Nutrient Pollution - Dissolved inorganic phosphorous (DIP) in rivers per river basins (risk category)

Phosphorous is an important cause of river nutrient pollution caused mainly by agricultural activities (fertiliser use and wastes from livestock), urban wastewater, and atmospheric deposition of nitrogen. Contamination by nutrients (particularly forms of nitrogen and phosphorous) increases the risk of eutrophication in rivers, which can pose a threat to environmental and human health (e.g. algal blooms, decreases in dissolved oxygen, increase in toxins making water unsafe for humans and wildlife, etc.). Five risk categories were developed based on published national river water quality criteria, with a risk factor of 5 being the highest risk for eutrophication and 1 the lowest. This indicator represents annual-scale mean river phosphorous concentration for the entire basin. Output is in kg P per year normalized by basin area. Results output is average for the basin, but most input data sets (for sources of pollutants) are calculated at 0.5 degree grids. River concentrations were then calculated as yield divided by water runoff. Basin area – part of NEWS inputs based on STN30 watershed delineations, presented in km2. This assessment is originally derived for Global NEWS 2 basins (Mayorga et al, 2010; Seitzinger et al, 2010) by assuming that the mean annual concentration at the basin mouth (where the mainstream river drains to the coast or to endorheic terminal points) is representative of river channel concentrations across the basin.