Predicting land use impacts on regional scale groundwater recharge and discharge

The paper presents the development and evaluation of methods that estimate recharge and discharge, water flow, and salt fluxes in rivers. The methods in combination provide an inferential framework to predict dryland salinity and the selection of the appropriate management scenarios. Hydrogeomorphic Analysis of Regional Spatial Data (HARSD) was used for delineating hydroge ologically homogenous units, and to translate limited hydrological data int o hydraulic head surfaces and ultimately a steady state flow net representi ng recharge-discharge relationships. A complex, physically based water, ene rgy, and carbon model (WAVES) was developed and tested to provide recharge estimates required for the now net simulations. Remote sensing imagery and analysis techniques involving airborne, advanced very high resolution refle ctance (AVHRR) and LANDSAT-Thematic Mapper (TM) data were used to infer the temporal and spatial patterns of leaf area index (LAI) and land-cover type . The techniques were applied in 22 subcatchments in the Loddon and Campasp e and for the two major catchments. Modeled recharge was consistent with lo cal estimates based on inverse methods and with subcatchment-scale estimate s based on stream salt leeds under a steady-state assumption. The calibrate d flow nets for each of the subcatchment have been used to test the sensiti vity of this system to changes in recharge resulting from land use change. It is shown, for example, that the Upper Campaspe subcatchment would requir e the reforestation of key recharge areas totaling 45% of the subcatchment to reduce salt loads from approximately 25 000 Mg yr(-1) down to 18 000 Mg yr(-1) under steady state assumption.