Figure 1. Average monthly precipitation (in inches) in Mercer County, Ohio (1957-1993); data collected at Celina.
E. Joseph Beiler
Mercer County
Water is a resource often taken for granted. In recent years, water availability and quality have become important public concerns in Mercer County. The county's population of 39,443 (1990 census data) is predominantly rural, and about 76 percent of all households rely on ground water for their water supply. This fact sheet provides a brief overview of Mercer County's water resources, and is intended to help increase public awareness and understanding about this vital resource. By understanding where water is obtained and how it is used in the county, residents can gain a better appreciation for their water supply. The water resources terminology used in this publication is included in Surface and Ground Water Terminology, Fact Sheet AEX 460, which provides a listing of generally accepted water resource definitions. Ohio State University Extension publications are available through all Ohio county Extension offices.
An average of approximately 35 inches of precipitation falls on Mercer County annually. Figure 1 illustrates the average monthly precipitation for the county for the period 1957 to 1993. Based on this 37-year record, the average precipitation is 3 inches per month, with February (2 inches) typically being the driest month, and July (4.1 inches) the wettest. However, there can be extreme variations in some years and in certain months within a year. Such seasonal and yearly extremes may have serious consequences and are not always apparent from the long-term precipitation information.
Figure 1. Average monthly precipitation (in inches) in Mercer County,
Ohio (1957-1993); data collected at Celina.
Mercer County is split by a major watershed divide. The north half of the county is drained by the St. Marys River which flows north to the Maumee River at Ft. Wayne, Indiana, then to Lake Erie. The northeast corner of Union Township by the Little Auglaize drains into the Maumee River. The south part of the county is drained by the Wabash River which joins the Ohio River at the Indiana/Illinois border, and the southeast corner of Marion Township is drained by the Miami River basin. A generalized surface water map of Mercer County is given in Figure 2.
Surface waters are affected by the soil type and topography of the land adjacent to them, and the way humans use the land. Land use, such as residential development, construction, and agricultural production, can affect the amount of sediment entering a body of water. The type of soils in an area also influences water runoff because of the soil's infiltration and water holding characteristics. With some soils, rainfall is more likely to run off, while other soils allow water to infiltrate more readily.
The county contains approximately 284,160 land acres, of which 81 percent is farmland. Seven soil types have been identified in the county and vary in drainage ability from very poorly drained to somewhat poorly drained with only a small percent of the soils listed as moderately well drained. The moderately drained soils are the Glynwood soils which make up about 11 percent of the land area. Most of the county water acreage can be attributed to Grand Lake St. Marys which contains about 14,500 acres; two-thirds of this lake are in Mercer County. There are two dams on the Wabash River that can hold up to 34 surface acres of water except they are dry most of the year. Many small private ponds also exist throughout the county. Mercer County contains approximately 297 linear miles of major streams and rivers [estimated from river basin maps, Ohio Department of Natural Resources (ODNR) Division of Water]. In addition, 62 miles of county maintained ditches and numerous miles of private maintained ditches are used for land drainage. This availability lends itself to many uses by both communities and individuals.
Figure 2. Surface-water resources in Mercer County, Ohio (adapted
from ODNR Division of Water river basin maps; illustration prepared
by H. Landfried).
Mercer County's primary ground-water source is the carbonate aquifer composed of limestone and dolomite bedrock. Limestone is composed of calcium carbonate, while dolomite is composed of calcium-magnesium carbonate. Together they form a popular construction material that most Ohioans refer to as limestone.
The carbonate aquifer is the primary and most productive aquifer in Mercer County. Yields of 400 gallons per minute (gpm) may be developed from wells encountering various solution fractures or cavities in the bedrock. Farm and domestic supplies of 20 to 40 gpm may be developed at depths of less than 150 feet. The bedrock is covered with 20 to 100 feet of glacial till consisting of thick clay, sandy clay and thin lenses of sand and gravel. Hydrogen sulfide (H2S) is often encountered in the bedrock.
Deep sand and gravel lenses in the ancestral Teays Valley are underlain by impermeable Ordovician shale. Sand and gravel lenses may yield over 25 gpm to screened wells often providing artesian supplies. These buried valleys are remnants of old streams which had cut their courses deep into the bedrock before the area was glaciated. Later with the coming of the glaciers the valleys were completely filled with sediment. The buried valleys and the valley margin area contain some extensive sand and gravel deposits which, in some locations, may supply as much as 100 gpm. Throughout most of the basin adequate farm and domestic supplies are available from the sediment, which averages 65 feet in thickness. An overview of the ground-water resources in the county is given in Mercer County Ground-Water Resources, AEX-490.54.
The yield of a well will vary considerably depending on the age and depth of the well, well construction, the diameter of the casing, pump capacity and age, and more importantly, properties of the geologic formation. Specific information on ground-water availability and wells can be obtained by contacting ODNR Division of Water.
Based on long-term weather records, Ohio receives an average of 38 inches of precipitation per year. These 38 inches move through a complex path called the hydrologic cycle. Of these 38 inches, about 10 inches (26 percent) become runoff, which moves immediately to surface-water bodies such as streams and lakes. Two inches are retained at the ground surface and evaporate back into the atmosphere in a relatively short period of time. Twenty-six of the 38 total inches enter the soil surface through infiltration. Twenty of these 26 inches go into soil storage and later are returned to the atmosphere by the combination of evaporation and transpiration (evapotranspiration). The remaining 6 inches of precipitation (16 percent of the total) have the potential to recharge the ground-water supply. Two of these 6 inches eventually move to springs, lakes, or streams as ground-water discharge. The remaining 4 inches either return to the atmosphere by evapotranspiration or are withdrawn to supply water needs. For further reading, refer to Ohio's Hydrologic Cycle, AEX 461.
Statewide averages applied to the county's average annual precipitation, provide a rough estimate of how many inches will result in runoff and how many inches have the potential to reach aquifers. Based on statewide averages of runoff and ground-water recharge, Mercer County's 36 inches of average annual precipitation result in about 9.4 inches of runoff to streams and lakes, and about 5.8 inches have the potential to recharge aquifers annually. Values for particular locations will differ according to local conditions.
Water use for each of Mercer County's public water-supply systems is given in Table 1. For each system, this table presents an estimate of the population served, water source, estimated daily usage, and treatment plant capacity. The county's largest public-water system is Celina, which uses Grand Lake St. Marys for its supply. All other systems in Mercer County use wells.
Ground water is a major water source for rural households in Mercer County. Approximately 49 percent of all households obtain their water from private wells. Based on an estimated usage of 75 gallons per person per day, 1,436,250 gallons per day (gpd) from private wells are used. Additional private water uses include industry (10,2000 gpd, although three wells cannot be accounted for in this figure), and livestock use (2 million gpd) mostly from ground-water supplies. The remaining 51 percent of households use public-water supplies with ground water as the major source, as identified in Table 1.
Some water users in Ohio must register their withdrawals with the ODNR Division of Water. Through the Water Withdrawal Facility Registration Program, owners of facilities capable of withdrawing 100,000 gpd (70 gpm) or more must register those facilities. Information collected through this program includes withdrawal capacity, ground- or surface-water sources, location and type of water use, and location of discharge points. The program is for registration only, and not for allocation or permission. Registered withdrawers file annual reports of their water use. This information helps planners at ODNR to determine the availability of water for projected needs, and to better manage and protect Ohio's water resources. Documenting water use also provides official records for individual uses. For more information, contact ODNR Division of Water.
Natural processes and human activities affect the quality of our water supplies. Throughout Ohio, human activities contribute to both point and nonpoint source pollution. Point source pollution is the introduction of impurities into a water supply source (ground water or surface water) from an identifiable, known location. Examples of point sources can include industrial plants, power plants, commercial businesses, and wastewater treatment facilities.
Nonpoint source pollution also involves the introduction of impurities into a surface-water body or an aquifer, except the route is usually non-direct and the sources are "diffuse" in nature. A major portion of the sediment, nutrients, acids and salts, heavy metals, toxic chemicals, and pathogens enter the state's water resources through nonpoint source pollution, affecting both ground and surface water. Examples include automobile emissions, runoff from parking lots, and runoff and drainage from agricultural fields, feedlots, home lawns and gardens, residential development, construction, mining, and logging activities.
As water moves through the aquifers underlying Mercer County, it dissolves the minerals contained in the formations and carries them in solution. Publication AEX-490.54 summarizes some of the county's natural ground-water quality aspects.
Human activities, such as agricultural production, domestic waste disposal, and lawn and turf care, may have some influence on the county's ground-water quality. In a 1987 study by Heidelberg College, 101 wells in the county were sampled for nitrate-nitrogen content, of which 96 (95 percent of total) contained nitrate-nitrogen concentrations in the range of 0 to 0.3 parts-per-million (ppm). This range is assumed to represent natural background levels.
Four wells (3.9 percent) tested in the 0.3 to 3.0 ppm range; these values may or may not indicate human influence. One well tested in the range of 3.0 to 10 ppm, and may indicate elevated concentrations resulting from human activities. None of the wells tested over 10 ppm for nitrate-nitrogen, an amount that exceeds the safe drinking-water standard. The average test value for the 101 wells sampled was 0.11 ppm.
Design, location, and condition of a well, combined with the characteristics of the soils and geologic formations in which the well is constructed, influence the potential for pollutants to enter the well. Bacterial counts are another indicator of ground-water quality. The Mercer County Department of Health tests water samples for concerned citizens, and results of these tests generally indicate safe drinking water in the county.
| Table 1. Water Use in Mercer County, Ohio.1 | ||||
|---|---|---|---|---|
| Public Water System | Population Served | Primary Water Source | Water Usage (GPD)2 | Treatment Plant Capacity (GPD) |
| Celina | 9,650 | Surface & Ground3 | 1,005,000 | 2,281,000 |
| Coldwater | 4,335 | Ground Water | 694,000 | 1,100,000 |
| Ft. Recovery | 1,386 | Ground Water | 86,000 | 369,000 |
| Mendon | 717 | Ground Water | 85,000 | 166,000 |
| Rockford | 1,190 | Ground Water | 152,000 | 288,000 |
| St. Henry | 1,910 | Ground Water | 405,000 | 893,000 |
| Other4 | 1,038 | Ground Water | 101,670 | NA |
| 1 Estimates from Ohio EPA using adjusted 1993 data; information is based on data available at time of publication. | ||||
| 2 GPD = gallons per day. | ||||
| 3 Supplied by Grand Lake St. Marys. | ||||
| 4 Includes mobile home parks, county homes, nursing homes, homeowners associations and the St. Charles Seminary, total plant capacity figure not available. | ||||
Runoff and sediment from residential development, construction sites and agricultural lands may enter the county's streams and lakes. Also, runoff may carry other pollutants, such as lawn and agricultural chemicals (pesticides and fertilizers), effluent from septic systems, oil and gas from spills, and industrial wastes.
Through the Ohio Nonpoint Source Assessment and Water Resources Inventory, the Ohio Environmental Protection Agency (Ohio EPA) and ODNR have identified 13,000 stream miles in Ohio that have been affected by nonpoint source pollution. Mercer County contains portions of several streams and their tributaries that have been classified by the Assessment as being affected by nonpoint source pollution. Based on the findings of the Assessment and Inventory, the Ohio Nonpoint Source Management Plan has been implemented to help improve the quality of the state's waters. For specific information about the streams and tributaries listed in the Assessment and details of the Management Plan for the county, contact the Ohio EPA Northwest District Office (347 N. Dunbridge Rd., Bowling Green, OH 43404).
Overall, Mercer County has a safe supply of water. County citizens have a major challenge to protect water resources from pollutants that could affect the quality of the water supply. For more information about nonpoint source pollution, refer to Nonpoint Source Pollution: Water Primer, AEX 465, available from your county Extension office.
Water availability and quality are important public concerns. Water problems can be both costly and inconvenient. While the present and future availability of water is good for Mercer County, water is a precious resource that must be conserved and protected. We must all work together to maintain an adequate supply of good quality water.
This fact sheet provides information about the water resources in Mercer County. For more information concerning water resources or drinking-water quality in the county, contact the Mercer County office of Ohio State University Extension (321 Riley St., Celina, OH 45822). In addition, the following agencies may be able to provide information on other water resources topics in the county: Mercer Soil and Water Conservation District; Mercer County Health Department; ODNR Division of Water (Fountain Square, Columbus, OH 43224); US Geological Survey (USGS), Ohio District (975 W. Third Ave., Columbus, OH 43212); Ohio EPA (1800 WaterMark Dr., Columbus, OH 43215-1099); and Ohio Department of Health (ODH; P.O. Box 118, Columbus, OH 43226).
Doane's Agricultural Report. 1992. Farm Water Systems.
Estimated Water Use in Ohio, 1990, Public Supply Data. 1993. USGS Open-File Report 93-72.
Gazetteer of Ohio Streams. 1960. Ohio Water Inventory Report No. 12. ODNR Div. of Water.
Ground-Water Resources of Mercer County. 1982. R. J. Kostelnick. ODNR Div. of Water. (map).
Hydrologic Atlas for Ohio: Average Annual Precipitation, Temperature, Streamflow, and Water Loss for the 50-Year Period 1931-1980. 1991. L. J. Hartstine. Water Inventory Report No. 28. ODNR Div. of Water.
Inventory of Municipal Water-Supply Systems by County, Ohio. 1977. Ohio Water Inventory Report No. 24. ODNR Div. of Water.
Inventory of Ohio's Lakes. 1980. Ohio Water Inventory Report No. 26. ODNR Div. of Water.
Mercer County Ground-Water Resources. 1994. E. J. Beiler, J. M. Raab, L. C. Brown, and K. T. Ricker. AEX-490.54. Ohio State University Extension.
Mercer County, Ohio Soil Survey. 1979. USDA-SCS. Mercer Soil and Water Conservation District Resources Inventory. 1986. USDA-SCS.
Monthly Station Normals of Temperature, Precipitation, and Heating and Cooling Degree Days, 1961-90, Ohio. 1992. Climatology of the United States, No. 81 (by state). NOAA.
Nitrate and Pesticides in Private Wells of Ohio: A State Atlas. 1989. Water Quality Laboratory, Heidelberg College.
Nitrate In Drinking Water. 1987. K. M. Mancl. Bulletin No. 744. Ohio State University Extension.
Non-Point Source Pollution: Water Primer. 1993. R. Leeds, L. C. Brown. AEX 465. Ohio State University Extension.
Ohio Ground-Water Quality. USGS National Water Summary-Ohio. 1986. USGS Water-Supply Paper 2325.
Ohio Ground-Water Resources. USGS National Water Summary-Ohio. 1984. USGS Water-Supply Paper 2275.
Ohio Nonpoint Source Management Program. 1993. ODNR.
Ohio Population by Governmental Unit. 1991. Ohio Data Users Center, Ohio Department of Development.
Ohio Surface-Water Resources. USGS National Water Summary-Ohio. 1985. USGS Water-Supply Paper 2300.
Ohio Water Firsts. 1985. S. L. Frost and W. S. Nichols. Water Resources Foundation of Ohio, Inc.
Ohio Water Resource Inventory: Executive Summary and Volumes 1-4. 1992. Ohio EPA.
Ohio's Hydrologic Cycle. 1990. L. C. Brown and K. M. Coltman. AEX 461. Ohio State University Extension.
Private Water Systems Handbook. 1987. MWPS-14. Midwest Plan Service, Ames, IA.
Southwest Ohio Water Plan. 1976. ODNR Div. of Water.
State of Ohio Nonpoint Source Assessment: Volumes 1-6. 1990. Ohio EPA.
Surface and Ground Water Terminology. 1990. L. C. Brown and L. P. Black. AEX 460. Ohio State University Extension.
Water-Ohio's Remarkable Resource. 1982. ODNR Div. of Water.
Withdrawal and Distribution of Water By Public Water Supplies in Ohio, 1985. 1989. USGS Open-File Report 89-423.
This publication was produced through the Ohio Water Resources Education Project, in cooperation with: ODNR Division of Water; Ohio EPA; USGS, Ohio District; and ODH. Project leaders are Larry C. Brown and Karen T. Ricker. Partial financial support for this publication was provided by these cooperating agencies and programs: Mercer County office of OSU Extension; Mercer County Commissioners; Mercer Soil and Water Conservation District; Overholt Drainage Education and Research Program; and the Ohio Management Systems Evaluation Area Project (USDA Extension Service Grant No. 90-EWQI-1-9018).
The project leaders express appreciation to the following reviewers: Ken Strickland (Wright State University-Lake Campus); Jim Will (USDA Soil Conservation Service, Mercer County); Harold Howick (Celina Weather Station); James M. Raab, David Cashell and Leonard Black (ODNR Division of Water); Scott Golden (Environmental Health, ODH); Steve Hindall (USGS, Ohio District); Robert Burris (USDA Soil Conservation Service, State Office, Columbus); Jay Fleming (Ohio EPA Division of Drinking and Ground Waters); and Larry Antosch (Ohio EPA Division of Surface Water).
A special thanks to Peg Wiehe (Mercer County Extension Office) for assistance in research and fact sheet preparation; and Kurt E. Bullock and Kim Wintringham, Associate Editors (Section of Communications and Technology, Ohio State University Extension), for editorial and graphic production.
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-1868