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to substantial alteration of the Yampa River through Dinosaur National Monu- ment. This study was undertaken to determine the prevailing conditions of streamflow and sediment discharge through Deerlodge Park, and to estimate the effect of changes in hydrology or sediment supply on the sediment budget. The Yampa River drains approximately 8,000 mi2 in northwestern Colorado and south-central Wyoming, and is a major component of the upper Colorado River system (fig. 1). The Little Snake River, a principal tributary, drains approximately 3,730 mi2 and joins the Yampa River in Deerlodge Park. Mean-annual runoff from the Yampa River basin is approximately 1.5 million acre-ft/yr. Altitudes in the watershed range from 5,065 ft at the river's mouth to over 12,000 ft in the headwaters in the Park Range. Precipitation varies from less than 12 in./yr in the western part of the basin to over 60 in./yr at higher altitudes along the Continental Divide. Most of the precip- itation falls on the basin as snoW from November through April, although intense localized thunderstorms occur during the summer months. Tertiary and Cretaceous sandstones, mudstones, and shales underlie most of the basin (Tweto, 1979) and are the source of most of the material trans- ported by the Yampa River in its lower reaches. The Yampa River is entrenched into Permian and Pennsylvanian sandstones and limestones of the Uinta Mountain uplift for the last 45 mi of its course; little of the transported sediment is derived from these formations. Immediately upstream from the Yampa River Canyon is Deerlodge Park, a broad valley where the Little Snake River joins the Yampa River. The Yampa River Canyon was formed in the Uinta Mountain uplift (Hunt, 1969), and it lies within the boundaries of Dinosaur National Monument. Entering the canyon, the river gradient steepens and the channel is entrenched in bedrock. Riverbanks are predomi nant ly bedrock or talus materi a 1. Sand, gravel, and cobbles are found 1 oca lly in bars or along banks where the ri ver gradi ent 1 essens, or where the canyon width increases. Mobile sediments periodically are scoured from the bed and banks and redeposited as floodflows pass through the canyon. The canyon of the lower Yampa River in Dinosaur National Monument is a unique feature in the Western United States. With no major dams, and modest water consumption (approximately 10 percent of annual streamflow, Steele and others, 1979) , the Yampa River, in its lower reaches, retains a relatively pristine character. As such, the Yampa River in Dinosaur National Monument offers the visitor a rare opportunity to observe and study the biological and geomorphological setting of a relatively undisturbed river system. Annual streamflow in the Yampa River has been measured and sediment yields estimated for prevailing conditions; however, the effects of changes in either of these two variables previously have not been addressed. The objectives of this investigation are: 1. To establish the relation bet~een sediment discharge and water discharge for the Yampa River above the entrance to Yampa Canyon at Deerlodge Park. 2, To determine the mean annual hydrograph and flew-duration relation for the prevailing streamflow at Deerlodge Park. 3. To compute the mean annual sediment supply to the Deerlodge Park reach. 2