COMPARING HYDROLOGIC CHARACTERISTICS BETWEEN URBAN LAKES AND STREAMS IN A SMALL WATERSHED IN NORTHEAST IOWA

This sampling project occurred in the Cedar River Watershed and comprised of 5 sites on Dry Run Creek (15,177 acres), 3 on small lakes and 2 on the Cedar River. Samples were taken a week apart over 10 weeks. Measurements included: pH, total dissolved solids (TDS), turbidity, dissolved oxygen (DO), biochemical oxygen demand (BOD), temperature, conductivity, nitrate, chloride, phosphate, e. coli, and sulfate. Data were compiled into graphs to show spatial and temporal variations in water quality index (WQI). Used variables are sample date, site, temperature, D.O., T.D.S., turbidity, E. coli. and B.O.D. Making a distinction between stream sites and lake sites a few key points of data follow. An average stream TDS of 390.9 mg/L was recorded. On the other hand, an average lake TDS of 298.9 mg/L was recorded. The average stream and lake E coli were 105.9 colonies/100 mL and 11.1 colonies/100 mL. A marked difference must be noted between the average E coli values of lakes and streams as this is the single greatest spread in the data. An average stream turbidity of 14.1 and an average lake turbidity of 17.5 were recorded. The higher turbidity in lakes is attributed to the algae blooms at Prairie Lake. The range of stream WQI values was between 78 and 53. The range of lake WQI values was between 77 and 60. Notable trends include significantly lower WQI values at Site 9 (S9), which is due to its location at the confluence of the Dry Run Creek and the Cedar River. The higher average WQI values at Site 1 (S1) is attributed to its location further upstream and nearer the edge of an urban area, thus receiving less urban runoff. Furthermore, overall higher average WQI (5.6 points) was found at lake sites (69.8 points) compared to stream sites (64.2 points), which is attributed to smaller drainage basins and greater settling of sediment in standing bodies of water.