Mapping suitable sites for water storage structure in the Sokoto-Rima basin of northwest Nigeria

Abstract

The persistent phenomenon of climate change has resulted in increased dryness and incidence of intermittent drought event as well as advancement of Sahara desert into the Sudano-Sahelian region of northern Nigeria. Part of the effect of this climate variability is increased intensity of rainfall albeit reduction in total amount rainfall, consequently producing high runoff, low infiltration and eventually creating the problem of water scarcity, which has adversely affected crop production, culminating in crop failures and pest infestation in some cases. Adaptation scheme involving rainwater management such as capturing and storing water for future use represents the best possible alternative to the current situation and possibly future scenario.In this study, sites suitable for location of water storage structures were delineated in the Sokoto-Rima basin by combining eight factors considered important in suitability analysis for water storage structures. The factors considered are land use/cover, soil, geology, slope, drainage density, lineament density, distance to drainage and precipitation. The factors were classified with each class assigned preference value based on insights from previous studies and knowledge of the study area. The factors were integrated through weighted overlay analysis using factors’ weights computed from Analytical Hierarchy Process. The result of the suitability analysis showed that 3% (131.89 km2) area of Sokoto-Rima basin is considered to be highly suitable, 9% (486.19 km2) of the basin area is moderately suitable, 11% (596.05 km2) of the basin area have low stability for siting water storage structures while 77% (3967.62 km2) of the basin is not suitable. Further combination of suitability layer, drainage network, cross-section graph generated from digital elevation model and triangulated Irregular Network (TIN) enable selection of six potential sites for which parameters such as base elevation, outlet elevation, surface area, storage capacity and flood extent were computed.