Ecological water requirements of the Lower De Grey

Department of Water Looking after all our water needs 168 St Georges Terrace, , Western Environmental water report series PO Box K822 Perth 6842 Phone: 08 6364 7600 Report no. 20 Fax: 08 6364 7601 June 2012 www.water.wa.gov.au

3053–30–0612

Ecological water requirements of the Lower

Department of Water Environmental water report series Report no. 20 June 2012 Department of Water Disclaimer 168 St Georges Terrace This document has been published by the Perth Western Australia 6000 Department of Water. Any representation, Telephone +61 8 6364 7600 statement, opinion or advice expressed or Facsimile +61 8 6364 7601 implied in this publication is made in good National Relay Service 133 677 faith and on the basis that the Department www.water.wa.gov.au of Water and its employees are not liable for any damage or loss whatsoever which © Government of Western Australia may occur as a result of action taken or not taken, as the case may be in respect of any June 2012 representation, statement, opinion or advice referred to herein. Professional advice should be obtained before applying the information This work is copyright. You may download, contained in this document to particular display, print and reproduce this material in circumstances. unaltered form only (retaining this notice) for your personal, non-commercial use or use within your organisation. Apart from any use This publication is available at our website as permitted under the Copyright Act 1968, or for those with all other rights are reserved. Requests and special needs it can be made available in inquiries concerning reproduction and rights alternative formats such as audio, large print, should be addressed to the Department or Braille. of Water.

ISSN 1833-6582 (print) ISSN 1833-6590 (online)

ISBN 978-1-921789-78-6 (print) ISBN 978-1-921789-79-3 (online)

Acknowledgements This report was prepared by Robyn Loomes from the Department of Water’s Environmental Water Planning section. The author acknowledges the input and comments provided by Mike Braimbridge, Michelle Antao, Rob Donohue, Ben Drew and Fiona Lynn. Contents

Ecological water requirements of the Lower De Grey

Summary vii 1 Introduction 1

1.1 Purpose of this document 1

1.2 Study area 3 2 Groundwater-dependent ecosystems 10

2.1 Groundwater-dependent ecosystems in the De Grey study area 10

2.2 Hydro-ecological linkages 13 3 Approach to determining ecological water requirements 17

3.1 Overview 17

3.2 Linkages 17

3.3 How we determined hydrological thresholds 18

3.4 Recharge classes 18

3.5 Site selection 19 4 Ecological water requirements 21

4.1 Developing the ecological water requirements 21

4.2 Recharge classes 31

4.3 Environmental water requirement summary 35 Appendices 39 Shortened forms 57 Glossary 58 References 60

iii Ecological water requirements of the Lower De Grey

Figures

Figure 1 Map showing the lower De Grey River EWR study area 2

Figure 2 Total monthly discharge for the Coolenar Pool gauging station on the De Grey River (1975–2010) 4

Figure 3 River flow analysis showing months of flow and years of low flow (<10 per cent average annual flow) 5

Figure 4 Geological cross-section of lower De Grey River study area 6

Figure 5 Depth to groundwater at selected bores across the study area 6

Figure 6 Bore data recorded across the De Grey River area since 1974, x represents data points 8

Figure 7 Location of Coolenar Pool gauging station, EWR pools, monitoring bores and the Namagoorie borefield 9

Figure 8 EWR sites and estimated depth to groundwater on the lower De Grey River 12

Figure 9 Pool levels and percentiles for (a) Coolenar Pool, (b) J96 Pool, (c) Homestead Pool and (d) Makanykarra Pool 22

Figure 10 Water depth percentiles and 0.45 m depth across pool cross-sections at (a) J96, (b) Homestead and (c) Makanykarra pools 24

Figure 11 Water depth percentiles and 1.5 m depth across pool cross-sections at (a) J96, (b) Homestead and (c) Makanykarra pools 27

Figure 12 Groundwater levels and percentiles at (a) bore 7/04, (b) bore U1, (c) bore 6/04 and (d) bore 9/04 30

Figure 13 Wet season flow probability distributions (1975–2011) 32

Figure 14 Mean and absolute groundwater levels for each recharge class at (a) bore 7/04, (b) bore U1, (c) bore 6/04 and (d) bore 9/04 33

Figure 15 Mean and absolute pool levels for each recharge class at (a) Coolenar Pool, (b) J96 Pool, (c) Homestead Pool and (d) Makanykarra Pool 34

iv Ecological water requirements of the Lower De Grey

Figure A1 (a) Coolenar Pool and bore 7/04, (b) J96 Pool and bore 3/04 (c) Homestead Pool and bore 9/04, (d) Makanykarra Pool and bore 6/04 and (e) Bulgarene Pool and bore 8/04 40

Figure B1 Relationship between total magnitude of wet season flow and groundwater levels at bores (a) U1, (b) 7/04, (c) 9/04 and (d) 6/04 42

Figure B2 Relationship between wet season river stage height and groundwater levels at bores (a) U1, (b) 7/04, (c) 9/04 and (d) 6/04 42

Figure B3 Relationship between duration of wet season river flow events and groundwater levels at bores (a) U1, (b) 7/04, (c) 9/04 and (d) 6/04 43

Figure B4 Relationship between duration of wet season no-flow events and groundwater levels at bores (a) U1, (b) 7/04, (c) 9/04 and (d) 6/04 43

Figure C1 (a) Bores U1 and 3/04, (b) Bores 9/04 and T2 and (c)Bores 6/04 and U1 44

Figure D1 J96 Pool (a) 5th percentile, (b) 20th percentile, (c) 50th percentile 45

Figure D2 Homestead Pool (a) 5th percentile, (b) 20th percentile, (c) 50th percentile 45

Figure D3 Makanykarra Pool (a) 5th percentile, (b) 20th percentile, (c) 50th percentile 46

Figure F1 Location of additional groundwater-dependent ecosystems 48

Figure F2 Cuttangunah Well groundwater levels and percentiles 49

Figure F3 Elevation across transect between Cuttangunah Well (left) and Triangle Pool (right) 50

Figure F4 Bore H2 groundwater levels and percentiles 51

Figure F5 Elevation across transect between bores H1 (left) and H2 (right) 52

Figure F6 Bore 12 depth to groundwater and percentiles 52

Figure F7 Bore F1 depth to groundwater and percentiles 53

v Ecological water requirements of the Lower De Grey

Tables

Table 1 Major river flows in the region 4

Table 2 Hydro-ecological linkages of river pool and riparian vegetation ecosystems of the lower De Grey River 14

Table 3 River pools and associated bores 20

Table 4 Historic pool-level percentiles and seasonal variations 23

Table 5 Aquatic macrophyte habitat water depth requirements as historic percentile pool depths, pool levels and frequency and duration of levels 25

Table 6 Deep pool habitat water depth requirements as historic percentile pool depths, pool levels and frequency and duration of levels 28

Table 7 Groundwater level/depth requirements as historic percentile levels, depth to groundwater and frequency and duration of levels 31

Table F1 Historic groundwater level/depths 53

vi Summary

Ecological water requirements of the Lower De Grey

Ecological water requirements (EWRs) are The De Grey alluvial aquifer is recharged the water regimes required to maintain directly from infiltration of water through dependent ecosystems at a low level of risk the riverbed. Groundwater ecosystems (WRC 2000). EWRs are a key part of the water dependent on the aquifer are river pools, allocation process, which also considers the riparian vegetation and aquifer ecosystems social and cultural requirements of the water (stygofauna). The water requirements of resource and its consumptive demand. We stygofauna are poorly understood and also use EWRs in operating strategies and to hence they are not considered specifically help set licence conditions for proponents in this report. We have focused on four sites wishing to abstract water. representative of river pools and riparian vegetation across the study area. The Pilbara groundwater allocation plan will set allocation limits for the lower De Grey In previous studies of alluvial aquifers in the River alluvial aquifer. The Water Corporation’s Pilbara, hydro-ecological linkages have existing De Grey borefield (Namagoorie), been used to describe how groundwater which supplies water to the Port Hedland maintains biodiversity and ecological water supply scheme, is located in this processes and to define hydrological aquifer. This document supports the thresholds. To determine the EWRs this study allocation plan by describing the EWRs for uses a combination of these hydrological groundwater-dependent ecosystems of the thresholds and thresholds based on lower De Grey alluvial aquifer. statistical analyses of local hydrological data. To meet the EWRs we have set water- level criteria that reflect the varying water To set EWRs that reflect seasonal conditions, availability conditions experienced in the we considered different water availabilities. Pilbara region, rather than rigid criteria. These are presented as percentile thresholds. This will ensure that a natural water regime, Water availability conditions have been reflecting dry and wet periods, will be defined as: maintained. The De Grey River is intermittent – it flows after rainfall from summer cyclones • drought conditions: pool or and autumn thunderstorms. Compared with groundwater levels <5th percentile other Pilbara rivers, flow is reliable and has been recorded in all but one of the past • dry conditions: pool or groundwater 36 years. In addition, the De Grey’s mean levels <20th percentile annual flow from 1974 to 2010 (1342 GL) • average/above-average conditions: is an order of magnitude higher than the pool or groundwater levels >50th region’s next largest – the Ashburton percentile. (952 GL) and the Yule (363 GL) – despite similar rainfall. This is due to the catchment’s large area and the number of major tributaries that flow into the De Grey (Shaw, Strelley, Nullagine, Oakover and Coongan rivers).

vii Ecological water requirements of the Lower De Grey

We considered the historic frequency and • class 3 – average: total wet season duration of groundwater and river pool river flow 450 000 ML to 2 000 000 ML water levels beyond these thresholds. This allowed us to account for the variability in • class 4 – wet: total wet season river regional rainfall, recharge to aquifers and flow >2 000 000 ML. water availability to groundwater-dependent To apply the appropriate EWR to a given habitats over a range of climatic conditions. water year (May to April), the total volume of the previous wet season flow (November The EWRs were linked to river flow (being to April) is calculated and the water year is the source of aquifer recharge). Recharge allocated to a recharge class. Groundwater classes, based on river flow, were developed and pool levels for the rest of the water year to indicate which EWR (drought, dry or (i.e. to the end of the following April) should average) should be applied in any given fall within the range of the appropriate class year. Four classes were identified based on and not below the applicable percentile total wet season flow: threshold.

• class 1 – drought: total wet season river flow <100 000 ML

• class 2 – dry: total wet season river flow 100 000 ML to 450 000 ML

viii Introduction 1

Ecological water requirements of the Lower De Grey

The Department of Water is developing 3. Allocation limits method report a water allocation plan for the Pilbara groundwater area. Determination of the – describes how EWRs and other ecological water requirements (EWRs) for factors are considered in setting the groundwater-dependent ecosystems of the annual volume of water set the De Grey River alluvial aquifer will support aside for consumptive use. revision of the aquifer’s allocation limit. The 4. Groundwater allocation plan aquifer will be one of the resources included in the Pilbara groundwater allocation plan. – how water will be allocated and managed in the Pilbara EWRs are the water regimes required to groundwater area. maintain dependent ecosystems at a To fully understand this EWR report, it is low level of risk (WRC 2000). They are a valuable to first read the ecological values key consideration in the water allocation and issues report (Loomes & Braimbridge process, which aims to balance the 2010). consumptive demand for water with the needs of ecosystems and other in situ values. Environmental water provisions (EWPs) are The habitats considered in the EWR the water regimes provided as a result of the study were: water allocation process (WRC 2000). • river pool ecosystems 1.1 Purpose of this • riparian vegetation ecosystems. document The water requirements of stygofauna are poorly understood. As such, EWRs for This document presents the EWRs for stygofauna was not considered specifically groundwater-dependent ecosystems of the in this study. However, it is assumed that lower De Grey alluvial aquifer. It is one of meeting the EWRs of superficial habitats a series of documents that will inform the (pools and riparian vegetation) will also Pilbara groundwater allocation plan. The meet the requirements of subterranean documents are: aquifer habitats.

1. Ecological values and issues report

– identifies and describes groundwater-dependent ecosystems of the De Grey River.

2. Ecological water requirements report

1 1 Ecological water requirements of the Lower De Grey

Legend Location map ¸# Coolenar Pool gauging station (! DERBY !( Homestead PORT HEDLAND River (!

r Highway ´ ve Ri y NEWMAN re Namagoorie borefield (! G De !( 0 2.5 5 10 (!

Kilometres

Ridley River

Great Northern Highway ¸#

D eG re y Strelley River Shaw River Riv er

Government of Western Australia GoDepartmentvernmen tof o Waf Wteer stern Australia Department of Water MapM reference:ap referen C2219_020ce: C2219_020

Figure 1 Map showing the lower De Grey River EWR study area

2 1 Ecological water requirements of the Lower De Grey

1.2 Study area Rainfall associated with summer cyclones and autumn thunderstorms is highly episodic The De Grey River basin is located north-east and variable between years. Average total of Port Hedland in Western Australia’s Pilbara rainfall is low (400 mm) with approximately region. The De Grey’s catchment covers 70 per cent falling between November and an area of approximately 50 000 km2 and March. is the largest river by volume in the region (based on mean annual flow). The size of Hydrology the catchment and the number of major tributaries result in a relatively reliable flow The De Grey River flows to the north-west, with compared with other Pilbara rivers – with major tributaries being the Shaw, Strelley, some flow recorded in all but one of the past Coongan, Oakover and Nullagine rivers. 36 years. Small creeks and erosion channels run from the ranges and plains of the Chichester, The De Grey River study area includes the Goldsworthy, Isabella and Gregory ranges, reach downstream of its confluence with forming the river’s headwaters. Closer to the Shaw in the area around the existing the study area, the Strelley East and West Namagoorie borefield (Figure 1). The Water branches feed the Ridley River, which wraps Corporation operates the borefield as part of around the Ord Ranges before draining the Port Hedland water supply scheme. north-west (Worley Parsons 2005). From there the De Grey widens to approximately 1 km and becomes a well-developed coastal drainage system.

Based on mean and median annual flows, the De Grey is the largest and most reliable of the gauged Pilbara rivers (Kennard et al. 2010) (Table 1). Mean annual flow from 1974 to 2010 (1342 GL) is an order of magnitude higher than the next largest rivers in the region – the Ashburton (952 GL) and the Yule (363 GL) – despite similar rainfall (Table 1).

Over the 36-year flow record, no flow was recorded in one year and total flows less than 10 per cent of the mean annual flow De Grey River in flood were recorded in another six years (figures 2 and 3). This indicates that in one out of six years recharge to the lower De Grey alluvial Climate aquifer is lower than average. This compares with one in three years of low recharge to The Pilbara region’s climate is classified as the . The longest duration of no flow semi-arid to arid with hot, dry conditions was 19 months (between June 1985 and most of the year. Heat and clear skies result January 1986); however, this was the only in average evaporation greatly exceeding year of no measured flow. rainfall, causing an extreme soil moisture deficit.

3 1 Ecological water requirements of the Lower De Grey

Table 1 Major river flows in the Pilbara region

River Gauging station Catchment Mean annual Mean annual area (km2) rainfall (mm) flow (GL) Ashburton 706003 71 387 300 952 Cane 707005 2326 400 82 Robe 707002 7104 500 125 Fortescue1 708002 14 629 450 227 Fortescue2 708015 18 371 400 224 Maitland 709004 1948 375 48 Harding 709001 1058 400 39 Sherlock 709003 4581 400 164 Yule 709005 8427 400 363 Turner 709010 885 400 33 De Grey 710003 56 890 400 1342 Shaw 710229 6501 400 221 Coongan 710204 3736 400 118 1 Gauging station 708002 at Gregory Gorge 2 Gauging station 708015 at Bilanoo

5000000

4500000

4000000

3500000

3000000

2500000 Discharge (ML)Discharge Discharge (ML)Discharge 2000000

1500000

1000000

500000

0 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Figure 2 Total monthly discharge for the Coolenar Pool gauging station on the De Grey River (1975–2010)

4 1 Ecological water requirements of the Lower De Grey

Tot discharge Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec (GL) 1975 651.98 1976 1026.77 1977 1575.40 1978 1781.22 1979 480.96 1980 1981 no data 1982 1983 2413.77 1984 772.87 1985 449.30 1986 0 1987 1327.57 1988 3264.22 1989 298.79 1990 7.31 1991 74.58 1992 14.63 1993 766.21 1994 54.98 1995 1612.60 1996 1185.41 1997 1790.54 1998 1097.56 1999 4015.57 2000 6968.95 2001 411.22 2002 2122.32 2003 481.12 2004 3243.69 2005 21.43 2006 1509.18 2007 1723.00 2008 229.63 2009 1114.53 2010 18.56

flow no flow flow in low flow year (<10% of average annual flow) Figure 3 River flow analysis showing months of flow and years of low flow (<10 per cent average annual flow)

5 1 Ecological water requirements of the Lower De Grey

Ord Range

Upper sand aquifer

De Grey River Ground surface Middle sediments

Archaean metasediments volcanics and granite Mesozoic sediments Basal gravel/sand aquifer

Figure 4 Geological cross-section of lower De Grey River study area

Figure 5 Depth to groundwater at selected bores across the study area

6 1 Ecological water requirements of the Lower De Grey

Hydrogeology to supply the Port Hedland water supply scheme. The borefield comprises 11 The De Grey alluvial aquifer is formed by production bores and is licensed to abstract alluvial sediments within a paleochannel up to 7 GL/year. that is roughly overlain by the current river channel. There are three distinct aquifer Production bores in the Namagoorie units, described as the ‘upper sand aquifer’, borefield access the deeper basal gravel/ ‘middle sediments’ and ‘basal gravel/sand sand aquifer in the paleochannel. There aquifer’ (Worley Parsons 2005) (Figure 4). is also minor abstraction from the shallow The aquifers are largely unconfined with alluvial aquifer for the De Grey pastoral good vertical connectivity between layers station’s stock and domestic requirements. (Davidson 1974). In addition, Atlas Iron Ltd is licensed to The basal gravel/sand aquifer within the abstract 2.007 GL/year from a fractured paleochannel is the most productive aquifer rock aquifer in the adjacent Ore Ranges unit. It generally occurs at depths greater to dewater mine pits of the Pardoo Direct than 30 m below the ground surface, Shipping Ore Project. ranging in thickness from 20 to 40 m (Worley Parsons 2005). Data availability

Flooding of the De Grey and its main The Water Corporation has monitored tributaries, specifically the Shaw, Ridley groundwater and surface water levels and Strelley rivers, is the greatest source of across the study area since 1974. Water recharge to the De Grey aquifer (Worley levels and limited water quality are currently Parsons 2005). The size of the catchment monitored monthly to bi-monthly in 30 bores, makes it likely that rainfall will occur including eight shallow bores established on somewhere in a given year and that one or vegetation monitoring transects in 2004 more of the tributaries will flow – thus it is likely (04 series bores). Figure 6 shows the length the De Grey will receive some inputs in most of the bore data records across the years. Due to the reliability of flows, recharge lower De Grey since 1974. events are therefore relatively frequent. In addition to a gauging station at Coolenar Groundwater levels in the study area are Pool, monitored since 1974, surface water 4 to 11 m below the ground surface levels have been measured at five pools (Figure 5) and fluctuate with local along the river since 1998. Four of the 04 topography, pumping influence and time series bores are located at these pools. since recharge. Where the river channel Figure 7 shows the location of the gauging intersects the aquifer, permanent and station, monitored pools, monitoring bores semi-permanent pools occur as surface and the Namagoorie borefield. expressions of the alluvial aquifer. Water-level monitoring data were used Current groundwater use along with bore stratigraphy, climate data and river flow records to develop a The Water Corporation operates the numerical groundwater model of the lower Namagoorie borefield, which is located on De Grey’s alluvial aquifers (SKM 2010) The the paleochannel’s northern edge model will support water allocation planning (Figure 1). It was commissioned in 1979 and, where appropriate, the determination of EWRs.

7 1 Ecological water requirements of the Lower De Grey data points Bore data recorded across the De Grey River area since 1974, x represents Figure 6

8 1 (! Ecological water requirements of the Lower De Grey

Legend Location map ! ( Monitoring Bores (! (! (! ! EWR bore ´ DERBY (!(! (! (!(! (! (! PORT HEDLAND (! Ground (! (! ! Production (! (! NEWMAN (! Pools (! ") ")(! EWR pool (! Homestead Pool (! (! Other pool (!!9/04(! ! (! Namagoorie borefield (! T2 0 2 4 8 Recent alluvium Kilometres

(! (! (! (! (! U1 (! (! !!")(! (! (! (! (!6/04 3/04 J96 Pool (! (! ")! Makanykarra Pool (! ! (! (! ( (! (! ! (! (!( (! (! ! ! (! (! (! (! ! (! (! (! ! (! (! (! -E1- (! (! !7/04 ! (! ") Great Nort (! ! ! hern Highway Coolenar Pool ! ! (! (! (! (! (! (! (! (!

(! (! (! (! (! (! (! (! D (! eG re (! (! y (! (! Riv (! er (! (! (! (! (! (! (! (! (! (! (!(! (! (! (! (! (! (! (! (! (! (! (! (! (! (!(! (!

(! (! Government of Western Australia GDepartmentovernmen oft oWaf teWrestern Australia Department of Water (! (! Map reference:Map refere C2219_020nce: C2219_020 !( (! Figure 7 Location of Coolenar Pool gauging station, EWR pools, monitoring bores and the Namagoorie borefield

9 2 Groundwater-dependent ecosystems

Ecological water requirements of the Lower De Grey

Groundwater-dependent ecosystems are The area includes approximately 4500 ha those that rely on groundwater directly of tidal wetlands consisting of habitats such (e.g. stygofauna or phreatophytic vegetation as mudflats, coastal flats, mangroves and using groundwater from shallow watertables) about 22 km of tidal reaches (MWH Australia or indirectly (e.g. wetland vegetation 2007). Because mangroves are present, the or aquatic ecosystems sustained by De Grey is also recognised as a wetland of groundwater discharge). subregional significance (Kendrick & Stanley 2002). A full description of the groundwater- dependent ecosystems and their links to Three types of groundwater-dependent hydrogeology is presented in Lower De Grey ecosystem have been identified on the River: ecological values and issues (Loomes lower De Grey River: & Braimbridge 2010). A brief description of each, how they were defined and the • river pools groundwater/ecology linkages have been provided here to give context. • riparian vegetation • aquifer ecosystems. 2.1 Groundwater- River pools dependent Permanent, semi-permanent and intermittent ecosystems in the pools are found along the lower De Grey De Grey study area River (Figure 7). The pools support aquatic ecosystems of freshwater and marine fish The De Grey River is one of the Pilbara species, macroinvertebrates, waterbirds, region’s most valuable wetland systems. frogs, reptiles and aquatic flora. It is described as a rare example of how a system functions both hydrologically The river and pools are connected to and and biologically (Environment Australia interact with the underlying alluvial aquifer. 2001) with the frequency of recharge Hydrological data show strong correlations events maintaining groundwater levels between the pools and groundwater levels in and therefore dependent ecosystems. The the alluvial aquifer (Appendix A). De Grey also has outstanding historical and cultural significance. Because of When the river is in flood, the pools, these features it is listed in the Directory of floodplains and riparian zone are important wetlands in Australia (Environment connected, allowing biota and nutrients to Australia 2001). move through the system. During river flow events groundwater is recharged and the watertable rises.

10 2 Ecological water requirements of the Lower De Grey

These are dominated by the tree species Eucalyptus camaldulensis (river red gum), (cadjeput) and E. victrix (coolibah). The distribution of riparian communities reflects the depth to groundwater and the area inundated during flooding (HGM 1998; Loomes 2010; Loomes & Braimbridge 2010; Strategen 2006).

For this study depth-to-groundwater mapping has been developed using groundwater monitoring data and a digital elevation model derived from LiDAR (Figure 8). Mapping demonstrates that the riparian communities are restricted to Riparian vegetation areas of shallow groundwater (<10 m). The shallow depth to groundwater in the alluvium, especially along the river, provides When there is no flow in the river, the areas where deep-rooted vegetation can groundwater movement reverses and reach groundwater – which sustains these groundwater discharges into the pools. As communities in the absence of rainfall and/ groundwater levels decline, connection or surface flow. between the river channel and aquifer is reduced, with only deep pools or low The tolerance of species to groundwater (elevation) sections of the river intersecting availability varies. For example, M. argentea the watertable. is restricted to areas where the watertable is very shallow or at the surface (Graham Aquatic habitat is reduced as surface 2001). E. camaldulensis can reach a deeper water recedes and then groundwater watertable, but its distribution is restricted levels decline. As groundwater continues to by groundwater depth and reliance on decline, aquatic fauna become isolated into floodwaters for recruitment (Pettit & Froend a series of disconnected pools. 2001).

Deep pools that maintain connectivity with E. victrix tends to be found in drier conditions the groundwater throughout the dry season than E. camaldulensis and M. argentea. are critical refuges from which aquatic Although tolerant of long periods of drought fauna repopulate the river when floods this species appears sensitive to prolonged return. The continued input of groundwater inundation (Strategen 2006). to permanent pools is important to maintain adequate habitat and water quality during Maintenance of healthy riparian ecosystems the dry season and extended droughts. is important to river health and provides a relatively high productive ecosystem in Riparian vegetation an arid environment (Douglas et al. 2005). Riparian ecosystems in arid environments The shallow alluvial aquifer supports also provide important habitat for terrestrial phreatophytic (groundwater-dependent) fauna (van Dam et al. 2005). riparian vegetation. The riparian vegetation communities fringe the river.

11 2 Ecological water requirements of the Lower De Grey

Legend Location map ! EWR bore ") ´ ! EWR pool DERBY Depth to groundwater PORT HEDLAND < 0 !

") 0 - 2m NEWMAN Homestead 2 - 4m ! !9/04 4 - 6m ! ! T2 6 - 8m 8 - 10m ! ! 10 - 16m 0 1 2 4 6

16 - 22m Kilometres

U1 !!")J96 6/04 3/04 ")! Muccangarra

-E1- !7/04 ! ") Coolenar

GoGovernmentvernment o off Westernestern AustraliaAustralia Department of Department of WWaatteer Map reference: C2219_020 Map reference: C2219_020 Figure 8 EWR sites and estimated depth to groundwater on the lower De Grey River

12 2 Ecological water requirements of the Lower De Grey

Aquifer ecosystems Many macroinvertebrate species complete lifecycles and enter diapause (or dormancy) Diverse subterranean fauna have been based on the timing of intermittent surface found in aquifers across the Pilbara region, flows and the persistence of residual pools including the De Grey alluvial aquifer. Given (WRM 2009). Seasonal drought is therefore the lack of understanding of factors affecting well tolerated. However, the unpredictable the distribution of stygofauna and their nature of longer-term drought (inter-annual) habitat requirements, EWRs for stygofauna is more difficult for fauna to deal with (Pinder have not been determined specifically. & Leung 2009). However, stygofauna are taken into account in the EWRs through pool and riparian Inter-annual drought generally has a vegetation water requirements. We have negative impact on macroinvertebrate assumed that if these are being met, then density. However, the effect on an individual stygofauna requirements are also being met. pool depends on whether it dries completely Should more specific data become available and/or reaches other critical ecological these requirements can be reviewed. thresholds (e.g. water quality). At the river scale, the proportion of pools retaining 2.2 Hydro-ecological water is important because persistent pools provide refuge for fauna and act as sources linkages of colonisers once the drought ends (Pinder & Leung 2009). Conceptual models were developed to describe the relationships between the water regime and groundwater-dependent Fish and other fauna (e.g. frogs and reptiles) ecosystems (Loomes & Braimbridge 2010). have lifecycle strategies for surviving variable These relationships were used to identify conditions (WRM 2009). Provision of pool parts of the water regime that are critical for habitat consistent with regional seasonal each ecological component or process of and climatic patterns for macroinvertebrate the ecosystem (e.g. fish, riparian vegetation) communities will therefore also satisfy hydro- (Poff et al. 2010). We refer to these ecological linkages for fish (2c) and other relationships as hydro-ecological linkages. fauna (3a) (Table 2).

Hydro-ecological linkages have been Seasonality in De Grey River pool levels are grouped by ecological components therefore important to ensure that while of river pool and riparian ecosystems permanent pools remain inundated to (macroinvertebrates, fish, frogs and reptiles, provide macroinvertebrate habitat, enough vegetation and water quality) (Table 2). variation in pool depth and size occurs Some linkages overlap; that is, they relate to ensure the completion of lifecycles. to more than one ecological component. Seasonality and variation also ensures that A brief background on the key linkages is non-permanent pools are at times available provided below. as aquatic habitat, allowing increased productivity and exchange of biota between refuges. Surface water expression consistent with regional seasonality

Pilbara rivers experience an underlying seasonality, with little or no flow during winter and spring. Substantial variability also occurs between years, including some periods of longer-term drought (Pinder & Leung 2009).

13 2 Ecological water requirements of the Lower De Grey

Table 2 Hydro-ecological linkages of river pool and riparian vegetation ecosystems of the lower De Grey River

Ecological feature Hydro-ecological linkage 1 Macroinvertebrates 1a Macrophyte habitat inundated and available for a range of macroinvertebrate species 1b Available surface water expression consistent with regional seasonality 2 Fish 2a Macrophyte habitat inundated and available for small-bodied fish and juveniles of large-bodied fish species 2b Deeper habitat permanently inundated and available for mature fish and large-bodied fish species 2c Available surface water expression consistent with regional seasonality 3 Frogs and reptiles 3a Permanent surface water with seasonal fluctuation to provide frog and reptile habitat 4 Vegetation 4a Permanent inundation of pools to support aquatic macrophytes 4b Permanent available soil moisture to support riparian vegetation 4c Occasional inundation of all riparian and floodplain vegetation 4d Maintaining depth to groundwater within the range required by phreatophytic species and within the context of regional climate 5 Water quality 5a Sufficient depth in deep pools to ensure dissolved oxygen levels do not reduce to anoxia 5b Occasional high-level flows to scour the sediment

Macrophtyes inundated and The historic permanence of the selected available as habitat pools suggests macrophytes are likely to have been present consistently since water- Macrophytes provide important habitat for level records began. fish in the De Grey River pools that would otherwise be habitat poor (Pinder & Leung The macrophyte species recorded in the 2009). Given other habitat types – such as De Grey River pools reproduce by seed that woody debris and emergent macrophytes – is resilient to frequent or extended periods of are not widespread (van Dam et al. 2005), drought (van Dam et al. 2005). But although submerged macrophytes shelter small- macrophytes can tolerate periods of drying, bodied fish species and juveniles of larger- it is important they remain inundated and bodied species from predators (Storey 2003). available as habitat during drought and dry periods.

14 2 Ecological water requirements of the Lower De Grey

Maximum pool depth has been identified Permanent pool depths of greater than 1.5 m as a driver of fauna diversity on the De Grey will also satisfy the hydro-ecological linkage River and elsewhere in Australian arid/semi- for water quality (5a). This depth should arid systems (Morgan et al. 2009; van Dam ensure sufficient water is retained in pools to et al. 2005). Yet the minimum depth required minimise the risk of nutrient enrichment and to maintain macrophyte habitat has not anoxia (Braimbridge & Malseed 2007). been determined (van Dam et al. 2005). However, studies on the lower have Depth to groundwater within the determined that a minimum dry season range required by phreatophytic depth of 0.45 m is required to maintain areas of macrophyte habitat for small fish (Trayler riparian vegetation et al. 2006). As such, a depth of 0.45 m is The distribution of dominant riparian tree also recommended as the minimum depth species is restricted to areas where the for De Grey River pools. depth to groundwater is relatively shallow. In these zones larger (relatively) deep-rooted Permanent inundation of submerged riparian vegetation relies on groundwater to macrophytes for fish habitat will also satisfy meet at least part of its water requirements hydro-ecological linkages 4a (maintaining (Roberts et al. 2000). To maintain the health macrophytes) and 1a (macroinvertebrate and vigour of riparian woodlands, the depth habitat). to groundwater needs to remain within an accessible range. Deep pools available as habitat As discussed in Section 2.1, the shallow Previous studies (Beesley 2006; Dobbs & depths to groundwater along the De Grey Davies 2009; Morgan et al. 2009; van Dam River (<10 m) suggest riparian vegetation is et al. 2005) have found that maximum highly likely to be accessing groundwater. pool depth and/or pool stability are also This is supported by the correlation of important drivers of Pilbara fish community riparian woodland distribution with areas structure. Deeper pools are not only capable of shallow groundwater. Each of the four of supporting greater species richness, representative sites supports riparian tree abundance and diversity, but also persist species known to use groundwater to meet longer during dry periods. This provides a their water requirements between periods of drought refuge and allows fish populations soil water recharge (Humphreys 2000; Muir throughout the river to re-stock when flows Environmental 1995). do occur. A minimum depth of 1.5 m was considered adequate to maintain mature and large-bodied fish on the De Grey River (van Dam et al. 2005).

15 2 Ecological water requirements of the Lower De Grey

Setting a minimum groundwater level will water levels is considered inadequate for sustain riparian vegetation in drought years maintaining riparian community vigour in – providing the watertable remains within the long term and thus periods of higher an accessible range. At the De Grey and groundwater levels are required. Yule rivers, depths of <10 m are considered accessible to E. camaldulensis and While periodic floods are needed to stimulate M. argentea. However, while these minimum seedling germination, this represents levels are acceptable for a short time, they high-flow conditions. High flows are not are unlikely to maintain riparian communities considered part of the EWR. in the long term. Groundwater levels in the De Grey alluvial Greater water availability (i.e. a higher aquifer fluctuate with the region’s dynamic groundwater level) is required for mature climate and ecosystems have adapted to riparian trees to maintain new growth and cope with droughts and recover during wet periodically flower and set seed, as well as for periods. The EWR has been developed to seedlings to establish (Roberts et al. 2000). It reflect this. is also important for maintaining ecosystem resilience. As such, meeting only minimum

16 Approach to determining 3 ecological water requirements

Ecological water requirements of the Lower De Grey

3.1 Overview 3.2 Linkages The hydro-ecological linkages presented This study’s focus was to determine EWRs to in Section 2.2 form the EWR framework. assess and manage the potential impacts of Linkages describe how surface water or groundwater abstraction on groundwater- groundwater maintain important ecological dependent ecosystems. Linkages related to components and processes. Water maintenance of high-flow events levels or thresholds required to maintain (e.g. 4c and 5f) are unlikely to be affected these linkages were calculated and then by groundwater abstraction. Therefore combined to describe the EWRs. thresholds were not determined for all hydro-ecological linkages. This approach is adapted from contemporary methods to determine EWRs Some hydro-ecological linkages overlap; for surface water systems, which emphasise that is, it was considered that providing that different parts of the water regime water to meet one would also satisfy others. maintain different ecosystem components; For example, if linkage 2a (inundation of for example, Ecological Limits of Hydrologic macrophytes for small fish) is met, then Alteration (ELOHA) (Poff et al. 2010). It is linkages 1a (inundation of macrophytes for also consistent with contemporary methods macroinvertebrates) and 4a (permanent for groundwater (Eamus et al. 2006; Howe inundation of pools to support aquatic et al. 2007) that set out frameworks based macrophytes) will also be met. on conceptual models of groundwater ecosystem interaction. Ultimately four linkages were addressed in detail, with the remaining seven either The approach used to determine EWRs for related to high flows or satisfied by the water the De Grey alluvial aquifer’s groundwater- requirements of similar linkages. EWRs were dependent ecosystems includes the determined for each of the following four following: linkages:

• recognises the variable nature of the • 1b: surface water expression system’s climate and groundwater consistent with regional seasonality levels • 2a: macrophytes inundated and • provides thresholds or limits of available for small fish and juveniles acceptable change in water of large-bodied fish species availability for groundwater- dependent ecosystems. • 2b: deep pool habitat • 4d: depth to groundwater within the range required by phreatophytic vegetation species.

17 3 Ecological water requirements of the Lower De Grey

3.3 How we determined To account for the natural variability in water availability, we determined EWRs for hydrological a range of climatic conditions rather than thresholds set static water-level criteria. The EWRs were determined for three water availability Where hydrological thresholds are available conditions. These were characterised by to predict ecological responses to altered percentile groundwater or pool surface water availability (e.g. 0.45 m pool depth for water levels as follows: small fish species), they have been used as references for determining EWRs for De Grey • drought conditions: pool or River groundwater-dependent ecosystems. groundwater levels <5th percentile These thresholds have been drawn from previous work on the Yule and De Grey rivers • dry conditions: pool or groundwater (van Dam et al. 2005) and similar systems levels <20th percentile elsewhere in Australia (Braimbridge & • average/above-average conditions: Malseed 2007). pool or groundwater levels >50th percentile. Where thresholds do not exist, the EWRs were based on statistical (percentile) thresholds Frequency analyses were done to determine of the existing hydrological regime. This how often the 5th percentiles were breached approach is similar to that recommended in the past and how long each breach by ANZECC & ARMCANZ (2000) to derive lasted. The frequency and duration of biological, chemical and physical water periods above the 20th and 50th percentiles quality stressors. It has the advantage of were also calculated. These data are used representing the water regimes the ecology to refine thresholds; for example, how often has adapted to, as well as the natural the minimum or the 5th percentile can be variability in the system. breached and how often the higher levels of the 20th and 50th percentiles should be met. Results of a groundwater drawdown trial on the lower Yule River found negative eco-physiological responses in riparian 3.4 Recharge classes trees when water levels fell below the Given the critical link between river flow 20th percentile (i.e. levels less than those and aquifer recharge, the EWRs have been experienced 20 per cent of the time). linked to river flow. Recharge classes were The degree of response increased when developed to give an early indication of levels fell below the 5th percentile. The use which EWR (e.g. drought, dry or average) of percentiles allows us to translate the should be applied in any given year. thresholds from one site to another and to identify site-specific or local conditions. The degree of pool and groundwater Therefore, these thresholds – the 5th and 20th recharge is determined by the magnitude, percentiles – provide the basis for the EWRs. duration and height of river flows, along with the period between river flow events. These parameters were examined to see which single parameter, or combination of parameters, was the greatest driver of recharge along the De Grey (Appendix B).

18 3 Ecological water requirements of the Lower De Grey

Analyses of correlations showed that river • degree of river pool permanency flow volume or magnitude influenced groundwater levels in the study area more • availability of data for surface water than the river height or duration of flow. and groundwater levels Given more than 90 per cent of the De Grey • inclusion in previous flora and fauna River’s mean annual flow occurs between studies. November and April, it was considered that wet season flow volumes were a strong Four sites were selected: Coolenar, J96, predictor of groundwater levels over the Homestead and Makanykarra pools following dry season (May to October). (Figure 7). Each site has a permanent river pool, groundwater data, pool water-level To establish recharge classes, total wet data, pool bathymetry (except Coolenar season flows for the years 1975 to 2010 were Pool) and established vegetation transects. ranked by volume from lowest to highest Site details are provided below (Table 3). (with the exception of 1980 to 1982 for which no flow data are available). Each year Groundwater levels in the 04 series and older was then assigned to one of four recharge monitoring bores at each of J96, Homestead classes based on probability distribution. See and Makanykarra pools were strongly Section 4.2 for the findings. correlated with one another (Appendix C). The strength of the correlations enabled groundwater data to be back-calculated. 3.5 Site selection This provided longer datasets for 04 Water requirements were determined vegetation monitoring bores at two of the at a subset of sites representative of the sites as follows: groundwater-dependent ecosystems across the De Grey study area. The sites were • Homestead Pool: bores T2 and 9/04 – selected based on the following: bore 9/04 back-calculated to 2001 • Makanykarra Pool: bores U1 and • presence of representative 6/04 – bore 6/04 back-calculated groundwater-dependent ecosystem to 1978. types, river pools and riparian vegetation

• likely groundwater connectivity

• location within or close to the borefield

19 3 Ecological water requirements of the Lower De Grey

Table 3 River pools and associated bores

Pool/description Data source Distance Data availability from pool (m) Coolenar Gauging station - 11/74 – 08/11 – large pool located at the crossing E1 1700 8/74 – 12/10 of the Great Northern Highway 7/04 100 4/05 – 10/10 J96 Pool level - 9/96 – 10/10 – shallow pool on the west side of U1 250 8/78 – 10/10 the main channel downstream of 3/04 60 4/05 – 10/10 Coolenar Pool Homestead Pool level - 9/96 – 10/10 – large (~25 ha), deep pool on the T2 1500 5/78 – 10/10 eastern bank of the river adjacent to 9/04 1000 4/05 – 10/10 the De Grey Station homestead Makanykarra Pool level - 4/98 – 10/10 – long, narrow and deep (up to 7m) 6/04 50 4/05 – 10/10 pool on the Ridley River west of the De Grey

20 Ecological water requirements 4

Ecological water requirements of the Lower De Grey

Deep pool habitat

EWRs were determined for the four historic water regime. Applying EWRs based groundwater-ecology linkages for each on recharge classes will link annual pool- site. The specific approach, results and level requirements to regional climate. recommendations for each linkage are presented below. Although the four representative permanent pools act as drought refuges, seasonality in levels and depth – lower during dry seasons 4.1 Developing the and higher during wet seasons – should be ecological water maintained. The changes in depth of these pools should also be indicative of drying and requirements re-filling of semi-permanent and intermittent pools on the De Grey, which will meet the 1b Surface water expression lifecycle requirements of aquatic fauna. consistent with regional seasonality Results Approach The biggest seasonal variations occur at Makanykarra Pool (average -0.47 m, wet to To represent the historic range in pool levels, dry) (Table 4), possibly reflecting the greater percentiles (5th, 50th and 90th) representing depth and morphology of the pool. Despite low, average and high water availabilities the highest peak levels, Coolenar Pool shows were calculated and compared with pool the smallest seasonal variation (average hydrographs for representative sites -0.18 m, wet to dry). This is likely due to the (Figure 9, Table 4). ‘bottoming out’ of the hydrograph when the pool falls below the cease-to-flow level and Maintaining water levels in this range of the gauging station recording a constant percentiles will maintain inter-annual and value until flow resumes (see minimum pool seasonal variation. This will ensure the levels in Figure 9a). provision of habitat consistent with the

21 4 Ecological water requirements of the Lower De Grey

a

B

C

D

Figure 9 Pool levels and percentiles for (a) Coolenar Pool, (b) J96 Pool, (c) Homestead Pool and (d) Makanykarra Pool

22 4 Ecological water requirements of the Lower De Grey

Recommendation

To meet the EWR for this linkage, seasonality of pool levels should be maintained consistent with the levels in Table 4. Maintaining water levels in this range of percentiles will maintain inter-annual and seasonal variation in the river pools. This will ensure the provision of habitat consistent with the historic water regime. Applying EWRs based on recharge classes will link annual pool-level requirements to regional climate.

Table 4 Historic pool-level percentiles and seasonal variations

Percentile pool water-level (mAHD) Average seasonal variation (m)(wet – dry) 5th 50th 90th Coolenar 15.50 15.73 15.99 -0.18 J96 9.86 10.62 11.40 -0.39 Homestead 6.54 7.10 7.94 -0.35 Makanykarra 8.53 9.62 10.60 -0.47

2a Macrophytes inundated and available as fish habitat Approach

Pool bathymetry and pool water levels for J96, Homestead and Makanykarra pools were used to determine minimum water levels to maintain a target 0.45 m pool depth (Appendix D). As no bathymetry is available for Coolenar Pool and a minimum water level could not be calculated for this site, the 5th percentile was set as a minimum. However, because Coolenar Pool levels are recorded at the river gauging station, the recorded 5th percentile is likely to be higher than the actual level (i.e. levels are not recorded below cease-to-flow).

Pool monitoring data were analysed to determine if depths greater than 0.45 m were achieved under past water regimes, represented by the 5th, 20th and 50th percentiles. The frequency and duration of pool depths below 0.45 m was also calculated to gauge the historic provision of macrophyte habitat.

Results

Minimum pool levels required to maintain a depth of 0.45 m are as follows:

• J96 Pool – 9.61 mAHD

• Homestead Pool – 4.25 mAHD

• Makanykarra Pool – 3.43 mAHD

• Coolenar Pool – 15.50 mAHD (5th percentile).

23 4 Ecological water requirements of the Lower De Grey

a 11

10.5

10

9.5 xsection elevation and water levels (mAHD) 9 0 10 20 30 40 50 60 70 80 90

B 8

7

6

5

4 xsection elevation and poollevels (mAHD) xsection elevation and poollevels (mAHD) 3 0 20 40 60 80 100 120 140

C 12

10

8

6

4

2

0 0 5 10 15 20 25 30 35 40 xsection elevation and poollevesl (mAHD) Distance across pool (m)

x-section 5th 20th 50th 0.45 m

Figure 10 Water depth percentiles and 0.45 m depth across pool cross-sections at (a) J96, (b) Homestead and (c) Makanykarra pools

24 4 Ecological water requirements of the Lower De Grey

Percentiles of pool depths representing drought, dry and average conditions at the three pools have exceeded 0.45 m since records began in 2004 (Figure 10 and Table 5). The extent and depth of inundation of pools under each scenario are presented as contour plots in Appendix D.

Additional analyses of duration and frequency of entire datasets show that 0.45 m depth was met continuously at Makanykarra Pool. Although 0.45 m was neither met at Homestead Pool for one spell of two months, nor at J96 Pool for one spell of one month, under the majority of drought or dry conditions macrophyte habitat in these pools is maintained.

Table 5 Aquatic macrophyte habitat water depth requirements as historic percentile pool depths, pool levels and frequency and duration of levels

Pool Linkage/ Water Water level Frequency Median percentile depth (m) (mAHD) level/depth duration met level/ depth met (months) Coolenar <1a 0.45 - - - <5th - 15.50 20 2.5 >20th - 15.73 25 4.5 >50th - 15.99 59 1 J96 <1a 0.45 9.61 1 1 <5th 0.70 9.86 4 2.5 >20th 1.00 10.16 9 6 >50th 1.46 10.62 12 4 Homestead <1a 0.45 4.25 1 2 <5th 2.74 6.54 5 1 >20th 2.97 6.77 10 7.5 >50th 3.30 7.10 16 4.5 Makanykarra <1a 0.45 3.43 0 0 <5th 5.50 8.53 2 2.5 >20th 5.83 8.81 7 6 >50th 6.64 9.62 10 3

Recommendation

To meet the EWR for linkage 2a, a minimum dry season pool level of greater than 9.61 mAHD, 4.25 mAHD and 3.43 mAHD should be achieved at Homestead, J96 and Makanykarra pools respectively. At Coolenar Pool a minimum of 15.50 mAHD is recommended.

It is also recommended that surface-water-level monitoring be set up and pool bathymetry surveyed at Coolenar Pool.

25 4 Ecological water requirements of the Lower De Grey

2b Deep pool habitat suitable Percentile pool depths representing the drought, dry and average years at for large-bodied and mature Homestead and Makanykarra pools exceed fish species 1.50 m (Figure 11 and Table 6). Maintaining the current pool water-level regimes should Approach therefore ensure sufficient water depths to maintain deep pool habitat for a range of Pool bathymetry and pool water levels mature and large-bodied fish species in were used to determine whether depths these pools. greater than 1.5 m were achieved under past water regimes, as well as the frequency and duration of depths less than 1.5 m. A minimum pool depth of 1.5 m is not Data were also analysed to determine achieved under the 5th, 20th or 50th occurrences of the 5th, 20th and 50th percentiles (of pool water level) at J96 Pool percentile depths. Although no bathymetry although the 50th percentile falls within was available for Coolenar Pool, percentile 0.04 m. This means that J96 provides deep levels were considered. However, as pool habitat for larger fish only in years of discussed previously, recorded levels are above-average water availability. likely to be higher than actual levels, and percentiles for Coolenar Pool should only be The fish fauna recorded from J96 Pool by regarded as interim. van Dam et al. (2005) reflect the shallower depth of the pool; that is, the most abundant Results species are small bodied as adults (<100 mm). This contrasts with the large- Minimum pool levels required to maintain a bodied fish species dominant in Homestead depth of 1.5 m are as follows: and Makanykarra pools.

• J96 Pool – not set Anecdotally we know Coolenar Pool is deep (>2.0 m). However, as bathymetry data do • Homestead Pool – 5.30 mAHD not exist, we have used the 5th percentile to set a minimum pool level to maintain deep • Makanykarra Pool – 4.48 mAHD pool habitat. It is recommended the pool’s • Coolenar Pool – 15.50 mAHD (5th bathymetry be surveyed. percentile).

Analyses of duration and frequency of all water-level data show that 1.5 m depth was met continuously at Makanykarra Pool, but neither met at Homestead Pool for one spell of two months nor J96 Pool on 13 occasions averaging four and a half months.

26 4 Ecological water requirements of the Lower De Grey

a 11

10.5

10

9.5

xsection elevation and water levels (mAHD) 9 0 10 20 30 40 50 60 70 80 90

B 8

7

6

5

4 xsection elevation and poollevels (mAHD) xsection elevation and poollevels (mAHD) 3 0 20 40 60 80 100 120 140

C 12

10

8

6

4

2

0 0 5 10 15 20 25 30 35 40

xsection elevation and poollevels (mAHD) Distance across pool (m)

x-section 5th 20th 50th 1.5 m

Figure 11 Water depth percentiles and 1.5 m depth across pool cross-sections at (a) J96, (b) Homestead and (c) Makanykarra pools

27 4 Ecological water requirements of the Lower De Grey

Table 6 Deep pool habitat water depth requirements as historic percentile pool depths, pool levels and frequency and duration of levels

Pool Linkage/ Water Water level Frequency Median percentile depth (m) (mAHD) level/depth duration met level/ depth met (months) Coolenar <2b 1.50 - - - <5th - 15.50 20 2.5 >20th - 15.73 25 4.5 >50th - 15.99 59 1 J96 <2b 1.50 10.66 13 4.5 <5th 0.70 9.86 4 2.5 >20th 1.00 10.16 9 6 >50th 1.46 10.62 12 4 Homestead <2b 1.50 5.30 1 2 <5th 2.74 6.54 5 1 >20th 2.97 6.77 10 7.5 >50th 3.30 7.10 16 4.5 Makanykarra <2b 1.50 4.48 0 0 <5th 5.50 8.53 2 2.5 >20th 5.83 8.81 7 6 >50th 6.64 9.62 10 3

Recommendation Depths recorded at Coolenar, Homestead, and Makanykarra pools under the different To meet the EWR for linkage 2d, minimum water availability scenarios are also dry season levels of 5.30 mAHD and 4.48 considered sufficient to ensure oxygen levels mAHD should be maintained at Homestead do not reduce to anoxia, as required under and Makanykarra pools respectively. No hydro-ecological linkage 5a. However, the EWR to meet this linkage has been set for shallower depths of J96 Pool during dry J96 Pool because historically it has not seasons may result in lower water quality achieved depths of 1.5 m. At Coolenar Pool, than in other pools. Further investigations the 5th percentile level of 15.50 mAHD is may be required to look at seasonal recommended. changes in dissolved oxygen in Pilbara river pools and risks and triggers for anoxia and fauna response when it occurs.

28 4 Ecological water requirements of the Lower De Grey

4d Depth to groundwater Percentiles are a measure of the relative variability of a dataset and represent the within the range required local water regime conditions the dependent by phreatophytic riparian ecology has adapted to. As we are vegetation concerned with the impacts of groundwater drawdown, it is the extremes in local depth to Approach groundwater – represented by the minimum thresholds – that the EWRs address. Results of a groundwater drawdown trial on the lower Yule River to the west of Port It is recognised that 5th percentile levels will Hedland found water stress responses in be breached in very dry years. Although riparian trees when groundwater levels fell riparian vegetation may show negative after a sustained period of no recharge impacts from occasional breaches, and continued pumping. The water stress permanent declines in condition are responses were declines in: unlikely if breaches are infrequent. Although minimum water levels will maintain • pre-dawn leaf water potential and ecosystems, periods of greater water a lack of recovery between midday availability are also required, as discussed and pre-dawn readings above. These conditions should be met by the 20th and 50th water-level percentiles. • canopy density and canopy condition Results • rates of tree water use as indicated by sap flow velocity. Groundwater-level percentiles at each site are shown in Figure 12 and frequencies and Based on the vegetation response durations of groundwater levels and depths thresholds, medium and high risks of are summarised in Table 7. impact were identified in terms of depths to groundwater at local monitoring bores At each site the 5th percentile depths (Braimbridge 2011). These thresholds to groundwater (representing drought were compared with historic groundwater conditions) are less than the 10 m records for the monitoring sites and found to considered accessible to riparian tree consistently coincide with the 20th percentile species: that is, bore 7/04 – 7.06 m, bore U1 of water-level distribution for the medium risk – 9.12 m, bore 9/04 – 7.76 m and bore 6/04 of impact threshold and the 5th percentile – 8.38 m. for the high risk of impact threshold.

29 4 Ecological water requirements of the Lower De Grey

17 17 16.517 a 16.517 16.516 16.516 15.516 15.516 15.515 15.515 14.515 14.515 14.514 14.514

Groundwater level (mAHD) 14 14 Groundwater level (mAHD) Groundwater level (mAHD) Groundwater level (mAHD) Groundwater level (mAHD)

12 12 12 B 1211 11 11 1110 10 10 109 9 9 98 8

Groundwater level (mAHD) 8

Groundwater level (mAHD) 8 Groundwater level (mAHD) Groundwater level (mAHD) Groundwater level (mAHD)

12 12 C 1211 1112 1110 1011 109 109 98 98 87 78 76 67 Groundwater level (mAHD) Groundwater level (mAHD) 6 6 Groundwater level (mAHD) Groundwater level (mAHD) Groundwater level (mAHD) Groundwater level (mAHD) Groundwater level (mAHD) Groundwater level (mAHD) Groundwater level (mAHD) Groundwater level (mAHD)

D 9 9 8.59 8.59 8.58 8.58 7.58 7.58 7.57 7.57 6.57 6.57 6.5

Groundwater level (mAHD) 6.5 Groundwater level (mAHD) Groundwater level (mAHD) Groundwater level (mAHD) Groundwater level (mAHD) 9/04 5th% 20th% 50th % 9/04 5th% 20th% 50th % 9/04 5th% 20th% 50th % 9/04 5th% 20th% 50th % Figure 12 Groundwater levels and percentiles at (a) bore 7/04, (b) bore U1, (c) bore 6/04 and (d) bore 9/04

30 4 Ecological water requirements of the Lower De Grey

Table 7 Groundwater level/depth requirements as historic percentile levels, depth to groundwater and frequency and duration of levels

Bore/pool Percentile Groundwater Depth to Frequency Median level (mAHD) groundwater level/depth duration (m) met level/ depth met (months) 7/04 <5th 14.27 7.06 1 2 Coolenar >20th 14.47 6.86 5 9 >50th 14.96 6.37 7 4.5 U1 <5th 9.26 9.12 3 3 J96 >20th 9.65 8.73 10 7 >50th 10.06 8.32 9 9 9/04 <5th 7.05 7.76 3 2 Homestead >20th 7.38 7.43 5 12 >50th 7.72 7.09 8 5.5 6/04 <5th 7.87 8.38 3 3 Makanykarra >20th 8.48 7.77 10 12.5 >50th 9.14 7.11 10 9.5

Recommendations 4.2 Recharge classes To meet the EWR for linkage 4d, minimum Based on the probability curve (Figure 13, drought year levels of 14.27 mAHD, 9.26 Appendix E) wet season flow volumes fell into mAHD, 7.05 mAHD and 7.87 mAHD should the four recharge classes as follows: be maintained at bores 7/04, U1, 9/04 and 6/04 respectively. In a dry year levels of • class 1 – drought: total wet season 14.47 mAHD, 9.65 mAHD, 7.38 mAHD and flow <100 000 ML 8.48 mAHD are recommended at the bores outlined above, and during an average • class 2 – dry: total wet season flow year levels of 14.96 mAHD, 10.06 mAHD, 7.72 100 000 ML to 450 000 ML mAHD and 9.14 mAHD are recommended. • class 3 – average: total wet season flow 450 000 ML to 2 000 000 ML

• class 4 – wet: total wet season flow >2 000 000 ML.

31 4 Ecological water requirements of the Lower De Grey

1.1

1 4

0.9

0.8

0.7 3

0.6

0.5

Probability 0.4 2 0.3

0.2 0.1 1 0

Total wet season flow (ML)

Figure 13 Wet season flow probability distributions (1975–2011)

To apply the appropriate EWR to a given Box and whisker plots show the average (box water year (May to April), the total volume plots) and absolute (whiskers) groundwater of the previous wet season flow (November (Figure 14) and pool (Figure 15) level ranges to April) is calculated and the water year is experienced at each of the four study sites allocated to a recharge class. Groundwater in each recharge class. The 5th, 20th and and pool levels for the rest of the water year 50th groundwater-level percentiles are also (i.e. to the end of the following April) should shown. Given levels at Coolenar Pool are fall within the range of the appropriate class not recorded below the cease-to-flow level, and not below the applicable percentile percentiles can only be regarded as interim, threshold. pending actual monitoring of pool levels.

32 4 Ecological water requirements of the Lower De Grey

a 17.5 17 16.5 16 15.5 15 50 20 14.5 5 14

Groundwater level(mAHD)Groundwater 13.5 1 2 3 4 percentiles Recharge class

B 12 11.5 11 10.5 10 50 20 9.5 5 9 8.5

Groundwater level(mAHD)Groundwater 8 1 2 3 4 percentiles Recharge class C 12

11

10

9 50 20 8 5 Groundwater level(mAHD)Groundwater Groundwater level(mAHD)Groundwater 7 1 2 3 4 percentiles Recharge class D 9.5 9 8.5 8 50 7.5 20 7 5 6.5

Groundwater level(mAHD)Groundwater 6 1 2 3 4 percentiles Recharge class

Figure 14 Mean and absolute groundwater levels for each recharge class at (a) bore 7/04, (b) bore U1, (c) bore 6/04 and (d) bore 9/04

33 4 Ecological water requirements of the Lower De Grey

a 17 15 13 11 50

Pool level (mAHD)Pool 9 20 7 5 1 2 3 4 percentiles Recharge class

B 13 12.5 12 11.5 11 10.5 50 20 10 5 Pool level (mAHD)Pool 9.5 9 1 2 3 4 percentiles Recharge class

C 9 8.5 8 7.5 50 7 20 Pool level (mAHD)Pool Pool level (mAHD)Pool 6.5 5 6 1 2 3 4 percentiles Recharge class

D 13 12

11

10 50

Pool level (mAHD)Pool 9 20 5 8 1 2 3 4 percentiles Recharge class

Figure 15 Mean and absolute pool levels for each recharge class at (a) Coolenar Pool, (b) J96 Pool, (c) Homestead Pool and (d) Makanykarra Pool

34 4 Ecological water requirements of the Lower De Grey

As expected, mean water levels generally Drought condition pool levels (5th percentile) increased, moving from the lowest water meet the fauna requirements of Homestead availability conditions of recharge class and Makanykarra pools. Although deep pool 1 to the highest in recharge class 4. The habitats are not found at J96 Pool, the 5th percentile levels also fell where predicted. percentile equates to a depth of That is, the 5th and 20th percentiles generally 0.45 m. Given the composition of fauna in fell close to the mean minimum levels of this pool reflects this depth, the 5th percentile recharge class 1 and 2 respectively. These level is recommended. In the absence of findings support the idea that recharge pool bathymetry for Coolenar Pool, the 5th classes are representative of actual water percentile has also been set as a minimum availability conditions. during drought conditions.

The water levels of some recharge classes To maintain variation in pool habitat overlap; for example, mean minimum levels availability during periods of higher water of recharge classes 2 and 3 in bores U1, 6/04 availability, the 20th and 50th percentiles and 9/04. However, this may be a result of have been recommended for dry and the patchy data that often resulted in only a average conditions respectively. small number of years being represented in recharge classes. Groundwater-level 5th percentiles have also been recommended for riparian vegetation As an example of recharge class application during drought periods. However, although – if total wet season flow in 2011 is riparian vegetation communities will tolerate <100 000 ML it falls into recharge class drought conditions, they are unlikely to 1: drought conditions. Using mean maintain health and condition if low water groundwater-level ranges, levels at bore availability persists for extended periods. The U1 over the following water year (i.e. to the 20th and 50th percentiles have therefore end of the following April) are likely to range been recommended for dry and average between 9.38 and 9.87 mAHD. In addition, conditions. levels are not to fall below 9.38 mAHD (the drought condition EWR) for more than three To allow for inter-annual variation in river months in a five-year period, as described in flow and water availability, the frequency Section 4.1. and duration of recommended levels have been set over a five-year period. Median (middle) values, calculated for river pool 4.3 Environmental water and groundwater levels, were used in dry requirement summary and average conditions. Frequencies and durations for drought conditions were based The water levels and/or depths needed on the results of the Yule River groundwater to meet some hydro-ecological linkage drawdown trial. requirements also meet others. For example, a minimum pool depth of 1.5 m to provide habitat for large fish species also meets the 0.45 m depth for submerged macrophytes and small fish.

35 4 Ecological water requirements of the Lower De Grey

Coolenar Pool (interim EWR) Dry conditions Drought conditions • Pool level of >10.16 mAHD to be reached more than five times for a • Pool level of 15.50 mAHD at the river duration of six months in a five-year gauge not to be breached more period. than three times for a duration of more than one month in a five-year • Groundwater level of >9.65 mAHD at period. bore U1 to be reached more than four times for a duration of nine • Groundwater level of 14.27 mAHD at months in a five-year period. bore 7/04 not to be breached more than three times for a duration of Average conditions more than one month in a five-year • Pool level of >10.62 mAHD to be period. reached more than eight times for a Dry conditions duration of three months in a five- year period. • Pool level of >15.73 m at the river gauge to be reached more than six • Groundwater level of >10.06 mAHD times for a duration of six months in a at bore U1 to be reached more than five-year period. four times for a duration of six months in a five-year period. • Groundwater level of >14.47 mAHD at bore 7/04 to be reached more Homestead Pool than four times for a duration of nine months in a five-year period. Drought conditions

Average/above-average conditions • Pool level of 6.54 mAHD not to be breached more than three times for • Pool level of >15.99 m at the river a duration of more than one month gauge to be reached more than in a five-year period. eight times for a duration of three months in a five-year period. • Groundwater level of 7.05 mAHD at bore 9/04 not to be breached more • Groundwater level of >14.96 mAHD at than three times for a duration of bore 7/04 to be reached more than more than one month in a five-year four times for a duration of six months period. in a five-year period. Dry conditions J96 Pool • Pool level of >6.77 mAHD to be Drought conditions reached more than five times for a duration of six months in a five-year • Pool level of 9.86 mAHD not to be period. breached more than three times for a duration of more than one month • Groundwater level of >7.38 mAHD in a five-year period. at bore 9/04 to be reached more than four times for a duration of nine • Groundwater level of 9.26 mAHD at months in a five-year period. bore U1 not to be breached more than three times for a duration of more than one month in a five-year period.

36 4 Ecological water requirements of the Lower De Grey

Average conditions Average conditions

• Pool level of >7.10 mAHD to be • Pool level of >9.62 mAHD to be reached more than eight times for a reached more than eight times for a duration of three months in a five- duration of six months in a five-year year period. period.

• Groundwater level of >7.72 mAHD at • Groundwater level of >9.14 mAHD at bore 9/04 to be reached more than bore 6/04 to be reached more than four times for a duration of six months four times for a duration of six months in a five-year period. in a five-year period. Makanykarra Pool To apply the EWR as measureable EWP criteria, continued monthly monitoring of Drought conditions bore and pool levels at the target sites will be required. Ongoing monitoring at the • Pool level of 8.53 mAHD not to be Coolenar Pool gauging station will also be breached more than three times for needed for annual recharge classes to be a duration of more than one month determined. in a five-year period.

• Groundwater level of 7.87 mAHD at bore 6/04 not to be breached more than three times for a duration of more than one month in a five-year period.

Dry conditions

• Pool level of >8.81 mAHD to be reached more than five times for a duration of six months in a five-year period.

• Groundwater level of >8.48 mAHD at bore 6/04 to be reached more than four times for a duration of nine months in a five-year period.

37

Appendices

Ecological water requirements of the Lower De Grey

39 Appendix A - Relationships between A groundwater and pool levels

Ecological water requirements of the Lower De Grey

a 20 2019 201918 191817 181716 171615 161514 Coolenar Pool (mAHD) Pool Coolenar 1514 14 14.5 15 15.5 16 16.5 17 Coolenar Pool (mAHD) Pool Coolenar Bore 7/04 (mAHD) 14 14 14.5 15 15.5 16 16.5 17 Coolenar Pool (mAHD) Pool Coolenar 11 14 14.5 15Bore 7/04 15.5 (mAHD) 16 16.5 17 11 Bore 7/04 (mAHD) B 10.5 11 10.5 10 10.5 10 9.5 10

J96 Pool (mAHD) 9.5 9

J96 Pool (mAHD) 9.5 9 9 9.5 10 10.5 11 11.5 12

J96 Pool (mAHD) 9 9 9.5 10Bore 3/04 10.5 (mAHD) 11 11.5 12 109 9.5 10Bore 3/04 10.5 (mAHD) 11 11.5 12 9.510 Bore 3/04 (mAHD) 9 C 9.510 8.5 9.59 8 8.59 7.5 8.58 7 7.58 6.5 7.57 Homestead Pool (mAHD) Pool Homestead Homestead Pool (mAHD) Pool Homestead 456789101112 6.57 Homestead Pool (mAHD) Pool Homestead Homestead Pool (mAHD) Pool Homestead Bore 9/04 (mAHD) 6.5 456789101112 Homestead Pool (mAHD) Pool Homestead Homestead Pool (mAHD) Pool Homestead 11 456789101112Bore 9/04 (mAHD) 10.511 Bore 9/04 (mAHD) 10.51110 10.59.510

(mAHD) 9.5109 8.5 (mAHD) 9.59 Makanykarra Pool MakanykarraPool 8.58

(mAHD) 9 Makanykarra Pool MakanykarraPool 8.58 8 8.5 9 9.5 10 10.5 11

Makanykarra Pool MakanykarraPool Bore 6/04 (mAHD) 8 8 8.5 9 9.5 10 10.5 11 11.0 8 8.5 9Bore 6/04 9.5 (mAHD) 10 10.5 11 11.0 Bore 6/04 (mAHD) 10.5 11.0 10.5 10.0 10.5 10.0 40 9.5 10.0 9.5 9.0

BulgarenePool (mAHD) 9.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 BulgarenePool (mAHD) Bore 8/04 (mAHD) 9.0 9.5 10.0 10.5 11.0 11.5 12.0 BulgarenePool (mAHD) 9.5 10.0 10.5Bore 8/04 (mAHD) 11.0 11.5 12.0 Bore 8/04 (mAHD) 20 2019 1918 1817 1716 1615 1514 Coolenar Pool (mAHD) Pool Coolenar 14 14 14.5 15 15.5 16 16.5 17

Coolenar Pool (mAHD) Pool Coolenar Bore 7/04 (mAHD) 14 14.5 15 15.5 16 16.5 17 11 Bore 7/04 (mAHD)

10.511

10.510

9.510

J96 Pool (mAHD) 9.59

J96 Pool (mAHD) 9 9 9.5 10 10.5 11 11.5 12 9 9.5 10Bore 3/04 10.5 (mAHD) 11 11.5 12 10 Bore 3/04 (mAHD) 9.5 10 9 9.5 8.5 9 8 8.5 A 7.5 8 Ecological water requirements of the Lower De Grey 7 7.5 6.5 7 Homestead Pool (mAHD) Pool Homestead Homestead Pool (mAHD) Pool Homestead 6.5 456789101112 Homestead Pool (mAHD) Pool Homestead Homestead Pool (mAHD) Pool Homestead Bore 9/04 (mAHD) 456789101112 D 11 Bore 9/04 (mAHD) 10.511 10.510 9.510

(mAHD) 9.59 8.5

(mAHD) 9 Makanykarra Pool MakanykarraPool 8.58 Makanykarra Pool MakanykarraPool 8 8 8.5 9 9.5 10 10.5 11 Bore 6/04 (mAHD) 8 8.5 9 9.5 10 10.5 11 11.0 Bore 6/04 (mAHD) E 10.511.0

10.010.5

10.09.5

9.09.5 BulgarenePool (mAHD) 9.0 9.5 10.0 10.5 11.0 11.5 12.0

BulgarenePool (mAHD) Bore 8/04 (mAHD) 9.5 10.0 10.5 11.0 11.5 12.0 Bore 8/04 (mAHD)

Figure A1 (a) Coolenar Pool and bore 7/04, (b) J96 Pool and bore 3/04 (c) Homestead Pool and bore 9/04, (d) Makanykarra Pool and bore 6/04 and (e) Bulgarene Pool and bore 8/04

41 Appendix B – Relationship between B groundwater levels and river flow parameters

Ecological water requirements of the Lower De Grey

a 11.5 11.5 a 11.5 11.5 11.511 11.511 11.511 11.511 10.511.51110.511.511 10.511.51110.511.511 11.511.5 11.51111.511 10.5101110.51011 10.510 10.510 11 11 10.5111010.51110 10.59.51010.59.510 9.5 9.5 10.510.5 10.59.51010.59.510 9.5109 9.5109 9 9 10 10 9.5109 109.59 8.59.59 8.59.59 8.5 8.5 Annual minimum Annual minimum 9.5 9.5 9.58.59 9.58.59

8.59 8.59 minimum annual Mean minimum annual Mean Annual minimum Annual minimum 8 8 8 8 groundwater level (mAHD) groundwater level (mAHD)

groundwater level (mAHD) groundwater level (mAHD) 9 9 9 9 8.58 8.58 minimum annual Mean minimum annual Mean 8.58 8.58 Annual minimum Annual minimum

groundwater level (mAHD) groundwater level (mAHD) 77 9 9 11 11 13 13 15 15 17 17 19 19 groundwater level (mAHD) groundwater level (mAHD) 00 2000 2000 4000 4000 6000 6000 8000 8000 8.5 8.5

8.5 8.5 minimum annual Mean minimum annual Mean Annual minimum Annual minimum 8 08 0 2000 2000 4000 4000 6000 6000 8000 8000 8 78 7 9 9 11 11 13 13 15 15 17 17 19 19 groundwater level (mAHD) groundwater level (mAHD) RiverRiver stage stage height height (m) (m) groundwater level (mAHD) groundwater level (mAHD) 8 8 TotalTotal wet seasonwet season flow flow(ML) (ML) minimum annual Mean minimum annual Mean 8 8

groundwater level (mAHD) groundwater level (mAHD) 77 9River 9 11River stage 11 stage 13height 13height 15(m) 15(m) 17 17 19 19 groundwater level (mAHD) groundwater level (mAHD) 00Total 2000Total 2000wet seasonwet 4000 season 4000 flow 6000 flow(ML)6000 (ML) 8000 8000 00 2000 2000 4000 4000 6000 6000 8000 8000 77 9River 9 11River stage 11 stage 13height 13 height 15(m) 15 (m) 17 17 19 19 15 15 TotalTotal wet seasonwet season flow flow(ML) (ML) 15 15 RiverRiver stage stage height height (m) (m) 15 15 TotalTotal wet wetseason season flow flow (ML) (ML) 15 15 B 14.8 14.8 B 15 15 14.51514.515 14.81514.815 14.51514.515 14.6 14.6 14.814.8 14.514 14.514 14.814.614.814.6 14.4 14.4 14.51414.514 14.614.6 14.614.414.614.4 13.51413.514 14.2 14.2 14.414.4 13.51413.514 Annual minimum Annual minimum 14.414.214.414.2 Mean annual minimum minimum annual Mean minimum annual Mean Annual minimum Annual minimum 14 14 13.513 13.513

14.214.2 groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) 14 14 minimum annual Mean minimum annual Mean 13.51313.513 Annual minimum Annual minimum 14.214.2 77 9 9 11 11 13 13 15 15 17 17 19 19 00 2000 2000 4000 4000 6000 6000 8000 8000 groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) Mean annual minimum minimum annual Mean minimum annual Mean Annual minimum Annual minimum 14 014 0 2000 2000 4000 4000 6000 6000 8000 8000 13 713 7 9 9 11 11 13 13 15 15 17 17 19 19

groundwater level (mAHD) groundwater level (mAHD) RiverRiver stage stage height height (m) (m)

groundwater level (mAHD) groundwater level (mAHD) TotalTotal wet seasonwet season flow flow(ML) (ML) Mean annual minimum minimum annual Mean minimum annual Mean 13 13 14 14 77 9 9 11 11 13 13 15 15 17 17 19 19 00 2000 2000 4000 4000 6000 6000 8000 8000 groundwater level (mAHD) groundwater level (mAHD) RiverRiver stage stage height height (m) (m) groundwater level (mAHD) groundwater level (mAHD) TotalTotal wet seasonwet season flow flow(ML) (ML) 77 9 9 11 11 13 13 15 15 17 17 19 19 11 1100 2000 2000 4000 4000 6000 6000 8000 8000 11 11 RiverRiver stage stage height height (m) (m) TotalTotal wet seasonwet season flow flow(ML) (ML) 11 11 11 11 TotalTotal wet wetseason season flow flow (ML) (ML) 10 10 RiverRiver stage stage height height (m) (m) 10 10 11 11 1011 1011 C 10 10 C 119 119 119 119 10 10 10 10 9 9 9 9 108 108 108 108 89 89 9 9 79 97 8 8 8 8 79 97 7 7 8 8 68 86 Annual minimum Annual minimum 7 7 67 67 Mean annual minimum minimum annual Mean minimum annual Mean 8 8 minimum annual Mean minimum annual Mean Annual minimum Annual minimum 5 5 groundwater level (mAHD) groundwater level (mAHD) 6 6 groundwater level (mAHD) groundwater level (mAHD) 7 7 Mean annual minimum minimum annual Mean minimum annual Mean Mean annual minimum minimum annual Mean minimum annual Mean groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) 7 7 56 56 groundwater level (mAHD) groundwater level (mAHD) 6 6 groundwater level (mAHD) groundwater level (mAHD) Annual minimum Annual minimum 77 9 9 11 11 13 13 15 15 17 17 19 19 groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) 7 07 0 2000 2000 4000 4000 6000 6000 8000 8000 6 6 Mean annual minimum minimum annual Mean minimum annual Mean Mean annual minimum minimum annual Mean minimum annual Mean

Annual minimum Annual minimum 5 5 groundwater level (mAHD) groundwater level (mAHD) 6 06 0 2000 2000 4000 4000 6000 6000 8000 8000 groundwater level (mAHD) groundwater level (mAHD) 77 9 9 11 11 13 13 15 15 17 17 19 19 Mean annual minimum minimum annual Mean minimum annual Mean Mean annual minimum minimum annual Mean minimum annual Mean groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) TotalTotal wet seasonwet season flow flow(ML) (ML) 5 5 RiverRiver stage stage height height (m) (m) groundwater level (mAHD) groundwater level (mAHD) 6 6 groundwater level (mAHD) groundwater level (mAHD) 77 9 9 11 11 13 13 15 15 17 17 19 19 groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) 00Total 2000Total 2000wet seasonwet 4000 season 4000 flow flow(ML) 6000 (ML) 6000 8000 8000 RiverRiver stage stage height height (m) (m) 00 2000 2000 4000 4000 6000 6000 8000 8000 77 9 9 11 11 13 13 15 15 17 17 19 19 8.5 8.5 TotalTotal wet seasonwet season flow flow(ML) (ML) 8.5 8.5 RiverRiver stage stage height height (m) (m) 8.5 8.5 TotalTotal wet wetseason season flow flow (ML) (ML) 8.5 8.5 RiverRiver stage stage height height (m) (m) 8 8 8.5 8.5 8.58 8.58 8.58 8.58 D 7.5 7.5 D 8.58 8.58 8 8 7.58 7.58 7.58 7.58 7 7 7.5 7.5 7.58 7.58 7.57 7.57 6.5 6.5 7.57 7.57 7 7 Annual minimum Annual minimum 7.57 7.57 6.57 6.57 Annual minimum Annual minimum 6 6 minimum annual Mean minimum annual Mean 6.57 6.57

groundwater level (mAHD) 6.5groundwater level (mAHD) 6.5 groundwater levels (mAHD) groundwater levels (mAHD) 6 6 minimum annual Mean minimum annual Mean Annual minimum Annual minimum 6.5 6.5 6.57 6.57 groundwater level (mAHD) groundwater level (mAHD) 00 2000 2000 4000 4000 6000 6000 8000 8000 groundwater levels (mAHD) groundwater levels (mAHD) 77 9 9 11 11 13 13 15 15 17 17 19 19 Annual minimum Annual minimum 6 06 0 2000 2000 4000 4000 6000 6000 8000 8000 minimum annual Mean minimum annual Mean 6.5 6.577 9 9 11 11 13 13 15 15 17 17 19 19 groundwater level (mAHD) groundwater level (mAHD) TotalTotal wet seasonwet season flow flow(ML) (ML) groundwater levels (mAHD) groundwater levels (mAHD) 6 6 minimum annual Mean minimum annual Mean 6.5 6.5 RiverRiver stage stage height height (m) (m) groundwater level (mAHD) groundwater level (mAHD) 00Total 2000Total 2000wet seasonwet 4000 season 4000 flow flow(ML) 6000 (ML) 6000 8000 8000 groundwater levels (mAHD) groundwater levels (mAHD) 77 9 9River 11River stage 11 13stage height 13 height 15 (m) 15 (m) 17 17 19 19 00 2000 2000 4000 4000 6000 6000 8000 8000 77 9 9 11 11 13 13 15 15 17 17 19 19 TotalTotal wet seasonwet season flow flow(ML) (ML) RiverRiver stage stage height height (m) (m) TotalTotal wet wetseason season flow flow (ML) (ML) RiverRiver stage stage height height (m) (m)

Figure B1 Figure B2 Relationship between total magnitude Relationship between wet season river of wet season flow and groundwater stage height and groundwater levels levels at bores (a) U1, (b) 7/04, at bores (a) U1, (b) 7/04, (c) 9/04 and (d) 6/04 (c) 9/04 and (d) 6/04

42 B Ecological water requirements of the Lower De Grey

a 11.5 11.5 a 11.5 11.5 11.511 11.511 11.511 11.511 10.511 10.511 11.5 11.5 11.510.511 11.510.511 11.510.510 11.510.510 11 11 11.510.51110 11.510.51110 9.51110 10.59.51110 10.5 10.5119.510 10.5119.510 10.59.59 10.59.5109 10 10.5109.59 10.59.5109 8.510 9 8.5109.59 9.5 9.5108.59 9.5108.59 9.58.58 9.58.589

Mean annual minimum minimum annual Mean minimum annual Mean 9 9.58.598 9.58.598 Mean annual minimum minimum annual Mean minimum annual Mean groundwater level (mAHD) 7.59 8groundwater level (mAHD) 7.58.598

8.5 minimum annual Mean Mean annual minimum minimum annual Mean groundwater levels (mAHD) 8.598 groundwater levels (mAHD) 08.598 0 50 50 100 100 150 150 200 200 Mean annual minimum minimum annual Mean groundwater level (mAHD) Mean annual minimum minimum annual Mean groundwater level (mAHD) 8.57.58 08.57.58 0 50 50 100 100 150 150 200 200 groundwater levels (mAHD) Mean annual minimum minimum annual Mean groundwater levels (mAHD) Mean annual minimum minimum annual Mean 8.58 08.58 0 50No-flow 50 100No-flow duration 100 duration (days) 150 (days) 150 200 200 Mean annual minimum minimum annual Mean groundwater level (mAHD) Mean annual minimum minimum annual Mean groundwater level (mAHD) 7.58 07.58 0 50Flow duration 50Flow 100 duration (days) 100 150 (days) 150 200 200 Mean annual minimum minimum annual Mean minimum annual Mean

8 groundwater levels (mAHD) 8 groundwater levels (mAHD) 0No-flow 50No-flow duration 100 duration (days) (days) 150 200 Mean annual minimum minimum annual Mean minimum annual Mean groundwater level (mAHD) groundwater level (mAHD) 0 50 100 150 200 7.5 07.5 0 50Flow 50durationFlow 100 duration (days) 100 150 (days) 150 200 200 15 15 groundwater levels (mAHD) 15groundwater levels (mAHD) 0150 50No-flow 50No-flow 100duration 100 duration (days) 150 (days) 150 200 200 00 50Flow 50durationFlow 100 duration (days) 100 150 (days) 150 200 200 15 15 15 15 No-flowNo-flow duration duration (days) (days) B 14.8 14.8 Flow durationFlow duration (days) (days) B 15 14.5 14.515 14.815 14.8 15 14.615 14.615 14.515 14.515 14.8 14.814.6 14.6 14.514 14.514 14.814.4 14.814.4 14 14 14.6 14.6 14.5 14.5 14.4 14.4 13.5 13.5 14.614.2 14.614.2 14 14 14.4 14.4 13.5 13.5

Mean annual minimum minimum annual Mean minimum annual Mean 14.2 14.2 14 14 groundwater level (mAHD) groundwater level (mAHD)

14.4 minimum annual Mean 14 14.414 13 13.513 Mean annual minimum minimum annual Mean 13.5 14.2 minimum annual Mean minimum annual Mean groundwater level (mAHD)

groundwater level (mAHD) 14.2

14 14 groundwater level (mAHD) 13 groundwater level (mAHD) 13 Mean annual minimum minimum annual Mean Mean annual minimum minimum annual Mean 13.5 13.5 Mean annual minimum minimum annual Mean 00 50 50 100 100 150 150 200 200 00 50 50 100 100 150 150 200 200 Mean annual minimum minimum annual Mean

14.2 14.2 groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) 14 014 0 50 50 100 100 150 150 200 200 13 013 0 50 50 100 100 150 150 200 200 Mean annual minimum minimum annual Mean Mean annual minimum minimum annual Mean minimum annual Mean Flow durationFlow duration (days) (days) minimum annual Mean No-flowNo-flow duration duration (days) (days) groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) 14 014 0 50 50 100 100 150 150 200 200 groundwater level (mAHD) 13 013 0No-flow 50No-flow duration 50 100 duration (days) 100 150 (days) 150 200 200 Flow durationFlow duration (days) (days) minimum annual Mean minimum annual Mean

11 11 groundwater level (mAHD) groundwater level (mAHD) 00 50Flow 50 durationFlow 100 duration (days) 100 150 (days) 150 200 200 11 011 0No-flow 50No-flow duration 50 100 duration (days) 100 150(days) 150 200 200 11 11 11 11 10 10 Flow durationFlow duration (days) (days) No-flowNo-flow duration duration (days) (days) 11 11 10 1110 C 10 10 C 1110 10 119 119 10 10 119 11109 9 9 109 9 108 108 9 9 108 1098 8 8 98 8 97 97 8 8 97 987 7 7 87 7 Mean annual minimum minimum annual Mean minimum annual Mean Mean annual minimum minimum annual Mean minimum annual Mean 86 86 7 7 minimum minimum annual annual Mean Mean 86 minimum minimum annual annual Mean Mean 876 groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) Mean annual minimum minimum annual Mean Mean annual minimum minimum annual Mean 6 7 Mean annual minimum minimum annual Mean Mean annual minimum minimum annual Mean Mean annual minimum minimum annual Mean Mean annual minimum minimum annual Mean 6 Mean annual minimum minimum annual Mean Mean annual minimum minimum annual Mean groundwater levels (mAHD) groundwater levels (mAHD) groundwater levels (mAHD) 6 groundwater levels (mAHD) 6 groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) groundwater levels (mAHD) 00 50 50 100 100 150 150 200 200 groundwater levels (mAHD) groundwater levels (mAHD) 7 7 groundwater levels (mAHD) 7 07 0 50 50 100 100 150 150 200 200 Mean annual minimum minimum annual Mean Mean annual minimum minimum annual Mean 6 Mean annual minimum minimum annual Mean 00 50 50 100 100 150 150 200 200 minimum annual Mean Mean annual minimum minimum annual Mean Mean annual minimum minimum annual Mean 6 Mean annual minimum minimum annual Mean Mean annual minimum minimum annual Mean 6 06 0 50 50 100 100 150 150 200 200 groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) groundwater levels (mAHD) groundwater levels (mAHD) groundwater levels (mAHD) 0Flow duration 50Flow duration (days) 100 (days) 150 200 groundwater levels (mAHD) No-flowNo-flow duration duration (days) (days) Mean annual minimum minimum annual Mean minimum annual Mean Mean annual minimum minimum annual Mean minimum annual Mean 6 6 Mean annual minimum minimum annual Mean minimum annual Mean 0 50Flow durationFlow 100 duration (days) 150 (days) 200 minimum annual Mean 6 minimum annual Mean 06 0No-flow 50No-flow duration 50 100 duration (days) 100 150(days) 150 200 200 groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD) groundwater levels (mAHD) groundwater levels (mAHD) groundwater levels (mAHD) groundwater levels (mAHD) 8.5 08.5 0 50Flow 50 durationFlow 100 duration (days) 100 150 (days) 150 200 200 8.508.50 50No-flow 50 100 duration 100 (days) 150 150 200 200 8.5 8.5 8.5 8.5 No-flow duration (days) 8.5 Flow durationFlow duration (days) (days) 8 8.58 No-flowNo-flow duration duration (days) (days) 8.58 8 8.58 8 8 8 8.5 8.5 8.57.5 8.57.58 D D 7.58 7.5 7.58 7.58 7.5 7.5 87 7.587 8 8 7.57 7 7.5 7.5 7 7 7.56.5 7.56.5 7 7 7 6.57 7.5 7.5 6.5 7 Mean annual minimum minimum annual Mean minimum annual Mean 7 6.576 6.576 groundwater level (mHD) groundwater level (mHD) 6.5 minimum annual Mean 6.5 Mean annual minimum minimum annual Mean Mean annual minimum minimum annual Mean minimum annual Mean 6 6 groundwater level (mHD)

groundwater level (mHD) 6.5

6.5 minimum annual Mean Mean annual minimum minimum annual Mean groundwater level (mAHD) groundwater level (mAHD) groundwater level (mAHD)

7 7 groundwater level (mAHD) 00 50 50 100 100 150 150 200 200

Mean annual minimum minimum annual Mean 00 50 50 100 100 150 150 200 200 6.5 6.5 Mean annual minimum minimum annual Mean 6 06 0 50 50 100 100 150 150 200 200 groundwater level (mHD) 6.5 0 50 100 150 200 Mean annual minimum minimum annual Mean groundwater level (mHD) 6.5 0 50 100 150 200 Mean annual minimum minimum annual Mean

groundwater level (mAHD) No-flowNo-flow duration duration (days ) (days ) Flow durationFlow duration (days) (days) groundwater level (mAHD) 0No-flow 50No-flow duration duration 100(days ) (days 150 ) 200 Mean annual minimum minimum annual Mean minimum annual Mean 00 50Flow 50durationFlow 100 duration (days) 100 150 (days) 150 200 200 6 06 50 100 150 200 groundwater level (mHD) 6.5 groundwater level (mHD) 6.5 Mean annual minimum minimum annual Mean minimum annual Mean

Flow duration (days) groundwater level (mAHD) groundwater level (mAHD) No-flowNo-flow duration duration (days ) (days ) 00 50Flow 50duration 100 (days) 100 150 150 200 200 00 50 50 100 100 150 150 200 200 Flow durationFlow duration (days) (days) No-flowNo-flow duration duration (days ) (days )

Figure B3 Figure B4 Relationship between duration of Relationship between duration of wet season river flow events and wet season no-flow events and groundwater levels at bores groundwater levels at bores (a) U1, (b) 7/04, (c) 9/04 and (d) 6/04 (a) U1, (b) 7/04, (c) 9/04 and (d) 6/04

43 C Appendix C – Relationship between bores

Ecological water requirements of the Lower De Grey

a 11.0

10.5

10.0

BoreU1 (mAHD) 9.5

9.0 9.0 9.5 10.0 10.5 11.0 Bore 3/04 (mAHD)

B 9.5

9.0

8.5

8.0

7.5 Bore9/04 (mAHD) 7.0

6.5 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 Bore T2 (mAHD)

C 11.0 10.5 10.0 9.5 9.0 8.5

Bore6/04 (mAHD) 8.0 7.5 7.0 9.0 9.5 10.0 10.5 11.0

Bore U1 (mAHD)

Figure C1 (a) Bores U1 and 3/04, (b) Bores 9/04 and T2 and (c)Bores 6/04 and U1

44 Appendix D – Pool-depth contour plots D

Ecological water requirements of the Lower De Grey

a a

a a fifi a fifia a fifi a

a fifia

a fifia Ba fifiB b a b fi b bfi fi fi fi fi b fi fi fi fl fi

b b fi fi fi b fi b bfi c fi fi fi Figure Dfi2 Homestead Pool (a) 5th percentile, (b) 20th percflentile, (c) 50th C percenCtile c fi cc fiFigure D2 Homestead Pool (a) 5th percentile, (b) 20th percentile, (c) 50th Figure D1 J96 Pool (a) 5th percentile, (b) 20th pepercercnentiletil,e (c) 50th percentile Figure D1 J96 Pool (a) 5th percentile, (b) 20th percentile, (c) 50th percentile fl c fi Figure D1 J96 Pool (a) 5th percentile, (b) 20th peFircguenrteile D, 3(c ) 50Mtahk panerykcenarrtaile P ool (a) 5th percentile, (b) 20th percentile, (c) 50th percentile c Figure D2 Homestead Pool (a) 5th percentile, (b) 20th percentile, (c) 50th percentile c fi c Figure D1 J96 Pool (a) 5th percentile, (b) 20th perFiceguntriele D, 2(c ) 50 Htho mpesrcteadentil Peoo l (a) 5th percentile, (b) 20th percentile, (c) 50th c fi c fi pe rcentile fl Figure D1 J96 Pool (a) 5th percentile, (b) 20th percentile, (c) 50th percentile Figure D1 J96 Pool (a) 5th percentile, (b) 20th percFieguntirle, D(c3) 50Mtha pkeanrcykenatrrilea Pool (a) 5th percentile, (b) 20th percentile, (c) 50th Figure D1 Figurepercen D2tile J96 Pool (a) 5th percentile, Homestead Pool (a) 5th percentile, (b) 20th percentile, (c) 50th percentile (b) 20th percentile, (c) 50th percentile

45 D Ecological water requirements of the Lower De Grey

a

a a a

a

a B

fi a fl

fi fl

fi fl

fi fl

fi fl

fi fl C fl Figure D3 Makanykarra Pool (a) 5th percentile, (b) 20th percentile, (c) 50th fl percentile Figure D3 Makanykarra Pool (a) 5th percentile, (b) 20th percentile, (c) 50th percentile fl Figure D3 Makanykarra Pool (a) 5th percentile, (b) 20th percentile, (c) 50th percentile

fl Figure D3 Makanykarra Pool (a) 5th percentile, (b) 20th percentile, (c) 50th fl percentile Figure D3 Makanykarra Pool (a) 5th percentile, (b) 20th percentile, (c) 50th pe rcentile fl Figure D3 Makanykarra Pool (a) 5th percentile, (b) 20th percentile, (c) 50th Figurepercen tilD3e Makanykarra Pool (a) 5th percentile, (b) 20th percentile, (c) 50th percentile

46 Appendix E – Total annual wet season flow volume, probability of exceedence, recharge classes E and water availability Ecological water requirements of the Lower De Grey

Year Flow vol. (ML) Probability Recharge class Water availability 1986 0.00 0 1 Drought 1998 0.00 0.030 1 2005 0.00 0.061 1 1990 7306.84 0.091 1 1992 13491.00 0.121 1 1991 31927.36 0.152 1 1975 61710.39 0.182 2 Dry 1994 171986.92 0.212 2 2008 199348.78 0.242 2 1989 294605.08 0.273 2 2011 398899.62 0.303 2 2001 413712.83 0.333 2 1979 416665.17 0.364 2 1985 448822.15 0.394 2 2003 489787.98 0.424 3 >average 2010 490914.08 0.455 3 1993 584932.59 0.485 3 2009 641250.07 0.515 3 1984 771827.96 0.545 3 1996 1180877.00 0.576 3 1987 1325060.48 0.606 3 2006 1493298.19 0.636 3 1977 1520426.88 0.667 3 1978 1575400.39 0.697 3 1995 1592525.56 0.727 3 1976 1614465.74 0.758 3 1997 1657406.19 0.788 3 2007 1713301.41 0.818 3 2002 2113316.32 0.848 4 wet 1983 2348103.87 0.879 4 1988 2974696.29 0.909 4 2004 3228096.07 0.939 4 1999 4698901.61 0.970 4 2000 7022031.62 1.000 4 1980 no data 1981 no data 1982 no data

47 Appendix F – Additional ecological water F requirement sites

Ecological water requirements of the Lower De Grey

Additional groundwater-dependent set static water-level criteria. The EWRs were ecosystems – river pools and riparian set for three water availability conditions. vegetation – have been identified south of These were characterised by percentile the highway near the Namagoorie borefield groundwater levels as follows: (Figure F1). Although data for these sites are limited, a brief description of their hydrology • drought conditions: pool or and likely ecological values are presented groundwater levels <5th percentile here. We have followed the approach described in the body of this report, and • dry conditions: pool or groundwater summarised here, to set the EWRs. levels >20th percentile • average/above-average conditions: Ecological!( water requirements pool or groundwater levels >50th approach!( !( percentile.

To account!( for!( the!( natural variability in (! water availability we determined EWRs for (! ! !( ! a range of climatic conditions!( rather than !( !( ! !( !( !( ! (! !( (! !( -E1- !7/04 ! (! ") Great Northern Highway !( ! ! ! !

!( (! H1 (! Triangle Pool De Grey River !( !( !( !( !( Nardeegeecarblin Pool(! I2 (! H2 !( !( !( !( !( !( !( F1 (! !( Legend Location map !( !( !( !( Monitoring Bores (! !( ! EWR bore ´ DERBY !( !( !( !( ! PORT HEDLAND !( Production bore (! !( !( (! Other bore Shaw River NEWMAN !( Poo!(ls !( (! ") EWR pool !( Other pool Government of Government oWf esternWest eAustraliarn Australia (! Department of Water Namagoorie borefield 0 1.25 2.5 5 Department of Water

Recent alluvium Kilometres Map reference:Map refer eC2219_020nce: C2219_020 Figure F1 !( Location of additional groundwater-dependent ecosystems

48 F Ecological water requirements of the Lower De Grey

River pools Groundwater dependence Triangle Pool Pool water levels are not monitored at Triangle Pool. The nearest bore, Triangle Pool is a semi-permanent pool Cuttangunah Well, is about 1 km from the (persists 60 to 99 per cent of the time) pool but has not been monitored since 1999. located approximately 1.3 km upstream of Coolenar Pool near the railway bridge. The strength of the relationship between the De Grey River pools and groundwater levels Ecological values was demonstrated in the body of this report. Assuming this relationship holds upstream of No specific data on the pool’s flora and the EWR study area, levels in Cuttangunah fauna are available. However, it is likely Well should reflect the water regime of to support similar biota to other semi- Triangle Pool. Figure F2 shows available permanent pools on the lower De Grey groundwater levels and percentiles. River. As such, aquatic macrophytes, macroinvertebrates, fish, waterbirds and riparian vegetation may occur in and around the pool.

18.0

17.5

17.0

16.5

16.0

15.5 Groundwater level (mAHD) 15.0 81 81 83 78 80 80 80 80 83 84 84 98 78 79 79 80 80 82 82 80 80 81 81 81 ------Jul Jan Jan Jan Jun Jun Oct Oct Apr - Apr - Sep Dec Aug Aug Aug Aug Nov Nov Mar Mar Mar May May May

Cuttangunnah Well 5th% 20th% 50th %

Figure F2 Cuttangunah Well groundwater levels and percentiles

A transect running from the bore to Triangle Pool was created using LiDAR data. Ground elevations and bore data support the semi-permanent nature of the pool, showing it persists in all but the driest years (Figure F3).

49 F Ecological water requirements of the Lower De Grey

27

25

23

21

19

17

Groundwater level/ elevation (mAHD) 0 500 1000 1500 2000 2500 3000 3500

Ground elevation 5th% 20th% 50th%

Figure F3 Elevation across transect between Cuttangunah Well (left) and Triangle Pool (right)

Nardeegeecarblin Pool Groundwater dependence

Nardeegeecarblin Pool is also semi- Pool water levels are not monitored permanent. It is located approximately 3 km at Nardeegeecarblin Pool. However, upstream of Coolenar Pool and 1.7 km south groundwater levels have been recorded at of Triangle Pool. bore H2, about 0.6 m south of the pool, since 1974. Figure F4 shows available groundwater levels and percentiles. Ecological and cultural values

No specific biotic data are available for Following the approach used for Triangle Nardeegeecarblin Pool. However, as a semi- Pool, groundwater levels at bore H2 were permanent pool it is also likely to support considered representative of levels in aquatic macrophytes, macroinvertebrates, Nardeegeecarblin Pool. fish, waterbirds and riparian vegetation. A transect running across Nardeegeecarblin Triangle and Nardeegeecarblin pools Pool from bores H2 to H1 was created using make up Nyartinjikapunya (Twin) Pool. LiDAR data. Ground elevations and bore Nyartinjikapunya Pool is listed with the data support the semi-permanent nature Department of Indigenous Affairs as a of the pool, showing it persists in all but the permanent site. At times these pools also driest years (Figure F5). join with Coolenar Pool. Nyartinjikapunya Pool is a popular picnic and camping spot and thus some disturbance to the bank has occurred.

50 F Ecological water requirements of the Lower De Grey

Riparian vegetation the De Grey and to grassland with emergent Corymbia flavescens/E. victrix along the Three vegetation monitoring transects were Shaw River. established in 2001 upstream of the highway: Groundwater dependence 1. 4 km east of bore I2, supporting E. camaldulensis and M. argentea In the Pilbara M. argentea and E. camaldulensis generally occur in areas 2. 1.5 km south-east of bore I2, where the watertable is less than 10 m below supporting E. camaldulensis and ground level. M. argentea

3. 800 m south-east of bore H1, Bores I2 and F1 were selected as being supporting a stand of E. victrix over representative of groundwater levels in the spinifex and buffel grass. area. Data have been recorded at both sites since 1974 (Figures F6 and F7). During Monitoring data (HGM 2002) and vegetation this time water levels have remained within mapping (Loomes & Braimbridge 2010) 10 m of the ground surface. However, in shows dense forest of M. argentea and more recent years (1994–2008) shallower E. camaldulensis occur along Triangle depths of 5.5 to 6.5 m have been recorded and Nardeegeecarblin pools and further at F1 compared with 8.5 to 9.5 m at I2. This upstream. Below the confluence of the Shaw suggests riparian species near bore F1 may and De Grey rivers the vegetation thins to have a greater degree of groundwater E. camaldulensis/E. victrix open forest along dependence.

22.5

22

21.5

21

20.5

20 Groundwater level (mAHD) 19.5 83 74 86 89 90 77 79 82 80 80 96 00 02 04 76 85 80 91 92 93 94 95 81 80 81 81 01 06 08 ------Jul Jul Jul Jul Jan Jan Jun Jun Jun Jun Oct Feb Sep Feb Sep Sep Sep Dec Aug Aug Nov Nov Mar Mar Mar May May May May

I2 5th% 20th% 50th%

Figure F4 Bore H2 groundwater levels and percentiles

51 F Ecological water requirements of the Lower De Grey

22.5

22

21.5

21

20.5

20 Groundwater level (mAHD) 19.5 80 82 86 89 83 90 74 77 79 96 00 02 04 80 81 85 76 81 81 91 92 93 94 95 80 01 80 06 08 ------Jul Jul Jul Jul Jan Jan Jun Jun Jun Jun Oct Sep Sep Feb Sep Feb Sep Dec Aug Aug Nov Nov Mar Mar Mar May May May May

I2 5th% 20th% 50th%

Figure F5 Elevation across transect between bores H1 (left) and H2 (right)

22.0 21.5 21.0 20.5 20.0 19.5 19.0 18.5 18.0 17.5

Groundwater level (mAHD) 17.0 74 90 76 77 80 81 82 83 83 91 92 93 93 94 85 85 89 97 00 01 02 03 04 06 08 78 79 95 90 ------Jul Jun Jun Jun Oct Oct Apr - Apr - Apr - Apr - Feb Feb Feb Feb Sep Sep Sep Dec Dec Dec Aug Aug Aug Nov Mar Mar May May May

H2 5th% 20th% 50th%

Figure F6 Bore 12 depth to groundwater and percentiles

52 F Ecological water requirements of the Lower De Grey

4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 Depth to groundwater (m) to groundwater Depth Jul- 09 Jul- 98 Jan- 04 Jan- 93 Oct- 06 Oct- 95 Apr- 01 Feb- 82 Dec- 73 Aug- 76 Aug- 87 Nov- 84 May- 79 May- 90

F1 5th% 20th% 50th%

Figure F7 Bore F1 depth to groundwater and percentiles

Summary of historic hydrological data

Table F1 Historic groundwater level/depths

Bore/pool Percentile Groundwater Depth to Frequency Median level (mAHD) groundwater level/ depth duration (m) met level/ depth met (months) Cuttangunah Well/ <5th 15.84 - 4 1.5 Triangle Pool >20th 16.06 - 8 3.5 >50th 16.49 - 8 1.5 Nardeegeecarblin <5th 19.05 - 3 3 Pool/H2 >20th 19.32 - 9 3 >50th 19.72 - 6 3 I2 <5th 20.21 8.77 11 2.5 >20th 20.59 8.39 9 2.5 >50th 20.97 8.01 7 3 F1 <5th 24.13 6.45 9 1 >20th 24.57 6.01 16 3 >50th 25.04 5.54 13 2

53 F Ecological water requirements of the Lower De Grey

Ecological water requirements Nardeegeecarblin Pool/bore H2 summary Drought conditions To allow for inter-annual variation in river flow and water availability, the frequency • Groundwater level of <19.05 mAHD and duration of recommended levels have at bore H2 not to be exceeded more been set over a five-year period. Median than three times for a duration of (middle) values, calculated for river pool more than three months in a five-year and groundwater levels, were used in dry period. and average conditions. Frequencies and durations for drought conditions were based Dry conditions on results of the Yule River groundwater drawdown trial. • Groundwater level of >19.32 mAHD at bore H2 to be reached more than Triangle Pool/Cuttangunah Well four times for a duration of nine months in a five-year period. Drought conditions Average conditions

• Groundwater level of <15.84 mAHD • Groundwater level of >19.72 mAHD at Cuttangunah Well not to be at bore H2 to be reached more than exceeded more than three times for four times for a duration of six months a duration of more than three months in a five-year period. in a five-year period. Bore I2 Dry conditions

Drought conditions • Groundwater level of >16.06 mAHD at Cuttangunah Well to be reached more than four times for a duration of • Groundwater level of <20.21 mAHD nine months in a five-year period. at bore I2 not to be exceeded more than three times for a duration of Average conditions more than three months in a five-year period. • Groundwater level of >16.49 mAHD Dry conditions at Cuttangunah Well to be reached more than four times for a duration of six months in a five-year period. • Groundwater level of >20.59 mAHD at bore I2 to be reached more than four times for a duration of nine months in a five-year period.

Average conditions

• Groundwater level of >20.97 mAHD at bore I2 to be reached more than four times for a duration of six months in a five-year period.

54 F Ecological water requirements of the Lower De Grey

Bore F1

Drought conditions

• Groundwater level of <24.13 mAHD at bore F1 not to be exceeded more than three times for a duration of more than three months in a five-year period.

Dry conditions

• Groundwater level of >24.57 mAHD at bore F1 to be reached more than four times for a duration of nine months in a five-year period.

Average conditions

• Groundwater level of >25.04 mAHD at bore F1 to be reached more than four times for a duration of six months in a five-year period.

Recommendations

Applying the EWR as measureable EWP criteria will require continued monthly monitoring of bore (H2, I2 and F1) levels at the target sites. Ongoing monitoring at the Coolenar Pool gauging station is also required to determine annual recharge classes.

It is also recommended that pool-level monitoring be instigated at Triangle and Nardeegeecarblin pools and shallow bores be installed close to both pools. In addition, bathymetry surveys of both pools is recommended.

55 Appendix G – Map disclaimer - G figures 1, 7 and 8

Ecological water requirements of the Lower De Grey

Datum and projection information

Vertical datum: Australian Height Datum (AHD) Horizontal datum: Geocentric Datum of Australia 94 Projection: MGA 94 Zone 50 Spheroid: Australian National Spheroid

Project information

Client: Robyn Loomes Map Author: Michelle Antao Filepath: J:\gisprojects\Project\C_series\C2219\0020_DeGrey_Maps\mxd\ Filename: DeGrey_Location_Map.mxd, DeGrey_DTGW_Veg_Map.mxd Compilation date: March, 2011-04-29

Disclaimer

These maps are a product of the Department of Water, Water Resource Use Division and were printed as shown. These maps were produced with the intent that they be used for information purposes at the scale as shown when printing.

While the Department of Water has made all reasonable efforts to ensure the accuracy of this data, the department accepts no responsibility for any inaccuracies and persons relying on this data do so at their own risk.

Sources

The Department of Water acknowledges the following datasets and their custodians in the production of these maps:

• Hydrography, Linear (Hierarchy) – DoW – 05/11/2007

• Pilbara Pool Mapping – DoW – 2009

• Road Centrelines – DoW – Current

• Towns –DLI – Current

• WA Coastline, WRC (Poly) – DoW – 20/07/2006

• WIN sites – DoW – Current

56 Shortened forms

Ecological water requirements of the Lower De Grey

AHD Australian Height Datum

ANZECC Australian and New Zealand Environment and Conservation Council

ARMCANZ Agricultural and Resource Management Council of Australia and New Zealand

ELOHA Ecological Limits of Hydrologic Alteration

EWP Environmental water provisions

EWR Ecological water requirements

LiDAR Light Detection and Ranging

SKM Sinclair Knight Merz

WRC Water and Rivers Commission (former)

WRM Wetland Research & Management

57 Glossary

Ecological water requirements of the Lower De Grey

Abstraction The permanent or temporary withdrawal of water from any source of supply, so that it is no longer part of the resource of the locality. Alluvium Fragmented rock transported by a stream or river and deposited as the river floodplain. Aquifer A geological formation or group of formations capable of receiving, storing and transmitting significant quantities of water. Usually described by whether they consist of sedimentary deposits (sand and gravel) or fractured rock. Bore A narrow, normally vertical hole drilled in soil or rock to measure or withdraw groundwater from an aquifer. Ecological water requirement The water regime needed to maintain ecological values of water-dependent ecosystems at a low level of risk. Ecosystem A community or assemblage of communities of organisms, interacting with one another, and the specific environment in which they live and with which they also interact, e.g. a lake. Includes all the biological, chemical and physical resources and the interrelationships and dependencies that occur between those resources. Environment Living things, their physical, biological and social surroundings and the interactions between them. Flow Streamflow in terms of m3/second, m3/day or ML/annum. May also be referred to as discharge. Groundwater Water that occupies the pores and crevices of rock or soil beneath the land surface. Groundwater-dependent An ecosystem that is dependent on groundwater for its ecosystems existence and health. Habitat The area or natural environment in which an organism or population normally lives. A habitat is made up of physical factors such as soil, moisture, range of temperature and availability of light as well as biotic factors such as food availability and the presences of predators. Hydrology The study of water, its properties, movement, distribution and utilisation above, on or below the Earth’s surface. Hydrogeology The hydrological and geological sciences concerned with the occurrence, distribution, quality and movement of groundwater, especially relating to the distribution of aquifers, groundwater flow and groundwater quality. Invertebrate An animal without a backbone. Lifecycle The series of changes in the growth and development of an organism from its beginning as an independent life form to its mature state in which offspring are produced.

58 Ecological water requirements of the Lower De Grey

Macrophyte A plant, especially an aquatic or marine plant, large enough to be visible to the naked eye. Phreatophyte A plant (often relatively deep-rooted) that obtains water from a permanent ground supply or from the watertable. Riparian vegetation Plant communities along the river margins and banks or at the interface between land and a river or stream. Stygofauna Fauna that live within groundwater systems, such as caves and aquifers, or more specifically small, aquatic groundwater invertebrates. Surface water Water flowing or held in streams, rivers and other wetlands on the surface of the landscape. Water regime A description of the variation of flow rate or water level over time. It may also include a description of water quality. Wetland Areas that are permanently, seasonally or intermittently waterlogged or inundated with water that may be fresh, saline, flowing or static, including areas of marine water where the depth at low tide does not exceed 6 m.

59 References

Ecological water requirements of the Lower De Grey

Australian and New Zealand Environment and Conservation Council and Agricultural and Resource Management Council of Australia and New Zealand 2000,. Australian and New Zealand guidelines for fresh and marine water quality, National Water Quality Management Strategy, paper no. 4, Australian and New Zealand Environment and Conservation Council and Agricultural and Resource Management Council of Australia and New Zealand, Canberra.

Beesley L 2006, ‘Environmental stability: its role in structuring fish communities and life history strategies in the , Western Australia’, School of Animal Biology, University of Western Australia, Perth.

Braimbridge MJ & Malseed BE 2007, Ecological water requirements of the lower Ord River, Environmental water report series, report no. 4, Department of Water, Government of Western Australia, Perth.

Davidson W 1974, Hydrogeology of the De Grey River area, Western Australia, Geological Survey of Western Australia, record 1973/27.

Dobbs R & Davies P 2009, Long term ecological research on a Pilbara river system – analysis of long term aquatic monitoring dataset, Centre of Excellence in Natural Resource Management, University of Western Australia: Perth.

Douglas MM, Bunn SE, & Davies PM 2005, ‘River and wetland food webs in Australia’s wet-dry tropics: general principles and implications for management’, Marine and Freshwater Research 56: 329–342.

Eamus D, Froend R, Loomes R, Hose & G, Murray B 2006, ‘A functional methodology for determining the groundwater regime needed to maintain the health of groundwater- dependent vegetation’, Australian Journal of Botany 54: 97–114.

Environment Australia 2001, Directory of important wetlands in Australia, third edition, Environment Australia, Canberra.

Graham J 2001, The root hydraulic architecture of Melaleuca argentea, University of Western Australia.

HGM 1998, East Pilbara water supply augmentation: biological assessment, prepared for the Water Corporation, HGM, Perth.

Howe P, Pritchard J, Cook P, Evans R, Clifton C & Cooling M 2007, Project REM1 – a framework for assessing the environmental water requirements of groundwater dependent ecosystems, report 3 implementation, Resource & Environmental Management PL, Kent Town, SA.

60 Ecological water requirements of the Lower De Grey

Humphreys G 2000, ‘Ecological water requirements of groundwater dependent riverine woodlands in Hope Downs project area’, Management of groundwater dependent vegetation in the central Pilbara iron ore mining province, Water and Rivers Commission, DRD and ERG, University of Western Australia.

Kendrick P & Stanley F 2002, ‘Pilbara 4 (PIL 4 – Roebourne synopsis)’, A biodiversity audit of Western Australia’s 53 biogeographical subregions in 2002,.Department of Conservation and Land Management, Perth.

Kennard M, Pusey B, Olden J, Mackay S, Stein J & Marsh N 2010, ‘Classification of natural flow regimes in Australia to support environmental flow management’,Freshwater Biology 55: 171–193.

Loomes R 2010, Determining water level ranges of Pilbara riparian vegetation, Environmental water report series, report no. 17, Department of Water, Government of Western Australia, Perth.

Loomes R & Braimbridge MJ 2010, Lower De Grey River: ecological values and issues, Environmental water report series, report no. 12, Department of Water: Government of Western Australia, Perth.

Morgan D, Ebner B & Beatty S 2009, Fishes in groundwater dependent pools of the Fortescue and Yule rivers, Pilbara, Western Australia, Centre for Fish and Fisheries Research, Murdoch University, Perth.

Muir Environmental 1995, Possible long-term impacts of the Yandicoogina iron ore project on riverine species along Creek, unpublished report prepared for BHP and AGC Woodward-Clyde, Perth.

MWH Australia Pty Ltd 2007, Atlas Iron Limited, Pardoo direct shipping iron ore surface water hydrology, MHW, Perth.

Pettit NE & Froend R 2001, ‘Variability in flood disturbance and the impact on riparian recruitment in two contrasting river systems’, Wetlands Ecology and Management 9: 13–25.

Pinder AM & Leung A 2009, Conservation status and habitat associations of aquatic invertebrates in Pilbara coastal river pools, a report to the Department of Water. Science Division, Department of Environment and Conservation, Perth.

Poff N, Richter B, Arthington A, Bunn S, Naiman R, Kendy E, Acreman M, Apse C, Bledsoe B, Freeman M, Henrikson J, Jacobson R, Kennen J, Merritt D, O’Keefe J, Olden J, Rogers K, Tharme R& Warner A 2010, ‘The Ecological Limits of Hydrologic Alteration (ELOHA): a new framework for developing regional environmental flow standards’,Freshwater Biology 55: 14–170.

Roberts J, Young B & Marston F 2000, Estimating the water requirements of floodplain wetlands: a guide, occasional paper 04/00, Land and Water Resources Research and Development Corporation, Canberra.

61 Ecological water requirements of the Lower De Grey

Sinclair Knight Merz 2010, Lower De Grey groundwater model, Sinclair Knight Merz, Adelaide.

Storey A 2003, Lower Ord River fish habitat survey, a report to the Water and Rivers Commission, University of Western Australia, Perth.

Strategen 2006, Draft Bulgarene borefield (De Grey River) vegetation sensitivity study, a report to the Water Corporation, Perth.

Trayler K, Malseed BE & Braimbridge MJ 2006, Environmental values, flow related issues and objectives for the lower Ord River, Western Australia, Environmental water report series, report no. 1, Department of Water, Government of Western Australia, Perth. van Dam R, Storey A, Humphrey C, Pidgeon B, Luxon R & Hanley J 2005, Bulgarene borefield (De Grey River) Port Hedland water supply aquatic ecosystems study, National Centre for Tropical Wetland Research, Darwin.

Water and Rivers Commission 2000, Statewide policy no. 5: Environmental water provisions policy for Western Australia, Water and Rivers Commission: Perth.

Worley Parsons 2005, De Grey groundwater resources: Bulgarene borefield model, volume 1 – model development and calibration, Worley Parsons, Perth.

Wetland Research & Management 2009, Hope Downs 4 aquatic ecosystem surveys: dry season sampling 2008, unpublished report by Wetland Research & Management to Rio Tinto Pty Ltd, Perth.

62

Ecological water requirements of the Lower De Grey River

Department of Water Looking after all our water needs 168 St Georges Terrace, Perth, Western Australia Environmental water report series PO Box K822 Perth Western Australia 6842 Phone: 08 6364 7600 Report no. 20 Fax: 08 6364 7601 June 2012 www.water.wa.gov.au

3053–30–0612