Water quality investigation of the county ditch 59-Cannon River Watershed, Le Sueur County, Minnesota

Nutrient input to a southern Minnesota hypereutrophic lake from the combined watershed of a second-order stream and an agricultural drainage ditch was monitored for a 14 month period, from July 1975 to September 1976. The stream-ditch watershed was divided into subwatersheds and the water quality of each was sampled approximately every seven to ten days during the ice free period and monthly during the ice cover period. Subwatershed flow rates were measured for each sample period and used to calculate subwatershed and total watershed nutrient loading. The overall water quality of the drainage ditch was found to excel that of the stream. In addition the flow rate in the stream was found to be 14 times that of the ditch. It was calculated that between 14 and 50 times the amount of nutrient loading of Nitrogen and Phosphorus respectively was contributed by the stream watershed as compared to that of the ditch.