Assessment of Climate Variability Impacts on Reservoir Storage and Hydropower Generation at Kainji Dam, Niger State

Kainji Dam in Niger State is Nigeria's largest hydroelectric facility, and its reservoir storage and power generation capacity are inherently sensitive to inter-annual and decadal climate variability driving inflows from the Niger River upper catchment. This study assesses the impacts of observed climate variability on reservoir storage dynamics and hydropower generation at Kainji Dam using a combination of meteorological, hydrological, and reservoir operations data for the period 2005 to 2022. Monthly inflow records to Kainji reservoir were obtained from the Kainji Lake National Park and correlated with upstream rainfall anomalies from NiMet stations in Niger State and Niger Republic using lag correlation analysis. A reservoir operations model simulating storage fluctuations and power generation under observed inflow sequences was developed and validated against historical generation records from the Niger Delta Power Holding Company. Results reveal that above-normal upstream rainfall anomalies, associated with La Nina events, produce mean reservoir storage increases of 22 percent above baseline, translating to measurable increases in annual hydropower output. Conversely, El Nino-related rainfall deficits have been associated with reservoir drawdown events in 2009, 2015, and 2018, each resulting in generation curtailments exceeding 15 percent of annual installed capacity output. The study develops a statistical prediction model for Kainji reservoir inflows from ENSO state and upstream rainfall anomalies, showing useful skill at three-month lead time for operational water management planning. Keywords: hydropower, Kainji Dam, climate variability, ENSO, reservoir storage.