COMPARISON OF 1990 AND 2020 WATER QUALITY DATA FOR THE GRAND RIVER, MICHIGAN

The Grand River, Michigan’s longest river, stretches 422 km from the headwaters to the mouth. The Grand River Watershed comprises 13% of the entire Lake Michigan Drainage Basin with a drainage area of 14,431 𝑘𝑚², the second largest drainage basin system in Michigan. The Grand River Expedition (GRE), launched by Verlen Kruger in 1990, documented water quality and highlighted recreational, economic, and environmental benefits of the Grand River. This once-in-a-decade public journey by canoe/kayak was planned to take place in July 2020, but was postponed due to COVID-19. Water quality sampling was completed using a modified sampling plan and methods with the following goals: 1) collect a complete, multi-parameter, water quality dataset; 2) compare collected data to other available datasets to evaluate water quality changes spatially and temporally; and 3) make data available to the public, policy makers, and river managers to raise awareness of water quality issues. Samples were taken at 1990 sampling locations and additional sites using an In-Situ Aqua TROLL 500 Multiparameter Sonde. Data was collected every two seconds, including: temperature, dissolved oxygen (DO), pH, salinity, conductivity, total dissolved solids (TDS), and oxidation reduction potential (ORP). Discrete water samples were also collected at each location and analyzed for E. coli, chloride, nitrate, ammonia, total phosphate, and orthophosphate. Preliminary comparison of 1990 and 2020 water quality data shows that DO and total phosphate concentrations remained essentially unchanged while pH, temperature, TDS, chloride, nitrate, ammonia and E. coli concentrations decreased. Average E. coli counts decreased from 1,583 to 101 CFUs. Some of the highest E. coli values were measured in tributaries (Cedar River, Crockery Creek, Deer Creek). Longitudinal changes in nitrate levels were similar to 1990 from the headwater to the mouth, however, average values decreased from 3.01 mg/L in 1990 to 0.75 in 2020. ArcMap Geographic Information System (GIS) will be used to analyze reaches with high spatial and temporal resolution data. Future sampling efforts should include additional sampling above and below tributaries to identify contributors to observed water quality changes and to evaluate hydrologic conditions.