Trend and change-point dynamics of urban water supply in Gondar City, Ethiopia: a sequential mixed-methods analysis

Urban water systems in sub-Saharan Africa face increasing pressure due to climate variability, aging infrastructure, and institutional constraints. This study examined the long-term trends and climate responsiveness of water sources supplying Gondar, Ethiopia, using monthly data from the Angereb Reservoir, groundwater wells, and springs (2011–2024). We applied Mann–Kendall tests, change-point detection, and the Standardized Precipitation Index (SPI) with lagged correlations, complemented by interviews and focus groups. The results showed that the reservoir output remained stable (τ = 0.048, p = 0.369), whereas groundwater (τ = 0.391, p < 0.001) and spring supply (τ = 0.256, p < 0.001) increased significantly. Change-point analysis revealed key shifts: surface water decline in July 2013, groundwater expansion in July 2017, and spring integration in June 2019. The SPI lag analysis indicated distinct response times: reservoir supply responded inversely after 11–12 months, groundwater after 3–12 months, and springs after 3 months. Despite increased production, household access did not improve due to population growth and distribution losses. Groundwater offsets the static reservoir output, but unmanaged use poses long-term risks. Incorporating climate-response lags and detected change points into seasonal allocation strategies is vital for strengthening urban water resilience during rapid population growth.