SPATIO-TEMPORAL TRENDS OF HYDRO-CLIMATIC VARIABLES AND POTENTIAL WATER DEFICIT IN THE BAGEL ZUNGUR WATERSHED, NORTH-CENTRAL NIGERIA (1981–2020)

Understanding long-term hydro-climatic variability is vital for sustainable water resource management, especially in watersheds targeted for infrastructural development. This study examined the spatio-temporal trends and patterns of key hydro-climatic variables—rainfall, relative humidity, temperature, and potential water deficit (PWD)—in the Bagel Zungur Watershed, North-Central Nigeria, over a 40-year period (1981–2020). These parameters were selected due to the proposed dam project within the watershed. Monthly and annual climatic data were sourced from NASA POWER/CERES/MERRA-2 and Climate Engine datasets. Linear regression and time-series analyses were employed to assess long-term trends, variability, and deviations from mean conditions. The results indicate a general decline in rainfall of 10.44 mm (16.57%) accompanied by strong inter-annual variability range of 1,350.59 mm. Decadal pattern revealed steady decline from 1991-2000 (1177 mm), 2001-2010 (480.08 mm), and 2011-2020 (546.87 mm) with a longtime annual average of 888 mm respectively. Relative humidity also showed a decreasing trend (-0.13%) and a long-term average of 53%, while temperature exhibited a significant increase (0.04%) with annual mean temperature of 24°C, reflecting progressive warming across the watershed. Potential water deficit remained consistently high (-848.68), with peak deficits occurring between 2001 and 2010 (-1668.7), suggesting persistent hydrological stress despite a slight post-2011 improvement. Overall, the study provides a critical baseline for dam planning, water resource management, and climate adaptation in the watershed.