A flow-filter model for simulating the conservation of limited resources in spatially heterogeneous, semi-arid landscapes

As in arid lands of the world, many semi-arid landscapes in Australia have plant and animal growth and reproduction, hence survival, severely limited by available water. For example, Acacia anuera (mulga) grove-intergrove landscapes are source-sink systems where water flows from low ridges and stony slopes (inter-groves) into flat areas (groves). Water can be lost from these systems, to lakes and rivers. This occurs if the water retention (filtering and storage) capacity of the sinks is too low (perhaps due to landscape degradation) or if the total area of sink is too small. A flow-filter landscape model was developed to determine the area of sink (relative to the total area) that will maximize resource (water) conservation and plant production under conditions of low rainfall. The model was also used to examine the effect of having landscape resource sinks with low and high filtering capacities. Simulation results indicate that when rainfall is low (160 mm) the area of sink needed to conserve all available water within the landscape was 40 per cent of the total landscape area when sinks had high resource-filtering capacities; this area increased to 60 per cent when sinks had a low filtering capacity as the case with landscape degradation. The flow-filter landscape model can provide land managers with guidelines on rehabilitating degraded landscapes by reconstruction of sink areas. To conserve the limited amounts of rainfall within a semi-arid landscape a minimal area of sink has to be reconstructed; the flow-filter model estimates this minimal area, thus reducing rehabilitation costs.