The Priest Lake Water Management Study was initiated by the Idaho Water Resource Board (IWRB) to evaluate opportunities for improving operation of the Priest Lake and Priest River system in order to meet long-term management objectives. The study includes several action items.
Evaluate alternatives for maintaining required lake levels and for maintaining current minimum discharge requirements of 60 cfs downstream from the dam.
Assess potential structural and operational modifications to the Priest Lake Outlet Dam.
Analyze options to improve access and navigable conditions for the Priest Lake Thorofare.
In accordance with Idaho Code § 70-507, the dam is operated to maintain the lake levels at three feet on the USGS gage for recreational purposes.
Purpose and Objectives
Preservation of lake levels through the recreation season to support the local economy and meet the Idaho Code lake level requirements, and avoidance of negative impacts to downstream river flows.
Maintaining marine access through the Thorofare channel between Upper Priest Lake and Lower Priest Lake.
Project Study Area Description
Lower Priest Lake is approximately 18 miles long, has a maximum depth greater than 300 feet, and has active storage space of approximately 76,000 acre-feet. It is connected to Upper Priest Lake (which is approximately 5 miles long) by a three-mile long channel known as the "Thorofare," which has long been used by the public for recreation and access to the upper lake. A 1,400-foot-long breakwater structure at the north end of Lower Priest Lake is intended to manage sediment from the upper lake while providing wave and erosion protection to landowners at the south end of the lower lake.
The original Priest Lake Outlet Dam was constructed in 1951. The current dam was constructed in 1978 to replace the deteriorating original dam. The dams were constructed to maintain lake levels in Lower Priest Lake and manage downstream flows into Priest River. The dam is owned by IDWR and operated by a contractor on behalf of IDWR. The dam is approximately 12 feet high with gates that regulate discharge. It does not have an emergency spillway.
Priest Lake is located on the Priest River in the northern Idaho panhandle. It is a significant draw for tourism and recreation, both of which add to the economic impact of Bonner County. The area is known for the pristine variety of wildlife, clear and clean water, and recreational fishing opportunities.
In 2015, limited water supply and drought conditions in northern Idaho made maintaining the required summer lake levels and downstream flow in the river very difficult. This situation, coupled with concerns about the breakwater structure and Thorofare access issues, increased interest in developing both operational and engineered improvements to the entire system.
In response to area stakeholders' concerns, the IWRB authorized funding to perform an evaluation of strategies and options that could meet the long-term water management solutions for the Priest Lake and Priest River system.