Dealing with salinity in Wheatbelt Valleys - Department of Water

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et al.1995, Chapter 4). The big picture however is one in which solutes and suspended silts and clays move faster and further down slope than the rolling and saltating sands. The general model of soil formation on hillslopes thus involves epimorphism of bed rock to saprolite and saprolite to soil with the principal motivators of the latter being biochemical change in the rhizosphere, mining by fauna, mainly in the topsoil, clay eluviation (Chittlebrough 1992) and differential downslope movement of bioturbated topsoil by rain wash. One outcome is a mobile, light textured, biomantle often expressing as a texture contrast soil. Reduced mobility on lower slopes, where the slope starts to wane, results in congestion and hence thickening of the mobile sandy layer. As deposition progresses, underlying soil starts to fall outside the influence of bioturbation, and clays coming in from upslope start to accumulate. In other words, there comes a point at which topsoil differentiation over-rides faunal mixing. Further down slope, old differentiation becomes buried by new differentiation and at this point we start to get a historical record of soil formation reflecting changes in surface hydrology, climate and vegetation (Figure 12). One thus encounters more and more colluvial/pedogenetic – 17 – Commander, Schoknecht, Verboom and Caccetta history in vertical sections as one progresses down waning cross valley slopes towards the oldest buried river channels. The situation in flat-floored valleys is somewhat different. Their catchments are large enough to sustain planating flows that are tempered by the very low down valley gradients mentioned above. Indeed, the erosive power of contemporaneous flows may be so subtle and ineffective that their impact is more pedogenetic than topographic. In these situations, clay winnowing and sand saltation generates ‘rivers’ of deep sandy duplexes with shallow sandy and loamy duplexes on the ‘interfluves’. HYDRO-AEOLIAN ACTIVITY Hydro-aeolian activity is important whenever there is a plentiful supply of loose fine material and little vegetation. The latter condition was particularly evident during last episode of aridity (25000 – 13000 B.P.) (Bowler 1976) and is caused by rising and lateral flows of salt in lower parts of the landscape. The obvious expression of hydro-aeolian activity is the playa lake systems and associated depressions. Figure 12: This profile, on a lower mid slope west of the town of Narrogin, records at least two cycles of soil formation in which iron and clay differentiation has been active with the most recent (uppermost) episode apparently contemporaneous. The sandy A-horizons appear intact and remain so 50 m down slope in two other exposures. They have similar sequences: red crystalline ferric oxides, principally hematite, can be seen along the margins of vertical root channels in horizon 1B, with their older, yellow hydrated counterparts in the buried 2B. Root channel precipitation does not extend into the sandy horizons below both B-horizons and so the contemporary process is limited to uppermost B-horizon. Contemporary precipitation tends to be confirmed by the observation of haematitic precipitates surrounding living Banksia roots.
Commander, Schoknecht, Verboom and Caccetta Here, ground level winds entrained sand size particles (2.0 - 0.05 mm in diameter) which moved by rolling and saltation while finer particles moved in suspension after dislodgment by the saltating particles. The particles may themselves be quartz grains or aggregates of minerals detached from mud curls and salt/mud efflorescences. Lunettes on the south eastern side of playas betray old north westerly winds. Lunette composition depends on provenance which in turn depends on hydrologic regimes. In other words, playas producing loose quartz sand generate sandy lunettes while those producing pelleted clayey aggregates generate clayey lunettes. Finer particles blow and saltate out greater distances forming discontinuous sheets of parna (locally referred to as morrel soils) which may over print hillslope soils. NEW GEOPHYSICAL PERSPECTIVES At the end of the day, the above described pedogenetic processes have to be consistent with newly acquired data. Airborne geophysical mapping provides such data, offering pedologists a new and penetrating perspective of soil landscapes. Below we first briefly describe these techniques and then use them to examine the relationship between radiometric and elevation data and the occurrence of salts and soils in parts of the Avon, Lake Toolibin and Elashgin catchments. DIGITAL ELEVATION MODELS (DEM) A DEM is a digital representation of the earths’ surface where, with the use of a computer, the elevation of a location on the ground (measured in Eastings and Northings, say) can easily be obtained by a simple click of a mouse button. Figure 13: An example of landscape visualisation using Landsat TM Figure 13 is an example of landscape visualisation using Landsat TM satellite information (visible and infrared) and digital elevation models. In this perspective view, the town of Merredin appears in the top left of the image as a blue/green colour. Paddocks with vigorous crop and pasture cover appear red, and saline areas in the lower left appear as hews of blue and green. Terrain has been exaggerated. From the figure we observe that the – 18 – salinity is largely confined to the lower parts of the landscape. DEMs may be combined with data such as Landsat TM, or aerial photography in digital form, to provide a powerful visualisation tool, an example of which is given in Figure 13. Further, computer algorithms and simulations may be applied to DEMs to produce estimates of land surface characteristics such as
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 29: 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
Page 57 and 58: George and Coleman for example in t
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
Page 67 and 68: George and Coleman this volume). In
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
Page 77 and 78: Effect of clearing on runoff The ot
Page 79 and 80: 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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