Office of Columbia River photo identifier

Office of Columbia River

Twin Lakes Water Storage

Water stored during high flows will be used to restore aquatic lake habitat, augment low flows in the Methow River, and mitigate for new water rights from the Columbia River.

The Project

The Twin Lakes Aquifer Coalition has applied for a groundwater right under application G4-34915 to withdraw groundwater near the Methow River to augment water levels in Twin Lakes area of Okanogan County that have been declining since 2001. TLAC will pump from wells in hydraulic continuity with the river only when adopted instream flows on the Methow River are met.

Water will be diverted from the Methow River through a 2.5 mile pipeline, and used to recharge Twin Lakes, Barnsley Lake, and the surrounding aquifer. Approximately 800 acre feet will be diverted to storage during each of the first ten years and 550 acre feet each year thereafter. The project will store about 1,600 acre feet and will return 300-450 acre feet annually to the river through the aquifer system. Although water withdrawals from the Methow River system will be limited to high flows, water returning to the river will be continuous and will be trusted to Office of Columbia River to benefit instream uses (1/3rd) and out-of-stream uses (2/3rd).

Amended Water Right Application

Posters Explaining the Project


Water storage opportunities providing significant benefit with limited impact on the environment are relatively rare. This project will restore water in Twin Lakes to historic levels while making available meaningful volumes of water for downstream users.

Expected Outcomes

  • Restore and maintain water levels in Big Twin, Little Twin, Barnsely and Dibble Lakes and the adjacent aquifer.
  • Restore and maintain recreational fisheries, wetland habitat and natural aesthetic appeal of these lowland lakes.
  • Augment streamflow in the mainstem Methow River during low flow periods.
  • Provide up to 450 acre feet of new water for instream and out-of-stream users.
  • Create new economic opportunities from mitigated permits on the Columbia River.

SEPA (State Environmental Policy Act)

In 2012, Ecology initiated project review under the State Environmental Policy Act (SEPA). Documents related to the SEPA process can be viewed below.

Under WAC 197-11-360 and -410, Ecology initiated scoping to evaluate the environmental impacts of the proposal. Written scoping comments were accepted through December 14, 2012. An open house as also held in Winthrop, WA on November 7, 2012.

Supporting Environmental Documents

Substantial environmental study has been compiled to support the SEPA process. The following library of environmental documents are available.

Photo: Aspect Consulting

Photo: nwcamera

Under RCW 90.90.010, water returning to the Methow River will benefit Methow River low flows (100-150 acre-feet) and mitigate for new water rights downstream (200-300 acre-feet).

Methow Valley, Okanogan County

Twin Lakes Aquifer Coalition