Multi-disciplinary decision support systems (DSS) are required to assist decision-makers in water resources management. These DSS need accurate and timely hydrometeorological information for reservoir operations, and river basin management, and planning. This paper discusses the decision support systems, and their application using relational data bases and state-of-the-technology forecasts used by the Bureau of Reclamation (Reclamation), US Department of the Interior, to make its water storage and conveyance facilities less vulnerable to variations in the water cycle including extremes of droughts and floods.

Reclamation serves over 31 million Americans in 17 Western States, providing over 9.3 trillion gallons of water and 45 billion kilowatt hours of electricity, and delivers irrigation water to over 140,000 farms each year. Consequently, river basin managers must have timely data from remote areas that are often inaccessible in winter, and have a means of quickly analyzing the impacts of precipitation and snowmelt on streamflow for routine river system management, and emergency responses to extreme events. Therefore, Reclamation uses a variety of hydrometeorological observing systems that it maintains, and cooperates with other agencies in collection of additional data. Reclamation's hydrometeorological and early warning systems provide data for decision support tools. Reclamation's Science and Technology studies focus research in the Watershed and River Systems Management Program (WaRSMP) on providing water resource managers with the most timely and accurate information for complex, interdisciplinary decisions using advanced decision support systems and relational data bases. Streamflow forecasts, and surface energy and water budgets are an integral part of the hydrology used in the decision process. These are needed on time scales from near real-time for flash floods and evaporation - crop consumptive use / water conservation needs, to days, weeks, months for daily operational decisions, and seasonal and interannual for annual operations plans, and up to decadal for long-range planning. Shifting demographics and climate variations create new challenges for integrated, multi-disciplinary decision support systems (DSS) that water managers and planners can apply to developing sustainable fresh water supplies for the West. These DSS integrate "the law of the river", riverine ecosystem and recreational needs with traditional irrigation, municipal and industrial uses, and hydropower generation, and economic trade-off analyses.

Reclamation cooperates with other agencies including: National Oceanic and Atmospheric Administration (NOAA), USGS, NRCS, and National Aeronautic and Space Administration (NASA), who collect, transmit, and analyze hydrometeorological information that we use in the Hydrologic Data Base (HDB) described by Matthews et al (1997, 1999, 2000). This paper will describe current and planned hydrometeorological needs, interdisciplinary modeling and decision support system tools and approaches used in major river basins served by Reclamation's facilities from Upper Columbia to the Rio Grande.