Pure, potable water is an essential resource, second only to breathable air in importance for life on earth, but it has other valuable attributes as well. It powers industry, provides recreation , irrigates agriculture, and is a highway for ships. It also takes many forms, from oceans, rivers, and lakes to groundwater and even atmospheric moisture. Given this vital significance, water rights have been contended throughout history.
One area of frequent dispute is jurisdiction. If a water right is a right to use water, then who has the authority to grant or withhold that right? The obvious answer is the government that has jurisdiction over the territory in which the water is found. However, water pays no attention to boundaries. A river that begins in one jurisdiction flows into another. Problems arise when people in the first jurisdiction deprive people in the other of a sufficient quantity or quality of water from the river. Such a situation forced the United States, which uses the Colorado River to irrigate several western states, to build a plant to remove excess salt from the Colorado before it flows into Mexico.
Impossible as it seems, jurisdiction over the water cycle has also been litigated. From atmospheric moisture comes rain and snow, which replenish groundwater and form streams that flow into rivers, which in turn flow into lakes and oceans. Surface water thus forms an interconnected system. International law has focused on rights to "international drainage basins" and, more recently, "international water resources systems" that include atmospheric and frozen water.
When jurisdiction is not at issue, water rights are usually established in one of three ways. The first was set out in the Institutes of Justinian (533-34 a.d.), which codified Roman law. This holds that flowing water is a res communes omnium —a thing common to all, at least when it is navigable. It cannot be owned or used exclusively by anyone. The second and third approaches have been developed in the United States, where the doctrines of riparian rights and prior appropriation predominate in the eastern and western states respectively. In a riparian system, landowners whose land borders a waterway have a special, if not exclusive, right to the water. In the arid western states, however, water rights derive from first use, not ownership, as in the "first in time, first in right" rule.
[Richard K. Dagger ]
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