Persistent drought in northwest Texas is leading farmers to pump more water from the Ogallala Aquifer, hastening the depletion of this crucial water supply.
Over the last decade, from 2004-2014, average underground water levels across the 16-county High Plains Underground Water Conservation District (HPWD) have dropped 8.83 feet (2.69 meters), with three counties seeing average declines of more than 15 feet, according to data compiled by the HPWD.
Some 77 percent of that depletion occurred during the last five years, when drought gripped the region.
Among the planet’s great underground water reserves, the Ogallala Aquifer underlies portions of eight U. S. states, spans some 175,000 square miles (453,250 square kilometers), and waters 27 percent of the nation’s irrigated cropland.
Decades of heavy pumping have caused widespread depletion of the Ogallala in its southernmost reaches, which get very little recharge from current rainfall. Since 1940, a volume of groundwater equivalent to two-thirds of the water held in Lake Erie has been depleted from the Ogallala.
For farmers in dry regions like northwest Texas, the ever-present possibility of drought creates tough choices about whether, when and what to plant, and, if drought persists through the growing season, how to make up the rainfall deficit to get their crops through to harvest. Lacking access to surface water, many farmers in the High Plains fill that soil-moisture gap by pumping more groundwater.
In 2012, the HPWD saw groundwater levels drop an average of 2.56 feet (0.78 meters), the largest annual decline recorded in the last quarter century.
This year, drought stalks the region again. Between Jan and April, total rainfall ranged from 0.1 inch to 0.7 inches across the district’s 7.6 million acres. The mid-July U. S. drought monitor map shows most of the panhandle under severe to exceptional drought conditions.
With natural rainfall adding so little moisture to the soil, farmers are likely again stepping up groundwater pumping to meet the water requirements of their cotton, corn and other crops.
After a four-year hiatus, officials of the HPWD, which is based in Lubbock, have decided to resume offering growers free assessments of their growing-season water use. A more precise measure of how much water is pumped during the typical 2,000-hour irrigation season provides crucial information to both growers and water managers.
The HPWD is more proactive than most western US groundwater authorities when it comes to education, incentivizing more efficient water use, and measuring and monitoring groundwater levels, but it too has had difficulty when it comes to regulation.
The district’s plan to enforce caps on groundwater pumping in order to drive up irrigation efficiency and slow the aquifer’s depletion has been delayed due to considerable resistance and threats of lawsuits from local farmers.
Nonetheless, more efficient irrigation practices and new water management strategies are helping some growers curb their groundwater pumping, saving water, energy and money – and perhaps extending the life of the Ogallala.
Currently, there are about 4,300 subsurface drip irrigation systems in the HPWD service area. Shifting from sprinkler to drip irrigation reduces water use by delivering more precise volumes of water directly to the roots of plants and reducing evaporation losses.
Some growers are also using sensors to monitor the soil moisture in their fields. This enables them to more accurately determine when and how much water to deliver to their crops – and can save up to 54,300 gallons per acre. Applied more widely across the panhandle, soil-moisture sensors to better schedule irrigations combined with more efficient irrigation systems could slow the Ogallala’s depletion.
One thing is clear: the future of the Texas panhandle depends on more commitment to conservation, to creative ways of adapting to drought, and to leaving enough water underground for generations yet to come.
Sandra Postel is director of the Global Water Policy Project, Freshwater Fellow of the National Geographic Society, and author of several books and numerous articles on global water issues. She is co-creator of Change the Course, the national freshwater conservation and restoration campaign being piloted in the Colorado River Basin.