The Skagit River instream flow rule was based on scientific studies conducted and peer-reviewed by third-party consultants. In June 1999, Duke Engineering and Services, Inc. issued its technical report. This report was reviewed for validity and appropriateness by Hardin-Davis, Inc. in March 2005. The 1999 Duke report is the basis for the Skagit River instream flow rule (WAC 173-503).
The United States Geological Survey, in partnership with Skagit County Public Works, Skagit County PUD No. 1, and Ecology, has studied groundwater conditions in the lower Skagit River basin and developed a groundwater flow model. The studies and model are intended to understand the physical system and evaluate the effects of potential groundwater withdrawals and consumptive use on streamflow in four tributary sub-basins (the east fork and mainstem of Nookachamps Creek, Fisher Creek, and Carpenter Creek).
- Numerical simulation of the groundwater-flow system in tributary subbasins and vicinity, lower Skagit River basin, Skagit and Snohomish Counties, Washington – USGS Scientific Investigations Report 2010-5184, 78 p. Johnson, K.H., and Savoca, M.E., 2010.
- Hydrographs showing groundwater level changes for selected wells in the Lower Skagit River Basin, Washington – USGS Data Series 441, Fasser, E.T., and Julich, R.J., 2009.
- Hydrogeologic framework, groundwater movement, and water budget in tributary subbasins and vicinity, lower Skagit River basin, Skagit and Snohomish Counties, Washington – USGS Scientific Investigations Report 2009-5270, 46 p. Savoca, M.E., Johnson, K.H., Sumioka, S.S., Olsen, T.D., Fasser, E.T., and Huffman, R.L., 2009.
- Shallow groundwater movement in the Skagit River Delta area, Skagit County, Washington – USGS Scientific Investigations Report 2009-5208, 22 p Savoca, M.E., Johnson, K.H., and Fasser, E.T., 2009.
Water solution studies