Policy Analysis Using RiverWare: Colorado River Interim Surplus Guidelines

During calendar year 2000, the Secretary of the Department of the Interior (Secretary), acting through the Bureau of Reclamation (Reclamation), considered the adoption of specific interim surplus criteria under which surplus water would be declared in the lower Colorado River Basin during an interim period that would extend through 2016. An Environmental Impact Statement was prepared to discuss the specific alternatives under consideration and to identify the potential environmental effects of implementing such criteria. Potential hydrologic effects of the alternatives compared to baseline conditions were analyzed using Reclamation's long-term policy model, implemented in RiverWare, a general-purpose river and reservoir modeling framework. Using RiverWare's rule-based simulation option, each alternative was represented in a different rule set and used to direct the particular simulation. Multiple runs were made to quantify the uncertainty with respect to future inflow hydrology. The results were then used to quantify the comparative impacts on various resources, including recreation, fisheries, special-status species, and energy production. The work culminated in the selection of a preferred alternative and the Record of Decision, which was signed by the Secretary on January 16, 2001.