PrintPollution
In addition to the increased nutrient concentrations from agricultural return flow downstream of dams, the reduction in flow velocity in slackwater behind dams leads to reduced flushing of pollutants that enter the river. In areas subject to high rates of municipal or industrial wastewater discharge, or to agricultural runoff, this can lead to significant impairment of water quality in the reservoir itself, and in upstream tributaries (for example, see Three Gorges: A “Mega-Dam” and its Impacts). High nutrient fluxes can also lead to eutrophication of the reservoir. Additionally, the increased surface area of reservoirs leads to large evaporative losses and subsequent increases in water salinity, especially in arid and semi-arid climates.