Changes in water balance components with pasture management in south-eastern Australia

Abstract

A method for evaluating infiltration and evapotranspiration for experimental catchments was applied to a series of four-acre catchments near Bacchus Marsh, Victoria. Differences in run-off between two levels of native pasture production were shown to be the direct result of changes in infiltration. On the more productive pasture containing perennial grasses, the infiltration rate was higher because of a larger capacity for moisture storage in the topsoil, and higher rates of water movement in the subsoil. The conversion of both levels of native pasture to annual improved pasture was associated with a reduction in run-off in each case, due to increased evapotranspiration during periods when soil moisture conditions are assumed to be non-limiting (topsoil moisture potential less than pF 3.5). The larger deficits developed in the soil moisture store led to increased infiltration and reduced run-off from rainfall events. The use of these findings to predict run-off, and their implications for catchment management, are discussed.