Assessing climate extremes and adaptation practices: a case of selected Water, Sanitation, and Hygiene (WASH) systems of Nepal

ABSTRACT A graphical abstract describes a concise, visual summary of a research paper's main findings. It presents the climate change and study methodology, hydro-climatic extremes and impacts, current adaptation responses and limitations, and recommendations/ way forward for climate-resilient WASH systems in Nepal. Climate change is intensifying hydro-climatic extremes across Nepal, triggering risks to water, sanitation, and hygiene (WASH) systems. This study analyzed historical climate records (1994–2024) with global climate models (GCMs) under moderate and worst-case scenarios, complemented by a questionnaire survey across three physiographic regions of Nepal. Historical trends reveal longer dry spells, fewer wet spells, declining precipitation, rising temperatures, and increasing climate extremes; these resonate with water source depletion/drying up, quality deterioration, and unreliable WASH services. Future projections indicate intensification of these trends; in worst-case scenario, Siwalik/hill experiencing severe precipitation extremes: five-day precipitation projected to increase by 1.87 mm/year, heavy-precipitation days by 0.56 days/year, and annual precipitation by 22.27 mm/year, intensifying floods and landslides. High-mountain facing accelerated warming (TXx: + 0.07 °C/year and TXn: + 0.10 °C/year), threatening snowmelt-dependent water sources, while middle-mountain shows moderate but continued increases across both climate extremes. Although communities have practiced adaptations, mainly water source conservation-protection, wastewater reuse, rainwater harvesting, among others, they remain fragmented and insufficient against projected risks. Three pathways reveal linkages between climate extremes and WASH impacts, with some policy-practice gaps. The study recommends embedding climate extremes into WASH planning, developing climate-resilient infrastructure, integrated and inclusive adaptation strategies, and strengthening stakeholders' capacity to build resilient WASH systems in Nepal.