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 ............................................................................................................