"When a river is spread out in a reservoir, it creates more inputs of solar heat. There is more water here to absorb sunlight, and we often increase temperatures in that pool. This is especially a problem in a coldwater stream where trout, for instance, will disappear if the temperatures get too high. In some of the larger reservoirs, often tailwater areas may release bottom water from this reservoir, which is much colder, and we can have the opposite thing happening in the tailwater. In a warmwater stream, we may convert that tailwater area into coldwater habitat. And in the large reservoirs out west, we actually get more of a coldwater system, which may have a localized trout fishery, but at the cost of the native warmwater species."