Ecohydrological Changes in the Murray-Darling Basin. III. A Simulation of Regional Hydrological Changes

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Journal of Applied Ecology

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1. Regional scale changes to the hydrological cycle of the M urray-Darling Basin (MDB) in Australia have occurred as a result of European settlem ent 200 years ago. Replacem ent of deep-rooted perennial plants (trees) by shallower rooting plants (pastures and cropping) is of particular significance in altering water-tables and causing waterlogging and secondary salinization.

2. The purpose was to locate the areas at risk of waterlogging and salinization as a result of tree clearing. To achieve this, present-day evaporation (ET) from 0*8% of the MDB (7750 km^) is com pared with ET from a reconstruction of the pre- European condition.

3. The spatial geographical database for the 155 x 50 km study area consisted of vegetation, soils, climate and topographic information at 1-6 x 1-6 km cell resolution (3072 individual cells for each data layer).

4. Leaf area index (LAI) was used to define the am ount of photosynthesizing and transpiring tissue. Present-day LA I was estim ated for each cell using the Normalized Difference Vegetation Index calculated from NO AA-9 Advanced Very High Resolution Radiom eter data. Pre-European LA I was obtained using the assumption that an equilibrium exists between LAI and clim ate—soil conditions. Daily climate was interpolated across the study area from Australian B ureau of Meteorology weather stations using topographic information and a microclimate simulator (MTCLIM).

5. A water balance model previously described (Part II) was used to calculate past and present-day ET for each cell assuming that only the tree vegetation had changed. The simulation was confined to a 30-day period in autum n when a uniform senescent ground layer occurs. Maps of water use by trees for pre- European and present-day vegetation were produced.

6. Differences in ET between pre-European and present-day vegetation were displayed spatially across the study area. These areas are interpreted as representing areas at risk from waterlogging and salinization.


remote sensing, salinization, tree clearance, water balance model, waterlogging


© 1993 Wiley

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