The production of the nuclear energy by the nuclear reactors requires lot of water. The water's role is to constantly keep cool the reactors because if they overheat there can be a disaster of big proportions.
Because of the heating up of the water the water changes its properties slightly. Those changes have big environmental impact, easily seen in the local flora and fauna in close proximity to the nuclear reactors. There is way to big of a percentage of bad mutations among the flora and fauna where the water is released from the nuclear reactors, where very often there's animals with either more or less extremities, two heads, weird growth and shape of the plants etc.
Rivers often start from the mountain streams and contain high amounts of oxygen. Rivers and streams grow larger as these waters merge. Rivers pick up sediments from the land as they flow. Lakes support many varieties of organisms, including plants in shallow,
