The citizens of Portage County are highly dependent on groundwater for drinking, municipal, industrial, agricultural, and other uses. So too are the county’s streams, lakes, wetlands, and aquatic plant and animal communities. Our groundwater is owned by all of us in a public trust. Along with the rights of ownership go the responsibilities for stewardship and for passing the resource on to future generations.

New groundwater challenges have been identified since Portage County wrote its last groundwater management plan in 1987. Planning and Zoning Department Director Chuck Kell requested that these challenges be dealt with in the context of a new (or updated) groundwater management planning effort. This document summarizes available groundwater information and identifies the challenges that need to be addressed in a new planning effort. Three crucial groundwater resource challenges distinctly stand out: groundwater quantity, nitrate pollution, and pesticide pollution.

Groundwater quantity challenges arise when pumping lowers the water table so that all users are unable to get sufficient water for their needs, and when pumping diverts water away from streams, lakes, and wetlands. An acute groundwater quantity concern exists in the Little Plover River basin, where groundwater use may be leading to the demise of the stream and its native brook trout fishery. A strategy is needed to deal with known acute concerns, and to identify other potential problem areas.

Nitrate pollution affects much of Portage County’s groundwater and most of its wells. About 20% of county wells exceed the standard. A variety of human health concerns regarding nitrate exist, as well as concerns about toxicity to aquatic wildlife. Nitrate concentrations in Portage County groundwater have been increasing for about 30 years, and the increase continues. Reducing nitrate pollution will require tackling agricultural sources, which are responsible for perhaps 95% of nitrate pollution.

Pesticide pollution also affects large numbers of county wells. Atrazine is the largest problem, occurring in 40% of wells. About 3% of wells have been estimated to exceed the atrazine standard, but this is likely an underestimate caused by a faulty interpretation of the analytical method. Other pesticides are also likely present in groundwater. More information is needed on what pesticides are used in the county and which pesticide residues leach to groundwater. Further, better information is needed on the toxicology data that exist for these compounds and where toxicology data are lacking.

Many other groundwater resource issues have been dealt with effectively by the policies and laws instituted in the 1980s. For instance, new pollution from point sources such as underground storage tanks and industrial sites has been virtually eliminated, and old point sources are being cleaned up through a variety of government programs. County zoning for homes serviced by septic systems seems to be effectively protecting groundwater, and sewering of older, dense subdivisions has helped improve groundwater quality as well.

Natural groundwater quality and well problems such as iron, manganese, corrosive water, bacteria, and radionuclides are distinct from groundwater resource issues and need not be handled as part of a groundwater management planning strategy. For iron, manganese, corrosive water, and bacterial contamination, sufficient public education materials and strategies are available from sources such as health departments and University Extension. Programs dealing with these problems in some instances go back two decades and should continue. The issue of radionuclides as a health threat is relatively new. More work on this drinking water threat may be needed through health agencies.

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The citizens of Portage County are highly dependent on groundwater resources for drinking, municipal, industrial, agricultural, and other uses. In addition, much of the county’s natural environment - streams, lakes, wetlands, and plant and animal communities - depends on groundwater. By law, all groundwater is owned by Wisconsin citizens. With that right goes the responsibility of stewardship and passing the resource along to future generations.

Portage County has not revisited its groundwater management planning efforts since 1987. Since that time, a number of new challenges have come to light. Per the direction of Planning and Zoning Department Director Chuck Kell, these challenges are being dealt with in the context of a new (or updated) groundwater management plan. Two recently established groups, the Groundwater Management Subcommittee and the Public Involvement and Education Subcommittee of the Portage County Groundwater Citizens Advisory Committee, are charged with moving the planning effort forward. The groundwater management effort can be summarized as a three part process:

1. Where are we now? This step includes describing the current state of Portage County’s groundwater resource, writing a problem statement (identification of problems and issues that need to be addressed in a groundwater management planning exercise), and beginning to create public awareness of groundwater issues in the county.

2. Where do we want to go? Determining groundwater resource goals to address the problem statement. (The process for this step has yet to be firmly established. Some type of detailed public interaction process will be needed.)

3. How do we get there? Again, some sort of public process will be used to determine ways to get to groundwater goals.

A feedback loop will then be needed so that groundwater management becomes an ongoing process rather than something that is done at 10-15 year intervals.

The purpose of this document is to use readily-available knowledge to describe the current state of Portage County groundwater. The document also identifies where information gaps exist. Information gaps may be filled during the planning process, but because some unknowns and uncertainties will always exist, it is important not to indulge in "paralysis by analysis", i.e., trying to answer every question before proceeding in the planning effort.

Parallel to development of this document is the county’s effort to create a "groundwater inventory" report. That effort was initiated as a one year project about three years ago, and an exact date for completion is presently uncertain. The county’s inventory report will amplify what is described here, but it is important not to let the lack of that report further delay the planning process.

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Portage County covers about 500 thousand acres (Figure 1). Its landscape is dominated by agriculture (200,000 acres) and forest (190,000 acres), with smaller amounts of wetlands, urban, and rural development (Table 1). The amount of irrigated farm land continually increases, and covered 76,000 acres in 1997 (Wisconsin Department of Agriculture, Trade, and Consumer Protection). Major crops include field corn, potato, snap bean, sweet corn, soy bean, and forage (Table 2). Portage County also houses 15,000 dairy cows plus other cattle and livestock.

Table 1. Area and percent of area of Portage County land covers. (Source: Portage County Planning and Zoning, from 1992 aerial photography.)

* Includes some grazed farmland and permanent pasture.

Table 2. Planted area of some agricultural crops in Portage County for 1998 (Source: Wisconsin Department of Agriculture Trade and Consumer Protection, 1999. Wisconsin Agricultural Statistics).

For purposes of discussing groundwater, the physical geology of Portage County can be divided into four provinces: shallow rock province, moraine province, sand plain province, and marsh province (Figure 2). The geology and hydrology of each province determines many of the characteristics regarding natural groundwater quality and availability, as well as the overlying land uses that impact groundwater quality.

The shallow rock province in the northwest tends to be flat to gently rolling. Uplands are frequently well-drained, but flatter areas tend to be wet to marshy, and soils tend to be heavy and somewhat shallow. Wells in this area usually tap the bedrock aquifer. Well yields are frequently poor - sometimes only a few gallons per minute. Some dominant land covers are dairy, forage, and grain farming, forests, and wetlands.

The moraine province in the eastern third of the county is typically gently rolling. A mixture of glacial sediments, ranging from sands to loams to somewhat clayey materials, covers bedrock in thicknesses sometimes reaching over a hundred feet. Wells usually tap the glacial sediments. Yields can be excellent - over 1000 gallons per minute. Land uses tend to be dairy, forage, and grain farming, irrigated agriculture, forests, and wetlands.

The sand plain province occupies much of the middle of the county. The land surface is flat, with a thick layer of sand (frequently over 100 feet) covering bedrock. Wells usually tap the glacial sediments. Yields are excellent, exceeding 1000 gallons per minute. Land use is dominated by irrigated agriculture. Some dairy and grain farming and forests are also common.

The marsh province occupies the southwest part of the county. Its geology is similar to the sand plain province, but the area is poorly drained. The area was once part of a large wetland until ditching and burning of peat in the earlier part of this century. Land uses include various types of agriculture, conservancy, and cranberry culture.

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Our Groundwater Resource

Some Groundwater Basics

Groundwater is the water under the earth’s surface that moves freely through the spaces between soil particles or cracks in bedrock and is the water that is pumped from wells. The rocks or soil materials that hold groundwater are called "aquifers".

Groundwater is part of the earth’s water cycle. The water cycle (Figure 3) in Portage County starts with local precipitation averaging 30 to 32 inches per year. About 1 to 4 inches (depending on which part of the county) of the precipitation runs off directly into streams. Another 20 to 22 inches is temporarily stored in the soil and gets transpired by plants back into the atmosphere, and 6 to 11 inches percolates through the soil and becomes groundwater. The portion of precipitation that reaches groundwater is called "recharge".

Figure 3. The water cycle in Portage County. Of the 30" or so precipitation that we receive per year, about 6-11" recharges groundwater. Groundwater eventually discharges to lakes and streams.

Groundwater is not stagnant, but rather moves from areas where water recharges aquifers (recharge areas) to areas where it leaves aquifers (discharge areas). Most of Portage County is a recharge area. Discharge areas are lakes, streams, and wetlands. The major groundwater discharge areas in Portage County are the Wisconsin River and its tributaries, and the Tomorrow River system. Because the county is abundant in streams, groundwater generally flows only a few miles between where it recharges to where it discharges (Figure 4). The average time between recharge and discharge in Portage County is probably around 50 years or so, but ranges from days to hundreds of years.

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Groundwater Challenges: Quantity

Groundwater quantity challenges can be due to natural or human-influenced causes. Natural causes are the result of aquifers that yield little water to wells because the spaces or cracks in the rock are too sparse or too tiny to effectively transmit and store water. This condition is particularly common in the shallow rock province of Portage County. Human-influenced quantity challenges can result from pumping. Pumping can lower the water table sufficiently such that all users are unable to get sufficient water for their needs. The pumping of groundwater also has an influence on lakes, streams, and wetlands. When groundwater is diverted away from its natural discharge area, insufficient groundwater may be available to maintain the natural value of our surface waters.

Groundwater Pumpage

Total annual pumpage in Portage County is estimated at 19 billion gallons per year - enough to fill a lake 1 mile square to a depth of 90 feet. The largest use of groundwater is for agricultural irrigation, followed by industry, municipal, and all others (Figure 5).

Pumpage vs. Consumption and Diversion

The concept of "groundwater pumpage" compared to "groundwater consumption" and "groundwater diversion" needs some explanation. The amount of pumpage is not the only important consideration; also important are the distribution and density of the pumpage, and the amount of groundwater actually consumed or diverted from its natural discharge zone.

Most rural residential groundwater pumpage has little effect on the aquifer and on surface waters. That is because most water pumped for this purpose cycles through a household and is then discharged back to the aquifer through the septic system. The net groundwater consumption or diversion is negligible. The same is true for much of the non-irrigation agricultural use. Water for livestock, milkhouse cleaning, etc., is usually returned to the aquifer when wastewater and animal waste are returned to the soil.

However, for irrigation, industrial, and municipal pumpage, a good deal of the water is "consumed" or diverted from its natural discharge zone. For agricultural irrigation, the net effect is that groundwater recharge is reduced about 30 to 40% on each irrigated acre, which reduces discharge to lakes and streams by an equal amount. Pumping for industrial and municipal purposes can have a greater influence because most of this pumping is concentrated in small areas, and groundwater pumped for this purpose is frequently diverted away from the streams where the groundwater would naturally want to discharge.

For instance, the Stevens Point wellfield takes water from the Plover River basin (amounting to about 10% of the river’s flow), circulates it through the city, and discharges the water to the Wisconsin River. Similarly, the Village of Plover wells take groundwater from the Little Plover Basin, and discharge it to the Wisconsin River (Figure 6). Groundwater models have shown that flows in the Little Plover could diminish by over 40% when the well pumpage reaches design capacity. This 40%, added to the 10% or so reduction from irrigation, could mean the demise of the Little Plover as a native brook trout fishery.

By far, the most concentrated pumpage in the county is in the Village of Whiting, where a high density of municipal and industrial wells are located. This wellfield likely has some, though possibly small, influence on surface water. Monitoring wells in the vicinity of this wellfield have shown some declines in water levels. Groundwater use in the county continues to increase, through expansion of irrigated agriculture, additions to industrial capacity, and increasing municipal use.

Groundwater Quantity Potential Data Gaps

1. Information on the locations, pumpage, and discharge points for other major water users (other municipalities and industries) in the county to determine if other areas of concern, similar to the Little Plover.

2. Information on long-term impacts of present pumping regimes.

3. Planning for increasing water use, methods for using the water we currently extract more efficiently, potentially using surface water for non-potable uses (e.g., using Wisconsin River water for industrial use, thereby freeing up groundwater for potential municipal use.)

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Groundwater Challenges: Quality

When discussing groundwater quality, it is important to understand the nuances between natural groundwater quality (which we can do little about except treat it or avoid it), well problems (which we may be able to do something about as individuals), and groundwater resource pollution (which we have societal obligation to address). These themes carry through the following discussion.

Natural Groundwater Quality

The natural groundwater quality of Portage County is generally very good; usually human-sourced pollutants are the problem. Where natural water quality challenges exist, they include iron, manganese, radionuclides, and corrosive water.

Iron and manganese are two metals that occur naturally in the sediment and rock that makes up the county’s aquifers. Both are essential to life, but become a nuisance when they are present in water at too high a concentration. This happens under certain chemical conditions when oxygen in the groundwater becomes depleted, and the iron and manganese in aquifer materials undergo a chemical change that makes them soluble in groundwater. The main concern with iron and manganese is not health, but rather taste, odor, and staining of plumbing fixtures and laundry. The US Environmental Protection Agency set a drinking water standard based on aesthetic (not health) concerns of 0.3 parts per million for iron and 0.05 ppm for manganese. Iron and manganese tend to be more of a problem in the shallow rock and marsh provinces.

Radionuclides are elements that undergo nuclear decay. Nuclear decay is the process by which atoms split to form other atoms and in the process emit potentially harmful radiation. A number of radioactive elements - radium, radon, uranium, thorium, and others - occur in the bedrock aquifer, particularly at greater depths. Since bedrock wells are more common in the northwest part of the county, this is likely where the greatest radioactivity concerns exist. The USEPA is in the process of revising standards for radioactivity in drinking water. The current standards are: "combined radium 226/228 of 5 pCi/L; a combined standard of 4 mrems for beta emitters; and a gross alpha standard for all alphas of 15 pCi/1, not including radon and uranium" (Source: USEPA, http://www.epa.gov/ogwdw000/standard/radionuc.html ). We do not know at this time the frequency of wells in Portage County with radioactivity standard exceedances.

"Corrosive water" is a term used for naturally soft and acidic water. The water itself is not harmful, however its chemistry is right for dissolving metal in plumbing. This results in damage to plumbing (e.g., leaks in copper pipe), but more importantly, dissolved copper and lead in drinking water. Dissolved lead is more of a problem in older homes (pre-1984) when lead solder was commonly used, but dissolved copper is a problem in homes that have copper pipe. Corrosive water is common in the western third of the county (Figure 7).

Microbial Contamination

Microorganisms (bacteria, viruses, and others) are everywhere in the environment, including aquifers and groundwater. Most are harmless or even beneficial, but some can cause disease and others create nuisance conditions.

Coliform bacteria and fecal coliform bacteria are frequently analyzed in well water samples. Coliform bacteria are a broad group that have members who live in soil, water, vegetation, and in the gut of animals. Fecal coliform bacteria are members of the group who specifically live in the gut or in feces. Most members of the coliform group do not cause disease, however, they are good indicators that a breach exists in the sanitary condition of a water system. In Portage County, coliform bacteria are usually not present as a groundwater contaminant, but rather, enter wells via a defect (missing well cap, a cracked casing, poor well construction) or an unsanitary condition adjacent to a well (e.g., a privy near a shallow well).

Groundwater Pollutants

Lists of groundwater contaminants can be quite extensive. This discussion will only focus on those of common concern in Portage County.

Metals - Metals that are of concern to drinking and groundwater include arsenic, lead, cadmium, mercury, and others. When found in groundwater, these would most likely be found in association with landfills, electro-plating, and other industrial sites. Metals pollution of groundwater is rarely widespread. No instances of metals pollution of groundwater are known by the Portage County Water Quality Specialist.

Organic pollutants from fuels, solvents, etc. (excluding pesticides) - Common pollutants in this category include benzene, toluene, dichlorethane, trichloroethylene, and others. Instances of this pollution are relatively rare, usually cover small areas, and frequently are related to accidents. Most are due to old spills around gas stations, dry cleaners, industrial sites, and pipelines. About 40 wells in the county are believed by the Portage County Water Quality Specialist to contain these pollutants.

Pesticides - The term "pesticide" includes herbicides, insecticides, nematocides, fungicides, and other compounds used to control organisms. Over 90 different pesticide products were reported as being used in Wisconsin. Pesticide application rates vary substantially among crops; averaging about 0.8 pounds (as active ingredient) per acre for soybean, 2 to 3 pounds per acre for field corn, and about 28 pounds per acre on potato. (Source: Wisconsin Department of Agriculture, Trade, and Consumer Protection, 1997. 1996 Wisconsin Pesticide Use.)

Pesticides are also used around homes, and on turf and gardens. The most commonly used pesticide around households is the 2,4-D contained in "weed and feed" lawn fertilizer formulations. Also used around households are malathion, carbaryl, and diazinon. At label application rates, 1.75 pounds of 2,4-D can be applied on a home lawn with two applications permissible per year. Actual usage is less. In a survey of two subdivisions with fairly well manicured lawns, only about half of households used a weed and feed formulation on their lawns, and then only once per year (Source: C. Mechenich et al., 1991. Chemical use and attitudes about groundwater in two Portage County Wisconsin subdivisions.)

The split between pesticides applied for agricultural compared to nonagricultural purposes is not precisely known, but a perspective may be gained by using the following comparison suggested by a Wisconsin Department of Agriculture, Trade, and Consumer Protection official (James Vanden Brook, Groundwater Unit Leader) The herbicide 2,4-D is likely the most commonly used nonagricultural pesticide. In the US, 16 times more 2,4-D is used in agriculture than on turf (Sources: I.C. Munro et al., 1992. A comprehensive, integrated review and evaluation of the scientific evidence relating to the safety of the herbicide 2,4,D. M.P. Kelty, undated. 2,4-D: a statement of position.). Because 2,4-D makes up only 0.2% of the agricultural pesticides used in Wisconsin, it follows that home and other turf use of 2,4-D is only 1/16 of 0.2% (0.013% or about 1/10,000) of the total agricultural pesticide use. While this analysis is imperfect (it neglects other, less commonly used pesticides), it demonstrates relative magnitudes of pesticide use.

The picture is murky on which pesticide residues ("residues" means the parent pesticide plus its related degradation products) might be occurring in Portage County groundwater, for several reasons. First, with the exception of atrazine residues, few wells have been sampled for pesticides. Second, well water samples are usually only analyzed for one or a few pesticides, not all those that are present. Third, no single analysis is able to examine for all pesticide residues. Finally, analytical methods are not commonly available to look for all the pesticide residues that might be present.

What do we know about pesticide pollution in Portage County groundwater?

1. Atrazine residues are widespread, having been detected in about 40% of Portage County wells. About 3% of wells are known to exceed the standard (Figure 8). This has led to the establishment of several atrazine moratorium areas in the county - areas where atrazine cannot presently be used.

2. Many more wells in which atrazine has been detected probably exceed the atrazine standard. A problem exists that most wells are tested for atrazine using an"atrazine screening test". This test consistently underestimates the true amount of atrazine residues present in groundwater. As Figure 9 shows, 20% of wells testing below 1 part per billion in reality exceed the groundwater standard of 3 parts per billion.

3. Alachlor ESA, one of the degradation products of the pesticide alachlor, is probably a common pollutant. A Department of Agriculture Trade and Consumer Protection (DATCP) study found that 15% of wells tested in central Wisconsin contained this compound (DATCP, 1995. A survey of atrazine in Wisconsin groundwater). Some controversy exists over at what levels alachlor ESA should be regulated. In the interim, the Wisconsin Division of Health has adopted a 20 parts per billion Health Advisory Level.

4. Metolachlor and metribuzin may also be present in groundwater near where they are used, though not necessarily above standards. These have been found in monitoring wells down gradient of vegetable fields, but little is otherwise known about their distribution.

5. It is likely that other pesticide residues are present in groundwater, but too little information and monitoring is presently available to assess which ones.

6. Data on the prevalence and toxicology of potential pesticide residues are not well established. Regarding drinking water standards for pesticides, the United State Geological Survey pointed out (1999, Distribution of Major Herbicides in Ground Water of the United States), "These criteria [drinking water standards], however, may not accurately reflect the overall health risks associated with pesticide detections in water resources because they have been established only for a relatively small number of pesticides and they do not account for the additive or synergistic effects of mixtures, impacts on the health of aquatic ecosystems, or the effects of pesticide degradates."

Nitrate - Nitrate is a chemical form of nitrogen. It is the most common groundwater contaminant found in Portage County. Nitrate exceeds drinking and groundwater standards in about 20% of Portage County wells. The exceedances are especially prevalent in irrigated parts of the county (Figure 10), particularly the sand plain province and other areas where irrigation is concentrated, for instance, in the northeast near Rosholt. In such areas, the percentage of wells exceeding the nitrate standard is sometimes over 70% (Figure 11). 

The drinking water standard (10 parts per million as nitrate-nitrogen) is based on the risk of methemoglobinemia (blue baby disease) to infants. Other countries have adopted similar standards. Three cases of methemoglo- binemia have been reported in Wisconsin since 1990. In 1999, a critically ill infant girl from Grant County required a Medflight to University Hospital in Madison where she remained hospitalized for more than two weeks. Other concerns over health risks associated with nitrate in drinking water have been expressed regarding non-Hodgkins lymphoma, gastric cancer, hypertension, thyroid disorder, birth defects, and miscarriage. Besides human health, concerns about nitrate include toxicity to livestock, fish eggs and fry, amphibian eggs and tadpoles, and the formation of the "Dead Zone" in the Gulf of Mexico.

Nitrate coexists with other forms of nitrogen in a complex cycle. Sources of nitrate include atmospheric deposition, applications of fertilizer, manure, waste material and dead plant and animal tissue. Nitrate is a fairly stable form of nitrogen under aerobic conditions, and other nitrogen forms will frequently convert quickly to nitrate under these conditions.

On a statewide basis, 90% of nitrate reaching groundwater is from agriculture land uses, 9% from septic systems and 1% from other sources (Figure 12). The fraction of nitrate originating from agriculture is probably higher for Portage County since it has a higher than average proportion of agricultural land uses. For instance, in the wellhead protection area for the Village of Plover, 99% of the nitrate originates from agriculture. Other sources can be locally important. Nitrate loading from septic systems in dense, unsewered subdivisions can be as high as some of the most intensive farming operations. Developments that have a density of four septic systems per acre (quarter-acre lots) would be expected to load the same amount of nitrate to groundwater as an acre of potato or sweet corn.

Nitrate pollution has resulted in substantial costs in Portage County that have been borne by taxpayers, utility customers and private well owners. Portage County has had three municipal wells (Whiting, Plover, and Amherst) that have had to install nitrate removal systems or drill new wells. Costs have involved capital expenses of $2.3 million for Plover and $630,000 for Whiting. In addition, these facilities incur continuous operating costs for energy, regeneration salt, maintenance, and wastewater disposal. Costs for non-community (e.g., schools, churches and businesses) and private water systems are more difficult to ascertain because few data are available.

Nitrate concentrations in Portage County groundwater are generally increasing, according to monitoring and modeling studies. Two readily available examples (others are available) include the Village of Whiting municipal well and baseflow in the Little Plover River (Figure 13 and 14). The upward trend is due to long term increases of nitrogen fertilizer use as well as land conversion to more intensive agriculture. Nitrogen fertilizer use began increasing rapidly in the early 1960s, and did not begin to level out until the 1980s (Figure 15). Concurrently, shifts to more intensive agriculture, as witnessed by increased acreage in irrigated agriculture, occurred. Since groundwater has a long residence time, averaging perhaps about 50 years, it will take time for groundwater to come into equilibrium with current nitrate loading to groundwater. Nitrate levels will stabilize only when nitrate loading decreases and after older, nitrate-free water has discharged from aquifers and has been replaced by newer, high-nitrate water. Studies looking at nitrate levels in the Stevens Point - Whiting - Plover wellhead protection area project that nitrate levels will might rise another 50% over current levels.

Figure 13. Increasing nitrate in the Village of Whiting well.

How has nitrate pollution been dealt with in the past? As part of the last groundwater management plan, some inroads were made in controlling nitrate pollution. For instance, sewering subdivisions was encouraged, and has been implemented. Zoning for two acre minimal lots sizes for homes requiring septic systems has brought this land use into compatibility with the nitrate standard. (Note, however, that some townships do not use county zoning.) However, relatively little progress has been made in reducing nitrate loading from agricultural lands.

Some additional background on nitrate and nitrogen fertilizer use for agriculture is needed. Nitrate loading to groundwater from agriculture can be divided into that which comes from overapplications and that which will come from recommended applications. Overapplications are simply applying more nitrogen in the form of fertilizer, legumes, and manure than that required to maximize crop productivity. Surveys have consistently shown that Wisconsin farmers frequently apply more nitrogen than is necessary. For instance, a survey of more than 1500 farmers showed that, on average, they applied 40 pounds per acre of nitrogen beyond University of Wisconsin recommendations for maximizing corn yields. (The 40 pound figure is conservative in that it didn’t account for residual soil nitrate, only accounted for first-year legume and manure nitrogen credits, assumed no incorporation of manure, and used the lowest value when a range was presented for manure or legume credits.) Other surveys, for instance, the Farm Practices Inventory for the Tomorrow-Waupaca Watershed, reinforce the idea.

Figure 16. Nitrate loading calculated for some irrigated crops on sandy soils for both University recommendations Best Management Practices and conventional practices.

To generalize, the situation with regard to nitrate is:

1. Nitrate levels will continue to increase without additional control measures.

2. In general, present strategies to deal with nonagricultural nitrate loading appear effective. Some localized problems (older, high density subdivisions) remain.

3. Agricultural nitrate pollution is where the bulk of the problem currently exists.

4. In some parts of the county and with some agricultural systems (non-irrigated systems, dairy agriculture, agriculture in areas with heavier soils) traditional approaches of reducing nitrate loading by cutting available nitrogen on fields to recommended levels may substantially improve groundwater. More information is needed.

5. With some agricultural systems (irrigated agricultural on sands), universal implementation of recommended practices would still result in continued increases in groundwater nitrate. New strategies will be needed in this industry for improvements to be made.

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Lists of potential activities that can result in groundwater contamination are amazingly large, however, the number of these that actually occur in Portage County is much smaller, and the number that are a potential or real threat to groundwater is smaller yet (Table 3).

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Conclusion and Recommendations

Groundwater Resource Issues

Three major groundwater resource issues exist in Portage County: groundwater quantity, nitrate pollution, and pesticide pollution.

Groundwater quantity issues are due to pumping for irrigation, municipal, industrial, and other uses. When groundwater is consumed or diverted by pumping, it does not reach its natural discharge area. This results in less flow to streams, lakes, and wetlands. An acute groundwater quantity concern exists in the Little Plover River basin, where groundwater use may be leading to the demise of the stream and its native brook trout fishery. A strategy is needed to deal with known acute concerns, and to identify other potential problem areas.

Nitrate pollution affects much of Portage County’s groundwater, and most of its wells. About 20% of wells exceed the drinking and groundwater standard. A variety of human health concerns regarding nitrate exist, as well as concerns about toxicity to aquatic wildlife. Nitrate concentrations in Portage County groundwater began increasing about 30 years ago. That increase will continue without efforts to reduce nitrate pollution. This will not be easy, because it means tackling agricultural sources, some of which will continue to lose over 100 lbs of nitrate-nitrogen per acre even when using University Extension recommended practices.

Pesticide pollution also affects large numbers of wells in the county. Atrazine is the largest problem, occurring in 40% of wells and exceeding standards in at least 3% of wells. The type of atrazine analysis used on most samples underestimates concentrations, so it is possible that many additional wells exceed the standard. In addition to atrazine, other pesticides may be present in groundwater. More information is needed on what pesticides are used in the county and which pesticides and which pesticide degradation products leach to groundwater. Further, better information is needed on the toxicology data that exist for these compounds and where toxicology data are lacking.

Many other groundwater resource issues have been more-or-less successfully dealt with by the policies and laws instituted in the 1980s. For instance, pollution from new point sources such as underground storage tanks and industrial sites has been virtually eliminated. Old point sources are being cleaned up by a variety of governmental programs. County zoning for homes serviced by septic systems seems to be effectively protecting groundwater, and sewering of older, dense subdivisions has helped improve groundwater quality as well.

Natural quality issues and well problems

Natural groundwater quality and well problems such as iron, manganese, corrosive water, bacteria, and radionuclides are distinct from groundwater resource issues and need not be handled as part of a groundwater management planning strategy. For iron, manganese, corrosivity, and bacterial contamination, sufficient public education materials and strategies are available from sources such as health departments and University Extension. Programs dealing with these problems in some instances go back two decades and should continue. The issue of radionuclides as a potential health threat is relatively new. More work on this drinking water threat may be needed through health agencies.

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goals and strategies  |  nitrate  |  pesticides  |  quantity

overview  |  demographics  |  geology  |  land use  |  precipitation  |  soils  |  topography

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