Deep infiltration - Significant or not

Abstract

For those involved with evaluating the effects on the water balance of changes in land use, it is always interesting and pleasing to see a report on a study involving paired catchments. One such report was presented by Prebble and Stirk (1988). From their study, Prebble and Stirk concluded that the killing of trees and establishment of improved pasture in an open grassy woodland did not affect evapotranspiration. While this result was not quite what they expected, they thought it could be explained by the fact that the killing of the trees resulted in an increase in wind run and in radiation to the grass. This in turn would have increased evapotranspiration from the grass, which would have compensated for the reduction in interception and evapotranspiration by the trees. This explanation, to some extent, ignores the observed increase in average soil water storage following the death of the trees. Perhaps, then, the answer to this water balance problem lies not in the evapotranspiration term, but in the increased soil water storage and associated increased deep drainage.