Impact of Climate Change on Hydropower Generation: Case of Shiroro Dam, Nigeria

Abstract

This study assessed the climate change impacts to streamflow and energy production in Shiroro Hydro power dam, located in a Guinean savannah zone in Niger State, Nigeria. Rainfall (1981-2015), streamflow (1990-2014), temperature (minimum and maximum) (1981-2015) data were collected from Nigeria Meteorological Agency (Nimet) and homogenisation test performed on the data using RHtestsV4. The trend in the data was evaluated using the Mann-Kendall and Sen’s slope techniques. Assessment of streamflow was done by utilising the Soil and Water Assessment Tool (SWAT). Remote Sensing datasets such as Digital Elevetion Model, FAO soil map and Moderate Resolution Imaging Spectroradiometer (MODIS) land cover were utilised in ArcSWAT to set up the watershed. Climate Forecast System Reanalysis (CFSR) was downloaded and served as the climate datasets for forcing the SWAT model. Streamflow data obtained were divided into two with the first part used for calibration and the other part for validation of the watershed model. Downscaled NCC-NorESM1-M with WRF model output (precipitation, maximum and minimum temperature) under RCP 4.5 and 8.5 scenarios were extracted for the study area and streamflow simulated for the projected data in ArcSWAT. A stochastic dynamic model was employed to assess climate change impact on hydropower generation using the simulated output from the SWAT model. The results from the trend test showed existence of positive trend in both precipitation and temperature (average temperature) for Kaduna and Zaria whilst Minna and Jos indicate presence of negative trend in average temperature with Jos precipitation showing no significant trend and Minna precipitation series revealing a positive and significant trend. The calibration results of streamflow were unsatisfactory for R2 = 0.51 and NSE=0.43 whilst PBIAS = -2 was very good. The uncertainty criteria of the model p-factor was 0.79 and r-factor 1.27 which were within the recommended range. The R2= 0.79 and NSE= 0.77 and PBIAS = 15 values were good during the validation period with p-factor = 0.77 and r-factor = 0.77. Streamflow increased significantly from the baseline period (1990-2014) when compared with the projected future scenarios for both RCP 4.5 ad 8.5. Generally, energy production were observed to increase alongside revenue generation in the future but reliability of the plant was below the acceptable 0.75 reliability.