Identifying lithogenic and anthropogenic factors responsible for spatio-seasonal patterns and quality evaluation of snow melt waters of the River Jhelum Basin in Kashmir Himalaya

Abstract

The characterization and evaluation of water quality in the Jhelum River Basin is indispensable due to its immense significance in supporting the livelihoods of people and various ecosystem services. Anthropogenic pressures, however, in the form of forest degradation, reckless use of fertilizers and pesticides, land system changes and unplanned settlements are diminishing pristine basin water quality, which necessitates better understanding of pollution variability and its sources. Extensive field sampling across major tributaries and along main river course was carried out during the year 2017–18. Pattern recognition techniques like Hierarchical Cluster Analysis (HCA), Wilk’s λ quotient, Principal Component Analysis (PCA) and Analysis of Variance (ANOVA) were applied to a huge dataset comprising of 5192 observations. Spatially, three clusters correspond to low pollution headwater streams (cluster 1), moderately polluted middle and downstream sites (cluster 2) and high polluted main river course sites (cluster 3). This is also supported by ANOVA results, manifesting significantly higher concentrations of total hardness (TH), calcium (Ca), magnesium (Mg), chloride (Cl), total alkalinity (TA), nitrate-nitrogen (NO3-N), total phosphorus (TP), iron (Fe) and total coliform (TC) in high pollution associated cluster (cluster 3) followed by cluster 2 and minimum quantities were observed in cluster 1. Observations on seasonal water quality either did not fluctuate considerably or differs significantly during summers only, except water temperature (WT), which exhibits significant difference in all seasonal clusters. Wilk’s λ quotient distribution revealed that only WT was main contributor in the formation of seasonal clusters. PCA recognized five underlying factors in the data structure and explained about 72% of total variance. Maximum variance (22.66%) is explained by combination of ionic salt group (natural source) and TC (anthropogenic source) followed by dissolved ions (19.20%) causing hardness and buffering of waters, nutrient sources (15.08%) from human and agriculture wastes, gradient factor (7.87%) allied with small fall in dissolved oxygen (DO) downwards and pH (7.11%) linked with hydrolysis of acidic material accrued from organic matter. The water quality index (WQI) was mostly influenced by coliform bacterial count and pH with highest mean effective weights of 39.15% and 26.65% respectively. Evaluation of the water suitability for drinking purpose reveals that the Jhelum River Basin has mostly retained excellent water quality (66% of data points) but poses safety concerns in downstream segments due to anthropogenic signatures.