Projection of the risk of nutrient pollution and eutrophication for mid-21st century under changing climate and land use land cover

Large industrial pollution, agricultural runoff, and disposal of untreated sewage into the river have made Kanpur the most critical water pollution hotspot of Ganga River. This study assesses the risk of nutrient pollution and resulting eutrophication in this industrialized stretch passing through Kanpur for the mid-21st century under climate change and land use land cover projections. For this assessment, climate projections from an ensemble of 20 GCMs for the RCP 4.5 and RCP 8.5 scenarios, and future land use land cover (LULC) projections from a multi-layer perceptron neural network are used to drive a hydrological model HEC-HMS which is coupled to the water quality model QUAL2K. The nutrients assessed are ammonia, nitrate, total nitrogen, organic-, inorganic- and total phosphorous. An increase in nutrient pollution is simulated for future climate change due to a reduction in dilution volume caused by reduced low flows. An increase in nutrient pollution is also simulated for future land use land cover because of an increase in pollution from agricultural runoff. Both nitrogen and phosphorous components are highly sensitive to climate change, while only phosphorous components are highly susceptible to land use land cover. This is because, the major contribution of phosphorous pollution in this stretch is from agricultural runoff and only a negligible contribution is from point sources. The risk of nitrate pollution decreases and ammonia pollution increases with future climate change due to higher denitrification rate with warming, but the risk of total phosphorous pollution slightly decreases due to an overall reduction in phosphorous with warming following an overall increase in mean streamflow. A shift in the hotspot of eutrophication from Kanpur to Jajmau is also simulated due to limiting phosphorous eutrophication for future climate at Kanpur. The risk of eutrophication would increase with future climate change due to increased total nitrogen and total phosphorous with warming, and the risk is likely to become higher for the combined climate change and land use land cover projections. The results of this ongoing study will be presented in the meeting. Our study would be highly beneficial for the policymakers to save the Ganga River from further pollution in the future.