Dealing with salinity in Wheatbelt Valleys - Department of Water

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Commander, Schoknecht, Verboom and Caccetta Figure 3: Solid geology of the Agricultural Area (after Myers and Hocking 1998) Finkl & Fairbridge (1979) have suggested that peneplanation of the Yilgarn Craton was completed in the Proterozoic, and that denudation rates were minimal ever since. They argued for a western source for the Permian-Cretaceous Perth Basin sediments (Fairbridge & Finkl, 1978), though this was challenged by van de Graaff (1981) who argued for removal of some 500 m of rock from the Yilgarn Craton since the Jurassic. However, it has recently been found that the Archaean provides only a minor source of detrital zircons to Quaternary mineral sand deposits in the Perth Basin (Sircombe & Freeman 1999). This strongly implies a western source for Perth Basin sediments from Proterozoic rocks, and supports the suggestion of minimal erosion of the Yilgarn Craton at least since the Jurassic/Cretaceous. Thus the landscape appears to have been moderately stable since the age of the dinosaurs. Most authors now agree that peneplanation was complete by the end of the Creatceous. Twidale – 5 – (1994) postulates that the ‘new plateau’ of Jutson (1934) in the eastern Yilgarn must also be of Eocene age, on the basis of the Eocene sediments there, and that the ‘older plateau’ is even older. Drainage The oldest drainage systems now preserved are likely to be in the zone of ancient drainage (Figure 1) containing the Pingrup, Lockhart and Camm valleys, between the median and the central watersheds, recently recognised by Beard (1998; 1999). The region may have been traversed by palaeoriver systems draining Antarctica when the continents were joined (Figure 4), and Beard (1999) has suggested that these rivers may have originally drained southwards (Figure 5), following the opening of a seaway between Australia and Antarctica in the Jurassic 150 million years ago (Table 2). It may be significant that these valleys follow the NNW structural trend in the basement rocks.
Commander, Schoknecht, Verboom and Caccetta These palaeodrainages are analogous with the Eastern Goldfields where an integrated palaeodrainage system, at least in existence by the start of the Middle Eocene (50 My) has palaeochannels infilled with mid to late Eocene sediments (Kern & Commander 1993; Clarke, 1994b). These palaeodrainages, however, cross the geological structure and direction appears determined by drainage to the Eucla Basin. No age dating has apparently been carried out on the palaeochannel sediments in the zone of ancient drainage (Yilgarn System of Beard 1999), though they have been correlated with the Eocene Bremer Basin sediments (Dodson 1999). Westward draining Eocene sediment-filled valleys (Figure 5) have been identified in the current Blackwood and Beaufort catchment (Waterhouse et al. 1995) and in the North Stirlings (Appleyard 1994), Mobrup catchment (Hundi et al. 2000) and at Wilgarup near Manjimup (Thorpe 1994). However, Figure 4: Reconstruction of Gondwana (GSWA 1990) – 6 – farther north, Eocene sediments have been identified only in dissected uplands (eg Westdale, Brookton), so the drainage pattern is currently unknown. The Perth Canyon, infilled onshore with Palaeocene (65- 55 My) sediments (Davidson 1995), and correlated with the Avon palaeochannel (Salama 1997) indicates the presence of a large westward flowing river system, but no sediments of that age are preserved on the Darling Plateau. The existence of Eocene sediments in palaeochannels confirms a minimum age for these palaeodrainages of about 45 My, Early Cretaceous sediments preserved only in the Collie basin (Nakina Formation) could have been much more extensive, but cannot be linked with current drainage systems. Twidale (1994) postulated a Gondwana landscape of low relief, with low domes rising from duricrusted plains in the southwest Yilgarn Craton, which could be similar to other pre-Cretaceous land surfaces currently being exhumed elsewhere in Gondwana.
Page 1 and 2: Foreword Dealing with Salinity in W
Page 3 and 4: 1Day one: Monday 30th July. Field t
Page 5 and 6: Papers Dealing with Salinity in Whe
Page 7 and 8: Ali and Coles biggest challenges fa
Page 9 and 10: Ali and Coles erosion, maintenance
Page 11 and 12: Ali and Coles expected under these
Page 13 and 14: Ali and Coles Coles, N.A. & Ali, M.
Page 15 and 16: Commander, Schoknecht, Verboom and
Page 17: 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
Page 55 and 56: George and Coleman surface, the vas
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Page 59 and 60: George and Coleman current trends c
Page 61 and 62: George and Coleman While not as div
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Page 65 and 66: George and Coleman advantages of so
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George and Coleman Venture Economy
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George and Coleman Lawrence, C. (19
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Hatton and Ruprecht WATCHING THE RI
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Since the mid 1970s annual rainfall
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Effect of clearing on runoff The ot
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Salinity Monthly streamflow (ML) 10
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The ratio of the salt outputs to in
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- 11 - Hatton and Ruprecht Table 4:
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THE FUTURE In looking at the future
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McFarlane, D.J., George, R.J. & Far
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Keighery, Halse and McKenzie Terres
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Keighery, Halse and McKenzie Wetlan
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Keighery, Halse and McKenzie specie
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Keighery, Halse and McKenzie enviro
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Lloyd number of legal cases pending
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Lloyd 0 -500 -1000 -1500 -2000 -250
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Lloyd Table 3. Sheep grazing days i
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Lloyd Hectares project to provide w
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INTRODUCTION The Lake Chinocup Catc
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agriculture) in various stages, the
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- 3,477 ha of remnant vegetation or
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Scientists talk of up to 30% of the
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6320000 6300000 6280000 6260000 624
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Although the waterlogged area under
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eliminates drainage through the nex
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REFERENCES Dawes, W.R., Stauffacher
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Pannell ECONOMICS, SOCIETY AND ENVI
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Pannell • the area of land protec
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Pannell Proposals to construct majo
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Pannell been conducted for the Cent
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Pannell investments in long-term la
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Pannell Pannell, D.J. (2001). Dryla
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Porter, Bartle and Cooper Table 1:
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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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