Science of the CSKT Water Rights Compact

Starting in 1982, the Confederated Salish and Kootenai Tribes embarked on a deliberative process to collect hydrologic data and technical information concerning Reservation water resources. Through this effort the Tribes have developed a thirty+ year dataset, often on small and generally overlooked water resources, and have developed an in-depth understanding of surface and ground-water resources and their interaction. This information has broad application for ongoing water resources management. Also, for several decades the Tribes have recognized that their reserved, but unquantified, water rights would need to be perfected either in a negotiated or adjudicatory setting. Recognizing the complexity of water use on the Reservation and the challenges of interjecting unquantified reserved rights into already over-utilized waters, the Tribes have consistently sought in their negotiation efforts to apply a forward-looking and scientific approach to water allocation. Rigorously developed water budgets for natural and modified hydrology form the base level for this perspective, and the Tribes have applied the HYDROSS allocation model as the container to hold and distribute water budget terms across the Jocko, Mission and Little Bitterroot Valleys; areas which are highly modified by irrigated agriculture served by the Flathead Indian Irrigation Project. Prior to and concurrent with modeling work, major water budget terms - e.g. natural and modified hydrology, crop types and crop water consumption, irrigated acreage, and irrigation project infrastructure -- were developed as stand-alone work products and inputs to the modeling framework. This significant level of technical effort is distilled in the Compact into a set of numeric tables and rules for implementation, the tip of a pyramid built on years of technical endeavor