The U.S. Environmental Protection Agency (US EPA) is developing e-Estuary, a decision-support system for coastal management. E-Estuary has three elements: an estuarine geo-referenced relational database, associated estuarine and watershed GIS coverages, and tools to support decision-making. A population of 300 estuaries with associated watersheds at the HUC-10 scale (16-100 ha) or larger within the conterminous U.S. has been identified for characterization of estuarine geomorphology, tidal and hydrologic regime, and land-use/land-cover of associated watersheds. Historic estuarine water-quality data from Federal and State agencies and local estuarine management groups have been integrated within a geodatabase structure consistent with the WQ-X schema established by US EPA for XML-based data transfer between reporting units and national databases. An ArcHydro-based geodatabase structure is being created to facilitate merger of national hydrographic databases (NHD-Plus) with emerging Coastal data models (ACES), to provide linkages with web services for delivery of time series data, and to provide linkages between monitoring data and modeling applications. Tools and associated datasets under development include: 1) nationwide classification schemes to reduce variance in nutrient-response relationships, 2) regional regression relationships to normalize total organic carbon in sediments to sediment grain-size in order to support diagnosis of eutrophication, 3) estuary-scale segmentation and parameterization of simple tidal prism models to refine loading targets, and 4) habitat zonation schemes to help refine aquatic life designated uses. The e-Estuary Project supports President Obama's call for transparency and open access to governmental data (re-affirmed in Administrator Jackson's January 23, 2009 memo), providing easy access to data from multiple Federal agencies in support of the Clean Water Act.