Analysis of seepage measurements in the Alder Creek basin, Stevens County, Wash., shows that approximately 50% of 0.2 cubic foot per second taken from an unnamed tributary and used for the 1978 irrigation season would have reached Alder Creek as surface flow. Differences in discharge and specific conductance are explained by the basin geology, physical characteristics, climate, and water use. Only general conclusions could be made from data collected for five seepage measurements because irrigation activities could not be scheduled to allow the hydrologic system to reach equilibrium. (USGS)