Ohio State University Extension

Food, Agricultural and Biological Engineering

590 Woody Hayes Dr., Columbus, Ohio 43210

Defiance County Ground-Water Resources

AEX-490.20

James J. Hoorman
James M. Raab
Kristina M. Boone
Larry C. Brown

Water stored under the earth's surface is a plentiful, yet precious, resource in most areas of Ohio. Humans greatly affect ground water. However, the availability and quality of this resource are influenced directly by the properties of the geologic formation that holds water. The chemical and physical nature of these formations varies from area to area, creating a wide range of water yields and quality at different depths.

This publication contains information about the ground-water resources underlying Defiance County. Its purpose is to help the reader better understand the factors that influence the quantity and quality of ground water. 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. Fact sheet AEX-460 and the publication Defiance County Water Resources, AEX-480.20, are available through your county Extension office.

Aquifers

Geologic formations (e.g., sand, gravel, limestone, sandstone) have the ability to receive, store and transmit water. In general, if a formation is capable of yielding enough water to support a well or spring, it is called an aquifer. The types of geologic material from which the formation originally was made influence its ability to store and transmit water. For example, sands and gravel allow water to flow through easily. By comparison, shale, which originated from compacted layers of mud and clay, allows very little water to flow through it unless the shale is highly fractured.

Three principal aquifers underlie Defiance County. These are unconsolidated coarse-grained aquifers, unconsolidated fine-grained aquifers, and the sedimentary carbonate aquifer. An unconsolidated coarse-grained aquifer consists of highly permeable sand and gravel deposited by glaciers. This aquifer is very productive and is under artesian pressure. Fine-grained unconsolidated aquifers are similar in form and origin to coarse-grained unconsolidated aquifers, but are less permeable because of a higher percentage of mixed fine sands, silt and clay. The sand and gravel deposits usually are interbedded within glacial till.

The carbonate aquifer, which is composed of layers of limestone and dolomite, is the third type of aquifer found in the county. Limestone consists of fossilized sea shells, shell fragments, and consolidated limy mud. Its main mineral is calcium carbonate, CaCO₃. Dolomite is similar to limestone, but has few recognizable fossils; its main mineral is calcium magnesium carbonate, (Ca,Mg)CO₃. Both limestone and dolomite are commonly referred to as limestone or carbonate rocks. The limestone and dolomite formations were deposited between about 380 and 410 million years ago. In most areas of this region, these formations are covered by a layer of glacial till, which is an unsorted mixture of clay, sand, gravel and boulders deposited by a glacier.

Well Yield

The actual yield of a well, in gallons per minute (gpm), will vary considerably depending on the age and depth of the well, the diameter of the casing, well construction, pump capacity and age, and most importantly, properties of the geologic formation. The exact yield and depth of each well will depend on the properties of the geologic formation at the specific location of the well.

Ground-Water Availability

The Ohio Department of Natural Resources (ODNR), Division of Water, maintains a statewide data base of more than 700,000 well logs. The Ground-Water Resources Section of the Division manages this valuable data base, which includes some information collected by the U.S. Geological Survey (USGS) and the Ohio Environmental Protection Agency (Ohio EPA). Since 1948, well log information has been collected to increase the understanding of the ground-water resources in Ohio. Geologists and hydrogeologists continue to study the state's ground-water resources, and as a result, Ohio is one of only a few states that has been completely mapped for ground-water availability (mapped by river basin, from 1959 to 1962).

Estimates of the size, shape, geologic make-up and yields of aquifers are being mapped county by county. Most of Ohio's counties have a completed map. The map presented in Figure 1 is a generalized representation of the water-bearing formations underlying Defiance County (adapted from map by Schmidt, 1982). This illustration is based on a hydrogeologic interpretation of the well log data from Defiance County and surrounding areas. It should be used only as a guide to understanding the ground-water resources in the county. The remainder of this section provides a brief description of the types of aquifers illustrated on the map in Figure 1.

Figure 1. Ground-water resources of Defiance County, Ohio (modified from J.J. Schmidt, ODNR Division of Water, by R.A. Roberts).

AREA A: Sand and Gravel

The sand and gravel aquifer illustrated in Figure 1 as Area A is located in the northwestern part of the county. This aquifer consists of 50 to 250 feet of extensive glacial deposits of sand and gravel, fine sand and thick layers of clay. Underlying the aquifer are Devonian and Mississippian shales, which are poor sources of ground water. The sand and gravel deposits are good sources of water because of the high degree of permeability of this type of formation. Most wells have yields that are adequate for domestic and farm water supplies. Yields of 100 to 500 gpm have been found at depths of 60 to 240 feet. Yields as high as 1,000 gpm are possible from properly constructed wells, which could be used for irrigation, as well as industrial and municipal purposes.

The minerals in this aquifer are water soluble, so water from this formation is hard and may require treatment before being used for many purposes. Small amounts of sulfur and iron are occasionally encountered in water obtained from the glacial till. Water from wells drilled into the limestone may have a high sulfur content.

AREA B: Sand and Gravel with Flowing Wells

This sand and gravel aquifer, illustrated as Area B, is very similar to Area A. The difference is this area lies in a belt of flowing artesian wells, which means many wells flow when drilled. Wells that are not flowing usually have a depth to water of less than 10 feet. Yields of up to 500 gpm can be obtained from this aquifer. Heavy pumping for irrigation or other large uses of water will lower the water table in the immediate vicinity. This may reduce the artesian head on nearby flowing wells and cause them to stop flowing.

AREA C: Limestone beneath Thin Glacial Till

The limestone aquifer illustrated as Area C is part of the regional carbonate aquifer that underlies a major portion of northwest Ohio. It is overlain by 35 to 95 feet of glacial till consisting principally of clay with intermittent deposits of sand and gravel. Virtually all wells are drilled into the limestone, and yields generally are adequate for domestic and farm water supplies. Yields of as much as 20 gpm have been developed at depths ranging from 45 to 95 feet. Yields of 50 gpm or more have been found at depths greater than 235 feet.

The minerals in limestone are water soluble, so water from this formation is generally hard. Water from this formation is considered below average in chemical quality for a carbonate aquifer because of hardness and high concentrations of sulfate and dissolved solids. At greater depths, hydrogen sulfide gas (HS; rotten egg or sulfur odor) is common due to the presence of the mineral gypsum (hydrous calcium sulfate). In an attempt to avoid hydrogen sulfide, many wells are drilled to less than 50 feet; however, lower well yields usually result. Figure 2 is a cross section across Defiance County (referenced in Figure 1 as line X-X') showing the relationship of different aquifers.

Figure 2. Generalized cross section of Defiance County, Ohio (modified from J.J. Schmidt, ODNR Division of Water).

AREA D: Sand and Gravel beneath Thin Glacial Till

Area D illustrates this sand and gravel aquifer. The entire area is underlain by non-water bearing Mississippian and Devonian shales. The glacial till above the bedrock consists of sand and gravel lenses beneath layers of fine sand, silt and clay ranging from 45 to 95 feet thick. Yields of as much as 10 gpm have been encountered near the non-water-bearing shale bedrock at depths ranging from 45 to 110 feet. However, lesser quantities and dry wells are noted. This area also contains occasional sand and gravel lenses that may yield a maximum of 50 gpm. Only small supplies of water can be obtained from the upper portion of the underlying shale bedrock. For domestic purposes, many ponds are constructed in this area for a source of water.

Wells in this area may obtain water from limestone by drilling through 10 to 250 feet of shale, but the water is likely to be highly mineralized. Small yields are occasionally obtained from the upper portion of the shale where, due to weathering, it is porous enough to contain some water. Hard water and sulfur are common water-quality problems.

Ground-Water Levels

The water level in any well typically does not remain constant, but changes depending upon the proximity of adjacent wells and surface streams, and natural rainfall. Ground-water discharge and recharge greatly affect water levels in wells. The ODNR Division of Water monitors ground-water levels using observation wells located throughout Ohio. No observation wells are located in Defiance County. However, observation wells are located in Henry, Putnam and Williams counties.

Ground-Water

Quality Various state and federal agencies have participated in programs to determine ground-water quality in Ohio. In Defiance County, water-quality data for seven wells were available from the ODNR Division of Water. In Figure 1, these wells are noted as Chemical Analysis Sites 1 through 7, and are either municipal, industrial or domestic wells.

The results of some of the chemical tests performed on the water from these Defiance County wells are given in Table 1. The chemical constituents listed are total dissolved solids, hardness (as CaCO₃), hydrogen sulfide, iron and sulfate. All concentrations are given in parts-per-million (ppm). For comparison purposes, drinking water-quality standards for these chemical constituents are also shown. These standards are established by the U.S. Environmental Protection Agency (USEPA) for public water systems for aesthetic reasons (taste, odor, appearance, etc.), and are not enforceable. These chemical constituents do not pose a risk to human health (see notes in Table 1). There are no drinking water-quality standards for private wells.

The information in Table 1 can be used as a guide to what one might expect from an existing or new well. All seven wells were developed in Defiance County and range from 64 to 580 feet in depth. Just as well yields differ, water quality will vary depending on aquifer properties at the specific location of each well. One should not forget that many human activities also affect the quality of ground water.

Summary

Defiance County's ground-water resources are valuable assets to the county's citizens and industry. The availability and quality of these resources are directly influenced by the properties of the geologic formations underlying the county. By understanding the physical and chemical nature of these resources, better decisions can be made about ground-water protection, management and use. This publication was designed to provide the reader with an overview of the county's ground-water resources. It should be used as a guide, and not as a substitute for detailed information and professional advice when drilling a well.

Where to Get More Information

The Defiance County Extension office can provide other publications about Defiance County's water resources. Your Extension agent, the Defiance County Department of Health and the Ohio EPA Division of Drinking and Ground Water (1800 WaterMark Drive, Columbus, OH 43266) can provide information on well-water testing and drinking-water quality. The ODNR Division of Water - Ground-Water Resources Section (Fountain Square, Columbus, OH 43224) is an excellent source of information on ground water. Some of the information in this publication was summarized from the map, Ground-Water Resources of Defiance County, and other information available through the Division of Water. This map is much more detailed than that given in Figure 1, and the Ground-Water Resources Section can provide more detailed information on ground-water availability and wells. The USGS, Ohio District (975 W. Third Ave., Columbus OH 43212), also provides information about ground water in Ohio.

Table 1. Chemical constituents of selected Defiance County wells.
Well No.	1	2	3	4	5	6	7	WQ Std1
Well Depth (feet)	80	64	110	148	71	90	580
Capacity (gpm)	3	3	2	500	4	2	85
Depth to Bedrock (feet)	NE2	63	95	148	68	30	77
Water-Bearing Formation3	G	SH	SH	G	SH	SH	LS
Chemical Constituents4
Total Dissolved Solids	1,022	566	420	507	279	1,770	676	500
Hardness (as CaCO3)	815	248	184	464	153	1,120	403	None5
Hydrogen Sulfide (H2S)	-6	-	-	-	-	110	69	None
Iron	10	2.3	0.48	2.2	1.2	0.11	6.8	0.3
Sulfate	372	180	1.2	-	0.28	740	116	250
1. USEPA Secondary Water Quality Standard.
2. Well constructed in this formation did not encounter bedrock.
3. LS - Limestone; G - Gravel; SH - Shale.
4. Units are parts-per-million, ppm; Comments as per Interpreting Your Water Test Report (1988); Total Dissolved Solids: Concentrations above 500 ppm may cause adverse taste and deteriorate domestic plumbing and appliances. Use of water containing 500 ppm is common. Hardness: Primary concerns are that more soap is required for effective cleaning, a film may form on fixtures, fabrics may yellow, and scales may form in boilers, water heaters, and cooking utensils. Hydrogen Sulfide: Presence of this unpleasant smelling gas is difficult to measure but not difficult to detect, even in small concentrations. Highly corrosive to pump parts and plumbing fixtures, but has no known harmful effects in humans. Iron: Concentrations greater than 0.3 ppm may cause rust-colored stains on laundry, plumbing fixtures and sinks. Metallic taste may be present and may affect the taste of beverages made from the water. Sulfate: Concentrations in excess of 250 ppm may have laxative effect on persons unaccustomed to the water. Also affects the taste of water and will form a hard scale in boilers and heat exchangers.
5. No USEPA Secondary Standard.
6. Data not available.

Bibliography

Defiance County Water Resources. 1992. J.J. Hoorman, K.M. Boone and L.C. Brown. AEX-480.20. Ohio Cooperative Extension Service, The Ohio State University.

Ground-Water for Planning in Northwest Ohio. 1970. ODNR Division of Water.

Ground-Water Resources of Defiance County. 1982. J.J. Schmidt. ODNR Division of Water. (map).

Interpreting Your Water Test Report. 1988. D. Lundstrom and S. Fundingsland. AE-937, No. 13 AENG 10. North Dakota State University Extension Service.

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.

Surface and Ground Water Terminology. 1990. L.C. Brown and L.P. Black. AEX-460. Ohio Cooperative Extension Service, The Ohio State University.

Underground Water Resources (maps of various river basins). 1958-1962. ODNR Division of Water.

Water Testing. 1988. K. Mancl., AEX-314. Ohio Cooperative Extension Service, The Ohio State University.

Acknowledgments

This publication was produced through the Ohio Water Resources Education Project, in cooperation with: ODNR Division of Water; Ohio EPA; USGS, Ohio District; and Ohio Department of Health (ODH). Project leaders are Larry C. Brown and Kristina M. Boone. Support for this publication was provided, in part, by: cooperating agencies; Defiance County Extension office; Defiance Soil and Water Conservation District; Defiance County Pork Producers Association; Overholt Drainage Education and Research Program; and USDA Extension Service Grant No. 90-EWQI-1-9018. The project leaders acknowledge the following reviewers: Denise Lange and George Derringer (USDA-Soil Conservation Service); Bernie Czartoski (Maumee Valley RC&D); David Cashell (ODNR Division of Water); Scott Golden (Environmental Health, ODH); Randall Reeder (Agricultural Engineering, OSU); Steve Hindall (USGS, Ohio District); and Tim Fishbaugh (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.