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Texas Tidbits

Do you know where your water comes from?

By June 2001Comments

Water is fast becoming a precious commodity. What flows so freely now from the kitchen sink may be harder to come by in the near future. Sound ridiculous? Not to the residents of south Central Texas.

According to the Lower Colorado River Authority (LCRA), Bexar County, which includes most of the greater San Antonio metropolitan area, will be approximately 350,000 acre-feet short of its annual water needs by the year 2050. (An acre-foot is the volume of water that would cover one acre to a depth of one foot.) The Edwards Aquifer is currently the city’s main source of water. But despite the fact that San Antonio has a good conservation record and has restricted the amount of water it pumps from the Edwards Aquifer (it is environmentally sensitive), the city needs a long-term solution.

The search might be over. The LCRA and the San Antonio Water System (SAWS) have found a possible interregional solution to meet San Antonio’s future shortage. The plan was devised to help not only San Antonio but also the Colorado River basin—and in turn would help resolve the area’s projected shortages for rural communities. The LCRA/SAWS Joint Water Conservation and Development Plan would develop 330,000 acre-feet of water a year—more than 100 billion gallons of water—through off-channel storage sites, advanced conservation programs, and the use of ground water from LCRA wells at its irrigation and coastal properties during drought. All for a small fee, of course. San Antonio would pick up the estimated $800 million to $1 billion tab and in return take almost half of the water—about 150,000 acre-feet—for no longer than eighty years.

Naturally, there has been some concern from environmental groups that this proposal could reduce the flow of freshwater into west Matagorda Bay—the second largest estuary on Texas’ Gulf Coast—which could prove detrimental to the natural ecosystems of that area. But the LCRA and the SAWS have said that for up to seven years, engineering and environmental studies will be conducted to identify the plan’s impacts on the basin’s environment. Both entities have agreed not to go forward with the plan unless environmental issues are satisfactorily addressed. Although the State Legislature in May unanimously approved legislation that would allow the LCRA to sell water to San Antonio, there are still many other hurdles to cross before the plan becomes viable, including approval of a final contract by the LCRA and the SAWS; environmental studies; and permits from state and federal agencies to obtain water rights, authorize reservoir construction and water diversion, and address environmental concerns.

Texas is making an effort to address water concerns region by region. But what about you? Do you know where your water comes from? In addition to river sources, a great deal of our water comes from below ground, from aquifers. Find out which one supplies water to you.

The Ogallala, which is underneath 46 counties of the Texas Panhandle, is the southernmost extension of the largest aquifer in North America, stretching to South Dakota and covering 174,000 square miles. Approximately 95 percent of the water pumped from the Ogallala is used for irrigation. Compared with a gigantic sponge, the Ogallala ranges in thickness from less than a foot to 1,300 feet and holds enough water to fill Lake Huron.

The Gulf Coast Aquifer extends through 54 counties from the Rio Grande to Louisiana forming a band that parallels the Texas coastline. The system is divided into three water-producing units (45 percent of the water in each unit is used for municipalities and irrigation).

The Edwards rounds through nine counties from Kinney County through the San Antonio area northeastward to the Leon River in Bell County. More than 50 percent of the water pumped from Edwards is for municipal use, and San Antonio relies solely on this water source for its municipal supply. The aquifer feeds several recreational springs.

The Trinity Group aquifer, which is the primary water source for much of the Hill Country, extends in a belt through the central part of the state from the Red River in the north to just beyond the eastern edge of Medina County. The aquifer recharges slowly.

The Edwards-Trinity aquifer underlies the Edwards Plateau and extends from the Hill Country westward to the Trans-Pecos region. In the northwest portion of the Edwards-Trinity, irrigation accounts for approximately 70 percent of the total aquifer use.

The Seymour aquifer is often referred to as the “north-central Texas alluvial aquifers” because it is located within 22 separate areas of alluvium in parts of twenty Texas counties near the upper Red and upper Brazos River basins. The salinity has increased in some heavily pumped areas to the point that the water is not suitable for municipal use.

The Hueco-Mesilla Bolson aquifers are located in West Texas near El Paso and Hudspeth counties and extend into New Mexico and Mexico. The Hueco-Bolson, east of the Franklin Mountains, consists of nine thousand feet of clay, silt, sand, and gravel. It is the principal source of drinking water for El Paso and Juárez. West of the Franklin Mountains, the Mesilla Bolson reaches up to two thousand feet in thickness and contains three separate water-producing zones.

The Cenozoic Pecos Alluvium aquifer is located in the upper Pecos River Valley of West Texas. It is the principal source of water for irrigation in Reeves and northwestern Pecos counties. Of the total water pumped, 81 percent is used for irrigation.

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