DEVELOPING ENVIRONMENTAL INDICATORS FOR MINNESOTA
Groundwater
The Environmental Indicators Initiative
State of MinnesotaFunded by the Minnesota Legislature
on recommendation of theLegislative Commission on Minnesota Resources
Sponsored byThe Environmental Quality Board
1998
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Citizens and decision makers useenvironmental indicators to helpeffectively manage and protectMinnesota�s groundwater. Environ-mental indicators answer fourquestions.
What is happening to ourgroundwater?Groundwater condition can beassessed by determining key hydro-logical features and tracking indica-tors of water quantity and quality.Important hydrogeologic featuresinclude groundwater distribution,flow and connectivity. Changes inwater quantity can be assessed usingwater-level indicators in observationwells. Water quality is measured withcontaminant indicators such asnitrate concentration.
Why is it happening?Indicators of human activities thataffect groundwater quantity andquality include water use (irriga-tion, public supply), factorsinfluencing recharge rates (imper-vious surface), and sources ofcontamination (septic tanks,storage tanks, landfills, fertilizers,animal waste, etc.)
How does it affect us?Changes in groundwater quantity andquality may diminish the flow ofbenefits. Indicators of how we areaffected include incidences ofwater restrictions based ondiminished water availability,number of drinking water welladvisories and drinking watertreatment costs.
What are we doing aboutit?Societal strategies to maintain or restorehealthy groundwater systems includegroundwater protection andmanagement, development oflocal water management plans,and ongoing research to learnmore about Minnesota�s hiddenwater resources.
In this chapter we outline importantbenefits from groundwater systems,the key ecological characteristics thatdetermine groundwater conditions,the pressures affecting groundwatertoday, the current status and trendsrelating to groundwater, and themost significant policies and pro-grams that affect Minnesota ground-water. In this chapter we giveexamples of indicators that provideimportant information aboutMinnesota groundwater.
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HIGHLIGHTSBenefits of Groundwater� Supplies drinking water to 70%
of Minnesotans� Used for irrigation of croplands� Supports industrial and
commercial activities, e.g.,mining, paper production, foodprocessing
� Provides base water flow tosurface waters and uniqueecosystems, e.g., fens
� Helps maintain water flows ofrivers and streams duringdrought
Important EcologicalCharacteristics� Minnesota has 14 principal
aquifers. Regional differenceshave implications for their useand susceptibility tocontamination.
� Geology and climate determinecomplex linkages betweensurface water and groundwateraquifers. Not all theserelationships are wellunderstood.
� Some aquifers have naturalcontaminants from surroundingrocks and sediments. Introducedcontaminants can leach throughsoils and surface waters to reachgroundwater aquifers.
� Once depleted or contaminated,aquifers can require extremelylong time periods to undergoregeneration or self-purification.
Pressures� Consumptive uses (e.g., irrigation
and lawn watering) may diminishgroundwater availability,especially during periods ofdrought.
� Leaching of contaminants fromlandfills, toxic waste sites, storagetanks, and accidental spills candiminish groundwater quality.Problems are associated withimproper storage, use, ordisposal of industrial,agricultural, business, andresidential chemicals.
� Urban and lakeshoredevelopment and agriculturalactivities are primary sources ofnon-point source pollution.Fertilizers, animal waste, andleaky septic systems canintroduce nitrate intogroundwater systems.
Status and Trends� Overall, Minnesota has large
volumes of good quality water,but human activities have alreadycaused some aquifer depletionand contamination in localizedareas.
� The majority of groundwateruse is for public water suppliesand irrigation.
� Use for public water suppliesincreased from 53 billion gallons(34% from groundwater) in1950 to 174 billion gallons (66%from groundwater) in 1995.
� Use of groundwater forirrigation increased from nearzero levels in the 1960s to 46billion gallons in 1995.
� Nitrate is the most widespreadcontaminant associated withhuman activities.
� 32,000 underground storagetanks (gas/fuel oil for schools,homes, industry) and 500,000residential septic systems occuracross the state.
� By 1995 all landfills were linedor covered, reducing leachateentering groundwater by 73%.
Existing Policies andPrograms� Federal laws (e.g., Clean Water
Act, Safe Drinking Water Act)set groundwater quality anddrinking water standards.
� The Minnesota GroundwaterProtection Act (1989) aims tomaintain groundwater that is freeof human-induced pollutants.
� State and local agencies havecomplementary programs tomanage Minnesota�sgroundwater. For example, theMinnesota Pollution ControlAgency and the MinnesotaDepartment of Agriculture focuson protecting groundwaterquality. The MinnesotaDepartment of Health works toprotect wells and drinking watersafety. The MinnesotaDepartment of NaturalResources focuses on water useand groundwater quantity.
� County governments developand implement comprehensiveLocal Water Management Plans.
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BENEFITS OFGROUNDWATERMinnesota�s aquifers provide largevolumes of good-qualitygroundwater. While rivers and lakesare also important sources of water,about 70% of Minnesotans dependon groundwater as their primarywater supply (MPCA 1995a).Groundwater supports Minnesota�sagriculture and industry as well; it isthe major source of water for cropirrigation, food processing, and otherindustrial uses (MDNR 1997). Inrecent years Minnesota has usedmore than 200 billion gallons ofgroundwater annually foragricultural, industrial, commercial,and domestic uses, thus highlightingthe importance of this resource(MDNR 1997, 1995).
Groundwater also providesimportant ecological benefitsthrough its interactions with streams,lakes, and wetlands. Groundwatercontributes 40% of the annual flowin streams across the United States(US EPA 1996). This contributioncan improve the quality and quantityof stream water. For example,groundwater aquifers provide cleanwater to tributaries along theMinnesota River, which mayimprove its water quality(IGWMCG 1995). And during thedrought of 1988, groundwaterdischarge maintained much of theflow of the Mississippi River and itstributaries, allowing barge andrecreational traffic to continue tonavigate during dry periods (Job andSimons 1994). Groundwater aquifersalso help sustain other ecosystems byrecharging wetlands and uniquesystems such as fens and cold-water
trout streams. Thus groundwater hasan important, but sometimes hidden,relationship with other valuedecosystems.
THEGROUNDWATERSYSTEMWhile it is easy to think aboutgroundwater as a physically isolatedresource, surface waters andgroundwaters together form theindivisible water resource system, asillustrated by the hydrologic cycle(Margat 1994) (Figure 1). Water thatfalls as rain and snow accumulates insoils and surface water bodies, butsome of it percolates intogroundwater aquifers. Water remainsin sediments, fractures, and porespaces of rocks, and more rarely in
underground caves, for days tothousands of years, but eventually itmakes its way back to the earth�ssurface, where it flows in streamsand rivers, collects in wetlands andlakes, and is used by plants. Withevaporation of water back into theatmosphere, the hydrologic cyclebegins again. In this process aquifersserve as both reservoirs andconductors; they not only store waterbut also allow water to flow throughinterconnections among surface andgroundwater systems, thus sustainingthe water cycle (Margat 1994).
The groundwater system is dynamicand can exhibit seasonal and yearlycycles of recharge and drawdown,or renewal and depletion.Groundwater aquifers, particularlythose that are closely connected tothe surface, typically recharge during
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Aquifer Types Foundin Minnesota
Unconfined surficial driftaquifers, of water-table aquifers(Figure 2), exist mainly in sand andgravel and are widespread acrossmuch of Minnesota, especially thecentral and western regions. They aregood sources of water and arewidely used for agriculture anddomestic purposes (Clark et al.1995). These unconfined aquifers areclosely connected to the surface; theyrecharge from rainfall that seepsthrough the topsoil, and fromstreams, lakes, and wetlands wherewater filters into from above. Theycan also be recharged through inflowfrom other aquifers (MDNR 1997).Because water-table aquifers are notconfined by impermeable materials,they are often susceptible tocontamination from land-surfacesources, especially in Minnesota�scentral sand plains (Albin andBreummer 1986). Water-tableaquifers are also highly susceptible tochanges in climate patterns; whilethey are able to recharge relativelyquickly from seasonal rainfall andsnowmelt, they also experiencerapidly declining water levels duringtimes of drought and heavy use(MDNR 1997).
Buried drift aquifers, or buriedartesian aquifers, are sand and gravelaquifers that are generally confinedby a clay till overlay. Confined
aquifers are pressurized andconnected to the surface onlythrough interactions with othergroundwater aquifers or drilledwells. Buried artesian aquifers occurthroughout much of Minnesota andare a principal source of good-quality drinking water. In some areas,however, natural contaminants (suchas sulfates and chlorides) fromsurrounding rocks may inhibit theirusefulness for drinking water (Albinand Breummer 1986). Theirgeochemistry and interconnectionsare variable and not always wellunderstood (MDNR 1997).
Bedrock aquifers are characterizedby different rock types. Sedimentarybedrock aquifers, consisting largelyof sandstone, dolomite, andlimestone, are widely used insoutheastern and southwesternMinnesota for public andcommercial water supplies. Theseconfined aquifers are generally welldefined in their extent andconnection (MDNR 1997), with theimportant exception of karst areaswhere fractured limestone createsunknown interconnections amongaquifers and surface waters. Suchkarst areas are of concern becausecontaminants from surface watersmay flow quickly through fracturedrocks in local groundwater aquifers.The Prairie du Chien-Jordan, St.Peter, and Mount Siman-Hinckleyaquifers are important sedimentarybedrock aquifers that serve the Twin
Cities metropolitan area (Albin andBreummer 1996).
Crystalline bedrock aquifers, suchas igneous and metamorphic rocks,form the basement complex ofMinnesota�s aquifers. These confinedaquifers generally do not providelarge yields but are important in areaswhere there are no other aquifers,such as parts of northern Minnesota.For example, the Biwabik-IronFormation aquifer is the only sourceof groundwater for many towns innortheastern Minnesota (Albin andBreummer 1986).
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spring snowmelt and autumn rainfall.Drawdown generally occurs duringsummer months when groundwateraquifers provide water to growingplants and surface water bodies andfor various uses by people (e.g.,irrigation, lawn watering, MDNR1997). Aquifers also respond toyearly cycles of flooding anddrought, experiencing higher andlower levels during wet and dryyears. This fluctuation occurred inMinnesota during the wetter years ofthe early 1980s and the drought yearsof 1987-88 (MDNR 1989). Ingeneral, however, large and deepaquifers require extremely long timeperiods, perhaps centuries, to renewthemselves and do not respondrapidly to short-term changes on thesurface. Thus, groundwater is not
necessarily a �renewable resource�;depletion rates can exceed renewalrates when society�s water needssurpass an aquifer�s natural ability toregenerate.
Groundwater aquifers are diverse. Infact, Minnesota has 14 principalaquifers with different underlyinghydrogeologic features. There areseveral main kinds of aquifers thatare broadly characterized by theirconnection to the surface andsurrounding rock type. Aquifers maybe unconfined (water-table aquifersthat are closely connected to thesurface) or confined (generallydeeper aquifers separated by materialof low permeability such as clay;MDNR 1997). Aquifer types includeglacial drift (generally consisting ofsand and gravel), sedimentary rocks(such as sandstone and limestone),and crystalline rocks (such as deepigneous and granite; Albin andBreummer 1986). Aquifers are alsocharacterized by size and volume.Aquifers have a much wider areathan thickness, almost like layers ofpancakes beneath the earth�s surface.Aquifers can span a few squarekilometers to millions of squarekilometers. Thickness is generally intens of meters to hundreds ofmeters, rarely occurring beyond athousand meters. Such differencesmean that aquifers vary greatly intheir storage capacity, flow, andrenewal rates (Margat 1994).
The geology and hydrologic featuresof Minnesota�s aquifers havesignificant implications for theprotection and effective managementof the state�s surface andgroundwaters. In particular, wateruse in watersheds that overlay
shallow, unconfined aquifers musttake into consideration the closerelationships that can exist betweengroundwater and streams, rivers,lakes, and wetlands (Margat 1994).The aquifer�s connection to thesurface can determine its accessibilityfor drilling wells. In addition,surrounding rock type can affectwater chemistry. For instance, someaquifers have high concentrations ofdissolved solids or naturalcontaminants, which may inhibit theirusefulness for drinking water. Finally,knowledge of an aquifer�s size,volume, and interconnections maygive an indication of its ability tomeet long-term water needs.
Although in recent years we havelearned much more aboutMinnesota�s principal aquifers, inmany cases we still lack importantinformation about the extent,connection, and long-term availabilityof groundwater (IGWMCG 1995).Indicators of hydrogeologic featuresprovide essential backgroundinformation about Minnesota�sgroundwater system. For example,studies that track groundwater flowand recharge rates supplyinformation not only about anaquifer�s basic characteristics but alsoabout its potential to provideabundant clean water for the longterm. Studies that identifyhydrogeologic features such as age,origin, distribution, and the spatialrelationship of sediment andbedrock also contribute essentialgeological information aboutMinnesota�s aquifers (MGS andMDNR 1997). Identifyinghydrologic connectivity, orinterrelationships, between aquifersand surface water systems is also an
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important, although often difficult,task (Job and Simmons 1994;IGWMCG 1995).
PRESSURES ONGROUNDWATERRESOURCESGroundwater resources, like surfaceecosystems, may be altered bycumulative pressures. Groundwaterquantity can be affected by factorsthat deplete groundwater (e.g., use)or diminish its recharge (e.g.,changing rainfall patterns).Groundwater quality can be affectedby numerous sources ofcontamination (e.g., spills, runoff,leakages). Because undesirablechanges in aquifer quantity andquality (i.e., depletion andcontamination) can be difficult orimpossible to rectify, it is critical toconsider how various pressures,either singly or cumulatively, mightsurpass the natural ability of anaquifer to sustain itself over time.
UseBoth groundwater and surface watersources provide water forMinnesota�s needs. Major categoriesof water use include thermoelectricpower generation, public watersupplies, industrial processing,irrigation, and other miscellaneoususes. Groundwater is the majorwater source for public supplies andirrigation. Surface water is almost thesole source for power generation,and the major source for industrialprocessing (Figure 3). Localcommunities choose their watersources largely based on ease andcost of accessibility, which dependon surface and hydrogeologic
features. In the Twin Citiesmetropolitan area, for example,where the state�s most productivelimestone and sandstone aquifersoccur, two-thirds of public suppliesare from groundwater sources. In
the northeastern part of the state,where deep crystalline bedrockaquifers yield small amounts ofwater, most of the public supplycomes from surface water (Trotta1987).
Major Water Uses
Water users that withdraw more than1 million gallons per year require awater appropriation permit from theMinnesota Department of NaturalResources (MDNR). The MDNRuses the following categories to tracktrends in Minnesota�s water use:
Thermoelectric powergeneration�water used to coolpower generating plants. This ishistorically the largest volume useand relies almost entirely on surfacewater sources. Thermoelectric powergeneration is primarily anonconsumptive* use in that most ofthe water withdrawn is returned toits source.
Public water supply�waterdistributed by community suppliersfor domestic, commercial, industrial,and public users. This category relieson both surface water andgroundwater sources.
Industrial processing�water usedin mining activities, paper mill
operations, food processing, etc.Three-fourths or more ofwithdrawals are from surface watersources. Consumptive use variesdepending on the type of industrialprocess.
Irrigation�water withdrawn fromboth surface water and groundwatersources for major crop and noncropuses. Nearly all irrigation isconsidered to be consumptive use.
Other�large volumes of waterwithdrawn for activities including airconditioning, constructiondewatering, water level maintenance,and pollution confinement.
* Note: Consumptive use is definedas water that is withdrawn from itssource and is not directly returned tothe source. Under this definition, allgroundwater withdrawals areconsumptive unless the water isreturned to the same aquifer. Surfacewater withdrawals are consideredconsumptive if the water is notdirectly returned to the source so thatit is available for immediate furtheruse.
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In some situations multiple uses cancombine to cause groundwaterdepletion, especially during periodsof summer drought, whengroundwater levels naturally decline.This decline is compounded by peakdemands for irrigation, lawnwatering, air conditioning, industrialuses, and so on. Over the long term,increased population growth anddevelopment may also put addedpressures on groundwater systems.A variety of conservation actions andplanning efforts can help minimizepressures on Minnesota�s watersupplies. The most effectiveconservation measures are taken byindividual water users at the locallevel (MDNR 1989).
In addition, planning for growth anddevelopment must consider thelong-term availability of
groundwater and its ability to sustaina variety of water uses. It isimportant to recognize thatgroundwater supplies are notuniformly distributed and that someareas may not have enoughgroundwater to satisfy everyone�sneeds (MDNR 1989). Thus, localcommunities can work to ensure thatland-use patterns match groundwateravailability.
Indicators provide necessaryinformation for the developmentand implementation of water useplans. Indicators of water use areimportant to track because theyidentify pressures that depleteMinnesota�s groundwater resources.Coupling these indicators withinformation about groundwaterrecharge rates gives insights into thelong-term sustainability of theresource.
Alteration of groundwaterrechargeAltering the recharge rate ofgroundwater aquifers can put subtle,but long-term, pressure on our waterresources. When water moves slowlyacross the landscape, it naturallypercolates into soils andgroundwater aquifers. Land-useactivities that alter the natural flow ofwater, causing water to race acrossthe landscape, not only can result inflooding and droughts but can alsodiminish the amount of wateravailable to recharge groundwateraquifers. Removing plant cover,draining wetlands, separating riversfrom floodplains, and paving landcan all change the flow of wateracross the landscape. In theMississippi basin, for example,changes over the past 150 years havereduced the water-holding capacityof the soils by up to 70%(Abramovitz 1997). Such land-usechanges may diminish the ability ofgroundwater aquifers to naturallyrecharge over long time periods.
Drought also diminishesgroundwater recharge and can lowergroundwater levels. The effects ofdecreased water levels arewidespread, as evidenced by themidwestern drought of 1988(MDNR 1989). For example, manyirrigation permits were suspended,Minneapolis implemented its firstban on outdoor water use, 40 homesin Sherburne County were leftwithout water when wells went dry,and lakes and rivers dropped to all-time lows (MEQB 1991).
Global climate change may alsoaffect the use and recharge rate ofgroundwater aquifers. While the
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specific effects of global climatechange are not well understood,shifting rainfall patterns could alterstream flow and lake levels andaffect groundwater resources (USEPA 1997).
Indicators that track the potential forchanging recharge rates giveresearchers and managers insightsinto the long-term ability of anaquifer to meet society�s water needs.In general, however, these kinds ofindicators are not easy to interpretand need to be measured over longtime periods. For example, thedistribution and amount ofrainfall over time might helpdetermine if global climate change isaffecting regional weather patterns.And tracking land-use changes, suchas percent impervious surface,may also illustrate how water flowsacross the landscape are beingaltered.
ContaminationGroundwater contamination occurswhen contaminants seep throughsoils or enter groundwater aquifersthrough connections with streams,rivers, lakes, and wetlands. InMinnesota there are over 600,000potential sources of groundwatercontamination, ranging fromresidential septic tanks to state andfederal Superfund sites (Table 1).Potential sources of groundwatercontamination are associated withmany kinds of land-use activitiesincluding the following (MPCA1994):� Agricultural land use (fertilizers
and pesticides, animal feedlots)� Industrial and commercial land
use (hazardous materials, miningwastes)
� Municipal land use (urbanrunoff, landfills, sewage, roadsalts)
� Other sources (septic systemsand injection wells, undergroundstorage tanks, accidental spills)
These activities can introduce manycontaminants including nitrate,various chemicals, and pesticides.Natural contaminants (e.g., iron,manganese, and arsenic) are ofconcern in some parts of the state(MPCA 1994).
Groundwater contamination is oftenlocalized because some aquifers aremore susceptible to contaminationthan others. Water-table aquifers areclosely connected to the land surfaceand thus more likely to collectcontaminants that seep through
sandy soils. The central Minnesotasand plain aquifers are highlysusceptible to contamination by land-use activity such as irrigatedagriculture, septic systems, lakeshoredevelopment, unseweredcommercial and industrialdevelopment (IGWMCG 1995).And in the northern lakes regionshallow aquifers connected towetlands can be contaminated byseptic tanks and lakeshore residences(IGWMCG 1995). Bedrock aquifers,though often protected by confininglayers that impede contaminant flow,may be contaminated when theyoccur close to the surface. They arealso highly susceptible in karst areas,where fractured rocks close to thesurface allow contaminants to flowquickly into confined aquifers (Albinand Breummer 1986). Karst aquifers
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in southeastern Minnesota aresusceptible to contamination fromindustrial, municipal, and agriculturalfacilities (IGWMCG).
Because some groundwater aquifersare naturally susceptible tocontamination, the only way toensure high-quality drinking suppliesis to limit the amount ofcontaminants entering thegroundwater system. This does notrequire that all chemical use shouldbe eliminated; many activities that usechemicals are integral parts ofMinnesota�s economy. For example,midwestern farmers produce about80% of the nation�s corn andsoybean crops. At the same time,however, agricultural land-usepractices can introduce contaminantsinto groundwater. Thus, programsthat work with farmers to managefertilizer and pesticide applicationhelp protect the quality ofMinnesota�s groundwater (USDA1994). And many options exist forreducing or eliminating pesticides inagriculture.
Whatever the use, agricultural,industrial, or municipal, it is necessaryto consider how to meet the needsof these activities while at the sametime protecting groundwater
resources. Efforts to reducegroundwater contamination focus infour areas (Job and Simons 1994):� Reduce or eliminate pollution� Recycle residuals� Stimulate proper treatment� Mediate safe disposal
There are many programs that workwith industries, businesses, andmunicipalities to help implementthese approaches to preventgroundwater contamination. TheMinnesota Office of EnvironmentalAssistance provides technicalassistance and grants to helpbusinesses properly manage theirwaste. Farm programs target effortsto better manage pesticides andfertilizers. And there are a range ofactions that individual citizens cantake to reduce pollution and thepossibility of groundwatercontamination.
All of these approaches are criticalbecause groundwater contaminationis extremely difficult to remedy.While groundwater aquifers do haveself-purifying processes that can helpimprove water quality in some cases,these natural processes are extremelyslow. Thus, once pollutants havereached aquifers, they generally haveextremely long residence times, andin high enough concentrations canthreaten groundwater quality(Notenboom et al. 1994).
Indicators that measure contaminantsinform local communities aboutpotential problems and highlightareas where management actions arenecessary. Indicators of problem
contaminants include groundwaterconcentrations of nitrate, volatileorganic compounds, and heavymetals. And indicators of naturallyoccurring contaminants (e.g.,concentrations of manganese,chloride, and arsenic) givecommunities baseline informationabout the availability of cleandrinking water from area aquifers. Itis also important to identify potentialsources of contaminants. Indicatorsrelated to human activities include,for example, the percentage ofpetroleum tanks not incompliance, the density of septicsystems in susceptible areas, andthe number of contaminated sites.
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GROUNDWATERRESOURCESSTATUS ANDTRENDSMinnesotans are concerned about thestate�s water resources, especiallygroundwater quality. In 1996, theMinnesota Pollution Control Agency(MPCA) held a series of regionalfocus groups to better understandwhat Minnesota citizens think aboutkey environmental issues.Groundwater contaminationsurfaced as the largest concernamong these group participants,probably because people readilyunderstand the link betweengroundwater quality and humanhealth. People were especiallyconcerned about practices that canintroduce contaminants intogroundwater, and how thesecontaminants might affectgroundwater suitability for drinkingand other uses (MPCA 1996a).
What are the actual trends ingroundwater contamination? Areconcerns justified? And dogroundwater resources have thecapacity to continue serving growingwater needs? There are no simpleanswers because Minnesota has acomplex groundwater system, andthe most serious problems areusually localized (Albin andBreummer 1986). It is difficult tomake generalizations whenMinnesota�s 14 principal aquifersvary considerably in hydrogeologicfeatures and susceptibility tocontamination or depletion.However, statewide monitoringstudies give insights into trendsacross Minnesota�s groundwater
aquifers, thus providing essentialbaseline information for both localand statewide decision makers(MPCA 1998).
Groundwater quantity:trends in water useAbundant surface and groundwatersupplies fueled Minnesota�s earlycommerce and settlement. Waterresources supported the loggingindustry, railroad transportation,mining, and agriculture in the late1800s. Groundwater use expandedthroughout the 1900s for industry,urban domestic uses, and agriculture.For example, agricultural irrigationbegan in Minnesota in the 1920s andexpanded gradually until the 1970s,when a combination of drought,grain prices, and government policiesencouraged farmers to obtain
permits for on-farm wells. Irrigationexpanded dramatically between 1975to 1980 (Trotta 1987). Groundwateruse for irrigation (Figure 4) has beenmore stable since then, althoughthere were increases during thedrought in the late 1980s anddecreases during wetter years in theearly 1990s (MDNR 1989, 1991,1993, 1995, 1997).
Groundwater also provided waterfor basic needs (e.g., drinking water)of Minnesota�s growing population.By the turn of the century thousandsof wells were being drilled to supplythe largely rural population. Sincethen, population growth, especially inthe seven-county metropolitan area,has continued to place demands onMinnesota�s water resources (Trotta1987). Use of groundwater has
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dramatically increased. Whenmonitoring of this resource began in1950, about 100 billion gallons ofgroundwater were used annually.During the past decade, around 200billion gallons of groundwater havebeen used each year. This amounthas fluctuated during wet and dryyears; for instance, 247 billion gallonswere extracted during the drought of1988 (Figure 5). There are concernsthat increased demands may strainavailable groundwater resources.Groundwater does not adhere topolitical boundaries, and as a result,
competition for groundwater in theabsence of cooperative planning,especially in growing urban areas,may put a strain on this resource(MEQB 1991).
Groundwater quantity:trends in water levelsMonitoring groundwater levelsensures that current uses are notdepleting Minnesota�s aquifers. TheU.S. Geological Survey and theMDNR have cooperated onmonitoring groundwater levels since1947. The earliest groundwater level
information dates from 1942.Baseline levels before settlement areunknown. Currently, water levels aremeasured in aquifers across the state.These data are compared to datataken during the past 15 to 30 years.Groundwater levels are naturallydynamic over time and reflect yearlychanges in climate patterns, such asdrought and flood years; forexample, in Minnesota groundwaterlevels were low during the droughtof 1988, and above average for theflood years of 1986 and 1993(MDNR 1989, 1995).
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In general, groundwater hasremained fairly stable across the state,although some areas in westernMinnesota and in the Twin Citiesmetropolitan area have showndeclines. A Minnesota Water YearData Summary reports that, ingeneral, water levels were aboveaverage for 1995 and 1996 due toabove-average levels of precipitation.However, specific wells showedwater level declines, suggesting thatlarge amounts of water use may beaffecting area aquifers (MDNR1997). Two of four wells thatmeasure water levels in buriedartesian aquifers in the Twin Citiesmetropolitan area were belowaverage for both 1995 and 1996, andone of six wells measuring waterlevels in the Mount Simon aquiferhas been experiencing declines since1980. It is possible that largeamounts of use from bedrockaquifers may be having an impact onlocal buried artesian wells;interconnections among theseaquifers are poorly defined, and thusrecharge rates are difficult to predict(MDNR 1997). Use for irrigationmay also have localizedimpacts on water levels (MDNR1997). While underlying bedrockaquifers have large supplies of water,the long-term impact of urban wateruse on water levels in the Prairie duChien-Jordan and Mount Simonaquifers is not known (IGWMCG1995).
Water quality: trends inoutput sourcesMany sources contribute togroundwater and surface watercontamination, including landfills,hazardous waste, Superfund sites,underground storage tanks, septicsystems, feedlots, and other land-useactivities which are non-point sourcesof pollution (MPCA 1994).Minnesota has made significant gainsin reducing point-source pollutionfor both groundwater and surfacewater. And while much progress hasbeen made in addressing theproblem of nonpoint sources ofpollution (such as runoff from farmfields, urban areas, golf courses), itremains a challenge.
LandfillsGroundwater contamination fromlandfills has been widespread. In1988 at least 37 sites had inorganic ororganic contaminants in excess ofdrinking water standards (MEQB1988), and 19 had levels ofcontaminants above normal thatwere attributed to leachate fromlandfills. In recent years newmeasures, including liners and capsfor landfills and leachate collectionsystems, have reduced the impacts oflandfills on groundwater supplies(Figure 6). The MPCA worked toinstall up-to-date pollutionprevention measures in old landfillsby 1995, and to introduce moderndisposal facilities in any new landfills.These two measures are estimated toreduce leachate entering groundwaterfrom 56 million to 15 million gallonseach year (MPCA 1995b).
Hazardous wasteInspections of hazardous wastegenerators in 1994 showed thatabout 80% were properly managed,and about 70% had proper storage.The MPCA has historically focusedregulatory efforts on large producersof hazardous waste. New educationefforts are being focused at verysmall quantity generators, often smallbusinesses that may inadvertentlymishandle their waste. The MPCAtrained 4,500 individuals inhazardous waste management during1992-94 (MPCA 1995b).
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Superfund sitesContaminated sites also cancontribute to groundwatercontamination. While cleanup isdifficult and costly, progress hasbeen made. Eighteen sites werecleaned up and removed from thelist during 1991-94 (MPCA 1995b).More recently, over 140 of about180 sites are in some stage ofinvestigation or cleanup. TheVoluntary Investigation and Cleanup
Program also lists hundreds of sites,which do not necessarily legallyrequire cleanup. In this programowners or responsible parties canclean up their property more quicklyand with fewer legal costs than in thetraditional Superfund program.More than 50 of these cleanups havealready been completed (MPCA1994).
Underground storage tanksAn estimated 32,000 undergroundstorage tanks occur throughoutMinnesota. Underground tanks arecommonly used for storing fuel forgasoline stations, industries andschools. If not properly maintained,such tanks eventually develop leaksthat may introduce benzene andother carcinogens into groundwatersupplies. Leaking tanks have beenreported across the state and aremost common in the Twin CitiesMetropolitan Area (Figure 7).Increased understanding of theproblems associated withunderground tanks, along withincreased monitoring and repair, hasresulted in rapid cleanup after a leakand more effective early detection ofproblems. Since 1990, the number oftank leaks reported has decreaseddramatically (Figure 8). Despiteimprovements, however, it is still achallenge to prevent leaks in all ofMinnesota�s 32,000 tanks. Federalstandards introduced in 1993 requirethat all tanks larger than 1,100 gallonshave leak-detection devices. A recentinspection by the U.S. EnvironmentalProtection Agency, whichfocused on larger-sized undergroundtanks in Minnesota, showed thatabout two-thirds of inspected tankswere in violation of federalrequirements. This suggests thatpreventative measures still need to betaken to ensure that undergroundtanks will not leak.
Septic systemsAround 500,000 household septicsystems and 100,000 nonresidentialseptic systems (called Class Vinjection wells) exist across the stateof Minnesota. Household septicsystems pose significant concerns
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because they are so common and areoften not properly maintained; 70percent of the household septicsystems are estimated to benoncompliant with current guidelines(MPCA 1994). Regulations exist totry to bring old septic systems incritical areas up to current standardsand to address other sources of non-point source pollution. But becausethere are so many septic systems, andthe cost of repair or replacement ishigh, they remain a problem(Vonmeier 1996). One county waterplan warns that approximately 4,000households in the county are usingseptic systems that have beeninstalled without inspection or soilinvestigation (MEQB 1991). Similar
situations are common across thestate. Currently many septic systemsare being installed in unsewereddeveloping areas and alonglakeshores.
FeedlotsAcross the state there are anestimated 50,000 feedlots.Traditionally many operated withoutpermits from the MPCA. In 1988,there were about 1,200 feedlots inOlmsted County alone, and only 133of these had MPCA permits(MEQB 1991). In recent years,however, much attention has focusedon feedlots because of concerns overwater and air quality. For example,spills or runoff from hog manurehave been linked to streamcontamination and fish kills, and haveraised concerns about groundwatercontamination in karst areas. Yet,people also recognize the importantrole that feedlots can play in localcommunities. Studies and forumsthat involve stakeholders arecurrently addressing environmentalconcerns.
Runoff from multiple sourcesMost widespread, and perhaps mostdifficult to control, are nonpointsources of pollution, which canreadily cause low-level contaminationof local aquifers. Sources includeboth agricultural and urban runoffcontaining fertilizers used in farmfields, lawns, and golf courses; road-salt runoff; and human waste leakingfrom residential and nonresidentialseptic systems. The potential forpollution from nonpoint sources isespecially high in the Twin Citiesmetropolitan region and southernparts of the state (MEQB 1991).Urbanization has already caused
widespread low-level contaminationof upper aquifers (IGWMCG 1995).
Trends in groundwaterqualityNumerous studies trackcontaminants in Minnesota�sgroundwater system. Of particularconcern are those substances thatpose a human health threat, such asnitrate, volatile organic compounds(VOCs), and pesticides. Of these,nitrate is by far the most widelydistributed chemical associated withhuman activity (MPCA 1998); it isalso the most widespreadgroundwater pollution problem inthe United States (US EPA 1996).
NitrateNitrate in groundwater is a seriousconcern because it is dangerous tohuman health, causing blue babydisease in infants, and it is also themost common contaminant found indrinking water. Sources of nitratecontamination include septic systems,landfills, fertilizers, and manure fromfeedlots (US EPA 1996). Nitratecontamination occurs across theentire state. In general, however,elevated nitrate concentrations aremost common in agricultural areasthat overlay susceptible groundwateraquifers (Figure 9), such as the sandaquifers of central and southwesternMinnesota and the karst regions insoutheastern Minnesota (MEQB1991).
A Minnesota Department of Healthstudy of nitrate showed that 7% ofprivate water wells exceeded thenitrate Health Risk Limit (HRL) of10 mg/l. And the MPCA�s GroundWater Monitoring and Assessment
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Program (GWMAP) showed that4% of random sampling stationsacross Minnesota�s principal aquifersexceeded the HRL criteria. It isdifficult to make broad-scalegeneralizations, especially becausenitrate contamination is notdistributed equally across Minnesota�saquifers. In water-table aquifers, forexample, 10% of samples exceededHealth Risk Limits. Deeper aquifersoften show lower levels; none of thesamples in the Saint Peter and Jordan
aquifers exceeded HRL criteria in1994. GWMAP data suggest thatHRL exceedances for nitrate havenot changed dramatically in the lastdecade; some aquifers showincreases in nitrate concentrationswhile others show decreases incomparison to samples taken in 1985(Clark et al. 1995). Local water-testing clinics sponsored by theMinnesota Department ofAgriculture help individuals andcommunities identify potential
problems due to nitratecontamination.
Volatile organic compoundsVolatile organic compounds (VOCs)are potential carcinogens when theyoccur in high levels in groundwater.VOCs can seep into groundwaterfrom leaking underground fuel tanks,industrial sites, and landfills.Improper disposal of industrial andhousehold products such as paintthinners, cleaners, refrigerants,varnishes, detergents, and severalother chemical compounds, cancontribute to this problem (MEQB1988). Efforts to reduce point-source pollution and improve wastedisposal have likely limited recentcontamination of Minnesota�sgroundwater. Of 356 randomlyselected wells sampled in 1992-93,41 showed VOCs present at lowlevels, and only two wells had VOClevels exceeding the RecommendedAllowable Limit (RAL) (MPCA1994).
PesticidesPesticides are widely used toimprove crop production but poseconcerns for drinking water safety,especially near aquifers that arenaturally susceptible tocontamination. Potential sources ofcontamination include spills andimproper disposal of unusedpesticides and pesticide containers(MPCA 1994). Pesticidecontamination is not as widespreadas nitrate contamination. In water-table aquifers where nitratecontamination occurs mostfrequently from agricultural activities,wells were below state health risklimits for pesticides (MPCA 1995).But pesticides remain a concern in
Percent of wellsamples exceedinghealth risk limit bygroundwaterregion
0 - 1%
2 - 5 %
16%
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older, shallow wells in karst areas insoutheastern Minnesota (IGWMCG1995).
Naturally occurring contaminantsNaturally occurring contaminantsinclude sodium, chloride, arsenic,sulfate, iron, manganese, and others.While much of Minnesota�sgroundwater is naturally of goodquality, some areas exhibit high levelsof contaminants from surroundingrocks and sediments (IGWMCG1995). For example, salinegroundwater occurs in areas alongLake Superior�s northern shores, indeep aquifers in southeasternMinnesota, and along the state�swestern border (Albin andBreummer 1986). Iron andmanganese also occur in high levelsthroughout the state, and cause watertaste problems. High levels of ironand manganese are often removedthrough filtration or softeningdevices (MPCA 1994).
Well and drinking water advisoryareasWhen groundwater contamination isknown, the Minnesota Departmentof Health issues well and drinkingwater advisories. More stringentregulations for the construction,reconstruction, and sealing of wellsapply in areas with well advisories. In1994 six well advisory areas weredue to contamination from VOCs.About 320 drinking water wells hadunhealthy levels of contaminationbetween 1989 and 1994 (MPCA1994). Residents depending on thesewells had to look elsewhere fordrinking water supplies, a situationthat illustrates how contamination hasreal-life implications for Minnesotacitizens.
GROUNDWATERMONITORINGBecause groundwater is such animportant resource for Minnesota,many state and local agenciesregularly collect and analyze data onMinnesota�s groundwater. TheInteragency Ground WaterMonitoring Coordination Group(IGWMCG) helps coordinatemonitoring efforts (MPCA 1996c).Many monitoring efforts arenecessary because the state�sgroundwater system is complex anddynamic.
Monitoring of wells is the best wayto gain information aboutMinnesota�s groundwater system.The MDNR monitors about 700observation wells across the state andrecords water-level changes due toseasonal and long-term pumping orclimatic effects (MDNR 1997). Inaddition, stream-flow gauges helpdetermine groundwater discharges.The MDNR and the MinnesotaGeological Survey have also beenworking with county staff togenerate detailed maps (Figure 10)that focus on importanthydrogeologic features, such asgroundwater flow systems andpollution sensitivity (MGS andMDNR 1997).
Groundwater quality is monitoredprimarily by the MinnesotaDepartment of Agriculture (MDA)and the MPCA. MDA�s GroundWater Monitoring Program evaluatesthe impact of agricultural chemicalson groundwater quality. Theprogram utilizes geologic andhydrologic information to determinethe susceptibility of regions to
contamination and provides keyinformation about the relationshipsbetween agricultural land use andgroundwater quality.
The MPCA�s Ground WaterMonitoring and AssessmentProgram (GWMAP) recentlycompleted a five-year water qualitystudy of Minnesota�s principalaquifers, using 954 wells across thestate (MPCA 1998). GWMAP�sapproach includes several keycomponents. A baseline assessmenthelps local resource managers andinterested citizens interpret site-levelresults by comparing them tostatewide trends (MPCA 1998).Ambient monitoring tracks large-scale trends (e.g., statewide trends ingroundwater quality), while probleminvestigation focuses on specificissues of concern (e.g., problemchemicals in local areas).Effectiveness monitoring helpsdetermine how well certain strategiesare addressing specific problems(e.g., success of cleanup strategies).
All of these groundwater monitoringprograms are tools that help localand statewide decision makersmanage our state�s water resources.It is important to note, however, thatwe still lack a complete picture ofour groundwater resources, andmany questions remain (MEQB1991). For example, the long-termimpacts of urbanization ongroundwater quality and quantity inthe Twin Cities, St. Cloud, andBrainerd areas are unknown. Doesgroundwater quality respond to bestmanagement practices and pollutioncontrol measures that have beenimplemented in karst regions ofsoutheastern Minnesota? Will heavy
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pumping of shallow aquifers innorthwestern Minnesota causeupwellings from deeper aquifers andintroduce natural contaminants?How are aquifers and streams, lakes,and wetlands related? And willincreased pumpage affect streamflows and stream quality across thestate? Ongoing monitoring and
groundwater studies will provideadditional insights into these kinds ofimportant management issues(IGWMCG 1995).
EXISTING POLICIESAND PROGRAMSBefore the 1980s, regulationspertaining to groundwater werelimited and addressed groundwaterissues indirectly. The impacts ofaboveground activity ongroundwater resources were notwidely understood. Since then, manylaws and policies have beendeveloped to protect groundwaterresources. Federal and state agenciesfocus on regulation and permitting,responses to spills, management andplanning, monitoring and research,and education. And localgovernments develop WaterManagement Plans.
At the federal level, standards forsafe drinking water are established bythe federal Safe Drinking Water Act(US EPA 1996). The U.S.Environmental Protection Agency�sComprehensive State Ground WaterProtection Programs Initiativeprotects the nation�s groundwaterresources with environmentalprograms and funding of stateactivities. The Wellhead ProtectionProgram works with state and localgovernments to manage public wellsupplies in areas that may besusceptible to contamination. Inaddition, the Natural ResourcesConservation Service of the U.S.Department of Agriculture focuseson conservation of natural resourceson private lands, with an emphasison protecting surface water andgroundwater quality. The U.S.Geological Survey�s National WaterQuality Assessments (NAWQA)determines long-term trends insurface water and groundwaterquality.
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At the state level, the Ground WaterProtection Act (1989) aims tomaintain groundwater free ofhuman-induced pollutants; the actsupports projects that monitorgroundwater and help controlchemical inputs (MPCA 1994). Lawspassed in 1990 help maintaingroundwater supplies. For example,certain kinds of heating and airconditioning systems that usedexcessive amounts of groundwater,especially in the Twin Citiesmetropolitan area, must be phasedout by the year 2010 (MDNR 1997).
Numerous agencies havecomplementary responsibilities forprotecting Minnesota�s groundwaterresources. The MDNR administersprograms related to water use andwater quantity. The MPCA and theMinnesota Department ofAgriculture implement programs toprotect groundwater quality. TheMinnesota Department of Healthfocuses on maintaining safe wells anddrinking water (MPCA 1995a).Other programs provide assistanceas well. For example, the MinnesotaOffice of Environmental Assistanceworks with small businesses toreduce pollution.
At a local level, Water ManagementPlans evaluate groundwater resourcesand improve management practicesfor protecting supply in nearly allcounties. The Clean WaterPartnership, established in 1987,provides local units of governmentwith resources to protect waters. Theproject promotes data collection,diagnostic analysis, and funding forareas needing protection. And theMinnesota Geologic Survey and theMDNR provide local areas withgroundwater information throughthe County Geologic Atlas andRegional Hydrogeologic AssessmentProgram (MGS and MDNR 1997).
A challenge for all these programs ismaintaining a focus on hydrologic,and not political, boundaries. Forgroundwater, the unit is the aquifer.Without looking at all the land andwater uses that affect an aquifer, it isunlikely that we will succeed inprotecting it (MEQB 1991).
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EXAMPLEINDICATORSTable 2 collects the indicators used inthis chapter. The indicators areorganized within the EII frameworkto illustrate the relationships betweenhuman activities, environmentalcondition, the flow of benefits from
the environment, and strategies forsustaining a healthy environment. Theindicators used in this chapter areexamples that illustrate howindicators may help assess thecondition of Minnesota�sgroundwater resources. Many ofthese indicators are currently trackedby agencies that are a part of the
Interagency Ground WaterMonitoring Coordination Group(IGWMCG). The EII works toensure that groundwater indicatorsare also related to indicators forMinnesota�s ecosystems.
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REFERENCESAbramovitz, J. 1997. Valuing nature�sservices. Pages 95-114 in L. Brown,C. Flavin, and H. French, eds., Stateof the World 1997. W. W. Nortonand Company, New York.
Albin, D. R., and L. B. Breummer.1986. Minnesota: Groundwaterquality. U.S. Geological Surveywater-supply paper 2325. U.S.Geological Survey, St. Paul.
Clark, T., Y. Hsu, and J.Schlotthauer. 1995. Ground WaterMonitoring and AssessmentProgram: A compilation of analyticaldata for 1994. Minnesota PollutionControl Agency, St. Paul.
Interagency Ground WaterMonitoring Coordination Group(IGWMCG). 1995. RegionalGround Water Profiles. MPCA,MDA, MDNR, MDH, LMIC,MGS, and USGS, Minnesota.
Job, C. A., and J. J. Simons. 1994.Ecological basis for management ofgroundwater in the United States:Statutes, regulations, and a strategicplan. Pages 523-40 in J. Gibert, D.Danielopol, and J. Stanford, eds.,Groundwater ecology. AcademicPress, San Diego.
Margat, J. 1994. Groundwateroperations and management. Pages505-22 in J. Gibert, D. Danielopol,and J. Stanford, eds., Groundwaterecology. Academic Press, San Diego.
Minnesota Department of NaturalResources (MDNR). 1989. Droughtof 1988. Minnesota Department ofNatural Resources, Division ofWaters, St. Paul.
_____. 1991. Water year datasummary 1989 and 1990. MinnesotaDepartment of Natural Resources,Division of Waters, St. Paul.
_____. 1993. Water year datasummary 1991 and 1992. MinnesotaDepartment of Natural Resources,Division of Waters, St. Paul. _____.1995. Water year data summary 1993and 1994. Minnesota Department ofNatural Resources, Division ofWaters, St. Paul.
_____. 1997. 1995 and 1996 wateryear data summary. MinnesotaDepartment of Natural Resources,Division of Waters, St. Paul.
Minnesota Environmental QualityBoard (MEQB). 1988. Minnesotaenvironmental quality: Trends inresource conditions and currentissues. Minnesota EnvironmentalQuality Board, St. Paul.
_____. 1991. Minnesota water plan:Directions for protecting andconserving Minnesota�s waters.Minnesota Environmental QualityBoard, St. Paul.
Minnesota Geological Survey (MGS)and Minnesota Department ofNatural Resources (MDNR). 1997.County Geologic Atlas and RegionalHydrogeologic Assessment Program.Minnesota Geological Survey andMinnesota Department of NaturalResources, St. Paul.
Minnesota Pollution Control Agency(MPCA). 1994. Minnesota waterquality: Report to the Congress ofthe United States, water years 1992-1993. Minnesota Pollution ControlAgency, St. Paul.
_____. 1995a. Groundwater: Adirectory of Minnesota�s programsand resources. Minnesota PollutionControl Agency, St. Paul.
_____ . 1995b. MPCA: Trackingour progress in protectingMinnesota�s environment. MinnesotaPollution Control Agency, St. Paul.
_____. 1996a. Minnesotaenvironmental priorities projectfocus groups. Minnesota PollutionControl Agency, St. Paul.
_____. 1996b. ProtectingMinnesota�s environment: A progressreport. Minnesota Pollution ControlAgency, St. Paul.
_____. 1996c. Status of groundwater monitoring and water qualitytrends in Minnesota. Report to theLegislative Commission onMinnesota Resources. MinnesotaPollution Control Agency, St. Paul.
_____. 1998. Baseline water qualityof Minnesota�s principal aquifers.Minnesota Pollution Control Agency,St. Paul.
Notenboom, J., S. Plenet, and M. J.Turquin. 1994. Groundwatercontamination and its impact ongroundwater animals andecosystems. Pages 477-504 in J.Gibert, D. Danielopol, and J.Stanford, eds., Groundwaterecology. Academic Press, San Diego.
Trotta, L. C. 1987. Minnesota: Watersupply and use. U.S. GeologicalSurvey water-supply paper 2350.U.S. Geological Survey, St. Paul.
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U.S. Department of Agriculture(USDA). 1994. The impacts:Management Systems EvaluationAreas (MSEA) integrated researchand education for clean water.USDA Cooperative State Research,Education, and Extension Service.Special project number 94-EWQI-1-9055.
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