When making decisions about water allocations, state and federal water project managers must consider the short-term and long-term needs of agriculture, urban users, hydroelectric production, and flood control. They are also required by the Endangered Species Act (ESA) to make sure their decisions do not jeopardize the continued existence of any endangered or threatened species. The National Marine Fisheries Service (NMFS) evaluates water project impacts on threatened and endangered salmonids and provides a decision on these impacts by issuing a Biological Opinion (BiOp). For water projects across the United Sates the NMFS BiOps (or similar processes by other federal agencies) are the decision support systems (DSS) for water allocation decisions with respect to endangered species. The most recent BiOp for the Central Valley Project (CVP) in California was rejected by reviewers due to inadequate stream temperature and fish mortality models. These models are the current decisions support tools (DSTs) used in water allocation decisions, but are based on a monthly time step, which cannot take into account the fine scale temperature patterns that can be critical to salmonid survival. Thus NMFS is required to use models with finer spatiotemporal scales. Generating stream temperature estimates in near real time, at fine spatiotemporal scales, and over large geographic areas is problematic using existing modeling approaches. We propose to use NASA Earth Sciences data coupled with ecosystem and statistical models to produce improved DTSs for stream temperature and fish mortality in the western U.S. The proposed system will include nowcasting and forecasting capabilities that will provide stream temperature and fish mortality estimates for every 1km of stream reach at 15 minute intervals. The proposed improvements to the existing DSS will allow for substantially improved water allocation decisions by fisheries managers and water project managers.