News Release, Kansas Geological Survey, Nov. 9, 2000
That contamination is caused by high levels of salinity in the river as it enters Kansas from eastern Colorado, said Don Whittemore, a geohydrologist at the Survey.
Jill Whitmer, a graduate student in the KU geology department, Whittemore, and KU geology professor Gwendolyn Macpherson will present the results of their research at the annual meeting of the Geological Society of America in Reno, Nevada, this week.
Whitmer and Whittemore collected samples of water from the river and from several wells at three sites in the river valley in western Kansas in 1999. Samples were taken from wells in Deerfield (in Kearny County), near Garden City, and near Dodge City. The water samples were then analyzed at the Survey and the KU plasma analytical lab at the KU geology department.
The results of these and other analyses showed that total dissolved solids in the river water, a general indicator of the water quality, average about 3000 parts per million. The maximum recommended level of total dissolved solids in drinking water is 500 parts per million. Sulfates, from naturally occurring minerals and salts, make up a large portion of those dissolved solids. Levels of selenium and uranium, also naturally occurring elements, are also elevated in the river. Whitmer's graduate research focused particularly on the movement of selenium and uranium in the groundwater.
Researchers say that most of the salinity in the river comes from eastern Colorado, where water is diverted by ditches from the river and used for irrigation. Some of that water evaporates, concentrating the minerals already present in the water. Part of that highly mineralized water runs off of fields and returns to the river, producing high levels of salinity in the Arkansas.
The amount of water in the river has been a concern because the Arkansas was dry in much of western Kansas through much of the 1980s and early 1990s. The Arkansas River was also the subject of an ongoing lawsuit between Kansas and Colorado.
Water has generally been more plentiful in the river during the past few years. However, high salinity levels are an issue because water from the river seeps into the alluvial aquifer--water-bearing sand and gravels along the river. Some of the mineralized water also moves into the High Plains aquifer (which includes the Ogallala aquifer). Water levels in the High Plains aquifer have been lowered by pumping in the past few decades. Saline water from the river is now moving into the alluvial aquifer and the High Plains aquifer, replacing the high-quality water that was pumped out. The water also contains elevated levels of selenium and uranium.
"Saline water is contaminating the Ark River valley," said Whittemore. "Salinity levels are not so high that they will stop the use of water for irrigation, but they could cause problems for other uses, such as manufacturing and domestic use."
The research is part of a broader study of the Upper Arkansas River valley, funded in part by the Kansas Water Plan.