SWE was retained by the State of Montana to assist with investigation of compliance with the Yellowstone River Compact, ratified in 1951.  The lawsuit was filed in the United States Supreme Court in 2007.  After an initial report was filed by the Special Master appointed by the Court in 2010 and the Court’s ruling on exceptions in May, 2011, the case proceeded to trial.  At issue was Wyoming’s compliance with Article V.A. pertaining to protection of pre-compact water rights in Montana on the Tongue River.  The river and its tributaries supply irrigation for approximately 70,000 acres in Wyoming and 24,000 acres irrigated from the Tongue River in Montana.  The Tongue River Reservoir is a pre-compact facility located just downstream of the Stateline in Montana.  The issue at trial was the administration of post-1950 water uses in Wyoming, reservoir administration and operation and the resulting hydrologic impacts at the Stateline.

SWE conducted hydrologic investigations of water use in Montana and Wyoming in the Tongue and Powder River tributaries of the Yellowstone River for the State of Montana.  The analyses were made to assess compliance with the provisions of the Yellowstone River Compact.  Technical analyses included mapping irrigated area, analysis of crop evapotranspiration, water rights documentation and reservoir operations.  Hydrologic water rights and water use records were compiled and summarized, and hydrologic impacts to streamflows resulting from irrigation and reservoir operations were quantified.  Mr. Book conducted investigations of issues and data and provided expert witness testimony at trial, conducted by the Special Master during 2013.  The case is currently pending before the Special Master.