The Idaho Water Resource Board manages the operation of Idaho's Water Supply Bank. The purposes of the Bank are to encourage the highest beneficial use of water; provide a source of adequate water supplies to benefit new and supplemental water uses; and to provide a source of funding for improving water user facilities and efficiencies. The history of the Idaho water bank system began in the 1930s.

In its most simplistic sense, the Water Supply Bank is a water exchange market operated by the Board to assist marketing of water rights to natural flow water or water stored in Idaho reservoirs.

Using the Bank, water users who in any given year have rights to more water than they require can put the excess stored water or natural flow rights that will not be used in the Bank. From there, the water can be sold or leased to people who do not have enough to meet their needs. This system helps make excess water available to other users for such things as irrigation or other authorized uses. Water Bank water also has proven valuable by providing stored water for downstream salmon recovery efforts. This Water Bank approach helps put the maximum amount of water to beneficial use.

Categories of Water in the Bank

Water in the Bank involves two distinct categories of water:  The first is natural flow water. This generally involves rights to surface water diverted from a river, stream or groundwater. The Board directly controls the sale or rental of water covered under natural flow water rights.

The second is stored water, that is water stored in "rental pools" in reservoirs. There are currently four rental pools operated by local committees appointed by the Board in Idaho. They involve water from the Snake River upstream from Milner Dam near Burley (including a separate bank operated by the Sho-Ban Tribes), the Boise River and the Payette River.

See side column for lists of procedures the local committees follow.