A more thorough explanation:

The implied-reservation-of-water doctrine is a legal principle that allows the federal government to use and control water that is connected to federal lands for public purposes. This means that the government can claim ownership of water resources that are adjacent to federal lands, even if the water is not explicitly mentioned in the land title.

For example, if the government owns a national park that includes a river, it can claim ownership of the water in that river and use it for public purposes like providing drinking water or generating hydroelectric power.

The implied-reservation-of-water doctrine is based on the principle of eminent domain, which gives the government the power to take private property for public use as long as it provides just compensation to the owner.