Thermal pollution, or overheated water, is often associated with industrial discharges, but also includes the more pervasive problem of stream overheating due to inadequate stormwater management in developed areas. When rainfall generates surface runoff in the summertime, it becomes heated due to its flow over hot surfaces (think of summer thunderstorms falling on asphalt-paved parking lots).
If such water flows into streams, they will become much hotter than they were prior to development. Other effects of inadequate stormwater management are excessive streambank erosion which causes loss of tree cover and allows the sun to heat streams, and the loss of groundwater recharge between rainstorms, reducing flow and magnifying the effects of solar heating. Higher water temperatures are directly harmful to most organisms, and also drive off dissolved oxygen, which remains deficient even when the water cools.