Groundwater inflow to the Deschutes River near the Warm Springs Indian Reservation in Oregon was estimated for August 1985 by: (1) measuring streamflow at various sites along the river; (2) determining the part of the streamflow that is groundwater inflow; and (3) analyzing the hydraulic gradients of the groundwater flow system to estimate the amount of groundwater discharge to the Deschutes River from both sides of the river. Results of the streamflow analysis indicated that the Deschutes River gained 415 cu ft/sec between Round Butte Dam and Dant in August 1985. Results of the analysis on hydraulic gradients of the groundwater flow system showed that the amount of groundwater inflow from the west side ranged from about 207 to 216 cu ft/sec, and groundwater inflow from the east side ranged from about 199 to 207 cu ft/sec. Streamflow measurements in September 1985 along the Metolius River from the site above Jefferson creek to the site below Camp Creek indicated a gain of 70 cu ft/sec. From the site below Camp Creek to the gage above Lake Billy Chinook the results of discharge measurements showed a loss of 112 cu ft/sec. Because of lack of groundwater hydraulic-head and lithologic data, no analysis of the groundwater flow system near the Metolius River was attempted. (USGS)