Water Resources Report for the Great Miami River Watershed
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2011-29 2011 WATER RESOURCES REPORT FOR THE GREAT MIAMI RIVER WATERSHED Summary This report summarizes the overall state of water resources in the Great Miami River Watershed for 2011, with an emphasis on the buried valley aquifer and water quantity and quality data. The Miami Conservancy District (MCD) operates and maintains an extensive hydrologic monitoring system. By tracking trends in precipitation, runoff, and groundwater levels, changes to the balance of the hydrologic system of the watershed are assessed. Water quality data also is collected in both surface and groundwater to track annual trends, establish a baseline for future studies, and verify nutrient reductions from landowner incentive programs. WATER QUANTITY The year 2011 was a record setting year with regards to annual precipitation. In 2011 MCD recorded record high annual precipitation within the Great Miami River Watershed. The 2011 mean annual precipitation was 58.89 inches, 19.84 inches above the long-term mean annual precipitation. The above normal precipitation contributed to above normal runoff in the Great Miami River and its tributary streams. The total annual runoff for the Great Miami River Watershed upstream of Hamilton was 29.83 inches, 16.61 inches above the long-term mean annual runoff. The year 2011 was an above normal year for groundwater storage in the Great Miami River buried valley aquifer system. The annual groundwater recharge to aquifers is estimated from stream gaging records for the Great Miami River Watershed. Groundwater recharge in 2011 was estimated to be 15.54 inches, 7.46 inches above the long-term mean annual groundwater recharge. The groundwater elevation levels measured in MCD observation wells reflect that the aquifers in the Great Miami River Watershed received most of their recharge in three major pulses occurring in late February/early March; late April/early May; and late November/early December. Groundwater levels in the major aquifers began the year at near normal levels, climbed to above normal levels, and finished the year at above normal levels. The water budget computed by MCD for the Great Miami River Watershed is a simple analysis using water inflows and outflows to the watershed. The computed 2011 water budget shows net water storage in the aquifers and soils of the watershed. Over the long term, the net water storage in the Great Miami River Watershed is near zero and water inflows and outflows are in balance. WATER QUALITY MCD collects data on nutrients in surface water to track annual trends, establish a baseline for future studies, and verify nutrient reductions from landowner incentive programs. In 2011, surface water quality continued to be impacted by excessive nitrogen and phosphorus levels. Nutrients are the primary pollutant issue in rivers and streams in Ohio (Ohio EPA, 2011). Excessive nutrients can lead to eutrophic conditions locally and contribute to the hypoxia problem in the Gulf of Mexico. Nutrients in the Great Miami River Watershed originate from both point and nonpoint sources. MCD collects data on emerging contaminant compounds which likely originated from private and municipal wastewater treatment systems. During 2011, data was collected on 21 emerging contaminant compounds in rivers, headwater streams, and the buried valley aquifer. Seventeen of the compounds were detected in one or more of the water samples. Analysis of surface water also reflects that the Great Miami River Watershed is impacted by fecal contaminants under all flow conditions and particularly during high flow events. Fecal indicator bacteria concentrations tend to be lowest during the summer and fall seasons when low flow conditions prevail. During 2011 groundwater samples were also collected to analyze the presence or absence of pollutants in the buried valley aquifer. The results show that water in the aquifer continues to be of high quality. Groundwater quality consistently meets nearly all the United States Environmental Protection Agency (U.S. EPA) standards for drinking water. However, arsenic was detected in three samples at concentrations above the drinking water maximum contaminant levels. Arsenic is thought to be naturally occurring and probably not indicative of a human source. BACKGROUND ..................................................................................................................................... 1 Great Miami River Watershed .................................................................................................... 1 Buried Valley Aquifer................................................................................................................. 1 MCD’s Water Resource Monitoring Program ............................................................................ 1 Hydrogeologic Setting ................................................................................................................ 4 WATER QUANTITY .............................................................................................................................. 7 A. The Water Cycle .................................................................................................................... 7 B. Precipitation Monitoring ........................................................................................................ 7 2011 DATA ............................................................................................................................................. 9 2011 Precipitation in the Great Miami River Watershed ........................................................ 9 C. Monitoring Runoff, Streamflow, and Groundwater Recharge ............................................. 11 2011 Runoff in the Great Miami River Watershed ............................................................... 13 How Runoff is Computed ..................................................................................................... 13 Surface Runoff ...................................................................................................................... 13 Base Flow.............................................................................................................................. 14 Trends in Annual Runoff ...................................................................................................... 14 2011 Flow in the Great Miami River at Hamilton ................................................................ 15 2011 Groundwater Recharge in the Great Miami River Watershed ..................................... 17 How Groundwater Recharge is Estimated ............................................................................ 17 D. Monitoring Aquifer Storage ................................................................................................. 19 2011 Groundwater Levels ..................................................................................................... 19 2011 Groundwater Storage ................................................................................................... 21 2011 Estimated Water Budget for the Great Miami River Watershed ................................. 22 2011 Water Quantity Summary ............................................................................................ 25 WATER QUALITY ............................................................................................................................... 27 A. Nutrients ............................................................................................................................... 27 Nutrient Criteria .................................................................................................................... 27 Nitrogen ................................................................................................................................ 28 Phosphorus ............................................................................................................................ 28 Annual Nutrient Loads .......................................................................................................... 28 Annual Nutrient Yields ......................................................................................................... 30 B. Emerging Contaminants ....................................................................................................... 32 C. Microbial Source Tracking of Fecal Contaminants ............................................................. 34 D. Groundwater Quality Assessment ........................................................................................ 36 E. Exceedances of National Drinking Water Standards ........................................................... 38 F. Major Ions ............................................................................................................................. 38 G. Nutrients ............................................................................................................................... 39 H. Trace Metals ......................................................................................................................... 39 I. Semi-volatile Organic Compounds (SVOCs) ....................................................................... 39 J. Volatile Organic Compounds (VOCs) .................................................................................. 39 SUMMARY AND CONCLUSIONS .................................................................................................... 40 REFERENCES......................................................................................................................................