Upper Arkansas River Mineralization Study

In response to findings of uranium exceeding the maximum contaminant level (MCL) in public water supply systems, a study was requested by state agencies of Kansas on the current state of groundwaters in the HPA in the river corridor, with a focus on uranium, radioactivity, and other elements for which MCLs exist. The KGS prepared a scope of work for the Kansas Water Office for a two-year study that included eight objectives, and this project was funded under the Kansas Water Plan in 2019.

Study Objectives:

  1. Determine the current distribution of salinity and uranium, selenium, and arsenic concentrations and gross alpha and gross beta radioactivity in groundwater of the High Plains aquifer (HPA) (including the alluvial aquifer) in the upper Arkansas River corridor from the state line with Colorado to Dodge City.
  2. Compare the current chemical concentration distributions with past distribution data to determine concentration differences and spatial and temporal changes.
  3. Determine the current input of chemical concentrations and loads in Arkansas River water in the river channel and major irrigation canals.
  4. Assess the geographic factors controlling the chemical concentration distributions and changes in time, including distance from the Arkansas River channel and major irrigation canals, and area underlying historic and current ditch irrigation areas.
  5. Assess the vertical lithologic controls on the chemical concentration distributions, including depth to sampling intervals and the distribution of thick clay layers based on lithologic information in well logs.
  6. Assess hydrogeochemical factors controlling the chemical concentration distributions, including precipitation of sulfate minerals in irrigated soils and adsorption of uranium, selenium, and arsenic on sediment surfaces during transport in groundwater flow, both of which can alter uranium/sulfate ratios in the groundwater.
  7. Estimate the future accumulation and redistribution of salinity, uranium, and other contaminants of concern in the study area as implied by the data and information obtained from the above objectives.
  8. Communicate the results of the study to state and local agencies and the public.