Trend analysis of observed precipitation, temperature, and streamflow for Hadejia-Nguru wetlands catchment, Nigeria

This study investigated trends in hydro-climate data (precipitation, maximum/minimum temperatures, and streamflow) for the period 1980–2016 around a semi-arid Hadejia-Nguru wetlands (HNWs) in Northern Nigeria. Four meteorological stations (Bauchi, Kano, Hadejia, and Nguru) and three streamflow gauge statins (Hadejia, Katagum, and Gashua) were used to cover the HNWs’ catchment. The data was checked for normality using Anderson–Darling and Shapiro–Wilk tests. Pettit’s test was used to check for homogeneity in the data series, and absolute homogenization, using RHtestsV4 software, was applied to homogenize and pre-whiten the data series. Trend analysis was carried out using modified Mann–Kendall and Sen’s slope tests. Results revealed increasing positive trends at all the stations for monthly minimum, average annual minimum, average annual maximum, and annual average temperature data series, while monthly maximum temperature series of Bauchi and Kano stations indicated the presence of an increasing trend with magnitudes 0.0035 °C and 0.0019 °C; and no trend was detected for Hadejia and Nguru stations. For monthly precipitation, no trends were detected at all stations. However, an increasing trend was detected at Bauchi, Hadejia, and Nguru stations for mean annual precipitation with magnitude 7.7960 mm/year, 8.1766 mm/year, and 5.7214 mm/year, respectively. A decreasing trend was detected for monthly and annual streamflow series at Hadejia gauge station with magnitude − 0.0115 m³/s/month and − 3.7037 m³/s/year, respectively; and no trend was detected for monthly and annual streamflow series at Katagum and Gashua gauge stations. The trend analysis may be helpful for planning and management of water resources in the HNWs.