Dinosaur National Monument, in northwestern Colorado, has become a test case in the establishment of a federal reserved water right to instream flows. For the first time, the Interior Department was forced to rigorously defend its claims in a watershed where the federal government did not control the upstream reaches. Inadequate quantification of minimum flow requirements, court orders, and an apparent Congressional ban on the spending of Water Resources Program funds by the Park Service to quantify its water rights have already placed the Service in a difficult position to protect instream flows for maintaining the ecological integrity of the Monument. As late as 1983, administrators of the Park Service were divided over their legal [...]