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Rio Grande irrigation system challenges water engineer
Texas
Like the difference between shooting at a stationery target and a moving target--that's how Dr. Juan Enciso compares irrigating crops with water from an aquifer to irrigating crops from the ever-moving Rio Grande.
For the past year, Enciso has been the irrigation engineer at the Texas A&M University Agricultural Research and Extension Center at Weslaco in the Lower Rio Grande Valley. Before that, he served a similar five-year stint in El Paso.
His job involves conducting research and working with growers, irrigation districts and commodity groups to improve on-farm water use efficiency and crop productivity.
But the Valley's century-old irrigation system, which distributes water from the Rio Grande through a network of canals, has been more challenging than pumping underground water.
"The aquifer is always there," Enciso said. "You pump water when you need it. Water is carried through pipes, the amount is metered, and applications to crops are easily controlled. It's all a neat little package.
"But irrigating from the Rio Grande is much more challenging. There are more entities to deal with in getting water delivered, and it's a much less efficient system because of the many open, earth canals and ditches."
Despite the drought and limited water supplies, Enciso said when he arrived he was struck by the abundance of cheap water here compared to water in El Paso.
"It's the opposite of what you find here," he said. "In West Texas the cost of the limited water supply is high and there's plenty of inexpensive land. Here, water is more plentiful and less costly, but land is limited and more expensive."
The challenge for West Texas growers, Enciso said, is to maximize net return per unit of water applied. In contrast, Valley growers must maximize net return per unit of land.
Enciso is impressed with the ability of Valley growers to adapt to the always-changing conditions of producing a crop. But during drought, growers will not switch to more efficient water technologies unless the expense can be justified over a long period of time, he said.
"If a dry period only occurs two out of every 10 years, growers won't make the change to these technologies because they are more expensive, and they require higher maintenance and more intensive management, more knowledge," he said.
Instead, growers alter their farming practices, including planting more drought-resistant crops, using shorter furrows and tightening irrigation schedules.
"That's why agriculture has endured and succeeded here," Enciso said. "They adapt to the situation and condition whether it be the market or natural conditions."
Still, Enciso tests and compares different irrigation technologies of drip, central pivot and flood irrigation to determine yield response of the major crops grown here. This information can be used today, but will be invaluable if water supplies dwindle again.
"The variety of crops grown here--sugarcane, cotton, vegetables, citrus, corn, sorghum and others--is another impressive aspect of agriculture here that keeps this industry viable," he said. "The diversity protects the overall agriculture economy should any one crop fail."
The improvements to the Valley's irrigation infrastructure, including installing new pumping units, lining earth canals, and converting canals to pipe and concrete pipes to plastic, are important to the growth of the entire area since municipalities and industry get their water from the same system as growers do, Enciso said.
"We need to get rid of the inefficient earth ditches and canals, better monitor water flows at the farm level and monitor water quality to reduce the discharge of polluted water to the Gulf," he said.
Enciso predicts automated greenhouses for the production of vegetables and other high value crops in the future to better control growing conditions.
"But for now," he said, "if the economies are right, we'll probably start to see more use of pressurized water systems here in the Valley, such as drip and central pivot systems. And flood irrigators will level land more often to improve water distribution and use more poly-pipe, or gated soft-plastic pipes instead of the earth ditches and siphon hoses used now."
Date: 9/23/04
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