Assessing the surface rainwater harvesting potential for Abuja, Nigeria: a short-term projection

This study aimed at assessing the surface rainwater harvesting potential in Abuja as a means of mitigating the problem of water scarcity. Surface rainwater harvesting potential for the year 2046 was assessed using Geographical Information System (GIS) and Spatial Multi-criteria Evaluation (MCE). The criteria considered were annual rainfall, land use/land cover (LULC), slope and soil. The spatial MCE was used to estimate the extent of surface rainwater harvesting and rank the potential. Analytical Hierarchy Process (AHP) was employed to determine the priority weights of the criteria which gave; rainfall 55.9%, LULC 26.3%, slope 12.2% and soil 5.7%. A potential map for surface rainwater harvesting was produced showing moderate, good and excellent with the percentages of Abuja 10.7, 34.4 and 54.9% respectively. After considering an increased rainfall from (1170 mm-1470 mm) in 2016 to (1230 mm-1910 mm) in 2046, expansion in built-up areas, bare surfaces due to urbanisation and population growth, the result showed that Abuja will have a minimum of 5.8 billion litres of water harvestable from rainfall per year which is about 14.8% increase compared to the estimated harvestable quantity for 2016. Therefore, the potential for surface rainwater harvesting in 2046 is significantly greater than it was in 2016.