Jan 02, 2008

University Study Examines Salinity, Water Tables in Arkansas Valley

Colorado State University study looks at the effects of large-scale water changes in the Arkansas Valley

A study that started with the intentions of determining the impact of irrigation on land and water farm-by-farm has grown into a potential means for predicting the effect of large-scale water changes in the Arkansas Valley, the Pueblo Chieftain reported.
In 1999, Colorado State University professor Tim Gates and his colleagues started looking at 125,000 acres of farmland above the John Martin Reservoir, taking field measurements to see how irrigation affected water tables and the salinity of the water. And in 2002, another 136,000 acres below John Martin Reservoir were added.
The study has given researchers the most complete data ever collected in terms of irrigation water use in the Arkansas Valley and an understanding of how irrigation changes the environment, the newspaper reported.
For farmers involved in the project, there is an opportunity to learn how to apply water more scientifically. The researchers have now branched out from simply studying the farms to looking at canal systems. One of the most significant parts of the study has been looking at how best to apply polyacrylamide (PAM) as a way to seal canals.
But larger benefits to the valley exist. During the study, Gates discovered the data could be compiled to model how large-scale changes in water use could affect water availability and quality for the entire area downstream of Pueblo Dam.
"What we're seeing is the same strategies that boost agricultural productivity will improve water quality, and that's not always the case," Gates recently told the Southeastern Colorado Water Conservancy District.
Unlike other water conservation strategies, lowering water tables in the valley could produce more water for beneficial use—potentially more than the city or Pueblo, Colo., uses each year.
During the process, the water quality of the Arkansas River would improve because salinity, selenium and metals would be reduced by 30 to 40%.
Seepage from canals and excessive runoff from fields contribute to waterlogging or water tables that are too high. This in turn leaches more salt into the soil and water. Productivity could be improved by 10 to 20% with better irrigation practices, the Pueblo Chieftain reported.
Gates intends to add the area around Pueblo and Fountain Creek, Colo., to existing studies to get a complete picture of the valley, according to the newspaper. The upper reach of the river is more influenced by urban factors, but needs to be considered to get a holistic picture, Gates explained.
"We're developing a decision-support system that will allow us to understand how to operate Pueblo Reservoir and John Martin Reservoir to store the water and release it in a timely manner that would not violate the Arkansas River Compact," Gates said.