Design in a Time of Uncertainty
By Rives Taylor, Principal, Global Resilience Research Lead
The state of Texas is trying to solve future water supply problems with yesterday’s solutions.
Innovative approaches to Texas’s future water security represent only a small portion of strategies presented in the current State Water Plan. Over 50% of future water supply projects intended to provide for population growth and drought resilience come from new reservoirs, water transmission projects, and changes in agriculture.
What is wrong with this picture?
Texas currently has approximately 200 major reservoirs built for water supply; many were built after the drought of record in the 1950s. A large problem with the strategy of reservoirs, particularly in arid areas, is water loss due to evaporation. Most of the major reservoirs west of Interstate 35, the interestate highway that stretches from Laredo to Dallas and north past the Texas-Oklahoma border, are less than 60% full.
Additionally, dam construction on Texas rivers has impacted the flow of nutrients to the Gulf of Mexico estuaries and put coastal fishery populations on a diet.
Despite all of the negative impacts tolerated for water supply reservoirs, they have not provided water security in western Texas when challenged by drought. What leads the proponents of major new reservoirs to believe that future precipitation and evaporation patterns will be sufficient to fill these reservoirs for supply?
Surface water is only one part of our water supply. Many public water providers and irrigators tap groundwater sources. In most areas with high demand, groundwater use has been unsustainable. This is particularly true in the Texas Panhandle where the Ogallala Aquifer shows very little recharge and in Southeast Texas where the Gulf Coast Aquifer is situated in sediments subject to subsidence.
One of the contributors to our water crises is per capita demand. The U.S. has the highest per capita water use in the world. It's hard to justify a Texan consuming twice as much water as a resident of Spain, France or England, especially when one of the biggest municipal uses in the summertime is watering lawns.
To approach the problem in an innovative way, Texans need to conserve our water supply. Almost every future water project will provide water at a higher cost than existing strategies. An infrastructure that leaks water at a rate of several thousand gallons per mile of water main per day should be updated. And, having a green lawn is not a right. Community perception needs to be changed to stop the wasting of water on thirsty, non-drought tolerant vegetation, such as the ever-popular St. Augustine grass.
Secondly, we should begin practicing water stewardship and reuse of treated wastewater.
I know some of my environmental colleagues will be fearful of depleting environmental flows, but there are benefits for sustainability. If we treat water as a recyclable resource, then we are more likely to avoid contamination that will reduce our ability to reuse it. Practicing stewardship of water that will be reused should lead to protecting consumers from contamination by unregulated substances, such as pharmaceuticals and personal care products, which are becoming more common in our rivers and reservoirs. We should not be afraid of toilet to tap if the water is properly managed.
Thirdly, when there is a justification for water storage, it should be stored underground if possible. Aquifer storage eliminates evaporative loss. The reservoirs built since the drought of record lose more than 4 million acre feet each year due to evaporation. San Antonio and several other communities have demonstrated the practicality of underground reservoirs.
Finally, if demand outstrips supply after all of the above strategies are implemented and new water must be found, let’s sustainably and cost effectively utilize abundant brackish groundwater. A lot of water-poor communities are considering this solution and a Texas Legislative committee will study its potential. Desalination technology has evolved and increased use is likely to drive improvements and cost reductions.
So how likely are we to achieve a drought resistant water supply?
If we repair the distribution infrastructure, it's likely that water available for municipal users will increase by 20%. Ending compulsive lawn watering practices could conserve an additional 30 to 40% of municipal water during the summertime months. This should permit us to take a thoughtful approach to agricultural water conservation. If we shift to aquifer storage, we can avoid evaporation of millions of acre feet of water and create a more drought secure water supply. Communities affected by failed reservoirs will be seeking new water sources and are turning to studies of desalination of brackish groundwater resources.
There are innovative solutions among the options presented in our State Water Plan, but we need to be watchful to avoid investing in yesterday’s answers to tomorrow’s problems.