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Infrastructure – Water

Unsurprisingly, the Gulf Coast’s history and fortunes are tied to water. All of Texas’ rivers eventually find their way to the Gulf Coast, where river deltas, salt marshes, bays and seawater meet and mingle. The coastal prairies and metropolitan areas alike receive moist winds from the southeast, punctuated by storms that can come from any direction.

The Gulf Coast region is on the higher end of the state’s rainfall scale, ranging from averages of 38 inches annually in Waller County to 54 inches in Chambers and Harris counties, and even more in other places. Statewide average annual rainfall amounts range from 10 inches annually in far West Texas to more than 55 inches in the Beaumont/Port Arthur area.1

One major aquifer, appropriately named the Gulf Coast aquifer, lies beneath the entire Texas coast, including every county in this region (Exhibit 24). In all, the Gulf Coast region tapped surface and groundwater sources for 2,352,592 acre-feet of water in 2006, as estimated by the Texas Water Development Board (TWDB) using the most recent data available. (An acre-foot is the amount needed to cover an acre of land with a foot of water, or 325,851 gallons, about the annual consumption of two to three Texas households. A regulation Olympic-sized swimming pool holds about two acre-feet.)

Exhibit 24

Gulf Coast Region, Major Surface and Groundwater Features

See text alternative.

Source: Texas Water Development Board.

View surface and groundwater features.

Much of the region’s surface water supply is taken directly from the rivers rather than from reservoirs.

The Colorado, Brazos, San Jacinto and Trinity rivers, along with lesser streams, provided the region with 69.2 percent of its total supplies, or 1.6 million acre-feet in 2006. The Gulf Coast aquifer’s 724,578 acre-feet accounted for 30.8 percent of the total.

The region’s municipalities consumed the largest share (36.8 percent) of its water in 2006, at 865,986 acre-feet. Irrigation accounted for 725,844 acre-feet (30.9 percent) of water use, while manufacturing accounted for the third-largest portion at 25 percent or 589,255 acre-feet.

Of the remaining sectors, steam-electric plants (which convert water to steam to produce electricity) consumed 5.7 percent of the total, while mining and livestock used 1 percent and 0.6 percent, respectively (Exhibit 25).

Of the three sectors that use nearly 93 percent of the region’s water, only municipal use is fairly evenly divided between groundwater and surface water; irrigation and manufacturing get the vast majority of their supplies from surface waters. Less than 31 percent of the region’s total supply comes from underground (Exhibit 26).2

Exhibit 25

Gulf Coast Region, Total Water Use, 2006

Municipal use accounted for 36.8%, irrigation 30.9%, manufacturing 25.0%, steam electric 5.7%, mining 1.0% and livestock is 0.6%.

Total Water Consumption:
2,352,592 acre-feet

(equivalent to 766.6 billion gallons)

Source: Texas Water Development Board.

Exhibit 26

Gulf Coast Region, Water Sources by Sector, 2006

In acre-feet:MunicipalManufac-
turing
Mining Steam
Electric
IrrigationLivestockTotal
Surface Water 414,377
(52%)
533,740
(9%)
18,671
(18%)
126,183
(6%)
528,009
(27%)
7,034
(53%)
1,628,014
(31%)
Ground Water 451,609
(48%)
55,515
(91%)
4,107
(82%)
7,711
(94%)
197,835
(73%)
7,801
(47%)
724,578
(60%)

Source: Texas Water Development Board and Texas Comptroller of Public Accounts.

Exhibit 27

Gulf Coast Region Regional Water Planning Groups

see alternative

Source: Texas Water Development Board.

View regional planning groups.

In 1997, Texas Senate Bill 1 required TWDB to divide the state into 16 regions under the administration of regional water planning groups (RWPGs). Most of the Gulf Coast region lies in Region H, with its three westernmost counties being part of Region K (Lower Colorado). One county, Wharton, is divided between Region K and Region P (Lavaca) to the west (Exhibit 27).3

Exhibit 28

Gulf Coast Water Use by Sector, 2000-2060 (acre-feet)

Sector 2000 Actual 2020 Projected 2040 Projected 2060 Projected
Irrigation 1,188,602 1,100,864 1,044,392 982,162
Livestock 13,098 13,098 13,098 13,098
Manufacturing 638,040 796,505 900,539 965,361
Mining 68,149 81,372 86,398 91,025
Municipal 852,667 1,117,657 1,391,652 1,731,548
Steam Electric 149,220 192,685 256,974 319,811
Total 2,909,776 3,302,181 3,693,053 4,103,005

Source: Texas Water Development Board.

SB 1 requires various stakeholder groups to be represented on RWPGs, including agricultural, municipal, environmental and business interests, electric generating utilities, water districts and river authorities. Each RWPG also may add other representatives at will.4

SB 1 requires RWPGs to evaluate their current water supplies and estimate their supplies and uses over a 50-year period; the current planning horizon extends to 2060. Based on 2000 data, the Gulf Coast region’s overall water use is projected to rise by 41 percent to 4,103,005 acre-feet in 2060.

Irrigation is the only category of water use expected to decline by 2060, by 17.4 percent, to 982,162 acre-feet. Steam-electric use is expected to rise to 319,811 acre-feet annually, an increase of 114.3 percent, slightly ahead of the 103.1 percent growth in municipal use, although the volumes of water used in the cities are expected to be much larger (1,731,548 acre-feet in 2060). Manufacturing water use is projected to increase significantly (51.3 percent) by 2060, up to levels similar to that for irrigation (965,361 acre-feet in 2060), while mining uses are expected to rise to 91,025 acre-feet annually, a 33.6 percent growth. Water use for livestock is not expected to change significantly (Exhibit 28).5

Exhibit 29

Gulf Coast Region, Major Lakes and Reservoirs

Lake/Reservoir Name River Basin Year 2010 projected yield (acre-feet) Conservation Storage Capacity (acre-feet)
Addicks Reservoir San Jacinto No WS 200,800
Anahuac, Lake Trinity 14,326 35,300
Barker Reservoir San Jacinto No WS 209,000
Brazoria Reservoir Brazos Pass-through 21,970
Cedar Bayou Generating Pond Trinity-San Jacinto Cooling 13,750
Conroe, Lake San Jacinto 79,800 416,188
Eagle Lake Colorado Sys. Op. 9,600
Eagle Nest Lake/Manor Lake Brazos 0 18,000
Gulf Coast Water Authority Reservoir San Jacinto-Brazos 98,805 7,308
Houston, Lake San Jacinto 168,000 128,863
Lewis Creek Reservoir San Jacinto 0 16,400
Smithers Lake Brazos 0 18,700
South Texas Project Reservoir Colorado Sys. Op. 202,600
Wallisville Lake Trinity Sys. Op. 58,000
William Harris Reservoir Brazos No WS 9,200
Total 360,931 1,365,679

Note: No WS – No water supply function; Sys. Op. – Reservoir operated as part of a system, no individual yield total available.
Source: Texas Water Development Board.

The steep increase expected in municipal use, as well as the growth of the steam-electric sector, are driven in large part by demand from Harris County.

The county has about 68 percent of the region’s population and accounted for 70.2 percent of its municipal water use in 2000; its share is expected to be nearly 63 percent in 2060. Its portion of the region’s water use for electrical generation is expected to rise from about 5.1 percent to nearly 14.5 percent by 2060. These fast-growing sectors will help drive Harris County’s projected share of the region’s total water use from 33.4 percent to nearly 40 percent by 2060.6

Surface Water

Many smaller streams and bayous supplement the Gulf Coast region’s four major rivers as they wind towards the coast. One river, the San Jacinto, is entirely contained within the region, while the Colorado River runs from the New Mexico border down to Matagorda Bay. The Brazos and Trinity rivers both have long runs from north Texas to the Gulf of Mexico, the Brazos arriving near Freeport and the Trinity, like the San Jacinto, emptying into upper Galveston Bay.

Much of the region’s surface water supply is taken directly from the rivers rather than from reservoirs. In fact, only four of the region’s 15 reservoirs have any water supply yield projected for the year 2010, although three other “system” reservoirs contribute to those yields. Although the storage capacity for the region’s reservoirs is about 1.4 million acre-feet, their projected yield in 2010 is less than 361,000 acre-feet (Exhibit 29).7

The Gulf Coast region includes two of the state’s coastal bays, Matagorda Bay and Galveston Bay, the state’s largest. Fresh water from rivers flowing into bays and estuaries is critical to maintaining ecosystems that support the state’s coastal fishing, shrimp, oyster and tourism industries.

Groundwater

The Gulf Coast region’s heavy use of groundwater, however, has become problematic in some areas, due to the phenomenon known as “subsidence.”

As noted above, the Gulf Coast region has only one major aquifer, the Gulf Coast Aquifer, which, along with a very small amount of groundwater from a minor aquifer called the Brazos River Alluvium, provides about 30 percent of the region’s water supply. Aquifers are water-bearing layers of permeable rock, sand or gravel. They can be shallow or deep, with waters that are fresh, brackish or saline. In the case of the Gulf Coast, the freshwater-saturated layers are about 1,000 feet thick and the water quality in the section under the region is considered good.

The Gulf Coast region’s heavy use of groundwater, however, has become problematic in some areas, due to the phenomenon known as “subsidence.” Removing large amounts of groundwater lowered the water level in the aquifer’s layers of clay and sand and as a result the strata have compacted and the land above has settled.

Exhibit 30

Gulf Coast Region, Groundwater Conservation Districts

See text alternative.

Source: Texas Water Development Board.

View groundwater conservation districts.

In parts of Harris and Galveston counties, the ground level dropped from one to nine feet during the 20th century. Consequently, several counties in the region have shifted significant portions of their groundwater use to surface water supplies, although identifying those new sources can be challenging, since the water in many Texas rivers is already fully allocated to permit holders (whether that water “right” is being used or not).

This situation is only a piece of a larger, statewide problem – that of shrinking groundwater supplies. Both TWDB and all regional planning groups anticipate a statewide reduction in groundwater supplies. TWDB projects that Texas’ groundwater supplies, assuming current permits and infrastructure, will fall by 32 percent between 2010 and 2060. The regional planning groups collectively anticipate a 22 percent fall in state supplies over the same period.8

Texas laws passed in 1999 and 2001 encourage the use of groundwater conservation districts (GCD), led by locally elected or appointed officials, to manage groundwater sources. These districts allow for some local control over the pumping and export of groundwater resources, to which landowners may have extensive property rights.

In the Gulf Coast region, only Liberty and Chambers counties are not covered by a GCD or, in the case of Fort Bend, Harris and Galveston counties, a subsidence district. The Harris-Galveston and Fort Bend Subsidence Districts are unique in the state and, although they predate the law that authorized the GCDs, they have similar powers to regulate groundwater use (Exhibit 30).9

GCDs generally follow county boundaries, but aquifers underlie multiple counties, which can make groundwater management complex and disjointed. To provide for greater cohesiveness, state law requires TWDB, together with the Texas Commission on Environmental Quality, to create Groundwater Management Areas, or GMAs. Groundwater districts within GMAs must meet at least annually to develop mutually agreeable “desired future conditions” for the aquifers based on TWDB models and other hydrology information. Once an amount is determined, RWPGs within the GMA may use the data for planning, and GCDs may issue groundwater withdrawal permits within the amount of “managed available groundwater” determined by the GMA.10

The Harris-Galveston and Fort Bend Subsidence Districts are unique in the state and, although they predate the law that authorized the GCDs, they have similar powers to regulate groundwater use.

PHOTO:Greater Houston Convention and Visitors Bureau

Endnotes

All links were valid at the time of publication. Changes to web sites not maintained by the office of the Texas Comptroller may not be reflected in the links below.

  • 1 Texas Water Development Board, Water for Texas, 2007, Volume II (Austin, Texas, 2007), pp. 130, 132, http://www.twdb.state.tx.us/publications/reports/State_Water_Plan/2007/2007StateWaterPlan/CHAPTER%205_final%20112906.pdf. (Last visited January 18, 2010.)
  • 2 Data provided by the Texas Water Development Board, October 27, 2009.
  • 3 Texas Water Development Board, Water for Texas, 2007, Volume II (Austin, Texas, 2007), pp. 55, 73, 103, http://www.twdb.state.tx.us/publications/ reports/State_Water_Plan/2007/2007StateWater Plan/CHAPTER%202_REGIONAL%20H_FINAL%20112706.pdf; (Last visited February 17, 2010.)
  • 4 31 Tex. Admin. Code §357.4 (2006) (Tex. Water Development Board, Designation of Regional Water Planning Groups.)
  • 5 Data provided by the Texas Water Development Board, July 22, 2009.
  • 6 Data provided by the Texas Water Development Board, October 27, 2009.
  • 7 Texas Water Development Board, Water for Texas, 2007, Volume II (Austin, Texas, 2007), pp. 357-361, (Last visited January 18, 2010.)
  • 8 Texas Water Development Board, Aquifers of the Gulf Coast of Texas by Robert E. Mace, Sarah C. Davidson, Edward S. Angle and William F. Mullican, III, eds., (Austin, Texas, February 2006), Chapter 7, “100 Years of Groundwater Use and Subsidence in the Upper Texas Gulf Coast,” by Thomas A. Michel, pp. 141-143, http://www.twdb.state.tx.us/publications/reports/GroundWaterReports/GWReports/R365/ch07-HGSD%20TWDB%202005%20Papera.pdf; Texas Water Development Board, Water for Texas, 2007, Volume II, (Austin, Texas, 2007), p. 176, http://www.twdb.state.tx.us/publications/reports/State_Water_Plan/2007/2007StateWaterPlan/CHAPTER%207%20FINAL_112906.pdf. (Last visited January 18, 2010.)
  • 9 Texas Water Development Board, Aquifers of the Gulf Coast of Texas, pp. 143 – 148.
  • 10 Texas Water Development Board, A Streetcar Named Desired Future Conditions: The New Groundwater Availability for Texas (Revised), by Robert E. Mace, Rima Petrossian, Robert Bradley, William F. Mullican, III and Lance Christian (Austin, Texas, 2008), pp. 2-4, http://www.twdb.state.tx.us/GwRD/pdfdocs/03-1_mace.pdf. (Last visited January 18, 2010.)
  • 14 Elizabeth Cruce Alvarez, ed., Texas Almanac 2010-2011 (Denton, Texas: Texas State Historical Association, 2010), pp. 125-132, 225, 243, 271, 316, 324.
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