Evaluating the effect of different water demand scenarios on downstream water availability in Thuli river basin, Zimbabwe.

Abstract

Thuli river basin is situated in a semi-arid area, where surface water resource availability is a constraint due to low rainfall received in the area. The river basin is more developed in its upper than lower reaches. There is intensified use of blue water in the upper catchment and demand from powerful sectors such as urban is increasing. This study is being carried out to evaluate the effects of upstream water demand scenarios on downstream users in the Thuli river basin in order to improve on the management of the water resources. To understand and manage such imbalances between upstream and downstream water users, this research applied a spreadsheet computer model as a tool to simulate the effects of different water demand scenarios on downstream water availability in Thuli river basin. Focus group discussions were done with major water demand nodes to establish the monthly demands. Historical hydrological and meteorological data were corrected and used as input to the model. Meetings were conducted with officials from different sectors involved in water utilization and development. In this research, the impacts of different water demand scenarios on the downstream water availability were evaluated. The water demand scenarios used were categorized in four sections, based on government recommendations and plans on water resources development, technology improvement, drought risk mitigation and factors affecting water demand in urban areas. The results of the simulations of water demand scenarios were analyzed and knowledge was generated to contribute to the management of the water resource in Thuli river basin.