PREDICTING SALINE GROUNDWATER OCCURRENCE IN WESTERN AND NORTHERN MISSOURI

Although much of Missouri has ample freshwater supplies, saline water in some deep aquifers limits groundwater extraction. A USGS study performed in 1985 defined a salinity line that denotes a transition from fresh to saline groundwater at depth and extends east to west across the state. This study also predicted that increased pumping rates in shallow wells might draw saline water upward. To investigate whether saline water has been drawn upward over the last 30 years, we acquired historical and current water quality data for 54 water supply wells in 20 counties that bordered the salinity line. Chloride and sulfate concentrations were analyzed as a function of time, elevation, and geologic formation using hypothesis tests, and maps of concentrations at different depths were created to visually identify any spatial patterns. Hypothesis testing showed no statistically significant changes in water quality with time, suggesting that the salinity line has remained approximately stationary since the initial USGS study. Spatial analysis of water quality suggests that major geologic deformation from the Ozark Uplift event may be responsible for higher salinity in some areas.