Farm Dams in Southern Africa: Balancing Environmental and Socio-Economic Sustainability

Abstract

The proliferation and extent of small dams is a significant issue for water resources management. South Africa has an extensive spatial database of farm dams; however, uncertainties remain when estimating the water volume held, although satellite-based techniques offer some means of measurement. This chapter compares various datasets on the occurrence of farm dams in southern Africa and summarises the research on their impacts. Correlations between high-density of small dams and the decline of macroinvertebrate communities, resulting from compromised water quality and low flows, have been established in South Africa. Despite this, the assessment of the cumulative impact of farm dams on riverine ecosystems proves complex due to various uncertainties. The degree of impact varies by dam type, with off-channel dams exhibiting a lower influence on connectivity and sediment dynamics. Efforts to manage and mitigate the effects of small dams is being addressed through a variety of integrated approaches, including: a spatial cost-benefit framework, a model that incorporates different value systems with equitable allocation criteria, and agent-based modelling. The viability of these techniques is dependent upon securing agreement among stakeholders. The chapter concludes with some recommendations for the ways forward.