Water-quality and streamflow data were collected in the Coteau des Prairies region of southwestern Minnesota and eastern South Dakota from 1979- 84. Data were collected to (1) document the water-quality characteristics of streams and impoundments in the Coteau area, (2) predict the impact of proposed impoundments, (3) define the amount of dissolved and suspended material transported, and (4) determine the differences in water quality between the impoundment inflows and outflows.

Streamflow and water-quality data were collected at 12 stream and four impoundment sites. Continuous-record gages, set to collect data at 15-minute intervals, and readings taken by local observers were used to complete discharge records at 10 stream sites and stage records at three impoundment sites. Automatic samplers and local observers collected storm runoff, sediment, and nutrient samples at 10 stream sites. Water-quality samples were collected at various time and stage intervals during high flow and periodically during low flow. Primary emphasis in the stream-sampling program was on analysis of samples for nutrients in 1980-82, and on analysis of suspended sediment and nutrients in 1983-84. Field measurements were made of pH, water temperature, dissolved oxygen, specific conductance, alkalinity, and bacteria. Secondary emphasis was on analysis of major dissolved substances. Primary emphasis in the impoundments was on analysis of samples for phosphorus and chlorophyll and on the measurement of transparency. Temperature and dissolved-oxygen concentrations were measured to determine the degree of stratification.

All data collected during the study are given in tables 4-13 of this report. The tables list mean-daily stream discharge, mean-daily suspendedsediment concentration, daily suspended-sediment discharge, results of waterquality analyses, and bed-material particle-size analyses at stream sites. The tables also list information on pool stage, water temperature, and transparency, on dissolved-oxygen, chlorophyll a, phytoplankton, and nutrient concentrations, and on chemical and partical-size analyses of bed material at impoundment sites.