The purpose of this study was to determine the hydrologic characteristics of Alder Creek, Iron County, Wisconsin, which are needed by water-resource planners to evaluate a reservoir site proposed by the Whitecap Mountain Corporation on Alder Creek. The hydrologic characteristics estimated were the mean flows, low flows, flood peaks, suspended-sediment discharge, and depth to bedrock. Also included is an estimate of the time required to fill the proposed reservoir. The study was done in cooperation with the Wisconsin Department of Natural Resources.