Evaluation of the Impact of Climate Change on Water Resources in Usutu River Basin, Swaziland

Abstract

The greenhouse effect is expected to cause high temperature increase globally and this will lead to an increase in precipitation in some regions while other regions will experience reduced precipitation. Therefore, countries are engaged in the exercise of evaluating the impact of expected climate change on water resources using General Circulation Models (GCM) and hydrologic models. The WatBall model has been found appropriate for the evaluation of the impact of climate on water resources. The Usutu catchment was selected for the evaluation of the impact of climate change on water resources because it covers two thirds of the country and traverses the four physiographic regions. The results of GCM models (precipitation, temperature and thus potential evapotranspiration) have been used as input to the calibrated WatBall model to forecast stream flow for Usutu catchment for the wet, dry and average year for year 2075. A comparison between observed and simulated stream flow without taking into consideration of population increase and expanded agricultural activities reveals that all the GCM models are simulating low flows from June to September for the wet years and from May to September for the dry and normal years. What can be concluded here is that, stream flows will be low during the winter months. Therefore, optimal water resources management will be crucial. Adaptation options have been suggested and range from modification of the existing infrastructure to water demand management.

UNISWA Research Journal of Agriculture, Science and Technology Vol. 4 (2) 2000: pp 135-146