Improving water quality from source-to-sea requires managing both point and diffuse sources of pollution. One of the main policy challenges facing OECD countries is the effective management of diffuse sources of nutrient pollution, which are caused by activities that have no specific point of discharge, and are often linked to agricultural and urban pollution via overland flow to surface waters.
Unless attention is turned to these diffuse sources, further deterioration of water quality and the ocean can be expected as human populations grow, industrial and agricultural production intensifies, and climate change causes significant alteration to the hydrological cycle.
Globally, one of the most prevalent water quality challenges is eutrophication; a form of water pollution caused by excess use of nutrients (nitrogen and phosphorous). Eutrophication can trigger toxic algal blooms and cause “dead zones” (oxygen depletion) in the ocean and coastal waters leading to significant loss of marine biodiversity. Excessive nitrogen in the environment also contributes to climate change, depletion of the ozone layer, air pollution, nitrate toxicity in groundwater and drinking water, loss of biodiversity and deterioration of soil quality.