ABSTRACT
Climatic parameters are exposed to variation due to the atmospheric concentration of greenhouse gases. Hence, it is essential to assess the water availability and demand under the climate variation in Goronyo Reservoir, Sokoto State Nigeria. since the supply of water is one of the significant tasks in water resources management. In this study, estimation of available water, demand, and unmet demand was simulated using Water Evaluation and Planning (WEAP) Software with the opinion of assessing the availability of water for its uses under climate change, The Reservoir is situated in Goronyo Local Government Area, Sokoto State, Northwest Nigeria. The study uses Water Evaluation and Planning (WEAP model) softwareto assess the influences of climate variability on the water availability of the area. This model allows simulation and analysis of various scenarios and water allocations. The water availability, Demand, Supplies, and Unmet were modeled with climatic data and water use rate. The model was satisfactorily calibrated and validated. Simulations were proposed for various climatic situations considering global climate change model (GCM) predictions and the linear trend of the data. Nine (9) selected climate change scenarios of temperature increases (i.e. 0, +0.4, +0.8, +1.2 oC) combined with an increase or decrease in rainfall (0, -10%, +10%) were applied for the study area in the WEAP model software for simulation. The model was used to analyze the linkage between water availability and demand for domestic and irrigation uses. This was projected to the future to analyze what would happen in years to come up to 2070. The demand and unmet were obtained as the output of the model. Results showed that the mean average volume of 737.9 million cubic meters (MCM), the maximum average volume of 824.3 MCM mainly in the wet period ranges from May - October, and the minimum mean average volume of 546.6 MCM mostly in a dried month i.e. April available in the reservoir. The annual total demand for various uses from 2018 to 2070 was obtained to be 7069.4 MCMand the annual average of 133.4 MCM. Meanwhile, the unmet demand was with annual total ranges from 1157.5 MCM to 1199.7 MCM and an annual average of 21.84 MCM to 22.64 MCM. The highest unmet was recorded under Scenario 9 with a 1.2 oC increase in temperature and a10% decrease in precipitation. In Conclusion, it was found that the demand in the area is 6 times higher in years to come i.e. 50 years from now and the deficit is 61% increased. It is recommended that the irrigation system (furrow irrigation system)should be improved to minimized water demand and also extraction from other means such as groundwater could relieve the stress on the available source, the reused of wastewater for other domestic uses such as the washing of lawn and watering of gardening will also help a lot in utilizing limited available resources.