U.S. Water News Online
PUEBLO, Colo. -- Arkansas Valley farmers are dumping
anywhere from 3 to nearly 10 tons of salt on their fields every year
because their irrigation water is so salty, according to preliminary
research by the U.S. Geological Survey.
That has prompted researchers to look into the potential effects
of large municipal water projects that would take water from the
Arkansas River. Some fear such projects could concentrate salinity
and cause greater crop losses than area farmers are already
The Arkansas River in Colorado and Kansas is the most saline river
of its size in the country. Initial information from the USGS shows
that salinity can increase by 61,000 percent from the headwaters near
Leadville to the Colorado-Kansas border.
Average salinity ranges from 500 parts per million (ppm) of salts
at Pueblo to 3,500 ppm at the state line. Agricultural crop losses
can occur when levels climb above 700 ppm.
Decades of inefficient furrow irrigation, where the land is
swamped with water, contributed to high salt levels that have cut
crop yields since at least the 1970s. A study from that decade
estimated the high concentrations were costing valley farmers
millions of dollars a year.
Research by Colorado State University estimates that salts reduce
yields by up to 20 percent across the valley, said civil engineering
professor Tim Gates.
``What we are learning is that there is substantial promise for
improving those conditions,'' he said.
Downstream from La Junta, almost all of the water in the river is
from irrigation return flows, which builds greater salt
concentrations over time. In 1900, wells near the Colorado-Kansas
border had salt levels ranging from 291 to 962 ppm. Those same wells
in 1940 measured from 2,800 to 4,600 ppm.
Besides crop losses, high salt levels can cause gastrointestinal
distress in people and health problems in livestock and poultry.
``I believe there could be significant improvements,'' said Pat
Edelmann of the U.S. Geological Survey.
Colorado State's research is examining ways that improved
irrigation efficiency, canal lining canals, subsurface drains,
groundwater pumping patterns and changes in river flows can reduce
the salinity. The changes could boost farm yields, Gates said.
``Ultimately, the data and the modeling will provide tools to
allow key decision-makers in the valley to come up with alternatives
that will allow these problems to be mitigated and solved,'' he said.
Research at Colorado State's Arkansas Valley Research Center
extension has demonstrated that drip irrigation can bring the same
yields as furrow irrigation with one-sixth of the water for some
crops, reducing the amount of salts flowing back into the river, said
researcher Mike Bartolo.
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