DRINKING WATER QUALITY IN THE ANNAPURNA CONSERVATION AREA, WESTERN HIMALAYAS, NEPAL

A drinking-water quality survey was conducted within the Annapurna Conservation Area (ACA), located in the western Himalayas of Nepal, in May of 2001. Water was sampled at twenty-six sources within the ACA along the main tourist trekking route from Pokhara to Muktinath. Most of the drinking water along the route emanated from springs or surface water at much higher elevation and were fed to the villages via gravity through high-density polyethylene pipes. These distribution systems were built by non-governmental organizations (NGOs) and designed to reduce both the time spent gathering water and the possibility of contaminating the water source via poor hygiene practices. Water was examined for indicators of contamination from sewage, agriculture, or industry, including total coliform and E. coli bacteria, nitrate, nitrite, ammonia, phosphate, sulfate, iron, manganese, and heavy metals. Drinking water sources were generally basic and low in total dissolved solids, with a mean pH of 8.0 and mean specific conductance of 0.210 mS/cm; ammonia, nitrite, and nitrate levels were all well below World Health Organization (WHO) and Nepali drinking water guidelines. Manganese was above the Nepali guideline in several samples, but phosphate, iron, and sulfate were generally very low. Unfortunately, 94 and 72 percent of the water samples were contaminated with total coliform and E. coli bacteria, respectively. Trace-metal contamination was also present with 42 percent of the samples above the WHO limit for mercury 1 ug/mL. 89 %, of the samples above the WHO limit for mercury were from within the Modi Khola River Basin, which is a tributary to the Kali Ghandaki. The Modi Khola is located just to the northwest of the urban center of Pokhara. Regression analyses of the mercury, cadmium, silver, and lead concentrations versus distance from Pokhara shows strong inverse relationships with R2 values of 0.86, 0.60, 0.54, and 0.39, respectively; all relationships were significant at p-values < 0.002. We hypothesize that much of the mercury is from fallout of atmospheric pollution originating in industrial areas to the south of the ACA; brought by the prevailing southeasterly winds into the mountains.