The Lower Elwha Indian Reservation covers 372 acres at the mouth of the Elwha River in Clallam County, Washington. The land of the reservation is used principally for residential purposes and growing forage for cattle. The population of the reservation is largely dependent upon fisheries resources for its economic health.
This study was made to assess the availability and suitability of ground water on the reservation for domestic use and for fish propagation, to determine the streamflow characteristics of the Elwha River and Bosco Creek, and to determine the chemical and physical quality of the area's surface and ground waters.
Existing wells on the reservation range in depth from about 30 to about 80 feet, and produce water of excellent chemical quality. Properly constructed wells in favorable locations on the reservation should be capable of large yields, up to 5,000 gallons per minute. Intrusion of seawater into the aquifers of the reservation has not occurred. However, if massive quantities of ground water are withdrawn, intrusion could occur.
The Elwha River, which flows along the western margin of the reservation has a mean annual flow of about 1,500 cubic feet per second (ft3/s). The recorded minimum daily discharge was 10 ft3/s, and the maximum was 41,600 ft3/s. The river floods the lower parts of the reservation annually, and extensive flooding is common. Water in the Elwha River is of excellent chemical quality, and its recorded temperature has ranged from 36° to 64°F. Bosco Creek, the only other stream on or adjacent to the reservation, has an estimated mean annual flow of 1.1 ft3/s.
Water resources of the Lower Elwha Indian Reservation, Washington