From The Pueblo Chieftain (Chris Woodka):
The U.S. Geological Survey monitors the entire Arkansas River in Colorado from Leadville to the Kansas state line through a series of stream gauges and testing stations. The Lower Arkansas Valley Water Conservancy District board voted [May 18] to continue funding of a water quality station below John Martin Reservoir and seven stream gauge stations for $31,500. The USGS picks up $18,100 of the cost.
The major water quality issue on the Arkansas River remains salinity, which increases from less than 100 parts per million at Granite, near the headwaters in Lake County, to more than 3,000 ppm at the state line, said David Mau of the Pueblo USGS office. “We also have 120 wells to monitor groundwater levels and look at changes in the aquifer,” Mau said. “That gives us information as there are changes in water and land use.”
More Arkansas River basin coverage here.