; 9. Laysback Fern*;

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Endemic species (*) dominate the list, however the remainder of the species are considered invasive and grow aggressively in the cloud forest. The most abundant plant species listed were present at over half of the total surveyed sites (Malan and Darlow, 2018).

8.4 Invasive Species

As discussed, the cloud forest is dominated by invasive plant species, notably New Zealand Flax, Whiteweed, Bramble, Dogwood and Bilberry. Philip and Myrtle Ashmole have written the most comprehensive history of introduced plant species to the island. The following summary is taken from their book, St Helena and Ascension Island: a natural history (Ashmole, 2000).

The introduction of alien plants to St Helena started soon after the discovery of the island, with tree seed imported as early as 1714. Victorian botanist Joseph Hooker was one of the first naturalists to document the significance of introduced plant species to the island, commenting that:

“by far the greater part of the vegetation that exists, whether herbs, shrubs, or trees, consists of introduced European, American, African and Australian plants.”

Hooker suggested that many of these plants were overrunning the island. Scotch fir, Spruce fir and oaks were planted in the 1740’s, with Stone pine in 1758. Maritime Pine followed in 1787. By the early 1800’s Cape Yew, Wattles and Eucalyptus were brought to the island. Many of the imported trees were planted with a particular task in mind such as timber for construction. Yams were imported for animal feed and human consumption. Some of the introduced species quickly spread out of control, such as Elderberry, Buddleia B. madagascariensis, White Flower, Furze and Common Blackberry.

By far the most damaging to the island’s ecology was the introduction of New Zealand flax Phormium tenax. It was introduced in the first half of the 19th Century and was already growing wild by December 1852, when Mr Fred Moss wrote to the St. Helena Advocate suggesting that it could be developed into an industry. The first flax mill operated from Jamestown in 1874 and by the early 1920’s, five private fibre mills were operating on the island and a decade later nine were operating. A rope and twine factory was established and the industry directly employed over 300 people on the island. The flax industry collapsed twice. The first due to a drastic price in fibre in 1932, when almost all the mills closed. The second was precipitated after the Second World War where the industry was supported by government subsidies and finally collapsed in the mid 1960’s when the introduction of synthetic fibres severely depressed the international natural fibre market. The final mills closed in 1966.

During the rise of the flax industry, no attention was paid to the conservation of native plant species and flax grew across the island and into areas below the Central Ridge where fragments of Cabbage tree woodland and tree fern thicket survived. Only the most precipitous slopes remained unplanted, mainly on the south easterly Sand Bay side of the central ridge.

Invasive species are a key management issue in the cloud forest. Through DPLUS029, the EMD Peaks Conservation team have successfully developed new techniques to clear invasive species, propagate endemic species and plant cleared areas. An essential part of this process is to limit the potential for soil loss once Flax and Whiteweed are removed, whilst maximising the chances of newly planted areas to outcompete the surrounding invasive species. This has been achieved with much success using a “pocket planting” technique where small areas (5m x 5m) are cleared of invasive species. These are re-planted with endemic species and intensively managed for 12 months to ensure the endemic

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DPLUS051 Project Report species take hold and form a dense understorey, preventing the re-colonisation of invasive species. It is a time consuming process, but far more successful than clearing large areas of land and replanting over time (risking large scare slope instability and soil loss and re-population of the land by invasive species).

9 Water Resources

9.1 Hydrology

Due to the highly weathered nature of the island’s topography, surface water catchments are delineated by the high ridges in the centre of the island. There are 20 main valleys which have a number of tributary valleys in their systems. In most cases the valleys are narrow and steep sided. Steep waterfalls are a feature in some of the valleys, corresponding with areas of harder basalt (Henry, 1974b). The largest catchments were reported by Sir William Halcrow and Partners, 1969 and are summarised in Table 3.

Table 3: St Helena Catchment Areas*

Catchment Catchment Area (km2)

Sandy Bay 14.00

Fishers Valley 10.02

Ruperts Valley 8.25

James Bay 7.83

Lemon Valley 6.29

Sharks Valley 5.91

*Source: Sir William Halcrow and Partners, 1969

There are no long-term records of continuous stream or spring flow on the island, which is surprising given the reliance of the island on springs and stream flow for potable water supply. Several short term stream and spring flow measurements (spot flow measurements) were reported by (Sir William Halcrow and Partners, 1969) however the data sets are too short and disparate to confidently assess stream and spring flows across the island.

Historic stream flow data was collated and reported in a UK Government Overseas Development Agency report (Brown, 1982), including data reported by Sir William Halcrow and Partners. Discontinuous short flow data for Wells Gut and Byrons Gut for the years 1937, 1944, 1960 and 1969 are presented in Figure 15. The data is provided as evidence of historic flow data within the study area, however the data sets are too short in duration to meaningfully interpret.

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What can be appreciated is the magnitude of flow recorded at the Wells Gut and Byrons Gut intake between 1937 and 1969, indicating that recorded flows are low (7.9 to 42.4 m3/d).

Figure 15: Historic Spring and Stream Flows in Wells and Byrons Gut

Historic Spring and Stream Flow Measurements Wells and Byrons Gut (Brown, 1982)

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40

35

30 /d) 3

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Discharge (m Discharge 20

15

10

5

0 1944 (Halcrow) 1960 (Teale) 1969 (Kopec) 1937 Mar-May (Dennis) 1937 Nov-Dec (Dennis) Spring and Stream Flow Measurements (m3/d)

Wells Spring Wells Upper Spring Wells Lower Spring Wells and Byrons Gut Intake

9.2 Water Distribution Network

Connect Saint Helena abstract spring water and surface water from several locations within the study area as shown in Figure 16. The spring collection points shown at Upper Wells, Lower Wells and Spring /Borehole (Byron’s Gut) are included in the DPLUS051 monitoring network (SW02WG and SW03WG). The Spring/Borehole in Byrons Gut feeds Longwood reservoirs. The catchpit monitored by DPLUS051 in Byrons Gut (SW01G) feeds the header tanks connected to SW02WG. Connect’s spring and stream flow data within the Hutts Gate water distribution network has been reported in Section 9.2.1.

The Hutts Gate treatment works collects water from 8 spring/small stream sources from beneath Diana’s Peak and Mount Actaeon. Flow that is not diverted to the treatment works reaches Willowbank downstream. Stream discharge data from 1981 to 1988 reported an average 125,000 m3 of water available between the high-level springs and Willowbank. The rainfall for 1982 was 52% of the average, with stream flow 258% above average for the period (Ch6, Saint Helena Government, 1989).

Connect monitors raw water volumes from abstraction points at several spring and stream sources at Hutts Gate, Levelwood, Chubbs Springs and Red Hill (Connect Saint Helena, 2018a).

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Figure 16: Hutts Gate Spring Water Collection and Distribution Network

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Pumped raw water volumes are measured from Wells Gut and Grapevine Gut by means of in-line flow meters. Pumped raw water volumes from Grapevine Gut reservoir are reported as part of the Red Hill and Hutts Gate treatment works intake. Pumped raw water from Wells Gut and Leggs Gut are reported as part of the Hutts Gate treatment works raw water intake.

Several surface water monitoring structures are located within Wells Gut and Grapevine Gut but are not used for continuous spring flow, stream flow or water level measurement (see Section 10). All monitoring data provided by Connect is related to pumped spring or stream water, rather than measured flows within streams or spring sources. Consequently, there is no long-term stream or spring flow monitoring data for sources that Connect abstract for potable water supply.

9.2.1 Wells Gut and Grapevine Gut

A summary of pumped raw water flows from 2007 to 2017 for Upper and Lower Wells Gut are presented in Figure 17, Figure 18 and Figure 19 (Connect Saint Helena, 2018a).

Figure 17: Upper Wells Gut Raw Water Flows (2007 to 2017)

Upper Wells Gut Monthly Raw Water Flow (m3) 2007 to 2017 7000

6000 )

3 5000

4000 Raw Water (m Raw Water

3000

2000

1000

0 January February March April May June July August September October November December Month

2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Average

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Figure 18: Lower Wells Gut Monthly Raw Water Flows (2007 to 2017)

Lower Wells Gut Monthly Raw Water Flow (m3) 12000

10000 )

3 8000

6000 Raw Water Flow (m Raw Water

4000

2000

0 January February March April May June July August September October November December Month 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Average

Figure 19: Average Monthly Flows: Upper and Lower Wells Gut (2007 to 2017)

Lower and Upper Wells Gut Average Monthly Raw Water Flows (m3)

8000

7000

6000 ) 3

5000

4000

Average Monthly Flow (m Monthly Average 3000

2000

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0 January February March April May June July August September October November December Month

Lower Wells Gut Average Flows (m3) Upper Wells Gut Average Flows (m3) Combined Average Flows (m3)

Average monthly abstraction from Upper Wells Gut is 1,860m3 and 2,893m3 for Lower Wells Gut. The data collected by Connect indicate that average daily pumped volumes in Lower Wells Gut are a third larger than in Upper Wells Gut. Average monthly pumped volumes in the Wells Gut catchment are 4,752m3 or 1,734Ml per annum. As Upper Wells Gut data is collected upstream of Lower Wells Gut

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DPLUS051 Project Report within the same water course, the data indicate that an additional 1,033m3 per month is available for abstraction in the Wells Gut stream between the monitoring locations. The mechanism for gains in stream flow between the monitoring points are unconfirmed, but may include rainfall runoff, interflow and baseflow.

It should be noted that the method of measuring water flows is via an off-take from the stream. Consequently, the total flow in the Wells Gut stream is not reported by the method of flow measurement.

As discussed in the introduction to Section 9.2, water from Grapevine Gut is pumped from Hutts Gate reservoir to Red Hill and Hutts Gate water treatment works. A summary of combined pumped raw water volumes from 2014 to 2017 for Grapevine Gut are presented in Figure 20.

Figure 20: Grapevine Gut Monthly Pumped Raw Water Flows 2014 to 2017

Grapevine Gut Combined Monthly Pumped Raw (m3) 2014 to 2017 4500

4000

3500 )

3 3000

2500

2000 Pumped Raw Water (m Raw Water Pumped 1500

1000

500

0 January February March April May June July August September October November December Month

2014 2015 2016 2017

The data indicate that average monthly pumped raw water volumes for Grapevine Gut are 347 m3. Pumped volumes were significantly lower during 2016 and 2017 due to the island-wide drought.

9.2.2 Combined Raw Water Abstraction

Figure 21 shows average monthly pumped raw water for Wells Gut and Grapevine Gut between 2014 and 2017. The data indicate that Wells Gut accounts for 86% of the total pumped raw water from the sub-catchments during this period.

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Figure 21: Wells Gut and Grapevine Gut Monthly Pumped Raw Water 2014 to 2017

Wells Gut and Grapevine Gut Average Monthly Pumped Raw Water (m3) 2014 to 2017

3000

2500 ) 3

2000

1500 Pumped Raw Water (m Raw Water Pumped

1000

500

0 January February March April May June July August September October November December Month

Wells Gut (m3) Grapevine Gut (m3)

9.2.3 Annual Treated Water Consumption

Figure 22 shows annual treated water consumption from all of the island’s treatment works (Levelwood, Hutts Gate, Red Hill and Jamestown) between 2009 and 2018. Data collected by Connect indicate that the Hutts Gate Water Treatment Works provides 38% of the islands water on an annual basis. Red Hill Water Treatment Works provides 52% of the islands water, with Grapevine Gut providing approximately 11% of the raw water to the treatment works between 2015 and 2017.

Figure 22: Saint Helena Annual Treated Water Consumption 2009 to 2017

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9.3 Hydrogeology

A comprehensive hydrogeological investigation of the island or study area has never been carried out. However, several reports and investigations make comment about the island’s hydrogeology through interpretation of the island’s geology, climate data and hydrology data.

Several boreholes have been drilled across the island to determine potential yields for potable water supply across the island and to provide construction and operational water for St Helena airport. The most recent hydrogeological investigation (WSP, 2017) was commissioned by Connect Saint Helena to evaluate the potential for deep aquifer groundwater abstraction. The report written by WSP Environmental Ltd, describes unconsolidated gravels in the valleys which, combined with the upper layer of fractured bedrock, form a superficial perched aquifer of limited storage but which are recharged by surface runoff and rainfall. These superficial aquifers are thought to feed many of the islands springs but are susceptible to drought or reduced flow due to periods of low rainfall.

Vesicular and brecciated lava which forms along the contact between two lava flows form aquifers of low storage but are believed to be significant zones of transmissivity. Secondary, fractured, basalt aquifers of low porosity but high permeability exist in areas of faults, dykes and fissures (WSP, 2017).

Layers of weathered material which separates lava flows are relatively permeable, along with soft, weathered tuffaceous deposits (Sir William Halcrow and Partners, 1969). These permeable layers form perched aquifers which can be seen as a secondary source of spring lines across the island.

A hydrogeological conceptual of Saint Helena was developed by Lawrence (1983) and has been reproduced in Figure 23 (WSP, 2017). As well as identifying spring flow, Lawrence describes leakage from overlying tuff to lower layers, increasing the potential for deep groundwater storage.

Figure 23: Hydrogeology Conceptual Model of Saint Helena – Lawrence, 1983

The literature review completed by WSP also evaluated calculated groundwater recharge. Groundwater recharge occurs primarily in the high lying areas in areas above the 500 mASL contour,

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DPLUS051 Project Report where the majority of precipitation falls. Lower areas have low rainfall and high evaporation rates and aquifers situated in these areas are not directly recharged from rainfall. Total recharge figures calculated by previous studies range from 1.5 to 3.6 x 106m3 per annum. When recharge occurring above 500mASL contour is considered, the catchment areas with the largest volume of recharge are the James Valley (259,753 m3) and Lemon Valley (208,094 m3) with all other catchments receiving significantly less recharge per annum. Grapevine Gut and Wells Gut comprise the top of the James Valley catchment. The annual volume of groundwater recharge to catchments above the 500mASL contour is estimated at 1.00 - 1.55 x 106 m3. It is also estimated that 1.0x106 m3 of the recharge is discharged into the ocean by the streams from these catchments as baseflow (Lawrence, 1983).

Test drilling completed by WSP in 2017 completed 10 exploration boreholes to depths between 69mbgl and 132 mbgl in Harper’s, Shark’s Valley, Pleasant Valley, Molly’s Gut, Rosemary Plain, Kinji Field, Plantation and Carson’s Gate. Eight of the boreholes intercepted deep groundwater with yields between 0.3 l/s and 4.3 l/s. Water strikes were reported in weathered material associated with the contact between the Upper Shield/Main Shield.

An assessment of the islands hydrology reported that the islands geology, high and well distributed rainfall and large variations observed in catchment yields suggest that an appreciable volume of water is lost by percolation (Sir William Halcrow and Partners, 1969). The appearance of some exposed beds of scoraceous lava indicated that zones of very high permeability may also be expected below the surface.

Several permanent springs are located within the largest of the island’s catchments. An assessment of the islands springs was reported by Brown, 1981 (Volume 2). In periods of dry weather, spring flows from the eastern valleys (Fishers, Sharks and Deep Valley) and springs from James Valley provide the majority of flow for domestic supply.

Sharks Valley contains the largest perennial flow on the island; estimated at 390-490 m3/d by Dennis during the very dry year of 1973 and 734 m3/d in February 1969 by Halcrow which was also a dry period (Brown, 1981 Volume 2).

Due to the limited data available for the island, the relationship between rainfall recharge, dry weather flow and spring flows cannot be accurately assessed. The Halcrow report (Sir William Halcrow and Partners, 1969) evaluated mean base flow for the islands perennial streams and calculated that base flow may be as high as 8% of annual rainfall at Sharks Valley, with a mean base flow for all perennial streams of 3% annual rainfall. However, due to the complex nature of the islands geology and limited hydrological and hydrogeological data, the contribution of springs and base flow to total stream flow cannot be reported with confidence.

9.4 Water Balance Model

Ian Mathieson completed a two-year tour as Irrigation Advisor to St Helena Government, working within the Department of Agriculture and Forestry. During his time on island, he undertook several tasks to assess the irrigation requirements of the island, including the completion of a Water Plan for St Helena, a hydrology study and evaluation of agro-ecology. His activities were summarised in an end of tour report (Mathieson, 1990).

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Grapevine Gut is a small 22ha steep catchment lying in the wettest part of the island, with over 1000mm rainfall per annum (Mathieson, 1990). Mathieson examined stream flows within the catchment of Grapevine Gut in order to:

1. Monitor stream flow over a 10-year period to observe increases in flow as newly planted forest cover develops. The catchment was predominantly flax, or scrub covered at the time of the report (as it still is today) and it was expected that planting a new forest would increase mist capture in the catchment; 2. Use stream flow and other catchment data to check the water balance model; and 3. Use data to inform decisions on abstraction from the Gut, with a view to pumping water to Hutts Gate.

Mathieson confirmed that studying the effects of mist interception in stream flow had been discussed in the Water Plan and the Agricultural Climate Report and the ability to increase stream flow could be vital for St Helena’s future water security.

At the time of the report, Grapevine Gut had a mixed land use which is summarised in Table 4 and shown in Figure 24.

Table 4: Grapevine Gut Land Use, 1990

Land Use Area (ha) Comment

Flax/scrub 8.5

Cleared flax 6.6 Some young trees.

Scrub 0.2

Flax 5.1

Grass 1.8

Total 22.2

A weir and flow recorder had been installed in the Grapevine Gut catchment and rainfall recording started by the end of Mathieson’s tour in 1990. However, Mathieson was concerned about the planned commitment from the ODA and Forestry section of St Helena Government, as a 10-year data set would be needed. It was strongly recommended that the ODA support the project and provide additional funds for monitoring equipment.

Mathieson’s concerns were well founded, as a 10 year data set was never recorded in the Grapevine Gut catchment and mist data was only collected at Hutts Gate (Section 5.3).

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Figure 24: Grapevine Gut Land Use, Mathieson 1990

Key: CFX (cleared flax), FX (Flax), SC (scrub) and GR (Grass). Ref: Mathieson, 1990.

10 Water Features Survey

During October 2016, the project team completed a walkover of the study area to identify water features (springs, streams, boreholes) and to scout potential monitoring locations.

The project team comprising staff from Connect and Arctium completed a survey of Grapevine Gut, Byrons Gut, Wells Gut and Willow Bank on 12th October 2016. Two catchpits were identified in Grapevine Gut at the bottom of each stream which flow into the Grapevine Gut reservoir (Plate 9 and Plate 10). Three catchpits were identified in Wells Gut (Plate 11, Plate 12 and Plate 14), with the third comprising a catchpit and v-notch weir at the confluence of Byrons Gut and Wells Gut by the Star Road. A spring source and catchpit were also identified in Byrons Gut (Plate 15 and Plate 16). Two water storage tanks take water from the catchpits in Wells Gut and Byrons Gut and pump the water to Hutts Gate Water Treatment Works.

Connect Saint Helena staff informed Arctium that the Byrons Gut spring source supplies potable water to some houses outside of the catchment. The water flowing out at the V-Notch weir on the Star Road is the residual water flowing out of Wells Gut and Byrons Gut.

Outflow at Wells Gut/Byrons Gut V-Notch Weir =

Recharge – water pumped to Hutts Gate WTW – spring water pumped to local houses.

Connect Saint Helena do not have any records concerning the design of the catchpits in both sub- catchments, nor documents describing their precise design use. Connect do have records of the v-

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DPLUS051 Project Report notch weir design but confirmed that the constructed v-notch weir may not have the same dimensions as the design drawings (confirmed during the field investigation). There are no “as-built” drawings for the weir.

Unfortunately, there are no reference geology or hydrogeology investigation reports available for the Peaks NCA and study area. As a consequence, all observations concerning the potential source of surface, near surface and groundwater described in the following sections refer to a general understanding of island-wide soils, geology and hydrogeology.

10.1 Grapevine Gut

10.1.1 Catchpit 1

Catchpit 1 (Plate 9) is located at the bottom of Grapevine Gut and comprises a concrete structure approximately 1.09m wide, with side walls 2.26m long which flare out to encompass all of the stream bed in Grapevine Gut. The stream bed upstream of the catchpit comprises large pebbles and cobbles of bedrock. It is thought that the stream bed in this this lower part of the catchment rests on low permeability lava.

The structure is 0.69m high with a 0.185m Internal Diameter (ID) HDPE outflow pipe located in the downstream concrete wall. Surface water collects in the catchpit and flows into the Grapevine Gut reservoir via the downstream outflow pipe. The base of the structure is concrete.

A stilling well is located on the left-hand side of the structure, which connects to the main catchpit via a small diameter pipe in the left-hand side wall of the catchpit. At the time of monitoring, there was no monitoring equipment within the stilling well and the standing water level was different to the actual water level in the catchpit. If the stilling well were used for monitoring equipment, it is recommended that the structure undergoes some maintenance to clean out any sludge in the connecting pipe. All flow from the stream appears to be intercepted by the catchpit and piped to Grapevine Gut reservoir. There are no observable stream flows downstream of the structure.

10.1.2 Catchpit 2

Catchpit 2 (Plate 10) comprises a concrete wall 3.6m wide and 1.25m high which has been constructed across the low permeability bedrock of Grapevine Gut’s subsidiary catchment which drains the north east side of the catchment. The bottom of the stream also comprises impermeable bedrock at this location. A 0.145m ID HDPE outflow pipe is located in the centre of the wall, approximately 0.22m from the bottom. All flow from the stream appears to be intercepted by the catchpit and piped directly to Grapevine Gut reservoir. There is no observable stream bed or stream flow downstream of the structure, however the ground below the structure is very silted and boggy, possibly the result of the catchment surface water being intercepted. There is no monitoring equipment installed within the outflow pipe or in the catchpit to measure water levels or flow.

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Plate 9: Grapevine Gut Catchpit 1

Plate 10: Grapevine Gut Catchpit 2

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10.2 Wells Gut

10.2.1 Catchpit 1

The stream flowing into Catchpit 1 rests on lava bedrock and boulders which lie beneath a layer of peaty silt. Catchpit 1 in Wells Gut (Plate 11) comprises a concrete rectangle with the downstream wall 0.84m wide, with side walls 0.86m long. The structure is approximately 0.77m deep. The upstream end was open to allow stream water to flow into the structure. A 0.08m ID HDPE outflow pipe is located in the centre of the downstream wall, approximately 0.42m from the concrete base of the structure. A steel perforated pipe was connected to the outflow pipe within the structure.

It is believed that this catchpit collects spring flow from further up the Wells Gut catchment where seeps have been observed in the bedrock (see Plate 17). These seepage faces may be emanating from the contact between impermeable lava flows and permeable tuffaceous deposits. An assessment of the local area surrounding the catchpit observed that all streamflow was intercepted by the catchpit and piped away to Wells Gut water treatment works. The bottom of the Gut comprised a highly saturated peat covered with wild Yam, indicating that a large amount of water was stored within the peat. It is believed that the saturated peat provides a slow release baseflow to the lower part of the catchment. There was no sign of a stream channel downstream of the catchpit.

Plate 11: Wells Gut Catchpit 1

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10.2.2 Wells Gut Catchpit 2

Catchpit 2 (Plate 12) comprises a concrete rectangle with flared side walls on the upstream end of the structure. The downstream wall is 0.93m wide, with a 0.10m ID HDPE outflow pipe located 0.255m above the concrete base of the structure. A 0.1m ID metal perforated pipe is located within the structure which is connected to the outflow pipe. The perforated pipe is used to limit the ingress of debris into the pipe to avoid blockages. The concrete side walls are 1.22m long, with the flared side walls 1.43m long. The structure is 1.115m high.

A narrower diameter HDPE inflow pipe extends several centimetres out of the upstream wall of the structure. The pipe is located in the centre of the structure and had a steady flow of water cascading into the catchpit. Three holes were located at equal intervals on either side of the inflow pipe, but no water was flowing from them.

Connect state that the structure intercepts stream flow. It is possible that the structure was also designed to intercept baseflow from the peat which covers the bottom of the catchment or from the source of a spring lower down in Wells Gut between Catchpit 1 and Catchpit 2. The equal interval holes may also have been designed to intercept through flow. However, without the original design drawings or geology and hydrogeology data for the Gut, the actual nature of these holes or source of all inflow cannot be confirmed.

It was observed that all water intercepted by Catchpit 2 was piped to the above ground storage header tanks (Plate 13) downslope of Catchpit 2 which feed the Hutts Gate water treatment works. No surface water flow was observed below the catchpit.

10.2.3 Wells Gut Catchpit 3

Catchpit 3, incorporating a v-notch weir (Plate 14), intercepts stream flow at the bottom of Wells Gut by the Star Road. The structure is of concrete construction with an open upstream end. The stream bed is highly vegetated with a silty soil.

Gabions line the upstream bed of the catchpit to stabilise the structure. The downstream wall is 1.62m wide and 0.55m deep with a v-notch in the centre of the wall 0.51m wide and 0.235m deep. The sides of the “v” are at 45 degrees. The side walls of the structure are 2.4m and 2.33 long. A small concrete chamber is located downstream of the v-notch weir where a metal flanged outflow pipe is located which pipes stream flow within the catchpit to Hutts Gate water treatment works. A smaller diameter black “washout” pipe is located below and to the right of the metal flanged outflow pipe. Water flowing from this pipe provides a surface water baseflow flow below the structure. The surface water then flows beneath the Star Road and into a stream in Fishers Valley.

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Plate 12: Wells Gut Catchpit 2

Plate 13: Wells Gut Above Ground Storage Header Tanks

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Plate 14: Wells Gut Catchpit 3 and V-Notch Weir

10.3 Byrons Gut

10.3.1 Byrons Gut Spring Source

The spring source at Byrons gut (Plate 15) comprises a buried concrete structure of unknown dimensions. A steel and HDPE outflow pipe with manual flow valve is located on the downstream side of the structure. It is understood that the spring flow is piped to Hutts Gate water treatment works. Connect have confirmed that spring flows are not recorded at this location.

10.3.2 Byrons Gut Catchpit

The catchpit in Byrons Gut (Plate 16) is of concrete construction and comprises an open upstream end intercepting stream flow. The stream bed above the structure comprises low permeability lava pebbles, cobbles and boulders with a fine silt. The 0.86m wide downstream concrete wall has a 0.10m ID HDPE outflow pipe which is connected to a metal perforated pipe located within the catchpit (similar to Wells Gut catchpit 2). The outflow pipe is located within the centre of the concrete wall, 0.12m above the concrete base of the structure. The structure is 0.645m high, with side walls 2.02m long which flare out at the upstream end. It is understood that all stream flow intercepted by the catchpit is piped into the above ground header tanks below the catchpit (which also store Wells Gut Catchpit 2 water) and then on to Hutts Gate water treatment works.

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Plate 15: Byrons Gut Spring Source

Plate 16: Byrons Gut Catchpit

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10.4 Sources of Water

During the survey, the team confirmed that the catchpits in Grapevine Gut collected water from two separate streams running either side of a ridge which bisects the gut. The principal stream was found running into Catchpit 1 in Grapevine Gut. The source of water in Grapevine Gut could not be identified due to the dense vegetation in the gut but is thought to be from springs and seepage faces.

A single stream was identified in Wells Gut, with each catchpit intercepting flow further down the sub- catchment. A single stream was identified in Byrons Gut, originating from an upstream spring source.

Surface water in Wells Gut is understood to originate from seepage faces and springs within the catchment but are hard to identify due to the dense vegetation in the gut. A seepage face in Wells Gut, below Cabbage Tree Road is shown in Plate 17. Vegetation is very dense in Grapevine Gut, so the identification of seep and spring sources is difficult. Given the close proximity of the sub-catchments and the regional geology, it would be surprising if some flow in Grapevine Gut did not originate from seepage faces and springs.

Steam beds in both Grapevine Gut and Wells Gut were observed to mainly comprise low permeability lava boulders, pebbles and cobbles with fine silt. In areas where peat was identified, the stream beds were very narrow, with the majority of water in the bottom of the Gut being held in storage within the saturated Peat.

There is no general stream monitoring within Grapevine Gut or Wells Gut. All stream flow data is related to water intercepted by the catchpits for distribution to the Hutts Gate treatment works. Consequently, stream flows reported in Section 9.2 may be under reporting total flows in each Gut, as slow release water stored in the peat will also provide a baseflow to surface water lower down the catchment. Flow data recorded by Connect is also collected at the downstream end at the water treatment works and could be under reporting actual flow due to transmission losses.

No boreholes or standpipes were identified within Wells Gut, Byrons Gut and Grapevine Gut.

Plate 17: Seepage Face in Wells Gut

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11 Remote Sensing

Quantifying the distribution and abundance of plants is of fundamental importance to plant ecology. Our ability to estimate plant distributions over large areas (i.e. several hectares) using traditional approaches (transect or quadrant methods) is generally limited because of the time and expense required (Cruzan et al., 2016). For DPLUS051, being able to start understanding the relationship between climate and vegetation in Wells Gut and Grapevine Gut required the assessment of the type and abundance of vegetation found within each sub-catchment (reported in Section 12). However, the steep topography of the montane cloud forest and size of the study area (Wells Gut – 14.7 ha, Grapevine Gut 23 ha) precluded detailed ecology surveys on the ground due to accessibility and cost considerations.

An alternative approach was to trial the use of low level aerial photography to support species/habitat identification.

11.1 Aerial Surveys

Aerial photographs have been taken since 1858 and are captured by a variety of methods including hot-air balloons, kites, rockets, aircraft, helicopters, remotely operated aircraft and satellites. A comprehensive review of the history of aerial photography and systems for photogrammetry and remote sensing can be found in Colomina and Molina, (2014).

The measurement of ecosystems, forest structure and tree canopy height using a remotely operated Small Unmanned Surveillance Aircraft (SUSA), commonly known as “drones”, has been developing for several years and is maturing as methodologies and technologies improve. A variety of papers have been published on the use and reliability of drones, including measuring tropical forest recovery in Costa Rica (Zahawi et al., 2015), seagrass ecosystems (Duffy et al., 2018), dryland vegetation (Cunliffe, Brazier and Anderson, 2016). Evaluations have been carried out in a number of challenging locations (Duffy et al., 2017) assessing the reliability of aerial photogrammetry compared to ground surveys (Mlambo et al., 2017). Papers evaluating the use of drones for community based forest monitoring (Paneque-Gálvez et al., 2014) and catchment scale water resource management (DeBell et al., 2016) have also assessed the maturity of drone technology and the practicalities of implementing drone data into day to day operations. In all studies, drone technology has been found to be a quick and relatively inexpensive method of obtaining data that historically would have been expensive and time consuming to acquire.

The principal drivers for trialling the use of drones for the Darwin Plus project were:

• Size of the study area; • Accessibility – steep sided montane cloud forest limiting access on foot; • Cost of ground-based ecology surveys; and • Evaluating drone technology for management of the Peaks NCA (e.g. planning conservation work, evaluating restoration programme success).

Discussions with the EMD Conservation Manager in 2015 and 2016 indicated a desire to compare aerial photographs of key conservation areas on an annual basis, as there was little comparative data available to measure the success of conservation work. This data would be beneficial for assessing

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DPLUS051 Project Report progress of the Peaks NCA invasive species eradication programme and to evaluate the success of re- forestation and the general health of the cloud forest over time.

Data sets to be compiled were:

• Orthomosiac aerial images for species identification and distribution; and • Digital elevation models to evaluate the topography of each sub-catchment.

The methodology for the aerial surveys was limited to:

1. Create an orthomosaic aerial photo for Wells Gut and Grapevine Gut; 2. Use the orthomosaic aerial photo to complete a tree canopy survey for each sub-catchment; 3. Map the distribution of key invasive and endemic species forming the cloud forest tree canopy using QGIS; 4. Estimate the proportion of cloud forest tree canopy endemic and invasive species in each sub- catchment; 5. Undertake a limited ground survey of select locations within each sub-catchment, to confirm the results of the orthomosaic canopy survey and assess the diversity of plant species beneath the tree canopy.

Further interpretation of the orthomosaic aerial photos would be completed to assess the quality of the images and develop a Digital Elevation Models (DEM) for each sub-catchment.

11.1.1 Selection of a Drone

There are a variety of fixed wing and multi-rotor drones on the market, from systems costing over £10,000 to those under £1,000. Understanding which one is most appropriate for collecting ecology and topographic data depends on a number of factors, including:

• Size of the study area; • The payload that needs to be carried (camera, multispectral sensor); • Topography; • Resolution of images required; • Size of Take-Off and Landing Area (TOLA); • Weather(principally windspeed and precipitation); • Accessibility (distance of study area from TOLA); and • Permissions to fly – from landowner and airspace regulator.

A number of these factors are interdependent such as topography, TOLA, accessibility and permissions.

The key differences between fixed wing and multi-rotor drones are summarised in Table 5.

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Table 5: Fixed Wing vs Multi-Rotor Drones

Summary Multi-Rotor Fixed Wing

Manoeuvrability

Price

Size/Portability

Ease-of-use

Range

Stability

Payload Capacity

Safer Recovery from Motor Power Loss

Take-Off and Landing Area (TOLA)

Efficiency for Area Mapping

Source: Drone Deploy, 2017

A DJI Phantom 4 quadcopter was selected (Plate 18), as it was:

• Portable; • Straight forward to use; • Required a small TOLA; • Included an integrated 12mp RGB camera with 3-axis gimble for image stability; • Could hover allowing closer inspection of the study area;

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• Did not need to fly long distances away from the TOLA; and • Software allowed manual or automated flights to collect overlapping images.

Plate 18: DJI Phantom 4 Drone

11.1.2 Airspace Regulation

The Air Navigation (Overseas Territories) Order 2013 applies to Saint Helena and includes several restrictions on the use of the island’s airspace. Its primary concern is that of safety, ensuring that aircraft landing and departing at St Helena are not put at risk by man-made flying objects or ground- based hazards. The lower airspace over St Helena is made up of a Controlled Traffic Region (CTR). The Order restricts and prohibits other aviation activities within the CTR depending on whether an aircraft is flying through it. There are fewer restrictions on activities that take place on the west of the island, as aircraft are unlikely to be flying in this area. However, some restrictions remain in place to ensure air safety is maintained (Saint Helena Airport, 2018).

In addition to the Order, the islands airspace is regulated by Air Safety Support International (ASSI), part of the UK Civil Aviation Authority (CAA). ASSI is responsible for supporting the Overseas Territories' existing authorities in the safety regulation of all aspects of civil aviation. Saint Helena Airport is responsible for operation of the airport and implementation of the to ensure safety of aircraft, passengers and the general public.

11.1.3 Regulatory Permissions

The recently opened airport on Saint Helena is located approximately 5.5km east of the study area. Before starting any aerial surveys, permission from ASSI and Saint Helena Airport was required as the Peaks NCA is located within the Saint Helena Airport restricted fly zone (Plate 19).

A “Permission” to conduct aerial work was needed from ASSI before formally approaching Saint Helena airport for approval. As the aerial surveys were deemed to be a commercial operation, the project team were required to submit an Operations Manual (OM) written to UK CAA specification, along with an application to undertake aerial work. The OM outlined how the team would manage drone operations including the assessment health and safety risks and methods for maintaining equipment and recording flight logs.

The project OM (Appendix D) and a template OM (Appendix E) are provided as separate documents which accompany this main project report.

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The template OM is provided for use by other UK Overseas Territories, however it should not be copied word for word as ASSI require all drone operators to develop their own OM so that they understand and develop their own drone operations, risk assessments and methodologies.

The project flight team were awarded the islands first “Permission” in September 2016.

Plate 19: Saint Helena Airport Drone Flying Zones

11.1.4 Flight Planning

Pre-flight planning required the assessment of the study area for the following risks:

• Type of airspace and specific provisions • Obstructions (wires, masts, buildings (e.g. Controlled Airspace); etc.); • Other aircraft operations (local • Extraordinary restrictions such as aerodromes or operating sites); segregated airspace around prisons, • Notice to Airmen (NOTAMS); nuclear establishments etc. (suitable • Hazards associated with industrial sites or permission may be needed); such activities as live firing, gas venting, • Habitation and recreational activities; high-intensity radio transmissions etc.; • Public access; • Nationally protected sites, buildings and • Permission from landowner; monuments; • Likely operating site and alternative sites; • Environmental protection areas; and • Local byelaws;

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• Weather conditions for the planned operation.

The following risks were assessed at the start of each flight day to determine if the flights could take place:

• Study area shape, size, slope, orientation; • Land use within and surrounding the site; • Obstructions; • Public access; • Local weather conditions on day of • Proximity to structures (electricity pylons, operation (cloud cover, wind speed, telephone poles, buildings etc); humidity); • Proximity to roads; • Sources of radio interference (mobile • Line of sight obstructions; phone or radio masts); • Site security; and • Livestock; • Surface conditions of the site.

In addition, on each flight day the flight team implemented a protocol agreed with Saint Helena Airport to ensure that there were no unscheduled (medevac) flights and that Air Traffic Control were contacted at the start and finish of each flight.

Saint Helena Airport was consulted by ASSI during the permission application review and were subsequently provided with flight plans outlining the aerial surveys in the Peaks, contact details for the team and health and safety risk assessments. The flight plans for 2017 (an update of the 2016 flight plan) are provided in a separate document which accompanies this report (Appendix F).

11.2 Aerial Images and Data Processing

TOLA were selected in Wells Gut and Grapevine Gut based on the following criteria:

• Select a site that enables full visual • Avoid steep slopes or uneven ground; coverage of take-off and landing • Avoid waterlogged ground; operations; • Consider effects such as wind shear • Position in relation to the sun to avoid from nearby trees, buildings etc.; and visual impairment; • All buildings and persons not under the • Avoid physical obstacles such as control of the PIC must be 30 metres overhanging trees, rocks, buildings, away from the aircraft for Take-Off and power lines etc.; 50 metres in flight.

Given the steep topography and width of Cabbage Tree Road (which contours around each sub- catchment), the selected TOLA were not ideal, but presented the widest and flattest surfaces where the DJI Phantom 4 could start and finish a flight. The TOLA were at the highest points of each sub- catchment so that the flight team could see the study area, obstructions and potential airspace incursions without restricting visual line of sight.

In less challenging locations, the location of TOLA should also consider the elevation of the TOLA with regards to the surrounding area. For DPLUS051, the safest location was at the top of each catchment on the ridge. This introduced an unanticipated reduction in image quality whilst the drone flew in a grid 50m above the TOLA. For areas of the study area, this resulted in images at a resolution of 2cm per pixel as they were at a similar elevation to the TOLA. However, as the terrain reduced in height at

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DPLUS051 Project Report a distance from the TOLA, the ground was up to 184m below the drone, resulting in images with a resolution of 5cm per pixel (Figure 25). To maintain a more detailed image in large study areas of undulating terrain, it is recommended that more than one TOLA is selected to maintain a 2cm per pixel resolution.

Figure 25: Image Resolution Changing with Ground Level

11.2.1 Orthomosaic

The flight team evaluated several software solutions to determine the best means of acquiring an orthomosaic, NDVI and DEM data for the sub-catchments. DJI Go4, Autopilot and DroneDeploy were used, with DJI Go4 providing the most straight forward solution for manual flights. DroneDeploy provided the best results for automated flights and allowed the selection of photograph overlap (front and side) as well as timed photographs. The best photographs were produced using DroneDeploy with an 80% side and front overlap taken at 2 second intervals. The software also allowed pre-planned flights to be suspended when the drone needed a fresh battery. Maps Made Easy and DroneDeploy were the principal post processing cloud-based tools used to develop the sub-catchment orthomosaic and DEM.

An orthomosaic for the study area is shown in Figure 26 with a maximum resolution of 5cm per pixel.

The orthomosaic was used to complete a vegetation survey of the study area by assessing the land area covered by key species of endemic and non-native plants (Section 12).

11.2.2 Digital Elevation Model (DEM)

The creation of an accurate DEM was a challenge, as the identification of ground control points to accurately fix elevation and grid reference was limited due to the study area topography and dense vegetation. The location of 14 iButton temperature and humidity monitoring locations were selected as ground control points, as they were spread across the study area in areas that were accessible to the survey team. The model was extracted from the location and elevation meta data associated with each photograph used to create the orthomosaic image. A DEM for the study area is presented in Figure 27.

Cross-sections and profiles for each sub-catchment were also developed using data from the DEM and are presented in Figure 28 and Figure 29. The sections and profiles are similar for both sub- catchments. The cross-section profiles created using drone imagery are not perfect, as can be seen in

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DPLUS051 Project Report the cross-section for Grapevine Gut (B-B1), where the section includes the top of the tree canopy within the profile rather than showing true ground level (in the centre of the section). Using additional ground control points within the study area would enable a true ground level to be mapped in these areas.

11.2.3 Calculated Watershed and Catchment Area

The DEM was imported into QGIS v2.18.15 (Las Palmas). QGIS was used as the project GIS software because it was also used by project partners on St Helena, other UKOT environment teams and NGO’s and it is free.

QGIS has a wealth of tools and add-ins used to interpret mapping data including the modelling of catchment areas using DEM’s. The project DEM processed from the orthomosaic image for Grapevine Gut and Wells Gut was used with the SAGA Catchment Area (Flow Tracing) tool to delineate the sub- catchments. A shapefile was extracted from the flow tracing shapefile and edited to delineate the final sub-catchments.

The calculated watershed is presented in Figure 30. The catchment areas for Grapevine Gut and Wells Gut are presented in Figure 31. The area of each catchment area is presented in Table 6.

Table 6: Area of Sub-catchments

Area Units Grapevine Gut Area Wells Gut Area

m2 207,568 140,409

ha 21 14

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Figure 26: Wells Gut and Grapevine Gut Orthomosaic

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Figure 27: Wells Gut and Grapevine Gut Digital Elevation Model

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Figure 28: Long Profile and Cross Section Locations

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Figure 29: Sub-catchment Long Profiles and Cross Sections

Wells Gut Long Profile A to A1 Grapevine Gut Long Profile A to A1

775 725.00

705.00

725 685.00

665.00

675 645.00

625.00

Elevation (mASL) Elevation 625 Elevation (mASL) Elevation 605.00

585.00

575 565.00

545.00

525 525.00 0 100 200 300 400 500 600 0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00 400.00 450.00 DIstance (m) DIstance (m)

Wells Gut Cross Section B to B1 Grapevine Gut Cross Section B to B1

675 755

665 735

655 715

645 695

635 675 625

655 615 Elevation (mASL) Elevation Elevation (mASL) Elevation

635 605

615 595

585 595

575 575 0 50 100 150 200 250 300 350 400 450 0 100 200 300 400 500 600 DIstance (m) DIstance (m)

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Figure 30: Study Area Calculated Watershed

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Figure 31: Study Area Catchment Areas

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12 Vegetation Survey

12.1 Methodology

Aerial photos of Wells and Grapevine Guts were collected using the DJI Phantom 4 drone (Section 11.2). The photos were used to complete a desktop canopy survey and provide maps for a ground truthing field survey. Vegetation was mapped using QGIS, using categories identified from the orthomosaic for each Gut by drawing polygons around patches of vegetation with similar canopy type. The canopy vegetation was easily identifiable and represented different vegetation classifications (Table 7). The desktop study was then validated in the field in order to verify the vegetation classification and distribution.

The maps were validated over two days in 2017 to verify the canopy species, ascertain that they were indeed separate vegetation classes and identify the understorey species which do not show on aerial photos. The surveyor walked along the public access trails (including Cabbage Tree Road) at the tops of the ridges and walked through each gut recording the canopy and understorey vegetation. It should be noted that the guts are extremely steep and as a consequence, binoculars were used to confirm canopy vegetation within inaccessible locations. Generally, it was possible to walk from the public walking trail on the high ridge down through a gut until the slope became too steep, and then climb back out. Each vegetation category was visited at least once in each Gt to verify the vegetation. The guts were also visited from below, walking upwards until they were inaccessible.

12.2 Vegetation Survey Categories and Map

The completed vegetation survey map is presented in Figure 32. The survey map has been produced using data collected from the desk-based canopy survey and field survey to record vegetation beneath the canopy. A summary of the vegetation identified in each sub-catchment is presented in Table 7.

Table 7: Sub-Catchment Vegetation Classification

Item Grapevine Gut Wells Gut

Area 21 ha 14 ha

Native/Endemic 1.3 ha 2.37 ha

Non-Native 19.67 ha 11.63 ha

Pasture 41.0% 6.9%

Flax 32.2% 49.3%

Flax & Whiteweed 32.7% 25.8%

Black Scale Fern 1.4% 2.1%

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Item Grapevine Gut Wells Gut

Tree Fern Thicket 4.9% 14.8%

Forestry Trees 23.8%

Yam 0.2% 1.0%

Jellico 0.1%

The vegetation classification has been split into 8 groups. A description of each vegetation classification is provided below.

12.2.1 Flax

Over 90% cover of flax canopy which is almost a monoculture. Some additional invasive species in flax include bilberry, whiteweed, and forestry conifers. Some scattered pockets of endemic trees, tree ferns and black scale fern.

12.2.2 Tree fern thicket

Tree fern dominated endemic cloud forest with black cabbage trees. Interspersed with other endemic trees such as whitewood, dogwood, and he cabbage. Also endemic ferns and shrubs such as black scale fern, brown scale fern, plastic fern, comb fern, hens and chicks fern, cristella, lobelia, and Diana’s peak grass. Also includes significant invasive species such as fuchsia, pheasant tail fern, cinchona, Mexican creeper, bilberry, and occasional flax.

12.2.3 Black scale fern

Fern thicket dominated by black scale fern, plastic fern, hen and chick’s fern and cristella. Some tree ferns occasionally recorded here. Invasive species include some whiteweed and bilberry and occasional pheasant tail fern. This will develop to young tree fern thicket and exists through management actions.

12.2.4 Mixed flax and Whiteweed

Combination of flax and whiteweed, approximately 50:50 by canopy cover. Also includes bilberry and yam. Scattered pockets of endemics include tree ferns and black scale fern. Also scattered endemic trees such as whitewood, dogwood and black cabbage exist here.

12.2.5 Jellico

Stands of large Jellico. Canopy of Jellico, understory consists of hens and chicks ferns, black scale, plastic and cristella fern. Occurs in damp flushes on waterways.

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Figure 32: Wells Gut and Grapevine Gut Vegetation Survey

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12.2.6 Yam

Stands of yam. Interspersed with pockets of arum lily, black scale and cristella fern. Occurs on soaks and flat marshy areas only.

12.2.7 Pasture

Farming land for cattle and sheep. Dominated by introduced grasses and rushes. Shrubs of whiteweed, billy goat weed, bilberry, gorse and occasional flax. Sporadic thorn trees and conifer trees occur throughout.

12.2.8 Forestry trees

Canopy dominated by large conifers or eucalyptus trees for forestry purposes. Understory is diverse but patchy, with some patches dominated by endemics and others dominated by invasive species, regardless of what neighbouring vegetation canopy is. Invasive species include flax, gorse, whiteweed, bilberry; endemics include black scale fern, brown scale fern, plastic fern, hen and chick’s fern, tree fern, cristella, and comb fern.

12.3 Grapevine Gut Plant Ecology

Grapevine Gut is dominated by non-native plants. Approximately 6.5% native/endemic plant cover and 93.5% non-native. Flax is the dominant non-native vegetation type, with mixed flax and whiteweed second dominant, and forestry trees third dominant. There is a small area of pasture grass and stands of yam.

Native plants are located on the higher ridges towards the peak and include only two vegetation types: tree fern thicket (the most abundant) and small patches of black scale fern thicket occurring in areas actively managed for conservation.

12.4 Wells Gut Plant Ecology

Wells Gut had a higher ratio of native/endemic plants to non-native plants than Grapevine Gut but is still dominated by non-native plants. Well Gut has approximately 17% native/endemic and 83% non- native vegetation cover. Non-native plants were dominated by flax stands, which cover 50% of the gut. Mixed flax and whiteweed, pasture grasses and stands of yam cover an additional 34% of the gut.

The 17% native/endemic vegetation are composed of mainly tree fern thicket up high on the ridges, black scale fern thicket occurs on the high slopes conservation areas, and Jellico stands in steep guts where flax does not grow.

Above the public walking trail the vegetation is native/endemic, below the road is non-native, with exception of Byron’s Gut which has some excellent tree fern areas below the road.

12.5 Invasive Species control

All invasive species are targets of the Peaks Conservation Programme. However invasive species are only managed in tree fern thicket and black-scale fern thicket areas, as they have the greatest impact on native habitat in these areas. Methods of control are specific to species. Flax are removed by

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DPLUS051 Project Report chopping the leaves at the base and removing the entire tuber from the ground. Bilberry, cinchona and large whiteweed are controlled by cutting and applying herbicide (Garlon mixed with oil or diesel). Small whiteweed and small flax are pulled out by hand. Mexican creeper, pheasant-tail fern and fuchsia are removed by hand, but the result is temporary and the plants often regrow stronger after weeding.

The Darwin-Plus project Establishing the national framework for invasive plant management (DPLUS059) is currently trialling new methods of invasive species control in the Peaks National Park.

12.6 Endemic plant restoration techniques

Restoration of endemic plants has been ongoing at the peaks for almost 25 years. A programme run by the St Helena Government has been restoring habitat since 1995. A lot of lessons have been learnt through trial and error, with techniques refined over time to maximise success and make restoration as efficient as possible. There has been a lot of effort spent on restoring the cloud forest in recent years thanks to generous support from Darwin-Plus funded projects, as well as other funders such as the Royal Society for Protection of Birds, the BEST 2.0 Programme, and the St Helena Government.

Three restoration methods are used in the Peaks National Park: (1) clear fell an area and plant with natives, (2) plant amongst weeds using the weeds as shelter, then remove the weeds selectively in patches, and (3) spot cleaning by specific careful maintenance work. Each method has advantages and disadvantages and works under specific circumstances or for certain species.

The clear fell and plant method was the original method of restoration in 1995. It involved clearing invasive species in large areas (often up to a hectare at a time), usually down to bare soil, then planting many native plants to fill the space. The advantage of this method is that its fast, progress is easy to see, and there is a fast transition from invasive to native. This method has proven effective in areas of dense monoculture such as flax or banana, where an entire area is cleared and hundreds or thousands of natives are planted. Planting ferns and grasses quickly creates a ground cover, and planting native trees forms the foundation of a canopy. Dense planting of native species helps to suppress invasive species. The disadvantage of this method is that there’s a high risk of failure unless sustained effort is put in to planting more natives and removing any invasive species. There is also a long lead in time since enough native plants need to be ready for planting immediately after initial clear felling. It is also labour-intensive. For an area of flax of 0.5 hectares cleared in 2016 approximately 2,000 plants were required and staff had to revisit every three months for the first year to remove new invasive species.

The plant amongst weeds method works on the theory that invasive species can be useful for restoration. Endemics are planted amongst invasive species, sometimes with a very small amount of clearance, sometimes without any clearance at all. The idea is that invasive species provide the necessary canopy cover, shelter and protection for young endemics to grow strong and tall, enabling a slow transformation from invasive species to natives. This method is relatively new to the Peaks but has been successful in some areas of whiteweed in lower Grapevine Gut and Wells Guts. The advantages of the method are fewer natives need to be ready for planting before work can begin and it is labour-efficient as large-scale clearance of weeds is not necessary. When combined with slow- acting herbicides such as poison plugs, which slowly kill an invasive tree in situ, it allows time for a more natural takeover of native species. Disadvantages of the method are that regular monitoring is

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DPLUS051 Project Report required to ensure that plants survive, it can be very slow, and while the weeds are in situ they are still flowering and seeding.

The spot cleaning method in specific locations works on the principle that in areas that are already high quality, only a small amount of work is needed to have maximum gains. It involves careful removal of weeds and planting of natives in areas which are good quality. It has been successful in areas of tree fern thicket which are regularly maintained, such as the upper tree fern thicket in Wells Gut and Byron’s Gut, and upper Taylors in Grapevine Gut (in the region of WS02GVG). Occasional whiteweed, bilberry and flax grow amongst the tree ferns which are removed before they become a problem. Native species are planted in their place to improve the habitat. Regular maintenance reduces the chance for big weeds establishing themselves and allows different age classes of native trees to grow from each successive planting. Advantages of this method is it’s relatively easy, lots of ground is covered, and whatever plants are ready can go out from the nursery at any time. The disadvantages of this method are that regular access to good quality areas will trample soil and emergent native vegetation and create maintenance trails.

12.7 Long Term Changes in Vegetation

The Grapevine Gut land use map published by Mathieson (Mathieson, 1990) provides a useful benchmark for comparing changes in the sub-catchment over time. The map indicates that the sub- catchment is 22ha, which compares well with DPLUS051 aerial survey at 21ha.

There is no reference to tree fern thicket on the 1990 map, indicating the successful efforts of the island conservation teams to restore cloud forest endemic plants have been restored within the sub- catchment over the past 18 years. The maps also indicate that the area of flax has increased by approximately 25% since 1990. There is no reference to whiteweed on the 1990 map, again indicating that this invasive species has flourished within this time period.

Comparing mapping data over time provides a valuable tool for conservation teams, as it validates the success of restoration methods and gives guidance for planning future restoration work. It is recommended that all historic habitat mapping is digitised for future reference to support ongoing restoration of the island’s endemic plants and invertebrates.

13 Monitoring Network

13.1 Monitoring Location Selection

On 16th October 2016, the project team scouted for weather station monitoring locations with the DPLUS029 team (Lourens Malan and Andrew Darlow). Key issues identified when selecting monitoring locations were:

• Safe access to each site due to the very steep slopes of each sub-catchment; • Limiting damage to endemic plants within each sub-catchment (both for installing equipment and monthly downloads of data); and • Selecting locations where the equipment will be safe and not subject to vandalism or theft.

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Four weather station and soil moisture monitoring locations were identified in Perkins Gut, Wells Gut and Grapevine Gut with the DPLUS029 team. A formal survey of each site was completed to confirm the elevation and grid reference of each location where the weather stations are located.

The survey identified that access to Wells Gut from the Star Road was problematic due to the thick vegetation and blocked footpath. Access from Cabbage Tree Road down into Wells Gut was also an issue due to the thick vegetation.

Alongside monitoring locations identified during the water features survey, a total of 14 locations were identified for the installation of monitoring equipment. Full details of the monitoring locations can be found in the DPLUS051 Monitoring Network Manual (v1.1) which accompanies this report as a separate document as Appendix F. Each data sheet includes a location map, photograph of the feature, grid reference, elevation and description of equipment installed at each location.

The water features survey (Section 10) was also used to select monitoring locations for inclusion in the monitoring network and to evaluate vegetation clearance needed to access each monitoring location.

13.2 Monitoring Equipment

In order to calculate a water balance for Grapevine Gut and Wells Gut, several climate and water level data sets needed to be collected within the study area specifically:

• Surface water level and flow in springs and streams;

• Temperature and humidity in the cloud forest and surrounding area;

• Soil moisture content;

• General meteorological conditions of the south east and north west slopes of the Peaks; and

• Recharge in the study area which can be attributed to intercepted fog/mist within the cloud forest.

A list of monitoring equipment used is presented in Table 8 and monitoring locations are shown in Figure 33 and Figure 34.

The naming convention for each item of monitoring equipment was selected to identify the type of equipment, the number of items of equipment and location within the study area. As an example, the weather station located in Perkins Gut has the identification number WS01PG.

• WS – denotes weather station; • 01 – denotes weather station 1 (in the event of more than 1 weather station in Perkins Gut); • PG – denotes the location, Perkins Gut.

The following abbreviations are used for each item of equipment;

• WS – weather station; • IB – iButton; • MC – mist capture logger with rain gauge; • SW – surface water monitoring logger;

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• BP – barometric pressure logger • RF – rainfall rain gauge; • PG – Perkins Gut; • WG – Wells Gut; and • GVG – Grapevine Gut.

The DPLUS051 Monitoring Network Manual (v1.1) was used by the project team as a training resource and to support the collection of field monitoring data.

13.3 Meetings and Training

A project inception meeting was held in Essex House, Jamestown on Wednesday 5th October 2016 to re-introduce the project to the field survey team, discuss the field visit programme and to agree staff time and resources to tasks identified during the 4-week programme. Staff present at the meeting are presented in Table 9.

The monitoring team then completed training on Friday 11th October 2016 to go through the basics of water level and flow monitoring, the equipment being used and protocols for data collection. The team then spent three days in October 2016 installing the equipment and completing in-field training on protocols for downloading data from each monitoring location. Further training was complete in November 2017 associated with aerial surveys.

13.4 Data Collection

Field data has been collected in collaboration with DPLUS052, which purchased a YUMA2 rugged tablet computer operating Windows 7. Data from the Omni Instruments supplied portable weather stations was downloaded using a USB thumb drive, connected to a USB port in the weather station data logger. For the remainder of the field equipment (soil moisture sensors, water level data loggers, tipping bucket rain gauges), the YUMA2 rugged tablet was used to download data using each piece of equipment’s USB dongle.

Field staff from Connect, EMD and Arctium collected field data and repaired equipment as and when required.

Table 10 provides a summary of the project field data collection programme for DPLUS051, showing times when field staff downloaded data from the monitoring locations and any issues encountered with the equipment.

13.5 Site Security

Despite the remoteness of the monitoring locations and relatively small number of people who access the study area, some of the data loggers in Grapevine Gut and Wells Gut were removed from their monitoring locations. An investigation by the DPLUS051 monitoring team concluded that data loggers at SW02WG and SW02GVG were removed without consent, which resulted in gaps within the monitoring data.

It is regrettable that this occurred and has had an impact on some of the data sets. All monitoring locations had been selected to ensure there was limited opportunity for tampering of equipment and signs were posted at each monitoring location explaining the purpose of the equipment and providing project team contact details.

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Table 8: Monitoring Equipment

Organisation Equipment No. Monitoring Location Comment

Level Scout water level data logger 5 Wells Gut and Grape Vine Gut Deployed in streams and in tube wells and boreholes. (10m range)

Level Scout barometric data logger 1 Wells Gut Required to calibrate data collected from the Level Scout loggers.

iButton temperature and humidity 14 Wells Gut, Grape Vine Gut, Perkins Gut Located throughout the study area. data loggers and Byrons Gut

Metpak RG portable weather 3 Wells Gut, Grape Vine Gut and Perkins Automatic data logger installed with each weather station. DPLUS051 station Gut Project Hobo RG3-M rain gauge with data 5 Transect across the peaks Used with CEH fog/mist monitoring equipment. Cell batteries in the logger need logger changing on an annual basis.

ANRD rain gauges 19 Across the island Manual measurements collected by ANRD staff and volunteers.

ANRD fog collector 1 Hutts Gate water treatment works Manual measurements collected by ANRD and Connect Saint Helena staff.

Bottom Woods weather station 1 Bottom Woods Longest continuous weather monitoring station on St Helena – over 40 years. Equipment provided and maintained by UK Met Office.

Centre for Madgetech SMR101A soil 4 Transect across the peaks Deploy equipment with fog/mist monitoring equipment to determine change in Ecology and moisture sensor soil moisture with elevation. Loggers have 10-year battery life. Are being Hydrology provided on permanent loan by CEH.

Fog/mist monitoring equipment 5 Transect across the peaks Equipment on permanent loan from CEH. Hobo RG3-M rain gauge data loggers have been installed within fog/mist monitoring equipment. The fog/mist monitoring equipment are located in a transect across the Peaks, two on south east side (Sandy Bay side), one on the top (Diana’s Peak) and two on the north- west side (Wells Gut).

Connect Saint Diver water level data logger (10m 1 Grape Vine Gut Deployed in stream catch pits. Helena range)

Diver barometric data logger 2 Grapevine Gut and Wells Gut Required to calibrate data collected from the Diver and LevelScout loggers.

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Figure 33: iButton, Barometric Logger and Weather Station Monitoring Locations

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Figure 34: Surface Water, Flow, Mist Capture and Soil Moisture Logger Monitoring Locations

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Table 9: Staff Present at Fieldwork Inception Meeting

Organisation Staff Project Role

Arctium Ben Sansom Project Manager and Technical Lead

Leon de Wet Project Partner

Heila Butters Connect Manager and Key Contact for Project

Connect Saint Helena Paul Cherrett Water Resource Engineer

Paul Duncan Water Resource Engineer

Ricardo Fowler Water resource Engineer

Derek Henry Project Lead

Sam Cherrett GIS Specialist and DPLUS052 Environmental Management Project Manager Division, Saint Helena Government Elizabeth Cairns-Wickes GIS Support

Mike Jervois Project Ecologist

Table 10: Project Field Data Collection Logbook

Date Staff Comments

January 2017 EMD and Connect Staff. WS01WG battery dead – unable to download data.

SM01DP(WG) not working.

Equipment working well at all other sites visited during the day.

February 2017 EMD staff. Wells Gut Catchpit 2 and Grapevine Gut Catchpit equipment working well.

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Date Staff Comments

WS01WG battery charged and re-installed and WS01GVG weather station cable fixed on Friday 3rd February.

May 2017 EMD staff. Vegetation clearance around monitoring locations.

WS01WG and WS01GVG working well. WS01PG battery is dead. Internal battery required replacing.

SM02GVG and SM01DP logger batteries are dead. Batteries replaced, however new batteries were draining too fast for loggers to be used in the field.

Unable to download data from the mist capture logger MC01DP. Possible battery replacement or faulty data logger.

June 2017 EMD Removal of MC01DP from site as the data logger was not working. The Hobo data logger battery was replaced, but the problem persisted. Possible faulty data logger hardware.

July 2017 Connect Data collected from a limited number of locations.

October and Arctium and EMD Downloaded data from all loggers. November 2017 Weather stations WS01PG, WS01WG and WS01GVG not working. All internal batteries replaced, rechargeable batteries recharged and installed. No signal from sensors to the weather station Datataker data logger. A check of connecting cables showed heavy corrosion within 9 pin plugs. Replacement cables needed to repair the weather stations. New cables ordered to arrive on island late January 2018.

MC01DP data logger inspected. All data lost between March 2017 and October 2017 due to malfunction of data logger. Logger battery replaced again in November 2017 and logger re-started. The logger has been moved to the site of MC02PG as there are still concerns about its reliability. The location of MC02PG is less critical to the project should problems with the logger persist.

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Date Staff Comments

MC01PG Hobo rain gauge data logger was removed from site and used to replace the damaged mist capture data logger at MC01DP.

MC02PG Hobo rain gauge data logger removed from site and installed at Grapevine Gut weather station location.

MC02WG Hobo rain gauge data logger removed from site and installed at Wells Gut weather station location.

SM01DP data logger replacement USB cable used to download data. The same communications problem persists with the logger. Possible hardware problem.

BP01GVG logger was found to have been removed from site as the logger memory was full. The logger was downloaded and installed back in the field in November 2017 recording at 1h intervals. Data from BP01WG can be used as the logger is close to Grapevine Gut.

Logger SW02GVG was also found out of the water in Grapevine Gut in November 2017. The reason for this was unknown, but the site is located within a secure compound. The logger was re-started and installed in November 2017.

BP01WG logger stopped recording in June 2017. Logger memory cleared and re-started in November 2017 recording at 1h intervals.

February 2018 EMD/SHNT Data download. Problems downloading data from SW03WG at the V-notch weir. Logger is working as was re-started in November 2017. Will attempt to download during the next site visit at the end of April.

Continuing problems with soil moisture loggers at Diana’s Peak and in Grapevine Gut.

Weather station cables were not replaced due to additional wiring needed. Postponed until end of April 2018. New rain gauges in Wells Gut and Grapevine Gut weather station locations are providing key data as an alternative.

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Date Staff Comments

May 2018 EMD Final data download. Surface water loggers in Wells Gut were not logging.

June 2018 EMD/ANRD Equipment removal from the study area. A pair of rain gauges and mist loggers were left on Diana’s Peak and at the location of Grapevine Gut weather station to continue collecting mist and rainfall data. A pair of iButtons (IB01GVG and IB01DP) were also left at both locations to collect temperature and humidity data.

14 Monitoring Data and Interpretation

Monitoring data has been collected from a variety of locations discussed in Section 13. The length of data record for each monitoring location is presented in Table 11.

Table 11: Field Monitoring Data Record

Catchment Monitoring Location Data Record Length

MC01PG 12 months data. October 2016 to October 2017.

MC02PG 10 months data. October 2016 to October 2017.

Perkins Gut WS01PG 4 months data. October 2016 to February 2017.

iB01PG 20 months data. October 2016 to June 2018.

iB02PG 19 months data. October 2016 to May 2018.

MC01DP 10 months data. October 2016 to March 2017 and November 2017 to May 2018.

Diana’s Peak SM01DP No data due to logger failure.

iB01DP 19 months data. October 2016 to May 2018.

WS01GVG 7 months data. 2 months unreliable data before sensors failed. Grapevine Gut October 2016 to June 2017.

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Catchment Monitoring Location Data Record Length

iB01GVG 19 months data. October 2016 to May 2018.

iB02GVG 19 months data. October 2016 to May 2018.

iB03GVG 19 months data. October 2016 to May 2018.

iB04GVG 19 months data. October 2016 to May 2018.

iB05GVG 19 months data. October 2016 to May 2018.

RF01GVG 5 months data. Hobo rain gauge (was previously used as MC01PG). November 2017 to April 2018.

SW01GVG 12 months data. October 2016 to October 2017. Additional flow data collected at this location by FL01GVG.

SW02GVG 15 months data. October 2016 to June 2016 and November 2017 to June 2018.

FL01GVG Blue Siren flow logger, 7 months continuous data. November 2017 to June 2018.

BP01GVG 17 months data. October 2016 to July 2017 and November 2017 to June 2018.

SM01GVG 19 months data. October 2016 to May 2018.

SM02GVG No data. Sensor is irreparable – near end of life equipment donated by CEH (not included in original project design).

WS01WG 4 months data collection. March to June 2017.

MC01WG 17 months data. October 2016 to September 2017 and November 2017 to May 2018. Wells Gut

MC02WG 12 months data. October 2016 to October 2017. Removed from site and used as rain gauge at location of Wells Gut weather station.

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Catchment Monitoring Location Data Record Length

SM01WG 19 months data. October 2016 to May 2018.

iB01WG 15 months data. October 2016 to February 2018.

iB02WG 12months data. October 2016 to November 2017.

iB03WG 15 months data. October 2016 to February 2018.

iB04WG 19 months data. October 2016 to May 2018.

BP01WG 16 months data. October 2016 to July 2017 and November 2017 to June 2018.

SW01WG 12 months data. October 2016 to October 2017.

SW02WG 12 months data. October 2016 to October 2017.

SW03WG 12 months data. October 2016 to October 2017.

RF01WG 6 months data. Hobo rain gauge (was previously used as MC02PG). November 2017 to April 2018.

iB01BG 19 months data. October 2016 to May 2018.

Byrons Gut iB02BG 15 months data. October 2016 to February 2018.

SW01BG 12 months data. October 2016 to October 2017.

Table 12 summarises the climate parameters recorded across the study area and identifies where duplicate parameters have been recorded.

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Table 12: Climate Data Equipment

Equipment

Parameter Portable Weather Hobo Rain Gauge Diver and BaroScout iButton Station Data Logger Barometric Loggers

Rainfall ü ü

Dew Point ü

Temperature ü ü ü ü

Humidity ü ü

Barometric Pressure ü ü

Wind Speed ü

Wind Direction ü

Temperature, humidity, dew point, rainfall, atmospheric pressure, wind speed and wind direction measurements have been collected at by the portable weather stations. Temperature and mist (as rainfall) has been collected by the Hobo rain gauge data loggers, installed beneath the CEH mist capture equipment. The barometric data loggers have been used to correct water level measurements collected in catch pits and the Wells Gut v-notch weir.

The performance of the portable weather stations has been significantly below expectations due to a combination of problems with rechargeable batteries, solar panels and corrosion of data cables due to the island’s aggressive environment. This has resulted in significantly reduced data record at these locations. It should be noted that temperature and atmospheric data was also recorded by iButtons at the weather station locations providing some complementary data.

The longest weather station data set is WS02GVG, with a climate record from 26th October 2016 to 9th September 2017. Only 9 days data was lost between June and July 2017. The cause is thought to be due to problems with the solar panel charging the battery. It is also noted that some barometric pressure data collected in July 2017 was also of poor quality although the cause is unknown. Two Hobo rain gauge data loggers used for measuring mist were re-purposed from Perkins Gut and Wells Gut to measure direct rainfall at the location of WS02GVG and WS03WG between November 2017 and April 2018 (RF01WG and RF02GVG).

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The weather stations at Perkins Gut (WS01PG) and Wells Gut (WS03WG) have operated for shorter periods of time. The presence of mist capture and iButton data loggers at the weather station sites has enabled the collection of duplicate data sets for a small number of parameters. As a consequence, there is a continuous data record for temperature and humidity at WS01PG and WS03WG for comparison with the weather station at Grapevine Gut (WS02GVG).

Similar problems were experienced operating automatic weather stations in the Peaks by CEH during 1996 and 1997, where equipment breakdowns and logging faults prevented continuous recording of climate data, many of which were not entirely resolved (Gunston and Rosier, 1997).

14.1 Wind Speed and Direction

14.1.1 Perkins Gut

The wind speed record for Perkins Gut weather station is only 3 months long due to long term reliability issues with the equipment related to corrosion of data cables. Consequently, only a short- term data set between 26/10/16 and 14/01/17 is available for review and is presented in Figure 35. This is too short to interpret in detail, but indicates that during the islands early summer months the wind direction on the south east side of the Peaks NCA was predominantly from the south west, with a mean wind speed of 0.64 m/s. During this period, 11% of days were recorded as calm (wind speed <0.30 m/s). Perkins Gut is oriented south east with steep slopes facing Sandy Bay.

14.1.2 Grapevine Gut

The longest wind speed record was collected at Grapevine Gut weather station (WS02GVG) between October 2016 and September 2017. The weather station is located on the north west side of the Peaks NCA. Data are presented in Figure 36 and Figure 37. The data record was limited to 11 months due to long due to long term reliability issues of the equipment, principally related to corrosion of data cables.

Grapevine Gut is horse-shoe shaped and orientated in a northerly direction, with the ridge of the Peaks NCA forming its eastern, southern and western boundaries. There are no high landforms south of Grapevine Gut, allowing winds blowing from Sandy Bay to reach Grapevine Gut unobstructed. The wind rose in Figure 36 confirms the prevailing wind direction from the south, with a mean wind speed of 1.72 m/s, maximum of 5.34 m/s and frequency of 1.35 to 1.49 m/s. During the monitoring period, no calm days were recorded. The wind rose indicates that winds do change direction, however they remain from a predominantly southerly direction. During the field work, the cloud base was observed flow over the Halley’s Mount ridge which separates Grapevine Gut from Wells Gut, confirming that an easterly wind occasionally blows parallel to the Peaks. This is also shown on the wind rose, but only during periods with an easterly wind greater than 1.5 m/s.

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Figure 35: Perkins Gut Wind Rose

Figure 36: Grapevine Gut Wind Rose

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Figure 37: Grapevine Gut Wind Speed Frequency

GV02WS Average Hourly Wind Speed (m/s) Frequency 26/10/16 to 11/09/17 700

624 605 600 595

530 536

500 490 483

410 400 352 342 323 300 256

Wind Speed Frequency Speed Wind 227 216 200 190 175 158 157 135 122 107 100 82 70 49 35 41 39 26 13 12 13 12 7 9 4 4 4 1 0 [0.09, 0.23] 0.37] (0.23, 0.51] (0.37, 0.65] (0.51, 0.79] (0.65, 0.93] (0.79, 1.07] (0.93, 1.21] (1.07, 1.35] (1.21, 1.49] (1.35, 1.63] (1.49, 1.77] (1.63, 1.91] (1.77, 2.05] (1.91, 2.19] (2.05, 2.33] (2.19, 2.47] (2.33, 2.61] (2.47, 2.75] (2.61, 2.89] (2.75, 3.03] (2.89, 3.17] (3.03, 3.31] (3.17, 3.45] (3.31, 3.59] (3.45, 3.73] (3.59, 3.87] (3.73, 4.01] (3.87, 4.15] (4.01, 4.29] (4.15, 4.43] (4.29, 4.57] (4.43, 4.71] (4.57, 4.85] (4.71, 4.99] (4.85, 5.13] (4.99, 5.27] (5.13, 5.41] (5.27, Wind Speed Bin

14.1.3 Wells Gut

The wind speed record for Wells Gut weather station is only 7 months long due to long term reliability issues. As a consequence, only a short-term data set between 02/02/17 and 12/09/17 is available for review and is presented in Figure 38.

Figure 38: Wells Gut Wind Rose

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During this period, the weather station experienced issues with data cables similar to WS01PG and WS02GVG, consequently readings were not continuous during the period when data was collected. Wells Gut is located on the northern side of the Peaks NCA, is horse-shoe shaped and orientated in a north-easterly direction, with the ridge of the Peaks NCA forming its eastern, southern and western boundaries. During the field work, the cloud base was observed flow over the central Peaks ridge between Diana’s Peak and Mount Actaeon from the south east and also from the east, parallel to the central ridge flowing over the ridge separating Legg’s Gut to the east and Wells Gut.

Based on the available data, the wind rose in Figure 38 shows a prevailing wind direction from the south south-east with wind flowing over the central Peaks in a easterly wind direction. A mean wind speed of 1.39 m/s was recorded, with a maximum of 7 m/s. No calm days were recorded.

14.1.4 Wind Data Summary

The data set is too short to evaluate longer term average wind speeds and direction at each monitoring location. However, the data confirm visual observations that wind direction is predominantly from the south and south east, however winds at Wells Gut are more variable and come from the south east and the east in equal measure. Recorded wind speeds averaged between 1.39 m/s and 1.72 m/s at Grapevine Gut and Wells Gut with maximum recorded wind speeds ranging between 5.34 m/s and 7.0 m/s at both locations.

14.2 Temperature and Humidity iButton temperature and humidity data are summarised in Table 13, Table 14 and Figure 39 as monthly averages.

Average monthly temperatures recorded in the Peaks between November 2016 and May 2018 ranged between a minimum of 13.7oC (IB01GVG) and maximum of 21oC (IB01PG) with a seasonal average of 16.9oC across the study area. Highest temperatures were recorded in Perkins Gut where temperatures were constantly higher than in Grapevine Gut and Wells Gut. Average monthly temperatures in south east facing Perkins Gut ranged between 1.2oC and 0.3oC higher than the northern facing Grapevine Gut and Wells Gut. Byrons Gut and Diana’s Peak averaged 16.7 and 16.8oC respectively.

Average monthly humidity recorded in the Peaks between November 2016 and May 2018 ranged between a minimum of 59.4%RH (IB03WG) and maximum of 113.7%RH (IB04GVG) with a seasonal average of 97.4%RH across the study area. Humidity in Grapevine Gut averaged 100%RH and in Wells Gut 94%RH. Byrons Gut and Diana’s Peak averaged 100%RH.

Temperature and relative humidity isohyets based on annual average data between November 2016 and October 2017 are presented in Figure 40 and Figure 41. Annual average temperatures in the study area ranged between 16oC (IB03GVG) and 17.5oC (IB02PG). The temperature isohyet confirmed that cooler air is located along the ridges with an increase in temperature as elevation reduces. Annual average humidity across the study area ranged between 78.4%RH (IB03WG) and 105.3%RH (IB04GVG). The humidity isohyet shows that humidity increases across the Peaks from south east to north west following the prevailing wind direction.

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Table 13: Temperature Data

IB01WG IB02WG IB03WG IB04WG IB01PG IB02PG IB01GVG IB02GVG IB03GVG IB04GVG IB05GVG IB01DP IB01BG IB02BG Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature (DegC) (DegC) (DegC) (DegC) (DegC) (DegC) (DegC) (DegC) (DegC) (DegC) (DegC) (DegC) (DegC) (DegC) Date 778mASL 764mASL 665mASL 638mASL 724mASL 747mASL 783mASL 764mASL 590mASL 660mASL 640mASL 834mASL 688mASL 658mASL Nov-2016 15.3 16.2 16.0 16.1 16.8 16.2 15.0 15.9 15.2 16.8 15.8 15.3 15.6 16.4 Dec-2016 16.6 17.5 17.2 17.3 18.4 17.8 16.3 17.2 16.5 17.9 17.0 16.9 16.7 17.3 Jan-2017 18.6 18.7 18.7 18.5 21.0 19.7 17.9 19.1 17.8 18.9 18.4 18.8 18.1 18.8 Feb-2017 18.6 19.0 18.9 19.1 20.4 20.0 18.4 19.5 18.1 19.0 19.0 18.9 18.5 18.8 Mar-2017 18.8 19.1 19.1 19.1 19.7 19.9 18.7 19.4 18.5 19.1 19.3 18.8 18.9 18.9 Apr-2017 18.4 18.4 18.5 18.1 18.9 19.5 18.7 19.1 17.8 19.0 19.1 18.4 18.4 18.5 May-2017 18.1 17.9 18.0 17.5 18.6 19.4 18.8 18.3 17.3 18.5 19.0 17.9 17.7 18.2 Jun-2017 15.5 15.8 16.0 15.6 15.9 16.7 15.8 15.6 15.4 16.2 16.4 15.3 15.9 15.7 Jul-2017 14.7 14.8 15.1 14.5 14.9 16.0 15.1 14.9 14.3 15.1 15.5 14.4 14.8 14.8 Aug-2017 14.3 14.9 14.9 14.7 14.8 15.6 14.2 15.2 14.3 14.9 15.4 14.1 14.7 15.2 Sep-2017 13.9 14.8 14.4 14.0 14.3 15.2 13.8 14.8 14.0 14.4 15.0 13.8 14.4 15.0 Oct-2017 13.8 14.5 14.2 14.0 14.3 15.2 13.7 14.4 13.8 14.3 14.5 14.0 13.8 14.4 Nov-2017 14.9 15.9 15.5 15.5 16.2 16.6 14.8 15.7 14.7 15.7 15.5 15.2 14.7 15.6 Dec-2017 15.8 16.0 15.8 17.2 17.6 15.5 17.1 15.2 16.6 15.8 16.4 15.2 16.1 Jan-2018 16.7 17.0 17.0 17.7 18.3 16.7 17.5 16.4 17.3 16.9 17.0 16.4 17.1 Feb-2018 17.8 18.1 18.2 19.9 20.3 18.1 19.6 17.7 18.5 18.2 18.9 17.9 18.9 Mar-2018 18.2 19.8 20.4 18.8 19.6 18.1 18.7 18.6 19.2 18.5 Apr-2018 18.2 19.1 19.6 18.6 19.0 18.0 18.5 18.3 18.5 18.2 May-2018 17.0 17.1 18.3 17.3 16.9 16.8 17.2 18.1 17.0 16.8

Min 13.8 14.5 14.2 14.0 14.3 15.2 13.7 14.4 13.8 14.3 14.5 13.8 13.8 14.4 Max 18.8 19.1 19.1 19.1 21.0 20.4 18.8 19.6 18.5 19.1 19.3 19.2 18.9 18.9 Average 16.4 16.7 16.7 16.8 17.6 18.0 16.7 17.3 16.3 17.2 17.1 16.8 16.6 16.9 95%ile 13.9 14.7 14.3 14.0 14.3 15.2 13.8 14.8 14.0 14.4 14.9 14.0 14.3 14.7

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Table 14: Humidity Data

IB01WG IB02WG IB03WG IB04WG IB01PG IB02PG IB01GVG IB02GVG IB03GVG IB04GVG IB05GVG IB01DP IB01BG IB02BG Humidity Humidity Humidity Humidity Humidity Humidity Humidity Humidity Humidity Humidity Humidity Humidity Humidity Humidity (%RH) (%RH) (%RH) (%RH) (%RH) (%RH) (%RH) (%RH) (%RH) (%RH) (%RH) (%RH) (%RH) (%RH) Date 778mASL 764mASL 665mASL 638mASL 724mASL 747mASL 783mASL 764mASL 590mASL 660mASL 640mASL 834mASL 688mASL 658mASL Nov-2016 97.6 96.2 89.0 96.2 92.5 95.3 100.2 95.9 98.6 95.9 99.5 97.9 98.8 96.2 Dec-2016 96.8 96.5 86.3 94.9 91.3 94.7 100.1 95.7 98.3 98.1 98.2 96.6 99.3 97.0 Jan-2017 90.8 95.2 84.5 93.5 84.1 90.0 96.4 90.5 94.9 96.8 94.8 92.5 96.3 93.4 Feb-2017 97.0 98.0 82.9 97.9 92.5 93.7 99.5 95.6 99.9 103.5 100.6 97.8 99.7 97.3 Mar-2017 99.0 100.5 69.5 99.9 96.2 96.1 100.6 98.2 100.1 105.8 101.9 100.4 101.3 93.7 Apr-2017 97.1 99.4 59.4 100.4 95.4 90.9 96.5 95.2 97.1 101.3 98.9 99.2 100.2 91.7 May-2017 94.3 98.9 61.0 100.1 93.5 85.0 93.3 95.1 98.9 103.2 97.3 97.6 99.5 93.8 Jun-2017 99.4 101.2 74.5 106.8 99.1 85.6 99.2 102.6 103.9 113.3 101.5 103.2 105.7 99.0 Jul-2017 98.0 100.8 72.9 108.5 98.0 84.2 98.0 102.4 109.0 113.1 102.7 93.9 109.7 100.3 Aug-2017 98.5 100.1 70.0 102.7 97.6 85.9 100.7 99.5 108.3 108.6 98.5 96.5 108.4 98.0 Sep-2017 100.4 99.5 81.3 105.5 99.5 86.6 102.5 101.8 109.1 111.2 99.9 91.6 110.7 99.1 Oct-2017 102.6 102.1 87.0 106.1 101.4 88.9 105.5 101.9 110.6 113.7 103.1 99.7 110.3 101.8 Nov-2017 97.3 96.6 81.0 97.8 92.3 86.6 100.9 96.6 107.4 103.3 98.6 105.6 103.8 98.4 Dec-2017 95.8 82.5 98.6 90.3 86.4 99.7 93.7 106.5 101.5 98.8 104.7 105.4 98.6 Jan-2018 99.5 87.2 100.8 95.6 88.9 101.8 98.2 101.9 105.7 101.3 109.4 112.5 100.9 Feb-2018 97.4 85.9 98.7 90.0 85.9 98.8 93.0 95.7 102.7 98.3 103.5 106.9 96.3 Mar-2018 102.7 94.2 87.5 99.8 96.4 86.0 106.5 101.4 105.4 108.4 Apr-2018 104.6 98.1 90.9 101.8 100.5 74.7 108.8 103.8 108.6 111.9 May-2018 102.8 98.4 91.3 101.1 103.5 69.7 107.3 100.9 108.2 110.0

Min 90.8 95.2 59.4 93.5 84.1 84.2 93.3 90.5 69.7 95.9 94.8 91.6 96.3 91.7 Max 102.6 102.1 89.0 108.5 101.4 96.1 105.5 103.5 110.6 113.7 103.8 109.4 112.5 101.8 Average 97.6 98.9 78.4 101.0 94.7 89.2 99.8 97.7 98.5 105.3 100.0 100.7 105.2 97.2 95%ile 93.4 95.8 60.6 94.8 89.4 85.0 96.1 92.8 74.2 96.7 97.0 92.4 98.5 93.0

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Figure 39: iButton Temperature and Humidity

Peaks Annual Temperature and Humidity 2016 to 2018 120.0 22.0

21.0 110.0

20.0

100.0 19.0

18.0 90.0

17.0

80.0 16.0 Temperature (DegC) Temperature Relative Humidity (%) Humidity Relative

15.0 70.0

14.0

60.0 13.0

50.0 12.0 Jul-2017 Jan-2017 Jan-2018 Apr-2017 Jun-2017 Oct-2017 Apr-2018 Dec-2016 Feb-2017 Aug-2017 Sep-2017 Dec-2017 Feb-2018 Nov-2016 Mar-2017 Nov-2017 Mar-2018 May-2017 May-2018 Date

IB01WG Humidity (%RH) 778mASL IB02WG Humidity (%RH) 764mASL IB03WG Humidity (%RH) 665mASL IB04WG Humidity (%RH) 638mASL IB01PG Humidity (%RH) 724mASL IB02PG Humidity (%RH) 747mASL IB01GVG Humidity (%RH) 783mASL IB02GVG Humidity (%RH) 764mASL IB03GVG Humidity (%RH) 590mASL IB04GVG Humidity (%RH) 660mASL IB05GVG Humidity (%RH) 640mASL IB01DP Humidity (%RH) 834mASL IB01BG Humidity (%RH) 688mASL IB02BG Humidity (%RH) 658mASL IB01WG Temperature (DegC) 778mASL IB02WG Temperature (DegC) 764mASL IB03WG Temperature (DegC) 665mASL IB04WG Temperature (DegC) 638mASL IB01PG Temperature (DegC) 724mASL IB02PG Temperature (DegC) 747mASL IB01GVG Temperature (DegC) 783mASL IB02GVG Temperature (DegC) 764mASL IB03GVG Temperature (DegC) 590mASL IB04GVG Temperature (DegC) 660mASL IB05GVG Temperature (DegC) 640mASL IB01DP Temperature (DegC) 834mASL IB01BG Temperature (DegC) 688mASL IB02BG Temperature (DegC) 658mASL

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Figure 40: Temperature Isohyet 2016 to 2017

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Figure 41: Humidity Isohyet 2016 to 2017

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Figure 42: Average 24h Temperature and Humidity

Peaks Average 24h Temperature and Humidity October 2016 to May 2018 120 28

26 110

24

100 22

90 20 Humidity (%RH) Humidity

18 (DegC) Temperature 80

16

70 14

60 12 00:00:00 01:00:00 02:00:00 03:00:00 04:00:00 05:00:00 06:00:00 07:00:00 08:00:00 09:00:00 10:00:00 11:00:00 12:00:00 13:00:00 14:00:00 15:00:00 16:00:00 17:00:00 18:00:00 19:00:00 20:00:00 21:00:00 22:00:00 23:00:00 Time

IB01WG Humidity (%RH) 778mASL IB02WG Humidity (%RH) 764mASL IB03WG Humidity (%RH) 665mASL IB04WG Humidity (%RH) 638mASL IB01PG Humidity (%RH) 724mASL IB02PG Humidity (%RH) 747mASL IB01GVG Humidity (%RH) 792mASL IB02GVG Humidity (%RH) 764mASL IB03GVG Humidity (%RH) 590mASL IB04GVG Humidity (%RH) 660mASL IB05GVG Humidity (%RH) 640mASL IB01DP Humidity (%RH) 834mASL IB01BG Humidity (%RH) 688mASL IB02BG Humidity (%RH) 658mASL IB01WG Temperature (DegC) 778mASL IB02WG Temperature (DegC) 764mASL IB03WG Temperature (DegC) 665mASL IB04WG Temperature (DegC) 638mASL IB01PG Temperature (DegC) 724mASL IB02PG Temperature (DegC) 747mASL IB01GVG Temperature (DegC) 792mASL IB02GVG Temperature (DegC) 764mASL IB03GVG Temperature (DegC) 590mASL IB04GVG Temperature (DegC) 660mASL IB05GVG Temperature (DegC) 640mASL IB01DP Temperature (DegC) 834mASL IB01BG Temperature (DegC) 688mASL IB02BG Temperature (DegC) 658mASL

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The annual average data indicate that average monthly temperatures vary 1.5oC across all monitoring locations within the study area. Temperatures generally increase with a decrease in elevation. Average monthly humidity varied by 27%RH between monitoring locations. The variability in temperature in each sub-catchment averaged 1.3oC in Grapevine Gut and 0.6oC in Wells Gut. The variability in relative humidity in each sub-catchment averaged 9.1%RH in Grapevine Gut and 25%RH in Wells Gut.

The diurnal and inverse relationship between temperature and relative humidity within the Peaks is illustrated in Figure 42. Temperature increases during daylight hours to reach its maximum between 12:00 and 14:00 and falls to its minimum between 03:00 and 05:00. Humidity increases during early evening to reach its maximum between 03:00 and 06:00 and falls to its minimum between 12:00 and 14:00.

The notable exception is the humidity on Diana’s Peak which reaches its maximum at 20:00 in the evening (104.4%RH). This consistently high humidity can also be attributed to the elevation of Diana’s Peak as the highest point on the island.

Seasonally temperature ranged between 13.8oC and 19.5oC (16.1oC average) in winter (April to September) and 13.8oC and 20.4oC (16.5oC average) in summer (October to March). During these periods, humidity ranged 54.95 and 113% in winter (97% average) and 81% and 113 % in summer (98% average). The data indicate that there is no seasonal variation in average temperature and humidity.

Wind speed, topography and habitat influence humidity. Recorded wind speeds are broadly similar in Grapevine Gut and Wells Gut and the vegetation survey reported that Wells Gut has a higher proportion of endemic and native plants than Grapevine Gut. Differences in temperature and humidity in the sub-catchments are likely to be influenced by plant morphology, the proportion of plant species in each Gut and differences in the orientation, topography and wind speed in each Gut. Theses micro-climate differences will affect plant photosynthesis, transpiration (high humidity reduces evapotranspiration), germination and mortality alongside soil type, decomposition and soil nutrients.

The 18-month temperature and humidity data set indicate that there are differences in micro-climate between each Gut. These differences could be promoting growth or mortality of different plant species and influencing the success or failure of invasive and endemic plants within the study area. More detailed microclimate studies would be needed to confirm the key influences on micro-climate and plant growth within each sub-catchment. However, the continued restoration of the Peaks NCA and study area will play a part in modifying the micro-climate and soil conditions over time by re- introducing plant species that naturally habit St Helena’s montane cloud forest.

14.3 Barometric Pressure

The pressure at any height in the atmosphere is the total weight of the air above a unit area at any elevation. At higher elevations, there are fewer air molecules above a given surface than a similar surface at lower levels. As a consequence, pressure decreases with increasing altitude. This relationship has been used to correct incomplete barometric pressure data sets collected in the Peaks NCA, using a complete record from the Bottom Woods Met Station.

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Barometric pressure (recorded in millibars) has been collected at each weather station and also in Wells Gut and Grapevine Gut using Diver pressure transducers. As well as being used to assess general climate conditions, barometric pressure data can be used to correct water pressure data (expressed as cmH2O), which is used to measure the depth of water in a borehole (groundwater) or in a stream or river.

During the review of ANRD climate data, it was confirmed that ANRD do not collect atmospheric pressure data. As a consequence, the longest barometric pressure record for the island is recorded at Bottom Woods Met Station (436mASL), which is reviewed here for the period October 2016 to May 2018. As in other datasets the atmospheric pressure data record for the DPLUS051 weather stations and pressure transducers is not complete (see Section 13).

Data for BP01WG has gaps due to logger memory full on 8th July 2017 and was re-started on 8th November 2017. The longest continuous record of barometric pressure at BP01WG was 8 months (November 2016 to July 2017). Data for BP01GVG has gaps as the logger memory was full on 8th July 2017 and was re-started on 9th November 2017. The longest continuous record of barometric pressure at BP01GVG was 7 months (November 2017 to May 2018).

Barometric pressure data recorded within the Peaks NCA and at Bottom Woods Met station are presented in Figure 43. It is clear that the sensor BP01GVG was not functioning correctly due to the large variation in pressure when compared against other data sets. The sensor at WS02GVG was also failing when recording late data from June 2017 onwards.

The data gaps in the pressure data at BP01WG and BP01GVG have been filled by a trend analysis of barometric pressure data collected at the Bottom Woods weather station operated by the UK Met Office. Before creating a hind cast and forecast data set for gaps in the BP01WG and BP01GVG, the relationship between barometric pressure recorded at these monitoring locations was tested against data collected at Bottom Woods Met Station using Pearson’s Product Moment Correlation Coefficient (known as Pearson’s R).

The Pearson’s R method is used to measure how strong a relationship is between two variables, commonly used in linear regression.

• A correlation coefficient of 1 means that for every positive increase in one variable, there is a positive increase of a fixed proportion in the other. • A correlation coefficient of -1 means that for every positive increase in one variable, there is a negative decrease of a fixed proportion in the other. • Zero means that for every increase, there isn’t a positive or negative increase. The two just aren’t related.

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Figure 43: Barometric Pressure Data

DPLUS051 Barometric Pressure with Elevation 1000

990 BP01GVG sensor drift 980

970

960

950

940

Barometric Pressure (mbar) Pressure Barometric 930

920 WS02GVG sensor failing 910

900 24/10/2016 07/11/2016 21/11/2016 05/12/2016 19/12/2016 02/01/2017 16/01/2017 30/01/2017 13/02/2017 27/02/2017 13/03/2017 27/03/2017 10/04/2017 24/04/2017 08/05/2017 22/05/2017 05/06/2017 19/06/2017 03/07/2017 17/07/2017 31/07/2017 14/08/2017 28/08/2017 11/09/2017 25/09/2017 09/10/2017 23/10/2017 06/11/2017 20/11/2017 04/12/2017 18/12/2017 01/01/2018 15/01/2018 29/01/2018 12/02/2018 26/02/2018 12/03/2018 26/03/2018 09/04/2018 23/04/2018 07/05/2018 21/05/2018 04/06/2018 18/06/2018 Time

BP01WG 680mASL (mbar) WS03WG 770mASL (mbar) BP01GVG 640mASL (mbar) WS02GVG 780mASL (mbar) WS01PG 750mASL (mbar) Bottom Woods Met Station 436mASL (mbar)

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Figure 44: Pearson’s R - BP01WG and Bottom Woods Met Station

Pearson's Product Moment Correlation Coefficient BP01WG vs Bottom Woods Met Station - 31/10/16 to 08/07/17

972

971

R² = 0.9361 970

969

968

680mASL 967

966 BP01WG Marometric Pressure (mbar) Pressure Marometric BP01WG

965

964

963

962 938 939 940 941 942 943 944 945 946 947 948

Bottom Woods Met Station Barometric Pressure (mbar) 436mASL

Figure 45: Pearson's R - WS02GVG and Bottom Woods Met Station

Pearson's Product Moment Correlation Coefficient WS02GVG vs Bottom Woods Met Station - 26/10/16 to 02/06/17

971

R² = 0.8957

970

969

968

967 780mASL 966

965 WS02GVGG Marometric Pressure (mbar) Pressure Marometric WS02GVGG

964

963

962 925 926 927 928 929 930 931 932 933 934 Bottom Woods Met Station Barometric Pressure (mbar) 436mASL

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Figure 46: Pearson's R - BP01GVG and Bottom Woods Met Station

Pearson's Product Moment Correlation Coefficient BP01GVG vs Bottom Woods Met Station - 11/11/17 to 22/05/18

969

968 R² = 0.1673

967

966

590mASL 965

964 BP01GVGG Marometric Pressure (mbar) Pressure Marometric BP01GVGG

963

962

961 935 940 945 950 955 960 965 970

Bottom Woods Met Station Barometric Pressure (mbar) 436mASL

The best-fit barometric data were recorded at BP01WG located next to SW02WG in the bottom of Wells Gut and at Grapevine Weather Station. An R value of 0.94 was recorded at BP01WG (Figure 44) and 0.90 at Grapevine Gut (Figure 45). Calculation of Pearson’s R for BP01GVG indicated that there was no relation between change in barometric pressure between BP01GVG and the Bottom Woods Met Station (Figure 46), confirming that the sensor was not operating correctly.

Barometric data was hind cast and forecast where data was missing in the record for BP01WG and WS01WG by calculating the change in pressure for every 1m change in elevation between the two pairs of monitoring locations (with Bottom Woods Met Station being the second of each pair).

The hind cast and forecast barometric pressure data sets are presented in Figure 47.

The change in pressure was calculated as 0.10 mbar/m for BP01WG and 0.11 mbar/m for WS02GVG. Rainfall data for Grapevine Gut are also presented in Figure 47, as recorded barometric pressure for 6th and 9th July fluctuates by 30 mbar. Looking at the data set, the change in pressure cannot be attributed to a climate event, but also cannot be attributed to sensor malfunction as actual later data corresponds to forecast data. The cause of this pressure fluctuation is unknown.

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Figure 47: Hind Cast and Forecast Barometric Pressure

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14.4 Rainfall and Mist

Rainfall has been recorded in the Peaks by the weather stations and also by Hobo rain gauge data loggers. Mist has been recorded using Hobo rain gauge data loggers installed within hybrid Juvik-type wire harp collectors supplied by CEH (Section 5.2).

Monthly mist data is presented in Table 15 and Figure 48. Monthly rainfall data is presented in Table 16 and Figure 49.

MC01PG didn’t record mist as rainfall between October 2016 and February 2017. It is thought that this gap in recorded mist is not due to any malfunction of the data logger, but a reflection of the data logger’s elevation (729mASL) and surrounding topography. The island experienced a drought during the time of the monitoring equipment installation which may also contribute to the lack of rainfall and mist in the early summer on island.

MC02PG has a data gap between 25th January and 29th March 2017. The cause of the data loss could not be identified from logger diagnostics or field notes for data downloads within this period.

MC01DP has no data between April 2017 and October 2017 due to problems with the Hobo rain gauge data logger. The Hobo data logger was removed from site in June 2017 for repair. The data record between 31st March 2017 and June 2017 was lost due to the malfunction of the data logger. Despite attempts to fix the logger, it was abandoned and replaced with the Hobo rain gauge data logger from MC01PG. The substitution was made as the principal aim of the project was to evaluate the microclimate in Wells Gut and Perkins Gut and derive a water balance for each sub-catchment. The mist capture equipment on Diana’s Peak provides an indication of the potential mist contribution to the water balance in Wells Gut. The top of the Wells Gut catchment is on the north east facing slopes of Diana’s Peak.

The lowest elevation logger (MC01PG, 729mASL) located on the windwards (south east) side of the Peaks in Perkins Gut did not report any mist as rainfall between October 2016 and January 2017, whereas the second lowest elevation mist logger (MC02PG, 752mASL) reported mist as rainfall between November 2016 and January 2017. On the leeward side of the Peaks (north west) all Hobo mist loggers reported mist between October 2016 and January 2017, including MC02WG which is located at 692mASL and was installed at the lowest elevation of all mist loggers in the study area. All loggers reported mist for the remainder of the monitoring period between February and October 2017.

The longest set of mist data was recorded at MC01WG (763mASL), with a total recorded mist of 2,836mm in 2017. Note: the logger stopped recording in October 2017, consequently the total mist recorded is for a 11-month period. By averaging the previous 7 months mist data for October 2017, total mist for the 12-month period is 3,090mm.

The longest set of rainfall data was recorded at WS02GVG/RF01GVG (783mASL), with a total recorded rainfall of 2,048mm for 2017.

The difference in elevation between MC01WG and WS02GVG/RF01GVG is 20m, with both located the leeward side of the Peaks. For 2017, total mist and rain was 5,138mm with mist comprising 60% total mist and rain.

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Table 15: Monthly Mist Data

Perkins Gut Mist (MC01PG) 729mASL Dianas Peak Mist (MC01DP) 834 mASL Wells Gut Mist (MC01WG) 763 mASL Monthly Mist (mm) Monthly Mist (mm) Monthly Mist (mm)

Year Year Month Year Month Month 2016 2017 2016 2017 2018 2016 2017 2018 January 0.00 January 174.90 377.08 January 120.78 330.22 February 91.52 February 768.24 139.48 February 647.24 81.18 March 517.44 March 821.48 301.84 March 692.12 98.78 April 131.56 April 467.72 April 126.50 139.04 May 163.02 May 154.22 May 143.00 41.58 June 305.36 June June 288.64 July 269.28 July July 222.42 August 121.44 August August 125.84 September 106.04 September September 176.44 October 0.00 October 126.94 October November 0.00 November 407.66 175.56 November 428.78 109.78 December 0.00 December 389.18 194.26 December 356.18 183.70

Total Annual Mist (mm) 0.00 1705.66 Total Annual Mist (mm) 923.78 2134.44 1440.34 Total Annual Mist (mm) 784.96 2836.46 690.80 Mean Monthly Mist (mm) 0.00 189.52 Mean Monthly Mist (mm) 307.93 426.89 288.07 Mean Monthly Mist (mm) 392.48 257.86 138.16 Maximum Monthly Mist (mm) 0.00 517.44 Maximum Monthly Mist (mm) 407.66 821.48 467.72 Maximum Monthly Mist (mm) 428.78 692.12 330.22 Minimum Monthly Mist (mm) 0.00 0.00 Minimum Monthly Mist (mm) 126.94 174.90 139.48 Minimum Monthly Mist (mm) 356.18 109.78 41.58 Median Annual Mist (mm) 0.00 131.56 Median Annual Mist (mm) 389.18 194.26 301.84 Median Annual Mist (mm) 392.48 176.44 98.78

Perkins Gut Mist (MC02PG) 752 mASL Wells Gut Mist (MC02WG) 764 mASL Monthly Mist (mm) Monthly Mist (mm)

Year Month Year Month 2016 2017 2016 2017 2018 January 32.12 January 22.88 February 0.00 February 110.44 March 9.90 March 116.16 April 79.86 April 63.14 May 159.94 May 98.34 June 291.28 June 135.30 July 251.02 July 45.10 August 130.90 August 119.46 September 202.40 September 33.00 October 331.98 October 24.86 12.10 November 67.54 November 105.60 December 29.04 December 61.16

Total Annual Mist (mm) 96.58 1489.40 Total Annual Mist (mm) 191.62 755.92 Mean Monthly Mist (mm) 48.29 148.94 Mean Monthly Mist (mm) 63.87 75.59 Maximum Monthly Mist (mm) 67.54 331.98 Maximum Monthly Mist (mm) 105.60 135.30 Minimum Monthly Mist (mm) 29.04 0.00 Minimum Monthly Mist (mm) 24.86 12.10 Median Annual Mist (mm) 48.29 145.42 Median Annual Mist (mm) 61.16 80.74

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Table 16: Monthly Rainfall Data

Perkins Gut Weather Station (WS01PG) Grapevine Gut Weather Station (WS02GVG and RF01GVG) Wells Gut Weather Station (WS02WG and RF01WG) Monthly Rainfall (mm) Monthly Rainfall (mm) Monthly Rainfall (mm)

Year Year Year Month Month Month 2016 2017 2016 2017 2018 2017 2018 January 56.40 January 99.79 130.24 January 72.60 February 31.60 February 66.92 37.18 February 9.46 March March 488.86 115.50 March 324.00 186.56 April April 373.43 40.92 April 362.60 116.38 May May 114.25 78.54 May 387.40 June June 140.18 June 98.80 July July 268.88 July 28.00 August August 117.02 August 34.00 September September 210.67 September October October 14.26 67.91 October November 7.60 November 135.04 26.84 November 15.18 December 73.80 December 99.79 74.14 December 40.92

Total Annual Rainfall (mm) 81.40 88.00 Total Annual Rainfall (mm) 249.08 2048.90 402.38 Total Annual Rainfall (mm) 1290.90 385.00 Mean Monthly Rainfall (mm) 40.70 44.00 Mean Monthly Rainfall (mm) 83.03 170.74 80.48 Mean Monthly Rainfall (mm) 161.36 96.25 Maximum Monthly Rainfall (mm) 73.80 56.40 Maximum Monthly Rainfall (mm) 135.04 488.86 130.24 Maximum Monthly Rainfall (mm) 387.40 186.56 Minimum Monthly Rainfall (mm) 7.60 31.60 Minimum Monthly Rainfall (mm) 14.26 26.84 37.18 Minimum Monthly Rainfall (mm) 15.18 9.46 Median Annual Rainfall (mm) 40.70 44.00 Median Annual Rainfall (mm) 99.79 115.63 78.54 Median Annual Rainfall (mm) 69.86 94.49

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Figure 48: Monthly Mist 2016 to 2018

Monthly Mist 2016 to 2018 900

800

700

600

500

Mist (mm) 400

300

200

100

0 01/11/2016 01/12/2016 01/01/2017 01/02/2017 01/03/2017 01/04/2017 01/05/2017 01/06/2017 01/07/2017 01/08/2017 01/09/2017 01/10/2017 01/11/2017 01/12/2017 01/01/2018 01/02/2018 01/03/2018 01/04/2018 Date

MC01PG Mist (mm) 724 mASL MC02PG Mist (mm) 752 mASL MC01WG Mist (mm) 778 mASL MC02WG Mist (mm) 764 mASL MC01DP Mist (mm) 834 mASL

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Figure 49: Monthly Rainfall 2016 to 2018

Monthly Rainfall 2016 to 2018 600

500

400

300 Rainfall (mm)

200

100

0 01/11/2016 01/12/2016 01/01/2017 01/02/2017 01/03/2017 01/04/2017 01/05/2017 01/06/2017 01/07/2017 01/08/2017 01/09/2017 01/10/2017 01/11/2017 01/12/2017 01/01/2018 01/02/2018 01/03/2018 01/04/2018 Date WS01PG Rainfall (mm) 752 mASL WS02GVG and RF01GVG Rainfall (mm) 783 mASL WS03WG and RF01WG Rainfall (mm) 763 mASL Peaks Nursery Rainfall (mm) 724 mASL Bottom Woods Met Station Rainfall (mm) 436 mASL

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Figure 50: Wells Gut Monthly Rainfall and Mist

Wells Gut Monthly Rainfall and Mist (mm) November 2016 to May 2018 800

700

600

500

400

300 Monthly Rainfall and Mist (mm) Monthly 200

100

0 01/11/2016 01/12/2016 01/01/2017 01/02/2017 01/03/2017 01/04/2017 01/05/2017 01/06/2017 01/07/2017 01/08/2017 01/09/2017 01/10/2017 01/11/2017 01/12/2017 01/01/2018 01/02/2018 01/03/2018 01/04/2018 01/05/2018 Date

MC01WG Mist (mm) WS03WG and RF01WG Rainfall (mm) Grapevine Gut WS02 and RF01GVG Rainfall (mm)

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Figure 48 mist data indicates that when loggers were functioning, the highest recorded mist was at Diana’s Peak (821mm in March 2017).

When compared to the rainfall record from Bottom Woods Met Station, total rainfall in Grapevine Gut (2,048mm) is 3.9 times higher than recorded at Bottom Woods (583.5mm) in 2017 and Peaks Nursery rainfall is 2.3 times higher (1,354mm) than Bottom Woods for the same period. Rainfall recorded at Grapevine Gut is 1.5 times higher than recorded at the Peaks Nursery in 2017 (Figure 49).

Mist and rainfall data have been collected for the longest period of time in one location at WS03WG/RF01WG and MC01WG. The rainfall and mist record are presented in Figure 50, which also compares mist with rainfall collected in Grapevine Gut (WS02GVG/RF01GVG). Due to the incomplete rainfall record in Wells Gut, mist and rainfall have been reviewed in two parts. Between March and October 2017, recorded mist in Wells Gut (1,598mm) was 1.3 times greater than rainfall (1,234mm). Between December 2017 and April 2018, recorded mist (943mm) in Wells Gut was 2.1 times greater than rainfall (441mm). The longest and most reliable rainfall record in the Peaks is at WS02GVG/RF01GVG. Comparison with the longest mist record in Wells Gut (MC01WG) indicates that for a 12-month period between March 2017 and February 2018, mist in Wells Gut (2,733mm) is 1.3 times greater than rainfall in Grapevine Gut (2,050mm). This period includes the unusually wet March 2017.

A summary of long-term mist and rainfall rain/mist days for WS02GVG/RF01GVG and MC01WG is presented in Table 17.

Table 17: Long Term Mist and Rainfall

Rainfall and Mist Rainfall Mist

WS02GVG/RF01GVG MC01WG

Monitoring Days 491 523

Total Rain/Mist Days 389 427

Total Dry Days 102 96

% Rain/Mist Days 79% 82%

% Dry Days 21% 18%

The data suggest that amounts of and rain are related as the proportion of mist days and rain days are very similar for the long-term records in both Wells Gut and Grapevine Gut.

The question then is whether rainfall measurements can be used as an indicator of mist given that this is the most often measured variable. The Pearson’s R method described in Section 0 has been used to quantify this relationship in Table 18.

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Table 18: Pearson's R - Rainfall and Mist

Rainfall and Mist Monitoring Monitoring Period Pearson’s R Correlation Locations

MC01DP and RF01GVG 23/11/17 to 18/05/18 0.49 Weak positive linear relationship.

MC01DP and RF01WG 23/11/17 to 16/04/18 0.72 Strong positive linear relationship.

MC01WG and RF01GVG 31/10/16 to 18/05/18 0.63 Moderate positive linear (WS02GVG) relationship.

MC01WG and RF01WG 23/11/17 to 16/04/18 0.26 No linear relationship

The rainfall and mist data show varying degrees of correlation, with the strongest correlation between mist data from Diana’s Peak (MC01DP) and rainfall data from Wells Gut (RF01WG) shown in Figure 51. The reasons for this stronger relationship are uncertain, as the distance or elevation between monitoring locations do not appear to be factors e.g. MC01WG and RF01WG (no linear relationship) are located within 1m of each other and MC01DP and RF01WG are 136m apart with an elevation difference of 71m. However, the weakness of the relationship appears to be influenced by the fact that it is much weaker when there are lower values little rain or mist i.e. the cluster of points nearer the origin of the axes Figure 51. Whether the relationship remains stronger for larger values of rainfall and mist would need additional data to determine.

Figure 52 shows the relationship between average mist and elevation in a SE to NW transect across the Peaks between November 2016 and January 2017. The mist recorded during this time indicates that rainfall and mist increase with an increase in elevation. A longer data set would assist in the validation of this relationship; however, equipment failures prevented the collection of a long continuous mist record in each monitoring location for the same period of time.

14.5 Soil Moisture

The Centre for Ecology and Hydrology kindly donated four Madgtech SMR101A soil moisture data loggers. The loggers were installed in four locations shown in Figure 34. Two were placed within the fern thicket on the top of Diana’s Peak (SM01WG) and adjacent to the Grapevine Gut weather station (SM01GVG). The other two loggers were located within flax in Grapevine Gut (SM02GVG) and Wells Gut (SMO2WG).

During the data collection phase of the project, the flax soil moisture logger (SM02GVG) in Grapevine Gut and fern thicket soil moisture logger on Diana’s Peak (MC01WG) developed a fault which the project team were unable to repair. Internal batteries were replaced in all loggers during November 2017. Soil moisture content for a stand of flax (SM01WG) and fern thicket (SM01GVG) are presented in Figure 53.

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Figure 51: Pearson's R - MC01DP and RF01WG

Pearson's Product Moment Correlation Coefficient MC01DP Mist vs RF01WG Rainfall (23/11/17 to 16/04/18)

40

35

30

R² = 0.7169 25

RF01WG Rainfall (mm) RF01WG 20

15

10

5

0 0 10 20 30 40 50 60 70 80

MC01DP Mist (mm)

Soil moisture beneath the flax averaged 84% between November 2016 and May 2018, with soil moisture in the tree fern thicket averaging 70% for the same period. Soil moisture ranged between 76% and 89% beneath the flax and between 48% and 107% beneath the tree fern thicket. Soil moisture beneath the flax maintained a more constant saturation throughout the monitoring period, whereas soil moisture between the fern thicket varied greatly.

Average monthly soil moisture has been plotted against average monthly temperature in Figure 54. Soil moisture beneath the tree fern thicket can be seen to increase when air temperatures decreases and vice versa, whilst beneath the flax air temperature does not markedly influence soil moisture.

Based on the available data, soil moisture may be more constant over time beneath the flax due to the large area of shading that flax fronds give to the underlying soil. Conversely, soil beneath the tree fern thicket is likely to be more exposed as the delicate fronds allow more light and wind beneath the canopy increasing evaporation losses from the soil. However, these data indicate that habitat responses can be different when exposed to similar climatic conditions. Hypothetically, this may mean that the tree fern thicket allows for more storage and release of water to the catchment than the flax habitat. This may be particularly true when there are larger rainfall events where the flax may be more likely to let water run off quickly showing a more flashy response. In contrast, the tree fern thickets are capable of water uptake and then a slower release over a longer period. A longer-term data set would be required to confirm if this relationship truly exists.

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Figure 52: Mist and Elevation

Average Mist as Rainfall (mm) with Change in Elevation November 2016 to January 2017 350

300

250

200

150 Mist as Rainfall (mm) 100

50

0 752 834 778 764 Elevation (mASL)

Average Mist as Rainfall (mm)

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Figure 53: Soil Moisture

DPLUS051 Soil Moisture 120

100

80

60 Soil Moisture (%RH) Soil Moisture

40

20

0 28/10/2016 11/11/2016 25/11/2016 09/12/2016 23/12/2016 06/01/2017 20/01/2017 03/02/2017 17/02/2017 03/03/2017 17/03/2017 31/03/2017 14/04/2017 28/04/2017 12/05/2017 26/05/2017 09/06/2017 23/06/2017 07/07/2017 21/07/2017 04/08/2017 18/08/2017 01/09/2017 15/09/2017 29/09/2017 13/10/2017 27/10/2017 10/11/2017 24/11/2017 08/12/2017 22/12/2017 05/01/2018 19/01/2018 02/02/2018 16/02/2018 02/03/2018 16/03/2018 30/03/2018 13/04/2018 27/04/2018 11/05/2018 Date

SM01GVG Fern Thicket Soil Moisture (%RH) SM01WG Flax Soil Moisture (%RH)

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Figure 54: Monthly Average Soil Moisture and Air Temperature

DPLUS051 Average Monthly Soil Moisture and Temperature 120 25.00

100 20.00

80

15.00 C) o

60

10.00 ( Temperature Soil Moisture (%RH) Soil Moisture

40

5.00 20

0 0.00 01/10/2016 15/10/2016 29/10/2016 12/11/2016 26/11/2016 10/12/2016 24/12/2016 07/01/2017 21/01/2017 04/02/2017 18/02/2017 04/03/2017 18/03/2017 01/04/2017 15/04/2017 29/04/2017 13/05/2017 27/05/2017 10/06/2017 24/06/2017 08/07/2017 22/07/2017 05/08/2017 19/08/2017 02/09/2017 16/09/2017 30/09/2017 14/10/2017 28/10/2017 11/11/2017 25/11/2017 09/12/2017 23/12/2017 06/01/2018 20/01/2018 03/02/2018 17/02/2018 03/03/2018 17/03/2018 31/03/2018 14/04/2018 28/04/2018 Date

SM01GVG Fern Thicket Soil Moisture (%) SM01WG Flax Soil Moisture (%) Average Temperature (oC)

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14.6 Surface Water

Surface water levels were measured using Level Scout and Diver pressure transducers between October 2016 and November 2017. The interpretation of surface water flows has used data collected during this period. Stream flow in Grapevine Gut (SW01GVG) continued to be collected using a Blue Siren ultrasonic flow logger until May 2018. Water levels were also monitored until early June 2018 at SW02GVG as parts of the data set between November 2016 and October 2017 were missing (Section 13.5).

Barometric pressure data (Section 0) was used to correct surface water pressure data from atmospheric pressure. This data was then calibrated against surface water reference levels logged at each catchpit and the Wells Gut V-Notch weir (SW03WG).

Surface water flows into the catchpits were calculated using the Manning equation for calculating steady uniform flow in a channel or pipe:

1 ! = # $ ' ()/+,-/) &

Where:

Q = discharge (m3/s)

A = area (m2)

R = hydraulic radius (m)

S = slope of the channel / pipe h = Manning’s channel / pipe roughness coefficient

(Environment Agency, 2018)

Note: The Manning flow equation is known to under or over estimates flows by between +-10 to +-20%, however variances in measurement can decrease accuracies to +-25 to +-30% because of friction losses, such that when a pipe is full, flow rates will decline compared to a pipe that is 90% full.

The Manning flow equation was used because all the stream flow accumulating in catchpits discharges through distribution pipes which then divert flow to the Hutts Gate water treatment works. Calculated flows are also compared against reservoir rates of fill by Connect for Grapevine Gut reservoir, as all flow from Grapevine Gut appears to be intercepted by the reservoir (see inflow pipes at the upstream end of the reservoir in Plate 20).

Average monthly flows in Grapevine Gut (SW01GVG) have been compared against surface water flows recorded by the Blue Siren ultrasonic flow logger (FL01GVG), which has been used to record pipe flow in the downstream outflow of catchpit SW01GVG between November 2017 and May 2018.

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Note: there are no well-defined stream channels in the Peaks. The Connect catchpits have been constructed to intercept surface water flows/spring flow at strategic points down Wells Gut and near the bottom of Grapevine Gut. It is assumed that this accounts for flow in the sub-catchments and that almost 100% of total flow has been intercepted by the

Catchpits. Therefore, the pipe flow calculated at each catchpit outflow is comparable with stream flow.

Plate 20: Grapevine Gut Reservoir Stream Inflow Pipes

Surface water flows in the Wells Gut v-notch weir have been calculated using the v-notch weir discharge formula published by Shaw (Shaw et al., 2011):

2 ! = ./01 $ ' 4+/) 2

Where:

Q = discharge (m3/s) q = angle of the v-notch

K = coefficient of the weir H = depth of water over the weir

A detailed assessment of stream flow, runoff and climate is provided in Section 14.8.

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14.6.1 Grapevine Gut

Surface water levels recorded in Catchpit 1 (SW01GVG) and Catchpit 2 (SW02GVG) are shown in Figure 55 and Figure 56. The top and bottom of the outflow pipe in each catchpit is shown on each chart, indicating when water levels were high enough in each structure for water to flow out of the structure.

Water flows in Grapevine Gut have been compared against rates of fill in the reservoir into which both SW01GVG and SW02GVG are believed to discharge. Flow data in SW01GVG calculated using water level and pipe flow has also been compared against flow data collected using a Blue Siren ultrasonic flow logger measuring flow within the outfall pipe of the catchpit. Missing data for SW02GVG were hind cast for the months of July to October 2017 using data collected between November 2017 and May 2018.

A summary of surface water flows in Grapevine Gut is presented in Table 19. Monthly stream flows in Grapevine Gut are presented in Figure 57. In Table 20 monthly stream flows are compared against raw water abstraction data from Grapevine Gut reservoir, provided by Connect Saint Helena (Connect Saint Helena, 2018a).

Table 19: Grapevine Gut Surface Water Flows

Monitoring Total Days Maximum Average Total No Location Monitored Recorded Flow Flow (m3/d) Flow Days (m3/d)

SW01GVG 382 14 13 4

FL01GVG 206 70 15 0

SW02GVG 424 9 5 68

Table 19 shows a good fit between average surface water flows in Catchpit 1 (SW01GVG and FL01GVG) calculated using the Manning flow equation and flows measured using the Blue Siren ultrasonic flow meter (Figure 57). The cause of the peak flow measured in December 2017 by FL01GVG is uncertain, as average rainfall of 170mm per month was recorded in Grapevine Gut in 2017, however in December 2017 94mm rainfall was recorded (RF01GVG). The smaller stream at SW02GVG (catchpit 2) has flows over 2 times smaller than the main stream in Grapevine Gut due to its smaller catchment area. The smaller catchment is also drier, with significantly more dry days recorded, despite a gap in the data set.

Comparison of stream flows and raw water abstraction indicate that between November 2016 and October 2017, Grapevine Gut reservoir abstractions were 22% total recorded stream flows. The data indicated that a surplus of 4,619m3 surface water was available for supporting stream flows in the lower part of the Grapevine Gut catchment below the reservoir. A comparison of reservoir rates of fill and stream inflow are presented in Table 21.

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Figure 55: SW01GVG Surface Water Levels

SW01GVG Daily Depth to Water (m) 0.50 0.50

0.45 0.45

0.40 0.40

0.35 0.35

0.30 0.30

0.25 0.25

0.20 0.20 Depthe to Water (m) to Water Depthe

0.15 0.15

0.10 0.10 (m) Top and Bottom of Outflow Pipe

0.05 0.05

0.00 0.00 24/10/2016 07/11/2016 21/11/2016 05/12/2016 19/12/2016 02/01/2017 16/01/2017 30/01/2017 13/02/2017 27/02/2017 13/03/2017 27/03/2017 10/04/2017 24/04/2017 08/05/2017 22/05/2017 05/06/2017 19/06/2017 03/07/2017 17/07/2017 31/07/2017 14/08/2017 28/08/2017 11/09/2017 25/09/2017 09/10/2017 23/10/2017 06/11/2017 Date

SW01GVG Depth to Water (m) Bottom of Outflow Pipe (m) Top of Outflow Pipe (m)

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Figure 56: SW02GVG Surface Water Levels

SW02GVG Daily Depth to Water (m) 0.450 0.45

0.400 0.40

0.350 0.35

0.300 0.30

0.250 0.25

0.200 0.20 Depth to Water (m) to Water Depth 0.150 0.15

0.100 0.10 Top and Bottom of Outflow Pipe (m) Top and Bottom of Outflow Pipe

0.050 0.05

0.000 0.00 31/10/2016 21/11/2016 12/12/2016 02/01/2017 23/01/2017 13/02/2017 06/03/2017 27/03/2017 17/04/2017 08/05/2017 29/05/2017 19/06/2017 10/07/2017 31/07/2017 21/08/2017 11/09/2017 02/10/2017 23/10/2017 13/11/2017 04/12/2017 25/12/2017 15/01/2018 05/02/2018 26/02/2018 19/03/2018 09/04/2018 30/04/2018 21/05/2018 11/06/2018 Date

SW02GVG Depth to Water (m) Bottom of Outflow Pipe (m) Top of Outflow Pipe (m)

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Figure 57: Grapevine Gut Monthly Stream Flow

Grapevine Gut Monthly Stream Flows November 2016 to May 2018 1000

900

800

700 ) 3 600

500

Stream Flow (m Stream 400

300

200

100

0 01/11/2016 01/12/2016 01/01/2017 01/02/2017 01/03/2017 01/04/2017 01/05/2017 01/06/2017 01/07/2017 01/08/2017 01/09/2017 01/10/2017 01/11/2017 01/12/2017 01/01/2018 01/02/2018 01/03/2018 01/04/2018 01/05/2018 Date

SW01GVG & FL01GVG Monthly Stream Flow (m3) SW02GVG Monthly Stream Flow (m3)

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Table 20: Grapevine Gut Stream Flow and Abstraction

SW01GVG SW02GVG Grapevine Gut Date Monthly Stream Monthly Stream Total Flow Raw Water Flow (m3) Flow (m3) (m3) Abstraction (m3) 01/11/2016 390 6 396 242 01/12/2016 407 2 409 23 01/01/2017 358 161 520 12 01/02/2017 304 212 516 265 01/03/2017 345 239 584 212 01/04/2017 399 253 651 51 01/05/2017 428 260 688 60 01/06/2017 394 25 419 140 01/07/2017 384 61 445 218 01/08/2017 405 66 471 18 01/09/2017 380 71 451 70 01/10/2017 341 84 425 45

Total 4,534 1,440 5,975 1,356 Min 304 2 396 12 Max 428 260 688 265 Average 378 120 498 113

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Table 21: Grapevine Gut Stream Flow and Reservoir Rates of Fill

GVG GVG Combined Reduction in Reservoir Reservoir GVG Pumped Date Monthly Reservoir Surplus/Defecit Comment Rate of Fill Raw Water (m3) Stream Flow Volume (m3) (m3) (m3) (m3) Reservoir 51% full at start of November 2016. Rate of fill is 2.4 times greater than 01/11/2016 396 947 936 11 242 stream flow. 01/12/2016 409 763 803 -40 23 Reservoir 53% full at start of December 2016.

01/01/2017 519 729 483 246 12

01/02/2017 516 965 599 366 265 Reservoir at full capacity between 15th February and 2nd March 2017.

01/03/2017 584 639 639 0 212 Reservoir at full capacity between 13th March and 20th April 2017.

01/04/2017 652 275 664 -389 51

01/05/2017 688 1486 1251 235 60 Reservoir at full capacity between 30th May and 8th June 2017.

01/06/2017 419 829 983 -154 140 Reservoir at full capacity between 25th July and 8th August 2017.

01/07/2017 445 1307 1414 -107 218

01/08/2017 471 1342 1342 0 18 Reservoir at full capacity between 7th Sept and 14th Sept and between 21st Sept and 7th 01/09/2017 451 744 744 0 70 Nov 2017. 01/10/2017 425 0 0 0 45 Reservoir at full capacity for whole month of October 2017.

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Connect confirmed that reservoir volume is 1,152 m3 and that inflows and outflows are not measured. Reservoir stage is measured on a daily basis alongside abstraction. As a consequence, reservoir inflows cannot be used as a comparison with calculated stream flow. Rates of fill have been calculated from daily reservoir volume measurements. The review of rates of fill confirm that recorded stream flows, reservoir volumes, rates of fill and pumped raw water do not agree for several months. For all months except April and October 2017, stream flows are less than the reservoir rate of fill. The source of this additional water could be due to under reporting of calculated stream flow (as the Manning equation can under or overestimate flows by +-30%), however the ultrasonic flow measurements agree with the calculated flow measurements at SW01GVG, reducing this uncertainty. Data for November 2016 indicates that rates of fill are 2.4 times greater than stream inflows (assuming all stream flow from Grapevine Gut reaches the reservoir). October 2017 is the only complete month where the reservoir is at 100% capacity, consequently all inflows should be reservoir outflows minus abstraction. Reservoir storage will account for the change in storage in some months when inflows are less than abstraction, but the data are not conclusive.

The review of reservoir data and stream flow data indicate that accurate measurement of reservoir inflows, abstraction and outflows is needed to fully understand the Grapevine Gut water balance. In addition, it is concerning that there appears to be no minimum flow which bypasses the reservoir to provide baseflow to the lower part of the Grapevine Gut catchment. By intercepting all surface water flow, the reservoir could have a detrimental effect on stream flows and habitats downstream of the reservoir.

14.6.2 Wells Gut and Byrons Gut

A summary of surface water flows in Wells Gut and Byrons Gut is presented in Table 22.

Table 22: Wells Gut and Byrons Gut Surface Water Flows

Monitoring Total Days Maximum Average Total No Location Monitored Recorded Flow Flow (m3/d) Flow Days (m3/d)

SW01WG 377 130 92 14

SW02WG 373 204 120 94

SW03WG 373 3,327* 642 9

SW01BG 381 4 3 4

*Maximum flow recorded on 24th February 2017. See Section 14.8.

Surface water levels for all catchpits and weirs are presented in Figure 58, Figure 59, Figure 60 and Figure 61. Stream flows are presented in Figure 62 and compared against abstraction in Table 23.

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Figure 58: SW01WG Surface Water Levels

SW01WG Daily Depth to Water (m) 0.70 0.70

0.60 0.60

0.50 0.50

0.40 0.40

0.30 0.30 Depthe to Water (m) to Water Depthe

0.20 0.20 Top and Bottom of Outflow Pipe (m) Top and Bottom of Outflow Pipe

0.10 0.10

0.00 0.00 28/10/2016 11/11/2016 25/11/2016 09/12/2016 23/12/2016 06/01/2017 20/01/2017 03/02/2017 17/02/2017 03/03/2017 17/03/2017 31/03/2017 14/04/2017 28/04/2017 12/05/2017 26/05/2017 09/06/2017 23/06/2017 07/07/2017 21/07/2017 04/08/2017 18/08/2017 01/09/2017 15/09/2017 29/09/2017 13/10/2017 27/10/2017 Date

SW01WG Depth to Water (m) Bottom of Outflow Pipe (m) Top of Outflow Pipe (m)

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Figure 59: SW02WG Surface Water Levels

SW02WG Daily Depth to Water (m) 0.45 0.45

0.40 0.40

0.35 0.35

0.30 0.30

0.25 0.25

0.20 0.20 Depthe to Water (m) to Water Depthe 0.15 0.15

0.10 0.10 (m) Top and Bottom of Outflow Pipe

0.05 0.05

0.00 0.00 24/10/2016 07/11/2016 21/11/2016 05/12/2016 19/12/2016 02/01/2017 16/01/2017 30/01/2017 13/02/2017 27/02/2017 13/03/2017 27/03/2017 10/04/2017 24/04/2017 08/05/2017 22/05/2017 05/06/2017 19/06/2017 03/07/2017 17/07/2017 31/07/2017 14/08/2017 28/08/2017 11/09/2017 25/09/2017 09/10/2017 23/10/2017 06/11/2017 Date

SW02GVG Depth to Water (m) Bottom of Outflow Pipe (m) Top of Outflow Pipe (m)

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Figure 60: SW03WG Surface Water Levels

SW03WG Daily Depth of Water Above V-Notch Weir (m)

0.50

0.45

0.40

0.35

0.30

0.25

0.20 Depth to Water(m) Depth 0.15

0.10

0.05

0.00 01/11/2016 15/11/2016 29/11/2016 13/12/2016 27/12/2016 10/01/2017 24/01/2017 07/02/2017 21/02/2017 07/03/2017 21/03/2017 04/04/2017 18/04/2017 02/05/2017 16/05/2017 30/05/2017 13/06/2017 27/06/2017 11/07/2017 25/07/2017 08/08/2017 22/08/2017 05/09/2017 19/09/2017 03/10/2017 17/10/2017 31/10/2017

Date

SW03WG Water Depth to Datum (m) Bottom of V-Notch in Weir (m)

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Figure 61: SW01BG Surface Water Levels

SW01BG Daily Depth to Water (m) 0.60 0.60

0.50 0.50

0.40 0.40

0.30 0.30 Depthe to Water (m) to Water Depthe 0.20 0.20 Top and Bottom of Outflow Pipe (m) Top and Bottom of Outflow Pipe 0.10 0.10

0.00 0.00 24/10/2016 07/11/2016 21/11/2016 05/12/2016 19/12/2016 02/01/2017 16/01/2017 30/01/2017 13/02/2017 27/02/2017 13/03/2017 27/03/2017 10/04/2017 24/04/2017 08/05/2017 22/05/2017 05/06/2017 19/06/2017 03/07/2017 17/07/2017 31/07/2017 14/08/2017 28/08/2017 11/09/2017 25/09/2017 09/10/2017 23/10/2017 Date

SW01BG Depth to Water (m) Bottom of Outflow Pipe (m) Top of Outflow Pipe (m)

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Figure 62: Wells Gut and Byrons Gut Monthly Stream Flow

Wells Gut Stream Flow November 2016 to October 2017 30,000

25,000

20,000 ) 3

15,000

10,000 Monthly Stream Flow (m Stream Monthly

5,000

0 01/11/2016 01/12/2016 01/01/2017 01/02/2017 01/03/2017 01/04/2017 01/05/2017 01/06/2017 01/07/2017 01/08/2017 01/09/2017 01/10/2017 Date

SW01WG Monthly Stream Flow (m3) SW02WG Stream Flow (m3) SW03WG Monthly Stream Flow (m3) SW01BG Monthly Stream Flow (m3)

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Table 23: Wells Gut and Byron Gut Stream Flow and Abstraction

SW01WG SW02WG SW03WG SW01BG Upper Wells Gut Lower Wells Gut Combined Wells Date Stream Flow Stream Flow Stream Flow Stream Flow Total Monthly Raw Water Raw Water Gut Raw Water (m3) (m3) (m3) (m3) Flow (m3) Abstraction (m3) Abstraction (m3) Abstraction (m3) 01/11/2016 2,035 3,054 6,853 390 12,333 1,656 2,787 4,443 01/12/2016 2,167 286 24,737 407 27,597 1,400 2,042 3,442 01/01/2017 3,521 2,500 17,669 358 24,049 1,313 434 1,747 01/02/2017 2,464 2,192 18,314 304 23,274 2,324 3,276 5,600 01/03/2017 2,688 4,527 24,528 345 32,088 6,200 5,363 11,563 01/04/2017 2,714 3,269 19,707 399 26,088 3,300 2,970 6,270 01/05/2017 2,994 2,590 10,717 428 16,729 2,852 1,581 4,433 01/06/2017 2,792 2,944 12,566 394 18,696 3,240 2,250 5,490 01/07/2017 2,728 4,506 25,479 384 33,097 4,278 3,782 8,060 01/08/2017 2,728 4,300 27,079 405 34,512 3,689 2,666 6,355 01/09/2017 3,104 2,859 17,868 380 24,210 2,520 1,770 4,290 01/10/2017 2,505 3,623 23,394 341 29,523 2,697 434 3,131

Total 32,442 36,650 228,911 4,534 302,196 35,469 29,356 64,824 Min 2,035 286 6,853 304 12,333 1,313 434 1,747 Max 3,521 4,527 27,079 428 34,512 6,200 5,363 11,563 Average 2,703 3,054 19,076 378 25,183 2,956 2,446 5,402

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Discharge pipes for SW01WG, SW02WG and WS01BG were buried downstream of each catchpit, consequently pipe slope could not be directly measured. To allow calculation of pipe flow, it was assumed that the buried pipes followed the ground contours as the majority of water distribution pipelines are at surface or near surface level of St Helena. The slope of a 10m length of pipe downstream of the catchpit was calculated using QGIS and used in the Manning’s flow calculations for each catchpit. Calculated flows were calibrated against flow data supplied by Connect.

Daily stream flow recorded at the Wells Gut and Byrons Gut intake (assumed to be where the header tanks are located in Wells Gut and Byrons Gut) between 1937 and 1969 (as spot flows) were between 7.9m3/d and 42.4m3/d (Section 9.1), indicating that flows measured between November 2016 and October 2017 at SW01WG, WS02WG and SW01BG are in the same order of magnitude (average 3m3/d to 120m3/d). Flows recorded at the v-notch weir (SW03WG) are 75% of all flows measured within Wells Gut and Byrons Gut.

During the period November 2016 to October 2017, average flows increased downstream between Catchpit 1 (SW01WG) and the weir (WS03WG) in Wells Gut. Flows at the weir (the lowest point in the sub-catchment) accounted for 76% of total flows in Wells Gut. Flows at the bottom of the sub- catchment recorded 9 no flow days, whereas Catchpit 1 and Catchpit 2 in Wells Gut recorded 14 and 94 no flow days respectively.

Flows in Byrons Gut are understood to flow into a header tank for distribution under gravity flow to Hutts Gate water treatment works. Only 4 no flow days were recorded in Byrons Gut, with flows comprising 0.5% average flows at the weir. Total flows in Byrons Gut could not be evaluated as the spring source flows are diverted directly to Hutts Gate water treatment works via a distribution network with no means of measuring flows at the spring source.

The data indicate that stream/spring flows in Wells Gut vary within the Gut but in general increase downstream. The central stream/spring location at Catchpit 2 (SW02WG) was driest for the longest period of time. There is no traditional stream bed within the catchment, so spot flow gauging could not be used to assess gains and losses within the sub-catchment. Flows at the weir are by far the greatest and are due to the weir being located at the bottom of the sub-catchment intercepting all stream/spring flow which is not intercepted by the catchpits.

Table 23 shows stream/spring flows and abstraction in Wells Gut and Byrons Gut. Connect abstract from Upper Wells Gut (Catchpit 2, SW02WG) and Lower Wells Gut (v-notch weir, SW03WG). There are no abstraction data for Byrons Gut. Notwithstanding this, total abstraction from Wells Gut comprises 21% stream/spring flows, indicating that abstraction within the sub-catchment is not detrimental to surface water flows. Flows at the v-notch weir are 76% of total catchment flows.

14.7 Potential Evapotranspiration (PE)

The assessment of water loss from a vegetated land surface by evaporation and plant transpiration

(Evapotranspiration, Et) is more complex than the processes involved in the evaporation from an open water surface (Eo). Instead of adding directly to the body of water, some of the rainfall is intercepted by the vegetation and, from the various wetted surfaces, moisture is returned to the atmosphere by direct evaporation (Shaw et al., 2011).

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In order to calculate a water balance for Wells Gut and Grapevine Gut, evapotranspiration data is required alongside other data sets such as discharge (stream flow) and changes in storage. As there are no recent PE data sets for the island, the Penman-Monteith equation (Shaw et al., 2011) has been used to derive PE using data from Bottom Woods Met Station and the Peaks. The Penman-Monteith equation used is in the form:

∆% + '()*[,-(/0)2,0]/50 !" = ∆ + 6(1 + 89/8()

Where:

H = energy available for evapotranspiration; uz = wind speed at the reference height; d = zero plane displacement; zo = roughness height;

Ta = dry-bulb air temperature at reference height; ea = vapour pressure (using wet-bulb air temperature at reference height); es = saturated vapour pressure at the canopy temperature;

ρa = density of moist air; cp = specific heat of moist air; rc = canopy resistance; rs = (internal stomatal resistance);

:;[(<2=)/<>]? ra = A ; @ BC

5 Ƴ= 6 D1 + - E 50 k = von Karman constant (= 0.41).

(Shaw et al., 2011)

Due to the length of the project weather station data record, the calculation of PE has been limited to the 10-month period between November 2016 and August 2017. Data was collected over 12 months. However, October 2016 and September 2017 were partial months and inclusion of the data would have underestimated PE. Calculated PE with mist and rainfall for the study area are presented in Table 24 and Figure 63.

Previous calculations of PE (Section 4.4) have reported an average of 862mm PE per annum at Hutts over a 22-year period, with average annual rainfall of 1,021mm (PE 84% of rainfall). A total of 1,713 mm PE has been calculated in the for the 10-month monitoring period reported in Table 24. PE for a 12-month period between November 2016 and October 2017 has been calculated as 2,052mm with

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The earlier calculations of PE have only considered rainfall at Hutts Gate, which may explain why PE calculated for the Peaks is 2.3 times greater. PE exceeds combined rainfall and mist for only 1 month during January 2017. If only rainfall is considered, then PE exceeds rainfall 6 out of 10 months.

Table 24: Monthly PE, Rainfall and Mist

Date Monthly PE WS02GVG MC01WG Monthly (mm) Monthly Monthly Rainfall and Rainfall (mm) Mist Mist (mm) (mm) 01/11/2016 176 135 371 506 01/12/2016 194 100 344 444 01/01/2017 222 67 92 159 01/02/2017 189 489 640 1,128 01/03/2017 184 373 675 1,049 01/04/2017 178 114 122 236 01/05/2017 177 140 150 290 01/06/2017 121 269 265 534 01/07/2017 137 117 288 405 01/08/2017 135 211 128 338

Total 1,713 2,015 3,074 5,089 Min 121 67 92 159 Max 222 489 675 1,128 Average 171 202 307 509

14.8 The 2016 to 2017 Drought

Climate and stream flow monitoring started when SHG and Connect Saint Helena declared a drought (Section 4.2) so the data collected here could be considered representative of some months in which drought occurs. The drought ended in February 2017 with a period of very high rainfall, the sixth highest monthly rainfall recorded in the island’s history and the third highest rainfall recorded during February. The data set therefore represents not only an opportunity to assess drought conditions but also how the sub-catchments behaved during a period of high intensity rainfall.

Mist, rainfall, soil moisture and stream levels span for the period between November 2016 to March 2018; November 2016 to January 2017 represents drought months and February to March 2017 represent the high rainfall period. Data for these periods are presented in Figure 64, Figure 65 and Figure 66.

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Figure 63: Monthly PE, Rainfall and Mist

Grapevine Gut Monthly Rainfall, Mist and Potential Evapotranspiration (PE) November 2016 to August 2017 1200 1200

1000 1000

800 800

600 600 Monthly PE (mm) PE Monthly

Monthly Rainfall and Mist (mm) Monthly 400 400

200 200

0 0 01/11/2016 01/12/2016 01/01/2017 01/02/2017 01/03/2017 01/04/2017 01/05/2017 01/06/2017 01/07/2017 01/08/2017 Date WS02GVG Rainfall (mm) MC01WG Mist (mm) Monthly Rainfall and Mist (mm) Monthly PE (mm)

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Figure 64: Surface Water Level and Rainfall (November 2016 to March 2017)

7 Day Moving Average Surface Water Level and Rain November 2016 to March 2017

0.70 45

40 0.60

35 0.50 30

0.40 25

0.30 20 Rainfall (mm) 15

Surface Water Level (m) Level Water Surface 0.20 10

0.10 5

0.00 0 01/11/2016 08/11/2016 15/11/2016 22/11/2016 29/11/2016 06/12/2016 13/12/2016 20/12/2016 27/12/2016 03/01/2017 10/01/2017 17/01/2017 24/01/2017 31/01/2017 07/02/2017 14/02/2017 21/02/2017 28/02/2017 07/03/2017 14/03/2017 21/03/2017 28/03/2017

Date

Grapevine Gut Daily Rainfall (mm) SW01GVG Depth to Water (m) SW02GVG Depth to Water (m) SW01WG Depth to Water (m) SW02WG Depth to Water (m) SW03WG Depth to Water (m) SW01BG Depth to Water (m)

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Figure 65: Surface Water Level, Mist and Rainfall (November 2016 to March 2017)

7 Day Moving Average Surface Water Level and Mist November 2016 to March 2017

0.70 70

0.60 60

0.50 50

0.40 40

0.30 30 Mist as Rainfall (mm)

Surface Water Level (m) Level Water Surface 0.20 20

0.10 10

0.00 0 01/11/2016 08/11/2016 15/11/2016 22/11/2016 29/11/2016 06/12/2016 13/12/2016 20/12/2016 27/12/2016 03/01/2017 10/01/2017 17/01/2017 24/01/2017 31/01/2017 07/02/2017 14/02/2017 21/02/2017 28/02/2017 07/03/2017 14/03/2017 21/03/2017 28/03/2017

Date

SW01GVG Depth to Water (m) SW02GVG Depth to Water (m) SW01WG Depth to Water (m) SW02WG Depth to Water (m) SW03WG Depth to Water (m) SW01BG Depth to Water (m) MC01WG Mist as Daily Rainfall (mm) MC02WG Mist as Daily Rainfall (mm) MC01PG Mist as Daily Rainfall (mm) MC02PG Mist as Daily Rainfall (mm) MC01DP Mist as Daily Rainfall (mm) Grapevine Gut Daily Rainfall (mm)

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Four periods of rainfall were recorded in November 2016, December 2016 and January 2017, with maximum rainfall ranging between 4.98mm and 9.8mm rainfall. Each rainfall event lasted an average of 8 days. The high rainfall event in February (rainfall greater than 10mm per day) started on 13th February 2017 and ended on the 1st March 2017 (17 days) with rainfall averaging 24.56mm, with maximum rainfall of 40.14 mm recorded on 18th February. The highest intensity rainfall was recorded between 13th February and 1st March 2017 (16 days). High rainfall was also recorded from 7th March to the end of the month, with an average daily rainfall of 25.86 mm and maximum rainfall of 27.49mm (16th March).

Stream levels are compared with the rainfall record in Figure 64 and the mist record in Figure 65.

14.8.1 Stream Level Response to Mist and Rainfall

In Wells Gut, stream levels at the top of the sub-catchment (SW01WG) had a clear response to rainfall in early November 2016, with a marked reduction after the second period of rainfall ending on 28th November from which stream levels gradually increased until the end of March 2017. Water levels responded to all rainfall events in February 2017, reaching their highest level in February 3 days after the highest recorded rainfall. Stream levels continued to rise during March 2017, to reach their highest level on 18th March 2017.

Stream levels in the middle of the sub-catchment at SW02WG did not show a marked response to rainfall until 3 days after the rainfall event in December, with water levels rapidly increasing and decreasing by the end of the January 2017 rainfall event. Water levels remained constant in SW02WG until 12th February 2017 when they increased more rapidly reaching their highest level on 2nd March 2017, 13 days after the highest recorded rainfall (18th February).

Surface water levels at the bottom of the sub-catchment at SW03WG responded to all rainfall events, however the response to the early December rainfall was more marked. Surface water levels at the v- notch weir are controlled by the height of the v-notch so maximum water levels at this location correspond to the top of the “V”. Consequently, water level increase during the highest rainfall is not as dramatic as that recorded at SW02WG, however water levels are also shown to reach their highest 3 days after the highest recorded rainfall.

For Grapevine Gut, stream flows are measured at the bottom of both streams that feed Grapevine Gut reservoir (Figure 64). The surface water levels at Catchpit 1 (SW01GVG) do not respond greatly during the end of 2016. Surface water levels increase quickly from 14th February and reach their highest level 3 days after the highest recorded rainfall. Water levels slowly decline until the high rainfall in March where water levels respond in a similar fashion. For water levels at Catchpit 2 (SW02GVG), stream levels remain steady until the end of the January rainfall where they increase quickly before flattening out. Surface water levels increase at the start of the February high rainfall and peak on the day of highest recorded rainfall.

Byron Gut surface water levels remain static until the high rainfall event in February. Water levels reach their highest 3 days after the highest recorded rainfall and respond to rainfall for the remainder of the period.

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The stream flow hydrograph for the v-notch weir in Wells Gut (SW03WG), at the bottom of the sub- catchment, have been plotted against the Grapevine Gut rainfall record (Figure 66). The irregularity of daily flows during times of rainfall indicates that the Wells Gut catchment responds rapidly to rainfall. Steep recessions in December, January, February and March indicate reduced storage within the sub-catchment. Conversely, later data during the winter season indicates a more even pattern to flows during periods of rainfall, with a sustained increase in flow rate between May and September 2017. The data suggest that due to a prolonged period of dry weather during the drought, the sub- catchment is shedding rainwater more quickly during short periods of rainfall and the high rainfall event in February rainfall. However later data between May and September 2017 suggests that the catchment storage has improved. This change may be due to the peaty soil within the Peaks wetting up over a 6-month period after the prolonged period of dry weather during the drought as peaty soils become hydrophobic when dry.

Longer term monitoring would enable a more complete picture of catchment behaviour. Catchment data would be more accurate if surface water monitoring data were collected from open channel structures such as weirs rather than enclosed catchpits where flow discharges into a pipe.

14.8.2 Soil Moisture Response to Mist and Rainfall

Soil moisture has been compared with the rainfall and mist record in Figure 67. Flax soil moisture is mainly static until early January when it quickly declines 15% reaching its lowest point in early February 2017. Soil moisture increases at the start of the February 2017 rainfall event reaching their highest concentration 3 days after the highest recorded rainfall. Soil moisture gradually declines from this peak and increases slightly during the March 2017 rainfall.

Fern thicket soil moisture declines over time between November 2017 and early February 2017, however there is a more marked response to soil moisture concentration from rainfall events than flax (November 2017 to January 2017). Fern thicket soil moisture responds to the February 2017 rainfall event during the same period of time as the flax, however soil moisture is seen to increase over a longer period of time reaching its maximum on 28th March 2017, 39 days after the highest recorded rainfall. This longer-term increase could be indicative of a more organic rich soil wetting up (such as a peat).

Without a longer data set it is difficult to draw conclusions from the limited soil moisture and climate data set. However, the data indicate that fern thicket soil moisture responds more readily to small rainfall events, whereas the flax soil moisture responses to larger rainfall events. This could be due to differences in plant morphology, the degree of shading the plant canopy provides which change rates of soil evaporation. Equally, the release of soil moisture may also be due to the type of soil that ferns and flax are growing in, with peaty soils releasing moisture more slowly than less organic soils. This may mean that the tree fern thicket is more resilient to drought than the flax habitat but again a longer-term data set would be required to confirm if this relationship truly exists.

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Figure 66: Daily Stream Flow and Rainfall Hydrogaph SW03WG

Daily Flow and Rainfall November 2016 to October 2017 70 2,500

60 2,000

50 /d) 3

1,500 40

30 1,000

20 Daily Rainfall Grapevine Gut (mm) Rainfall Grapevine Daily Daily Stream Flow SW03WG (m Flow SW03WG Stream Daily 500 10

0 0 01/11/2016 15/11/2016 29/11/2016 13/12/2016 27/12/2016 10/01/2017 24/01/2017 07/02/2017 21/02/2017 07/03/2017 21/03/2017 04/04/2017 18/04/2017 02/05/2017 16/05/2017 30/05/2017 13/06/2017 27/06/2017 11/07/2017 25/07/2017 08/08/2017 22/08/2017 05/09/2017 19/09/2017 03/10/2017 17/10/2017 31/10/2017

Date

Grapevine Gut Daily Rainfall (mm) SW03WG Stream Flow 7 Day Moving Average - Q (m3/d)

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Figure 67: Rainfall, Mist and Soil Moisture (November 2016 to March 2017)

Soil Moisture 7 Day Moving Average November 2016 to March 2017

100 60

90

50 80

70 40

60

50 30

Soil Moisture (%) Soil Moisture 40 Rainfall and Mist (mm) 20 30

20 10

10

0 0 07/11/2016 14/11/2016 21/11/2016 28/11/2016 05/12/2016 12/12/2016 19/12/2016 26/12/2016 02/01/2017 09/01/2017 16/01/2017 23/01/2017 30/01/2017 06/02/2017 13/02/2017 20/02/2017 27/02/2017 06/03/2017 13/03/2017 20/03/2017 27/03/2017 Date Grapevine Gut Daily Rainfall (mm) SM01GVG Volumetric Water Content - Fern (%) SM02WG Soil Moisture - Flax (%) MC01WG Mist as Daily Rainfall (mm)

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15 Sub-Catchment Water Balance

The water balance equation describes the hydrologic regime for a watershed where the surface-water divides and groundwater divides coincide, and for which there are no external inflows or out-flows for groundwater, takes the form:

! = # + % + ∆'( + ∆')

Where:

P = Precipitation;

Q = the average annual runoff;

E = annual evapotranspiration

∆'( = change in storage in a surface water reservoir;

∆') = change in storage in a groundwater reservoir.

(Freeze and Cherry, 1979)

Ultimately, a water balance describes water entering and exiting a catchment. In a steady state, one should equal the other, cancelling each other out. However, when calculating a water balance using data collected in the field, there is rarely a perfect balance due to the difficulties collecting data sets for all components of the site conceptual model and the short time scales over which some datasets are collected. In some cases, the data set may never be collected due to the costs involved in data collection or topographical challenges where it is not possible to install equipment where needed. As a consequence, some data sets have to be approximated using alternative data sources. Our dataset represent a snapshot in time for both catchments, are imperfect but offer some contrasting results.

Climate data for the water balance are presented in Table 25. The data comprise the rainfall and mist record for Grapevine Gut (WS02GVG) and Wells Gut (MC01WG) reported in Section 14.4, and calculated PE reported in Section 14.7. Annual runoff is derived from stream flow data reported in Section 14.6. Catchments areas calculated from aerial mapping data have been used for each sub- catchment water balance (Section 11.2.3).

Water balances for each sub-catchment are presented in Table 26 and Table 27. For both balances, mist recorded as rainfall is an important factor as it accounts for 63% of total water inputs.

The larger Grapevine Gut sub-catchment shows a significant surplus in the water balance as recorded stream flows are so small. The stream flows have been verified against recorded reservoir fill rates at Grapevine Gut reservoir (Section 14.6.1). Although there are discrepancies between the data sets, the rates of infill are of the same order of magnitude as the recorded stream flows. Despite concerns regarding the accuracy of stream flow and reservoir measurements, the sub-catchment is also shown to have a water surplus if mist is excluded from the calculation.

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Table 25: Water Balance Climate Data

Monthly Monthly PE WS02GVG MC01WG Rainfall and Date (mm) Rainfall (mm) Mist (mm) Mist (mm) 01/11/2016 176 135 429 564 01/12/2016 194 100 356 456 01/01/2017 222 67 121 188 01/02/2017 189 489 647 1136 01/03/2017 184 373 692 1066 01/04/2017 178 114 127 241 01/05/2017 177 140 143 283 01/06/2017 121 269 289 558 01/07/2017 137 117 222 339 01/08/2017 135 211 126 337 01/09/2017 160 68 176 244 01/10/2017 156 27 254 280

Total 2,030 2,110 3,582 5,691 Min 121 27 121 188 Max 222 489 692 1136 Average 169 176 298 474

Table 26: Grapevine Gut Water Balance

Water Balance Component Total Comment

Catchment Area (m2) 207,568 Derived from aerial photography and mapping data.

Annual Rainfall (m3) 1,181,333 Value in brackets excludes mist as rainfall.

(437,927)

Annual Evapotranspiration (m3) 421,346

Rainfall - PE 759,987 Value in brackets excludes mist as rainfall.

(16,581)

Annual Stream Flow (m3) 5,975

Surplus/Deficit (m3) 754,013 Surplus with mist and rainfall and when mist is excluded from rainfall calculations (value in (Rainfall – PE – Stream Flow) (10,607) brackets).

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Table 27: Wells Gut Water Balance

Water Balance Component Total Comment

Catchment Area (m2) 140,409 Derived from aerial photography and mapping data.

Annual Rainfall (m3) 799,111 Value in brackets excludes mist as rainfall.

(296,235)

Annual Evapotranspiration (m3) 285,018

Rainfall - PE 514,092 Value in brackets excludes mist as rainfall.

(11,216)

Annual Stream Flow (m3) 302,196

Surplus/Deficit (m3) 211,896 Surplus with mist and rainfall. Deficit if mist is excluded from rainfall calculations (value in (Rainfall – PE – Stream Flow) (-290,980) brackets).

The smaller Wells Gut sub-catchment shows a surplus in the water balance, however there is a significant deficit if mist is excluded from the balance. The calculated stream flows are considered reasonable given the observations made in Section 14.6.2 about flow measurements in the catchpits, as over 75% of all flows in Wells Gut and Byrons Gut were recorded at the v-notch weir at the bottom of the sub-catchment. The v-notch weir is the most reliable source of flow rates within the sub- catchment and also provides an indication of sub-catchment outflows.

Despite concerns about the accuracy of some data sets, the water balances provide some insight into the catchments. Grapevine Guts catchment area is 32% larger than Wells Gut, but stream flows are only 1.9% of total flows measured in Wells Gut. Both sub-catchments have a water surplus, so where could the water be going?

The limited geology and hydrogeology data for the island provide one explanation. Assessments of the islands hydrology reported that the islands geology, high and well distributed rainfall and large variations observed in catchment yields, suggested that an appreciable volume of water is lost by percolation (Sir William Halcrow and Partners, 1969). The appearance of some exposed beds of scoraceous lava indicated that zones of very high permeability may also be expected below the surface. Zones of high permeability have also been reported by WSP (WSP, 2017). Unconsolidated gravels in the valleys which, combined with the upper layer of fractured bedrock, form a superficial perched aquifer of limited storage but which are thought to be recharged by surface runoff and rainfall. These superficial aquifers are thought to feed many of the islands springs but are susceptible to drought or reduced flow due to periods of low rainfall.

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The assessment of drought data in Section 14.8 indicates that all stream flows respond to rainfall. At the top of the Wells Gut catchment, stream flows also increase over time indicating storage at the top of the sub-catchment is increasing (after a prolonged period of drought) with a corresponding increase in spring flow. The difference in total flows between Grapevine Gut and Wells Gut may also be due to the underlying geology where one sub-catchment loses more water to percolation (groundwater recharge) than the other. This may explain the significant difference in flows within the Grapevine Gut compared to the unexplained surplus water in the water balance.

The differences in vegetation may also play a part in the water balances. Wells Gut has 15% of its land area as tree fern thicket, whereas Grapevine Gut has only 5%. Soils beneath the tree fern thicket in the cloud forest are appreciably more organic and over the millennia have formed a rich, deep peaty soil. Given the larger area of tree fern thicket in Wells Gut, it is likely that the area covered by a rich peat soil is larger than Grapevine Gut (which has been impacted more by forestation and invasive plant species). This peaty soil provides not only a good carbon sink but also provides good water retention, soaking up rainfall and releasing it slowly. The gradual increase in stream flows in SW01WG at the top of the Wells Gut sub-catchment may also be due to the peat wetting up after a prolonged period of drying out and releasing more water from storage. A sub-catchment which is underlain by a perched aquifer feeding springs with overlying peaty soil will provide a good source of water, as groundwater recharge will provide the spring baseflow whilst the peat provides a slow release source of water to the vegetation and streams.

Due to the limited data available for the island and within the sub-catchments, the relationship between geology, soils, rainfall recharge, dry weather flow and spring flows cannot be more accurately assessed. The Halcrow report (Sir William Halcrow and Partners, 1969) evaluated mean base flow for the islands perennial streams and calculated a mean base flow for all perennial streams of 3% annual rainfall. This would be 22,800 m3/a for Grapevine Gut (4 times greater than stream flows measured between November 2016 and October 2017) and 15,423m3/a for Wells Gut (2 times greater than annual flows measured in SW01WG and SW02WG).

16 Climate Change Assessment

16.1 Climate Change Data

A review of global climate change data associated with St Helena was completed by iMC in 2014 for EMD (iMC Worldwide, 2014). This section expands on the iMC analysis of global climate change data and updates with a review of other data sets.

The islands long-term climate record has been reported in Section 4. A trend analysis of island temperature and climate was complete by IMC (Figure 68) (iMC Worldwide, 2014). Temperatures have been increasing on the island for the past 100 years and have increased approximately 1oC since the 1920s. In contrast, rainfall has been highly variable with the long-term linear trend of a decrease in rainfall since the 1890s to the present. However wetter conditions have been experienced since the 1990s, with February 2017 being the 6th wettest month on record.

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Figure 68: Annual Average Temperature and Rainfall for St Helena

To assess climate change risks, we need to consult global climate change models. However, due to the scale of the models, small islands such as St Helena are not adequately represented due to their size and are usually located within a much larger grid cell. As a consequence, we cannot consult global climate models to specifically look at St Helena but need to assess the model cell that St Helena is located within. These larger scale global models represent the larger scale climate circulation patterns and ocean influences that dominate the climate of St Helena and will not accurately represent local conditions.

Current global climate models (known as CMIP5) have been used by the Intergovernmental Panel on Climate Change (IPCC) to assess climate scenarios. Four scenarios have been developed globally and are call Representative Concentration Pathways (RCPs). Each represent different climate change “forcing levels” (RCP8, RCP6, RCP4.5 and RCP2.6) e.g. relative climate change impact resulting from different greenhouse gas concentrations in the atmosphere. The closest land mass to St Helena that the IPPC global climate change models are available for is Africa (which includes parts of the South Atlantic region including St Helena).

16.1.1 University of Cape Town Climate Information Platform

The University of Cape Town has developed more local scale climate models based on the larger IPCC model for Africa (including those for St Helena) and can be located through the climate web portal of the Climate Systems Analysis Group (CSAG) (University of Cape Town, 2018). The downscaled models are based on the RCP4.5 and RCP8 greenhouse gas concentration model scenarios and include climate data collected by the UK Met Office at the Bottom Woods weather station on St Helena. The models output climate change scenarios for temperature and rainfall up to 2100. For the purpose of this

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Figure 69 and Figure 70 show predicted changes in maximum and minimum temperature on St Helena for the RCP4.5 model scenario. The bars show the range of scenarios for different models (confidence intervals). The grey lines show the individual model runs, highlighting the complexity of using models to forecast future climate change at this scale. Broadly, temperatures are expected to change by an average of 1oC (the relative changes in maximum and minimum temperature are similar) in the next 40 years. On a seasonal basis changes in average temperature may fluctuate between 0.7 and 1.8 oC greater than current temperatures. For the RCP8 model scenario, the average change in temperature is very similar.

Figure 69: St Helena Average Maximum Temperature RCP4.5

Figure 70: St Helena Average Minimum Temperature RCP4.5

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Figure 71, Figure 72 and Figure 73 show predicted changes in rainfall, maximum daily rainfall and the number of wet days on St Helena for the RCP4.5 model scenario. The climate model outputs do not agree as well for rainfall however they show that the months of May and June are expected to be far drier with a reduction of between 10 to 16mm rainfall (up to 25% drier in May and 30% drier in June, based on the monthly long-term average rainfall reported at Bottom Woods Met Station). January, September and November are predicted to be wetter months with an additional 4 to 5mm rainfall (between 14% and 26% higher than the monthly long-term average rainfall reported at Bottom Woods Met Station). The number of wet days increases by at least 0.5 day for January and February, with November expected to have an additional 2 wet days. For the RCP8 model scenario, the average change in is very similar.

Figure 71: St Helena Total Monthly Rainfall RCP4.5

Figure 72: St Helena Maximum Daily Rainfall RCP4.5

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Figure 73: St Helena Number of Wet Days RCP4.5

The downscaled climate change model scenarios highlight two key trends between 2040 and 2060:

• Temperatures in the region are rising and will increase by an average of 1oC; and • Changes in rainfall are highly variable and any climate change trends are likely to be masked by variability for several decades.

Notwithstanding the variability in rainfall, the global climate models and evidence of climate change across the world (glaciers receding, arctic ice flows reducing in size, extreme weather events) indicate that climate change is already having an effect on global climate. There is sufficient evidence for St Helena to consider the potential effects of climate change in all decision making and the planning of island infrastructure and growth.

16.1.2 World Bank Climate Change Knowledge Portal

The World Bank has a Climate Change Knowledge Portal which also interprets IPPC CIMP5 global climate modal data (World Bank, 2018). Climate model predictions for St Helena are compared against a reference period (1986 to 2005). The World Bank climate change projection for monthly change in temperature indicates that in the period 2080-2099 temperatures will change between 0oC and 40C, with median island temperatures increasing by an average of 2oC (Figure 74). Changes in rainfall are predicted to fluctuate by -100 mm and +200 mm per month by 2080-2099, with a median change of between -2.5 mm and +2.05 for all model scenarios (Figure 75). This change in rainfall is equivalent to a 5% increase or decrease in annual rainfall based on the long-term average annual rainfall recorded at Bottom Woods weather station).

The World Bank climate change portal also provides an assessment of seasonal variability in annual rainfall between 2050 and 2100, including the change in mean monthly rainfall and the number of days with very heavy rainfall.

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Figure 74: Modelled Change in Temperature (2080-2090)

Figure 75: Modelled Change in Rainfall (2080-2090)

Changes in projected monthly mean rainfall (precipitation) for 2050 are shown in

Figure 76. The graph compares all RCPs of CIMP5 climate modelling. Positive values indicate that monthly rainfall is likely to increase and decrease compared to the baseline. The shaded area represents the range between the 10th and 90th percentile of all climate projections. The months of January to March show the greatest change in projected rainfall for median values with the overlying trend for an increase in rainfall in these months of between 0mm and 8mm (except for the RCP8.5 model scenario). The month of April has a modelled decrease in rainfall of between -1mm and -4mm when compared to the baseline.

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Figure 76: Change in Modelled Average Monthly Rainfall (2050)

The number of modelled days with heavy rainfall (at least 20mm/day) are shown in Figure 77 for the period 2020 to 2100. On average the number of heavy rainfall days will increase on St Helena by 0.5 day per annum, with a range of 0 to 1 days.

A "dry day" is a day without any agriculturally meaningful rainfall, which is generally defined by a threshold of 0.1 mm/day. The figure indicates that the mean number of consecutive dry days for RCP 2.6 and RCP 4.6 scenarios will be a similar order of magnitude to the 1986 to 2005 long term mean of 210 days. However, the range of projected consecutive dry days indicates that in some years, the number of consecutive dry days could increase to a maximum of 360 days (an increase of 48%) for these scenarios.

The maximum number of consecutive dry days is an important metric for rain-fed agriculture as it directly impacts soil moisture, and crop growth. As climate warms, one of the signals is the increase in contrast: when it rains, it might rain harder, but when its dry it might get drier. The trend toward more consecutive dry days and higher temperatures will increase evaporation and add stress to limited water resources, affecting irrigation and other water uses. Long periods of consecutive days with little or no precipitation also can lead to drought. In general, the average annual maximum number of consecutive dry days are projected to increase for the higher emissions scenarios. Some crops, however, might benefit from this change, particularly when the dry conditions exist in specific parts of the crop cycle (World Bank, 2018).

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Figure 77: Modelled Days with Heavy Rainfall (2020 to 2100)

A final climate related scenario relevant to DPLUS051 are the number of consecutive dry days modelled for St Helena between 2020 and 2100 (Figure 78).

Figure 78: Modelled Consecutive Dry Days (2020 to 2100)

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16.2 Climate Change Risks

The UK Government department Joint Nature Conservation Commission has overarching responsibility for supporting the management of the UK Overseas Territories (UKOT’s) environmental resources. JNCC published a series of climate change documents for the UKOT’s in 2008, most notably a report titled Climate Change in the UK Overseas Territories – An Overview of the Science, Policy and You (JNCC, 2008). The report identified the follow key climate change risks for St Helena:

1. Fish stocks and the fishing industry are at the highest risk from climate change; 2. Tourism associated with sports fishing are at a high risk from climate change; 3. Changes in air and sea temperatures could influence weather patterns and cause disruption to established wind and rainfall patterns, leading to floods, drought, and/or soil erosion; 4. Research points to a strong warming trend in air temperature (2°C over 60 years) and a slight decrease in rainfall. Over time, the latter could have implications for local water supplies; 5. Altitudinal shifts in vegetation zones; and 6. Currently identifiable ecological imbalances could become even more marked.

Since the report was written, risks associated with a land-based ecotourism economy can be added to those identified by JNCC alongside operation risks to the recently opened airport (associated with high intensity rainfall events, high winds and increased risk of soil erosion).

The risks identified by JNCC are still valid for the Peaks NCA and the islands water supply, with the key climate change risks to the study area being:

1. Changes to air and temperature disrupting wind and rainfall patterns e.g. rainfall is more erratic with longer drier period and more short high intensity rainfall events; 2. Increased risk of soil erosion due to high intensity rainfall events and high wind 3. Increase in air temperature (2°C over 60 years) with slight decrease in rainfall; 4. Reduced rainfall (and mist) has negative impact on local water supplies; 5. Altitudinal shifts in vegetation zones; and 6. Increase in ecological imbalances.

Altitudinal shifts in the vegetation zone are critical for the endemic plants and animals within the Peaks NCA, as a shift in the vegetation zone could significantly reduce the size of the cloud forest. In the case of St Helena, the cloud forest has been significantly damaged through the introduction of invasive species, deforestation and cultivation. The proposed cloud forest restoration plan outlined in Section 17 identifies the extent of the original cloud forest in the study area, which covered an area 4 times greater than the remaining cloud forest in Grapevine Gut and Wells Gut. By restoring the cloud forest to its original extent, any climate change risks to the vegetation zone will be reduced as the proportional impact on cloud forest habitat would be smaller than if the current area of habitat remained the same.

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The sensitive selection of invasive species clearance solutions is also critical for maintaining the cloud forest soil structure. As the risk of soil erosion increases due to a projected increase in high intensity rainfall events and high wind, clearing large areas of land for restoration increases risks of large-scale soil erosion. It is recommended that these risks are mitigated through the use of “pocket planting” or similar, where small areas of land are cleared, replanted and stabilised.

The JNCC climate change report Guidance for Biodiversity Conservation and Management in a Changing Climate in the UK Overseas Territories (JNCC, 2008) also identified 6 guiding principles for adapting to and mitigating the effects of climate change which are still relevant to this project and St Helena. The principals are reproduced in Table 28.

Table 28: JNCC Climate Change Biodiversity Guiding Principals

JNCC Climate Change Guiding Principals 1. Conserve existing biodiversity (including protected areas, high quality habitats and ecological variability). 2. Reduce source of harm not linked to climate change (such as invasive species). 3. Develop ecologically resilient and varied landscapes. 4. Establish ecological networks through habitat protection, restoration and creation. 5. Make sound decisions based on analysis. 6. Integrate adaptation and mitigation measures into conservation management, planning and practice.

It is recommended that these guiding principles are used to as a climate change mitigation and adaptation check-list for all proposed development and conservation work on the island. The limited data we have presented above suggest that endemic native habitats are potentially more resilient to climate change than the introduced vegetation. This ecological resilience will be an important factor in determining how St Helena’s ecosystems respond to any changes in climate and ensuring a sustainable water supply. Unfortunately, we cannot wait to find out; a long-term commitment to genuinely restoring larger areas of the cloud forest habitat to its former extent is needed to ensure that sustainable water provision is safeguarded. Native buffer zones will also be required between the cloud forest habitat and the lower agricultural areas.

16.3 Water Demand

In order to understand future pressures on water use on Saint Helena, it is helpful to review current water consumption. Water data has been provided by Connect (Connect Saint Helena, 2018b) which is understood to be treated water volumes, with population data provided by the SHG statistics department (SHG, 2018). The islands population data is recorded on a monthly basis, whereas treated water consumption is reported annually, starting in April and finishing in March. As a consequence, the islands population in March has been used to evaluate domestic water consumption per person per day on an annual basis with the year ending in March. At the time of writing, Connect reported treated water for domestic consumption as 75% of total treated water, with commercial water 21% and agricultural water 4% of treated water consumption. Annual treated water consumption reported as litres per person per day (l/p/d) is presented in Figure 79. The island population in March 2018 was recorded as 4,712.

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Figure 79: Saint Helena Water Treated Consumption Per Person Per Day

Saint Helena Treated Water for Domestic Consumption 2009 to 2018 250

200

150

100 Treated Water (l/p/d) Water Treated

50

0 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 2016/2017 2017/2018

Water Year

Average Treated Water for Consumption (l/p/d) WHO Water Consumption (l/p/d) UK Water Consumption (l/p/d)

Note: the data provided for treated water consumption for domestic use differs from the billed water consumption figures for 2014 to 2017, published in the March 2017 Connect Saint Helena Report and Financial Statement (Connect Saint Helena, 2017).

Average treated water consumption for domestic use is 167 l/p/d and can be seen to fall from 169 l/p/d between 2009 and 2014 to 145 l/p/d in the water year 2013/2014. The low point coincides with one of the islands most recent droughts, indicating that water efficiency measures were working. However, since 2013/2014, treated water for domestic consumption has been on the increase to a high of 196 l/p/d (2017/2018). This increase includes the 2016/2017 drought year, indicating that water efficiency measures have not been as successful as previous years. The most recent publication of average treated water consumption for domestic use is 214 l/p/d published on 30th June, 2018 indicating that treated water for domestic consumption has continued to increase.

Billed water consumption figures show that water consumption declined by 10% between 2016 and 2017 (for all water use) as the public responded to water restrictions during the drought. Treated water for consumption data show higher water demand during this period than the billed water consumption figures, indicating that treated water may have been lost in the distribution network due to leakage. Total volume of water billed in the 2016 to 2017 year is 265,623m3. Treated water for this period was 412,880m3 according to data provided by Connect (Connect Saint Helena, 2018b),

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Average island treated water consumption has also been assessed against average UK domestic water consumption (Waterwise, 2017), and World Health Organisation (WHO) recommended domestic water consumption (Howard, Jamie and World Health Organisation, 2003) for all domestic consumption and hygiene requirements. Treated domestic water consumption on St Helena is on average 19% higher than UK domestic water consumption and 67% higher than WHO water requirements. This may be partly due to leakage within the distribution network.

The most recent island census indicated that the population had risen by 11.2% since the previous census in 2008 (Government, 2016). Some of this population increase may be related to migrant workers and returning Saints who have worked on the airport and wharf construction projects. Resident population numbers from census data between 1901 and 2016 are presented in Figure 80. The census data show an increase in island population from 1911 to 1987, discounting the large decline in population between 1901 and 1911 associated with the repatriation of 6,000 Boer war prisoners who had been imprisoned on the island. The population declined in the 1990’s and early 2000’s before increasing to the current population size (4,534 in 2016). Between 1911 and 2016, the island population has averaged 4,519.

The island currently has one of the oldest populations in the world (average age 47). There are no available published reports for projected population increase. As a consequence, we assume that the resident island population will remain static at the 1911 to 2016 average, with additional pressure placed on the island water supply through an increase in the tourist population.

Figure 80: St Helena Resident Population Census Data, 1901 to 2016

St Helena Total Resident Population, 1901 to 2016 12,000

10,000

8,000

6,000

4,000 Resident Population Resident 2,000

0 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 Year Total Resident Population

16.4 Tourism and Water Demand

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The Saint Helena airport project was commissioned by the UK Government in order to support the development of a tourism industry on the island. As part of the Saint Helena airport project, the UK Department for International Development (DFID) commissioned a Visitor Demand Assessment report (DFID et al., 2013) which evaluated the potential number of visitors to the island within the first 5 years of the airport opening. We used this data to estimate increases in island population over time with water availability, to determine potential impacts on the islands water resource due to increased demand through tourism and the effects of climate change. DIFD have an overall target of 30,000 tourists per year, more than 6 times the March 2018 island population.

The Visitor Demand Assessment report modelled three scenarios for tourism;

1. Organic growth; 2. Modest growth; and 3. Rapid growth.

Scenario 2 (modest growth) was identified as the most realistic, with one new hotel being developed on the island. This has proved to be accurate as a new hotel opened in November 2017. Table 29 shows the Scenario 2 model predicted increase in island population due to tourism (excluding Saints travelling overseas) with predicted increase in water consumption, based upon the islands average domestic water consumption data (Section 16.3).

The island has 2,010 residential properties (Saint Helena Government, 2018). The increase in annual water demand at the end of year 5 is equivalent to an additional 49 households (based on 4 people per household), an increase of 2.5%. The tourism target of 30,000 tourists per year is equivalent to 147 permanent households, or an additional 7.5% of current water demand.

Table 29: Predicted Tourism Increase

Year Predicted Number of Visitors Predicted Increase in Water Consumption (m3/a)

Year 1 4,400 735

Year 2 6,700 1,119

Year 3 8,100 1,353

Year 4 9,000 1,503

Year 5 10,100 1,687

Given that the total amount of water available on island is unlikely to change significantly due to the effects of climate change, the additional water required for tourism could be sourced from existing surface water sources and recently identified groundwater sources (WSP, 2017). However, as

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16.5 Climate Change Impacts on Water Supply

Using University of Cape Town climate model data for predicted changes in rainfall provided in Section 16.1, it is possible to estimate the potential climate change impact on the islands water supply in Wells Gut and Grapevine Gut.

Recharge data has been amended for both sub-catchments to consider the potential reduction in rainfall and mist in May and June and increases in January, September and November. The amended water balance for each sub-catchment indicates that Wells Gut has a 171m3 reduction in recharge and Grapevine Gut has a 244 m3 reduction in recharge. The total reduction in available water due to impacts of climate change is 415 m3, which is equivalent to 2 average households’ water per annum.

Whilst the data suggest that there is no material change in available water within each sub-catchment due to climate change, the underlying message is that the way the island receives its water is going to change. The annual volume of water the island receives may not change, but the number and distribution of wet and dry days will change along with rainfall intensity. For example, a higher number of dry days or months will be offset by very wet days or months where high intensity rainfall events are encountered (as recorded in February 2017). This means that the water infrastructure will need to have capacity to retain larger volumes of water which are drawn down over a longer period, rather than being “topped up” on a regular basis by more regular rainfall. Alternatively, encouraging a larger area of cloud forest and developing a richer peaty subsoil in the Peaks will help even out the islands water supply by holding back rainfall runoff, and releasing water in a slower less “flashy” flow.

17 Outline Cloud Forest Restoration Plan

Lambdon & Darlow (2012) make reference to the cloud forest being largely confined to the highest ridges of the Peaks, generally over 750mASL. Lambdon & Darlow (2012) also report that the cloud forest is likely to have extended down to the flanks of the Peaks as far as Halley’s Mount (680mASL) and Osbourne’s (560mASL) and been continuous around the great crescent of the Central Ridge.

Mist data collected in the Peaks has provided further insight into the altitude that mist forms in the Peaks NCA. The lowest elevation mist capture logger (MC01PG, 729mASL) located on the windwards (south east) side of the Peaks did not report any mist as rainfall between October 2016 and January 2017, whereas the second lowest elevation mist logger (MC02PG, 752mASL) reported mist as rainfall between November 2016 and January 2017. On the leeward side of the Peaks (north west) all Hobo mist loggers reported mist between October 2016 and January 2017, including MC02WG which is located at 692mASL. All loggers reported mist for the remainder of the monitoring period where they were all operating, between February and October 2017.

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Based on the evidence of mist data collected between October 2016 and October 2017, it is recommended that a restoration plan is based on the likelihood of mist forming and being intercepted by endemic plants in the Peaks. This limits cloud forest restoration above the 690mASL contour in Wells Gut and Grapevine Gut (close to the 680mASL contour of Halley’s Mount), shown in Figure 81. It is also recommended that an additional 25m buffer below this contour is managed for invasive species and allow for any climate change adaptation. Based on the 690m contour, the total area of habitat that could be restored is 16ha, excluding areas already populated by cloud forest endemic plants. With restoration areas of 8.02ha (80,200m2) in both Grapevine Gut and Wells Gut.

The climate change assessment identified altitudinal shifts in the vegetation zone as being critical for the endemic plants and invertebrates within Grapevine Gut and Wells Gut, as a shift in the vegetation zone could significantly reduce the size of the cloud forest. As part of a wider island climate change mitigation strategy, restoring the cloud forest in both sub-catchments above the 690m contour would increase the cloud forest habitat in the study area from 3.6ha to 19.7ha (over 400% increase on current levels) and increase the islands total cloud forest habitat by 40%.

There is an abundance of knowledge on the island regarding the pros and cons of different restoration techniques which could be used to restore the cloud forest in Grapevine Gut and Wells Gut, including research funded by Darwin Plus to evaluate invasive species removal (DPLUS059) and plant propagation (DPLUS029). It is recommended that future restoration programmes consult this body of evidence to select the best available technique to restore the cloud forest, limit the potential for soil erosion during restoration of habitat and look for opportunities to limit time consuming and costly habitat maintenance.

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Figure 81: Proposed Restoration Area and Buffer Zone

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18 Ecosystems Services Assessment

To fully appreciate the value of St Helena’s cloud forest and the benefits that restoring the cloud forest have for the island, an ecosystems services assessment has been completed using the method outlined by the Institute of Environmental Sciences (Everard, Waters and Institution of Environmental Sciences, 2013). The IES method draws on UK Government Guidance and the Millennium Ecosystem Assessment methodology.

Ecosystems services are the benefits that the natural environment provides society. These benefits support our economy, health and quality of life and are normally overlooked. This ecosystems services assessment looks at the benefits and opportunities that the cloud forest in Grapevine Gut and Wells Gut provide St Helena.

The key benefits that the cloud forest provide are:

1. 38% of the islands water supply, through mist capture and direct rainfall which recharge the islands aquifers (groundwater) and streams; 2. water for drinking, washing and production of food (through irrigation); 3. habitat for over 1/3 of all UK mainland and Overseas Territory endemic species; 4. climate regulation – the cloud forest catches mist, which provides 60% of the sub-catchment water; 5. a carbon sink to mitigate climate change impacts, via rich the peaty soil and vegetation; 6. flood regulation – retain water in the catchments for longer periods (see surface water levels in SW01WG), reducing “flashy flows” during high rainfall events; 7. a significant eco-tourism destination for the island; 8. a recreation area for the island’s population – walking, running, nature conservation activities; and 9. health – providing a calm, quiet natural environment away from man-made distractions.

Ecosystem services Grapevine Gut and Wells Gut provide St Helena are presented in Table 30. The Total Economic Value (TEV) assessment identifies 4 categories of ecosystem use:

• Direct use: where individuals make actual or planned use of an ecosystem service; • Indirect use: where individuals benefit from ecosystem services supported by a resource rather than directly using it; • Option value: the value that people place on having the option to use a resource in the future even if they are not current users. These future uses may be either direct or indirect; and • Non-use value (also known as passive use) is derived simply from the knowledge that the natural environment is maintained.

An estimation of the value of the cloud forest to the island for public water supply (as a provisioning service) has been provided in more detail in Section 19.

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Table 30: St Helena Cloud Forest Ecosystem Services

Non-use MA Group Service Direct Use Indirect Use Option Value Value

Millennium Assessment Framework TEV Framework

Provisioning Fresh water supply – Grapevine Gut and Wells Gut provide 38% of the islands water supply. The cloud forest catches mist, which provides 60% of the sub-catchments water.

Food – water used to support irrigation of crops including agricultural land in the Longwood area.

Habitat – the cloud forest provides habitat for a significant number of St Helena’s endemic plants and invertebrates. St Helena provides habitat for over 1/3 of all UK mainland and Overseas Territory endemic species.

Natural medicines / pharmaceuticals – little is understood about the islands endemic plants and fungi concerning their medicinal benefits.

Regulating Climate and air quality – long term sequestration of pollutants such as sulphur dioxide, nitric acid, ammonia and nitrous oxides in trees and other vegetation. Provides a carbon sink for the island.

Climate resilience – a varied and complex habitat provides a more climate resistant island.

Water – retain water in the catchments for longer periods (see surface water levels in SW01WG), reducing “flashy flows” during high rainfall events.

Natural hazards – stabilises soils preventing soil and nutrient washout.

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Non-use MA Group Service Direct Use Indirect Use Option Value Value

Cultural Tourism – the Peaks NCA (within which Grapevine Gut and Wells Gut sit), comprise an important eco-tourism destination for the island.

Recreation – the Peaks NCA provides an important recreation area for the

island’s population e.g. walking, running, nature conservation activities.

Health – provide a calm, quiet natural environment away from man-made distractions.

Supporting Soil formation – cloud forest vegetation creates an organic rich peaty soil.

Nutrient cycling – peaty soils within the cloud forest retain nutrients from decayed organic material. Supporting services are valued through other categories of ecosystem Agriculture – water from the catchments support agriculture (arable, services. livestock and hydroponics).

Site of Environmental Importance - Wells Gut supports minimum flows within Fisher’s valley, which has been identified as a candidate RAMSAR site due to its importance for wetland birds.

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19 Increasing Mist as Rainfall for Public Water Supply

A crude comparison of recorded stream flows with catchment area indicates that 1m2 of catchment within Wells Gut provides the equivalent of 2m3 water per annum, whereas 1m2 of catchment within Grapevine Gut produces the equivalent of 0.5m3 water per annum.

Several topographical, soil, geological and botanical factors may have a significant effect on the amount of water that reaches the streams in each sub-catchment; these are not well understood. However, the flow data collected between 2016 and 2017 indicate that Wells Gut has significantly more surface water flow than Grapevine Gut. Further investigation of each sub-catchment geology and hydrogeology is needed to identify key mechanisms for percolation of recharge into aquifers, spring flow and the identification of non-aquifers or aquitards.

A proposed restoration area for Wells Gut would be above the 690mASL contour (see elsewhere). The higher proportion of cloud forest vegetation within the sub-catchment (tree fern thicket), peaty soil and high surface water flows make Wells Gut an ideal first candidate for cloud forest restoration to improve water security. These characteristics indicate that cloud forest vegetation is likely to be the main agent for mist capture within Wells Gut.

The native cloud forest canopy of St Helena is structurally more complex than the other vegetation types found in Wells Gut. As canopy ‘roughness’ increases mist capture, it is not unreasonable to assume that restoration of cloud forest will increase mist capture and hence water supply whilst also safeguarding and increasing the biodiversity of the restored areas. The benefits of providing increased mist capture for water supply through restoration will incur initial costs. Plant propagation is estimated at £2.50 per plant (assuming efficiencies in propagation since 2015), from work developed by the EMD Conservation team in 2015 to support the St Helena Airport Landscape and Environmental Management Plan (Sansom, Malan and Thomas, 2015). Local staff time needed to remove invasive species and restore habitat over 1 year have been provided by EMD, based on a recent scheme to restore a 100m2 strip of flax within the Peaks NCA. Staff time costs are based on 2015 LEMP data adjusted for inflation. Here, we assume a planting density of 20 plants m-2. Actual planting densities will differ depending upon the condition of the land being restored and the amount of flax or other invasive species that need to be removed. It is recognised that propagation costs will continue to reduce as new techniques developed by DPLUS029 further improve nursery propagation efficiencies. The costs do not include resources for ongoing management of the additional area of restored cloud forest. However, it is hoped that these would be limited due to the density of planting and removal of invasive species.

A summary of cloud forest restoration costs vs recent water infrastructure construction costs is presented in Table 31. Costs are based on an equivalent volume of water for each scheme, with cloud forest restoration costs calculated as £116 per m2 for Wells Gut.

Based on restoration costs, data indicate that 1m3 additional water for public water supply via mist capture will cost in the region of £58/m3.

The costs of cloud forest restoration compared with the Hutts Gate 2 reservoir construction are over 55% more expensive in the short term. Costs for cloud forest restoration are also higher when compared with refurbishing Harpers 3 for an equivalent volume of water. However, the restoration of

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Table 31: Cloud Forest Restoration Cost Comparison

Scheme Description Cost (£) Comments

Harpers 3 Increase in storage capacity in the reservoir 44,390 Costs published by Saint Helena from 8,000m3 to 20,000m3. Government, 2018.

Equivalent cloud forest restoration costs 764,325 per m3.

Hutts Gate 2 Construction of a new reservoir with 313,872 Costs published by Saint Helena 11,200m3 capacity. Government, 2018.

Cloud Forest Costs of restoring Wells Gut cloud forest to 713,400 Costs of water based on Hutts Gate 2 Restoration produce an additional 11,220m3 water for reservoir construction cost per m3 comparison with Hutts Gate 2. reservoir capacity.

The costs of restoring 16ha in both catchments above the 690m contour is estimated to be in the region of £18.6 million. Quantifying the value of this benefit to the island and to the world for water supply, soil creation and stabilisation, health, ecotourism and carbon management is difficult and is beyond the scope of this current project. However, DEFRA spent £445 million in the 2016 to 2017 financial year on biodiversity in the UK. Funding a cloud forest restoration scheme on St Helena represents only 4% of the annual DEFRA budget, presenting a very cost effective method of increasing globally important biodiversity. Essentially, this would protect up to 1/3 of the UK mainland and Overseas Territory endemic biodiversity, increase St Helena cloud forest habitat by 40% and would meet commitments to the convention on biological diversity and the global plant conservation strategy in particular. The potential benefit to the island’s water supply could reach an additional 146,886m3/a through additional mist capture. This could be equivalent to an additional 33% treated water for consumption, based on 2017/18 figures.

The approximate costs calculated here, indicate that additional water provision through mist capture from cloud forest restoration would be more expensive than the infrastructure costs of improving water storage, depending on the costing model. Adopting an ecosystem service approach to costs instead of a simple construction model of costs will require a shift in attitude across Government, the private sector and society. This is because water is perceived as being a free resource, with only the costs of abstraction, storage, treatment and distribution considered in economic assessments. To

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It is understood from Connect that previous predictions of water demand from former studies have already been exceeded. In addition, the additional storage in Harpers 3 and Hutts Gate 2 reservoirs will not satisfy long-term demand. The development of a dam at the bottom of Fishers Valley (a candidate RAMSAR site for its unique wetland habitat), which will increase stored water capacity by a factor of 10, is being considered as an option by Connect. Having this sizable body of water to fall back on would provide an increased level of water security needed to cope with predicted increases in demand (Personal communication, July 2018). Any proposal to increase water storage in the wetland will need to include a detailed environmental impact assessment to include economic, environmental and biological costs and benefits and alternative options.

20 Conclusions and Recommendations

The project has highlighted that there is limited hydrological and hydrogeological data within the study area to determine minimum flows needed to support surface water habitats and ecosystems. The data suggest that stream flows measured from the catchpits may not be representative of total stream flow within each sub-catchment.

The water features survey found that there were no design records available for structures except for the v-notch weir in Wells Gut and Grapevine Gut reservoir. Nor are there any “as-built” drawings for structures.

Flows from Wells Gut and Grapevine Gut are recorded several hundred metres from the catchpits and weir as in-flows into the Hutts Gate water treatment works. As a consequence, the accuracy of surface water abstraction data cannot be determined, as water could be lost through leakage in the water distribution network before inflows are recorded at the water treatment works.

20.1 Aerial Surveys

The use of a small unmanned survey aircraft has proved to be successful and collected valuable data to support the development of an orthomosaic photograph for the vegetation survey, digital elevation models, catchment area boundaries and for the calculation of sub-catchment areas. The aerial surveys have shown that aerial photography can enhance conservation work, as the data can be used to:

• compare aerial photographs of key conservation areas on an annual basis to assess rates of change; • plan conservation work; • monitor ongoing conservation work; • improve health and safety; and • measure the success of invasive species and cloud forest restoration programmes.

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20.2 Vegetation Survey

The vegetation survey confirmed how dominant non-native plants are in both of the Guts, with 93.5% non-native in Grapevine Gut and 83% non-native in Wells Gut. Flax is the dominant non-native vegetation type, with mixed flax and whiteweed second dominant. Native/endemic plants are located towards the highest ridges towards the peak and include only two vegetation types: tree fern thicket is the most abundant with small patches of black scale fern thicket which occurs in areas actively managed for conservation.

In both Guts, endemic cloud forest vegetation is found up high on the ridges of the Peaks.

The Grapevine Gut land use map published by Mathieson (Mathieson, 1990) provides a useful benchmark for comparing changes in the sub-catchment over time. There is no reference to tree fern thicket on the 1990 map, indicating that all cloud forest endemic plants have been restored within the sub-catchment over the past 18 year through the efforts of the island conservation teams. The 1990 map also indicates that the area of flax has increased by approximately 25%. There is no reference to whiteweed on the 1990 map, again indicating that this invasive species has flourished within this time period.

20.3 Wind, Temperature and Humidity

The short duration wind data record indicates that wind direction is predominantly from the south and south east in Grapevine Gut and Wells Gut, however there are variations which are controlled by topography.

Annual average temperatures in the study area ranged between 16oC (IB03GVG) and 17.5oC (IB02PG) and varied 1.5oC across all monitoring locations at any given time. Wells Gut was observed to maintain a more constant temperature at all elevations and through all seasons than Grapevine Gut. The data indicate that humidity increases across the Peaks from south east to north west following the prevailing wind direction. Grapevine Gut was observed to have a more consistent humidity across the seasons.

Differences in temperature and humidity within each sub-catchment are likely to be influenced by plant morphology, the proportion of plant species in each Gut and differences in slope orientation, topography and wind speed. Theses micro-climate differences will affect plant photosynthesis, transpiration, germination and mortality alongside soil type, decomposition and soil nutrients.

The 18-month wind, temperature and humidity data set indicate that there are differences in micro- climate between each Gut. These differences could be promoting growth or mortality of different plant species and influencing the success or failure of invasive and endemic plants within the study area. More detailed microclimate studies would be needed to confirm the key influences on micro- climate and plant growth within each sub-catchment. However, the continued restoration of the Peaks NCA and study area will play a part in modifying the micro-climate and soil conditions over time by re-introducing plant species that naturally habit St Helena’s montane cloud forest.

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20.4 Rainfall and Mist

The mist and rainfall monitoring data indicate that for 2017, mist comprised 60% of total precipitation within the study area.

When compared to the 2017 rainfall record at Bottom Woods Met Station, total rainfall in Grapevine Gut is 3.9 times higher than recorded at Bottom Woods in 2017. The Peaks Nursery rainfall is 2.3 times higher than Bottom Woods for the same period. Rainfall recorded at Grapevine Gut is 1.5 times higher than recorded at the Peaks Nursery in 2017.

During the winter months mist recorded in Wells Gut was 1.3 times greater than rainfall, but in the summer, mist was 2.1 times greater than rainfall. These seasonal differences indicate that during the summer months, mist plays a far greater role in bringing precipitation to the cloud forest and island than direct rainfall, supporting habitat growth, spring/seep flows, groundwater recharge and surface water flows.

The mist and rainfall data record also indicate that mist increases with an increase in elevation and forms at a higher elevation on the windward (south east) side of the Peaks in Perkins Gut than on the leeward side in Wells Gut. These measurements support historic records which show that the cloud forest extending down the flanks of the Peaks on the leeward side to 680mASL at Halley’s Mount, adjacent to the study area. A longer data set would assist in the validation of all the mist and rainfall relationships.

20.5 Soil Moisture

Soil moisture beneath the flax maintained a relatively constant saturation throughout the monitoring period, whereas soil moisture between the fern thicket varied greatly. Fern thicket soil moisture responds to the February 2017 rainfall event during the same period of time as the flax, however soil moisture is seen to increase over a longer period of time reaching its maximum on 28th March 2017, 39 days after the highest recorded rainfall. This longer-term increase could be indicative of a more organic rich soil wetting up (such as a peat).

The soil moisture data indicate that habitat responses can be different when exposed to similar climatic conditions. Hypothetically, this may mean that the tree fern thicket allows for more storage and release of water to the catchment than the flax habitat. This may be particularly true when there are larger rainfall events where the flax may be more likely to let water run off quickly showing a more flashy response. In contrast, the tree fern thickets are capable of water uptake and then a slower release over a longer period. A longer-term data set would be required to confirm if this relationship truly exists.

20.6 Stream Flows

There are no long-term records of continuous stream or spring flow on the island, which is surprising given the reliance of the island on springs and stream flow for potable water supply. There are no well-defined stream channels in the upper reaches of the sub-catchments.

Comparison of stream flows and raw water abstraction in Grapevine Gut and reservoir indicate that between November 2016 and October 2017, Grapevine Gut reservoir abstractions were 22% total

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Total abstraction from Wells Gut comprises 18% of calculated flows indicating that abstraction within the sub-catchment is not detrimental to surface water flows. Flows at the v-notch weir are 76% of total sub-catchment flows. It is not clear if all flows in Wells Gut and Byrons Gut above SW02WG and SW01BG are intercepted, or if water held in storage within the peat provides sub-surface flow which may reach the lower half of the catchment which flows over the v-notch weir.

Stream flows at the v-notch weir in Wells Gut (SW03WG) show irregular flow when compared against precipitation. The irregularity of daily flows during times of precipitation indicates that the Wells Gut catchment responds rapidly to rainfall and mist. Steep recessions in December, January, February and March indicate reduced storage within the sub-catchment. Conversely, later data during the winter season indicates a more even pattern to flows during periods of rainfall, with a sustained increase in flow rate between May and September 2017.

The data suggest that due to a prolonged period of dry weather during the drought, the Wells Gut sub-catchment is shedding rainwater more quickly during short periods of rainfall and the high rainfall event in February rainfall. However later data between May and September 2017 suggests that the catchment storage has improved. This change may be due to the peaty soil within the Peaks wetting up over a 6-month period after the prolonged period of dry weather during the drought.

The difference in total flows between Grapevine Gut and Wells Gut may also be due to the underlying geology where one sub-catchment loses more water to percolation (groundwater recharge) than the other. This may explain the significant difference in flows within the Grapevine Gut compared to the water balance, as during the investigation the flows observed in the Gut were significantly smaller than the surplus water in the calculated water balance.

20.7 Potential Evapotranspiration

Previous calculations of PE have reported an average of 862mm PE per annum at Hutts, with average annual rainfall of 1,021mm (PE 84% of rainfall). PE for a 12-month period between November 2016 and October 2017 has been calculated as 2,052mm with combined mist and rainfall of 6,180mm (PE i33% of average annual precipitation). If only rainfall is considered PE is 84% of average annual precipitation, similar to that recorded in earlier studies at Hutts Gate.

The earlier calculations of PE have only considered rainfall at Hutts Gate, which may explain why PE calculated for the Peaks is 2.3 times greater. PE exceeds combined rainfall and mist for only 1 month during January 2017. If only rainfall is considered, then PE exceeds rainfall 6 out of 10 months.

20.8 Water Balance

Water balances indicate that Grapevine Guts catchment area is 32% larger than Wells Gut, but stream flows are only 1.9% of total flows measured in Wells Gut.

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The larger Grapevine Gut sub-catchment shows a significant surplus in the water balance as calculated stream flows are so small. The sub-catchment is also shown to have a water surplus if mist is excluded from the calculation. The smaller Wells Gut sub-catchment shows a surplus in the water balance, however there is a significant deficit if mist is excluded from the balance.

Rainfall and mist within each sub-catchment may provide recharge to aquifers beneath the Peaks NCA, accounting for the surplus water in each water balance. Differences in vegetation within each sub- catchment may also play a part in the water balances. Wells Gut has 15% of its land area as tree fern thicket, whereas Grapevine Gut has only 5%. Soils beneath the tree fern thicket in the cloud forest are appreciably more organic and over the millennia have formed a rich, deep peaty soil. Given the larger area of tree fern thicket in Wells Gut, it is likely that the area covered by a rich peat soil is larger than Grapevine Gut (which has been impacted more by forestation and invasive plant species). This peaty soil provides not only a good carbon sink but also provides good water retention, soaking up rainfall and releasing it slowly from storage supporting stream flows and vegetation. A sub-catchment which is underlain by a perched aquifer feeding springs with overlying peaty soil will provide a good source of water, as groundwater recharge will provide the spring baseflow whilst the peat provides a slow release source of water to the vegetation and streams.

Due to the limited data available for the island and within the sub-catchments, the relationship between geology, soils, rainfall recharge, dry weather flow and spring flows cannot be more accurately assessed. The degree to which topographical and geological features influence stream flows cannot be quantified within each sub-catchment based on the available data, however the available data indicate that the sub-catchment with the larger proportion of endemic cloud forest vegetation (and associated peat soil) supports a far higher annual stream flow.

20.9 Climate Change

The climate change assessment indicates that temperatures in the region are rising and will increase an average of 2oC by 2099. Changes in rainfall are predicted to fluctuate between -2.50mm and +2.05mm per month by 2099, with the number of consecutive dry days increasing up to 48% on the present day.

Key climate change risks for the study area and islands water supply are:

1. Changes to air and temperature disrupting wind and rainfall patters e.g. rainfall is more erratic with longer drier period and more short high intensity rainfall events; 2. Increased risk of soil erosion due to high intensity rainfall events and high wind 3. Increase in air temperature (median 2°C) with slight decrease in rainfall; 4. Reduced rainfall (and mist) has negative impact on local water supplies; 5. Altitudinal shifts in vegetation zones; and 6. Increase in ecological imbalances.

The limited data we have presented above suggest that endemic native habitats are potentially more resilient to climate change than the introduced vegetation. This ecological resilience will be an important factor in determining how St Helena’s ecosystems respond to any changes in climate and ensuring a sustainable water supply. Unfortunately, we cannot wait to find out; a long-term commitment to genuinely restoring larger areas of the cloud forest habitat to its former extent is

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An assessment of climate change impacts on the island’s water supply suggests that whilst there is no material change in available water within each sub-catchment due to climate change, the underlying message is that the way the island receives its water is going to change. The number and distribution of wet and dry days will change along with rainfall intensity, consequently water infrastructure will need to have capacity to retain larger volumes of water which are drawn down over a longer period, rather than being “topped up” on a regular basis by more regular rainfall. Alternatively, encouraging a larger area of cloud forest and developing a richer peaty subsoil in the Peaks will help even out the islands water supply by holding back rainfall runoff, and releasing water in a slower less “flashy” flow.

20.10 Cloud Forest Restoration

Based on the evidence of mist data collected between October 2016 and October 2017, the suggested restoration plan is based on the likelihood of mist forming and being intercepted by endemic plants in the Peaks. This limits cloud forest restoration above the 690mASL contour in Wells Gut and Grapevine Gut (close to the 680mASL contour of Halley’s Mount). An additional 25m buffer below this contour should be considered to manage invasive species and allow for any climate change adaptation. Based on the 690m contour, the total area of habitat that could be restored is 16ha (excluding areas already populated by cloud forest endemic plants).

The climate change assessment identified altitudinal shifts in the vegetation zone as being critical for the endemic plants and invertebrates within Grapevine Gut and Wells Gut, as a shift in the vegetation zone could significantly reduce the size of the cloud forest. As part of a wider island climate change mitigation strategy, restoring the cloud forest in both sub-catchments above the 690m contour would increase the cloud forest habitat in the study area from 3.6ha to 19.7ha (over 400% increase on current levels) and increase the islands total cloud forest habitat by 40%, providing additional climate change resilience.

20.11 Ecosystems Services Assessment

Key ecosystem services provided by cloud forest in the study area comprise the supply of 38% of the islands water supply, water for drinking, washing and production of food, habitat for over 1/3 of all UK mainland and Overseas Territory endemic species and a significant eco-tourism destination for the island.

Based on restoration costs, data indicate that 1m3 additional water for public water supply via mist capture will cost in the region of £58/m3. Ongoing costs of water should be significantly reduced as they will be limited to habitat maintenance.

Costs for cloud forest restoration for an equivalent volume of water are 55% higher when compared with construction of storage at Hutts Gate 2 reservoir. However, the restoration of the cloud forest for water supply also has benefits for ecosystem services.

The costs of restoring both catchments to the 690m contour is estimated to be in the region of £18.6 million. Funding a cloud forest restoration scheme on St Helena represents only 4% of the annual DEFRA biodiversity budget (2016 to 2017), presenting a very cost effective method of increasing

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20.12 A Future Source of Water

The 20-Year Water Resource Masterplan outlines a preferred water supply development approach through rainwater harvesting. The island obtains water from springs as stream flow and through limited groundwater abstraction. Both of these methods abstract water from the same amount of mist and rainfall. Groundwater abstraction is a valid option, but a large increase in groundwater abstraction would need an improved understanding of the islands hydrogeology to understand mechanisms of aquifer recharge to accurately determine the longevity of the island’s aquifers.

The study has shown that mist is a significant source of water within each sub-catchment, is the dominant source of precipitation for the island during the summer months and restoration of the islands cloud forest can improve the amount of water available for public water consumption. Mist capture provides an opportunity of increasing the amount of water that reaches the island throughout the year, whilst also improving a significant source of rare biodiversity and habitat. There are identifiable benefits for drinking water, food production, ecotourism, public health and mitigating the effects of climate change.

Costs of restoring cloud forest indicate that bringing additional water to the island through improvements in mist capture is initially more expensive than the costs of water storage infrastructure. Planning for these costs will require a change in thinking across Government, the private sector and society as water is considered a free commodity, with only the costs of abstraction, storage, treatment and distribution being considered. The calculation of the cost/benefits to society of securing habitat for up to 1/3 of the UK’s endemic biodiversity is almost impossible.

To ensure long-term water security, a more holistic approach is needed with consideration of the inputs to the water supply (rain), it’s pathway through ecosystems (cloud forest), storage in reservoirs and efficient supply to end users. With the exception of rain, efficiency can be increased at all these levels; fixing leaks in supply pipes, increased reservoir storage and increased cloud forest for capture more mist. Adopting such an ecosystem approach to costs and St Helena’s water cycle would be a very progressive and forward-thinking attitude to water security.

20.13 Recommendations

It is recommended that:

• Permanent surface water monitoring equipment should be installed in all water supply catchments on St Helena to measure stream flows, baseflow and to develop minimum low flows for supporting surface water habitats and ecosystems. The study confirmed that there were no long-term records of continuous stream or spring flow on the island, which is surprising given the reliance of the island on springs and stream flow for potable water supply;

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• Mist, rainfall and stream flow measurements continue within Wells Gut and Grapevine Gut to support accurate long-term interpretation of sub-catchment climate and hydrology and to update the water balance; • A hydrogeology investigation of the island (including the Peaks) is completed to fully understand the relationship between geology, soils, rainfall recharge, dry weather flow and spring flows; • Grapevine Gut reservoir inflows and outflows should be measured using in-line flow meters to accurately record the reservoir water balance;

• Water infrastructure design and construction schemes need to ensure that built infrastructure measurements are accurately recorded (as-built drawings) and retained for future reference;

• Capital investment to reduce leakage in the water distribution network needs to continue to further improve the efficient use of the islands limited water resources;

• Treated water data and billed water consumption data are checked regularly to assess losses from leakage and to calculate accurate water consumption values (l/p/d) for comparison with other nations and to track water efficiency targets;

• A trial cloud forest restoration programme is agreed between Connect, SHG and stakeholders in Wells Gut (including Byrons Gut), to monitor and measure changes in stream flow associated with cloud forest restoration. The data will be used to accurately quantify the additional water that mist capture through restored cloud forest brings to the island and update costs of restoration;

• Future restoration programmes select the best available technique to restore the cloud forest, limit the potential for soil erosion during restoration of habitat and look for opportunities to limiting time consuming and costly habitat maintenance;

• Drones are used to monitor habitat change and the management of conservation habitat; and • JNCC climate change guiding principles for biodiversity conservation are used as a climate change mitigation and adaptation check-list for all proposed development and conservation work on the island.

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Holder, C. D. (2006) ‘The hydrological significance of cloud forests in the Sierra de las Minas Biosphere Reserve, Guatemala’, Geoforum, 37(1), pp. 82–93. doi: 10.1016/j.geoforum.2004.06.008.

Howard, G., Jamie, B. and World Health Organisation (2003) Domestic Water Quantity , Service Level and Health. doi: 10.1128/JB.187.23.8156. iMC Worldwide (2014) Climate Change Factsheet: Climate Data and Requirements for St Helena.

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Lambdon, P. and Darlow, A. (2012) Flowering Plants and Ferns of St Helena. Pices Publlications. Available at: https://www.summerfieldbooks.com/flowering-plants-and-ferns-of-st-helena~3664 (Accessed: 19 March 2018).

Lawton, R. O. et al. (2001) ‘Climatic impact of tropical lowland deforestation on nearby montane cloud forests’, Science. American Association for the Advancement of Science, 294(5542), pp. 584–587. doi: 10.1126/science.1062459.

Malan, L. (EMD) and Darlow, A. (Independant) (2018) Securing St Helena’s Rare Cloud Forest Trees and Associated Invertebrates.

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Mlambo, R. et al. (2017) ‘Structure from motion (SfM) photogrammetry with drone data: A low cost method for monitoring greenhouse gas emissions from forests in developing countries’, Forests. Multidisciplinary Digital Publishing Institute, 8(3), p. 68. doi: 10.3390/f8030068.

Paneque-Gálvez, J. et al. (2014) ‘Small Drones for Community-Based Forest Monitoring: An Assessment of Their Feasibility and Potential in Tropical Areas’, Forests. Multidisciplinary Digital Publishing Institute, 5(6), pp. 1481–1507. doi: 10.3390/f5061481.

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‘Technical Review of Hutts Gate and Longwood Water Systems SHG Jan 1981.pdf’ (no date).

University of Cape Town (2018) Future Climate Projections -St Helena, Web site. Available at: http://cip.csag.uct.ac.za/webclient2/datasets/africa-merged-cmip5/#nodes/cmip5- anomalies?folder_id=33&extent=99983.

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Zahawi, R. A. et al. (2015) ‘Using lightweight unmanned aerial vehicles to monitor tropical forest recovery’, Biological Conservation. Elsevier, 186, pp. 287–295. doi: 10.1016/J.BIOCON.2015.03.031.

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APPENDIX A: PROJECT TASKS AND PROGRAMME

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Table 32: Project Partner Roles, Responsibilities and Deliverables

Organisation Name Role Responsibilities Deliverables

ENRD Trevor Graham Project Lead Project governance and formal reporting of • Submission of all reports to Darwin / Derek Henry progress to Darwin Plus. Plus; • Approval of purchase orders and invoices.

Ben Sansom Project Manager. Drafting of all project management documents, • Project management; Environment and reports and financial statements. Project • Desk study; Water Resources. programme and budget tracking. Field monitoring, • Equipment procurement; desk study, water balance, interpretive reporting. • Monitoring network design and installation; • Aerial survey; • Water features survey; • Monitoring data interpretation Arctium (water and climate data); • Water balance; • Final report.

Climate Change and Desk study research and reporting, field • Desk study research and reporting; Environment monitoring and climate change assessment. • Field monitoring; • Monitoring data interpretation (water and climate data); • Interpretive reporting; • Climate Change assessment.

Mike Jervois Terrestrial Lead ecologist completing botanical surveys of • Desk study; Conservation the catchments and co-ordination with Lourens • Botanical surveys of study area Malan (DPLUS029) to share botanical data and aerial survey support; between projects. • Monitoring network design support; EMD • Interpretation of botanical data; • Outline cloud forest restoration plan.

Samantha Environmental GIS Project lead for all remote sensing and GIS • Digital Elevation Model; Cherrett and Remote Sensing elements. Co-ordination with DPLUS052 which

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will collect new remote sensing data for Saint • Remote sensing data collation and Helena which can be used in this project. interpretation; • Mapping field data; • Report figures.

Connect Saint Helena Leon deWet Water Resource Management of Connect Saint Helena project • Baseline data collation from Manager – Saint staff. Design of water resource monitoring Connect archives; Helena network, monthly and quarterly collection of field • Monitoring network design and data, water balance support. installation; • Water features surveys support; • Monthly and quarterly collection of field data, collation of data and graphing; • Water balance.

CEH Dr Alan Grey Plant Ecology and Technical advice and support to the project. • Desk study; Climate Change Identification of technical assistance colleagues in • Equipment procurement advice; Technical Advisor CEH can provide. • Monitoring network design; • Interpretation of climate and botanical data; • Water balance; • Technical support to project team.

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The project programme is presented in Table 33.

Table 33: Project Programme

Revised Programme (2018 to 2019)

Activity No of Year 1 Year 2 Year 3 Months A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S Output Desk Study

1 1.1 Data collation at CEH 2

and Kew 1.2 ANRD data collation 1 1.3 Reporting 2 Output Monitoring Network 2 and Baseline Data Collection 2.1 Vegetation surveys in 3

sub-catchments 2.2 Remote sensing and 3

aerial surveys 2.3 Installation of surface 2 water and groundwater monitoring equipment 2.4 Monthly and quarterly 16 monitoring or surface

water and groundwater – minimum 12 months Output Microclimate

3 Assessment 3.1 Installation of meteorological monitoring equipment

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Activity No of Year 1 Year 2 Year 3 Months A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S 3.2 Collection of 16 meteorology data over a minimum 12 months 3.3 Collection of humidity 16 data from tiny-tags

over a minimum of 12 months Output Water Balance and 4 Interpretation

4.1 Water balance 4

calculation 4.2 Interpretation of water 3

balance Output Reporting and 5 Outline Restoration Plan 5.1 Collation and 10

interpretation of data 5.2 Reporting plus 8 ecosystems services

assessment and outline restoration plan.

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APPENDIX B: SHG RESILIENCE FORUM DROUGHT NOTICES 2016 TO 2017

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NO SIGNIFICANT RAIN FORECAST

Posted on October 25, 2016 by St Helena Government | Leave a reply

RESIDENTS URGED TO LIMIT WATER CONSUMPTION

St Helena Resilience Forum urgently advises the public to reduce their water consumption. The Forum is responsible for monitoring and managing risks that can affect the safety of the community as a whole, it comprises senior officers from the Emergency Services, SHG, CONNECT and SURE.

As exceptionally dry weather continues – with no significant rainfall forecast over the coming weeks – domestic water levels on St Helena have reached dangerously low levels with Island reservoirs gradually emptying.

St Helena residents, businesses and people who use water for agricultural purposes are therefore urged to exercise great care and restraint when using water.

CEO of Connect Saint Helena Ltd, Barry Hubbard, explains:

“The water levels on St Helena are dangerously low and if we don’t have any substantial rainfall soon, we will reach a very serious situation.

“We have experienced droughts in the past but these have been cases where there has been water on the Island, but in the wrong place. This year we have no other available water on St Helena.

“Connect has closely monitored the situation, followed all protocols and gathered and transferred water where possible. But the bottom line is that we can’t control the weather. The fact is this year we are experiencing very low levels of rainfall and there is a good chance this dry weather will continue.”

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Rainfall data since 2001 – collected from the Met Office site in Bottom Woods – highlights a serious and significant drop in our monthly rain:

The figures show that rainfall this year has been significantly lower than even during the drought in 2013.

With approximately only 15mm of rainfall received so far this October it is likely that the problem will continue in the short to medium term.

As the festive season approaches and more people arrive on-Island, there will be even higher demand for water – but we must reduce our consumption. St Helena residents are reminded that this is an Island-wide shortage and it is everyone’s responsibility to manage the situation and to take great care in using this precious resource.

The Resilience Forum added:

“If consumption continues at the current level, or increases, Connect will have no option but to place further restrictions on people’s use of water. This could result in consumers only being allowed a certain volume of water each day.

“Connect does not want to do this but it is becoming a serious possibility if we do not limit our usage now to essential needs only. On a household level, just monitoring how much water you’re using each day and making sure you cut this down, will help. An Island-wide shortage affects everyone and we must all do our part.”

Connect is doing all it can to sustain available resources and gather and transfer water where possible. But this will not solve the main problem, which is lack of rain.

This situation is being taken very seriously by the St Helena Resilience Forum, which will keep the public informed through frequent radio rainfall and consumption data, together with advice on how to limit your consumption.

St Helena Resilience Forum

25 October 2016

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ST HELENA WATER LEVELS STILL SERIOUSLY LOW

Posted on November 4, 2016 by St Helena Government | Leave a reply

RESIDENTS URGED TO FURTHER REDUCE THEIR USE

The St Helena Resilience Forum today confirmed that water resources on St Helena remain dangerously stretched.

The low levels of rainfall during September and October this year has significantly impacted on water volume, surface runoff and replenishment of the springs. The amount of water we are able to collect daily is now only 80% of the amount that is being used daily. That is even when taking into account that over the past two months, consumption has reduced by around 10%.

This still leaves a significant shortfall which means that water stocks are continuing to diminish.

Connect continues to move water by bowsers and pipelines to areas where it is most needed, but it remains the case that there is still less water coming into the network than is needed to meet demand. Essentially we are using more water than we are collecting.

St Helena residents, businesses and people who use water for agricultural purposes are urged to exercise great care and restraint when using water.

If we can achieve a further 10% reduction in our consumption, the amount of water will remain at current levels. Without such a reduction, our stock will continue to dwindle. This means that Connect will have no option but to place further restrictions on people’s use of water.

Connect does not want to do this but it is becoming a serious possibility if we do not now restrict our usage to essential needs only.

As we move into the weekend, residents are reminded that this is an Island-wide shortage and it is everyone’s responsibility to manage the situation and to take great care in using this precious resource. If you see anyone using water irresponsibly then please inform Connect.

This situation is being taken very seriously by the St Helena Resilience Forum, which will keep the public informed through frequent updates on consumption versus collection.

Leaflets and posters containing water saving tips have also been distributed to local outlets and public buildings and people are encouraged to pick up a leaflet to see how they can limit their water use.

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Notice to Commercial Agricultural Consumers

You should be aware that water usage exemptions will not be renewed automatically. When your exemption has expired you need to resubmit an application to Connect.

Connect will then prioritise these applications, based on cultivated status of agricultural land.

St Helena Resilience Forum

4 November 2016

ST HELENA WATER LEVELS SERIOUSLY LOW

Posted on November 8, 2016 by St Helena Government | Leave a reply

WEEKEND RAINFALL NOT ENOUGH

CONNECT TO IMPOSE FURTHER RESTRICTIONS

Despite some rainfall over the weekend and last evening, water resources on St Helena remain dangerously stretched.

Connect will this week publish an Island-wide legal notice restricting the use of water for essential purposes only from Monday 14 November 2016.

This is defined as using water for drinking, cooking and personal washing only.

In addition, all Exemption Notices previously issued are now expired and no longer valid.

On Friday 4 November 2016, Island reservoirs contained 11,278 cubic metres of water – just 9.3% of the total capacity. The total reservoir capacity on St Helena is around 121,000 cubic metres.

There are other sources of water – tanks, boreholes & springs – but the reservoirs are the most significant and visible, with levels easy to measure. They are also less vulnerable to daily fluctuation.

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Over the next few days we will see some of the rainfall run-off make its way to the reservoirs – but as welcome as the rain was it is nowhere near enough to get us through the summer. Until the reservoirs reach at least 50% full, we remain in a critical situation.

Regular updates on reservoir levels will be issued to the public.

In the meantime, St Helena residents, businesses and people who use water for agriculture are urged to exercise great care and restraint when using water.

If we can achieve a further 10% reduction in our consumption, the amount of water will remain at current levels. Without such a reduction, our stock will continue to dwindle.

Residents are reminded that this is an Island-wide shortage and it is everyone’s responsibility to manage the situation and to take great care in using this precious resource. If you see anyone using water irresponsibly then please inform Connect.

Leaflets and posters containing water saving tips have been distributed to local shops and public buildings and people are encouraged to pick up a leaflet to see how they can limit their water use.

Connect has received a positive response to its advertisement for temporary contract drivers – and commenced 24-hour bowser operations from today Tuesday, 8 November 2016.

St Helena Resilience Forum

8 November 2016

ST HELENA WATER LEVELS STILL SERIOUSLY LOW

Posted on November 11, 2016 by St Helena Government | Leave a reply

Despite some recent rainfall, water resources on St Helena remain dangerously stretched.

As welcome as the rain was, reservoir levels have only increased by around 1%. This clearly shows that we will need a longer period of heavy rain for water levels to return to normal. Until the reservoirs reach at least 50% full, we remain in a critical situation.

Consumption levels have not significantly decreased and St Helena residents are urged to do more to reduce their use. Connect is continuing to bowser water 24/7 to ensure that everyone has access to water, but there remains an average 28 cubic metre daily shortfall. As the Island continues to use more water than is being replenished naturally, the stored water will continue to reduce. If things do not change, we will eventually run out.

Governor Lisa Phillips said:

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“We are managing, but as a community we need to cut our consumption of water by 10%. This means that we will only use as much as we can put into the system so that we are in balance. I am doing my bit, and every little counts. So please pick up a water saving leaflet in the shops and public buildings and see how you can join me in reducing your water use.”

Connect has this week published an Island-wide legal notice restricting the use of water to essential purposes only – drinking, cooking and personal washing . Personal washing is washing yourself, clothes and bedding etc in order to maintain your personal cleanliness and hygiene. These revised restrictions are effective from Monday 14 November 2016.

Exemption Notices that expired on 31 October 2016 are NOT automatically renewed. An application must be made for a fresh exemption which will be assessed against the further restrictions.

Residents are reminded that this is an Island-wide shortage and it is everyone’s responsibility to manage the situation and to take great care in using this precious resource. If you see anyone using water irresponsibly then please inform Connect.

A Press Conference with Connect and SHG representatives will be held on Wednesday 16 November 2016. Further details will be issued next week.

St Helena Resilience Forum

11 November 2016

UPDATE ON ST HELENA WATER LEVELS

Posted on November 15, 2016 by St Helena Government | Leave a reply

CONSUMPTION DOWN BY 4.5% BUT WATER RESOURCES REMAIN STRETCHED

Water resources on St Helena remain seriously low.

On Friday 11 November 2016, Island reservoir levels had increased to 13,021 cubic metres – around 10.9% of total capacity. This increase is largely attributed to the rain run-off from the previous weekend. But as welcome as this rain was, it gives an indication of just how much rain we need in order to increase reservoir levels.

Until the reservoirs reach at least 50% full, we remain in a critical situation.

It is pleasing that water consumption last week was down by around 4.5% on the previous week – and residents are thanked for their cooperation. But St Helena water levels are still seriously low so please continue to exercise great care and restraint when using water.

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With a slight improvement in stored water and a slight decrease in consumption, the immediate situation remains stable. But, we cannot be complacent as we may not have the benefit of further rain before the summer. To maintain the balance between water coming into the system and water being used, Connect is continuing to bowser water from other sources. But we all need to continue to do our bit and reduce our use. If you see anyone using water irresponsibly then please inform Connect.

The public is reminded of the Island-wide Legal Notice now in place which restricts the use of water for essential purposes only – defined as drinking, cooking and personal washing. Personal washing is washing yourself, clothes and bedding etc in order to maintain your personal cleanliness.

In addition, Exemption Notices which expired on 31 October 2016 are not automatically renewed. Anyone requiring an Exemption Notice must apply for reassessment.

Leaflets and posters containing water saving tips have been distributed to local shops and public buildings and people are encouraged to pick up a leaflet to see how they can limit their water use.

St Helena Resilience Forum

15 November 2016

ST HELENA WATER SHORTAGE 2016

Posted on November 21, 2016 by St Helena Government | Leave a reply

STATEMENT FROM THE UK MET OFFICE

St Helena is currently experiencing unusual and exceptionally dry weather this year. In fact, rainfall so far in 2016 has been significantly lower than even during the drought in 2013. That is why the Island is currently suffering a serious water shortage.

As the dry weather continues – with no significant rainfall forecast over the coming weeks – the UK MET Office has issued the following statement outlining some of the factors which may be contributing to St Helena’s drought-like conditions this year:

“St Helena sits close to the northern edge of a large area of high pressure called the ‘South Atlantic Anticyclone’. High pressure brings dry weather because the air is not able to rise to form clouds and rain.

“The South Atlantic Anticyclone shifts in position and strength over time, and it is likely that these changes in the anticyclone drive the annual variability in rainfall across St Helena. There

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“Without an extensive research programme it is not possible for us to be sure which one factor is responsible for the reduction in rainfall in 2016, and it is highly likely that this results from a combination of factors coming together.

“Looking ahead, are we likely to continue the drought? November, December and January are normally very dry months on St Helena. The Met Office and European seasonal forecast models show that close-to or below-average rainfall is likely over the coming three months. There is a chance therefore that the water shortage on St Helena may continue into the start of 2017.”

With this in mind, St Helena residents, businesses and people who use water for agriculture are again reminded to exercise great care and restraint when using water. Every drop counts, every action counts – please do your bit.

This situation is being taken very seriously by the St Helena Resilience Forum, which will keep the public informed through frequent updates on consumption versus collection.

Leaflets and posters containing water saving tips have also been distributed to local shops and public buildings and people are encouraged to pick up a leaflet to see how they can limit their water use.

SHG

21 November 2016

UPDATE ON ST HELENA WATER LEVELS

Posted on November 22, 2016 by St Helena Government | Leave a reply

RESERVOIRS UP SLIGHTLY BUT SO IS CONSUMPTION

On Friday 18 November 2016, Island reservoir levels had increased to 14,551 cubic metres – around 12% of total capacity. This increase is largely attributed to run-off from recent rainfall. Again, as welcome as this rain was, we still need much more in order to increase reservoir levels.

Until the reservoirs reach at least 50% full, St Helena remains in a critical situation.

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Unfortunately, water consumption last week crept up slightly from around 900 cubic metres a day to just over 1000 cubic metres. With this in mind, all St Helena residents are again reminded to exercise great care and restraint when using water. Every drop counts, every action counts – please do your bit.

To maintain the balance between water coming into the system and water being used, Connect is continuing to bowser water from other sources. But we all need to continue to do our bit and reduce our use. If you see anyone using water irresponsibly then please inform Connect.

The public is reminded of the Island-wide Legal Notice now in place which restricts the use of water for essential purposes only – defined as drinking, cooking and personal washing. Personal washing is washing yourself, clothes and bedding etc in order to maintain your personal cleanliness. The Legal Notice applies to all water sources Island-wide, which includes The Run water and private borehole and spring water.

The Legal Notice prohibits use of all water sources, except ‘grey’ (recycled) water. Rain water which is captured from roofs into water butts is classed as ‘grey’ water and may be used for any purpose without an Exemption Notice.

Although these legal restrictions apply universally, Connect can grant Exemptions on a case- by-case basis. Anyone who wishes to use The Run or other private sources of water for any of the prohibited purposes must apply for an exemption.

Essentially, if you want to use water for anything other than personal washing, cooking and drinking, you must apply for an Exemption Notice.

Exemption Notices which expired on 31 October 2016 are not automatically renewed. Anyone requiring an exemption must apply for reassessment.

Leaflets and posters containing water saving tips have been distributed to local shops and public buildings and people are encouraged to pick up a leaflet to see how they can limit their water use.

Members of the public are also advised that a transcript of the Press Conference held on Wednesday 16 November 2016 is now available on the publications page of the SHG website at: http://www.sainthelena.gov.sh/publications/

RESERVOIR LEVELS SLIGHTLY UP

Posted on November 25, 2016 by St Helena Government | Leave a reply

BUT STILL NOT ENOUGH

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Island reservoir levels are up to around 13% of total capacity. This is good news, but 13% of our current reserves is not going to see us through the summer.

As highlighted by the UK Met Office this week, weather patterns worldwide are changing and St Helena is not the only place suffering from lack of rain. Huge parts of Africa are experiencing droughts and even our neighbours in Cape Town are bound by similar water restrictions to those in-force on St Helena.

Connect Saint Helena Ltd are continuing work on the design and installation of three new water transfer systems and the first of these, from Chubbs Spring to Red Hill, is expected to become operational next week.

Connect intend to continue with their strategy of increasing reservoir capacity to improve the Island’s water security. The more water we have stored, the less vulnerable the Island is to changing weather patterns which are beyond anybody’s control.

The new transfer systems will be a permanent addition to Connect’s water infrastructure, and will provide easy access to water resources which can be drawn upon if stored water is in short supply – either through unpredictable rainfall or other unforeseen events.

The public is reminded that until the reservoirs reach at least 50% full, St Helena remains in a critical situation.

Everyone is therefore reminded to exercise great care and restraint when using water. Every drop counts, every action counts – please do your bit.

Leaflets and posters containing water saving tips have been distributed to local shops and public buildings and people are encouraged to pick up a leaflet to see how they can limit their water use.

St Helena Resilience Forum

25 November 2016

UPDATE ON ST HELENA WATER LEVELS

Posted on November 30, 2016 by St Helena Government | Leave a reply

NO SIGNIFICANT CHANGE

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On Monday 28 November 2016, Island reservoir levels had slightly increased to 15,796 cubic metres – remaining at around 13% of total capacity. Consumption remains at around 1000 cubic metres a day.

The graph below gives a rough indication of Island consumption compared to the same period last year. The indication is that overall we are using less of our precious water resources. With the dry summer months ahead, it is essential that we do not become complacent and we must all try to conserve as much as we can for the coming months.

Compared to 2015, our consumption levels are slightly reduced – but because of our current situation, until we can balance what is going into the system with what is being used – we remain in a critical situation.

Connect Saint Helena Ltd are continuing work on the design and installation of three new water transfer systems and the first of these, from Chubbs Spring to Red Hill, is expected to become operational this week.

Connect intend to continue with their strategy of increasing reservoir capacity to improve the Island’s water security. The more water we have stored, the less vulnerable the Island is to changing weather patterns which are beyond anyone’s control.

The new transfer systems will be a permanent addition to Connect’s water infrastructure, and will provide easy access to water resources which can be drawn upon if stored water is in short supply – either through unpredictable rainfall or other unforeseen events.

Everyone is therefore reminded to exercise great care and restraint when using water. Every drop counts, every action counts – please do your bit.

Exemptions

Members of the public have responded well to the Island-wide Legal Notice and, where appropriate, to applying for relevant Exemption Notices. This process has enabled Connect to better measure and monitor the situation in specific sectors. The public is thanked for their cooperation and vigilance when using water.

The Island-wide Legal Notice restricts the use of water for essential purposes only – defined as drinking, cooking and personal washing. Personal washing is washing yourself, clothes and bedding etc in order to maintain your personal cleanliness. The Legal Notice applies to all water sources Island-wide, which includes The Run water and private borehole and spring water.

The Legal Notice prohibits the use of all water sources, except ‘grey’ (recycled) water. Rain water which is captured from roofs into water butts is classed as ‘grey’ water and may be used for any purpose without an Exemption Notice.

Connect grant Exemptions on a case-by-case basis. Anyone who wishes to use The Run or other private sources of water for any prohibited purpose must apply for an Exemption.

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Essentially, if you want to use water for anything other than personal washing, cooking and drinking, you must apply for an Exemption Notice.

Questions

Anyone wanting to know more about the current water situation and the work being done are encouraged to submit questions to the local media. We will then answer your questions and print them in future updates.

St Helena Resilience Forum

30 November 2016

ST HELENA WATER SHORTAGE 2016

Posted on December 9, 2016 by St Helena Government | Leave a reply

ADDITIONAL DFID FUNDING

With St Helena currently experiencing exceptionally dry weather – rainfall so far in 2016 is significantly lower than even during the drought in 2013 and water stocks are seriously low – DFID has responded positively to an SHG and Connect business case and capital request for additional funding for water infrastructure.

St Helena is suffering the effects of a lack of rainfall throughout 2016 and, with only approximately 14% of reservoir capacity filled, the raw water stock on the Island is dangerously low. Normally at this time of year the reservoirs would have been much better replenished by the winter rains and levels would be significantly higher.

As the dry weather continues – with no significant rain forecast over the coming weeks – it is recognised that access to water is a basic, obvious and reasonable need for St Helena. SHG, supported by DFID, is therefore working with Connect to resolve the current crisis and, in the longer term, to ensure that the Island secures adequate access to fresh water and can manage this finite resource sustainably.

SHG and Connect have together achieved much over the past couple of years and have worked hard to identify the best value for money solutions to the Island’s water needs. This additional funding has now allowed Connect to begin to add water transfer systems to the infrastructure – to supplement emergency bowsering – such as pipes, pumps and associated power supplies. It will also allow for a geohydrological study into deep aquifer drilling and the provision of more boreholes.

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Finally, all St Helena residents are again reminded to exercise great care and restraint when using water. Every drop counts, every action counts – please do your bit.

SHG

9 December 2016

UPDATE ON ST HELENA WATER LEVELS

Posted on December 14, 2016 by St Helena Government | Leave a reply

WATER CONSUMPTION INCREASES

This week has seen a noticeable increase in water consumption on St Helena, with usage back up to around 1000m3 per day.

The recent light rainfall is helping to maintain the water reservoir levels at just less than 13.5% of capacity – but this is not enough. Once we enter the dry summer, there will be no water going into the reservoirs and the levels will fall. It is therefore essential that we do not become complacent and instead continue to conserve as much water as we can for the coming months.

December and January are usually months when consumption increases as we have visiting friends and family on St Helena. Everyone disembarking the RMS is now given a leaflet containing water saving tips to make them aware that our reserves are very low.

Everyone on St Helena is urged to continue using water very sparingly and to please encourage friends, family, visitors and neighbours to do the same. To make sure the reserves last as long as possible, everyone is reminded to exercise great care and restraint when using water. Every drop counts, every action counts – please do your bit.

Consumption levels are indicated below, with the target level shown as an orange line.

Transfer Systems

Connect Saint Helena Ltd is pleased to advise that the new water transfer system from Chubbs Spring to Scotts Mill is now operational. However, there remains a need to bowser water to and from other locations to ensure that everyone has access to water.

Use of ‘Grey’ or Recycled Water

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The Island-wide Legal Notice restricts the use of water to essential purposes only – defined as drinking, cooking and personal washing. Personal washing is washing yourself, clothes and bedding etc in order to maintain your personal cleanliness. The Legal Notice applies to all water sources Island-wide, which includes the Run water and private borehole and spring water.

These legal water restrictions do not apply to ‘Grey’ or recycled water. Water that you collect from your roof into a water butt or recycled washing water may be used for any purpose.

St Helena Resilience Forum

14 December 2016

UPDATE ON ST HELENA WATER LEVELS

Posted on December 20, 2016 by St Helena Government | Leave a reply

KEEP UP YOUR EFFORT TO REDUCE WATER USE

Over the past few months, everyone on St Helena has pulled together and made a significant reduction in our water usage. The graph below shows the reduction in use compared to last year.

Our combined effort means that we have been able to meet demand without too much impact on our very limited stored water resources. However, with no significant rainfall, the stored water resources will soon dwindle if we don’t all keep up our effort. Every drop saved now helps to make the reserves last a little longer. It is therefore essential that we do not become complacent and instead continue to conserve as much water as we can for the coming months.

Please encourage friends, family, visitors and neighbours to do the same. Every drop counts, every action counts – please do your bit.

Consumption in 2016 compared to 2015

December and January are traditionally periods of higher water use as people are at home, relaxing, and may have friends and family visiting. We are anticipating that demand will increase – but if everyone continues to be careful, we are hoping that use will remain lower than last year.

Legal Restrictions

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The Island-wide legal restrictions are still in force so we all have to put up with dirty cars, dirty windows and brown gardens for the foreseeable future. In addition to these legal restrictions, please continue to do all of the little extra things that you have been doing to save every drop – such as recycling water, flushing the toilet less frequently, using less water to wash up etc. The little things all add up to make a big difference.

These legal restrictions do not apply to ‘Grey’ or recycled water. Water that you collect from your roof into a water butt or recycled washing water may be used for any purpose.

St Helena Resilience Forum

20 December 2016

UPDATE ON ST HELENA WATER LEVELS

Posted on January 9, 2017 by St Helena Government | Leave a reply

CONSUMPTION RISING, RESERVOIR LEVELS DOWN SLIGHTLY

St Helena continues to suffer the effects of a lack of rainfall throughout 2016 and, with only approximately 11% of reservoir capacity filled, the raw water stock on the Island remains dangerously low.

As expected, water consumption increased slightly over the festive period. But, now that the holidays are over, it is important that we reduce our water use so that consumption rates can get back to normal.

Consumption Levels To Date

Consumption levels are indicated below, with the target level shown as an orange line.

Over the past few months, everyone on St Helena has pulled together and made a significant reduction in our water use – we are hoping that this will continue in the New Year.

While the recent rains have been welcome, reservoir levels continue to decline and we will need a lot more rain before levels become normal. Currently, we are still experiencing a daily shortfall of 100-200 cubic metres of water a day.

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Therefore, please encourage friends, family, visitors and neighbours to exercise great care and restraint when using water. Every drop counts, every action counts – please do your bit.

Transfer Systems

The new water transfer system from Chubbs Spring to Scotts Mill is operational and the other networks which are partially complete will come on line soon. However, there remains a need to bowser water to and from other locations to ensure that everyone has access to water.

Geohydrological Study

Connect Saint Helena Ltd is pleased to advise that a contract has been awarded to WSP | Parsons Brinkerhoff, to carry out a geohydrological study of St Helena. This study will inform the drilling of trial bore holes on the Island. Further information will be provided as this work progresses.

Legal Restrictions

The Island-wide legal restrictions are still in force. In addition to these legal restrictions, please continue to do all of the little extra things that you have been doing to save every drop – such as recycling water, flushing the toilet less frequently, using less water to wash up etc. The little things all add up to make a big difference.

These legal restrictions do not apply to ‘Grey’ or recycled water. Water that you collect from your roof into a water butt or recycled washing water may be used for any purpose.

St Helena Resilience Forum

6 January 2017

UPDATE ON ST HELENA WATER LEVELS

Posted on January 17, 2017 by St Helena Government | Leave a reply

DO NOT UNDERESTIMATE THE SERIOUSNESS OF OUR WATER SITUATION

Despite recent rain showers, St Helena’s reservoir levels remain at around 11% of total storage capacity. Until the reservoirs reach at least 50% full, St Helena remains in a critical situation.

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Island Reservoir Levels

Over the last week, four days out of seven have seen consumption creep back up to over 1000 cubic metres per day – equivalent to 12,500 full bath tubs.

The target for consumption, to balance what is going into the system, is 800 cubic metres or 10,000 full bath tubs per day. We therefore need a saving of 2,500 bath tubs or 40,000 five litre water bottles per day across the Island.

While we still have water coming out of our taps in our homes, it is easy to forget just how serious our situation is. The reality is that:

1. Our reservoirs are virtually empty 2. Livestock are struggling to find sufficient natural food 3. Water to farmers is being restricted once crops have been harvested

As a community we must continue to cut our consumption and keep it down in everything we do, every single day. Every drop saved now contributes towards conserving our Island’s water reserves a little further.

Every drop counts, every action counts – please do your bit.

Jamestown Swimming Pool

Unwanted water from the Jamestown Swimming Pool has been put to good use by the St Helena Landscape & Ecology Mitigation Programme

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The LEMP, which is responsible for restoring or compensating for habitats and landscapes lost to the Airport footprint, have been using the Swimming Pool water to support ongoing work.

LEMP have used their large water bowser to pump water from the Swimming Pool to transfer around the Island where needed, including to the ANRD and Environmental Management Division’s Nursery and for other agricultural use.

St Helena Resilience Forum

17 January 2017

UPDATE ON ST HELENA WATER LEVELS

Posted on February 8, 2017 by St Helena Government | Leave a reply

RAIN SHOWERS NOT REALLY IMPROVING RESERVOIR LEVELS

DESPITE THE RECENT HEAVY RAIN SHOWERS ON ST HELENA, THESE HAVE NOT MATERIALLY AFFECTED RESERVOIR LEVELS OR SURFACE FLOWS.

AS INDICATED IN THE GRAPH BELOW, FROM THE MONTH OF NOVEMBER 2016 THROUGH TO THE MIDDLE OF JANUARY 2017, THERE HAS BEEN A GRADUAL DOWNWARDS TREND IN ABSTRACTION SURFACE FLOWS, OR IN OTHER WORDS ‘RUN-OFF’ water. WHERE THE SURFACE FLOW SPIKES, THIS INDICATES RAINFALL. HOWEVER THESE SPIKES ARE BRIEF. TO REALLY SEE A DEFINITE INCREASE IN RESERVOIR LEVELS AND ABSTRACTION FLOWS WE NEED A LOT MORE RAIN.

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CEO OF CONNECT SAINT HELENA LTD, BARRY HUBBARD, EXPLAINS:

“We continue to see slowdown in surface water sources with some consumers who have previously enjoyed spring water now requiring mains connections. In mid-January the boreholes provided more water than surface abstraction for the first time ever. Surface water flows will require an extended period of heavy rain before they are restored so the situation is still serious.

“WE URGE ALL ST HELENA RESIDENTS TO NOT BECOME COMPLACENT. THE ISLAND’S water SUPPLIES AND water STORAGE ARE STILL VERY CRITICAL. WE CAN’T STRESS ENOUGH THE NEED TO WORK TOGETHER AS A COMMUNITY IN CUTTING DOWN ON OUR CONSUMPTION AND KEEPING IT DOWN IN EVERYTHING WE DO.”

Every drop counts, every action counts – please do your bit!

St Helena Resilience Forum

8 February 2017

WATER RESTRICTIONS LIFTED

Posted on February 27, 2017 by St Helena Government | Leave a reply

RESERVOIR LEVELS REACH 50% TARGET

The St Helena Resilience Forum and Connect Saint Helena Ltd are today pleased to announce that the formal water restrictions on St Helena have been lifted with immediate effect. This follows a prolonged period of substantive rainfall on St Helena over the last few weeks.

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Island reservoir levels have now reached the 50% target with today’s levels recorded at 62%.

Bowsering of water has now ceased but water is still being pumped via the newly installed transfer systems to ensure everyone has access to water. The borehole exploration programme will also continue to go ahead to ensure that we do not find ourselves in a similar situation in the future.

St Helena has been experiencing a severe water shortage since August 2016 when Connect warned St Helena Government that the Island only had sufficient water to last 45 days. In early September, when the trigger point reached 30 days, formal Island-wide restrictions were put in place. The St Helena Resilience Forum began assisting Connect with the coordination of actions and plans to resolve the water shortage in October at the 20 day trigger mark.

The Resilience Forum recognises that the last six months have been a difficult time for the people of St Helena in light of the water restrictions and in reducing their consumption. Everyone is thanked for their continued cooperation and the important role they have played in conserving and maintaining our Island water stocks.

Formal thanks are also extended to Connect staff, contractors who installed the transfer systems, bowser drivers and to the Warning & Informing sub-group for their ongoing and important work throughout this critical period.

Although the situation is significantly better than it has been, the changing weather patterns provide no certainty of when the next rains will come. People have reduced consumption during the crisis and are encouraged to continue exercising care to preserve this precious resource.

St Helena Resilience Forum

27 February 2017

MET STATION RECORDS HIGHEST RAIN COLLECTION IN SIX YEARS

Posted on March 2, 2017 by St Helena Government | Leave a reply

The MET Station at Bottom Woods has announced that recorded rainfall for the month of February 2017 is the highest it’s been since February 2011.

The data collected last month saw recorded rainfall amount to 115.2mm – just 5.6mm less than was collected six years ago when the recorded number stood at 120.8mm.

The 115.2mm recorded this year is the sixth highest monthly rainfall collection in the Island’s history – the highest being back in February 1979 at 141.6mm. It is also the third highest that has ever been recorded during the month of February.

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The MET Station at Bottom Woods has been collecting climatic data regularly since it was established in October 1976.

All data collected is specific to the MET Station and does not reflect on other Island locations.

SHG 2 March 2017

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APPENDIX C: SPECIES NAMES MENTIONED IN THE TEXT

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Group Common Name Scientific name Author Animals goat Capra aegagrus hircus Linnaeus, 1758 rats Rattus norvegicus Berkenhout, 1769 rats Rattus rattus Linnaeus, 1758 Endemic Plants back cabbage tree Melanodendron integrifolium (Rox.) DC black scale fern Diplazium filamentosum (Roxb.) Cronk brown scale fern Pseudophegopteris dianae (Hook.) Holtt. comb fern Elaphoglossum dimorphum (Hook. & Grev.) Moore Diana’s Peak grass Carex dianae Steud. dogwood Nesohedyotis arborea (Roxb.) Bremek. false gumwood Commidendrum spurium (G.Forst.) DC. filmy fern Hymenophyllum capillaceum Roxb. gumwood trees Commidendrum species he cabbage Pladaroxylon leucadendron (G.Forst.) Hook.f. hen and chick’s fern/plastic fern Asplenium compressum Sw. large bellflower Wahlenbergia linifolia (Roxb.) A.DC. large jellico Berula bracteata (Roxb.) Spalik & S.R.Downie laysback fern Pteris paleacea Roxb. lobelia Trimeris scaevolifolia (Roxb.) Mabb. stringwood Acalypha rubrinervis Cronk tree fern Dicksonia arborescens L'Hér. (J.R.Forst. & G.Forst.) R.Br. ex whitewood Petrobium arboreum Spreng. Introduced Zantedeschia aethiopica Plants arum lily (L.) Spreng. bilberry Physalis peruviana L. bramble/common blackberry Rubus pinnatus Willd. Buddleia Buddleja madagascariensis Lam. Cape yew Podocarpus species Christella Christella dentata (Forssk.) Brownsey & Jermy Cinchona Cinchona species cow grass Paspalum scrobiculatum L. creeping fuscia Fuchsia coccinea Dryand. elderberry Solanum mauritianum Scop. Eucalyptus Eucalyptus species furze/gorse Ulex europaeus L. maritime pine Pinus pinaster Aiton Mexican creeper Antigonon leptopus Hook. & Arn. New Zealand flax Phormium tenax J.R. Forst. & G. Forst. oak Quercus species pheasant tail fern Nephrolepis exaltata (L.) Schott Scotch fir Pinus sylvestris L. spruce fir Picea species St. Helena olive Nesiota elliptica (Roxb.) Hook.f. stone pine Pinus pinea L. wattles Acacia species whiteweed Austroeupatorium inulifolium (Kunth) R.M. King & H. Rob. yam Colocasia esculenta (L.) Schott

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APPENDIX D: DRONE OPERATIONS MANUAL

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Intentionally blank.

See separate Appendix D document.

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APPENDIX E: TEMPLATE DRONE OPERATIONS MANUAL

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Intentionally blank.

See separate Appendix E document.

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APPENDIX F: FLIGHT PLANS

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Intentionally blank.

See separate Appendix F document.

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APPENDIX G: MONITORING MANUAL V1.1

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Intentionally blank.

See separate Appendix G document.

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