DROUGHT:

The future of Texas' groundwater supply may be precarious, experts say

The city of Vernon, in north-central Texas, lies right on the path of the old Western Trail, where cowboys once drove their cattle northward to Nebraska. The city of 11,005 has suffered through a drought that has parched most of Texas for the last four years.

Residents are only allowed to water their lawns every other day, and City Manager Mitch Grant says homeowners may adopt "zero-scape" landscaping that uses native plants, which are less water intensive. Local officials worry what it will mean for Vernon's water supply if the drought continues. In the past few years, the city has had to drill additional wells to meet their water needs.

"I think our citizens go above and beyond when it comes to saving water," Grant said.

Like many smaller communities in Texas, Vernon gets all of its water from an aquifer beneath it. If their groundwater ever runs out, they would have few other feasible options. The nearest river is less than 20 miles away, but its water is owned by Oklahoma.

Though Vernon's residents dread using recycled water from a wastewater plant for their drinking water -- like residents of Wichita Falls (ClimateWire, July 11), about 50 miles away -- Grant said the city doesn't have the infrastructure for even that extreme option. Vernon's officials are certainly not alone in deliberating where tomorrow's water might come from. Similar conversations are happening in municipalities across the state.

80-year drop in groundwater levels

Texas' dependence on groundwater concerns some hydrology experts. About 60 percent of all of Texas' water comes from aquifers, and about 40 percent of the water used by municipalities is groundwater, making the state the second biggest user of groundwater in the country, according to the Texas Water Development Board (TWDB).

They say Texans are pumping water at unsustainable levels, and the groundwater supply seems unlikely to meet future demand. No one is entirely sure of how much groundwater is available. However, researchers do know that there is a lot less groundwater than there used to be. A recent study of Texas groundwater records dating back to the 1930s shows a steady decline in groundwater levels in the past 80 years.

The study, published by researchers at Texas A&M AgriLife Research and Extension Center in the journal Science of the Total Environment, found that in the 1930s the statewide median water level was 14 meters (nearly 46 feet) from the surface of the land. But by the 2000s, the median average was 36 meters (118 feet) from the surface.

Between 1995 and 2005, water levels had decreased by a third in the nine major and 21 minor aquifers across Texas, and there were noticeable declines in 42 percent of the wells, according to the study's authors, Sriroop Chaudhuri and Srinivasulu Ale. Their study was the first to take a panoramic look at the state's groundwater levels; previous studies had focused on specific aquifers.

While lack of rain from drought has brought down water levels, overdrawing water has been the leading cause of groundwater level declines in the state, said Robert Mace, the deputy executive administrator of the water science and conservation department of the Texas Water Development Board.

Rapidly drawing down the Ogallala

The biggest demands for water are on the Ogallala Aquifer in the Texas Panhandle, which feeds much of Texas' agriculture and by itself is the source of 40 percent of the state's total water supply. "They are pumping at six times the rate the water is coming in, so what we see is a year-on-year decline in water level," Mace said.

Other factors also may be bringing the water level down. The Trinity Aquifer beneath the Dallas/Fort Worth area has declined rapidly, in some places by as much as 1,000 feet. Ale hypothesized that the process of urbanization could be partly to blame because increasing paved roads and parking lots could reduce how much water seeps back into the ground.

Both Mace and Ale recommended that municipalities adopt water-saving measures like creating rainwater catchment areas or using more energy efficient plumbing fixtures to reduce water use, features that are already being implemented throughout Texas.

Some places have already had to take drastic measures to handle the drought. Wichita Falls relies entirely on treated wastewater for its drinking water because of the severity of the drought there. Although the city sits directly above Seymour, the shallow aquifer did not provide enough water to supply the population, according to Mace.

A recent analysis of historical data from the U.S. Geological Survey showed that over the past 61 years, groundwater levels around much of the country have declined significantly, according to a study by the Columbia Water Center, part of the Earth Institute at Columbia University.

Declining groundwater is problematic because Americans get more than 40 percent of their drinking water from groundwater, demand is likely to increase as the U.S. population grows and the surface water sources become less reliable, according to the study that was published last March.

How quickly an aquifer can replenish depends on a number of different factors, including the components of the soil, the weather patterns in the region, the topography of the land above the aquifer and how the land is being used, according to Tess Russo, a postdoctoral fellow at the Earth Institute at Columbia University and lead author of the study.

Groundwater and climate change

Drought conditions can not only reduce available water in the aquifers, the lack of rain can make populations more dependent on groundwater reserves as surface water levels decrease. These conditions could only be made worse by climate change. As the global temperature has become hotter and droughts have become longer, the risks of further reduction in groundwater could be increasing, Russo said.

Her research found a correlation between long-term climate patterns and groundwater levels in deep wells, where wetter periods had groundwater recovery. On the other hand, some wells showed little or no variation in relation to either local precipitation or longer weather trends.

Russo said more research was needed to fully understand just how much groundwater is available for consumption.

"The main thing that's missing from the study is we are only looking at the change in water level, we don't look at the volume of that water that is coming out," Russo said.

Not all aquifers across the country provide the same amount of water, so comparisons between formations can be misleading, Russo said. While the waters levels at Ogallala and aquifers along the East Coast might decrease at the same rate, the total volume of water lost is not the same, she said.

While a lot of attention has focused on groundwater depletion in the western United States, Russo said she was surprised by the groundwater declines in southern Mississippi and in aquifers along the East Coast.

There are a few hopeful signs for Texas. The losses in groundwater levels appear to be declining in some parts of the state over the past decade. Mace, the Texas state water official, attributes the change to state and federal mandates that required the use of more efficient plumbing fixtures in municipalities and sprinkler-style irrigation on farmland.

In Vernon, Grant, the city manager, said increased rainfall this year has helped replenish the Seymour's reserves, but he was cautious about making predictions about the future of the city's water.

"I don't know if we are out of the drought, it could go on for another 10 years," he said. "But we've had more rain than we've had in the past four years."

Twitter: @nhheikkinen | Email: nheikkinen@eenews.net

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