Spatial Variation of Nutrient Concentrations (NH<sup>+</sup><sub style="margin-left:-5px;">4</sub> and Cl<sup>-</sup>) in the Dudhkoshi River Basin, Sagarmatha National Park, Nepal

Abstract

The Sagarmatha National Park (SNP) in Nepal is home to unique natural beauty and cultural significance. While the SNP has a relatively small local population, it has drawn thousands of visitors since Edmund Hillary and Tenzing Norgay reached the peak of Mt Everest in 1953. Importantly, the tourists and their concurrently generated refuse have caused massive anthropogenic pressure with serious environmental consequences for the unique SNP and SNP Buffer Zone ecosystems. This study aimed to understand the spatial variation of nutrient concentrations in stream water and drinking water (primarily shallow springs) using analyses of nitrogen as NH+4 and chlorine (Cl-) concentrations. Sampling occurred in April 2017 during the pre-monsoon dry season in the upper Dudhkoshi River Basin, SNP. Dissolved inorganic nitrogen (NH+4) concentrations in both drinking water and stream water were low with average concentrations in drinking water of 0.016 mg/L (±0.010) and 0.033 mg/L (±0.031) in stream water. Similarly, Cl- concentrations were also low with average concentrations of 0.185 mg/L (±0.045) and 0.124 mg/L (±0.051) in stream and drinking water, respectively. Importantly, nitrogen in stream waters exhibits a decreasing trend with altitude whereas Cl- values decrease with altitude in both drinking water and streams. The observed spatial variations of nitrogen and chlorine concentrations are attributed primarily to the significant variations in land use/land cover from the highest portions of the drainage basin to the lowest elevations, which are outside of the SNP boundary and therefore allow more agricultural development. Our results demonstrated that although the quality of stream water in the upper reach of Dudhkoshi River Basin meets WHO standards for drinking water, there is significant surface water contamination in the form of agricultural run-off. These results will provide base-line data for further studies and will help to improve understanding of the relationship between land use/land cover and water quality in the region.