COLLEGE STATION - Recommendations by the Texas Agricultural Extension Service are playing a key role in achieving a projected 20 percent decrease in water demand by agriculture in the Rio Grande Valley over the next 50 years, according to a recently-released study.
Extension experts are working at both ends of an irrigation problem finding ways to reduce water losses in an inefficient irrigation canal system, and proving methods for using less water on crop lands.
Agricultural irrigation is important to the Rio Grande Valley, which contains about 12 percent of the irrigated acres in the state and grows many of the winter vegetables produced in the United States.
“There is a lot of dryland cotton and sorghum, but just about everything that’s irrigated is done through canal systems in districts,” said Dr. Guy Fipps, Extension agricultural engineer.
Agricultural irrigation accounts for 90 percent of the water use in the Valley; average water use is about 1 million acre-feet per year, or more than 325 billion gallons of water.
Concrete canals and irrigation pipes are literally the lifeline to agriculture in that region. About 4,100 miles of canals and pipelines enough to stretch from Key West, Fla., to Seattle, Washington serve not only agriculture but municipal and industrial purposes as well.
However, the Valley is becoming thirstier and demanding more water the population is projected to more than double, growing from about 1.3 million people to 3.1 million by 2050, the Lower Rio Grande Valley Development Council reports.
According to the regional water plan submitted in February to the Texas Legislature, water districts and agricultural producers are being asked to stretch their water resources as far as possible.
“There is no other source of water for the cities, except for desalinization plants, which are very expensive,” Fipps said. “To meet future water demand, there’s going to have to be a transfer from agriculture to municipal and industrial use.”
In cooperation with Rio Grande Valley irrigation districts, Extension recently completed a study that identified 24 canal segments with a loss rate of about 10,532 acre-feet of water per year, or 3.4 billion gallons per year. The purpose of the study was to identify how much water could be saved and how it could be done.
“This is a good report,” said Ken Jones, executive director of the development council.
“I’m really pleased A&M was a key player in doing these projections related to irrigation districts.”
This work should improve the conveyance efficiency of the irrigation districts in the region, he said.
For example, by implementing surge irrigation and on-farm metering, both introduced by the Extension Service, the Brownsville irrigation district already has reduced water usage by 33 percent.
The study found the average conveyance system in the Valley had a overall efficiency of 64 percent (meaning about one-third of the water was lost), compared to a potential of 90 percent.
“You will never have 100 percent,” Fipps explained, “but 80 to 90 percent is achievable.”
The study found the major losses were caused by seepage as well as spills at the end of canals excess water that cannot be used at the end of the system.
“If you don’t manage the way the water is moved through the canal system, you end up with excess water in areas where you don’t need it or large spills,” Fipps said.
Also, the way canals are maintained eroded banks, cracked concrete or improper construction materials and methods can cause losses.
Besides making canal repairs, new technology for better management of the canal system, such as automatic gate controls, are remedies districts are studying seriously and in some cases, implementing.
The study also predicted greater savings by making changes at the farm level, by improving the management and using polypipe instead of ditches.
“We’re looking at the farmer better managing the water, controlling the flow, as well as adopting drip and sprinkler technology,” Fipps said.
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