Preliminary empirical models to predict reductions in total and low flows resulting from afforestation

Abstract

Mathematical models to predict runoff reductions due to afforestation are presented. The models are intended to aid decision-makers and planners who need to evaluate the water requirements of competing land uses at a district or regional scale. Five afforestation catchment experiments were analysed by the paired catchment method to determine the reductions in both total (annual) and low flows. The percentage reduction in flow after afforestation with both eucalypts and pines was determined for each post-treatment year relative to the expected flow based on a calibration relationship with an untreated (control) catchment. The authors fitted curves to these data points to predict the effects of afforestation under optimal and sub-optimal growing conditions. Eucalypt plantations were found to deplete both total and low flows sooner and in larger quantities than pine stands.