Appendices

A Guide to Tennessee’s Water Resources by Hydrologic Region^[1]

1. River Basins, Geology, and Regional Water Supply

The three “grand political divisions” of Tennessee can be further divided into six regions or provinces based on geology and physiography. These are the Blue Ridge Mountain Province, the Valley of the Tennessee or the Ridge and Valley Province, and the Cumberland Plateau which comprise East Tennessee; the Highland Rim and the Nashville Basin which comprise Middle Tennessee; and the Gulf Coastal Plain which is equivalent to West Tennessee.

The physiography and soil characteristics of the various provinces of the state have very important consequences for water policy. Where soils are shallow and the base rock is relatively impermeable, both ground and surface supplies are undependable. Major portions of Tennessee fail in this category. On the other hand, important areas of the state do have large and dependable ground or surface water supplies. This means that it may be necessary to have a water policy that makes separate provision for different areas of the state. The amount of planning and regulation needed in an area of shortage may be quite different from what is needed in a surplus area.

Nearly all of Tennessee lies in the Cumberland, Tennessee, or lower Mississippi River Basins. One per cent of the state drains into the Green and Conasauga Rivers in Kentucky and Georgia, respectively. Of the 41,800 square miles of land in the state, the Tennessee River drains about 55 %, the Cumberland drains 25 %, and the Mississippi drains 19%. The population of the state is concentrated around these rivers and their major tributaries. Each of the four largest cities of Tennessee is on the main stem of Mississippi, Tennessee, or Cumberland. Most towns of more than 5,00 population are on an important watercourse.

2. Water Resources in the Blue Ridge Province

The Blue Ridge Province of Tennessee is the mountainous area lying along the entire eastern boundary of the state. The mountains are the Unaka Range of the Appalachian Mountains and elevations range up to nearly 7,000 feet. The underlying rock structure consists of crystalline granites, schists, and gneisses and partly crystalline sandstones, shales, and conglomerates.

Soils tend to be rocky and sandy and are productive for timber. In some valleys and on general slopes there are soils of agricultural value. About half of the land is in forest.

Ground Water. The generally low‑quality soils and the transportation difficulties created by the terrain have restricted population growth in the Blue Ridge province. Although a few towns do obtain water from wells and many large springs exist, it seems unlikely that this area will be developed to use ground water as a major source of supply.

Surface Water. The streams of the eastern mountains are large and their flows are dependable. Several of the major tributaries of the Tennessee River rise in North Carolina and flow across the Blue Ridge province and the Valley of East Tennessee. Flows for the lowest month on record usually range between 0.1 and 0.3 cubic feet per second (c.f.s.) per square mile drained, and are more than for any other region of the state. Average flows per square mile drained are about the same as for other parts of the state, and usually range from 1 to 2 c.f.s. In the southern part of the area runoff is somewhat higher, being from 2 to 3 c.f.s. on the average, and as much as 0.7 for the maximum month on record.

Low flows during the average year are substantially higher than record flows. USGS investigations indicate that on the average only once in two years will the minimum discharge for a three‑day period fall below 0.44 c.f.s. per square mile for the area drained by the French Broad River above Newport. Equivalent minimum flows for other areas in the mountain region are mostly about 0.3 or 0.4 c.f.s. per square mile. Where the discharge of a stream is 0.3 c.f.s. per square mile, the yield of the stream will be 20 million gallons a day for each 100 square miles drained. The quality of the surface water in this region is generally very good. The tributary streams have very soft water, usually less than 25 parts per million of hardness.

3. Water Resources of the East Tennessee Region or ‘Ridge and Valley’ Province

The Valley of East Tennessee lies between the Blue Ridge Mountains and the Cumberland Plateau and consists of low ridges and broad valleys running from the northeast to the southwest. Limestone, sandstone, and shales are 2,000 to 6,000 feet thick and usually form red and grey loams valuable for general farming in the valleys. Considerable acreage is in forest. Although the valley is not the largest geographic region of the state, it contains nearly one-third of the population of the state.

Ground Water. General geological evidence indicates that large wells would be difficult to develop. However, actual ground water development by industries and municipalities in the valley is second only to the development of the Gulf Coastal Plain in west Tennessee. Many towns and industries use from several hundred thousand to two million gallons of ground water daily. Pollution of ground water is a problem, as it is in other limestone areas of the state.

Surface Water. The Tennessee River and its tributaries, the Holston and the Clinch, traverse the entire length of the valley. Other major tributaries such as the French Broad, the Little Tennessee, and the Hiwassee Rivers cross many miles of the valley before joining the Tennessee. Flows on these main streams and on many tributaries are large. Natural flows have been substantially modified by the extensive system of TVA dams.

4. Water Resources of the Cumberland Plateau

The Cumberland Plateau is the highest area between the Smoky Mountains and the Mississippi River; it extends from eastern Kentucky southeast through Tennessee and Alabama. The plateau is relatively flat except in the northeast, and beds of sandstone, conglomerates, shales and coal underlie it. The soils of the plateau are usually moderately fertile loams. Over two-thirds of the region is forested.

Groundwater. In general, wells must be drilled into the permeable sandstone beds in order to obtain water. Sufficient quantities for domestic supplies can usually be had from wells less than 100 feet deep. Larger supplies can be obtained at greater depths, the water usually rising to easy pumping distance of the surface. A number of towns on the plateau depend on wells forpublic water supplies. Other towns depend upon springs, but these are usually in areas where the plateau has been eroded to the level of the Highland Rim or the Sequatchie River basin.

Surface Water. Stream flows of the Cumberland Plateau are not dependable, and a number of streams draining over 100 square miles have, at times ceased to flow. Flows for the lowest month on record range from 0.00 to 0.06 c.f.s. per square mile.

5. Water Resources of the Highland Rim

The Highland Rim surrounds the Nashville Basin and extends from the Cumberland Plateau to the Tennessee River. The rim is from 500 to 1,000 feet lower than the plateau and is underlain by sandstone, limestone, shales, and chert. The soils formed from Highland Rim rocks vary from fertile loams at the higher levels to cherty barrens and grey silt loams where the rocks are worn down to the lower levels. The western part of the rim near the Tennessee River is heavily forested, while over the remainder of the region less than one acre in two is forested.

Ground Water. Water is available in gravel, sandstone, and solution channels in limestone. The underlying limestone is dense, so that water is usually found in joints and openings formed by solution. There is little assurance that any particular well drilled will hit one of these openings. Yields are usually low, and few wells drilled will exceed 5 to 10 gallons per minute. Domestic and stock water is usually obtained from dug wells less than 100 feet deep on the southern part of the Highland Rim. Throughout most of the area water can be obtained in small quantities from drilled wells less than 200 feet deep. It is generally inadvisable to go deeper than 350 feet because the rock becomes more dense and the chemical quality of the water decreases. Water supplies often are reduced or disappear during summer months, and bacteriological contamination is not uncommon.

Over the region, springs form the most reliable source of ground water. Springs yielding over 100 gallons per minute are common and a number are known to exceed 1,000 gallons per minute. Many communities depend upon springs for public water supplies.

Surface Water. The Cumberland and the Tennessee Rivers are the major surface waters of the Highland Rim. The Cumberland enters the state at the northeast corner of the rim and leaves at the northwest; the Tennessee crosses the entire width of the state at the western boundary of the rim. The discharge of each of these rivers is large and control through upstream reservoirs is extensive.

Uncontrolled stream flows are well sustained on the southern part of the Highland Rim, but are less adequate in the north. Flows for the minimum month of record are about 0.05 c.f.s. per square mile in the north and in some areas overlapping on the Cumberland Plateau or the Nashville Basin. In the southwest and to a lesser extent in the southeast, erosion and surface drainage have progressed further and here minimum flows ranges between 0.1 and 0.3 c.f.s. per square mile. Most of the Highland Rim is underlain by limestone and the streams tend to be fairly high in dissolved minerals and fairly hard. The areas drained by the Elk, Duck, parts of the Cumberland and the Collins River yield water of about 100 parts per million total hardness.

6. Water Resources of the Nashville Basin

The Nashville Basin is a plain in the center of the Highland Rim. The boundaries of the basin are slowly expanding through erosion at the edges of the rim. The underlying rock is limestone and calcareous shales. The soils are very fertile and suitable for general farming; however, they are often so shallow that they are suited only to pasture or timber. The largest concentration of population is in the Nashville urban area on the Cumberland River. Secondary streams intersecting the basin include the Duck, Stones, Harpeth, Caney Fork, and Elk rivers.

Ground water. Over parts of the Nashville Basin water is unobtainable at shallow depths. Where shallow water is available, drilled wells yield only about 3 to 5 gallons a minute. Most areas can be expected to yield domestic quantities of water at less than 200 feet depth; yields will usually be less than 10 gallons a minute. A high percentage of dry, or non‑water bearing wells, occurs.

There are aquifers in the upper part of the Knox dolomite section underlying the basin. This section is within 400 feet of the surface in the center of the basin, and drops to more than 1,000 feet at the fringes. In some areas of the Nashville Basin, usually near the Highland rim, there are flowing artesian wells. There are also a number of large springs in the region, and several towns use these for their public water supply. The quality of ground water in the basin is often unsatisfactory. Water from deep wells tends to contain excessive minerals, hardness is often fairly high, and many wells yield nonpotable sodium chloride or calcium‑sulfate water.

Of the three heavily populated regions of the state, the Nashville Basin has the least to offer for ground water resources.

Surface Water. The dams on the Cumberland and its tributaries help to maintain rather large, minimum flows on this river as it passes through the basin. For no other part of the region can it be said that there are large, assured water supplies, either ground or surface. Two important tributaries of the Cumberland River originate in the central basin; one is the Harpeth River and the other is the Stones River. The Duck and the Elk rivers and their tributaries drain the southern half of the basin. In general Duck River tributaries in the Nashville Basin will cease to flow during moderate or extreme drought. Low flow is somewhat better for the Elk River tributaries.

7. Water Resources of the Gulf Coastal Plain

The Gulf Coastal Plain, or the Mississippi Embayment, of western Tennessee extends from the Tennessee River and the Highland Rim to the Mississippi River. Deposits of sand and clay range from 3,000 feet in thickness at Memphis to a vanishing point at the Highland Rim. The early deposits are of marine origin, and rise to the surface in the east; while in the west near the flood plain of the Mississippi is the more recent loess.

Ground Water. Without question the ground water resources of west Tennessee are much better than for any other region of the state. The unconsolidated strata of sands constitute large reservoirs and means of replenishment for ground water. The three principal water-bearing beds are the sand formations named Wilcox, which is up to 1,900 feet thick; McNairy, which is up to 400 feet thick; and Eutaw, which is 250 feet thick in some places. Because of the physical properties of this sand it appears that large quantities of water are available throughout the region. The immense size of the storage space is a product of the depth of the water-bearing sands and the tens of thousands of square miles that constitute the Gulf Coastal Plain. These ground waters are recharged over the extensive areas of the plain where these formations surface and where overlying strata are permeable to any extent.

Surface Water. The Mississippi River forms the western boundary of the Gulf Coastal Plain in Tennessee, and most of the plain drains into the Mississippi through the Obion, Hatchie, and Wolf rivers. The Tennessee River forms the approximate eastern border of this region, and its tributaries, the Big Sandy, Beech, and smaller streams, extend short distances into west Tennessee. In general the minimum monthly flows are dependable and range between 0.1 and 0.2 cfs per square mile. West Tennessee is relatively flat and the underlying formations are unconsolidated so that silting and turbidity are common problems.

8. Precipitation and Its Variation: Policy Relevance

Much of the precipitation falling on Tennessee comes during the winter months. The summer and early fall are dry seasons for most of Tennessee. It is during this period that many uses, and especially irrigation, are at a maximum. The combination of various climatic factors such as wind, humidity, and temperature is such as to bring the rate of evaporation to a peak during the summer months. Important portions of reservoir storage and soil moisture are lost through evaporation. Evaporation from vegetation and soil probably exceeds rainfall during the summer and early fall in many parts of the state. This rainfall deficiency accounts in large part for both the low stream flows and the large withdrawals of water by various users at the critical season.

Normal rainfall is usually high in all parts of Tennessee but is highest in the southern and eastern parts of the state. While most of the state has experienced a thirty‑year average of from 50 to 55 inches of rain, a few areas have had over 55 inches. In the north there are regions with less than 50 inches of precipitation, while one substantial area of less than 45 inches centers around Johnson City and Morristown. Some months of the year are relatively dry in Tennessee even when annual precipitation is normal. Rainfall of less than 4 inches a month can usually be expected in August, September, October, and November. The first part of this period is accompanied by high rates of evaporation due to summer temperatures, so that more, rather than less, rain is needed to maintain runoff and ground water levels at that time.

National Weather Service reports show that in five out of every seven years droughts have occurred during the July through October period. For this purpose a drought is a period of at least 21 days with less than 0.25 inches of precipitation. The occurrence and frequency of such periods is important, especially for agriculture. Tennessee often has more than one drought a year. During the period 1871‑1953 there were a total of 112 droughts, or 1.3 per year.

Recurring dry spells are the normal thing, then, even during wet years; and a suitable water policy for the state of Tennessee must take account of this fact. The four-month period with the highest rainfall is December through March. This high rate of precipitation is coupled with the lowest rate of evaporation for the year; thus there is an excess of water that must go into temporary storage or into stream runoff. The months of December through March are a period of frequent floods.

In order to plan for predictable shortages of water and for measures to alleviate them, it is necessary to know how rainfall varies between one year and another and how this variation influences the amount of water available for use. During the period since 1884 annual rainfall in Tennessee has ranged between 36.7 and 62.9 inches. Merely as an illustration, rainfall was less than 45 inches during seven of these twenty‑five years between 1929 and 1955 and during six of the years from 1884 through 1929.

More than half of the water falling on the state evaporates and does not run off. The amount that evaporates depends upon the amount and timing of rainfall and upon temperatures, soil conditions, and many other factors. Evaporation cannot be measured directly for Tennessee but it can be computed for various watersheds in the State.

Rainfall minus runoff nearly always falls within the range of 25 to 35 inches in Tennessee watersheds. For the larger watersheds the range is narrower. Evaporation approximates rainfall minus runoff in most watersheds, the difference being a net gain or loss in ground flows. For example, in 1954 rainfall minus runoff in sixteen Tennessee Valley watersheds ranged from 27.6 to 36.0 inches and the median was 30.5 inches. Twelve of these sixteen were 1.9 inches or less from the median. The size of drainage areas ranged from 104 to 2,571 square miles, while rainfall ranged from 41.2 to 59.5 inches, with a median of 48.3 inches. Runoff varied from 11.0 inches to nearly three times as much, 30.9 inches. Rainfall in the Tennessee Valley above Chattanooga in 1954 was 48.0 inches while unregulated flow at Chattanooga was the equivalent of 18.1 inches, a difference of 29.9 inches.

The average loss of water to evaporation in Tennessee -- 30 inches -- tends to be less during dry years and more in wet years. When rainfall is 45 inches in Tennessee, not more than 15 inches of runoff can be counted upon. In 1941, a record dry year, rainfall was 36.7 inches, and runoff was an estimated 6.7 inches, or 13,500 million gallons a day. This is one‑third of the normal supply statewide of 40,600 million gallons a day and less than half of what has been available during some recent dry years.

APPENDIX B:

Stakeholder Survey

Thank you for agreeing to participate in this study. We are doing a study with the University of Tennessee regarding challenges facing future water use in our state and its communities.

This will take a few moments of your time. The responses will remain confidential. If you prefer not to answer a question, that’s fine. Please e-mail the completed survey to Valerie Diden at vdiden@utk.edu.

1. Can you recall the drought of the late 1980s (especially 1989):

Yes, remember (go to #2).

2. How did you know that there was a drought? What indicators were there?

3. Did this drought affect you, or the people (or organizations) that you work with in any way?

Yes. Please describe how:

No (go to #5).

Don’t know, can’t recall (go to #5).

4. As a result of this drought, did you, and/or the people (or organizations) you work with change the way they used or managed water?

Yes. Please describe how:

No.

5. Would you say that we are currently experiencing a drought, or a below-normal level of precipitation/rainfall in this region?

Yes.

No (go to question #7)

Uncertain/don’t know (go to question #7).

6. In your opinion, will this current drought affect the way you, the people you work with, or the organizations you work with, use or manage water?

Yes. Please describe how:

No. Our organization is concerned with protecting the streams and rivers of the state but feel they have no control over drought situations. It will effect our recreational times on water but feel it is out of our control.

I work at a hospital and they are usually are not effected by this type of situation.

Uncertain, don’t know.

7. What is (are) the source(s) of water you use? Metro Water System

8. Do you know how much water is used, on an average annual basis, by you(r) (constituents)? Yes, amount:

_ No

Don’t know, uncertain

9. What do you forecast for your constituents’ water use for the next 10 years?

Cannot predict the usage

10. Do you have any worries about your water supply?

Yes. What are they?

No.

Uncertain, don’t know.

11. One challenge the state of Tennessee is facing in regards to water supply is competition among people over the same ground- and surface water sources. In your experience, does this competition pose a problem to the way you, or the people or organizations with whom you work, conduct business? Or, do you foresee this as a problem in the future?

Yes. Please describe: Concerned over impoundments/dams, etc. that some cities are trying to do to insure a water supply for their communities¼

No.

Uncertain, don’t know.

12. Across the nation, a number of ideas have been discussed on how a state facing competition over sources of water supply might better deal with its problems. Some of these ideas are discussed below, and we would like your reaction to them (i.e., support, don’t know, don’t like.) If you prefer not to answer one, that’s fine.

a. Develop and maintain a statewide set of data on stream flow, groundwater levels, water withdrawals from surface and groundwater sources, and projected use by major users. One possible use for this could be to make decisions over water allocation:

b. Develop and maintain a statewide planning process that would require communities to plan water resource investment decisions, such as where, when, and how to acquire more water:

c. Develop and maintain a process for permitting water withdrawals from streams and groundwater sources, including diversion of water across or between different watersheds or basins:

Consumptive use – Use of water in a manner that makes it unavailable for use by others, generally because of absorption, evaporation, transpiration or incorporation in a manufactured product. In some instances, when water is returned to a stream at a distance downstream from the point of diversion, the use may be consumptive as to users immediately below the point of diversion, but nonconsumptive as to users below the point where water is returned.

Cooling water – Water used for cooling in an industrial process or in generation of power. After use, it usually has a higher temperature than that of the stream or lake into which it is discharged and so may constitute a source of thermal pollution.

c.w. consumption – The amount of cooling water lost primarily by evaporation caused by increase in temperature.

Correlative rights doctrine – (1) A doctrine requiring the sharing of groundwater shortages by overlying landowners; accomplished in some states by prorating the supply on the basis of overlying acreage. (2) A doctrine that applies surface riparian law to groundwater.

Depletion – withdrawal of a resource, such as surface water or groundwater, at a faster rate than it is being replaced.

Diffused surface water – Water lying or running on the surface of the land, but not in defined streams or water bodies, because of rain, melting snow, or floods. This water is generally not subject to water allocation rules.

Divide – The boundary between two drainage basins, frequently along a ridge line or a line connecting peaks.

Domestic uses – Household uses of water, such as drinking, cooking, washing, and watering livestock and a garden. Under traditional riparian law, these uses are given preference over "artificial" uses such as commercial irrigation or manufacturing.

Doctrine – A rule, principle, theory, or tenet of the law; as, e.g. Clean hands doctrine, Public trust doctrine.

Drainage basin – An area of the land surface that gathers water resulting from precipitation and contributes it to a stream, a stream system, another body of water or to a central point. The entire drainage basin therefore possesses a common outlet for its surface runoff. Syn. Catchment area, water shed.

Drawdown – The distance by which the surface of a waterbody is lowered by the withdrawal of water through pumping, artesian flow or other release.

Groundwater d. – (1) The lowering of the piezometric surface or water table as a result of groundwater withdrawal. (2) The difference between the height of a water table and the height of the water in a well. (3) Diminished pressure in an aquifer as a result of groundwater withdrawal.

Drought – A prolonged period of dry weather characterized by an absence of or a deficiency in rainfall. There are various quantitative measures established to try to determine a drought. In qualitative terms, however, it usually causes a partial crop failure, a hydrologic imbalance or an interference with the ability to meet normal water demand.

Ecosystem – A population of interdependent living organisms and the distinct environmental context to which they relate. The whole is characterized by biological, chemical, and physical linkages.

Effluent – (1) An outlflowing of a stream or other waterbody. (2) Any fluid emitted by a source such as a stream, reservoir, or a basin, including a partially or completely treated waste fluid that is produced by and flows out of an industrial or wastewater treatment plant or sewer.

Ephemeral stream – A stream or a portion of a stream whose channel is dry except after precipitation. The stream channel is above the water table and receives little or no water from springs or snowmelt.

Excess water – the amount it is believed safe to withdraw from a water source from whatever flow is available at the source (cf. Water withdrawn at a given river mile in a river or drawn from a spring and not returned to the streambed. and stored or drawn from a well or several wells over an aquifer. Water held in storage capacity is a factor here. See Safe Yield (below)

Federal land – Any land belonging to the United States, either by virtue of sovereignty or by acquisition from state or private ownership.

Foreign water – Water in a stream or other body of water that originated in another drainage basin. By definition this only happens by human action or natural catastrophe. If an area drains naturally into another (usually larger) drainage basin, it is not foreign. Cf. Water flowing from a tributary to the Tennessee to the Tennessee, thence to the Ohio River, into the Mississippi and to the Gulf can be said to flow in one large drainage that is a part of the Mississippi River drainage.

Groundwater – Subsurface water from which wells and springs are fed. In a strict sense groundwater applies only to water below the water table.

Groundwater recharge – Replenishment of groundwater naturally or artificially.

Hydrologic budget – An accounting of the inflow, outflow, storage and evaporation of water from an hydrologic unit, such as a drainage basin, aquifer, soil zone, lake or reservoir, and expressed by the hydrologic equation as the relationship between evaporation, precipitation, runoff, and water storage.

Hydrologic cycle – The process involving the continuous circulation of water from the oceans and the land surface of the earth to the atmosphere through transpiration and evaporation, and its eventual return to the earth's surface through various forms of precipitation.

In-stream use – Any use of water that does not require diversion or withdrawal from the natural watercourse, including in place uses such as navigation and recreation as well as power generation that requires a continuous flow.

In-stream appropriation – An appropriation in which water is left in a stream, river or lake (rather than diverted from the stream, river, or lake) at a particular place to provide for fish, wildlife, scenic beauty, waterborne recreation, environmental protection, or similar purpose. In-stream appropriations generally may only be made by a government agency.

Interbasin transfer – The physical conveyance of water from one watershed to another.

Irrigation – The application of water to lands to meet the water needs of plants not met by precipitation.

Irrigation return water – Water from irrigated farmlands that has been leached out of the upper layers of the soil.

Mine – To use up a resource without making provision for replenishment, as, for example, water from an underground reservoir.

Municipal water supply – Water to be distributed through a central system, whether municipally or privately owned, to users in an urban area, for both domestic and commercial uses.

Natural uses – These include traditional domestic water uses, such as drinking, cooking, laundry, and other uses necessary for the immediate sustenance of a household.

Navigable water – A stream, river, lake, arm of the sea, or other body of water that could be used for commerce, trade, transportation, or fishing. There is a federal definition and also a Tennessee state definition which differ slightly.

Nonconsumptive use – Use of water with return to a stream or body of water of substantially the same amount of water as was withdrawn, thus a use in which only insignificant amounts of water are lost by evapotranspiration or incorporation in a manufactured product.

Nontributary groundwater – Underground water (in an aquifer) that is so situated that it neither draws from nor contributes to a natural surface stream in an measurable degree.

Percolation – Movement through the pores or interstices of a substance, as water moves through rock or soil.

Farm waste percolation – Irrigation water in excess of what is consumptively used in a crop area, including both surface drainage to other areas and water intercepted by drainage systems moving through the root zone to the water table.

Perennial stream – A stream that carries water throughout the year and is generally fed by groundwater. The water surface of a perennial stream generally lies below the water table of the groundwater source.

Piezometric surface (potentiometric surface) – An imaginary surface representing the level to which groundwater will rise in a well as a result of the pressure under which it is confined in an aquifer. If, at a given location, water from different depths in the aquifer will rise to different levels, then the aquifer has more than one piezometric surface.

Point source - An origin of waste discharges that can be identified specifically, such as a municipal sewage system, an industrial plant or an animal feed lot.

Potable – Suitable for drinking.

Precipitation – The discharge of water, in either liquid or solid form, from the atmosphere to the surface of the earth, including rain, drizzle, sleet, snow, snow pellets, snow grains, ice crystals, ice pellets, hail, dew, and frost, usually measured in inched and hundredths of inches of equivalent depth in water.

Preferred uses – Water uses that have been given legal preference over other uses during times of water shortage.

Prescription – The use of water, exclusive and uninterrupted, for a certain period of time, which confers the right to continue the use of the water.

Public domain – Land owned, controlled, or heretofore disposed of by the United States federal government.

Public trust doctrine – This doctrine holds that the government has a trust responsibility toward certain natural resources, including water. The acceptance and effects of the doctrine vary from jurisdiction to jurisdiction. Among its effects, the doctrine can (1) provide the basis of government authority to regulate with regard to trust resources, (2) require heightened judicial scrutiny with regard to agency actions involving trust resources, (3) require governments to protect trust resources, and (4) limit the creation of private rights in trust resources. Although it is an old concept, the doctrine has been given renewed vigor and power as a tool for addressing Environmental concerns. ALSO Provides that submerged and submersible lands are preserved for public use in navigation, fishing and recreation and state, as trustee for the people, bears responsibility of preserving and protecting the right of the public to the use of the waters for those purposes.

Reasonable use doctrine – Also known as the American Rule, this doctrine allows a landowner to withdraw groundwater for reasonable uses on the overlying land without liability for harm to adjoining landowners; any beneficial use on the overlying land is considered reasonable.

Recharge – Addition of water, especially to a groundwater aquifer, to replace that which is withdrawn.

Artificial recharge –Recharge accomplished through the efforts of man, including seepage of irrigation water and induced infiltration from streams or wells.

Recharge area – An area through which an aquifer is replenished by force of gravity, usually where a permeable layer lies close to the surface.

Recharge basin – An artificial basin constructed in sandy deposits in order to promote infiltration thereby replenishing a groundwater supply.

Return water – Water diverted from a stream for irrigation purposes that, not having been consumed, passes directly back to a stream or other body of water or downward to the water table.

Return flow – Any water that is returned to a stream channel, a groundwater source, or a waterbody after being diverted or withdrawn for a purpose. Water diverted by a riparian for use\ which is then returned to the source after treatment. Return flow is legally required under riparian law and should take place within the same riparian landholding at which the water was originally withdrawn. Riparian land – Land lying along the banks of a stream or waterbody.

Riparian character is generally held to extend only to those lands in a single chain of title, so that a riparian owner's conveyance of the upland portion of the tract will remove the riparian character of the portion conveyed.

Riparian rights – The right of the owner of land abutting a stream or other natural body of water to use such water. At an early date, each riparian had a right to the natural flow of the stream, "undiminished in quantity and unaffected in quality", except for domestic use. More recently, the right to the natural flow has been modified to allow each riparian landowner to make a "reasonable" use of water on riparian lands. The "reasonableness" of a landowner's use is usually determined on a case-by-case basis by considering a number of factors associated with the use in question and the uses being made by competing riparian landowners.

Runoff – That portion of precipitation that would ultimately reach a stream without the intervention of man.

Safe yield – An ambiguous term that may refer to withdrawal of groundwater from an aquifer at a rate that (1) does not exceed average annual recharge to the aquifer, (2) does not result in continued withdrawing of groundwater from storage, (3) does not result in an "overdraft" or "mining" condition, or (4) does not produce an undesirable result.

Seasonal storage – Storage of water during that portion of the year when an excess occurs in the source. See Extra water (above).

Spring – A place where, without human modification, water issues from a rock or soil onto the land or into a body of water. The occurrence of a spring is dependent upon the location of permeable and impermeable rock layers, the level of the water table and on the local topography.

Storage – the long term collection of water, either in surface or underground reservoirs, for future use.

Storage capacity – Extent of ability to hold or accommodate.

Active storage c. – The volume of water normally available for release from a reservoir, the amount contained between the maximum level for which the dam is designed and the minimum level below which water will not normally be released.

Conservation storage c. – Amount of water that can be held in a reservoir for purposes other than flood control.

Dead storage c. – The volume of a reservoir below the level of the lowest outlet; the amount that cannot be drained by gravity through the outlets.

Flood control storage c. – The space in a reservoir allocated for retention of flood inflows to prevent or abate downstream damage.

Gross reservoir c. – The total volume of a reservoir from the bottom of the reservoir to the normal maximum operating level, including dead storage but not surcharge.

Surcharge storage c. – The volume of a reservoir above the maximum level for which the dam is designed, up to either the crest of an uncontrolled spillway or to the full-pool level with the gates closed.

Storage right – Water interrupted in its natural gravity flow and detained for later beneficial use.

Stream flow – The water that is flowing in a stream channel. The term is used synonymously with stream discharge to indicate the rate or quantity of water flowing in a stream.

Stream flow depletion – The amount of water lost from a stream in a particular area as measured by the difference between the amount flowing into and the amount flowing out of the area.

Sustained yield – (1) the quantity of a resource, such as groundwater, that can be withdrawn within a given period of time without reducing the total quantity available over the long run. (2) The amount that will be replaced or is renewable.

Thermal pollution – Impairment of water quality by rise in temperature from geothermal, industrial, or other cause.

TMDL – Total maximum daily load. The entire quantity of a pollutant that a body of water can receive without exceeding water quality standards. Used as a legal device, it includes point sources and nonpoint sources of the pollutant and may include a margin for error and a margin for future growth. The TMDL is arrived at based on the flow of water in a stream. For entities relying on calculations to set discharge rates, when water flow is diminished by increased withdrawals and/or drought, margins may disappear. When this happens, either excess must be spilled resulting in pollution (as with a municipal water treatment system);or process interruption may be required (as with an industrial use).

Transbasin removal – The removal of water of a natural stream from its natural basin into the natural basin of another stream.

Transpiration – The process by which water vapor is transferred to the atmosphere from living plants or the amount of water lost in this manner.

Tributary - A stream that empties into and contributes its waters to another stream.

Tributary drainage – The area from which water drains by gravity into a watercourse.

Tributary groundwater – Groundwater hydraulically connected to a stream so that groundwater withdrawals affect the stream supply and thus may be administered in conjunction with a surface water allocation system.

Unsaturated zone – A subsurface soil zone, also called the aeration zone, that lies above the zone of saturation (the water table), and is characterized by the saturation of soil interstices partially by water and partially by air. The interstitial water tends to move under gravity despite being held by molecular capillary forces.

Water course – A place on the earth's surface where water flows, regularly or intermittently, in a defined channel.

Water cycle – The continuing process by which atmospheric water condenses, falls to the surface of the earth in any form of precipitation, runs through surface or subterranean passages toward the sea and again returns to the atmosphere by evaporation from either water or land surface.

Water quality standard – An in-stream standard specifying, usually, the maximum allowable concentration of a pollutant. Water quality standards may be numeric (for example, one part per million of copper) or narrative ("no toxic substances in toxic amounts"), may be chemical specific or stated in terms of whole-effluent toxicity. They may be designed to protect humans, aquatic organisms, or wildlife, such as eagles and mink that eat fish. Special water quality standards may be developed for sediments, groundwater, or the protection of wetlands.

Water right – A legally enforceable right to use water. Typically, a water right refers to the right to water from a naturally occurring source, such as a stream, river, lake or aquifer.

Water-right value – The value of the right to use water from a given source.

Watershed – (1) The region that is either drained by or contributed water to a body of water such as a river, stream, or lake. (2) The area within a divide above a specified point in a stream.

Water table – The upper surface of an underground layer saturated with water; the level to which water will naturally fill an excavation or the surface between the zone of saturation and the zone of aeration.

Well – An artificial pit, hole, or other excavation that is often walled or lined and is sunk into the ground in order to penetrate water-yielding rock or soil in order to withdraw, usually by pumping, water for use at the land surface.

Artesian well – A well releasing groundwater under such natural pressure that pumping is not required to bring it to the surface.

This glossary is taken in large part from the Glossary of Water Related Terms prepared by Elizabeth Slusser Kelly, in Beck, Waters and Water Rights. Other sources include: Black's Law Dictionary 6^th Edition (1990) and Glossary by Patricia Pinson in Wright, Kenneth R., Ed., Water Rights of the Eastern United States, American Water Works Association, (1998) (She cites Titlebaum, O.A., Glossary of Water Resource Terms, US Environmental Protection Agency (1970); Getches, D. H., Water Law, St. Paul, Minn,: West Publishing (1984); and American Society of Civil Engineers, Glossary Water and Wastewater Control Engineering, 3^rd ed., New York: ASCE (1981)).

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