Trend Analysis of Observed Precipitation, Temperature and Streamflow for Hadejia – Nguru Wetlands Catchment, Nigeria

Abstract This study investigated trends in hydro-climate data (precipitation, maximum/minimum temperatures, and streamflow) for the period 1980–2016 in a semi-arid Hadejia-Nguru Wetlands (HNWs) catchment, Nigeria. Four meteorological stations (Bauchi, Hadejia, Kano and Nguru) and three streamflow gauge stations (Gashua, Hadejia and Katagum on Rivers Yobe, Hadejia and Jama’are respectively) covers the HNWs catchment. Anderson-Darling and Shapiro-Wilk normality tests were applied on the monthly hydro-climate data series to determine their class of distribution. A non-parametric Pettit’s test for homogeneity was employed to detect change points in the data series. An absolute homogenization method using RHtestsV4 software was applied to homogenize and (as needed) pre-whitened the data series. Trend analysis was carried out using modified Mann–Kendall trend test (trend free pre-whitening approach), while Sen’s slope was used to estimate the magnitude of the changes. Results of the study revealed that there was an 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 magnitude 0.00350C and 0.00190C; and no trend was detected for Hadejia and Nguru stations. For monthly precipitation, no trends was detected at all stations. However, an increasing trend was detected at Bauchi, Hadejia and Nguru stations for mean annual precipitation with magnitude 7.7960mm/yr, 8.1766mm/yr and 5.7214mm/yr respectively. A decreasing trend was detected for monthly and annual streamflow series at Hadejia gauge station with magnitude − 0.0115m3/s/month and − 3.7037m3/s/year respectively; and no trend was detected for monthly and annual streamflow series at Gashua and Katagum gauge stations. The trend analysis may be helpful to water resources managers for planning and management of water resources in the HNWs catchment and the Hadejia Jama’are Komadugu Yobe Basin at large.