Water quality assessment through numerical indices in Phewa Lake, Nepal

Abstract

ABSTRACT Pokhara valley is gifted with nine lakes out of which the largest lake, Phewa is the lifeline for the economic development of that region. However, the lake water is deteriorating owing to wastewater discharge from nearby hotels, restaurants, and urban settings. Therefore, the current study aims to rate the status of water quality in Phewa Lake concerning the water quality index (WQI), heavy metal pollution index (HPI), and pollution load index (PI). Ten selected physicochemical parameters like pH, electrical conductivity, total dissolved solids, nitrate, dissolved oxygen, biological oxygen demand, turbidity, hardness, chloride, and alkalinity were analysed for the calculation of WQI. Likewise, iron (Fe), lead (Pb), zinc (Zn), manganese (Mn), and nickel (Ni) were selected for HPI and PI calculations. The average WQI value in the winter, rainy, and autumn seasons of 2021 was 33.64, 66.94, and 58.71 respectively. In general, water quality was good in the WQI classification and it showed significant differences seasonally. However, the value of HPI and PI indicated that the water of Phewa Lake is polluted with heavy metals. The study findings are a useful database that is important for the concerned authorities for effective lake management.