Texas Almanac, 2000-2001 Page: 63
672 p. : col. ill., ports. ; 23 cm.View a full description of this book.
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Environment
near the surface of most soils.
Cattle grazing is the chief economic use of the various
salt-tolerant cordgrasses and sedges. Many areas are
managed for wetland wildlife. Recreation is popular on the
barrier islands. Providing fresh water and access to graz-
ing areas are the major management concerns.
19. Flatwoods Soils
The Flatwoods area includes about 2.5 million acres of
woodland in humid southeast Texas just north of the Coast
Prairie and extending into Louisiana. The landscape islevel to gently undulating. Surface drainage is slow.
Upland soils are mostly deep, light-colored, acid loams
with gray, loamy or clayey subsoils. Bottomland soils are
deep, dark-colored, acid clays and loams. The water table
is near the surface at least part of the year.
The land is mainly used for forest; cattle are grazed in
some areas. Woodland management problems include
seedling survival, invasion of hardwoods in pine stands,
effects of logging on water quality and control of the south-
ern pine beetle. aWater Resources
Beginning in September 1993, regulation of water qual-
ity of water resources of the state were placed in the juris-
diction of the Texas Natural Resource Conservation
Commission. In addition, the Texas Water Development
Board is responsible for the development of Texas water
resources and the financing of facilities, such as dams,
that are part of that development. The TWDB furnished the
information for this section of the Texas Almanac.
Texas, through its river authorities, municipalities, water
districts and state-level agencies, exercises the dominant
role in development of municipal and industrial water sup-
plies. Approximately 80 percent of the money invested in
the state's water projects has been provided by Texas enti-
ties of government.
To develop a comprehensive statewide water plan, the
75th Texas Legislature, in 1997, required the TWDB to
divide the state into 16 regional water-planning areas.
Each area's Regional Water Planning Group (RWPG),
whose membership includes representatives from 11
interest groups, will adopt a water plan addressing conser-
vation of water supplies, meeting future water needs and
responding to future droughts, by Sept. 1, 2000. The
TWDB is charged with incorporating these into a compre-
hensive state water plan by Sept. 1, 2001.
For more information, see the TWDB Web page at
www.twdb.state.tx.us.
Ground-water Supplies and Use
Texas has historically relied on its wealth of fresh to
slightly saline water that underlies more than 81 percent of
the state. Fifty-six percent of the more than 13.5 million
acre-feet of water currently being used in Texas is derived
from underground sources that occupy nine major and 20
minor aquifers. Approximately 75 percent of the ground
water produced is used for irrigating agricultural crops,
especially in the Panhandle region. Ground water also
supplies about 41 percent of the state's municipal needs.
Major Aquifers (see map on next page):
Ogallala - The Ogallala aquifer extends under 46 coun-
ties of the Texas Panhandle and is the southernmost
extension of the largest aquifer (High Plains aquifer) in
North America. The Ogallala Formation of late Miocene to
early Pliocene age consists of heterogeneous sequences
of coarse-grained sand and gravel in the lower part, grad-
ing upward into clay, silt and fine sand. In Texas, the Pan-
handle is the most extensive region irrigated with ground
water. Approximately 95 percent of the water pumped from
the Ogallala is used for irrigation. Water-level declines are
occurring in part of the region because of extensive pump-
ing that far exceeds recharge. Water-conservation mea-
sures by both agricultural and municipal users are being
promoted in the area. A new computer model of the north-
ern portion of the Ogallala aquifer is being developed by
the University of Texas Bureau of Economic Geology, and
several agencies are investigating playa recharge and
agricultural re-use projects.
Gulf Coast Aquifer - The Gulf Coast aquifer forms an
irregularly shaped belt that parallels the Texas coastline
and extends through 54 counties from the Rio Grande
northeastward to the Louisiana border. The aquifer system
is composed of the water-bearing units of the Catahoula,
Oakville, Fleming, Gollad, Willis, Lissle, Bentley, Mont-
gomery and Beaumont formations. This system has
been divided into three major water-producing compo-
nents referred to as the Chlcot, Evangeline, and Jasper
aquifers. Municipal uses account for about 51 percent and
irrigation accounts for about 36 percent of the total pump-
age from the aquifer. Water quality is generally good north-
east of the San Antonio River basin, but deteriorates to thesouthwest. Years of heavy pumpage have caused signifi-
cant water-level declines in portions of the aquifer. Some
of these declines have resulted in significant land-surface
subsidence, particularly in the Houston-Galveston area.
Edwards (Balcones Fault Zone) - The Edwards (BFZ)
aquifer forms a narrow belt extending through nine coun-
ties from a ground-water divide in Kinney County through
the San Antonio area northeastward to the Leon River in
Bell County. A poorly defined ground-water divide in Hays
County hydrologically separates the aquifer into the San
Antonio and Austin regions. Water in the aquifer occurs in
fractures, honeycomb zones and solution channels in the
Edwards and associated limestone formations of Creta-
ceous age. More than 50 percent of aquifer pumpage is for
municipal use, while irrigation is the principal use in the
western segment. San Antonio is one of the largest cities
in the world that relies solely on a single ground-water
source for its municipal supply. The aquifer also feeds sev-
eral well-known recreational springs and underlies some
of the most environmentally sensitive areas in the state.
In 1993, the Edwards Aquifer Authority was created by
the legislature to regulate aquifer pumpage for the benefit
of all users: agricultural, municipal and environmental. The
authority's jurisdiction extends from Uvalde County
through a portion of Hays County. Barton Springs-
Edwards Aquifer Conservation District provides aquifer
management for the remaining portion of Hays and south-
ern Travis counties. The EAA has an active program to
educate the public on water conservation and also oper-
ates several active groundwater reharge sites. The San
Antonio River Authority also has a number of flood-control
structures that effectively recharge the aquifer.
Conservation districts are promoting the use of more-
efficient irrigation techniques, and market-based, volun-
tary transfers of unused agricultural water rights to munici-
pal uses are becoming more common.
Carrizo-Wllcox - Extending from the Rio Grande in
South Texas northeastward into Arkansas and Louisiana,
the Carrizo-Wilcox aquifer provides water to all or parts of
60 counties. The Wilcox Group and overlying Carrizo Sand
form a hydrologically connected system of sand locally
interbedded with clay, silt, lignite and gravel. Throughout
most of its extent in Texas, the aquifer yields fresh to
slightly saline water, which is used primarily for irrigation in
the Winter Garden District of South Texas and for public
supply and industrial use in Central and Northeast Texas.
Because of excessive pumping, the water level in the aqui-
fer has been significantly lowered, particularly in the arte-
sian portion of the Winter Garden District of Atascosa, Frio
and Zavala counties and in municipal and industrial areas
located in Angelina and Smith counties.
Trinity Group - The Trinity aquifer consists of basal Cre-
taceous-age Trinity Group formations that extend from the
Red River in North Texas to the Hill Country of Central
Texas. Formations comprising the aquifer include theTwin
Mountains, Glen Rose and Paluxy. Where the Glen
Rose thins or is absent, the Twin Mountains and Paluxy
formations coalesce to form the Antlers Formation. In the
southern extent, the Trinity includes the Glen Rose and
underlying Travis Peak formations. Water from the Antlers
portion of the Trinity is used mainly for irrigation in the out-
crop area of North and Central Texas. Elsewhere, water
from the Trinity is used primarily for municipal and domes-
tic supply. Extensive development of the Trinity aquifer in
the Dallas-Fort Worth and Waco areas has historically
resulted in water-level declines of several hundred feet.
Edwards-Trinity (Plateau) - This aquifer underlies the
Edwards Plateau, extending from the Hill Country of Cen-
tral Texas westward to the Trans-Pecos region. The aquifer
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Ramos, Mary G. Texas Almanac, 2000-2001, book, 1999; Dallas, Texas. (https://texashistory.unt.edu/ark:/67531/metapth162509/m1/63/: accessed May 6, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting Texas State Historical Association.