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National Cave and Karst Research Institute

Publication Date

November 2013


Mark ChildreNatural Sciences and Kinesiology Department Laredo Community College West End Washington Street Laredo, TX 78040 AbstractThe hydrogeologic controls, flow velocities, flow direction, groundwater delineation, and physical characteristics in a joint controlled dendritic conduit- spring system are characterized. The known conduit extends from Magic Spring to and past CM Cave with 4,475 m of measured passages and tributaries. Four storm events were measured characterizing the system's hydrodynamics. The rise time and half flow period time (t0.5) occur in less than a day. The volume of ground stored in conduits is approximately one half million m3. Storm flows into the conduit-spring system drain within 3.7 to 7.5 days. This system is thermally ineffective with little radial heat flux into the conduit walls. The field components of this study include a karst feature density survey, four dye traces, continuous monitoring of dynamic parameters, stage height, and discharge at Magic Spring. Hydrographs and chemographs show patterns interpreted as pulses of water recharging through caves, sinkholes, and a stream sink. These pulses are superimposed on baseflow from the joint controlled dendritic conduit- spring system. The dye tracing results identified groundwater piracy across surface water divides. The storm flow velocities at Magic Spring ranged between 8,700 and 15,120 m/d with baseflow characteristics below 3,000 m/d. Open Access - Permission by Publisher See Extended description for more information.