Seasonal variation of surface water quality and streamflow in Rispana: A tributary of Ganges river, India

To evaluate the seasonal changes in quality and quantity of river Rispana (a tributary of river Ganges-Dehradun region of India) water quality index (WQI) was calculated at four major locations by using the weighted arithmetic method. Sixteen samples in all were taken throughout the pre-monsoon (April 2022), monsoon (July 2022), post-monsoon (November 2022), and the Winter season (January 2023). The major parameters, namely, temperature, dissolved oxygen (DO), pH, electrical conductivity (EC), and total dissolved solids (TDS), E-coliform, sulphate, total alkalinity (TA), total hardness (TH), and biochemical oxygen demand (BOD) were considered for calculation of WQI. The WQI varied from minimum 44.53 (good) at site 1 - Kairwaan Gaon during monsoon season to maximum 302.69 (unfit for drinking) at site 4 - Mothrowala during the pre-monsoon period. In 75% samples quality of water was unfit for domestic purpose and the contributing factors are DO, BOD, and Coliform which exceeds permissible limit in all samples. The major factors attributed for decline in the Rispana water quality are discharge of sewage, commercial sites effluent, and urban runoff. Pre-monsoon, monsoon, post-monsoon, and winter had average total coliform levels of 1849.6, 2419.6, 2419.6, and 1546.25, respectively, in MPN units. The average value of E-coli for the four season vary from 1306.8 to 1888.1 MPN. The pollution load (physico-chemical parameters and bacteriological factors) increases as the river Rispana flows to downstream in urban locations. Streamflow was observed as very lean except monsoon season (similar to 1500 cfs) due to more extraction of Rispana's fresh water in upstream and unplanned changes in its catchment basin; thus establishes an extensive decline in availability of fresh water sources (Domestic use) in downstream Dehradun city area. In monsoon season, more streamflow (rain water influx) maintains the WQI also in good-moderate category. The land use/land cover - LULC analysis in Rispana basin area, depicted 71% enhancement in urbanization (24.16%-41.55%) takes place in 15 years' span (2003-2017). The study establishes the potential causes (natural and anthropogenic) for Rispana deterioration and provides a baseline (quality index) for aquatic and ecological rejuvenation of its watershed by executing a proper management strategy with people participation. This work contributes discernments for effective water resource management to address the smart city objectives and sustainable development goal-SDG:6, urban and municipal authorities must take cognizance for revival of this domestic water resource.