We measured stream and lake water quality during summer 2002, to describe spatial and temporal patterns and identify potential "hot-spots" of low water quality. From 17 selected locations in the lake and surrounding watershed streams, we collected water samples and measured pH, conductivity, temperature, dissolved oxygen, nitrate+nitrite, ammonium and soluble reactive phosphorus.
High nutrient concentrations in streams were more typically found from developed sub-watersheds occupied by the college and surrounding community (residences and small shopping centers). Stream pH and conductivity both decreased after rainstorms, whereas stream oxygen content increased. Water delivered to Lake Matoaka was elevated in total dissolved nutrient concentration, yet the concentrations of nutrients in the lake itself were very low. Phosphate concentration in one stream, for example, averaged over 3 µM over the summer; from 6 locations in the lake, however, the concentration was never above 0.1 µM. Much of the nutrient load went into algal production in the lake, as secchi readings decreased to less than 0.5 m by the end of summer.
Lake Matoaka appears to function as an efficient water detention basin for the surrounding community, since high nutrient loads are retained in the lake as algal biomass. Much of the lake volume, however, is anoxic. Watershed-driven eutrophication Lake Matoaka may decrease its function as habitat for fish, shellfish and other aquatic species.
For additional documentation Bonnie Ludlow and Tim Wygant provided a Powerpoint Presentation entitled, "Water Quality in Lake Matoaka and the Surrounding Watershed," provided here in PDF form.