TRANSPARENCY AS AN INDICATOR OF WATER QUALITY IN GARVIN BROOK, SOUTHEASTERN MINNESOTA

Garvin Brook, a state-designated trout stream near Stockton, Minnesota, has been listed as an impaired stream for fecal coliform bacteria and turbidity. The stream has a drainage area of 30,720 acres and 65% of the land in the watershed is used for agricultural purposes. In the 1980's, the Garvin Brook Rural Clean Water Project (GBRCW), composed of nearby landowners and governmental agencies, developed an extensive plan to maintain water quality in the watershed. The GBRCW focused on nutrient management and ground water quality. Currently, the state of Minnesota has implemented a stream monitoring program that employs stream transparency as an indicator of overall water quality. We took transparency measurements over a 10 month period in 2005 and compared them to other physicochemical stream parameters. The monitoring program included three different sampling sites along Garvin Brook. Transparency measurements accurately indicated the overall water quality of the stream during baseflow and bankfull conditions. High transparency readings indicated low levels of orthophosphate, nitrate, fecal coliform, and biological oxygen demand. These results show that transparency is a good indicator of ecosystem health and is suitably applied to stream monitoring programs. Additionally, we compared our results with those of the GBRCW Project. Our 2005 data shows increases in overall water quality and a decrease in turbidity over the 1989 GBRCW data.