A study of runoff to selected lakes was done in the Twin Cities metropolitan area from July 1981 to December 1982. The purpose of the study was to determine differences in nutrient-loading characteristics for lakes with and without wetlands and settling ponds. The study also quantified nutrient loading to lakes on a storm, seasonal, and annual basis, complementing an inlake water-quality study of these lakes done by the Metropolitan Council.
Discharge and water-quality data were collected periodically during 1981 and continuously during 1982 at 22 sites located in seven lake watersheds Bryant Lake, Lake Elmo, Fish Lake, Lake George, Lake Riley, Spring Lake, and Square Lake. Basin characteristics and land use were determined for each watershed. Recording instruments provided continuous discharge records at 14 sites and continuous rainfall records at six sites. Automatic water-quality samplers were used at lake inlets. The automatic samplers collected samples at 1- to 2-hour intervals during storms. Lake-outlet samples were collected manually on a weekly basis during flow. Samples were analyzed for suspended solids and nutrients. Atmospheric-input data were collected at eight sites from September 23 to November 1, 1982. Discharge and water-quality data were used to calculate storm, seasonal, and annual loads of total suspended solids, volatile suspended solids, total phosphorus, dissolved phosphorus, nitrite-plus-nitrate nitrogen, ammonia nitrogen, and ammonia-plus-organic nitrogen.
All data collected during the study are documented in tables and graphs that contain (1) watershed characteristics and land use; (2) storm concentrations; (3) storm, seasonal, and annual loads; (4) storm hydrographs; (5) atmospheric-input concentrations and loads; (6) storm, seasonal, and annual precipitation totals; and (7) results of quality-assurance tests.
