ASSESSMENT OF RAINWATER HARVESTING POTENTIAL AND APPROPRIATE TECHNOLOGIES IN ABUJA, NIGERIA

Abstract

Water scarcity is vastly becoming a serious environmental problem in the world and in Nigeria, it is increasingly becoming severe and frequent. This is especially so in Abuja where; water scarcity is a major contributor to environmental problems. The rate of water consumption, urbanization and industrialization has exceeded the rate at which the available water supplies are replenished. Rainwater harvesting is one of the means with which water scarcity in Abuja State could be mitigated. The current research was therefore aimed at assessing and mapping Rainwater harvesting potential in Abuja, appropriate technologies as well as evaluating the effect of rapid urbanisation and climate change on that potential. The study applied Geographical Information System (GIS) integrated with Multi-criteria Decision Analysis (MCDA) to assess the potential for rooftop, surface and in-situ Rainwater Harvesting (RWH). Some of the factors considered during this analysis were annual rainfall, land use/land cover, population, and land slope and soil type. The spatial multi-criteria evaluation was used to classify and rank the suitable locations for rainwater harvesting while the Analytical Hierarchy Process (AHP) method was used to compute the priority weight of each criterion. Using AHP, the percentage weights derived for each criterion considered for in-situ rainwater harvesting were rainfall 24.2%, slope 24.8%, soil 20.8% and land use/land cover 30.2%. Potential maps of different RWH systems and technologies for Abuja were generated. The total quantity of harvestable rainwater was estimated to be 5.6 billion m3 by in-situ rainwater harvesting at minimum rainfall. Some of the appropriate technologies found are megrims, trapezoidal bunds, bench terraces and xv igloo pits. The effect of urbanization leading to the lateral spread of built-up areas and climate change on the potential of rooftop and surface rainwater harvesting reflected an increase of about 120% and 18.2% respectively in the quantity of rainwater harvestable at minimum rainfall between the years 2016 and 2046. The result showed that Abuja has an excellent potential for rooftop, surface and in-situ RWH and this potential will most likely increase over time. This quantity of harvestable rainwater can be used as an additional source of water which will minimize the problem of water scarcity in the state. It is therefore recommended that RWH be adopted in Abuja. Keywords: Abuja, Analytical Hierarchy Process, Geographical Information System, Rainwater Harvesting Potential, Water Scarcity.