Abstract
The clearing of native vegetation and establishment of agricultural plants on a small catchment in southwest Western Australia resulted in a large streamflow increase (approximately 30% rainfall/yr). This increase was brought about by a decrease in transpiration and interception loss. Streamflow increased markedly in the first year after clearing (approximately 10% rainfall) and continued to increase at a slower rate for a further five years, when a new streamflow equilibrium was reached. Explanations of the time trend of streamflow increase were sought in terms of streamflow generation mechanisms. The initial increase in streamflow was attributed to the impact of the immediate decrease in interception loss (approximately 13% of rainfall). The subsequent linear increase in streamflow was closely correlated with the expansion of the groundwater discharge area, and the cessation of streamflow increase was considered to result from the attainment of a new groundwater recharge-discharge equilibrium. Evidence from other catchments which have undergone forest reduction show that the permanent groundwater system is instrumental in controlling the streamflow response following forest reduction.
