A GEOCHEMICAL INVESTIGATION OF THE BIG FOUR SPRINGS REGION IN SOUTHERN MISSOURI

The Big Four Springs Region hosts four major first-order magnitude springs in Missouri and Arkansas. These springs are Big Spring (Carter County, MO), Greer Spring (Oregon County, MO), Mammoth Spring (Fulton County, AR), and Hodgson Mill Spring (Ozark County, MO). Based on historic dye traces, these springs drain an area of approximately 1500 square miles and collectively discharge an average of 780 million gallons of water per day. The Big Four Springs issue from Ordovician and Cambrian dolomite formations, which make up the majority of rocks exposed throughout south-central Missouri and north-central Arkansas.

The objectives of this study were to (1) establish the geochemical characteristics of the Big Four Springs, providing insight into water-quality conditions. (2) Investigate calcite and dolomite saturation of the Big Four Springs to determine whether the spring waters are related to tufa deposits in the southernmost region of the study area.

Results of the geochemical investigation of the Big Four Springs are presented. The results show the geochemical trends of each spring from the sampling period beginning in June through October. Ten sampling events took place during the sampling period. The results were useful to characterize each spring using geochemical software (Phreeqc Version 3 and GW_Chart). Analyses of the dissolved solutes indicate that the water issuing from the study area is predominantly magnesium-bicarbonate water type. The data available for each spring include temperature, conductivity, pH, and alkalinity, and lab results for Chloride, Sulfate, Nitrogen, Ca, Fe, Mg, Ba, Na, and K. This study has established a baseline geochemical data set for the Big Four Springs. These major springs are the primary water resource for south-central Missouri residents.

Results from Phreeqc provides insight into calcite, dolomite, and iron saturation indices. GW_Chart plotted the chemistry of the Big Four Springs to classify the groundwater type. Discussion of these results and the understanding of the groundwater chemistry type, groundwater kinetics, and potential contamination sources of the Big Four Springs is presented.