Irrigation water resources in the Texas Southern Plains are diminishing at the same time the number of irrigation systems and wells are increasing, putting even greater pressure on the aquifer.
“The number of active irrigation wells has increased from 3,500 to almost 6,000 in the district,” says Jason Coleman, with the South Plains Underground Water District.
Coleman, addressing the recent South Plains Ag Conference and Trade Show in Brownfield, said the area has seen a significant depletion in the aquifer in the last 15 years. During that same time, the number of center pivot irrigation units has increased.
Based on surveys conducted every five years, Coleman noted the district tallied 701 center pivot units in 1993. By 1998, that number had almost doubled, up to 1,392 units. By 2003, producers added only a few more units to 1,406. The number dropped to 1,394 by 2008, but inched back up to 1,413 this year.
The number of wells required to supply those center pivot irrigation systems is also rising. “In November, 2012, we had 11 quarter sections that had 10 or more irrigation wells in place,” Coleman said.
The current number of irrigation systems in the district, 1,413, is served by 5,978 irrigation wells, Coleman said. “We are averaging 4.23 wells for each center pivot system.”
Many of those wells produce less than 300 gallons of water per minute. And well yields continue to diminish. He said well yield potential depends on several factors, including saturation thickness and conductivity. Saturated thickness is a telling benchmark.
“As more groundwater is pumped, water levels decline and saturated thickness decreases,” he said. “This results in additional declines in production. Adding more wells may speed the decline in water levels and may also deplete larger segments of the aquifer.”
The problem will only get worse in coming years, he said. “Even with 40 feet of water saturation, many wells will produce less than 150 gallons per minute.”
Coleman said the district has 160,000 irrigated acres and producers would need wells with 480 gallons per minute capacity to provide 3 gallons per minute per acre. Currently, that’s from 4,000 wells. In the future, to provide adequate water for irrigation, the district may need “up to 9,500 wells.”
And more wells will mean a more rapid decrease in the aquifer.