Site selection for rainwater harvesting : a case of KwaZulu-Natal, South Africa

Abstract

The rapid growth of the world’s population has placed an increased strain on water resources globally, particularly in sub-Saharan Africa, where communities rely on rainfall for their day to day activities. Water scarcity in KwaZulu-Natal, South Africa, is high because of unevenly distributed rainfall and limited water resources. There is a need for suitable site selection for rainwater harvesting structures in KwaZulu-Natal, which has the potential to address shortage of water currently experienced in the province. Access to adequate water supply and sanitation is crucial for poverty alleviation and addressing the problems faced by vulnerable groups, such as those affected by HIV/AIDS and other diseases. Rainwater collection is a procedure in which rainwater is gathered and stored for a multitude of objectives. This practice encompasses the capture of precipitation either at its point of descent or via the accumulation of runoff from various surfaces such as rooftops, roadways, or landmasses. By facilitating the optimal utilization of rainfall, rainwater collection endorses a diminished reliance on conventional water sources and the minimization of water dissipation. It contributes to the conservation of water resources and ensures their sustainable management. This study aimed to select suitable sites for rainwater harvesting using geographic information systems (GIS) and multi-criteria decision analysis (MCDA) techniques in the province of KwaZulu-Natal, South Africa. Geospatial data on precipitation, soil, slope, runoff curve number and land use were combined to develop a multi-criteria ranking system. Using the Analytical Hierarchical Process (AHP), weights were assigned with rainfall assigned (17), soil texture (39.1), slope (11.3), land cover (5.6) and Runoff curve number (27). The selection of these specific factors for this study areas was based on a review of literature. The study identified moderately to highly suitable sites for rainwater harvesting structures, covering 38% of the study area. Approximately 10% of the study area was considered to be less suitable for rainwater harvesting (RWH). The research findings could facilitate the wider adoption of rainwater harvesting in KwaZulu-Natal to meet irrigation demands and promote sustainable water resource management. The developed methodology can be implemented and adopted by any city or country. This study could be expanded by collecting and analysing various parameters (such as distance to roads, groundwater discharge, and geology and lineaments density, expertise and decision-makers preference value for pairwise matrix comparison). The development of a graphical user interface and improved approach in MCDA in relation to relative weight calculation while integrating the water balance model may also be considered for future research.