Development of water quality management strategies for an urban river reach: A case study of the river Yamuna, Delhi, India

The urban reach of River Yamuna at Delhi is contaminated with a high volume of wastewater inflows amounting to a flow of about 3600 MLD consisting of BOD as high as 200 mg/l entering through sixteen outfalling drains within the 22 km of reach. The present study intended to develop water quality management approaches to bring out the BOD and DO concentrations within the prescribed limits. Four different scenarios with twelve cases have been developed to attain this objective. The model QUAL2Kw was calibrated and validated with secondary data. RMSE values were determined to validate the predicted and observed values. Four scenarios, including bottom algal modification, pollutant load modification, pollutant load modification with diversion, and diversion with flow augmentation, were assessed for February 2019 with low flow conditions. The study showed that flow augmentation and diversion of some drains (D1, D11, D12, D13) could ensure the required criteria for BOD < 3 mg/l throughout the reach. At 33 km from upstream, local oxygenation was required to maintain DO above 4 mg/l. Advanced treatment in drain 1 and diversion of a few smaller drains can also maintain the required standards. Results indicated that the reach required a combination of bottom algal reduction, flow augmentation, load modification, and local oxygenation to sustain the river quality. The present study attempts to develop a novel strategy for river water management under different scenarios for the urban reach of the Yamuna River, which is almost anoxic after outfalling drain 1.