Council hears Palouse Basin aquifer feasibility update; study considers Clearwater River diversion
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Summary
Mayor Willard updated the council on a Palouse Basin aquifer feasibility study: the lower aquifer is declining about 0.72 feet per year; preliminary results expected late 2026; a diversion near Lewiston with roughly 40 miles of piping and treatment near Moscow is among the options under study to provide an estimated supplemental supply (~10 cfs) for long‑term aquifer stabilization.
Mayor Willard briefed the council on long‑term water‑supply work for the Palouse Basin on March 24, describing ongoing monitoring and a regional feasibility study.
Willard said the basin has been monitored since about 1992 and that the lower aquifer has been declining at an observed rate of about 0.72 feet per year despite existing watering regulations. After evaluating alternatives, "a diversion from the Clearwater River near its confluence with the Snake River appears most feasible," he said. The concept in the study includes approximately 40 miles of pipeline, multiple storage tanks, treatment likely near Moscow, and an elevation gain from roughly 740 feet to about 2,960 feet (much of that gain occurring in the first eight miles of alignment). The study is assessing conveyance, diversion and treatment options and whether supplemental water would be used for direct consumption, aquifer recharge or a mix of both.
Willard told the council that preliminary study results are expected later in 2026 and that earlier analyses suggested roughly 10 cubic feet per second of supplemental supply could stabilize aquifer levels over long time horizons. He urged residents to follow irrigation rules for summer and framed the project as an investment in future water security.
The council received the update but did not take formal action; staff indicated they will share study materials and continue coordination with regional partners.
