Extreme drought is showing its gaunt face across much of Texas this winter. What will happen in Central Texas if dry weather continues through the spring and summer?
It's little known, but Central Texas has a wealth of water. It is stored in two manmade lakes – Travis and Buchanan – formed by damming the Colorado River. LCRA manages the lakes so that together, even during a drought, they provide plenty of water for most purposes – drinking water, industry, agriculture irrigation and downstream flows for fish and other aquatic life.
“We’re on top of the situation,” said Karen Bondy, manager of LCRA River Services. “The lakes are storing the water as they were designed to do, and we’re controlling the use of it according to a state-approved management plan.”
Recreation hazards
Boaters may see things differently. The look of the lakes will change significantly if the drought continues through spring and summer, as forecasted. In fact, they could drop to their lowest levels in more than five years. So, although there’s no shortage of water for consumption, water recreation will become more challenging. Shorelines are widening along the upper end of Lake Travis and along some coves, and a few public boat ramps are high and dry. The shrinking surface will be more obvious at Lake Buchanan, which is relatively shallow. Travis, a very deep lake, will remain navigable, but hazards will become more exposed, said Jim Richardson, manager of LCRA Water Surface Management.
“What throws boaters off is the level of the lakes, and the location and nature of hazards change,” Richardson said. “They can be very safe if they take boater education classes, have an aerial contour map, and pay attention to hazards and markers.”
Long-time residents of Central Texas know that the sapping effect of drought is an inevitable part of weather extremes in this semiarid region of the state. The lakes are designed to be water reservoirs that fill up during wet years and are drawn down for uses downstream, such as drinking water for Austin and rice irrigation. Add evaporation, which can drink up to 4 feet a year, plus little or no rain runoff, and you get precipitous drops in lake levels.
The change may come as a shock to approximately 192,000 people who have moved to the Austin area since the last dry spell ended in 2000.
The chart below depicts an LCRA projection of the combined volume in lakes Buchanan and Travis for year-end 2006. The volume of water in the lakes is projected to drop to almost 1.1 million acre-feet — nearly half of the volume as when the lakes are full. The numbers below are in millions of acre-feet.
(Acre-foot: the amount of water required to cover an area of one acre to a depth of one foot. One acre-foot of water is equal to almost 326,000 gallons.) |
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Notes: Total combined capacity of lakes Travis and Buchanan is 2.017 million acre-feet. The projection is based on assumed "dry year" inflows, and recent demands. For example: Assumes rice irrigation demand of 105 percent of 2005, City of Austin and water customers demand is equal to drought year 2000, and power plant demands are 100 percent of 2004. |
Here are key projections for lake levels in the next few months:
- If the drought continues through Memorial Day, Lake Buchanan will drop 2.5 feet and Lake Travis more than 8 feet, according to the latest projections.
- By July 4, the level of Buchanan could lower by another 1.5 feet – to 1,009 feet above mean sea level (msl) – and by 7 feet at Travis – to 648 feet msl.
- Continuing to Labor Day, the level at Buchanan could decline by another 7 feet, to about 1,002, and at Travis by 3 feet, to about 645.
What does that mean in terms of water supply? The numbers show the extent of the lakes’ water storage capacity. At the levels projected for Labor Day, the combined storage of Buchanan and Travis would be more than 1.1 million acre-feet, or 365 billion gallons. For perspective, Austin’s municipal consumption in 2005 was 165,716 acre-feet or about 54 billion gallons.
Water quality
Water quality in the lakes may improve in the absence of runoff, which causes stormwater runoff pollution. Without nutrients to feed on, phytoplankton and algae blooms are less likely to occur, said LCRA aquatic scientist John Wedig.
The picture could change downstream of Austin. The Colorado River will be “extremely skinny” and more laden with nutrients and salt constituents for the winter months, Wedig said. The water quality will remain safe for swimming and fishing, but canoeists and kayakers will have to carry their crafts more than usual, Wedig said. These conditions will continue until LCRA begins releasing water for downstream irrigation of rice crops in early March.
Unless it rains downstream of Lake Travis, Matagorda Bay and estuaries will feel the effect of drought due to decreased inflow of fresh water. Salinity levels will go up but the adult fish of the winter season are not expected to suffer. If the drought continues through summer, juvenile fish may suffer the effects. “The bay has evolved to withstand droughts, so critters can survive,” Wedig said. “They may not thrive, but they will survive.”
Food sources
The harsh effects of drought are felt more keenly by those who depend exclusively on rainfall for their water supply. In some areas, the whole food chain is disturbed for lack of rain. Livestock have very little forage and farmers have produced little or no winter oats and hay for feed. If the drought continues, farmers may not plant crops simply because the soil is too dry to till.
Lack of rain will stunt growth of plants needed by many species such as white-tailed deer and birds, said Jarrod Depew, LCRA natural resources conservation coordinator. Wildlife will tend to congregate around remaining water sources, increasing the likelihood of disease. “If the current weather pattern holds, this spring could see decreased offspring production by many of our favorite bird and animal species,” Depew said.
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