The U.S. Geological Survey began a study in 2003 in cooperation with the Tennessee Duck River Development Agency to assess the hydrology of the Duck River watershed from Normandy Dam downstream to Columbia, Tennessee. Ground-water-level data, spring-flow, bacteria samples, and streamflow were collected during this study to characterize the hydrology of the study area. The emphasis of this study was to characterize the temporal and spatial variability of the various components that make up streamflow in the Duck River in this study area. Water-level data from wells in the study area indicate a good hydraulic connection between the aquifer and the river, with little long-term storage of water following recharge events. Variations in spring flow and ground-water temperature at springs indicate that a large component of water issuing from springs has a short residence time in the aquifer for most of the springs monitored in the study area. Escherichia coli densities in samples collected from springs are similar to concentrations in samples from tributaries and the Duck River. Base-flow synoptic discharge measurements, flow-duration analysis of tributary streams, and streamflow accounting analysis indicate the portion of the watershed between Pottsville and Columbia yields more water than the portion between Shelbyville and Pottsville. Base-flow synoptic measurements show that Fountain Creek yields more water than other tributary basins in the study area, whereas base-flow synoptic measurements on the mainstem indicate that streamflow in the Duck River between Pottsville and Columbia could vary by 10 percent as the result of gaining and losing reaches. These results are applicable for average flow conditions that occurred during the study. Flow-duration analysis indicates that tributaries in this part of the watershed have a large component of ground-water contributing base flow. Streamflow accounting analysis for two periods of extended recession was used to determine the contributions of flow releases from Normandy Dam, tributaries, wastewater discharges, and ground-water discharge. The analysis indicated this same section of the mainstem of the Duck River between Pottsville and Columbia had as much as four times more ground-water discharge as sections upstream from Pottsville.