Platte River Basin
Modified North Platte Decree
The U.S. Supreme Court revisited Nebraska v. Wyoming (1945) in 1953, 1993, 1995, and 2001. The 2001 Modified Decree expanded the limitation on irrigation in Wyoming to include both consumptive use and irrigated acreage above Guernsey Reservoir. The Modified Decree added a consumptive use cap for irrigation purposes above Guernsey Reservoir (except Casper/Alcova Irrigation District) and expanded the 1945 Decree's limitation on irrigated acreage above Guernsey Reservoir (with the same exception) to include tributaries between Pathfinder and Guernsey Reservoirs. The Court remained consistent in support of the historic sectionalized administration of the river, where available flows have been equitably apportioned between the states with certain specified limitations on acreage, consumptive use, and reservoir storage. The 2001 Modified Decree and related settlement stipulations also provided for an automatic priority call for the mainstem federal North Platte River reservoirs in Wyoming when forecasted water supplies are less than 1.1 million acre feet.
The “Green Area” maps depict the geographic boundaries of the North Platte River sub-basins where groundwater resources are considered non-hydrologically connected to the North Platte River and its tributaries under application of the 2001 Modified North Platte Decree (Decree) criteria, and subsequently adopted for the Wyoming Depletions Plan as part of the Platte River Recovery Implementation Program (Program). The Green Area maps are broken into sub-basin areas as depicted on the attached Figure 1. Three of these sub-basin maps were developed as a result of the settlement of the 1986 Nebraska v. Wyoming lawsuit as documented in the Decree and Final Settlement Stipulation and adopted by the U.S. Supreme Court. These sub-basin maps are entitled: Above Alcova Dam, Alcova Dam to Guernsey Dam, and the Lower Laramie Basin.
Green Area Maps
Ground Water and the Green Area
Surface Water and the Green Area
The Green Area maps have no Decree implications for surface water sources in the North Platte River Basin in Wyoming, with the exception of springs. Irrigated acreage that relies solely on spring sources emanating within Green Areas are considered to be non hydrologically connected and are not accounted for under the acreage limits contained within the Decree.