The regulation of water use has and continues to be the province of the states. However, the flow of water, whether in surface water bodies or under ground, does not respect political boundaries. Water flows freely across state and local borders. As a result, certain states have banded together, in some cases with the federal government, and formed interstate compacts to regulate water use. Examples include the 1961 Delaware River Basin Commission in Pennsylvania and the 1922 Colorado River Compact in the west. There are many others throughout the United States. While each compact has its own history and purpose, all share the common goal of attempting to meaningfully regulate water use across state boundaries. Focusing on the Delaware River Basin Commission, this session will provide an overview of the jurisdiction, activities and accomplishments of one of the most successful interstate water compacts and will provide useful insights into the critical role played by interstate regulation of water use.