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DECLINING RATES OF EXPANSION OF RESERVOIR CAPACITY IN NORTH CAROLINA

David H. Moreau

Director, Water Resources Research Institute of the University of North Carolina

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ACKNOWLEDGEMENTS

The author wishes to thank Mr. James Leurnas for making available the computer files for dams in North Carolina. Mr. Leumas is Dam Safety Engineer, Division of Land Resources, North Carolina Department of Environment Health and Natural Resources. Without his cooperation this report would not have been possible.

Mr. John Morris, Director, North Carolina Division of Water Resources; Mr. Charles Gardner, Director, North Carolina Division of Land Resources; and Mr. Larry Saunders, Chief, Planning

Division, U.S. Army Corps of ~ngineers, Wilmington, NC, reviewed drafts of this report and offered many helpful suggestions and criticisms. The author is grateful for their help, but they are not responsible for the opinions and conclusions expressed in the report.

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Two complementary inventories of dams in North Carolina are used to examine trends in reservoir capacity from 1900 to 1990. Normal capacity of all reservoirs is shown to be expanding at a declining rate since 1970; construction of reservoirs used

primarily for hydroelectric power virtually ceased after 1965. Construction of reservoirs classified as being primarily for water supply or for recreation has also declined sharply since

1970. These trends are particularly important in the growing urban Piedmont region that depends almost exclusively on surface water supplies. They point to the need to protect existing

reservoirs, identify and preserve sites for new reservoirs, and to reexamine statutes and administrative processes for allocating stored water among competing uses.

FINDINGS AND RECOKMENDATIONS .

Analyses of records of reservoir development in North

Carolina, as described in this report, lead to several findings. First, expansion of normal capacity in reservoirs, including

storage for hydroelectric power, public water supply, recreation, and other conservation purposes has slowed considerably since the 1960s. Nearly 85 percent of the 7.04 million acre-feet of normal capacity that existed in 1990 was built during the period 1915-

Second, one of the major reasons for that slow-down is the fact that expansion of capacity for hydroelectric power virtually ceased after 1965. This factor is particularly important because over 70 percent of normal capacity in 1990 was in reservoirs that were built primarily for generating hydroelectric power.

Third, expansion of capacities of reservoirs intended primarily for public water supplies has been rather flat since the early 1970s. Since 1970, significant increases in capacity for public water supply have been included in reservoirs that were built primarily for flood control. Most of this increase was due to two projects in the Research Triangle area.

Fourth, increases in reservoirs used primarily since the early 1970s.

both the number and capacities of

for recreation have dramatically slowed

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Finally, few additional major reservoir sites have been identified and very few are in active stages of planning.

Therefore, rates of expansion are likely to continue to decline over coming years.

Demand for water and water-based services is growing much faster than the rate at which supplies have been developed over the past 15 to 20 years. The gap between demand and supply can be attributed to a number of factors. First, the best sites for building dams have already been developed. Yet-to-be-developed sites are likely to be less cost-effective even if they were built to the same standards as those in earlier years, but new projects are likely to be built under more stringent safety criteria. Furthermore, because of changing social values, environmental costs of new projects are likely to be

substantially greater than those associated with earlier

projects. New projects will have to stand more rigorous tests of public need than those built by earlier generations.

These findings lead to several recommendations. One, greater care must be taken to protect existing reservoirs, including efforts to preserve both the quantity of storage and the quality of impounded water. Two, greater attention must be given to the identification and preservation of sites for new reservoirs. Three, as demands continue to grow faster than supply and excess capacity is depleted, new needs will be increasingly met through reallocation of storage in existing reservoirs, and the current system for allocating that storage among competing uses should be reexamined. If economic

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TABLE OF CONTENTS

ABSTRACT

. . .

iii

. . .

FINDING8 AND RECOMMENDATIONS iii

. . .

LIST OF FIGURES vi

. . .

LIST OF TABLES vi

PURPOSE

. . .

1

. . .

THE EXISTING INVENTORY 1

. . .

Size Distribution 4

. . .

Capacities 5

. . .

E X P A N S I O N O V E R T I M E 6

. . .

AllReservoirs 6

. . .

Hydroelectric Power 9

Recreation

. . .

10

. . .

W a t e r s u p p l y 10

. . .

Planned Reservoirs 13

. . .

CAUSES OF THE SLOW-DOWN 14

. . .

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LIST OF FIGURES

Figure 1.

Figure 2.

Figure 3.

Figure 4 .

Figure 5.

Figure 6.

Figure 7.

Figure 8.

Figure 9.

Components of Reservoir Capacity

. . .

3

Normal Capacity of Reservoirs in North Carolina 1900-

1990

. . .

Difference between Maximum and Normal Capacity 1900-

. . .

1990 . 7

Number of Reservoirs Having at Least 100 Acre-feet of

. . .

Storage 1900-1990 8

Normal Storage in Hydroelectric Power Reservoirs 10

Normal Storage in Single Purpose Recreation Lakes 11

Normal Storage in Water Supply Reservoirs

. . .

12

Reservoir Capacity per Capita in North Carolina

.

.

18

Urban Population in North Carolina 1900-1990

. . .

19

Figure 10. Distribution of Urban Population in North Carolina 21

LIST OF TABLE8

Table 1. Size Distribution of Reservoirs in North Carolina

. .

4

Table 2. Capacities of Reservoirs by Purpose

.

.

.

5

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PURPOSE

Demands for water-based services supplied by surface water impoundments in North ~arolina are increasing at a rapid pace as population, income, and other factors affecting demand continue to grow. A large share of these demands is for impounded surface water for public water supplies, recreation, flood control,

hydroelectric and thermoelectric power, water quality management, and other purposes. Expansion of reservoir capacity is

proceeding at a much slower pace than demand, however. In fact, the rate of expansion has slowed considerably in recent years. The widening gap between growth of demand and expansion of

supplies is examined in this paper. Causes of the slow-down in reservoir expansion are examined, and some implications of this trend are explored.

THE EXISTING INVENTORY

An inventory of existing reservoirs is available from two sources. One is the register of dams in North Carolina prepared by the Division of Land Resources (DLR), Department of

Environment, Health, and Natural Resources. That agency is

charged with the responsibility for dam safety in the state. The computer file of dams that is maintained by DLR contains data on 4,727 regulated dams and related lakes (as of July, 1992). Most of these dams are at least 15 feet high (toe to top) and contain at least 10 acre-feet (ac-ft) of volume.'

The second dataset is one that is maintained by the U.S.

Geological Survey (1990). It includes selected characteristics of all large reservoirs in the United States that have at least 5,000 acre-feet of normal capacity and 25,000 acre-feet of

maximum capacity. This data set is particularly useful for the larger reservoirs because some of the federally-owned reservoirs

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are exempt from state regulations and are not included in the state data.

Some limitations on analysis result from the nature of these datasets. First, information is not available for many of the reservoirs in the DLR database. More than three-fourths of the entries in that file are for relatively small lakes for which only limited information is available. A large fraction of them fall in the category of farm ponds. Volumes are not available for 1,186 of the reservoirs in the file, but most of those are probably very small reservoirs, and, as noted later, most of the statewide storage is in a relatively small number of impoundments for which volumes are available. Furthermore, no date of

completion is available for 3,011 dams, but fortunately, these are mostly small impoundments whose total volume is less than 1

percent of total reported capacity.

Second, there is no reporting of how storage has been

allocated in multiple purpose reservoirs. Some reservoirs are built to serve a single purpose such as public water supply, recreation, or cooling of thermoelectric power plants. Most large, single-purpose reservoirs that are designed primarily for public water supply or for cooling water are also used for

recreation, but recreational use of these lakes is incidental to their primary purpose. Other reservoirs, such as those built by the U.S. Army Corps of Engineers and large electric power

companies, are designed to be used for multiple purposes, often including flood control, public water supply, recreation, and hydroelectric power.

Even if they are not designed for flood control, most

reservoirs include some storage above the elevation at which they are normally operated. That storage, generally known as

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called controlled storage. In either case, there is usually a difference between the maximum capacity (volume) of a reservoir and the capacity under normal (non-flood) operating conditions.

The normal capacity usually consists of two parts as

illustrated in Figure 1. It contains the conservation storage, the active or useable part of normal capacity, and inactive storage from which no releases or withdrawals can be made. Conservation storage may also be allocated among two or more purposes. For instance, conservation storage in each of Falls Lake on the Neuse River and Jordan Lake on the Haw River was allocated in the congressional authorization process between public water supply and downstream.flow augmentation. In some reservoirs, conservation storage may be allocated implicitly in establishing the rules by which a reservoir is to be operated.

Maximum

Normal

.L . ( "

Figure 1. Components of Reservoir capacity

The DLR and USGS datasets include the purpose(s) for which each reservoir is used. For multiple purpose reservoirs, the order of priority of uses is reported, but the allocation of capacity is not. In this analysis, where reservoirs are

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Caution must be exercised,therefore, when drawing conclusions from this analysis.

A third limiting factor in these datasets is that they

exclude certain interstate reservoirs like John H. Kerr Reservoir located on the Virginia border and Lake Wylie on the South

Carolina border. Those reservoirs could be easily added to the dataset, but their inclusion would simply reinforce the

conclusions to be drawn from this analysis.

Siee Distribution

Data given in Table 1 confirm that a very large proportion of reservoirs in the DLR-USGS database are small reservoirs. Thirty-seven percent of the 3,554 dams for which storage volumes are available have maximum capacities of 25 acre-feet (8.1 MG) or less. Three-fourths of them are smaller than 100 acre-feet.

Only 158 reservoirs (4.1 percent) have maximum volumes in excess of 1,000 acre-feet (326 MG)

.

Table 1. Size Distribution of Reservoirs in North Carolina

Size Ranqe (ac-ft) Number

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Despite the preponderance of small reservoirs in the

inventory, however, most of the statewide storage is contained in the larger reservoirs. There are 866 reservoirs in the combined files that have a maximum capacity at least 100 acre-feet. Those projects account for over 99 percent of storage in all of the 4,740 reservoirs in the combined dataset. For purposes of this analysis, it is fortunate data are available on storage volumes and completion dates for all but a very few of these projects over 100 acre-feet.

Capacities

The numbers of reservoirs by purpose are shown in Table 2. Storage capacities in those reservoirs for which storage volumes are available are also included in Table 2. Although several of the larger reservoirs in the database serve more than one

purpose, all reservoirs have been classified by the primary purpose for which they were built as indicated in the file from

DLR. Data in that file do not indicate how storage in multiple purpose reservoirs is allocated among purposes. The table

includes both the maximum capacities of reservoirs (when they are brim-full under flood conditions) and normal capacities. The largest difference between maximum capacity and normal capacity is found in reservoirs that were designed primarily for flood control. In those projects, a large share of the storage is empty except under flood conditions. They account for 20.4

percent of all maximum-capacity storage, but only 13.4 percent of normal capacity. The largest shares of both maximum-capacity and

Table 2. Capacities of Reservoirs by Purpose

Purpose

Capacities in Acre-Feet of Storaae Number Maximum Capacitv Normal Capacity

Hydroelectric

Power 55 6,307,432 5,016,300 Flood Control 84 1,999,505 942,569 Public Water

supply 183 440,591 305,759

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normal-capacity storage are in projects that were built primarily for hydroelectric power. That set of projects accounts for 64.2 percent of all maximum-capacity storage and 76.7 percent of

normal-capacity storage.

EXPANSION OVER TIKE All Reservoirs

As illustrated in Figure 2, the rate of increase in normal reservoir capacity in North Carolina has slowed down considerably

Figure 2. Normal Capacity of Reservoirs in North Carolina 1900-

1990

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was approximately 0.2 MAF per year. Growth has been much slower since then. Over the 35-year period 1930-1965 an additional 2.7 MAF of normal storage was added to the inventory. The average annual rate of addition during this period was about 0.08 MAF.

That rate continued to drop from 1965 to 1990 when capacity increased by only 1.02 MAF, an average annual rate of 0.07 MAF.

Figure 3. Difference between ~aximum and Normal Capacity 1900

-

1990

While growth in normal storage has tended to slow down,

storage allocated to flood management has continued to rise since about 1918. Figure 3 shows how the difference between

maximum

and normal storage has increased over time. Some of that

difference is due to the inclusion of flood control in reservoirs that were built primarily for hydroelectric power; some is

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during extreme storms; and, since the 1950s, several major flood control projects have been constructed by the U . S . A m y Corps of Engineers. The jump in flood control capacity from 1980 to 1985 is almost solely due to two reservoirs, namely B. Everett Jordan Lake on the Haw and New Hope Rivers near Pittsboro and Falls Lake near Raleigh. These two projects added 1.18 MAF of maximum-

capacity storage, much of which was dedicated t o flood control. A slow-down in reservoir construction is evident from the

Figure 4. Number of Reservoirs Having at Least 100 Acre- Feet of Storage 1900-1990

numbers of reservoirs as well as their normal capacities. As shown in Figure 4, the rate of increase in the numbers of reservoirs began to decline in the period 1965-70, and that

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866 reservoirs over 100 acre-feet and the 474 recreational reservoirs in that size range.

Hydroelectric P o w e r

A major factor contributing to the post-1965 slow-down has been the virtual exhaustion of sites for development of

-

hydroelectric power. As noted earlier in this report,

hvdroelectric power projects account for 6.31 MAF of current maximum-capacity storage, nearly 60 percent of the storage for

4

all projects.

-

They account for 5.02 MAF of normal-capacity

storage, 74 percent of that for all purposes. A s illustrated

in

Figure 5, 87 percent of that capacity was built prior to 1965

--

Figure 5. Normal Storage in Hydroelectric Power ~eservoirs

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60 percent before 1945. Among the pre-1945 projects are several large Duke Power reservoirs on the Catawba River, including Lake James-Bridgewater (0.265 MAF), Lake James-Paddy's Creek (0.265 MAF), Lake Hickory (0.366 MAF), Mountain Island (0.140 MAF), and Lake Rhodhiss (0.114 MAF). Several major projects were also built on the Yadkin River by private companies before 1945, including Narrows (0.456 MAF), Norwood (0.177 MAF), and Blewett Falls (0.100 MAF). Five major projects in the Tennessee River Basin were constructed before 1945 with a combined capacity of 1.68 MAF, including Santeetlah, Chatuge, Hiawassee, Nantahala, and Fontana. Only two large hydroelectric projects have been built since 1945, Lake Norman (1.09 MAF) and Tuckertown (0.425 MAF), and both of those were built before 1965.

Recreation

There has also been a dramatic reduction in the rate at which recreational reservoirs are expanding. These reservoirs account for a rather modest share of total capacity, in the range of 4 to 5 percent, but 2,181 dams in the state inventory (46

percent) are classified for this purpose. As shown in Figure 6, the capacity of these reservoirs were growing exponentially until about 1975. That growth was curtailed abruptly. From 1945

through 1975, the capacity of recreational lakes increased at an average rate of 3.70 percent a year, but over the period 1975- 1990 that growth dropped sharply to an annual rate of 0.23 percent.

Water Supply

Construction of reservoirs for which the primary purpose is public water supply has also declined sharply since 1975. The state inventory includes 184 projects in this category with a combined maximum-capacity storage of about 440 thousand acre-feet

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the state began t o expand rapidly after 1950, there was a rapid expansion of capacity in water supply reservoirs t o meet the growing demand. From 1950 to 1975 capacity expanded at an average annual rate of 5.30 percent. Between 1975 and 1990, however, the average rate dropped to 0.55 percent a year.

Special note should be made in this case, however, that. expansion of capacity for water supply purposes was significant in two multiple purpose reservoirs that are not classified as being primarily for water supply. Both Falls and Jordan Lakes are assigned t o the flood control category because that is the highest priority designation in the dataset, but these two reservoirs contain 81 KAF of water supply storage. As noted earlier, a limitation of the dataset is that a complete breakout

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Planned Reservoirs

In addition to those trends revealed by the preceding

analyses of the history of reservoir expansion in North ~arolina, another significant indicator is the small number of future

projects that are in active planning processes. At present the

U.S. Army Corps of Engineers is not planning any new reservoirs. In comprehensive plans developed for the Neuse and Cape Fear River basins in the 1960s, Falls and Jordan Lakes were viewed by the Corps as the key development projects for those two basins, respectively (U.S. Army Corps of Engineers, 1961 and 1963). They had been included in plans prepared as early as 1933, but they were not authorized by Congress until the 1960s. After those two projects were completed in the 1980s, the Corps had exhausted the list of projects authorized for construction.

One other large multiple purpose project, Randleman Dam, was scrapped by the Corps because it failed to meet criteria for

federal participation. A modified plan for that project has been developed by the Piedmont Triad Regional Water Authority (PTRWA), and approval for its construction has been granted by the North Carolina Environmental Management Commission. If constructed as planned, it would add 56 KAF of water supply storage (NCDEHNR,

1991).

The Soil Conservation Service (SCS) is constructing or planning to construct three projects within the next five years under authority of Public Law 566, the small watershed program. One is a single-purpose flood control project in Rutherford County; another, on Town Fork Creek in Stokes County, is a dual purpose project for flood control and public water supply. The third is under construction in Duplin County. Preliminary

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CAUSES OF THE 8LOW-DOWN

Several factors have contributed to the slow-down in reservoir construction in North Carolina

--

exhaustion of

available sites for development, shifts in public attitudes and related legislative actions elevating the importance of

environmental values in water resource development decisions, dam safety legislation, and increased cost.

Expansion of reservoir capacity for hydroelectric power has slowed in large part due to a decline in attractive sites for development. The last major hydroelectric power projects were built in the early 1960s, before environmental regulations were enacted. There was a considerable slow-down in hydroelectric power construction after 1945, and two of the last big projects, Lake Norman (a large portion of which was dedicated to cooling water for thermoelectric power plants) and Tuckertown, accounted

for most of the added storage since 1945. Few other projects have even been proposed. One of the few remaining sites, one proposed for development by Appalachian Power Company on the New River in the late 1960s, ran into a storm of environmental

opposition and was never built.

Trends in North Carolina are consistent with those found at the national level. After nearly a century of reservoir

construction, most of the good sites have already been developed. In one of his commentaries on the Water Resources Planning Act, Professor Henry Caulfield, the first Director of the U.S. Water Resources Council, argues that the act was based on certain assumptions, many of which turned out to be false (Caulfield, 1984). Among those was an assumption by the Senate Select

Committee on National Water Problems in 1961 that a new round of comprehensive, multiple-purpose, river basin plans would identify the need for many more water projects. That need did not

materialize when those plans were developed.

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but lags somewhat behind that for North Carolina. Those numbers show the peak decades for expansion of reservoir capacity in the United States to be the 1950s and the 1960s. Rates of expansion during the 1970s were one-third of those in the 1960s. U.S.G.S.

states that

...

an upper limit on reservoir capacity for the 48

coterminous States is about 1,200 million acre-feet, of

which 450 million acre-feet has already been developed. The remaining or potential 750 million acre-feet is likely to be high in cost, because the more cost-effective sites have already been developed. If so, the Nation's reservoir

capacity may be gradually approaching a limit lower than the one suggested above.

Shifts in public attitudes about building dams, often undergirded by various legislative acts, apparently have had a significant effect on reservoir construction. Among the

legislative actions that has made dam building more difficult are :

(1) North Carolina's Dam Safety Act of 1967,

(2) the Wild and Scenic Rivers Act,

(3) the National Environmental Policy Act of 1969 (NEPA) t

(4) the Federal Water Pollution Control Act (FWPCA) Amendments of 1972,

(5) the Water Resources Development Act of 1986,

(6) and North Carolina's Sedimentation and Erosion Control Act of 1973.

The Dam Safety Act was passed in 1967, but only modest

resources were made available by state government until events of 1976 and 1977 ( Charles Gardner, Director, Division of Land

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County and threats to many others. Increased public awareness stemming from these events led to increased appropriations for enforcement of dam safety. Dam safety regulations may not deter construction of large reservoirs, but data in Figures 3 and 5

suggest that regulatory actions of one kind or another have had a substantial effect on smaller reservoirs. Regulations requiring adequate emergency spillway capacity added to the cost of

construction and may have caused developers to either drop plans for some reservoirs or reduce them to a size such that they were no longer covered by the regulations.

NEPA, combined with Section 4 0 4 of the amendments to FWPCA,

triggered the use of environmental impacts statements on water projects. Regulations promulgated by the U.S. Army Corps of ~ngineers in 1975 under authority of Section 4 0 4 required that anyone building a reservoir that impounded water from more than 5

square miles of a watershed to obtain a permit before dredging or filling in a stream. Granting of that permit, judged to be a "major federal action", triggered provisions of NEPA that required an environmental assessment before a permit could be granted. In some cases, environmental considerations may have been were sufficient to discourage applications for 4 0 4 permits. Costs of actions necessary to mitigate adverse environmental effects to the satisfaction of federal agencies may have tipped the scales in some instances to a point that proposed projects were no longer financially viable.

Shifts in public attitudes were clearly evident in decisions to abort plans for dams on the New River and Eno Rivers. The campaign to save the New River from Appalachian Power's proposed hydroelectric dam was based on a desire to preserve the natural and scenic beauty of that river. A plan to build a water supply reservoir on the Eno River was similarly aborted years ago

because of public demands to preserve the area in an undeveloped state (John N. Morris, Director, N.C. Division of Water

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keeping the Eno undeveloped were successful subsequently in getting the area incorporated into a state park.

The argument that the most cost-effective sites have already been developed is supported by the work of Memel (1958) that

shows the declining marginal productivity of new reservoir sites. In that approach, the indicator of cost-effectiveness is the

volume of storage created in a reservoir per unit volume of

material required to build the dam. Dams built in the 1920s and earlier contained, on average, 10.4 acre-feet of storage for every cubic yard of material placed in the dam (about 17,000

cubic feet of storage per cubic foot of material). Dams built in the 1960s contained only 0.3 acre-feet of storage per cubic yard of material (470 cubic feet per cubic foot). In other words, it took 36 times more material to develop new reservoirs at sites that were available in the 1960s than it did to create

reservoirs of the same size at sites that were available in the 1920s.

DEMAND

The slow-down in expansion of reservoir capacity runs counter to the trend for water and water-related services in North Carolina. Rates of growth of demand are well above those for supplies. A general indicator of need relative to supply is the ratio of normal reservoir capacity to population, and

variations in that ratio since 1900 are shown in Figure 8. The big jump in per capita capacity came during the decade 1910 to 1920 when it jumped to about 0.75 acre-feet per resident. It continued to rise at an unsteady rate from 1920 until 1970, but it has declined since 1970.

That trend has been dominated by hydroelectric power

reservoirs, however, and the virtual stoppage of new capacity for that purpose after 1965 tends to mask changes for other purposes. Of special concern is the growth in reservoirs for public water supplies

.

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An indirect but very useful indicator of public water use is urban population. More than 90 percent of urban residents in North Carolina are served by public supplies, and most of the water produced by public supplies is used within urban areas. A s

shown in Figure 9, the number of people living in towns and cities in ~orth'carolina has grown rapidly and steadily

Figure 9. Urban Population in North Carolina 1900-1990

throughout the twentieth century. In 1900, less than 200,000 people resided in urban areas in the state, but in the first 4 0

years of this century, that number increased by 800,000. It took only 20 years for the n e x t 800,000, and over the period 1960 to 1990, the urban population

in

North Carolina increased by 1.5

million, bringing the 1990 count for million. Thus, in the past 50 years

urban residents to 3.3

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quadrupled, and it is reasonable to assume that water use has increased by at least that much.

As shown in Figure 10, much of that population has been

concentrated in the Piedmont region of the state where the public water supplies are drawn predominantly from surface waters. The

1989 data compiled by DEHNR and reported by USGS indicate that 88

percent of all public supplies in the state is taken from surface sources. In the Piedmont region where groundwater can be

withdrawn only at relatively small rates, all water systems that serve over 10,000 people take their water from rivers and

reservoirs.

USGS reported that in 1989 water was withdrawn from surface and groundwater sources in North ~arolina at the rate of 805

million gallons per day (MGD), a 41 percent increase over the estimated withdrawal of 570 MGD in 1980. As stated earlier, the historical data are subject to considerably more uncertainty than the 1989 data, but, if valid, the USGS data indicate that public water use has increased by nearly 80 percent just since 1970.

Not only has total use increased, but the USGS data imply that per capita consumption has increased also. Estimated use in 1980 is equivalent to an average use of 202 gallons per day per urban resident (that number includes commercial, industrial, and public use as well as residential use). Similar calculations for 1989 indicate per capita use at 241 gallons per day, an increase of 19 percent.

The fact that demand for water is growing much faster than reservoir capacity has long-range implications for water

management but not necessarily in the short-term. Reservoir

capacity is only an indirect volumetric measure of supply (say in acre-feet or million gallons), and it cannot be compared directly with demand which is expressed as a rate of use (say million

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Carolina are enjoying the benefits of excess supply constructed before 1980 (John N. Morris, Director, North Carolina Division of Water Resources. Personal Communication. 1992). Falls and Jordan Lakes in the Research Triangle region and the Catawba Lakes in the Charlotte area created excess capacities upon which cities in those areas are now drawing. Two other urban areas where

shortages are being anticipated, namely the Piedmont Triad and Asheville, are vigorously pursuing development of new sources.

with the rapid increase in demand, however, excess supplies will be diminished. As that occurs, cities will be faced with one of several options. Like the Piedmont Triad and Asheville, they could seek to add new reservoirs, but as noted, that option is becoming increasingly difficult and costly. A second option will be to seek reallocation of existing storage from

hydroelectric power, recreation, and other uses to public water supply. Informal reallocations have been occurring at several locations, but formal reallocations are likely to be highly contested. A third option, one that has not been pursued with any vigor in North Carolina, is to seek improvements in the efficiency with which water is being used in urban areas. Only the first steps have been taken toward the use of conservation as a viable management option. An important step was taken with revisions to the state plumbing code to require all residences built after January 1, 1993 to have low-flush toilets (1.6 gallons per flush) and low-flow showerheads (3.0 gallons per minute). These restrictions apply only to new residences,

however, and many other opportunities for improving efficiency of existing uses in residential, industrial, commercial and

institutional sectors have not been pursued.

GUMMARY AND CONCLUSIONS

These observations about trends in surface water supplies and the need for water in North Carolina point to the

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development in North ~arolina suggest that the rate of expansion of normal reservoir capacity has definitely slowed down since the 1960s. When that evidence is combined with the knowledge that few additional major reservoir sites have been identified and very few are in active stages of planning, it is unlikely that current trends are likely to change. Expansion of capacity for hydroelectric power, which account for a major portion of

existing capacity, virtually ceased after 1965. Increases in both the number and capacities of reservoirs that are used primarily for recreational use have been dramatically slowed since the early 1970s. Likewise, expansion of capacities of reservoirs intended primarily for public water supplies has been rather flat since the early 1970s. Substantial increases in storage for public water supplies were included in two multiple purpose Corps of Engineersf projects in the Research Triangle area in the 1980s.

When indicators of demand are compared to supply, it becomes clear that demand has been growing much faster than supplies have been developed over the past 15 to 20 years. Furthermore, there is a limit on how much that supply can be expanded. The number of suitable reservoir sites is fixed, and as each new site is selected for development from among those that remain, both the quantity and cost-effectiveness of remaining sites are

diminished.

Yet-to-be-developed sites are likely to be less cost-

effective even if they were built to the same standards as those in earlier years, but new projects are likely to be built under more stringent safety criteria. Furthermore, because of changing social values, environmental costs of new projects are likely to be substantially greater than those associated with earlier

projects. As a consequence, new projects will have to stand more rigorous tests of public need than those built by earlier

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abundant resource, greater care must be taken to protect existing reservoirs. Greater attention must be given to reducing losses of storage in these reservoirs due to the deposition of sediment. Greater attention must be given to preserving the quality of

water in existing reservoirs to keep them fit for their highest and best uses. A second and similar implication is that greater attention must be given to the identification and preservation of sites for new reservoirs.

A third implication is that the current system for allocating storage in existing reservoirs to competing uses

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Caulfield, Henry P. 1984. "Fulfilling the Promises of the Water Resources Planning Act," paper presented at the 25th Annual Meeting of the Interstate Conference on Water Problems, Pittsburgh, PA, Sept. 18, 1984.

Langbein, Walter B. 1982. Dams. Reservoirs, and Withdrawals for Water Sutmlv

-

Historic Trends. U.S. Geological Survey Open- File Report 82-256.

Memel, T.W. 1958. Reqister of Dams

in

the United States. McGraw- Hill Book Co.

North Carolina Department of Environment, Health, and Natural Resources, Division of Water Resources. 1991. G.S. 162-7 &

153A-285 ~ e v i e w Document and Final Environmental I m ~ a c t Statement: Randleman Lake.

U.S. Army Corps of Engineers. 1961. Com~rehensive Report on Cape Fear River Basin, North Carolina, District Office,

Wilmington, N.C.

U.S. Army Corps of Engineers. 1963. Neuse River Basin, N.C.,

District Office, Wilmington, N.C.

U.S. Geological Survey. 1984. National Water Summarv 1983. U.S. Geological Survey Water-Supply Paper 2250, U.S. Government Printing Office, Washington, DC.

U.S. Geological Survey. 1990. Summarv of Selected Characteristics of Larse Reservoirs in the United States and Puerto Rico,

Figure

Figure 1. Components of Reservoir capacity
Figure 2. Normal Capacity of Reservoirs in North Carolina 1900- 1990
Figure 3. Difference between ~aximum and Normal Capacity 1990
Figure 4. Number of Reservoirs Having at Least 100 Acre- Feet of Storage 1900-1990
+4

References

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