In Southern Idaho, as in most of the western US, available fresh water supplies are essentially fully appropriated and future economic growth depends upon the ability to transfer water rights from lower value uses. These transfers often involve a change in use of the water as well as a change in location of the point of diversion. The change in location creates special administrative challenges when dealing with ground water rights. The effects of ground water use can propagate throughout an aquifer and affect nearly every ground and surface water user in the basin. A spreadsheet based Ground Water Rights Transfer Tool has been applied in the Eastern Snake River Plain in southern Idaho for several years. The Transfer Tool uses a ground water flow model of the aquifer to calculate the hydrologic effects of changes in well location on surface and ground water exchange in 11 different reaches of the Snake River. Typically, the rate or volume of a right will be decreased in the transfer process because of increased levels of impact to one or more of the 11 reaches of the Snake River.