 Photograph by Chase A. Fountain, Texas Parks and Wildlife Department Researched & written by Paul Robbins, May 7, 2024 Part 1 – Six Steps to Year Zero
This is the first of a two-part series on potential, and likely, water shortages that will afflict Austin in the coming decades, and how it will impact the city’s future. Part 1 looks at where are we were in April 2024 with the current drought, and what our future looks like with climate heating and a worst-case scenario. This future worst case is projected in six layers or steps to show the approximate year Austin reaches “Year Zero” with empty lakes if everything goes wrong at the same time, and gives a few examples of other places where it has gone wrong. Obviously, the Lakes have not gone dry yet. But when plausible and likely climate and consumption patterns collide with population growth, the prospect of dry lakes is no longer science fiction. Note to readers: The year 2023 is used as the baseline, but data in this analysis was sourced from the most current years available. These included 2022, 2023, and 2024. The Texas Weather: Where Erratic is “Normal” Texans are privileged to reside in one of the most temperamental regions of the U.S. The state is blessed with hurricanes, tornadoes, numerous lightning bursts, hail, debilitating heat, and even fierce blizzards in the northern part. These extremes have contributed to the character of the people, and by extension, the state’s history, in several major ways, including the massive infrastructure needed for its water systems. There is only one (partially) natural lake in the entire state. The other 196 major stationary “lakes” over 5,000 acre-feet in size are actually man-made reservoirs largely built to slake the state’s thirst. (An acre-foot would have supplied 5 Austin homes a year in 2023.) The collective area of these lakes is about 150% larger than Travis County. There is no other state in the country that has this much land covered with inland water bodies. The Central Texas Highland Lakes are a chain of six reservoirs along the Colorado River created for reliable water supplies in dry times, flood control in wet times, hydroelectricity, and irrigation for agriculture in counties near the Gulf Coast. When the two lakes used for reliable municipal water supplies were commissioned, Lake Buchanan (1937) and Lake Travis (1942), they were viewed by most Central Texas residents as virtually inexhaustible. But a lot can happen in 90 years: an almost 12-fold increase in the population of Central Texas; the growth of major industry; way more water-cooled power plants; sediment deposits that diminish the Lakes’ storage capacity, severe droughts, and increasing severity of drought caused by global warming. On April 17, 2024, the Highland Lakes that store Austin’s water supply were only 42% full. There have only been 4 periods since 1941 when they have been lower. In an attempt to look at the worst case, this analysis attempts to layer on the challenges facing Central Texas water supplies caused by drought, global warming, increasing population, and sedimentation. The Real Drought of Record Of all the extreme weather conditions that afflict Texas, droughts are the most common. According to the NOAA Storm Events database, in 2023, 23% of all drought incidents in the U.S. occurred in Texas. When water supply planners and utilities in Austin and Texas plan for emergency supplies, they generally refer to the state’s “drought of record,” which occurred between 1951 to 1956. In this time period, Central Texas experienced a 25% decrease in precipitation compared to recent history.  Water Shortage Step 1: The Historical Drought of Record However, Texas weather data only goes back to 1895. When scientists used observations from tree rings to reconstruct climate history going back to 1500, they discovered droughts in Central Texas were much worse using a similar metric that measures precipitation and temperature together, the “Palmer Drought Severity Index.” The worst, from 1712 to 1717, scored an Index rating 35% worse than the 1950s drought of record.  Water Shortage Step 2: Using calculations derived from tree rings, scientists have identified 3 extended droughts in Central Texas worse than the one in the 1950s. Things Can Always Get Worse: Drought with Global Warming As global warming caused by fossil fuel emissions intensifies, it poses an ironic challenge for Texas. How do you define the new normal in a state where being normal is being erratic, and where the landscape is already scarred by weather hazards? Austin’s water utility, Austin Water, currently has contracts with the University of Texas Jackson School of Geosciences to assess how climate change will impact the temperature and rainfall in the not-too-distant future. Though no final conclusions have been made yet, the draft report’s predictions are staggering. The study explored three different internationally-recognized carbon emission scenarios. These have various emission levels depending on the year as described in this chart.
 Water Shortage Step 3: Computer simulations for two 20-year periods show dramatic decreases in average monthly Colorado River flows at Austin. Water availability adjusted for the droughts of the 1950s and the 1700s and global warming could be cut yet again by another 13% to 25%. Sedimentation If drought and excessive demand are not enough to threaten water supplies, there is the phenomenon of erosion or sedimentation. All water bodies, natural and man-made, are subject to loss of capacity from erosion as soil is swept into them by rainfall and wind. This is often compounded by runoff from human development. Lakes Buchanan and Travis have lost 11% and 1.5% of their original capacity, respectively, since they were built. And there are those who have it worse. Lake Steinhagen in East Texas has lost 35% of its volume since it was completed in 1951. Reservoirs can theoretically have the silt dredged and removed to restore their original capacity. However, industrial dredging on this scale is humongously expensive. To give an example of the high cost of dredging, a study for restoring Lake Buchanan in 1990, updated to 2024 dollars, was approximately 13 times the cost per acre-foot that LCRA charged for water. While continued sedimentation of the Highland Lakes will be minor from one year to the next, it will also be cumulative and unrelenting. By 2050, it will represent an additional 20,400 acre-feet of water storage loss, equivalent to almost 93,000 Austin homes at 2023 levels of consumption.  Water Shortage Step 4: Sedimentation in the Highland Lakes is expected to lose enough water supply to provide for almost 93,000 Austin homes by 2050. Increasing Demand: Too Many People Using Too Much Water In 1956, the Austin business community began an aggressive campaign to recruit businesses to the city, and has not stopped to this day. The campaign’s achievements have been so successful that, according to the U.S. Census in 2023, Austin was the 10th largest city in the country. In 2023, Austin’s water utility served 1,146,000 people in a service territory of more than 548 square miles. By 2030, it is predicted to rise to 1.3 million; by 2050, almost 1.7 million, and by 2100, 2.8 million. Based on this growth rate, municipal use of the Highland Lakes for Central Texas cities (not just Austin) will almost triple between 2023 and 2080. Even if all other uses, such as industrial and recreational, remain static, total consumption will more than double. And this estimation is conservative. If water consumption increases at the rate of population growth in Central Texas, total consumption will more than quadruple.  Water Shortage Step 5: Predicted rising water demand of the Highland Lakes Stagnating Water Conservation Effects At the same time, use per person is not falling. Austin Water began an intense water conservation effort in 2007, and saw its per-person water use plummet from 190 gallons per capita per day to as low as 120 gallons per capita per day in 2019. But the progress has flattened and consumption has even buoyed up slightly from this low-water mark.  Water Shortage Step 6: Water consumption fell dramatically after more water conservation programs were implemented in 2007, but this progress has stalled in recent years. In fact, this stubborn per capita usage, combined with low rainfall in 2022, sent Austin’s total water consumption to a record high of 174,000 acre-feet. And if Everything Goes Wrong… When all these water supply stressors are layered over each other, it shows just how fragile the future of Central Texas could be. 
This worst-case drought and global warming scenario (with moderate consumption) shows the Highland Lakes at only 4% of their full (2 million acre-feet) capacity in 2023 and running dry between 2030 and 2040. Some of this residual water would require pumps to remove because the lake levels would be too low for water to flow with gravity. It Can’t Happen Here (But It Happened There) Skeptics of these dire warnings will say it is highly improbable that all these plagues will occur at once – that the odds are so low as to be minuscule. But a relatively short distance northwest of Lake Buchanan, four Texas reservoirs in the Upper Colorado River Basin have crashed several times, and for lengthy periods of time, because of drought and overuse.  The E.V Spence reservoir, 145 miles from Buchanan, was completed in 1969. It has never held close to its designed volume, and crashed during a lengthy period in the last decade.  Lake J.B. Thomas, 210 miles from Buchanan, was commissioned in 1952. It has not been full since about 1965, and has crashed at least twice.  Lake O.C. Fisher near San Angelo, 130 miles from Buchanan, has only filled to capacity once since it was completed in 1952, and has been empty or near empty during many years of its existence.  Twin Butte Reservoir, also near San Angelo, was completed in 1963. It has not been at capacity since the late 1970s, and has been empty or near empty for a considerable time period since 2000. Skeptics of an Austin water shortage will point out that these reservoirs are in a more arid climate. But that is the whole point of this article: calculating how much water in Central Texas will be available during the plagues of drought, global warming, and over consumption. In fact, the Austin Water utility recently conducted its own simulations with advanced global warming scenarios, indicating a 6% chance of dry lakes under extreme conditions in 2030, rising to a 63% chance by 2080. This did not include using the extreme drought history from the 1700s.  Recent simulations by Austin Water showing chance of empty Highland Lakes with advanced global warming. Of course, long before the Highland Lakes dipped anywhere close to these dangerous levels, massive and rigid water conservation measures would be enforced. However, as the region’s population increases rapidly and rabidly, even these drastic measures will become less effective at providing a secure supply.
Calculating how much water Central Texas will need during the worst-case plagues of drought, global warming, and over consumption is no longer science fiction. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * This is the first of a two-part feature on potential, and likely, water shortages that will afflict Central Texas in the coming decades. Next: Part 2 – The Malpractice of Ignoring Aggressive Water Conservation. Research for this story was funded with a grant from the Save Our Springs Alliance. Stay tuned. Comments are closed.
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