STABLE ISOTOPE SIGNATURES OF WATER SOURCES IN SAGARMATHA NATIONAL PARK, NEPAL

Water resources in the Himalayan region are highly vulnerable to a warming climate and anthropogenic impacts. The headwaters of the Mount Everest region provide critical water sources and are threatened by retreating glaciers. This study was conducted in the Sagarmatha National Park (SNP) region to determine (a) stable isotopes of springs, rivers, and domestic waters at varying elevations, (b) isotope altitude lapse rates, and (c) meltwater contribution using a two-component mixing model. Spring and surface water, glacial meltwater, and rain samples were collected during the pre-monsoon dry seasons in 2017,2018, 2019, and 2022 along the trekking route from Lukla (2845 m) to Mt. Everest Base Camp (5315 m). Khumbu glacier meltwater and rainwater endmembers were used to estimate meltwater contributions. Surface, springs, and domestic water samples δ¹⁸O values ranged from -11.97 to -16.28 ‰. Water samples at higher elevations indicated signatures of snow/glacier melt sources. Altitude lapse rates of δ¹⁸O and δD are -2.57 ‰ km^-1 and -21.80 ‰ km^-1, respectively at 2500-5100 m elevations. The yearly average meltwater contributions in domestic water ranged from 60.57 - 66.54%. These significant meltwater contributions suggest that future warming and glacier melting may have an effect on the local water supplies in the SNP.