National Ground Water Association - CHARACTERIZATION OF CONDUIT-MATRIX INTERACTIONS AT THE SANTA FE RIVER SINK/RISE SYSTEM, FLORIDA; FEBRUARY 23-24, 2009; SAFETY HARBOR, FLORIDA; P 17-25

ACN	090583733 - PDF of Article
IND	CLM
ENT	090505
AU	SCREATON E; MARTIN J
TI	CHARACTERIZATION OF CONDUIT-MATRIX INTERACTIONS AT THE SANTA FE RIVER SINK/RISE SYSTEM, FLORIDA; FEBRUARY 23-24, 2009; SAFETY HARBOR, FLORIDA; P 17-25
SOU	5TH CONFERENCE ON HYDROGEOLOGY, ECOLOGY, MONITORING, AND MANAGEMENT OF GROUND WATER IN KARST TERRAINS
PUB	NGWA
DATE	2/2009
CLASS	2009 KARST
LAN	ENGLISH
LIB	NGWIC
ABST	Investigations of the Santa Fe River Sink/Rise System in north Florida provide the opportunity to examine the interactions between a subsurface conduit system and the surrounding unconfined eogenetic karst aquifer. The conceptual fluid flow model at this site,located within Oâ€™leno State Park and River Rise State Preserve, has evolved through time as more information has been obtained. Initially, the research focus was on understanding the conduit system. Natural and introduced tracers helped to establish flow paths and velocities; these efforts were complemented by mapping by cave divers. Additional work examined the interactions between water in the conduit system and the surrounding aquifer through monitoring of discharge into and out of the conduit system, conduit and aquifer water levels,and episodic chemical sampling. Results indicate that the underground conduit system drains water from the surrounding aquifer during most time periods. Flow reverses, moving water from conduits to matrix porosity, during high discharge events in the upper Santa Fe River that raise hydraulic heads in the conduit system above those in the surrounding aquifer. This reverse flow has implications for water budgets, water quality, and dissolution of the conduit system. Recent work suggests additional complexity to the system due to both heterogeneity of hydraulic conductivity and multiple origins of water discharging from the system. Hydraulic conductivity varies by 4 orders of magnitude as determined by slug tests and responses of wells to perturbations, creating complexities of exchange between conduits and matrix. Water budget studies,monitoring, and chemical sampling suggest that water within the aquifer is provided by a single discrete input at the River Sink, local diffuse recharge, as well as a source of water upwelling from several hundred meters deep in the aquifer. The importance of each input varies greatly through time, depending on hydrological conditions. Although this work represents a single study site, it demonstrates some of the complications of heterogeneity of flow and water-rock interactions in eogenetic carbonate aquifers punctuated by conduits.