Water quality appraisal of a Mountainous River: A case study of Rispana river, Dehradun

Rispana river is one of the many tributaries of river Ganga flowing through Dehradun. Rispana river originates from the Mussorie hills and traverses through Dehradun and finally joins river Bindal at Mothrowala in Dehradun. The total catchment area, Drainage length, and Chainage length of Rispana river is 58.09 km², 130.19 km, and 12.55 km respectively. The quality of river water was monitored throughout its length during Dec. 2018 to April 2019. Total dissolved solids (TDS), alkalinity, sulfate, hardness, aluminium, iron, lead, manganese, and cadmium exceeded the permissible limits prescribed by BIS for drinking water at one or more locations, and is-a concern as Rispana is the major source of drinking water for the city, residential schools, and hamlets in its-vicinity. The biochemical oxygen demand (BOD) values in the river water ranged from non-detectable to 390 mg/l. The E-coliforms were detected throughout the river length with counts ranging from 1 to 2419600 MPN/100 ml indicating fecal contamination of river demanding proper disinfection before potable use. The water quality-of the river was observed to be influenced with geology of the catchment and also anthropogenic pollution. The study indicates that the status of the river requires significant investment in wastewater treatment and catchment-treatment to improvise its quality for many purposes including aquaculture in the lower reaches. We propose increased implementation of sewerage network along with decentralized wastewater treatment in the catchment for reducing the organic, nutrient and pathogen load entering the river.