Modeling Surface Runoff Under Climate Change Scenarios: An Integrated SCS-CN and GIS Techniques in a High Andean Basin of Puno, Peru

Surface runoff is crucial in the hydrological cycle, influencing freshwater availability, soil erosion, and water quality. Climate change will alter precipitation patterns, increasing floods and droughts, exacerbating soil erosion, and affecting the ability of watersheds to retain and filter water, which will impact global water security. This study analyzes surface runoff in the Huancané river basin, Peru, highlighting its importance for water resource management in climate change, using historical precipitation data (1956-2009) from SENAMHI and climate models (HadGEM3-GC31-LL and MPI-ESM1-2-HR) under the ssp126 and ssp585 scenarios. The methodology included using the Curve Number (CN) method for different land covers, soil, and slopes, together with overlapping thematic maps to analyze the spatial variability of runoff. The results show that areas with impermeable soils and open vegetation register the highest runoff values. At present, runoff varies between 0-230 mm (869.3 km²), 230-460 mm (1583.0 km²), and 460-636 mm (1107.8 km²). Under the ssp126 scenario, significant increases in precipitation and runoff are projected, especially in the lower part of the basin, with values that can reach up to 720 mm and affect 1517.8 km². For the ssp585 scenario, runoff values increase even more, with areas experiencing up to 720 mm of runoff affecting 1488.8 km². The weather stations analyzed show significant increases in future precipitation, with an average increase of 100-300 mm, exacerbating runoff problems, particularly in areas with impermeable soils and high slopes. We conclude that integrated watershed management that considers conserving vegetation cover, implementing efficient drainage systems, and sustainable agricultural practices is essential to mitigate the negative impacts of runoff. Long-term planning and collaboration between different stakeholders will be crucial to face the challenges of climate change and protect the natural resources of the Huancané river basin, ensuring its sustainability and resilience.