however maintaining these processes to manage point source pollution is essential and must not be abandoned diffuse pollution from stormwater runoff and combined sewer overflows is an ongoing challenge for cities climate change will exacerbate existing water quality challenges due to altered precipitation flow and thermal regimes and sea level rise which will mean water authorities and water and sanitation utilities will be confronted by further economic and operational challenges however freshwater ecosystems are under immense pressure as a result of a legacy of industrial pollution and alteration of the natural morphology of water bodies continuing pollution from diffuse sources agricultural and urban and an everevolving number of emerging pollutants in wastewater