1 INTRODUCTION

This book has been written to help ground water. The better we 's citizens learn about one understand this valuable resource, of our most important natural the better we will be able to protect resources – ground water. Water and manage it for our benefit and the beneath the earth’s surface, or benefit of future generations. ground water, quenches our thirst, supports our crops and livestock, Words printed in bold type in the waters our lawns, and supplies text are defined in the glossary. industry throughout Alabama. If used wisely, ground water resources will Ground water facts, indicated by never run out. However, lack of the water drop symbol, appear planning and careless actions can at various points in the text. cause shortages or contamination of

Alabama has enough ground water to cover the entire state to a depth of about 50 feet. 2 WHAT IS GROUND WATER? When rain falls on the ground, saturated zone is called the water some runs off into rivers or streams table and water in the saturated zone and some soaks into the ground and is ground water. partially or fully fills the open spaces between soil particles. These open Ground water forms a fairly spaces are called pores. Some of the continuous mass of primarily fresh water that enters the shallower soil water that underlies the land surface. will partially fill the pores spaces. It is It may be only a few inches beneath held by capillary forces in the the surface or hundreds of feet deep. unsaturated zone. Capillary forces Where the water table meets the land are caused by surface tension. These surface, ground water discharges forces hold very small amounts of such as springs may occur. Water fluids in the pore spaces. If more may also seep out slowly to form water enters the soil than can be held wetlands, swamps or marshes, by capillary forces, it will continue to which are important ecologically. It flow downward until it reaches a depth also contributes to the flow of many where all of the pore spaces are filled streams. Nationally, 40% of the base with water. The soil in this zone is said flow of streams comes from ground to be saturated. The top of this water.

A film of water clings to each particle in the unsaturated zone even when it may seem dry. However, this residual water cannot be obtained through pumping of a well as in the saturated zone. 3 Many of us drink ground water Wells are not just holes in the every day. Turn on the faucet in ground. Proper well construction Dothan, Greenville, Ozark, Selma, or keeps soil and sediment out of water Montgomery, to name a few cities, that is pumped from the well. It also and you are probably drinking ground keeps contaminants from the surface water. Eighty percent of the public from entering the well. The well bore water systems in this state depend in a properly constructed well may be on ground water for at least part of lined with casing made of metal or their water supply. Public water plastic. Where water enters the well systems in Alabama withdraw more a special casing called a screen is ground water than any other category used. The screen is slotted to admit of use, about 220 million gallons per water inside the casing, and it is day (gpd). Many rural Alabamians surrounded by gravel. The gravel lets obtain water from private wells. In in water but keeps sediment out. The fact, nearly one in ten Alabamians get cement in the upper part of the their drinking water from more than annulus, the part of the bore hole 100,000 private wells. outside the casing, protects the 4

Cross section of a properly constructed well subsurface from contamination that What does all this water cost? A could enter the well bore. The rest of gallon of water, delivered to your the annulus is filled with clean sand. house by a public water system, costs less than half a cent in most places Why do so many of us depend in Alabama. You can buy water for as upon ground water for our drinking little as 0.08 cents per gallon (about water? Many times ground water may 12 gallons per penny) from some be the most economical source Alabama public water systems, which because it is so readily available in makes it one of the world’s best many areas of our state. Also, ground bargains. Nationally, tap water costs water usually requires less treatment about 0.2 cents per gallon. A gallon than surface water. Although both of water in the grocery store costs at surface water and ground water have least 50 cents, more than 100 times to be chlorinated for public water as much as tap water in most parts supplies, surface water must also be of our state. treated to settle out soil particles which are carried along in streams Drinking water is not the only and rivers. important use of ground water. 5

How does Alabama use ground water?

Ground water is also used in living in our state. This accounts for agriculture, one of Alabama’s most about one fourth of the total important industries. Agriculture uses statewide ground water use. about 100 million gallons of ground Alabamians use a total of about 400 water every day, or more than 9,000 million gallons of ground water per gallons per year for each person day, or about 146 billion gallons annually. 6

Brahan Spring, Huntsville's Big Spring, discharges from the base of a limestone bluff.

Center pivot irrigation system 7

Alabama’s ground water reserves rivers or reservoirs, and other are estimated at about 533 trillion hydrographs record water levels in gallons, or enough to last 3,300 years wells. In a stable situation, that is, one at the present rate of consumption. with no long term trends, water levels Ground water is a renewable do not change. An example of a stable resource that is constantly situation is shown in the hydrograph replenished by rainfall. Alabama is a of the Dale County well shown on the relatively wet states. More than 55 next page. If more water is pumped inches of rain fall each year. than can be naturally replenished, Considering these facts, it seems that then water levels decline over time, conserving our ground water supply as shown in the Barbour County would not be a concern, but the hydrograph. The hydrograph from a numbers do not tell the whole story. Houston County well shows that water levels in wells may change with the Ground water, while plentiful, is not seasons. All of these are real evenly distributed throughout the examples. There are even some state. In some places the water is wells in which water levels are rising! shallow and abundant; in other places it is deeper and harder to find. When Ground water availability varies found, ground water can be difficult from region to region and is controlled to extract in the quantities needed and primarily by the kinds of rocks, may differ in quality from place to sediments, and soils that contain the place. So even though a statewide water. To understand the differences shortage is unlikely, local shortages in water availability between different may occur in some areas where the areas, we must first understand how demand is great, causing serious ground water moves from one area problems. to another, as well as the rock, sediment, and soil properties that Hydrographs are graphs that show control water movement, storage, water levels over time. Some and availability. hydrographs record water levels in 8

Water levels in this Dale County well have been stable since the well was drilled in 1964.

Water levels in this Barbour County well have been declining steadily since 1968 and continued decline is likely.

Water levels in this Houston County well have varied widely while declining overall. However, during a 5-year period (inside box) wide swings in water levels did not occur, permitting the regular seasonal cycle to be seen. Water levels are high in the spring (S) and low in the fall (F), reflecting the influence of spring rains and summer droughts.

Hydrographs show changes in water levels over time. These three hydrographs illustrate some of the water level changes that have been observed in wells in Alabama. 9 WHAT IS GROUND WATER MADE OF?

Water is composed of hydrogen reason bottled spring water is so and oxygen – two atoms of hydrogen popular. for every atom of oxygen. But naturally occurring water is never Ground water is also likely to vary pure H2O. Water contains dissolved less in quality over time than surface or suspended materials, both natural water. Ground water moves slowly and anthropogenic (caused by and it changes slowly. Natural factors human activity), that may be harmful, affecting ground water quality include helpful, or not have any effect. Some the amount of time the water has natural water constituents, like been underground, the composition fluoride, are helpful in small amounts of the rocks through which the water but harmful where they are too has moved, and local conditions concentrated. Iron causes no underground. problems at low concentrations but at high concentrations may result in Few natural water quality an unpleasant taste and staining of problems affect ground water in clothes and household fixtures. Alabama. Problems of local significance in some areas include Ground water commonly contains excessive hardness, high more mineral matter than surface concentrations of iron, chlorides and water. This is because ground water dissolved solids, and low pH (high moves slowly through the subsurface acidity). All of these factors can make and has more time to react with water unsuitable for some uses. As minerals with which it comes in mentioned, too much iron in water contact. The natural minerals in some stains fabric and fixtures, whereas ground water taste good, which is one high chloride concentrations and low pH can corrode fixtures. 10

Wetlands, such as this gum swamp in Greene County, occur when the water table meets the land surface. They provide natural filters and serve to protect the water quality of streams.

The effects of human activity on passing cleaner water on to other ground water quality are commonly sediment or rock units. less severe than on surface water. This is because most sources of Although there are many instances anthropogenic contamination are in which ground water has been located at the Earth’s surface. Also, contaminated through surface underground layers of clay and other activities, these effects are generally natural materials help keep localized. Most ground water in contaminants out of ground water. Alabama is free of significant These earth materials act as natural anthropogenic contaminants. filters, retaining contaminants and 11 THE HYDROLOGIC CYCLE

The waters on the surface of the drains directly into streams and lakes earth and beneath the earth are not as runoff, and eventually flows back separate. They are connected by soil to the ocean. The rest enters the soil. and rock pore spaces and fractures. If the sun is hot enough and the air Water constantly moves from one dry enough, much of the moisture in zone to the other. This movement is soil evaporates and returns to the part of a global pathway called the atmosphere. If plants are growing in hydrologic cycle, which can be the soil, their roots will capture some or most of the The hydrologic cycle goes on forever, water in that and involves all water on and in the zone. Ultimately, much of this earth and in the atmosphere. water will be returned to the visualized as a series of banks that air by plants through transpiration, store and continuously transfer water. a process whereby moisture The oceans are the largest bank, absorbed by the plants evaporates containing about 97 percent of the directly into the atmosphere from Earth’s water. The other banks, plant surfaces. In Alabama, about 60 though much smaller, are also percent of precipitation is returned to important. These include the the air by evaporation and atmosphere, glaciers and ice sheets, transpiration, or rivers, lakes and streams, soil evapotranspiration. Part of the moisture, and ground water. water that enters the soil zone moves downward to the water table. Ground Water evaporates from the water may discharge as springs or surfaces of the oceans and other seeps into streams, lakes, wetlands, water bodies and enters the or directly into the ocean, completing atmosphere as water vapor, the cycle. The hydrologic cycle goes eventually falling back to Earth as on forever, and involves all water on precipitation, usually in the form of and in the earth and in the rain or snow. Some of the rainfall atmosphere. 12

Ground water in Alabama is part of the global hydrologic cycle.

The oceans contain about 97 percent of the Earth's water. Only 0.3 percent of the Earth's water is fresh water in lakes, rivers, and aquifers. The other 2.7 percent is frozen in glaciers, is very deep salty ground water, or is located in water bodies not included above, such as salt water lakes. 13

Balancing Alabama's water budget

Water moves very slowly through Depending upon local hydrologic and some parts of the hydrologic cycle. geologic conditions, water can travel Some water stays in the ground for several miles underground in a few thousands of years and may days, or it may take hundreds or even penetrate miles below the surface. thousands of years to cover the Precipitation that falls onto glaciers same distance. The average rate of and ice sheets may also be trapped ground water movement in Alabama in ice for thousands of years. is about 1 inch per day. A drop of water moving at this rate would take Rates of ground water movement 174 years to travel 1 mile. are variable and difficult to measure. 14 WHAT ARE AQUIFERS?

Many people believe that ground usually represented as percent, of water occurs primarily in open pore space in the aquifer. This underground lakes or rivers. represents the storage capacity of the Although underground lakes and aquifer. A good aquifer may contain rivers do exist, the vast majority of 10 to 30 percent open space and ground water is found in the tiny therefore 90 to 70 percent rock, so openings called pores that occur its porosity is 10 to 30 percent. An between the grains in rocks, soil, and equally important aquifer property is sediment. Many rock formations are permeability. fractured, and large amounts of water can be contained in those fractures. Permeability is a measure of the Below the water table these interconnectedness of a pore or openings are filled with water. Even fracture system, and determines the in areas where the ground is dry, ability of a rock unit to transmit fluids. water-saturated material exists Not all porous rocks are permeable. everywhere at some depth, usually Impermeable rocks may contain from a few inches to a few hundred significant amounts of water, but feet below the surface. make poor aquifers because the water cannot move from pore to pore The upper part of the earth’s crust and be pumped to the surface. is composed of soil and many Permeability can be illustrated by the different types of rocks. Some types of rocks are able Even where the ground is dry, to store and transmit water water-saturated material exists better than others. Rock, sediment, and soil units that everywhere at some depth. contain significant amounts of producible ground water are called following example. An open pipe is aquifers (from the Latin aqua, water, totally permeable because its and ferre, to bring). Aquifers have two volume is all open space. If the pipe very important properties. The first is filled with gravel, about 25 percent is porosity, which is the amount, of the total volume of the pipe consists of interconnected pore 15

A pump test can reveal how much water an aquifer can yield to a well.

space and the pipe can still shut. This compression of pore transmit water, though not as quickly space usually does not occur at as before, because its permeability depths shallower than about 2,000 has been reduced. If the pipe is filled feet. Aquifers that produce sufficient with cement, very little or no water can quantities of water commonly occur pass through it, and its permeability at much shallower depths, so is near zero. The porosity of the compression is not a factor in the cement may not be much less than siting of most water wells. that of the gravel-packed pipe but the pores are not well connected. This Another concept critical to the illustrates why some rock formations, understanding of ground water while having significant porosity, availability and protection is that of cannot transmit much water and do unconfined and confined not make productive aquifers. aquifers. Unconfined aquifers consist of an upper unsaturated The porosity and permeability of portion above the water table and a aquifers tend to decrease with depth lower saturated zone below the water because pressure generated by the table. Some aquifers are overlain and weight of the overlying rocks underlain by layers of significantly squeezes the pores and fractures less permeable materials that restrict the flow of water 16

The time it takes ground water to travel from its point of recharge to point of discharge can be measured in days to years for shallow ground water, but may be centuries or millennia for deep ground water.

across the aquifer boundaries. water can be under considerable These aquifers are called confined pressure. When a well is drilled into aquifers. The less permeable layers a confined aquifer the pressure that impede water movement are forces the water in the well to rise called confining units. In Alabama, above the top of the aquifer itself. If confining units are generally the pressure is great enough the composed of clays, shales, and water will actually flow from the well chalk. Confined aquifers are at the ground surface without having completely saturated with water. to be pumped. Such flowing wells are Because the space the water common in and near the flood plains occupies in a confined aquifer is of major streams in the southern half restricted by the confining layer, the of the state, and are sometimes called artesian wells. 17

Recharge to a confined aquifer may occur far from the locations of wells producing water from that aquifer.

Also, it is important to note that surface or where the confining unit is where the confining unit is present absent. Thus, the area of recharge confined aquifers cannot be locally for an aquifer may be a long distance replenished, or recharged, by from where water from that aquifer is rainwater filtering down from the produced. For example, the city of surface. Infiltrating surface water can Dothan in Houston County pumps recharge confined aquifers only water from the Nanafalia Formation, where the aquifer is exposed at the a sandy geologic unit that, in that

Ground water moves at an average rate of an inch per day. At this rate it would take 174 years to travel one mile. 18

Flowing artesian well in Old Cahawba

area, is a confined aquifer. The that future generations will rely on in recharge area for the Nanafalia Dothan can be affected by activities aquifer is where it crops out at the in the recharge area of the Nanafalia surface, more than 30 miles north of Formation, 30 miles away. Dothan. It is important to understand this relationship because the water 19 KINDS OF AQUIFERS SAND OR SANDSTONE Aquifers in Alabama can be amounts of water but are restricted grouped according to the way water to the floodplains of major rivers and flows through them. Aquifers transmit thus are only of local importance. The water by porous flow, conduit flow, towns of Saraland and Satsuma in fracture flow, or by a combination of Mobile County use ground water from these. Porous flow is typical of sand aquifers deposited by the aquifers composed of sand or Mobile River. Sandstone is simply sandstone. These aquifers are sand that has been hardened into made up of sand-sized particles of rock by the heat and pressure other rocks that were broken down caused by deep burial for extremely by erosion, transported to their long periods of geologic time. Many present location by wind or water, and sand bodies and some sandstone deposited. Water is stored in and units are highly permeable, with moves through the open spaces, or porosity values that may exceed 25 pores, between the individual sand percent. Typically, water moves grains. Sand bodies can range in size slowly but steadily through sand and from a few square feet to thousands sandstone, making many sand and of square miles. Sand aquifers are sandstone aquifers reliable sources often found along rivers and streams of large amounts of ground water. where they Sand and formed as the sandstone stream Water moves slowly aquifers are the meandered back but steadily through most important and forth across sand and sandstone, aquifers in the floodplain. making many many parts of These aquifers, sandstone aquifers Alabama and sometimes generally called reliable sources of produce large watercourse large amounts of amounts of aquifers, can ground water. water. Because supply significant water moves slowly through the aquifer, there is 20

The three kinds of aquifers have differing pore networks and therefore transmit water at different rates.

more time to respond if the tendency of some sandstone ground water becomes aquifers to produce water containing contaminated. Also, sand and too much iron, which can stain fixtures sandstone aquifers tend to filter out and fabric and give the water a bad some contaminants as the water taste. moves slowly through the pore spaces. Disadvantages include slow One important sand aquifer in recharge if a sandstone aquifer Alabama is the Eutaw Formation. becomes depleted, and the Sands of the Eutaw produce fresh water from Aliceville to Eufaula. 21 LIMESTONE A second way that water moves spectacular, most dissolution cavities through an aquifer is by conduit flow. in limestone aquifers are small, even In conduit flow, water actually flows microscopic. Most ground water in through underground channels, or limestones occurs in these cavities conduits, in the rock. Conduit flow is and channels. Because these commonly associated with carbonate openings are irregular in shape and rocks, such as limestone and distribution, ground water flow can be dolomite. Most conduits are formed unpredictable and extremely fast, over thousands of years by sometimes up to several thousand dissolution, a chemical reaction feet per day through the larger between limestone and fresh water channels. in which the limestone is dissolved. Sometimes, large volumes of rock Springs are common in limestone can be dissolved, forming cavities aquifers, discharging water where and caves. Although cave formations water filled channels meet the can be fascinating and sometimes surface.

Stream pouring into a sinkhole, connecting surface water to ground water.

A total of nearly 90 million gallons of water each day flows from the three biggest springs in Alabama—Coldwater Spring (Anniston), Tuscumbia Spring (Tuscumbia), and Big Spring (Huntsville). 22

Caves are common features in limestone terrain. This cave is located in Madison County. Limestone aquifers have several aquifers may stop producing potential disadvantages. For altogether during dry summer example, sinkholes tend to occur in months or periods of over-pumping. areas underlain by limestone. A Fortunately, most of these wells sinkhole forms when the ground recover quickly when the fall rains surface collapses into an underlying come. Another potential dissolution cavity. Sinkholes are like disadvantage of many limestone huge drains and water entering them aquifers is the hardness of the water. is immediately introduced into the This means it contains large ground water system. If quantities of dissolved carbonate, contaminated water enters a sinkhole and does not readily produce a lather connected to a channel or cavity with soap. system capable of transporting large volumes of water, ground water can In spite of these disadvantages, become contaminated very quickly, limestone aquifers are important leaving little time to take action to sources of ground water in many protect it. Also, the water table in parts of Alabama. The Tuscumbia- limestone aquifers may fall rapidly in Fort Payne aquifer in , response to an increase in pumping for example, serves more than or a decrease in precipitation. As a 100,000 public water supply system result, some wells in limestone customers, although it is prone to all the problems which characterize limestone aquifers. 23 FRACTURED ROCK

The third way aquifers transmit Fractures also may or may not be water is through fractures. Aquifers well connected, and fracture- characterized by porous flow or dependent aquifers rarely contain conduit flow can enough water to also be fractured, make them reliable which enhances sources of water. the permeability of They are typically these aquifers. In used only when nonporous and more suitable insoluble rocks, aquifers are not fractures may present. Small provide the only springs are common way in which fluids in fractured terrain can be transmitted. wherever saturated Examples of such permeable fracture rocks include systems intersect sandstone in which the land surface. In the pores have Alabama, fractured been filled by DeSoto Park is in aquifers are most some secondary an area of fractured rock important in the material; shales; region and most igneous and metamorphic (see next section), where hard rocks such as granite and gneiss granitic rocks, remnants of the core (pronounced “nice”). These rocks are of the Appalachian Mountains, yield very dense and contain few open modest amounts of water from spaces except for fractures. fracture systems. Fractured granites Typically, fractures are concentrated and granitic rocks are major aquifers near the surface and are not in large parts of Coosa, Tallapoosa, distributed evenly over a large area. and Chambers Counties, and smaller parts of several neighboring counties. 24 ALABAMA’S AQUIFERS

Alabama is divided into five Rim—are composed of much older hydrogeologic provinces: the sediments that have hardened into Coastal Plain, Piedmont, Valley and rocks. Also, the rocks in these Ridge, , and provinces have all been structurally Highland Rim. These hydrogeologic deformed to varying degrees by the provinces are closely related to the forces that formed the Appalachian physiographic provinces. The Mountains. The rocks of the hydrogeologic provinces are defined Piedmont were strongly deformed to on the basis of differences in water the point of recrystallization by the bearing properties of rocks, rock deformational pressures. This type, structural geology, and means that original mineralogy and physiography. Such characteristics texture of Piedmont rocks were determine the types of aquifers in funda-mentally changed by mountain these areas. building. The rocks of the Valley and Ridge, protected to some extent by The Coastal Plain province the Piedmont, were highly folded and includes sediments such as sand, faulted. The rocks of the Cumberland gravel, and clay, as well as chalk and Plateau and the Highland Rim were some limestone deposited by seas less affected. The intensity of the that once covered the southern part structural deformation influences the of Alabama. Coastal plain sediments occurrence and quality of ground are relatively young compared with water in each province. The the rocks that make up the other boundary between the soft rocks of provinces and are mostly the Coastal Plain province and the unconsolidated, which means they hard rocks of the other four provinces have not been hardened into rocks. is called the fall line, because the The other four provinces—the change in rock durability fosters the Piedmont, Valley and Ridge, formation of waterfalls along this line. Cumberland Plateau, and Highland 25

Ground water provinces are regions characterized by certain kinds of aquifers. 26

The geologic map shows that each part of the state is underlain by different rocks, which control the nature and distribution of aquifers. 27 28 29 COASTAL PLAIN

The Coastal Plain is by far the of Alabama’s total agricultural water largest and most populous use occurs in the Coastal Plain. hydrogeologic province in the state. The occurrence and availability of Although most areas in the ground water in the Coastal Plain is Coastal Plain yield plenty of ground quite high; some Coastal Plain wells water, some areas do not. Near the can yield up to several thousand northern limit of the Coastal Plain, gallons per minute (gpm). Average strata (rock layers) are too thin to production per well is higher than in store large quantities of water, and any other province in Alabama. In major users have to augment their most parts of the Coastal Plain, wells ground water supplies by developing can be expected to yield more than other sources. The city of 50 gpm. To put this in perspective, a Tuscaloosa, for example, is located well producing 7 to 10 gpm is in the northern part of the Coastal adequate for most domestic Plain, and relies on Lake Tuscaloosa purposes. for its water because the ground water supplies there are insufficient Ground water resources in the to support the city. Coastal Plain are estimated at about 488 trillion gallons. Major ground Farther south in the Coastal Plain water users include the cities of is a part of Alabama which has Dothan, Enterprise, Jackson characteristic black, dense soils that (supplied by a spring), Montgomery are sticky when wet. This area is (which also uses surface water), underlain by chalk, a variety of Prattville, Selma, and Troy. Residents limestone, which is a poor aquifer. of the Coastal Plain, while including only 44 percent of the state’s population, account for approximately 63 percent of the total Eighty percent of ground water use. The per capita use public water supply is high primarily because of systems in Alabama agricultural use. More than 70 percent have at least one ground water source. 30

Flowing wells can waste millions of gallons of water. The rust colored material on the pipe is due to the iron content of the water.

Sinkhole in Shelby County, 1972. Sinkholes are common in parts of the Alabama Coastal Plain where limestone is near the surface. 31

In many areas wells must parts of the region. In much of the penetrate the chalk and tap deeper Coastal Plain springs yielding aquifers to supply ground water. between 10 and 100 gpm of water Because the deep aquifers are are moderately common. Rock types under high pressure, flowing wells are are interlayered sand, clay, and common. Although the deeper limestone, with many sand and aquifers contain an abundant supply limestone units capable of yielding of water, flowing wells can waste water to springs. millions of gallons of ground water, which can lead to long term depletion Ground water from subsurface of these deeper aquifers. sand and limestone is the primary water source for the City of Dothan, The Coastal Plain contains and is an important source to people sporadic springs, most of which are living in an area from Henry County found in the northern and southern to southern Choctaw County.

Flowing Well - Tuscaloosa County 32

Subsurface sands also supply supplies by salt water is a problem. ground water to communities in Salt water occurs at relatively shallow Escambia, Washington, Baldwin, and depths near the coast. Coastal Mobile Counties. Ground water in the freshwater aquifers can become southern Coastal Plain is produced contaminated if wells in these from wells ranging in depth from tens aquifers are pumped heavily, or of feet to nearly 1,000 feet. overpumped, enough to draw salt water into the wells. Salt water In some areas of the Coastal Plain contamination, or salt water located near the Gulf Coast, intrusion, is a problem in southern contamination of fresh ground water Baldwin County and can affect any coastal area.

Overpumping in coastal regions may lead to contamination of wells by salt water (salt water intrusion). 33

PIEDMONT

Piedmont is a French word small communities, but not enough meaning foothills. The Alabama for a large town or for commercial Piedmont is the southernmost use. exposure of a vast physiographic province that forms the foothills of Springs are more common in the the Appalachian Mountains and Piedmont than in the Coastal Plain, stretches all the way to Pennsylvania. but are not abundant. Typical The ancient crystalline rocks of the Piedmont springs yield 10 to 100 Piedmont are igneous and gpm of water from fractured metamorphic rocks and are the metamorphic and igneous rocks. most intensely deformed rocks in the state. Rocks in the Piedmont do not About 7 percent of Alabama’s hold much water compared to the population lives in the Piedmont, sands and limestones of the Coastal accounting for 5 percent (less than Plain. Most of the porosity in 19 million gpd) of the state’s ground Piedmont aquifers is fracture related, water consumption. The hilly terrain although soil and is unsuitable for large weathered rock near Water yields in scale agriculture, and the surface may exhibit only 3.5 percent of porous flow. Water the Piedmont are Alabama’s agricultural yields both from typically low, water use takes place fractures and from the highly variable, here. There are no relatively thin layer of and difficult to large cities in the weathered material predict. Piedmont except for near the surface Anniston, which uses (known as saprolite) water from Coldwater are typically low, highly variable, and Spring, one of the largest springs in difficult to predict. Generally, wells in the state. Even though Anniston is in the Piedmont yield enough water for the Piedmont, Coldwater Spring is domestic use, or sometimes for located in the Valley and Ridge province. 34 VALLEY AND RIDGE The Valley and Ridge province is The Valley and Ridge province is made up of folded and faulted characterized by northeast- sedimentary rocks (limestones southwest trending ridges and and dolomites, sandstones, and valleys. Rocks that are resistant to shales), and marks the southern end erosion, such as sandstone and of the Appalachian Mountains. chert, form the ridges, whereas easily Aquifers in the Valley and Ridge may eroded rocks, such as limestone and be dominated by porous, conduit, or dolomite, underlie the valleys. fracture controlled flow, depending Generally, valleys are better places on the rock type. Ground water is to locate wells than hill slopes abundant in the Valley and Ridge, with because ground water tends to flow limestone, dolomite, and sandstone away from hill slopes into the valleys. aquifers capable of producing more Because most of the valleys are than 100 gpm. A few wells can yield underlain by limestone and dolomite as much as 1,600 gpm.

Coldwater Spring, located in the Valley and Ridge province, supplies water to Anniston, located in the Piedmont province. 35

and therefore are prone to conduit The limestone aquifers in the flow, aquifers located in these areas Valley and Ridge feed many springs are relatively susceptible to ground including Coldwater Spring, which water contamination from the has an average discharge of 31.2 surface. million gpd. Few springs approach the flow rate of Coldwater Spring, but The Valley and Ridge accounts for springs in the Valley and Ridge 14 percent, or about 56 million gpd province typically yield 100 gpm or of the state’s total ground water use. more of water from limestone, Eighteen percent of Alabama’s dolomite, and other rock types. population lives in the Valley and Large springs are common in the Ridge and, although the water use Valley and Ridge because of conduit per person approaches the state flow in limestone and dolomite average, agricultural water use is low aquifers. (8 percent of the state total), because of the mountainous terrain. Trussville, in Jefferson County, is the largest single consumer of ground water in the Valley and Ridge province. The cities of Attalla and Leeds also use ground water to supply virtually all of their water needs.

Contaminated water may enter the subsurface directly through sinkholes. 36 CUMBERLAND PLATEAU The Cumberland Plateau in north The Cumberland Plateau contains is underlain by 18 percent of Alabama’s population relatively flat-lying rocks. The and accounts for 12 percent of the Pottsville Formation, which consists state’s total water consumption, 9 of interbedded sandstone and shale, percent of the total ground water use, is the major aquifer in the Cumberland and 12 percent of the total agricultural Plateau, with the Bangor Limestone water use. Ground water supplies in and the Hartselle Sandstone the Cumberland Plateau, although supplying significant amounts of sufficient for smaller consumers, ground water in some parts of the cannot sustain the needs of a major province. Water from the Pottsville user. The towns of Eldridge in Walker contains enough iron in places to County and Hodges in Franklin stain fixtures and affect the taste of County depend on ground water to the water, and water from the Bangor supply their needs. and to a lesser extent the Hartselle, is hard (see hard water). Individual wells in the province can yield as much as several hundred gallons per minute, but 20 gpm or less is typical. Springs in the Cumberland Plateau are moderately common, yielding 10 to 100 gpm of water from limestone, sandstone, and shale.

Ground water supplies in the Cumberland Plateau, although sufficient for smaller consumers, cannot sustain the needs of a major user. Spring Source - Bridgeport, Alabama 37 HIGHLAND RIM As is the case in many areas in amounts of limestone. Caves and Alabama, ground water is unevenly sinkholes are common, and distributed in the Highland Rim. High contamination of ground water is a capacity wells, producing from 100 serious concern. Much of the ground to more than 1,000 gpm, occur in the water in the Highland Rim is hard and limestones and dolomites of the Fort locally contains objectionable Payne-Tuscumbia aquifer system in amounts of iron, carbon dioxide, or the northern part of the Highland Rim, hydrogen sulfide. and in the Bangor Limestone in the southern part. The Hartselle Thirteen percent of Alabama’s Sandstone and several other population lives in the Highland Rim, aquifers of local importance supply accounting for 12 percent of minor amounts of ground water to the Alabama’s total water use. Only 9 southern part of the province, mostly percent of the state’s total ground from wells producing 10 gpm or less. water consumption occurs in the Highland Rim. Part of the reason for The major aquifers in the Highland this is the Tennessee River system, Rim province contain significant which provides plentiful surface water

The Huntsville Lincoln Well is the largest diameter well (20 feet) in Alabama. It can pump up to 3200 gallons per minute. 38

to users throughout the province. common in the Highland Rim Agricultural water use has increased because of conduit flow in limestone dramatically in the past few years and chert aquifers. because the practice of irrigation is becoming more widespread in the Huntsville is the largest ground area. water user in the Highland Rim, getting most of its water from two Springs in the Highland Rim are wells and Brahan Spring (Huntsville abundant and typically yield more Big Spring). In addition, the Madison than 100 gpm of water from County Water Authority and the limestone, chert, and other rock Limestone County Water Authority types. The Highland Rim includes two depend entirely on ground water for of Alabama’s three biggest springs. their water supply. Madison County Tuscumbia Spring, also known as Big has been a leader in the Spring, supplies water to the city of development of local ground water Tuscumbia. Large springs are protection efforts.

Tuscumbia Spring, one of Alabama's largest, is located in limestone terrain. 39 GROUND WATER MYTHS WATER WITCHING Water witching (also called to drill a well and not find water. divining or dowsing) is an ancient Dowsers in Alabama can easily build method of finding ground water. The up excellent “success” rates, oldest detailed description of because in most of our state ground dowsing was published in 1556, but water is not that hard to find. In areas cave paintings at least 6,000 years where water is more difficult to find, old appear to show a dowser at work. dowsers do no better than random But does it work? Alas, there is no drilling at locating usable quantities hard evidence that supports the of water. The U.S. Geological Survey claims of any water dowser. In most has two publications on dowsing. parts of Alabama it would be difficult Both are listed in the reference section.

The Mount Carmel public water supply well in Pike County is the deepest in Alabama, at 2723 ft. 40 UNDERGROUND STREAMS AND LAKES

As mentioned earlier, and most ground water occurs in underground lakes, rivers, and even small cavities and fractures in that waterfalls exist in Alabama. These “solid” rock. features are almost always associated with caves. At least five caves in Jackson and Madison Counties contain under- It is important to remember that ground rivers more than a mile long even in regions known for their that are large enough for canoeing. caves, such as northwest Alabama No one knows exactly how long these or the southern Coastal Plain from rivers are, because they all com- Choctaw to Geneva Counties, more pletely fill the cave passages at some than 99 percent of the space point. Such places remain largely underground is solid rock, not cave, unexplored because of the danger posed even to experienced cavers.

The beautiful cave formations and mysterious underground rivers form an eerie part of Alabama's natural environment. However, most underground water, even in cave country, is in holes too small to see. Bluff River Cave, Jackson County, Alabama.