Got Water Solutions?
Question: What do Kerrville, San Antonio, and Wimberley, Texas have in common?
Answer: All three of them rely on groundwater as their primary source of drinking water.
Kerrville, Texas has a population of more than 21,000 and relies on groundwater to meet its residential, agricultural and industrial needs. In cohort with the Upper Guadalupe River Authority, the City of Kerrville operates an Aquifer Storage and Recovery system that draws water from the Guadalupe River during the wet season, treats the water, and injects it into the underlying Trinity Aquifer for storage. During the dry season, the city recovers, retreats, and uses the stored water. This system has been in place since 1992 and when combined with effective conservation measures and land use regulation, has proven capable of meeting the local needs while reducing the load on the Trinity Aquifer. The situation is not static, and more will have to be done in the future as the city grows, but for now, ASR is making a positive difference.
To our south is that quaint little village we call San Antonio — population 1,144,646 (and growing). They rely entirely on ground water for all their fresh water needs. In June 2004, the San Antonio Water System (SAWS) Aquifer Storage and Recovery Project (ASR) went online. Located in south Bexar County, SAWS’ ASR uses relatively new technology to store excess Edwards Aquifer water during rainy times for use during dry south Texas summers. When both phases of the project are completed, this ASR project will be the second largest in the country. Phase One of SAWS’ ASR began operations in June 2004. It also includes San Antonio’s first drinking water treatment plant that will eventually serve as the hub for receiving additional water supplies in the future. Initially, it will store a little more than 3.5 billion gallons of water. Phase Two of the ASR project is expected to be completed in 2005, and will double the storage capacity to nearly 7.5 billion gallons. The cost of the project? About $190 million. Cost per capita? About $166.00. Cost per gallon? About two and one-half cents. To quote SAWS: “While ASR technology is a proven method of storing water underground, SAWS has enlisted the help of some of the world’s leading ASR experts on this project. Water will be pumped from the Edwards Aquifer during peak periods of rainfall and stored in the Carrizo Aquifer in south Bexar County. Later, during the hot, dry months, we’ll pump the drinking water back into the existing distribution system to help meet summer water demands. Although SAWS purchased 3,200 acres for this project, most of the land is being leased back to farmers and ranchers so they can continue their work. We’re also proactively working to make sure the project doesn’t impact neighboring well owners in Bexar, Wilson, and Atascosa Counties.”
The Hays Trinity Groundwater Conservation District’s Draft Management Plan envisions a constancy of reaction to water shortage problems after the problems occur or at best merely checks the pace of the inevitable problems — after all, regulation is about reaction, not proaction. The plan does contain two guiding principles that envision proactivity: rain water collection and artificial recharge.
Rain water collection seems viable so long as we have a reasonable amount of precipitation over the area. In an extended drought, those who find themselves dependent on rain water may have to haul-in potable water when their tanks run dry. This approach is a house-by-house solution that leaves the decision in the hands of the homeowners. Unless every home in the valley installs and relies on rain water collection, I’m just not convinced that it will make enough difference to save the Trinity.
Artificial recharge, on the other hand, seems to offer long-term hope for rescuing the Trinity from its otherwise inevitable deathbed.
Looking at our situation in Woodcreek Phase II, I know that we have dry creek beds that converge on Cypress Creek. When we get heavy rains, these dry creek beds turn to torrents that contribute considerable flood water to Cypress Creek and ultimately the Blanco River. If a hydrological examination of the structures beneath these dry creek beds meets the criteria, then there may be potential for enhanced natural recharge. There are many more dry creek beds similar to ours throughout the district that might pass hydrological examination. A series of storm water retention levees and dams constructed along key dry creek beds throughout the district (such as our run of the dry Cypress) where these streams cross the Trinity Aquifer recharge zone could operate to impound significant amounts of storm runoff thereby enhancing local natural recharge of the aquifer. Most of the recharge to the Trinity appears to occur during heavy rains. As it stands now, these heavy rains lead to streamflows that exceed the maximum possible recharge rate of the area over the recharge zone. In the process, relatively little of the stormwater runoff actually contributes to recharge, while most of the rain contributes to downstream flooding instead of aquifer recharge. We need to save this water while we have it to save.
If we could slow the flow of the stormwater runoff by erecting a series of catchment levees and dams along key creek beds, then we could increase the amount of time that the water remains over the recharge zone, and that should contribute far more local recharge to the aquifer without substantially impacting stream habitats. To increase the effectiveness of these catchment basins, it may be necessary to bore seep holes to enhance the rate of recharge. This approach would involve natural recharge and should result in no changes in water quality in the Trinity. These catchment sites would likely hold the water for relatively brief periods as the impounded water seeps or evaporates. The added benefit would be the mitigation in the amount of floodwater that would otherwise contribute to downstream flooding.
This approach is not new. You will find countless examples of this technique being used effectively in Texas and across the nation.
{Editor’s Note: Our thanks to Woodcreek North resident Tom Davis for researching and writing this article.}