|MILLER, B - Western Kentucky University|
|GROVES, C - Western Kentucky University|
|POLK, J - Western Kentucky University|
Submitted to: Hydrogeology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2014
Publication Date: 2/3/2015
Citation: Miller, B.V., Lerch, R.N., Groves, C.G., Polk, J.S. 2015. Recharge mixing in a complex distributary spring system in the Missouri Ozarks, USA. Hydrogeology Journal. 23:451-465. DOI:10.1007/s10040-014-1225-y.
Interpretive Summary: Distributary spring systems are characterized by multiple spring outlets in close proximity which share common sources of groundwater. Traditionally, the water discharging from these springs has been viewed as having been derived from a single groundwater source, and therefore, of homogeneous chemical composition. Toronto Springs, located in the central Missouri Ozarks, is an example of a complex distributary spring system in which two separate groundwater sources mix. One source is Carroll Cave (CC), a large karst aquifer, and the other source is Wet Glaize Creek (WG). Previous research established that a portion of WG stream flow is diverted to the sub-surface where it mixes with CC water and discharges through one of 11 perennial springs identified as part of the Toronto Springs system. The objective of this research was to: 1) characterize the physical and chemical properties of the groundwater sources and the springs at Toronto Springs; 2) develop mixing models to estimate the proportion of CC and WG to each spring; and 3) create a conceptual model for the system. Intensive monitoring showed that the springs differed in their properties and the differences were related to the proportion of recharge from CC and WG. Estimates from the mixing models showed a range of recharge proportions, with one spring estimated to be >90% WG and another spring estimated to be >80% CC. Several springs had nearly equal proportions of the two sources. A conceptual model proposes a system of distinct conduits extending beneath the WG flood plain that transmit water to the individual springs. These conduits controlled the recharge contributions and water chemistry discharging from the springs. Results of this work have contributed to a more sophisticated understanding of the hydrologic complexities associated with distributary spring systems. Researchers studying groundwater hydrology will benefit as the approaches used here can be applied to other distributary spring systems. The public will benefit as these systems may be used as drinking water sources and improved methods for understanding their hydrology can lead to improved water quality and/or source water protection.
Technical Abstract: Toronto Springs is a complex distributary karst spring system with 11 perennial springs in the central Missouri Ozarks, USA. Carroll Cave (CC) and Wet Glaize Creek (WG) were previously identified as principal recharge sources. This study 1) characterized physical and chemical properties of the springs and recharge sources; 2) developed end member mixing models to estimate contributing proportions of CC and WG; and 3) created a conceptual model for the system. Continuous monitoring of temperature, specific conductivity (SpC), and pH along with grab samples analyzed for major ions and SpC were used to assess differences among the sites. Monitoring data showed that the springs differed depending upon recharge proportions. Cluster analysis of average ion concentrations supported the choice of CC and WG as mixing model end members. Results showed a range in the proportions of the recharge sources, from surface to groundwater dominated. A conceptual model suggests that a system of distinct conduits beneath the WG flood plain transmits water to the individual springs. These conduits controlled the end member recharge contributions and water chemistry discharging from the springs. Results of this work have contributed to a more sophisticated understanding of possible hydrologic complexities associated with distributary spring systems.