Estimating episodic recharge under different crop/pasture rotations in theMallee region. Part 1. Experiments and model calibration

Changes in land use in the Mallee region of southeastern Australia have led to increased groundwater recharge and salinisation. This study was conduct ed to determine the impact of different agronomic practices on recharge con trol, in particular episodic recharge. During the period 1991-1995, two fie ld experiments were carried out at Hillston (New South Wales) and Wallpeup (Victoria) where soil hydraulic properties, soil-moisture content, and leaf area index were measured. Various crop and pasture rotations were consider ed involving fallow, field pea (Piscum salivum L cv Dunndale), Indian musta rd (Brassica juncca cv F2 cross), wheat (Triticum aestivum cv Janz Meering) , oats (Avena sateva L. cv Coolabah), lucerne (Medicago sativa L. cv. Arora ) and medic pastures (Medicago truncatula cv Parriagio, Sephi and Hykon). D ata obtained from these experiments were used to calibrate and test a bioph ysically based model WAVES. With minimum calibration, the simulated soil-mo isture content and leaf area index are in good agreement with field observa tions. The parameter values are within a physically reasonable range. The s uccess of the model in simulating soil-moisture dynamics and plant growth w as due to the accurate representation of the soil and canopy processes. WAV ES combined with field measurements provides a powerful tool for estimating the impacts of land-management options on water balance. (C) 1999 Elsevier Science B.V. All rights reserved.