Thermal pollution can cause significant ecological impact [1] when left unchecked; however, thermal discharge is regulated under the Clean Water Act [2], hence the usage of cooling ponds [3] and towers [4].

[1] https://en.m.wikipedia.org/wiki/Thermal_pollution

[2] https://www3.epa.gov/region1/npdes/merrimackstation/pdfs/ar/...

[3] https://en.m.wikipedia.org/wiki/Cooling_pond

[4] https://en.m.wikipedia.org/wiki/Cooling_tower