Figure 1. Average monthly precipitation (in inches) in Delaware County, Ohio (1961-1990).
K. Troy Putnam
Kristina M. Boone
Larry C. Brown
Water is a resource often taken for granted. In recent years, water availability and quality have become important public concerns in Delaware County. The county is a mix of urban and rural cultures with a population of 66,929 (1990 census data), and about 71 percent of all households rely on surface water for their water supply. By understanding where water is obtained and how it is used in the county, residents can gain a better appreciation for their water as the important resource it is. Providing a brief overview of Delaware County's water resources, such as rivers, streams, ponds, reservoirs and ground water, this fact sheet is intended to increase public awareness and understanding of water resources. 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. OSU Extension publications are available from all county Extension offices.
An average of approximately 36 inches of precipitation falls on Delaware County annually. Figure 1 illustrates the average monthly precipitation for the county for the period 1951-1980. Based on this 30-year record, the average precipitation is about 3.0 inches per month. February and October are typically the driest months with 2.0 inches, and July is historically the wettest with an average 4.0 inches of rainfall. There can be, however, extreme variations in some years and in certain months within a year. Such seasonal and yearly extremes, which may have serious consequences, often are not apparent from the long-term precipitation information.
Figure 1. Average monthly precipitation (in inches) in Delaware
County, Ohio (1961-1990).
Delaware County has three major drainage basins: Big Walnut Creek, Olentangy River and Scioto River. Alum Creek is part of the Big Walnut Creek basin. Major feeder streams that drain various parts of the county include: Rattlesnake Creek, Culver Creek, Sugar Creek, Little Walnut Creek, Whetstone Creek, Delaware Run, Indian Run, Horseshoe Run, Mill Creek, Bokes Creek and Fulton Creek. All of these drainage basins are important because they are tributaries to the Ohio River, which is a major water resource for southeastern and southern Ohio, and other states. A generalized surface-water map of the county is given in Figure 2.
The Big Walnut Creek basin drains approximately 557 square miles and stretches from near Mt. Gilead to south of I-270 near Shadeville, where it joins the Scioto River. The Hoover Reservoir, located on the Big Walnut in southeastern Delaware County, covers 3,300 surface acres, of which approximately 2,640 acres are located in the county, with the remaining in Franklin County. Alum Creek Lake, a part of the Big Walnut Creek basin, was completed in 1974 and covers 3,387 surface acres. Alum Creek empties into the Big Walnut north of Groveport on the southeast side of Columbus.
The Olentangy River basin covers approximately 536 square miles, starting southwest of Galion and running through southern Crawford County, eastern Marion County, and into Delaware County where it feeds into the 1,300-acre Delaware Lake. After passing the Delaware Dam, the Olentangy runs to Columbus, where it enters the Scioto River.
The Scioto River basin contains approximately 6,510 square miles of drainage, all in Ohio. It begins just north of Indian Lake in Auglaize County, and empties into the Ohio River at Portsmouth, in Scioto County. In Delaware County, the 920-acre O'Shaughnessy Reservoir is fed by the Scioto.
Delaware County contains approximately 293,760 land acres, of which approximately 182,000 acres are farmland. Eighty-six different soil mapping units are present within the county, the majority of which are somewhat poorly-drained and poorly-drained soils formed in fine textured, slowly permeable, calcareous glacial till. The county contains approximately 8,460 acres of reservoirs and lakes, and about 315 linear miles of stream and rivers (estimated from river basin maps, ODNR Division of Water). More than 800 ponds, ranging from 1/4- to 1/2-acre or larger in size, also are found in Delaware County. Most are filled by precipitation and runoff.
Figure 2. Surface-water resources in Delaware County, Ohio
(adapted from ODNR Division of Water river basin maps).
In Delaware County, four different types of aquifer systems are present. Thin lenses of sand and gravel interbedded in thick layers of clay fill valleys in the southern part of the county. This aquifer has an average domestic well yield of 5 to 15 gpm at depths of up to 175 feet. In eastern Delaware County, sandstone aquifers yield from 15 to 25 gpm at depths less than 95 feet. A shale aquifer underlies the center of Delaware County and extends from the northern to southern county borders. This shale aquifer yields 0 to 3 gpm at depths of up to 75 feet. Dry wells are common in this aquifer, and generally, homeowners rely upon public supplies, additional storage and/or cisterns, to maintain daily requirements. The western portion of Delaware County is underlain with a carbonate aquifer capable of producing yields up to 1,000 gpm. Farm and domestic supplies of 10 gpm to 15 gpm are usually encountered at depths of less than 85 feet. An overview of the ground-water resources in the county is given in Delaware County Ground-Water Resources, AEX-490.21.
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 the Ohio Department of Natural Resources (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 like streams and lakes. Two inches are retained at the ground surface and evaporate back into the atmosphere in a relatively short time period. Twenty-six of the 38 total inches enter the soil surface through infiltration. Twenty of these 26 inches go into soil storage and later return 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 may result in runoff and how many inches have the potential to reach aquifers. Based on statewide averages of runoff and ground-water recharge, Delaware County's 36 inches of annual precipitation result in about 9 inches of runoff to streams and lakes, and about 6 inches have the potential to recharge aquifers annually. Values for particular locations will differ according to local conditions.
Surface water is a major water source in Delaware County. Approximately 71 percent of the population and industries in the county use surface water. The remaining 29 percent uses water supplied from public or private wells. Alum Creek, the Olentangy River, Hoover Reservoir, the Scioto River and Big Walnut Creek are all used to supply water for Delaware County.
Water use for each of Delaware County's public water-supply systems is given in Table 1, which provides an estimate of the population served, water source, estimated daily water usage and treatment plant capacity.
| Table 1. Water Use in Delaware County, Ohio1. | ||||
|---|---|---|---|---|
| Public Water System | Population Served | Primary Water Source | Water Usage (GPD)2 | Treatment Plant Capacity (GPD) |
| Ashley | 1,057 | Surface Water | 100,000 | 288,000 |
| Olentangy3 | 11,000 | Surface Water | 800,000 | 3,100,000 |
| Alum Creek3 | 10,560 | Surface Water | 1,800,000 | 3,430,000 |
| Delaware City | 21,000 | Surface Water | 2,750,000 | 6,000,000 |
| Galena | 370 | Ground Water | 27,000 | 83,000 |
| Lake of the Woods | 450 | Surface Water | 50,000 | 144,000 |
| Ohio YC Scioto Village | 600 | Surface Water | 75,000 | 576,000 |
| Sunbury | 2,400 | Surface Water | 560,000 | 1,300,000 |
| 1 Abstracted from Inventory of Municipal Water-Supply Systems by County, Ohio (1977), and updated with data provided by Raymond P. Shesky, Ohio EPA, Division of Drinking and Ground Water, Columbus, OH. | ||||
| 2 GPD = gallons per day. | ||||
| 3 Water supplied by Del-Co Water Company. | ||||
Considering all of the uses of water in Delaware County, the quality of water is indeed important. Ground water in the western portion of the county tends to be hard (high levels of calcium carbonate) and may be highly mineralized with calcium and magnesium sulfates. Hydrogen sulfide (rotten egg smell) is also common in certain areas. Despite these water quality concerns, the aquifers underlying this portion of the county are important sources of water. The shale bedrock areas of central Delaware County not only have low yields, but also contain hydrogen sulfide. The sandstone aquifer in the eastern third of the county generally can provide a sufficient supply for residential use.
Questions are often raised about the quality of water from private wells, more specifically, the nitrate concentration. In 1988, 159 county wells were sampled for nitrate content, of which 100 (63 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. Thirty-two wells (20 percent) were tested in the range of 0.3 to 3.0 ppm; these values may or may not indicate human influence. The 20 wells (13 percent) that tested in the range of 3.0 to 10 ppm, may indicate elevated concentrations resulting from human activities. Only 7 wells (4 percent) tested at higher than 10 ppm nitrate-nitrogen, which exceeds the safe drinking-water standard. The average test value over the 159 wells tested was just under 2.0 ppm.
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 excellent for Delaware 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 is intended to provide information to the public on water facts for Delaware County. For more information on water resources and drinking-water quality in the county, contact the Delaware County Extension office. In addition, the following agencies may be able to provide information on other water resources topics in the county: Delaware Soil and Water Conservation District; USDA Soil Conservation Service; Delaware County Health Department; ODNR Division of Water (Fountain Square, Columbus OH 43224); U.S. Geological Survey, Ohio District (975 W. Third Ave., Columbus OH 43212); Ohio Environmental Protection Agency (1800 Watermark Dr., Columbus OH 43266); and Ohio Department of Health (PO Box 118, Columbus OH 43226).
If you have other factual county water-resources information that might be of interest to the public, please send copies to the author of this publication at the Delaware County Extension office.
Delaware County Ground-Water Resources. 1992. K.T. Putnam, A.W. Jones, K.M. Boone and L.C. Brown. AEX-490.21. Ohio Cooperative Extension Service, The Ohio State University.
Gazetteer of Ohio Streams. 1960. Ohio Water Inventory Report No. 12. ODNR Division of Water.
Ground-Water Resources of Delaware County. 1979. J.J. Schmidt. ODNR Division 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 Division of Water.
Inventory of Municipal Water-Supply Systems by County, Ohio. 1977. Ohio Water Inventory Report No. 24. ODNR Division of Water.
Inventory of Ohio's Lakes. 1980. Ohio Water Inventory Report No. 26. ODNR Division of Water.
Monthly Normals of Temperature, Precipitation, and Heating and Cooling Degree Days, 1950-80, Ohio. 1982. Climatography of the United States, No. 81 (by state). National Oceanic and Atmospheric Administration.
Nitrates 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 Cooperative Extension Service, The Ohio State University.
Ohio Ground-Water Quality. USGS National Water Summary - Ohio. 1986. U.S. Geological Survey Water-Supply Paper 2325.
Ohio Ground-Water Resources. USGS National Water Summary - Ohio. 1984. U.S. Geological Survey Water-Supply Paper 2275.
Ohio Surface-Water Resources. USGS National Water Summary - Ohio. 1985. U.S. Geological Survey Water-Supply Paper 2300.
Ohio's Hydrologic Cycle. 1990. L.C. Brown and K.M. Coltman. AEX-461. Ohio Cooperative Extension Service, The Ohio State University.
Ohio's Natural Heritage. 1979. M.B. Lafferty (Ed.). Ohio Academy of Science, Columbus, OH.
Private Water Systems Handbook. 1987. MWPS-14. Midwest Plan Service, Ames, IA. (Available through your county Extension office).
Soil and Water Conservation District Resource Inventory. 1985. USDA-Soil Conservation Service.
Surface and Ground Water Terminology. 1990. L.C. Brown and L.P. Black., AEX-460. Ohio Cooperative Extension Service, The Ohio State University.
Water - Ohio's Remarkable Resource. 1982. ODNR Division of Water.
This publication was produced through the Ohio Water Resources Education Project, in cooperation with: ODNR Division of Water; Ohio EPA; U.S. Geological Survey (USGS), Ohio District; and Ohio Department of Health (ODH). Project leaders are Larry C. Brown and Kristina M. Boone. Support was provided, in part, by: the cooperating agencies; Delaware County Extension Office; Overholt Drainage Education and Research Program; and USDA Extension Service Grant No. 90-EWQI-1-9018.
The project leaders express appreciation to the following reviewers: Ralph Jones and Donald Breece (OSU Extension); A. Wayne Jones, David Cashell and Leonard Black (ODNR Division of Water); Larry Ufferman (Delaware Soil and Water Conservation District); and Tom Edwards (USDA-Soil Conservation Service); Scott Golden (Environmental Health, ODH); Tim Lawrence (Agricultural Engineering, OSU); Larry Antosch (Ohio EPA Division of Water Quality Planning and Assessment); and Linnea Saukko (Ohio EPA Division of Drinking and Ground Water).
A special thanks to Michelle Roby and Ross A. Roberts (Agricultural Engineering Undergraduate Assistants) for help in manuscript and graphics preparation, and Judy Kauffeld and Tonya Ewing (Section of Communications & Technology, OSU 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