Section 1
Description of the
South Central Texas Region

1.1       Background

Water supplies of the South Central Texas Region are obtained from the Edwards-Balcones Fault Zone, Carrizo-Wilcox, Trinity, and Gulf Coast Aquifers; from two minor aquifers (Queen City and Sparta); and from the rivers, streams, and reservoirs within the region.  The water supply picture of the region is very complex, involving intricate relationships between surface water and groundwater.  The Edwards-Balcones Fault Zone Aquifer (hereinafter referred to as the Edwards Aquifer) supplied approximately 46 percent of the total water used in the South Central Texas Region in 1990.  Water demands for the area that is now being supplied from the Edwards Aquifer are growing at a rate of approximately 1.7 percent per year.  However, not even the present level of use can be sustained while maintaining levels of flows at Comal and San Marcos Springs adequate to support habitats of threatened and endangered species and also meet downstream water rights.  Demands on the other aquifers of the South Central Texas Region exceed recharge, such that continued withdrawals at present rates could ultimately result in water supply failures, particularly in some areas that now depend upon the Trinity, Carrizo-Wilcox (hereinafter referred to as the Carrizo Aquifer), and Gulf Coast Aquifers.

Operations of the largest existing surface water supply sources in the region are also directly linked to the Edwards Aquifer.  Dependable supplies from Canyon Reservoir for municipal and industrial customers are a function of springflows from the Edwards Aquifer, since releases from Canyon are necessary to meet downstream water rights when springflows drop below certain levels.  Storage in the Medina Lake System contributes significantly to recharge of the Edwards Aquifer, and reservoirs used for power generation (Coleto Creek, Calaveras, and Braunig) are dependent upon springflows and/or treated municipal effluent that originate from the Edwards Aquifer.  Surface water supplies available to the region are also a function of recharge to and withdrawal from the aquifers, as are the quantities of streamflows permitted for use in counties of the Nueces, San Antonio, and Guadalupe River Basins outside of the South Central Texas Region.  In water planning for the South Central Texas Region, these factors, together with the numerous potential water management strategies and options of the South Central Texas Region, will have to be taken into account.

1.2       Physical Description of the South Central Texas Region

The South Central Texas Region includes counties that are located in whole or in part in the Rio Grande, Nueces, San Antonio, Guadalupe, Colorado, and Lavaca River Basins, and the Colorado-Lavaca, Lavaca-Guadalupe, and San Antonio-Nueces Coastal Basins (Table 1-1).  The physical terrain of the region ranges from the Hill Country of the Edwards Plateau to the Coastal Plains.  A general description of the region, including geology, climate, water resources, vegetational areas, and major water demand centers, is presented in the following sections.

1.2.1    Climate[1]

The South Central Texas Region lies in three climatic divisions in Texas: the Edwards Plateau division, the South Central division, and the Upper Coast division.  The climate of the region is classified as humid subtropical.  Summers are usually hot and humid, while winters are often mild and dry.  The hot weather is rather persistent from late May through September, accompanied by prevailing southeasterly winds.  There is little change in the day-to-day summer weather, except for the occasional thunderstorm, which produces much of the annual precipitation within the region.  The cool season, beginning about the first of November and extending through March, is also typically the driest season of the year.  Winters are ordinarily short and mild, with most of the precipitation falling as drizzle or light rain.  Any accumulation of snow is a rare occurrence.  Polar air masses, which penetrate the region in winter, bring northerly winds and sharp drops in temperature for short periods of time.

In the coastal region, the climate is dominated by proximity to the Gulf of Mexico and characterized by prevailing southeasterly winds.  During the long humid summers, high daytime temperatures, which are common in inland areas, are moderated in coastal areas by the Gulf breeze.

Mean annual precipitation in the region ranges from a high of 38 inches per year in DeWitt County, in the eastern part of the region, to a low of 23 inches per year in the Nueces River Basin, in the west (Table 1-2).  There is a general trend of decreasing precipitation from the eastern portions of the region to western portions.  There is also a general trend of increasing precipitation from inland areas to coastal areas.

Although mean annual temperatures are basically uniform throughout the region, there are some marked seasonal variations, which lead to widely varied values for annual net lake surface evaporation.  The values for annual net lake surface evaporation range from a high of 65 inches per year, for the portion of Dimmit County located in the Rio Grande River Basin, to a low of 24 inches per year, for the portion of DeWitt County that lies in the Lavaca River Basin (Table 1-2).

The South Central Texas Region is subject to the threat of hurricanes each year from mid-June through the end of October, and in those parts of the region along and near the coastline, the hazard of hurricane tides is prevalent.  Although hurricane winds and tornadoes spawned by hurricanes cause extensive damage and occasional loss of life, surveys of hurricanes reaching the Texas Coast indicate that storm tides cause by far the greatest destruction and largest number of deaths.  Elsewhere in the inland areas of the region, the greatest concern with regard to hurricanes is the damage that results from winds and flooding.  Records dating back to 1871 show that, on average, a tropical storm or hurricane has affected the region once every 3 years.

1.2.2    General Geology[2]

The Hill Country area of the South Central Texas Region is underlain by Cretaceous Age limestone, which forms the Edwards Plateau.  East and south of the Plateau are upper Cretaceous chalk, limestone, dolomite, and clay, with the extensive Balcones Fault Zone System marking the boundary between the Edwards Plateau and the Gulf Coastal Region.  The entire sequence dips gently toward the southeast.

A Tertiary Age sequence of southeasterly dipping sand, silts, clay, glauconite, volcanic ash, and lignite overlie the Cretaceous Age strata.  The primary water-bearing unit of this sequence is the Carrizo Aquifer.  A sequence of clay, sand, caliche, and conglomerate of the Pliocene Age Goliad Formation underlie the coastal areas of the region.

Overlying the Goliad Formation is the Quaternary Age Lissie Formation, which consists of sand, silt, clay and minor amounts of gravel.  Clay, silt, and fine-grained sand of the Beaumont Formation overlie the Lissie Formation.  Throughout the region, alluvial sediments of Recent Age occur along streams and coastal areas.

1.2.3    Vegetational Areas[3]

Biologically, the South Central Texas Regional Planning Area is a region of transition from the lowland forests of the southeastern United States to the arid grasslands of the western uplands and tropical thorn scrub to the south.  The essence of this landscape consists of dendritic networks of wooded stream corridors populated by typically eastern species that dissect upland grasslands, and savannahs that harbor western species.  The vegetational areas containing portions of the South Central Texas Regional Planning Area are the Edwards Plateau, South Texas Plains, Blackland Prairies, Gulf Prairies and Marshes, and the Post Oak Savannah (Figure 1-1).  Each area is described below.

1.2.3.1     Edwards Plateau

In the South Central Texas Region, the Edwards Plateau vegetational area includes all of Kendall County, the northern portions of Uvalde, Medina, Bexar, and Comal Counties, and that portion of Hays County located within the planning area.  This limestone-based area is
characterized by springfed, perennially flowing streams that originate in its interior and flow across the Balcones Escarpment, which bounds it on the south and east.  This area is also characterized by the occurrence of numerous ephemeral streams that are important conduits of storm runoff, which contributes to the recharge of the Edwards Aquifer.  The soils are shallow, ranging from sands to clays, and are calcareous in reaction.  This area is predominantly rangeland, with cultivation confined to the deeper soils.

Noteworthy is the growth of Bald cypress (Taxodium distichum) along the perennially flowing streams.  Separated by many miles from cypress growth of the moist Southern Forest Belt, they constitute one of Texas’ several “islands” of vegetation

The principal grasses of the clay soils are several species of bluestem (Schizachyrium and Andropogon spp.), gramas (Bouteloua spp.), Indiangrass (Sorghastrum nutans), common curlymesquite (Hiaria belangeri), buffalograss (Buchloe dactyloides), and Canadian wild rye (Elymus canadensis).

The rocky areas support tall or mid-grasses with an overstory of live oak (Quercus virginiana) and other oaks (Q. fusiformis, Q. buckleyi, Q. sinuata var. breviloba), cedar elm (Ulmus crassifolia) and mesquite (Prosopis glandulosa).  The heavy clay soils have a mixture of buffalograss (Buchloe dactyloides), sideoats grama (Bouteloua curtipendula), and mesquite (Prosopis glandulosa).

1.2.3.2     South Texas Plains

South of San Antonio, including all or parts of Uvalde, Zavala, Dimmit, Medina, Frio, LaSalle, Bexar, Atascosa, Wilson, Karnes, DeWitt, Goliad, and Refugio Counties, lies the South Texas Plains vegetational area, which is characterized by subtropical dryland vegetation consisting of small trees, shrubs, cactus, weeds and grasses.  Principal plants are honey mesquite (Prosopis glandulosa), live oak (Quercus virginiana), post oak, several members of the cactus family (Cactaceae), blackbrush acacia (Acacia rigidula), guajillo (Acacia berlandieri), huisache (Acacia smallii) and others that often grow very densely.  The original vegetation was mainly perennial warm-season bunchgrass in post oak, live oak, and mesquite savannahs.  Other brush species form dense thickets on the ridges and along streams.  Long-continued grazing as well as the control of wild fires has contributed to the dense cover of brush.  Most of the desirable grasses have persisted under the protection of brush and cacti.

There are distinct differences in the original plant communities on various soils.  Dominant grasses on the sandy loam soils are seacoast bluestem (Schizachyrium scoparium var. litoralis), bristlegrasses (Setaria spp.), and silver bluestem (Bothriochloa saccharoides).  Dominant grasses on the clay and clay loams are silver bluestem, Arizona cottontop (Trichachne californica), buffalograss (Buchloe dactyloides), common curlymesquite (Hilaria belangeri), bristlegrasses (Setaria spp.), gramas (Bouteloua spp.), and Texas wintergrass (Stipa leucotricha).  Gulf cordgrass (Spartina spp.) and seashore saltgrass (Distichlis spicata) characterize low saline areas.  In the post oak and live oak savannahs, the grasses are mainly seacoast bluestem (S. scoparium var. litoralis), Indiangrass (Sorghastrum nutans), and switchgrass (Panicum virgatum).

1.2.3.3     Blackland Prairies

This area, including parts of Bexar, Comal, Guadalupe, Hays, Caldwell, Gonzales, and DeWitt Counties, while called a “prairie,” has timber along the streams, including a variety of oaks (Quercus spp.), pecan (Carya illinoiensis), cedar elm (Ulmus crassifolia) and mesquite (Prosopis glandulosa).  In its native state it was largely a grassy plain.

Most of this fertile area has been cultivated, and only small acreages of meadowland remain in original vegetation.  In heavily grazed pastures, buffalograss (Buchloe dactyloides), Texas grama (Bouteloua rigidiseta) and other less productive grasses have replaced the tall bunchgrass.  Mesquite and other woody plants have invaded the grasslands.

The original grass vegetation included big bluestem (Andropogon gerardi) and little bluestem (Schizachyrium scoparium), Indiangrass (Sorghastrum nutans), switchgrass (Panicum virgatum), sideoats grama (Bouteloua curtipendula), hairy grama (Bouteloua hirsuta), tall dropseed (Sporobolus asper), Texas wintergrass (Stipa leucotricha) and buffalograss.  Non-grass vegetation is largely legumes and composites.

1.2.3.4     Gulf Prairies and Marshes

The Gulf Prairies and Marshes vegetational area includes all or parts of Victoria, DeWitt, Goliad, Refugio, and Calhoun Counties.  There are two subunits: (1) the marsh and salt grasses immediately at tidewater and (2) a little farther inland, a strip of bluestems and tall grasses, with some gramas in the western part.  Many of these grasses make excellent grazing.  Oaks (Quercus spp.), elm, and other hardwoods grow to some extent, especially along streams, and the area has some post oak and brushy extensions along its borders.  Much of the Gulf Prairies is fertile farmland.

Principal grasses of the Gulf Prairies are tall bunchgrasses, including big bluestem (Andropogon gerardi), little bluestem (Schizachyrium scoparium), seacoast bluestem (S. scoparium var. litoralis), Indiangrass (Sorghastrum nutans), eastern gamagrass (Tripsacum dactyloides), Texas wintergrass (Stipa leucotricha), switchgrass (Panicum virgatum) and gulf cordgrass (Spartina spp.).  Seashore saltgrass (Distichlis spicata) occurs on most saline sites.  Heavy grazing has changed the range vegetation in many cases so that the predominant grasses are less desirable broomsedge (Andropogon virginicus), smutgrass (Sporobolus indicus), threeawns (Aristida spp.) and many other inferior grasses.  The other plants that have invaded the productive grasslands include oak underbrush, huisache (Acacia smallii), mesquite (Prosopis glandulosa), pricklypear (Opuntia spp.), ragweed (Ambrosia psilostachya), broomweed (Xanthocephalum spp.), and others.

1.2.3.5     Post Oak Savannah

This secondary forest region, also called the Post Oak Belt, includes all or parts of Guadalupe, Caldwell, Wilson, and Gonzales Counties.  It is immediately west of the primary forest region, with less annual rainfall and a little higher elevation.  Principal trees are post oak (Quercus stellata), blackjack oak (Quercus marilandica) and cedar elm (Ulmus crassifolia).  Pecans (Carya illinoiensis), walnuts (Juglans spp.) and other kinds of water-demanding trees grow along streams.  The southwestern extension of this belt is often poorly defined, with large areas of prairie.

The original vegetation consisted mainly of little bluestem (Schizachyrium scoparium), big bluestem (Andropogon gerardi), Indiangrass (Sorghastrum nutans), switchgrass (Panicum virgatum), silver bluestem (Bothriochloa saccharoides), Texas wintergrass (Stipa leucotricha), post oak and blackjack oak.  The area is still largely native or improved grasslands, with farms located throughout.  Intensive grazing has contributed to dense stands of a woody understory of yaupon (Ilex vomitoria) and oak brush and mesquite has become a serious problem.  In addition, the control of wild fires has affected the encroachment of brush species on Savannah range lands.  Such plants as broomsedge (Andropogon virginicus), broomweed (Xanthocephalum spp.) and ragweed (Ambrosia psilostachya) have replaced good forage plants.

1.2.4    Natural Resources

1.2.4.1     Water Resources

The South Central Texas Region includes parts of six major river basins (Rio Grande, Nueces, San Antonio, Guadalupe, Lavaca, and Lower Colorado) and overlies the Edwards and Gulf Coast Aquifers, and southern parts of the Trinity, Carrizo, and Edwards-Trinity (Plateau) Aquifers.  In addition to these water resources, the area also overlies two minor aquifers (Queen City and Sparta Aquifers).  Details about these water resources are presented in Section 1.7.

Springs also serve as a significant water resource in the South Central Texas Region.  The two most noteworthy springs are the Comal and San Marcos Springs, which both contribute to flow in the Guadalupe River.  The San Marcos Springs have the greatest flow dependability and environmental stability of any spring system in the southwestern United States.  Constancy of its

spring flow is apparently key to the unique ecosystem found in the uppermost San Marcos River.  Comal Springs, located in New Braunfels, serve as the source for the Comal River, which is a tributary of the Guadalupe River.  Unlike the San Marcos Springs, Comal Springs is more responsive to drought conditions and ceased flowing in June of 1956 in response to severe drought conditions.

1.2.4.2     Wildlife Resources

An overview of the environmental and cultural resources setting of Region L is presented in Volume I, Section 5.2.5, and more specific discussions of resources and impacts are presented in the previously completed Phase I work (Technical Evaluations of South Central Texas Region Water Supply Options, October 1999), and in Volume III of this series.  Common types of wildlife found in the area include white-tailed deer, raccoons, ringtails, gray foxes, coyotes, beaver, bobcats, and several species of skunks.  Wintering songbirds such as robins and cedar waxwings may also be found.

A key concern in the South Central Texas Region is that of threatened and endangered species.  There are approximately 123 species listed in the planning region by the U.S. Fish and Wildlife Service or the Texas Parks and Wildlife Department as threatened or endangered.  These species are listed by county in Appendix D (Volume III) with notations concerning concerning their habitat preferences and protected status, if any.

The subterranean aquatic habitats associated with the Edwards Aquifer support a diverse ecosystem.  Vertebrates and macroinvertebrates have been found at depths ranging from 190 to 2,000 feet in the artesian parts of the aquifer.  The Edwards Aquifer is the only important aquifer habitat in Texas in which vertebrate species live. Volume III, Appendix E includes a listing of threatened or endangered species found in the Edwards Aquifer and related springs.

1.2.4.3     Agricultural Resources

Of the 12.82 million acres of land area in the planning region, over 10.35 million acres (81 percent) are classified as farmland and ranchland (Table 1-3).  In 1997, there were 20,098 farms and ranches in the region with an average size of 866 acres (Table 1-3).  Of the 10.35 million acres of farmland, over 2.68 million acres were classified as cropland, of which about 1.15 million acres were harvested in 1997 (Table 1-3).  Approximately one-tenth (about 252,616 acres) of the total cropland in the region was irrigated in 1997 (Table 1-3).[4]  The leading irrigation counties are located in the western part of the region and include Uvalde, Frio, Medina, Atascosa, and Zavala.  Major irrigated crops are corn, cotton, grain sorghum, wheat, rice, soybeans, and vegetables.  Cow-calf operations are the most predominant type of livestock industry, although beef cattle, hogs and pigs, sheep and lambs, and poultry are also produced.  (Agricultural production and livestock production are discussed in greater detail in Sections 1.3.2 and 1.3.3, respectively.)

1.2.5    Major Water Demand Centers

In the South Central Texas Region there are four major water demand centers.  These centers are the Interstate Highway 35 (IH-35) corridor from San Antonio to San Marcos, the Edwards Aquifer region west of the City of San Antonio, the Winter Garden area south of the Edwards Aquifer area, and the Coastal area.  The San Antonio, New Braunfels, and San Marcos corridor along IH-35 is one of the fastest growing areas in Texas.  In the next 50 years, its water use will follow the same trend as population growth, with most of the demand being for municipal use.

The Edwards Aquifer region west of San Antonio, including Uvalde and Medina Counties, is a major demand center for water to be used for irrigated agriculture.  The Winter Garden area, including Zavala, Dimmit, and Atascosa Counties, is also a major demand center for water for irrigated agriculture.  The Coastal area, including the cities of Victoria and Port Lavaca, are major demand centers for water for industrial purposes, with significant demand for irrigation in Calhoun County.

1.3       Population and Demography

1.3.1    Historical and Recent Trends in Population

The South Central Texas Region population has increased from 806,770 in 1950 to approximately 1,954,100 in 1998, an increase of 1,147,300, or 2.4 times (Table 1-4).  The largest percentage increase occurred between the years 1950 and 1960 (25.8 percent), while the smallest occurred between 1990 and 1998 (15.2 percent) (Table 1-4).  Between the period 1950 to 1998, 16 counties had a positive annual growth rate, while five counties (DeWitt, Gonzales, Karnes, LaSalle, and Refugio) had a negative annual growth rate (Table 1-4).  Historically, the fastest growing counties in the region are Hays (3.34 percent), Comal (3.15 percent), Kendall (2.83 percent), and Guadalupe (2.31 percent), while the slowest growing counties were Dimmit (0.04 percent), Zavala (0.10 percent), Goliad (0.12 percent), and Frio (0.87 percent) (Table 1-4).  Section 2.1 summarizes population projections through the year 2050 for the South Central Texas Region.

There are 81 cities in the South Central Texas Region for which the TWDB has made population and water demand projections.  Of the 81cities, 22 have a population greater than 5,000.  These cities are relatively equally distributed among the 21 counties in the planning region and are located in three commonly used regional references (Coastal, Hill Country, and Winter Garden) (Table 1-5).  Bexar County contains six cities having a population of 5,000 or more, including San Antonio and its surrounding suburbs.  Four counties, Goliad, Karnes, Kendall, and Refugio, do not have a city of 5,000 or greater.

1.3.2    Demographic Characteristics

In 1990, 82 percent of the South Central Texas Region’s population resided in urban areas, while only 18 percent resided in rural areas (Figure 1-2).  LaSalle County had the lowest population in 1998, with 6,120 residents (averaging 4.1 persons per square mile), while Bexar County had the highest population in the region with 1,342,934 residents (averaging 1,077 persons per square mile) (Table 1-6).

Age distribution across the region is characterized by a relatively young population.  The two age groups that include the highest percentage of the population are under 18 years of age (29 percent) and from 25 to 39 years of age (25 percent) (Figure 1-3).  The age groups with the lowest percentage of the population are ages 18 to 24 (11 percent) and ages 65 and older (11 percent) (Figure 1-3).

The regional population can also be characterized by its level of education.  Of those residents in the South Central Texas Region who are 25 years of age are older, 60.7 percent have at least a high school diploma, while 39.3 percent do not.  The two largest groups rated according to educational achievement are those who have an 8th grade education or lower (24.7 percent) and those who have completed high school, but have not gone to college (27.3 percent).  Only 4 percent of the population who are 25 years or older have a graduate degree (Figure 1-4).

1.4       Economy — Major Sectors and Industries

1.4.1    Summary of the South Central Texas Regional Economy[5]

The South Central Texas Region has an economic base centered on agricultural production, livestock production, mining, manufacturing, and trades and services.  The region has experienced economic ups and downs throughout the past decade, but all sectors of the economy, with the exception of the mining sector, have experienced solid growth in recent years.  Paralleling economic growth, employment in the diversified regional economy is supported by a strong trades and services sector, which accounts for approximately 76 percent of the region’s value of output and a thriving tourism industry in San Antonio.  Fabricated metal products, industrial machinery, petrochemicals, and food processing form the core of the region’s manufacturing sector, which accounts for approximately 21 percent of the value of output in the South Central Texas Region.  Beef cattle, corn, and grain sorghum are the dominant agricultural enterprises, although vegetables produced in the Winter Garden area add diversity to the region’s agricultural sector.  A more detailed summary of the agricultural, livestock, mining, manufacturing, and trades and services sectors is presented below.

1.4.2    Agricultural Production

It was estimated in 1997 that over 2.6 million acres in the South Central Texas Region were used in crop production.  Of this total, only 252,616 acres (9.4 percent) were irrigated while the remaining 90.6 percent of the total cropland was farmed using dryland techniques.  The leading irrigation counties are found primarily in the western part of the region and include Uvalde, Frio, Medina, Atascosa, and Zavala.

According to the 1997 Census of Agriculture, all crops grown in the South Central Texas Region had a market value of over $290 million in 1997.  The leading agricultural producing counties in the region, by market value of products, are Bexar, Frio, Uvalde, Medina, and Atascosa.  The major crops grown in the region include corn, grain sorghum, wheat, soybeans and cotton (Table 1-7).

Corn and grain sorghum have historically been the leading crops in the region.  In 1997, it was estimated that over 17 million bushels of corn were harvested in the South Central Texas Region, having a market value of $48.5 million.  The leading corn producing counties in the region are Uvalde, Medina, Victoria, and Calhoun (Table 1-7).

Grain sorghum also contributes significantly to the region’s agricultural sector.  In 1997, it was estimated that over 17 million bushels of grain sorghum were harvested in the region, having had a market value of $42.5 million.  The leading grain sorghum producing counties in the region are Medina, Refugio, Victoria, Guadalupe, Wilson, and Uvalde (Table 1-7).

Although wheat production is not as widespread as corn and grain sorghum production, it is still an important part of the region’s agricultural production with almost 3 million bushels of wheat harvested in 1997, which had a market value of close to $10 million.  The leading wheat producing counties in the region are Medina, Uvalde, and Guadalupe Counties (Table 1-7).

Because of favorable climatic and soil conditions, the coastal counties of Calhoun and Victoria are able to produce rice.  In 1997, these two counties combined produced 305,683 hundredweight (cwt) of rice which had a market value of over $2 million (Table 1-7).

Cotton production is widespread throughout the region and is the third highest valued crop produced in the region.  In 1997, the 17 counties in which cotton is produced combined to harvest over 80,000 bales with a market value of over $24 million (Table 1-7).

The majority of soybean production in the region occurs in the area extending from the Gulf Coast to DeWitt and Karnes Counties.  The two leading soybean producing counties are Calhoun and Victoria, while all counties engaged in soybean production combined to harvest over 600,000 bushels of soybeans with a market value of approximately $3.7 million in 1997 (Table 1-7).

1.4.3    Livestock Production

According to the 1997 Census of Agriculture, livestock marketed in the South Central Texas region had a market value of over $645 million, or about 2.2 times the value of crop production.  Major types of livestock produced in the area include cattle and calves, beef cattle, and sheep and lambs.  Layers, pullets, and broilers also contribute significantly to the region’s livestock production, with Gonzales County producing over 98.7 percent of these types of livestock.  In 1997, the region’s leading livestock producing counties by market value were Gonzales, Uvalde, Medina, and Wilson Counties (Table 1-8).

1.4.4    Mining

The South Central Texas Region contains many sand and gravel quarries and is also rich in petroleum products including oil, natural gas, and lignite.  Much of the stone quarried is used in the production of cement.  The leading cement producing areas in the region are located in Bexar and Hays Counties.  According to the 1992 Economic Census, approximately 1,000 people were employed in the mining of stone, sand, and gravel, with these products having a market value of over $42 million in 1992.[6]  Most of the region’s stone, gravel, and sand mining activities are located in Bexar, Comal, Gonzales, and Victoria Counties.

The region also derives a significant portion of its mining income from oil and gas activities.  All but two counties (Comal and Hays) derived some of their revenues from oil and gas production in 1998.  Oil and gas production in the remaining 19 counties generated over $290 million in 1998 and provided approximately 3,500 jobs in the region.  The leading oil and gas producing counties in the region are Refugio, Goliad, Victoria, Atascosa, and DeWitt.

1.4.5    Manufacturing[7]

In 1992, manufacturing facilities contributed over $9 billion in sales and provided 56,460 jobs in the South Central Texas Region.[8]  Sales of manufactured goods accounted for 21.3 percent of the total market value of all products produced in the region in 1992, including farming and livestock (Table 1-9).  The leading manufacturing counties, by value of shipments, in the region are Bexar, Calhoun, Victoria, and Guadalupe.  The leading types of manufacturing plants in the region (in 1992) were printing and publishing; food and kindred products; industrial machinery and equipment; and stone, clay, and glass products.

1.4.6    Trades and Services[9]

In 1992, wholesale trade, retail trade, and services contributed over $32 billion in sales or receipts and provided 285,293 jobs in the South Central Texas Region, with trades and services sales accounting for 76 percent of the total market value of all products produced in the region, including farm and livestock products (Table 1-10).[10]  Wholesale trade accounted for 42.5 percent of the total sales or receipts and provided 11.2 percent of the jobs within the trades and services classification in 1992.  The leading type of wholesale trade within the South Central Texas Region is durable goods, which includes automobile parts and supplies; lumber and construction materials, and machinery, equipment, and supplies.  In 1992, the leading counties in wholesale trade were Bexar, Victoria, Guadalupe, and Comal.

Retail trade accounted for 37.1 percent of the total sales or receipts and provided 43.1 percent of the jobs within the trades and services classification in 1992.  The leading types of retail trade within the South Central Texas Region are restaurants, automotive dealers and service stations, food stores, and apparel and accessory stores.  In 1992, the leading counties in retail trade were Bexar, Victoria, Comal, and Hays.

Services accounted for 20.4 percent of the total sales or receipts and provided 45.7 percent of the jobs within the trades and services classification in 1992.  The leading types of services within the South Central Texas Region are health services, business services, engineering and management services, and membership organizations.

1.5       Water Uses[11]

Water use in 1990 within the South Central Texas Region is summarized for each of the river and coastal basin areas of the region in the following paragraphs.

In 1990, total water use in that part of the Rio Grande Basin located in the South Central Texas Region (part of Dimmit County) was approximately 198 acre-feet (acft) of which 6 acft (3 percent) was used for municipal-type (household) purposes, while the remaining 192 acft was for livestock watering.

In the Nueces River Basin, groundwater resources supply about 76 percent of the water used for all purposes in the basin, with surface water resources supplying the remaining 24 percent.  In 1990, total water use in the basin was 615,752 acft, of which 582,121 acft (94.5 percent) occurred in the South Central Texas Region.  Irrigated agriculture accounts for nearly 93 percent of all the water used in that portion of the Nueces River Basin located in the planning region, while municipal water use accounts for only about 4.1 percent.

In the San Antonio River Basin, groundwater resources supply about 88 percent of the water used for all purposes, with surface water resources supplying the remaining 12 percent.  In 1990, water use for municipal, industrial, and agricultural purposes within the South Central Texas Region totaled 327,633 acft.  Municipal water use accounts for about 67 percent of all water use in that portion of the basin located in the planning region, with water used for irrigated agriculture accounting for about 20 percent.  Groundwater resources supply about 99 percent of the water for municipal use in the basin and about 80 percent of the water used for irrigated agriculture.

In the Guadalupe River Basin, groundwater resources supply about 48 percent of the water used for all purposes, with surface water resources supplying the remaining 52 percent.  Total basin water use in 1990 was 116,519 acft, of which 108,159 acft (92.8 percent) was used in the South Central Texas Region.  Municipal is the largest water use category in that part of the basin located within the planning region, accounting for more than 40 percent of the total water use, followed by manufacturing, which accounts for about 24 percent.

In 1990, total water use in that part of the Lower Colorado River Basin located in the South Central Texas Region (parts of Caldwell and Kendall Counties) was approximately 403 acft.  Of this total, 236 acft (58.6 percent) was used for municipal purposes, 20 acft (5 percent) for irrigation purposes, and the remaining 147 acft for livestock purposes.

Total basin water use in 1990 for the Lavaca River Basin was 277,458 acft, of which only 1,003 acft was used inside the South Central Texas Region.  Municipal water use accounts for about 58.8 percent of all water use in that portion of the basin located in the planning region, followed by livestock use, which accounts for 30.4 percent.

In 1990, water use for municipal, industrial, and livestock purposes in that portion of the Colorado-Lavaca Coastal Basin located in the South Central Texas Region totaled 6,573 acft.  Industrial water use is the largest in that part of the basin located within the planning area, accounting for nearly 96 percent of all water used.

In the Lavaca-Guadalupe Coastal Basin, annual water use totaled 87,489 acft in 1990, of which 72,694 acft was used within the South Central Texas Region.  The largest water-using category in that part of the basin located within the planning region is irrigated agriculture, which accounts for about 65 percent of all water used.

In the San Antonio-Nueces Coastal Basin, annual water use totaled about 29,000 acft in 1990, of which 2,375 acft was used within the South Central Texas Region.  The largest water use category in that part of the basin located within the planning region is municipal, which accounts for about 56 percent of all water used.

1.6       Major Municipal and Manufacturing Water Providers[12]

The TWDB has defined a major water provider as follows: “A major water provider is an entity which delivers and sells a significant amount of raw or treated water for municipal and/or manufacturing use on a wholesale and/or retail basis.” The SCTRWPG decided that a major water provider is an entity that has commitments to provide 500 acft or more of raw or treated water for municipal and/or manufacturing use, on a wholesale or retail basis, to water users other than its own direct customers.  The SCTRWPG has identified six major municipal and manufacturing water providers in the South Central Texas Region, as follows: the San Antonio Water System, Bexar Metropolitan Water District, Canyon Regional Water Authority, Guadalupe-Blanco River Authority, New Braunfels Utilities, and the City of San Marcos.  Each major water provider is briefly described below.  Detailed water demand projections for each major water provider are presented in Section 2.10.

1.6.1    San Antonio Water System

The San Antonio Water System (SAWS) is a public utility owned by the City of San Antonio, and its sole water supply source is the Edwards Aquifer.  SAWS has 260,000 separate customers, and serves approximately 1 million people in the urbanized portion of Bexar County.  The water supply service area includes most, but not all, of the City of San Antonio, several suburban municipalities, and adjacent areas of Bexar County.  In addition to serving its own retail customers, SAWS also provides wholesale water supplies to several utility systems within Bexar County (Section 2.10).  SAWS is in the process of developing supplies from other sources, including surface water from both the San Antonio and Guadalupe River Basins and from the Simsboro formation within the Carrizo Aquifer.

1.6.2    Bexar Metropolitan Water District

Created in 1945 by the Texas State Legislature, Bexar Metropolitan Water District (BMWD) serves a population of more than 250,000 in the west and northwest portions of Bexar County, some portions of the City of San Antonio, and areas in Atascosa and Medina Counties.  It is the second-largest water supplier in Bexar County and, at present, obtains most of its water from the Edwards Aquifer.  However, BMWD is in the process of developing supplies from other sources including surface water from both the San Antonio and Guadalupe River Basins.

1.6.3    Canyon Regional Water Authority

Canyon Regional Water Authority (CRWA) is a subdivision of the State of Texas created by the Texas Legislature in 1989.  CRWA is the water planning and development agency for water purveyors that serve large areas of Guadalupe County and portions of Bexar, Hays, Wilson, and Comal Counties.  It works as a partnership of 11 water supply corporations, cities and districts responsible for acquiring, treating, and transporting potable water (Section 2.10).  CRWA owns and operates a treatment plant at Lake Dunlap on the Guadalupe River for surface water purchased from the GBRA.  CRWA’s sources of supply also include groundwater pumped from the Edwards Aquifer, however, CRWA is encouraging development of alternative sources for users not located directly over the aquifer.

1.6.4    Guadalupe-Blanco River Authority

The Guadalupe-Blanco River Authority (GBRA) was created by the Texas Legislature in 1933 for the purpose of controlling, storing, preserving, and distributing the waters of the Guadalupe River Basin for all useful purposes.  GBRA is a regional entity serving Hays, Comal, Guadalupe, Caldwell, Gonzales, DeWitt, Victoria, Kendall, Refugio, and Calhoun Counties.  GBRA’s activities include supplying hydroelectric power through operations of six hydroelectric dams located on the Guadalupe River in Guadalupe and Gonzales Counties, supplying potable water, treatment of wastewater, and supplying raw water through management of substantial run-of-river rights and storage rights in Canyon Reservoir.  As of July 1999, the Authority has contracts to provide water to 28 public and private entities (Section 2.10).

1.6.5    New Braunfels Utilities

New Braunfels Utilities provides water to the City of New Braunfels and three utilities that serve neighboring areas (Section 2.10).  The utility obtains its water from run-of-river rights, purchased water from Canyon Reservoir (GBRA), and Edwards Aquifer pumping rights.  If future water supplies are needed in its service area, the utility plans to purchase additional water from Canyon Reservoir to feed an expansion of New Braunfels Utilities’ water treatment plant.

1.6.6    City of San Marcos

The City of San Marcos has historically obtained its water supply from the Edwards Aquifer.  In order to reduce pumpage from the aquifer and increase its water supply, the City purchased 5,000 acft/yr of surface water from Canyon Reservoir (GBRA).  In addition to supplying water to the permanent residents of San Marcos, the City supplies water to Southwest Texas State University, and the Texas Education Foundation (Section 2.10).

 


[1] Texas Water Development Board (TWDB) “Continuing Water Resources Planning and Development for Texas,”
 May 1977.

[2] TWDB, Op. Cit., May 1977.

[3] HDR Engineering, Inc. (HDR), et al., “Trans-Texas Water Program, West Central Study Area, Phase I Interim
 Report,” Volume 2, San Antonio River Authority, et al., May 1994.

[4] 1997 Census of Agriculture, Volume 1 Geographic Area Series, “Table 1. County Summary Highlights: 1997.”

[5]  Information summarized from reports by the Texas Comptroller’s Office.

[6] Data for 1992 are the most recent data available.

[7] Source: 1992 Census of Manufacturing, U.S. Department of Commerce.

[8] Data for 1992 are the most recent data available.

[9]   Source: 1992 Economic Census, U.S. Department of Commerce.

[10] Data for 1992 are the most recent data available.

[11] TWDB, “Water For Texas: A Consensus-Based Update to the State Water Plan,” Austin, Texas, August 1997.

[12] The following section contains information provided by the major municipal and manufacturing water providers.