Climate change threats to urban water supply in the Higueras river basin, Huánuco, Peru

ABSTRACT

A process diagram illustrating the steps followed for the modeling inputs and methodology, as well as the findings. These include the intensification of streamflow seasonality and the projected moderate to high long-term water stress in the Higueras River basin.

Climate change threatens water availability in semi-arid Andean watersheds, where cities such as Huánuco (Peru) rely primarily on surface water for urban supply. This study evaluates future changes in water availability in the Higueras River Basin by integrating projections from 22 CMIP5 Global Climate Models (GCMs), Bias Correction, the GR2M hydrological model, population growth projections, and the Water Stress Index (WSI). This integrated framework addresses a gap in previous Andean studies by integrating climate projections, hydrological modeling, and urban water demand. Future water demand was estimated assuming a 2.59% annual population growth rate and a per-capita demand of 220 liters/person/day. Streamflow was simulated for 2003–2019 and projected for the short (2020–2036), medium (2037–2053), and long term (2054–2070) under RCP4.5 and RCP8.5 scenarios. Results show water surpluses during the short term, whereas deficits emerge in August and September during the medium-term (up to 0.31 m3/s) and intensify during July–September in the long term, reaching 1.10 m3/s in August under RCP8.5. The WSI also indicates a transition from low to moderate/high water stress after 2065, especially under RCP4.5. These findings highlight the urgency for adaptive water management and planning in Andean cities reliant on surface water.