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Smith, CGWP Consulting Hydrogeologist, Smith-Comeskey Ground Water Science, Ada, Ohio GROUNDWATER SOURCE QUALITY: RELATIONSHIP WITH SURFACE WATER AND REGULATION The topic of groundwater

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CHAPTER 4 SOURCE WATER QUALITY

MANAGEMENT GROUNDWATER Stuart A Smith, CGWP

Consulting Hydrogeologist, Smith-Comeskey Ground Water

Science, Ada, Ohio

GROUNDWATER SOURCE QUALITY:

RELATIONSHIP WITH SURFACE WATER

AND REGULATION

The topic of groundwater source quality is a complicated one, with numerous ences, both natural and human in origin Aside from frequently being more accessi-ble (drilling a well near a facility is often more convenient than piping in surfacewater from a remote location), groundwater is typically chosen because its naturallevel of quality requires less treatment to ensure safe, potable consumption byhumans Although many groundwaters benefit from aesthetic treatment, and some-times from treatment to remove constituents such as metals and arsenic that poselong-term health risks, in general groundwater sources compare favorably againstsurface water due to the reduced treatment needed In the dangerous modern world,groundwater sources are far less vulnerable to terrorist attack than surface waterreservoirs, just as they were recognized as being less vulnerable to nuclear falloutduring the political atmosphere of the 1950s and 1960s

influ-Arguably, surface water and groundwater form a water resource continuum inany hydrologic setting (e.g., Winter et al., 1998), and from a groundwater-biasedview, surface water bodies are often simply points where the water table rises abovethe surface Thus impacts on one part of this continuum can affect the other overtime However, the hydraulic connections between these two resources can beobscure (at least superficially), and surface water and groundwater managementstrategies in the United States (regulatory issues are discussed in Chapter 1) tend tofollow different paths

Surface water management assumes that the source is impaired and unsafe forconsumption without elaborate treatment (a point not always conceded wheresource surface waters are of high quality, such as in Portland, Oregon, and New York

4.1

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City) By contrast, because the advantages of groundwater include a perceivedreduced vulnerability and need for treatment, groundwater protection strategies,such as those in the United States, have traditionally focused on protection of thatquality This approach (and a procedural defeat for artificial separation of ground-water and surface water) is belatedly being reflected in the U.S regulatory sphere inthe change to source water assessment and protection instead of “wellhead protec-tion” and “surface water rules” as separate emphases.

However, experience of the last several decades has shown that groundwatersources are not uniquely immune to contamination, and that once contaminated bychemical or radiological agents, they are almost always difficult to clean up.Recently, attention has refocused on the risk of pathogen transport to wells A com-mon conclusion of all groundwater contamination research is that prevention is farmore effective than remediation or treatment in assuring the quality of groundwatersupply sources Prevention takes the form of management

The intent of this chapter section is to introduce the reader to influences ongroundwater quality, management options, and tools to improve understanding ofthe groundwater resource and thus improve its management and protection as itrelates to water supply

GENERAL OVERVIEW OF GROUNDWATER

SOURCES AND IMPACTS ON THEIR QUALITY

The key to understanding and managing groundwater quality in water supply ning is to understand that both aquifer hydrologic characteristics and the causes andeffects of groundwater contamination are complex and highly site-specific Ground-water quality management is most effective when it can respond to the specifics ofindividual aquifers, wellfields, and even individual wells

plan-For example, in both porous media (sand/sand-and-gravel/sandstone) and fractured-rock aquifers, hydraulic conductivity and its derivative values can vary

by orders of magnitude over short distances (meters to kilometers) Flow ties can also vary by similar dimensions over meter differences horizontally andvertically Pressure changes near a well may cause flow characteristics to vary sig-nificantly in a distance of one meter away from the well

veloci-Changes in each of the just-mentioned hydrologic characteristics can affectgroundwater quality by changing local constituent concentrations Likewise, local-ized differences in formation geochemistry (e.g., organic content, iron, and othermineral transformations) affect water quality A third factor is the influence of theaquifer microflora in a specific fracture or aquifer zone tapped by wells Work in thelast 20 years has revealed the extent and complexity of the microbial ecosystems thatinhabit aquifers (e.g., Chapelle, 1993; Amy and Haldeman, 1997)

The extent of human impact also depends on (1) how potential contaminants arehandled; (2) the physical-chemical characteristics of such materials if they are released

to the ground; and (3) the hydrologic characteristics of the location where a releaseoccurs If the soil has a low hydraulic conductivity, contamination may be very limited,even if application (e.g., oil spills or herbicides) is relatively intense On the other hand,

if conductivity is high and there is a direct contact with an aquifer, a small release mayhave a large impact A further human impact is the presence of abandoned wells orother underground workings that provide conduits through low-conductivity soils.All of these factors are site-specific, but they can be understood and managed ifidentified Thus, effective water supply management of source groundwater (and

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avoiding unnecessary treatment) depends on adequate local knowledge of thegroundwater system being utilized.

Types of Aquifer Settings in North America

and Their Quality Management Issues

North America has vast and widely distributed groundwater resources that occur inmany types of aquifers (see Figure 4.1) In addition to this hydrogeologic variety,North America offers extreme variability in climate and degree of human develop-ment From the standpoint of groundwater development, these range from areas ofabundant groundwater and very low population density in western Canada to highpopulation densities in urban centers in the dry southwestern United States andnorthern and central Mexico, where groundwater overdrafts are an important watermanagement problem

Large areas of the central and western United States (like large regions of theworld) and Mexico struggle to effectively and equitably manage groundwaterresources that could very easily become depleted by overuse Prominent examplesinclude the decades-long efforts to manage the Edwards aquifer in Texas, and theOgallala aquifer, which spans the central United States east of the Front Range of the Rockies In the long term, questions must be asked, such as how sustainable is thehigh-water-use, technological civilization in the desert U.S West (established during a200-year historically wet period)? What kind of population density is sustainable on

FIGURE 4.1 (a) Groundwater regions of the United States (Source: Van der Leeden, Troise, and

Todd 1990 Originally from R C Heath “Classification of ground-water regions of the United

States.” Ground Water, 20(4), 1982 Reprinted with the permission of the National Ground Water

Association.)

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[Abbreviations: (1) Aquifers: P, principal aquifer in region; I, important aquifer in region; M, minor aquifer in region; U, unimportant as an aquifer in region.

(2) Rock terms: S, sand; Ss, sandstone; G, gravel; C, conglomerate; Sh, shale; Ls, limestone; Fm, formation; Gp, group.]

de-Highly developed with local depletion.

Storage large but perennial recharge limited—P.

S and G posits especially in northern part of region and

de-in some leys—I.

val-S and G posits along streams, interbedded with basalt—I to M.

de-S and G outwash, especially in Spo-kane area—I.

U

S and G along water courses.

Sand dune deposits—P (in part).

S and G outwash, much of it reworked (see above)—I.

in terrace deposits—I (limited).

S and G outwash especially along northern bound- ary of region—I.

S and G along water courses—M.

S and G outwash, terrace deposits and lenses in till throughout region—P (in part).

S and G outwash in northern part Not highly developed—M.

S and G outwash, terrace deposits and lenses

in till.

Locally highly

S and G along water courses and

in terrace and littoral deposits, especially in the Missis- sippi and tributary valleys Not highly developed

in East and South.

Some tion in Gulf Coast—I.

deple-S and G outwash in Mississippi Valley (see above)—I.

The most widespread and important aquifers in the United States Well over one- half of all groundwater pumped in United States is withdrawn from these aquifers Many are easily available for artificial recharge and induced infiltration Subject to saltwater

S and G along water courses and in terrace deposits Not developed.

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Alluvial Fm and other

basin deposits in the

south-ern part—M to P (see

Allu-vium above).

tion in coastal areas.

contamina-Aquifers in coastal areas subject to saltwater encroach- ment and contamination.

Coquina, limestone, sand, and marl Fms in Florida—M.

Dewitt Ss

in Texas ronelle and LaFayette Fms in Gulf States—I.

Cit-New Jersey, Maryland, Delaware, Virginia—

Cohansey and Calvert Fms—I.

Delaware

to North Carolina—

St Marys and Calvert Fms—I.

U

Ellensburg

FM in ington—I;

M to I.

Ogalalla

Fm in High Plains.

Extensive S and G with huge storage but little recharge locally.

Much tion—P (in part).

deple-Arikaree Fm—M.

U

Flaxville and other terrace deposits S and G in northwest- ern part—

U

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Ss, and Tohatchi Sh

in northwest Arizona and northeast New Mex- ico—M.

Brule clay, locally—I;

Gp in ern Illinois (?), Ken- tucky, and Missouri—

south-M; where—U.

Tampa Ls, Alluvium Bluff Gp, and Tami- ami Fm—I.

Eastern Texas—

Oakville and Cata- houla Ss—I.

Suwannee

Fm, Byram

Ls, and Vicksburg Gp—I.

New Jersey, Maryland, Delaware, Virginia—

Pamunkey Gp—I.

North olina to Florida—

Car-Ocala Ls and Castle Hayne

Includes the principal formations (Ocala

Ls, cially) of the great Floridan aquifer Subject to saltwater contamina-

espe-[Abbreviations: (1) Aquifers: P, principal aquifer in region; I, important aquifer in region; M, minor aquifer in region; U, unimportant as an aquifer in region.

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U

Many bedded basalt flows from Eo- cene to Plio- cene—P.

inter-U

Local flows—M.

Ft Union Gp—M.

Absent

Ft Union Gp—M.

Absent

Ft Union Gp—M.

Florida—

Avon Park Ls., South Carolina to Mexican border, Claibourne

Gp, Wilcox Gp—I.

Clayton Fm

in gia—I.

Geor-Absent

tion in coastal areas but source of largest groundwater supply in southeastern United States.

Source: Reprinted with permission from F Van der Leeden, F L Troise, and D K Todd The Water Encyclopedia.

Boca Raton, FL: Lewis Publishers, 1990 Copyright CRC Press, Boca Raton, Florida.

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Florida’s abundant aquifers without water quality degradation? Do our currentgroundwater “sustainable yield” concepts bear scrutiny (Sophocleous, 1997)?Groundwater management issues involve but extend beyond human water sup-ply and also intersect with surface water quality and quantity issues In the case ofboth the Edwards and the Ogallala aquifers, and the surficial aquifers of Florida,management has to consider the water needs of agricultural and human water sup-ply, but equally so, the maintenance of wildlife habitats The Edwards feeds promi-nent springs (supporting rare aquatic species), as well as culturally and ecologicallyimportant streams The Everglades in Florida represent a water system incorporat-ing both “surface” and “ground” water.The Ogallala involves formations too deep to

be directly involved in surface water maintenance; however in the same region ficial aquifers along the North and South Platte, the Missouri, and other rivers in thewestern Mississippi watershed are critical to maintaining wildlife habitat As withwetlands management strategies all over the United States, the Ogallala and HighPlains management equation involves finding the optimal distribution of water with-drawal among groundwater and surface water resources In all of these cases, qual-ity is a factor Where groundwater is overused, water quality and the quality ofaquatic ecosystems are also commonly degraded

sur-What are the consequences? The technology to drill and pump wells essentiallymade settled rural and town life possible in the Great Plains of the United States andsouth-central Canada, as well as in very similar locations in Australia, where no use-ful surface water was available nearby In many communities, stations, and farms inthese areas, wells can be drilled to groundwater, often hundreds of meters deep Ifgroundwater sources become depleted or contaminated, many farms or communities

FIGURE 4.1 (Continued ) (c) Groundwater potential in Canada (Source: Van der Leeden, Troise, and Todd, 1990 Adapted from P H Pearse et al., 1985 Currents of Change: Final Report—

Inquiry on Federal Water Policy Ottawa, Canada Reproduced with the permission of Environment

Canada, 1999.)

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in North Dakota or Queensland, for example, could not be maintained economically.With the years-long drought in Queensland, inhabitants recently were actually facingthe possibility of abandoning their towns due to dwindling groundwater reserves.Agriculture, especially in production of food for human consumption, has becomehighly dependent on irrigation The food economy of the United States is highlydependent on the production of fresh vegetables from California, Florida, and Mexico,mostly sustained by irrigation Israel, as a modern society established in a near-desert,

is totally dependent upon irrigated agriculture If large-scale, groundwater-dependentirrigation were to become impractical, major changes would be necessary in foodproduction and distribution worldwide In the case of the United States, water forirrigation reserved by prior appropriation can only be available for human watersupply if these rights are purchased or abandoned “Water farming” or purchasingprior agricultural water rights to groundwater reserves for urban water supply is anissue with many economic, cultural, and emotional aspects If water farming reservesgroundwater formerly allocated to agriculture for direct human use, how are freshproduce, cotton, or animal feed crops produced? Would all of this be shifted back tothe wetter (but colder) eastern United States, raising costs and requiring increasedexpenditures of hydrocarbons for greenhouse heating?

Even within a relatively small and water-rich part of North America, great variety

in water availability and quality can occur, illustrating the need for flexible and specific management The situation in western Ohio and eastern Indiana (e.g., Lloydand Lyke, 1995) is only one of many such examples The region is underlain by anextensive carbonate-rock aquifer that is largely underutilized due to low populationdensity, and relatively protected due to glacial clay till coverage However, local over-drafting and contamination of this aquifer can and does occur By contrast, carbonaterock in southern Ohio and Indiana (laid down under different depositional condi-tions) provides poor yields to wells Within this area of unproductive rock, Daytonand Columbus, Ohio, and many smaller communities are underlain by large and pro-ductive glacial-outwash aquifers These aquifers are at once both productive and vul-nerable (sometimes being the only flat places to build factories, drill oil wells, etc.)

site-As in southern Ohio, in much of New England, municipal groundwater suppliescan only be developed in relatively vulnerable (and highly developed) glacio-fluvialaquifers, although adequate household yields are possible from rock wells However,population densities and intensity of land use is high Overuse and vulnerability tocontamination make management of these aquifers a critical environmental imper-ative for the region that is only now being addressed seriously

PATTERNS OF PRIVATE AND PUBLIC

GROUNDWATER SOURCE USES:

QUALITY MANAGEMENT ISSUES

North America has a relatively high density of private groundwater supply use, ticularly in the eastern United States (see Figure 4.2) Private wells have long beenthe principal mode of water supply for widely spaced rural homesteads and manysmall villages This contrasts with France, for example, where public water service torural properties is the rule

par-Local variability in the quality and availability of groundwater influences sure to develop or extend public water supply distribution systems in rural settings.Constructing individual water supply wells is always more cost-effective wheregroundwater is abundant and of suitable quality Where natural groundwater quality

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pres-is exceptionally poor or where supplies are insufficient, the more costly option ofpiping treated water from a centralized source is a solution to provide suitablewater In the United States, the development of systems to provide public water torural residents has been promoted and funded by the federal government Manyareas have mixed individual private well and public piped water supply options.

Rural Groundwater Quality Management

Managing rural water quality is a significant challenge due to its site-specific natureand the typically inadequate financial and human resources available to addressproblems

Microbial Health Risks. The most commonly detected problem of rural privatewells is the occurrence of total-coliform (TC) bacteria positives Statistically mean-ingful studies over the years have shown that a significant number of wells sampledare positive for total coliform bacteria The most recent data available from large-scale studies (results from Midwest studies by the Centers for Disease Control andPrevention) show 41 percent TC positive and 11 percent fecal coliform positive(CDC, 1998) in the population of wells sampled Such contamination is mostly due

to well-construction deficiencies and deterioration (Exner et al., 1985; Smith, 1997;NGWA, 1998) It is rare that a large volume of an aquifer is contaminated by sewagewaste, although such incidents have occurred (Ground Water Geology Section,1961) A relatively new concern in the United States is the microbial impact of con-centrated animal farm operations (CAFO) through faults in animal waste manage-

FIGURE 4.2 Density of housing units using on-site domestic water supply systems in the United

States (by county) (Source: U.S Environmental Protection Agency, Office of Water Supply, Office

of Solid Waste Management Programs, 1977 The Report to Congress: Waste Disposal Practices and

Their Effects on Ground Water Reprinted in Van der Leeden, Troise, and Todd, 1990.)

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ment So far, this has been addressed as a surface water concern, but the potentialexists for new phenomena such as the spread to nearby wells of antibiotic-resistant

Salmonella sp from chicken manure deposited on shallow bedrock.

Correlations made in CDC (1998) suggest that positive TC results increase withincreasing well age, poor well condition and maintenance, shallow depth, and certainwell types (e.g., dug), supporting the value of well construction standards and wellmaintenance (Smith, 1997) However, recent research in relatively undisturbedaquifers (e.g., Jones et al., 1989) raises the question of whether bacteria that arecapable of positive growth in coliform media are native to aquifers, and not indica-tors of contamination from the outside

Pesticides and Nitrates. Another problem is pesticide and nitrate infiltration fromsurface contamination, discussed in greater detail later in this chapter This is a typi-cally rural to suburban groundwater quality concern, since these chemicals are used

in agricultural and horticultural activities Pesticides and nitrates represent the mainsources of chemical aquifer contamination in agricultural zones (Dupuy, 1997) Thematter of pesticide and nitrate contamination is also a good illustration of the inter-actions among (and need to understand) use and application methods, hydrogeol-ogy, climatic factors, and site-specific circumstances in prevention and prevention inmanagement In contrast to the limited understanding of the microbial impacts ofindustrial-scale agriculture, nitrate impact management for facilities such as CAFO

is relatively well understood However, experience in the Netherlands, where rises ingroundwater nitrate levels are attributed to manure spreading, provides a soberingexample of the possibilities

Public Water Supply Wells. Incidents of contamination are not unique to privatewells However, public wells are more likely to be isolated from contaminationsources and better constructed As is the case for coliform contamination, older,deteriorated, and poorly constructed wells (public or private) were more likely to becontaminated (EPA, 1990; USGS, 1997)

Nitrate and pesticide occurrence in wells is most likely where there is a high sity of wells and on-site waste disposal systems (which are themselves often forgot-ten or neglected by their users) Situations can be particularly acute when combinedwith a vulnerable aquifer setting such as a shallow limestone Numerous abandonedbut unsealed or poorly sealed wells (Gass et al., 1977; Banks, 1984; Smith, 1994) mayserve as conduits for contamination to move to the subsurface

den-Natural Environmental Impacts on Groundwater Quality

Groundwater quality reflects the physical, chemical, and biological actions ing with the water itself As part of the hydrologic cycle, the water falls as precipita-tion and is influenced by soil and organisms at or near the surface As groundwater

interact-in the saturated zone, it is affected by the nature of the formations (interact-includinteract-ing theirmicrobial ecologies) in which the water has been stored The influence of the aquiferformation depends on how long the water has been held in the aquifer, and howrapidly stored water is recharged by fresh water from the surface

Aquifer Formation Composition and Storage Effects

Groundwater movement is relatively slow, even in the most dynamic flow systems.Water moves in close contact with the minerals that make up the particles or frac-ture channels of the aquifer formation

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These minerals reflect the depositional environment of the formation For ple, limestone, laid down as carbonate-rich sediments, fossils, and fossil debris, con-sists of calcium carbonate with impurities Dolomite rock is chemically alteredlimestone containing a high fraction of magnesium Carbonate rock aquifers typicallyprovide an alkaline, high total dissolved solids (TDS) water that also has high calciumand/or magnesium hardness, but as illustrated in Figure 4.3, quality can vary greatlyamong carbonate aquifers with somewhat varying histories (e.g., Cummings, 1989).Sandstone (cemented quartz sands) and volcanic rock, by contrast, may be acidic(unless cemented by carbonates) The water may be relatively soft, especially withsodium minerals in the rock matrix, or low in TDS (but not always).

exam-The chemical influences of glacial and alluvial sands and gravels tend to reflectthe composition of the source rock of the formation material

All natural aquifer formations have impurities that provide additional ity to the water Most aquifers contain iron, and many contain manganese and otherminor metal constituents as well Certain igneous and metamorphic rocks, and theshales, sandstones, and unconsolidated deposits derived from them, may have highheavy metal or radionuclide contents

complex-A tragic example is that of the arsenic-rich alluvial and deltaic formations ofBangladesh and the West Bengal state of India which were tapped for tubewells toreplace poor-quality shallow groundwater and surface water sources (e.g., Bhat-tacharya et al., 1997; Mushtaq et al., 1997) These sediments were derived from As-rich continental source rocks Formations laid down near geo-historical continentalmargins (which may be different from continental margins now) may contain signif-icant amounts of evaporites, such as rock salt or gypsum, that contribute chlorides orsulfates

Elevated radon and other radionuclides (e.g., radium) levels in groundwaterclosely match the geographical distribution of rock types rich in radioactive miner-als (e.g., New England, the Canadian Shield region of the United States and Canada,shale areas of Ohio and the east, and sediments derived from them) See Figure 4.4.Sediments derived from metamorphic source rocks may contain elevated solid-phase radionuclides, for example the Kirkwood-Cohansey aquifer of New Jersey(USGS, 1998a) Phosphate deposits in Florida with high radioactive-isotope contentmay be added to this group

Deep formations well isolated from surface hydrologic recharge usually containbriny fluids (usually geochemically distinct from shallower groundwater), whichmay migrate to freshwater aquifers along density gradients if there are pathwayssuch as faults or boreholes open between the formations Table 4.1 is a generalizedsummary of water qualities that may be expected from wells developed in variousaquifers

Table 4.2 shows variation in mean analytical values for selected parametersamong aquifers in one area (Michigan), illustrating how difficult generalizationsabout water quality and source geochemistry can be

Aquifer Biogeochemistry

Lithology (rock type and composition) sets the broad tone for natural groundwaterquality, but the effects of microbial ecology in aquifers, typically driving redox reac-tions, provide additional complexity at the local scale Many oxidation-reduction(redox) transformations of common metals can occur without the mediation ofmicroorganisms, but are not likely to occur at ambient groundwater temperaturesand measured bulk redox potentials An example is the oxidation MnII to MnIV,

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brian, and Precambrian ages) (Source: Cummings, 1989.)

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which occurs at approximately Eh +600 to 700 at pH and temperature rangesencountered in potable groundwater (Hem 1985) Figure 4.5 illustrates the Eh-pHranges of stability for Mn species (gray areas are MnIV solids) Such a high redoxpotential is unlikely in groundwater, and in fact, MnIV is encountered in groundwa-ter with much lower measured bulk Eh Reductions of Fe, Mn, As, and a variety ofother metals have been demonstrated to be microbially controlled Both the oxida-tion and reduction of sulfur species largely involve bacteria except at extreme tem-peratures and pressures Research on these activities to-date was summarized inChapelle (1993) and Amy and Haldeman (1997) and continues actively.

The presence of organic carbon is an important factor influencing the activities ofmicroorganisms Both coal and hydrocarbons, which are extensively distributed informations throughout the United States and around the world, are ready sources oforganic carbon for bacteria Acidic coal mine waters provide the preferred environ-ment for iron-oxidizing bacteria, which, ironically, are chemolithotrophs and do notcommonly utilize organic C

Hydrocarbons, common in carbonate and other reduced sediments such asshales, provide the type of organic carbon compounds and the reductive conditionsthat promote sulfate reduction (and hydrogen sulfide formation) or methanogene-sis by microorganisms Jones et al (1989) summarizes the occurrence and ecology ofsulfate-reducing bacteria and methanogens in aquifers Where ready sources of sul-fate (e.g., gypsum) as well as short-chain hydrocarbons (e.g., acetate) are available,

H2S production can be intense This is well illustrated in carbonate aquifers acrossthe U.S Great Lakes region

Relatively high microbiological activity in aquifers can contribute significantamounts of carbon dioxide, producing gaseous waters and lower pH, thereby shiftingthe carbonate balance toward bicarbonate This condition can in turn contribute togreater dissolution of Ca and Mg from rock and very high hardness Figure 4.6 is a

FIGURE 4.4 Distribution of radon in groundwater mapped by county, based on available data

and aquifer type (Source: J Michel 1987 In Environmental Radon (pp 81–130) Ed by C R

Coth-ern and J E Smith New York: Plenum Press.)

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Basalt Very low Very low <120 mg/L Na, Cl, Si far from saturation May have high and exotic metal

Carbonate High >500 Very high >500 Ca, Mg carbonates (near saturation), High Fe, “dirtier” formations may

major sulfate admixture, may be have radionuclides at levels closely associated with evaporite greater than U.S MCLsdeposits

Igneous and Low <250 Low to moderate <120–500 Mixed, depending on rock mineral May have high and exotic metal

rocks

Surficial Very low to Moderate 120–240 Glacial-fluvial Mixed, depending on rock mineral Low Fe except where concentrated

sands/gravels moderate deposits may be have high origin Glacial-fluvial deposits by biological action (e.g.,

<250–500 carbonate hardness may be more carbonate Kirkwood-Cohansey aquifer,

dominated Pine Barrens, NJ), typically low

metal contents in pumpedgroundwater

Sandstone Low to moderate Moderate Mixed, depending on rock mineral Low to high depending on

origin Sandstones with carbon- cementation material and sandate cementation are closer to origin, and degree of water flush-carbonate saturation In the U.S ing over time May have east, often intermixed with coal radionuclides above U.S MCLsdeposits depending on sand origin (sands

are major sources of uraniumdeposits)

nuclides and metals (typicallypoorly flushed)

* These summaries are highly generalized and may likely be different regionally or locally Water quality should be

investigated at the wellfield or aquifer scale.

† Numbers from Lehr et al (1980) and considered general and representative.

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summary of the carbon system influencing aquifer conditions Table 4.3 is a summary

of physical-chemical activities often influenced by microorganisms in the subsurface.When wells are installed in formations, redox gradients form due to both abioticand biotic effects on metal species (Cullimore, 1993) These gradients can be verysharp Iron can oxidize readily at the appropriate redox potential along these gradi-ents, and microorganisms associated with iron precipitation are often found preferen-tially at Eh-pH environmental conditions as found in Figure 4.7 (Smith and Tuovinen,1985) Manganese, where present and in solution as Mn(II), also oxidizes catalytically

to Mn(IV) due to the activity of bacteria (Hatva et al., 1985; Vuorinen et al., 1988), amechanism also involved in at least some Fe(II)-Fe(III) oxidation (Hatva et al., 1985).Hydrogen sulfide is also oxidized by various S-oxidizers to Soand then to sulfate Theresulting oxidized products (solid S and sulfate salts) usually cause clogging in wellintake screens, pumps, and piping, and discoloration and odors in the water

Human Impacts

In addition to understanding and taking into consideration factors in naturalgroundwater quality, management of groundwater source quality is also concernedabout human impacts Within the overall scope of management, regulation is largelyfocused on human impacts Adverse human impacts include providing routes forpotential pathogens or chemicals to reach groundwater, and aquifer depletion.Other human activities can prevent or mitigate such adverse effects, and these arethe agents of appropriate stewardship of the groundwater resource

Health-Related Microbiological Occurrence in Groundwater

Groundwater is a preferred source of water supply due to natural removal of sirable microorganisms and viruses, especially where minimal treatment is the high-est priority (e.g., small systems and private wells)

unde-Although bacteria are not uncommon in groundwater, attenuation by variousmeans reduces total coliform and fecal indicator bacteria, commonly to unde-tectable levels A persistent coliform bacteria presence in groundwater samples usu-ally indicates short-circuited flow from a surface source [although some research(Jones et al., 1989) shows doubt about that assumption] Pathogenic bacteria or pro-tozoa are not known to be native to or commonly occur in groundwater exceptwhere direct and close sources of innoculant are present

TABLE 4.2 Selected Median Values of Physical-Chemical Parameters from Michigan Aquifers

Ca hardness Fe (dissolved) Boron (total) Chloride Source (total) in mg/L in µg/L in µg/L (dissolved) (mg/L)Glacial sand (Pleistocene) 8 50 <20 1.5Glacial gravel (Pleistocene) 27 270 40 1.8Engadine dolomite 515 1290 80 1.2Paleozoic dolomite 250 160 80 1.3Sylvania sandstone 600 1800 110 47Freda sandstone 101 16 640 11Portage Lake volcanics 29 47 700 5.3

Source: Cummings (1989), Appendix A.

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While viruses have been detected in groundwater, little has been known abouttheir occurrence in aquifers At the present time, intensive field research is limited,and conclusions that can be drawn from it are preliminary A study sampling from

460 wells across the United States managed by the American Water Works ServiceCompany (LeChevallier, 1997) showed that viral occurrence may be expected inmany groundwater sources Culturable viruses (cultured on tissue cells) weredetected in samples from 7 percent of the sites (LeChevallier, 1997), illustrating howdifferences in methods affect detection statistics Methods and their varying resultsare discussed in Abbaszadegan et al (1998)

FIGURE 4.5 Fields of stability of manganese solids and equilibrium

dissolved manganese activity as a function of Eh and pH at 25 ° C and 1

atmosphere pressure Activity of sulfur species 96 mg/L as SO 4 − , and

car-bon dioxide species 61 mg/L as HCO 3 (Source: Hem, 1985, p 87.)

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Conclusions about viral numbers and role in human disease have been difficult tomake, although viruses have been linked to enteric disease outbreaks from ground-water sources (e.g., Craun and Calderon, 1997) However, such outbreaks have to beobvious to be noticed Assessment of the occurrence of viruses at less-than-outbreaklevels has been hampered by limits in collection and analysis methods.

FIGURE 4.6 Carbon cycling in local flow systems (Source: F H Chapelle.

Wiley & Sons Reprinted by permission of John Wiley & Sons, Inc.)

TABLE 4.3 Representative Microbially Influenced Chemical and Redox Activities in Aquifers

Reaction activity* Microbiological influence†

Calcite dissolution CaCO3+H2CO3→Ca2++2 HCO3 Respiration: DOC removed and CO2added

Fe reduction Fe3++e =Fe2+ Dissimilatory use of ions such as Fe3+or

SO4 −reduction SO4 −+10H++e =H2S +4H2O SO4 −as final electron acceptors

Methanogenesis CO2+6H++e =CH4+H2O Dissimilatory reduction by archaebacteria

Sources: * Freeze and Cherry (1979).

† Chapelle (1993).

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Transport and fate of microflora and viruses depends on a complex interaction ofsoil characteristics, hydrology, climate, water quality, and features of the organisms orviruses themselves Gerba and Bitton (1984) provide a conceptual review of transportand attenuation of bacteria and viruses in soil and groundwater Tables 4.4 and 4.5summarize factors affecting enteric bacteria survival and viral movement in soils.Groundwater has characteristics that may tend to favor the transport of viableviruses: absence of strong oxidants, cool temperatures, and frequently alkaline pH.However, reported transport distances have been on the meter scale Yates (1997)reported viruses detected 402 m downgradient from a landfill on Long Island, NewYork, and three m below land-applied sludge (both potentially intense sources ofviral inoculum) Bales et al (1995) showed movement upwards of 14 m for bacterio-phage PDF-1 in 24 days in a glacial sand Attenuation factors clearly are at work atleast in granular aquifers (Bales et al., 1995) Schijven and Rietveld (1997) report

≥2.6 to 2.7 log removal of enteroviruses and ≥4.7 to 4.8 log removal of reovirusesover 30 m bank filtration distances in the Netherlands

While these studies provide evidence for mechanisms that provide impediment

to viral transport, the degree of removal inactivation have been difficult to model(Schijven and Rietveld, 1997; Yates, 1997) and can be reversible (Bales et al., 1995).All of these factors have relevance to water supply in determining what is neces-sary in risk assessment, and how to site and protect water supply wells The Ground-water (Disinfection) Rule (GWDR), currently under development by the U.S EPA

FIGURE 4.7 Eh-pH diagram for major iron species in

relation to the occurrence of iron bacteria in the

environ-ment (Source: S A Smith and O H Touvinen

“Environ-mental analysis of iron-precipitating bacteria in ground

water and wells.” Ground Water Monitoring Review, 5(4),

1985: 45–52.)

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(Macler, 1996; Macler and Pontius, 1997) and intended for promulgation early in thefirst decade of the twenty-first Century, will focus on minimizing risk of viral disease

in groundwater-source public water systems The mentioned research on viral rence, transport, and fate is intended to support the GWDR development effort,which is a regulatory process being developed on emerging and uncertain science

occur-TABLE 4.4 Factors Affecting Survival of Enteric Bacteria in Soil

Factor Comments

Moisture content Greater survival time in moist soils and during times of

high rainfallMoisture-holding capacity Survival time is less in sandy soils with lower water-

holding capacityTemperature Longer survival at low temperatures; longer survival in

winter than in summer

pH Shorter survival time in acid soils (pH 3–5) than in

alkaline soilsSunlight Shorter survival time at soil surface

Organic matter Increased survival and possible regrowth when sufficient

amounts of organic matter are presentAntagonism from soil microflora Increased survival time in sterile soil

Source: C P Gerba and G Bitton “Microbial pollutants: Their survival and transport pattern to

ground-water.” Pp 65–88 in Groundwater Pollution Microbiology C P Gerba and G Bitton, eds New York:

TABLE 4.5 Factors That May Influence Virus Movement to Groundwater

Factor Comments

Soil type Fine-textured soils retain viruses more effectively than light-textured

soils Iron oxides increase the adsorptive capacity of soils Muck soilsare generally poor adsorbents

pH Generally, adsorption increases when pH decreases However, the

reported trends are not clear-cut due to complicating factors.Cations Adsorption increases in the presence of cations (cations help reduce

repulsive forces on both virus and soil particles) Rainwater maydesorb viruses from soil to its low conductivity

Soluble organics Generally compete with viruses for adsorption sites No significant

competition at concentrations found wastewater effluents Humicand fulvic acid reduce virus adsorption to soils

Virus type Adsorption to soils varies with virus type and strain Viruses may have

different isoelectric points

Flow rate The higher the flow rate, the lower virus adsorption soils

Saturated versus Virus movement is less under unsaturated flow conditions

unsaturated flow

Source: C P Gerba and G Bitton “Microbial pollutants: Their survival and transport pattern to

ground-water.” Pp 65–88 in Groundwater Pollution Microbiology C P Gerba and G Bitton, eds New York:

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Point-Source Chemical Contamination

Point-source contamination of groundwater is that resulting from defined sources ofsmall areal extent such as single locations or properties Eliminating it has been amajor focus of public health regulation for many years in North America and else-where in the world Leaking septic tanks or privies are point sources identified aspublic health risks generations ago More recently, point sources of chemical con-taminants such as underground storage tanks or waste pits have been the focus ofenvironmental regulation

Point sources are frequently identifiable as sources of contamination by fieldchecking and testing They are typically closely regulated by government agencies.Examples include municipal or hazardous waste landfills, underground storage tanks,

or deep injection wells They are readily eliminated as groundwater risks by such igating actions as repair, replacement, or sealing Effectiveness of the “repair” canoften be judged quickly by the result of greatly reduced or eliminated contamination.However, reduction or elimination of contamination after a point source is removedmay also take many years Point sources can also be addressed in public health regu-lation because it is often possible to assign blame for allowing the problem to occur

mit-Nonpoint Chemical Contamination

Surface-water nonpoint contamination is a well-known problem that is extensivelydiscussed in the literature and elsewhere in this text Nonpoint-source contaminantssuch as nitrate or pesticides also reach groundwater from regional use at the surface

An example might be elevated nitrate levels in shallow wells in an area of sandy soilswhere there is extensive use of fertilizers and septic tanks This is a worldwide prob-lem in areas of vulnerable soil situations

In many regions, nitrate concentration levels in groundwater can reach andexceed water quality criteria (e.g., U.S drinking water, 10 mg NO3/L, E.U ambient,

50 mg NO3/L) The increasing use of mineral fertilizers in some regions and theintensive exploitation of the aquifers for crop irrigation have led to groundwatercontamination by nitrates (e.g., Dupuy et al., 1997; USGS, 1997) The dynamics(long-term persistence) and extensiveness (regional contamination) of this contam-ination, as well as uncertainty about behavior in aquifers, make it a sensitive envi-ronmental issue

The USGS (1997), summarizing current USGS study results, reports that over

300 studies of pesticide occurrences in groundwater and soils have been carried outduring the past 30 years Further data are being compiled in the National WaterQuality Assessment Program (NAWQA) Provisional summary data and interpreta-tion (subject to revision) are available from the USGS on the World Wide Web (e.g.,USGS, 1998b), a mechanism that permits rapid, but fluid publication of such infor-mation USGS studies have shown that:

1 Pesticides from every major chemical class have been detected in groundwater.

2 Pesticides are commonly present in low concentrations in groundwater beneath

agricultural areas, but seldom exceed water quality standards

Occurrence of pesticides in groundwater follows a pattern resembling that of form bacteria occurrence (Figure 4.8)

coli-The USGS currently has come to a several conclusions on pesticide and nitratecontamination occurrences associated with cropland (USGS, 1997):

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1 Factors most strongly associated with increased likelihood of pesticide

occur-rence in wells are high pesticide use, high recharge by either precipitation or gation, and shallow, inadequately sealed, or older wells (consistent with resultsreported by EPA 1990) (Figures 4.9 and 4.10)

irri-2 They are more likely to occur where groundwater is particularly vulnerable, such

as shallow, unprotected sands, or highly solutioned (karstic) or fractured rock

3 Pesticide contamination is generally more likely in shallow groundwater than in

deep groundwater, and where well screens are located close to the water table,but such relations are not always clear-cut

4 Frequencies of pesticide detection are almost always low in low-use areas, but

vary widely in areas of high use

5 Pesticide levels in groundwater show pronounced seasonal variability in

agricul-tural areas [consistent with Dupuy (1997)], with maximum values often followingspring applications Temporal variations in pesticide concentrations decreasewith increasing depth and are generally larger in unconsolidated deposits than inbedrock

As with pesticides, the risk of groundwater contamination by nitrate is not the sameeverywhere (Nolan and Ruddy, 1996) Figure 4.11 shows four groups in order ofincreasing risk related to soil characteristics:

1 Poorly drained soils with low nitrogen input (white area on the map)

2 Well-drained soils with low nitrogen input (light gray area)

3 Poorly drained soils with high nitrogen input (medium gray area)

4 Well-drained soils with high nitrogen input (dark grayish area)

Well-drained soils can easily transmit water and nitrate to groundwater In contrast,the other three groups have a lower risk of nitrate contamination because of poorlydrained soils and/or low nitrogen input Poorly drained soils transmit water andchemicals at a slower rate than well-drained soils (Nolan and Ruddy, 1996) Drainsand ditches commonly are used to remove excess water from poorly drained agricul-

Detection more likely

Detection less likely

High pesticide use High recharge High soil permeability Unconsolidated or karst

No confirming layer(s) Dug or driven wells Shallow wells Wells with leaky seals

Thick confirming layer(s) Drilled wells Deep wells Wells with proper seals

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1,000 10,000 100,000 1,000,000

COUNTYWIDE ATRAZINE USE,

IN POUNDS OF ACTIVE INGREDIENT PER YEAR

FIGURE 4.9 Proportion of sampled wells with atrazine detections in

relation to countywide use Wells were sampled as part of the National

Alachlor Well-Water Survey (Source: U.S Geological Survey, Pesticides

in Ground Water, USGS Fact Sheet FS-244-95, http://water.wr.usgs.gov/

> 10% of sampled wells

FIGURE 4.10 Frequency of triazine herbicide detection in counties with ten

or more wells sampled during the Cooperative Private Well Testing Program.

(Source: U.S Geological Survey, Pesticides in Ground Water, USGS Fact Sheet

FS-244-95, http://water.wr.usgs.gov/pnsp/gw/gw5.html.)

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tural fields, diverting nitrate to nearby streams (and thus making it a surface waterproblem).

The effects of application of fertilizers is illustrated by studies from the UnitedKingdom The British Geological Survey (BGS) has been studying the problem ofnitrates in groundwater for over 15 years.As is the case elsewhere in Europe, the con-centrations of nitrate in groundwater in the principal British aquifers are generallyrising, and some groundwater sources already exceed the EC Drinking Water Direc-tive limit of 50 mg/L NO3(11.3 mg/L NO3-N).The BGS suggests that many others arelikely to exceed this limit if current agricultural practices continue unchanged.Investigations at four grassland sites on the chalk of southern England between

1987 and 1989 (Figure 4.12) demonstrated that the majority of pore water nitrateconcentrations under most of the grazed grassland sites investigated exceed the EClimit and that leaching from grazed grassland receiving more than about 100 kgN/ha/yr is likely to give rise to nitrate concentrations above the EC limit in ground-water recharge Typical nitrate concentrations in the unsaturated zone beneathgrazed grassland sites (Figure 4.13) are in the range of 10 to 100 mg/L NO3-N, withmarked peaks as high as 250 mg/L NO3-N This compares with values of less than

5 mg/L NO3-N measured under lower-productivity grassland, and is also higher thanlevels observed under intensively cultivated land Nitrate losses expressed as a per-centage equivalent of the nitrogen input to the land range from 15 up to 45 percent,showing a broad correlation between the implied leaching loss and the quantity ofnitrogen applied (BGS, 1997)

There is historically less information available on pesticide occurrence beneathnonagricultural land, such as residential areas and golf courses, despite chemical appli-cation rates that often exceed those for most crops However, studies of golf courses on

FIGURE 4.11 Areas in the United States most vulnerable to nitrate contamination of ter (shown in grayish blue on the map) generally have well-drained soils and high-nitrogen input from fertilizer, manure, and atmospheric deposition High-risk areas occur primarily in the western,

groundwa-midwestern, and southeastern portions of the nation (Source: U.S Geological Survey Fact Sheet

FS-092-96, http://wwwrvares.er.usgs.gov/nawqa/fs-092-96/fig1.html.)

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Cape Cod, Massachusetts, and in Florida (Cohen, 1996; Cohen et al., 1990; Swancar,1996) shed some illumination Swancar (1996) found pesticides in groundwater atseven of nine golf courses, with 45 percent at trace concentrations and 92 percentbelow MCLs or health advisory levels (HALs) In the Florida study, there was onetrace diazinon detection, although this insecticide was banned for golf courses in the1980s This raises the question of the poorly known contribution of lawn application, apossible source of the diazinon occurrence in the Florida study (Cohen, 1996).The nature of land use controls also has to be considered carefully For example,protection zones around public supply wells are often used as a setback to reduce orprevent contamination of groundwater Nitrate concentrations can be reduced byestablishing zones in which agriculture would be restricted, perhaps by replacement

of arable farming with grassland or woodland, with appropriate compensation tofarmers The BGS studies indicate that, where grassland is to be a land use option inplans to reduce nitrate concentrations in groundwater supply sources, restrictions onfertilizer applications to the grassland may be required

The discharge of groundwater contaminants to surface water is another aspect ofthe relationship between groundwater and surface water For example, sources of ele-vated TDS, salt, metals, or industrial chemicals may have their source in groundwaterthat contains or is contaminated with these constituents The potential for close inter-action of ground and surface waters is illustrated by detections of pesticides in sam-

FIGURE 4.12 Outcrop of chalk aquifer in SE England and location of grassland

http://www.akw.ac.uk/bgs/w3/hydro/Nitrate.html.)

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ples (USGS, 1998b) On the one hand, high concentrations of pesticide contaminants

in rivers may lead to contamination of shallow groundwaters in agricultural areasduring periods of extensive seepage of river water into underlying alluvial aquifers.This is particularly the case following spring applications, when pesticide loads andriver flows reach maximum levels Conversely, pesticides in alluvial aquifers may flowinto adjoining rivers during periods of low runoff In many areas, “bank filtration” byalluvial aquifers has been found to be ineffective in removing pesticides from waterdrawn from pesticide-contaminated rivers into adjacent supply wells

Industrial Agriculture: A Mixture of Point

and Nonpoint Source Contamination

Agriculture has traditionally been a low-density activity on the land Until recently,animal fecal wastes were thinly distributed over rangeland by grazing animals orspread mechanically Problems, if they occurred, tended to be nonpoint types, such asrunoff from inadequately protected fields flowing into surface waters

In more recent times, hog, cattle, and poultry operations have become more centrated In large-animal (cattle and hog) CAFO operations, wastes are concen-trated in lagoons in liquid form and then periodically pumped and spread or sprayed.This management method has the effect of creating a concentrated point source (thelagoon) in addition to nonpoint nitrate and bacteria land application Effectivegroundwater protection against the risk posed by such a facility thus depends onassuring that the lagoon does not leak as well as on nonpoint runoff prevention

con-FIGURE 4.13 Unsaturated zone pore water nitrate profiles for

se-lected grazed grassland sites (Source: BD/IPR/20-7, British Geological

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Large-scale industrial chicken and turkey CAFO operations have a similareffect Animal wastes must be dispersed in a manner that prevents surface andgroundwater contamination One strategy is to make the wastes available to areafarmers for spreading However, if nonpoint problems occur, the spreading farmerand not the generator may be at legal risk.

Egg and pullet operations may constitute a point source in addition to nonpointbird waste problems For example, egg washing for a 1-million-hen operation gener-ates thousands of cubic meters of wastewater per day that must be properly treated

or dispersed In addition, large-scale bird and farrowing operations generate a tain percentage loss in dead animals, which must be properly composted on-site ifthey are not removed off-site Animal disposal represents a serious risk of microbialcontamination if performed improperly

cer-Effects of Excessive Withdrawal on Water Quality

In addition to water quality degradation by the introduction of wastes or chemicals

to aquifers, excessive withdrawal may have localized or area-wide impacts on thequality of pumped groundwater Examples include chronic seawater infiltrationproblems on Long Island and in New York, New Jersey, coastal Florida, and Califor-nia Another well-studied situation is that of pulling seawater into freshwater lenses

on ocean islands, as in Hawaii and the Bahamas Excessive pumping may also pull inundesirable water from other formations, such as upconing from brine-containingaquifers deeper in a sedimentary series

This latter point introduces the topic of well or wellfield use in managing waterquality A particular aquifer may not be generally overtaxed or exhibit overuse-related water quality However, individual wells or wellfields may cause water qual-ity degradation locally if operated at unsustainable rates (which must be determinedindividually) The most common effect is excessive oxidation of Fe and Mn in a well-field’s area of influence

Interrelationships Between Performance and Quality Decline

The primary negative effect of area-wide Fe and Mn oxidation is that Fe and Mnoxides can build up and reduce the hydraulic conductivity in the oxidized drawdownzone, causing further increases in drawdown This process continues in a cause-effectcycle, and is part of the long-term aging process of some wellfields Overall calcu-lated aquifer transmissivity (flow capacity times aquifer thickness) may be notice-ably reduced as drawdown increases.This results in increased well areas of influence,and increases the possibility of inducing poor-quality water or contaminants to flowtoward affected wells Migrating organic pollutants (e.g., petroleum products) canseverely increase Fe and Mn available, as was discussed earlier

The phenomenon of lifetime aquifer or wellfield aging is poorly understood.There does seem to be a pattern of increasing frequency and severity of well reha-bilitation in wellfields observed over some decades For example, in the Ohio RiverValley, alluvial wellfields exhibit accelerated maintenance problems after about 20years This may be a near-well phenomenon, but it also occurs on the wellfield scale

Groundwater Quality Management Options

Once the many factors that affect groundwater quality are understood, methods ofmanagement can be implemented or evaluated Groundwater management is by

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nature localized However, it can be planned simultaneously (1) in a general way atthe regional or aquifer scale and then (2) more specifically at the wellfield scale.

The Big Picture: Regional and Aquifer Scale Management

Groundwater management may be considered on regional basin or aquifer scales

As is the case for large bodies of surface water such as lakes or rivers, aquifers andbasins do not respect surface political jurisdictions (Figure 4.14), so “regional” maypreferably have something other than artificial (such as state) boundaries For exam-ple, on a system scale, the Atlantic and Gulf coastal plain aquifer systems each spanseveral U.S states The Ogallala aquifer alone extends across several states Manag-ing such systems properly involves cooperation across major political jurisdictions(even international ones, e.g., at the U.S.-México and Washington–British Columbiafrontiers, or more dramatically, in the Middle East, where nations in political conflictshare aquifers)

On the other hand, specific aquifer units may be very localized, especially smallglacial valley fill or alluvial fan aquifers These also will not respect surface politicalboundaries Entities such as towns or individual properties dependent upon an

FIGURE 4.14 Regional aquifer studies in the United States (Source: Van der Leeden, Troise, and

Todd, 1990 Originally from Cardin, C W., and others 1986 Water Resources Division in the 1980s U.S Geological Survey Circular 1005.)

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aquifer source may need to arrange with adjacent jurisdictions to protect areas side their legal boundaries Such cooperation at both the regional and local scalerequires perhaps the greatest challenge in groundwater management: coordination ofpolitical and private entities for an intangible goal such as groundwater protection.

out-At both scales, the ideal situation is to have accurate and complete hydrogeologicinformation and mapping for planning for aquifer protection and management.Lithologic, depositional, depth, flow, and quality information should be available ingroundwater resources maps Where published by jurisdictions such as counties, spe-cific hydrogeologic information should be included, as well as keys for linkage toadjacent maps, and references to sources The advent of widespread availability ofdigital mapping information has made this somewhat easier

However, in practice, one common problem with groundwater resources or tamination vulnerability mapping is the limited information available With limitedbudgets, state or similar water resources agencies may not have the resources forhighly detailed mapping, or may not verify file or regional information used Localgroundwater users should plan to conduct investigations to adapt general maps orassessments for the level of detail they need for local planning

con-State/Provincial/Tribal and Federal Groundwater Management Strategies

Groundwater may be managed in a variety of ways, depending on political structureand tradition In the Canadian, U.S., and Australian federal systems, for example,groundwater management and protection are accomplished at the subfederal (state,province, or tribal) level Other nations make this a national government function orstrictly a local matter

In the case of the United States, federal legislation serves to protect groundwaterand groundwater public water supply sources to some degree, but there is no singlegroundwater protection law Both the Resource Conservation and Recovery Act(RCRA) and the Comprehensive Environmental Response, Compensation andLiability Act (CERCLA or “Superfund”), as well as other legislation, have ground-water protection as one goal The Safe Drinking Water Act (SDWA) mandatessource water (including wellhead) protection planning for public water supplies(and thus groundwater protection for systems using groundwater)

Water use is prioritized and allocated at the state and tribal level in the UnitedStates and Canada (Fetter, 1980) In the 17 U.S western states, the doctrine of priorappropriation is used in surface water management Under prior appropriation, use

is “first-come, first served” with the junior rights holder holding lesser priority Somestates (e.g., New Mexico) also apply this doctrine to groundwater Others, such asCalifornia, apply “correlative rights”: the right to use groundwater underlying aproperty belongs to the landowner, who may use it as long as the use is “reasonable.”

In other states (Colorado for example) groundwater and surface water resources areintegrated into basins, and are not treated separately

Whatever the foundation of the water rights system, groundwater resources may

be allocated based on criteria such as priority of need and water availability In statessuch as North Dakota (and the Australian state of Queensland, for comparison),where water belongs to the state (or the Crown in the case of Australian states),water may be allocated on a volume basis Landowners or public water purveyors orwater districts have the right to use a certain volume per year The allocation mayapply to all water users, or some (such as private well owners) may be exempted Theallocation is usually based on available stored resources and available rechargeexpected In times of drought, allocations may be more restricted

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In the more humid U.S East, where rainfall exceeds evapotranspiration, twogroundwater use doctrines prevail: English Rule, where a landowner has absoluteright to groundwater under the property regardless of the value of the use, andAmerican Rule, where neighbors have rights, too, and landowners may only use

“reasonable” amounts of water so as not to harm a neighbor American doctrine isincreasingly applied throughout the eastern United States, mostly through individ-ual legal decisions However, like their western-state counterparts, some easternand Midwestern states (Wisconsin for example) have adopted comprehensive,regional groundwater management plans rather than relying on case-by-case man-agement

The effectiveness of such plans is yet to be conclusively determined, since fewhave been in place for sufficient time to be evaluated properly Most are still in thestudy stage [e.g., the Willamette River Basin in Oregon, (USGS, 1996)] However,some are quite mature Examples include the Edwards Aquifer Authority, the WaterResources Board system in North Dakota (North Dakota State Water Commis-sion), and the Delaware River Basin Commission (Pennsylvania, New York, NewJersey, and Delaware) Management of artesian aquifer basins includes somenotable successes One of these is the Australian interstate project to limit hydro-static head loss in the Great Artesian Basin in western Queensland, New SouthWales, and the Northern Territories (Harth, 1993; Free et al., 1995), which has hadgreat success in plugging uncontrolled artesian well flows, although desert springsand aquifer hydrostatic levels in general remain at risk

Water rights for tribal reservations represents an interesting challenge for thewater-short U.S West Native nations were forced out of the more water-rich areas

of the United States settled by people of the Euro-American culture by the late1830s, and settled on more arid land in the West However, in a historic 1908 U.S.Supreme Court decision, it was ruled that the federal government must reservewater rights sufficient to make the tribal land productive This amount was ruled to

be that necessary to irrigate arable land States could not reserve or allocate thiswater for other uses While the 1908 case applied to surface water, in 1976 theSupreme Court extended the ruling to include groundwater

One important issue in water rights adjudication is determining who has therights to recharged or stored water The priority of groundwater recharge (overother land uses) to replenish water supplies to historical levels was established by aCalifornia state ruling in 1969 Rights to use water equivalent to that injected toaquifer storage were also upheld in California It is generally recognized in theUnited States that water committed to aquifer storage and recovery systems may bereclaimed by the entity pumping water into storage

In terms of quality, states may apply specific environmental laws to protectgroundwater, or extend nuisance laws or “reasonable use” doctrine for this purpose

In general, if a party causes harm to groundwater quality, or if it is determined thatthey may cause potential harm, the state may act Federal laws are frequentlyapplied by states with primacy in environmental enforcement In nonprimacy states,

or on tribal or territorial land, U.S federal agencies may act directly In Canada,either provincial or federal authorities may act in such circumstances

States have the authority to enact legislation to protect groundwater fromdegradation due to overuse Difficulties arise when states try to establish responsi-bility for changes in groundwater quality that develop due to problems other thandirect contamination In such cases, it may be more effective to take a regionalapproach to mitigating withdrawal-related quality problems Examples includecoastal states that establish recharge projects to protect large areas from seawaterintrusion

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The Local Scale: Source Water (Including Wellhead and Aquifer) Protection

While state or regional activities may have defined regulatory authority and times are effective in managing water use, local activities are more important in thepractical management of groundwater quality problems Sources of contaminationare most typically located within meters to at most a few kilometers from theaffected wells

some-Recognizing this, the wellhead protection planning (WHPP) process establishedunder the U.S federal SDWA amendments of 1987 for public groundwater-usingsystems (and now part of the Source Water Protection Program under the 1996amendments) is remarkably “federalist” in the original sense of the word, implying

a high degree of local decision-making authority A similar process is being mented in Canada In the United States, the existing WHPP and evolving SWAPprocesses permit broad state latitude in overall management In Canada, provincialauthority is presumed as in all resource management issues

imple-As a process, WHPP/SWAP depends on gathering local hydrogeological andpotential pollution source risk information, and encourages local management andeducation initiatives.The entities involved in developing WHPP may range from stateagencies to water conservancy districts to local water suppliers The information necessary for the process is highly specific to the public water supply wellfields inquestion

WHPP (as a subdivision of SWAP) applies to designated wellhead protection areas(WHPA).These are intended to be scientifically defined using hydrologic and geologicdata gathering and analysis to establish valid groundwater time-of-travel zones orcatchment areas around pumping wells For many public water supply wellfields, theWHPA delineation process provides the most complete and accurate (and sometimesthe only such) hydrogeologic information ever gathered for their management.Both the WHPA delineation and the management planning processes of WHPPhave the potential to go fundamentally wrong Most WHPA delineation depends onhydrologic modeling of groundwater flow Valid modeling depends on gathering datathat represent the situation in the ground Different groundwater models emphasizedifferent parameters in their calculations If data and calculations are incomplete orinaccurate, or the model invalid for the application, the shape of the WHPA may bewrong for management purposes Both data and model validity have to be checkedagainst the in-ground conditions by appropriate hydrogeologic analysis

After the WHPA is delineated, risks to the wellfield within the zone must beassessed Questions to be asked in the risk assessment process include: What consti-tutes risk? How are potential risks ranked? Are all significant real risks identified?What about historical impacts? Just what has transpired on that flat patch of grassyland near the river? What ever became of those oil wells or oil tanks? These kinds ofquestions add “industrial archaeologist” to the list of skills (including “engineer,”

“manager,” and “hydrogeologist”) that a water system may need for source protection Modern and active industrial activities are much less likely tohave groundwater impacts than past activities because they work under current reg-ulations It becomes important to identify and assess whether further testing might

groundwater-be necessary at locations in question

In the protection task, the water supplier actually takes action to protect theWHPA It is easy to write and file a plan, but it is another matter to enact the plan.The WHPA often crosses jurisdictional boundaries If a city files a WHPP for aWHPA that includes neighboring rural land, how does it induce the neighbors totake enforcement action to protect their wellfield? What authority is to be used inprotecting this WHPA? Will enforcement or education be used?

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Witten et al (1995) identifies numerous options available Among the most ful tools available for local governments are land-use regulations (depending onlocal-rule authority in individual states) Local entities may restrict land uses thatcould adversely affect groundwater quality Industrial activities may be encouraged

use-to relocate out of the WHPA, or permits required for certain activities such as dling hazardous materials In practical terms, zoning restrictions must be balancedagainst excessive “takings” that may require compensation to the landowner How-ever, in some cases, paying compensation to remove risky operations may be a goodinvestment

han-An unfortunate unintended consequence of WHP programs in some tions has been the preclusion of groundwater use through denial of, or unreason-able restrictions on, permits for wells proximate to hypothetical, potential sources

jurisdic-of contamination Program administrators unable to control potential threatsinstead control groundwater use through existing permitting authority The result isthe “writing off” of certain groundwater resources that are not (and may never be)contaminated

The Local Scale Beyond Wellhead Protection: Aquifer Protection

The WHPP process is specific to public water supplies The U.S SDWA gives the U.S.EPA no jurisdiction over private water supplies Instead, private water supply pro-tection is managed by state and local environmental health or water resourcesauthorities State and local jurisdictions typically regulate waste disposal and wellplacement and construction

The evolving SWAP process is a broader approach than WHPP, and envisions agreater degree of state official participation in source water delineation, instead ofthe local lead in delineation under WHPP In Ohio, for example, the state EPA willdelineate source water zones, relieving the responsibilities of local officials, but cer-tainly resulting in less detailed and less locally focused zones

Beyond SWAP, federal point-source groundwater control legislation may play arole Enforcement of landfill, injection well, or radioactive waste repository regula-tions may serve to protect the groundwater that supplies private wells

U.S federal law, for example, restricts certain chemicals, uses, storage, and posal However, there is little regulatory protection that is actually effective locallyagainst nonpoint-source contamination While specific regulatory authority mayexist, identifying sources of hydrocarbons, nitrate, or ammonia in a well may be dif-ficult, time-consuming, and expensive Responding to something like an industrialagricultural operation risk to groundwater may be overwhelming to small popula-tions of affected people

dis-To prevent pesticides and nitrates from reaching water supply wells vulnerable tononpoint-source contamination, some process is necessary to identify and remove(1) sources of contamination and (2) preferential pathways for contamination toreach aquifers (such as abandoned wells) Examples of source-control strategiesinclude switching from septic tank leachfield systems to more advanced systems orsewers in sensitive locations, or encouragement of on-site system maintenance, andbest agricultural management practices to keep pesticides and fertilizer in the soilroot zone, the intended point of application Such an effort may require the forma-tion of a county sewer district or active involvement of a county soil and water con-servation district in regional groundwater planning

Also on the list of “unenforced mandates” are abandoned wells Almost all stateshave legislation that requires the proper sealing of abandoned wells, boreholes, and

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