Dealing with salinity in Wheatbelt Valleys - Department of Water

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Hatton and Ruprecht Annual Flow-Weighted Salinity (mg/L TDS) Flow (m3/s) 4500 4000 3500 3000 2500 2000 1500 1000 6000 5000 4000 3000 2000 1000 500 0 Prediction 0 1940 1960 1980 2000 Year 2020 2040 2060 Salinity Data Indicative Range of Salinity Increase 10 Yr Backward Moving Average Figure 11: Salinity trend and prediction for Blackwood River at Darradup (adapted from Bowman & Ruprecht 2000). Calibration Prediction: Scenario 1 - Salt-affected land area doubles Prediction: Scenario 2 - Salt-affected land area trebles Prediction: Scenario 3 - Salt-affected land area quadruples 21/01/82 24/01/82 27/01/82 30/01/82 Figure 12: Predicted peak flows of the Blackwood River at Darradup with rainfall as recorded in January 1982 (Cyclone Bruno), under expanding source areas associated with rising regional watertables. The lower curve is the calibrated event as it happened under prevailing levels of groundwater discharge areas in 1982. That flood event had major impacts along the lower Blackwood to towns like Nannup. The three higher curves represent what may happen if groundwater discharge areas double, treble or quadruple. – 12 –
THE FUTURE In looking at the future of the wheatbelt catchments, it is not possible to divorce the health of the ecohydrological system from that of the communities that derive their living and wellbeing from these catchments. The Avon Basin, for instance, produces agriculture worth some $1.5 billion, and is home to 54,000 people. These rural stakeholders are affected by declining terms of trade for agricultural products, and the loss of people and services from rural communities. At the same time, growing environmental awareness regarding catchment health, and a growing intention to assert their values, translate to residents of Perth (1.3 million people) having a larger influence on natural resource management, including areas remote from Perth. In any debate about wheatbelt catchment management, it is crucial that an objective picture regarding the future of the rivers be painted and understood by everyone. The rivers do not look like they once did, nor will they look like they do now in the future. The decisions we take must be considered in the context of the future state of these systems if we do nothing, not against the background of how they used to look or how they look now. Our technical ability to paint this picture is limited but must be developed. As for what options are open to significantly improve the state of the wheatbelt catchments, it is useful to distinguish among the goals of reducing nutrient loads, salinity, flooding and inundation, and waterlogging. Each of these has a set of options that may be more or less feasible and attractive. Viney & Sivapalan (2001) concluded on the basis of simulation modelling that strategic revegetation (of particular sub-catchments) had the potential to disproportionately reduce sediment and nutrient delivery to the Swan estuary, although these results would clearly not hold in the case of large flood events arising from the upper catchment. It is difficult to imagine revegetation at the scale of the Avon that could intercept nutrients and sediment on those occasions when summer rainfall inland leads to the kind of flows and loads observed in January 2000. It may be possible for new farming systems to reduce the inputs of agricultural fertilisers in large scale agriculture, but if the origin of most sediments delivered to the Swan estuary are remobilised from the river bed and banks from upstream, then the source of sediment and particulate phosphorous may in effect be inexhaustible. – 13 – Hatton and Ruprecht The options for flood mitigation include revegetation of the variable source areas (i.e. saline discharge areas), increasing the storages along the chains of lakes, or widespread revegetation with trees. These options are not mutually exclusive, but the impediments to adoption of the latter are widely recognised. Lacking the development of commercially attractive tree crops with a product market that can sustain millions of hectares of production, it is unlikely to ever happen and will certainly not happen in the immediate future. Revegetation of discharge areas (e.g. with salttolerant vegetation) is more technically and economically feasible, but the effectiveness of this approach in mitigating flood risk is untested and is unlikely to dramatically mitigate risk, particularly in winter. The potential to create detention basins by raising the outlets of natural lakes and thus mitigate risk is higher, but also untested in practice. These basins may create a temporary impoundment, which releases water in times of “diluting high flows”, but not floodflows. The increasing likelihood of flooding affects not only agricultural land, but has a major impact on infrastructure such as roads, railways and townsites. The potential economic value of protecting these assets is probably much higher than for agricultural land and as such there may be greater opportunity to look at multiple objectives of mitigating the impacts of floods on infrastructure and agricultural land. The options for reducing inundation and waterlogging are similar to flood mitigation. However, the emphasis is more likely to be on surface water management, water harvesting, and engineering and vegetation options to increase discharge. Hatton & Salama (1999) concluded that neither revegetation nor engineering was likely to recover the wheatbelt rivers from salinity. However, it is now widely recognised that engineering can be effective in reducing the impacts and extent of land salinisation on infrastructure and natural assets, as well as in keeping land under crops. It is also generally acknowledged that even if the long-term strategy is to revegetate, the immediate protection of land and assets can require engineering. Such practices are already being employed in places such as Lake Toolibin, where surface water diversions and groundwater pumping are beginning to protect the reserve ahead of intended revegetation in the surrounding catchment.
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Foreword Dealing with Salinity in W
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1Day one: Monday 30th July. Field t
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Papers Dealing with Salinity in Whe
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Ali and Coles biggest challenges fa
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Ali and Coles erosion, maintenance
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Ali and Coles expected under these
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Ali and Coles Coles, N.A. & Ali, M.
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Commander, Schoknecht, Verboom and
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Page 33 and 34: Commander, Schoknecht, Verboom and
Page 41 and 42: APPRECIATING AND CREATING OUR HISTO
Page 43 and 44: services. The Government responded
Page 45 and 46: WHEATBELT VALLEYS IN DIFFICULTIES T
Page 47 and 48: argue that they were really abnorma
Page 49 and 50: 1990s, the wheatbelt valleys in par
Page 51 and 52: REFERENCES Agstats (1997). Agricult
Page 53 and 54: George and Coleman two to four fold
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Page 65 and 66: George and Coleman advantages of so
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Page 69 and 70: George and Coleman Venture Economy
Page 71 and 72: George and Coleman Lawrence, C. (19
Page 73 and 74: Hatton and Ruprecht WATCHING THE RI
Page 75 and 76: Since the mid 1970s annual rainfall
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Page 79 and 80: Salinity Monthly streamflow (ML) 10
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Page 99 and 100: Lloyd 0 -500 -1000 -1500 -2000 -250
Page 101 and 102: Lloyd Table 3. Sheep grazing days i
Page 103 and 104: Lloyd Hectares project to provide w
Page 105 and 106: INTRODUCTION The Lake Chinocup Catc
Page 107 and 108: agriculture) in various stages, the
Page 109 and 110: - 3,477 ha of remnant vegetation or
Page 111 and 112: Scientists talk of up to 30% of the
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Page 117 and 118: eliminates drainage through the nex
Page 119 and 120: REFERENCES Dawes, W.R., Stauffacher
Page 121 and 122: Pannell ECONOMICS, SOCIETY AND ENVI
Page 123 and 124: Pannell • the area of land protec
Page 125 and 126: Pannell Proposals to construct majo
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Page 129 and 130: Pannell investments in long-term la
Page 131 and 132: Pannell Pannell, D.J. (2001). Dryla
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Porter, Bartle and Cooper Table 3:
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Porter, Bartle and Cooper operation
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Porter, Bartle and Cooper Increase
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Porter, Bartle and Cooper support i
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Porter, Bartle and Cooper that is a
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CASE STUDY - TOOLIBIN LAKE AND CATC
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• The distribution, storage and m
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Secondly, there is a set of practic
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within three categories: relationsh
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CONCLUSIONS Actions to protect and
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FIELD TOUR LOCATIONS FIELD TOUR NOT
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COLES FARM “Avon River Basin Over
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Conference Outcomes Dealing with Sa
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with Salinity in Wheatbelt Valleys:
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with Salinity in Wheatbelt Valleys
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Photo Gallery 2 Dealing with Salini
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APPENDIX 1 BACKGROUND HYDROLOGY AND
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WHEATBELT HYDROLOGY Flow in the Yil
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Flow (ML) STREAM SALINITY Salt Rive
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APPENDIX 2 WATER MANAGEMENT OPTIONS
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APPENDIX 3 MANAGING WATER AND SALIN
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SUMMARY- TIMELINE OF RECENT SIGNIFI
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RECENT HISTORY OF WATER AND SALINIT
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Figure 1. Hydrological cross-sectio
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Depth (m) 316 315 314 313 312 311 M
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FURTHER INVESTIGATIONS AND MANAGEME
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Dealing with salinity in Wheatbelt Valleys - Department of Water

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