Impacts of afforestation on low flows: Paired catchment data revisited

Abstract

Disruption of the hydrological regime caused by afforestation is well documented. Several sets of experimental catchments were set up in South Africa between 1935 and 1980 specifically to quantify such impacts. Data emanating from these experimental catchments have been used in several analyses, and have progressively directed the regulation of commercial forestry and its associated hydrological impacts in this country. Subsequent modelling efforts have sought to introduce improved accuracy by accounting for catchment- and species-specific variations in impacts. However, conventionally used one dimensional hydrological model which models soil moisture to limited depths have been shown to reproduce periods of low flow with limited accuracy. This is a considerable limitation since the evaluation of land use impacts on periods of low flow is particularly important in riverine and water resources management. This paper presents a re-analysis of the data sets of several of the paired catchments, with focus on the low flow periods. Hydrological dynamics revealed by this analysis are to be used in future, improved modelling exercises