U.S. Geological Survey Karst Interest Group Proceedings, Carlsbad, New Mexico, April 29-May 2, 2014

Abstract

Weary of the USGS. The karst hydrology field trip on Thursday will be led by Lewis Land (NCKRI karst hydrologist) and the optional Friday field trip on the geology of Carlsbad Caverns National Park will be led by George Veni. The keynote speaker is Dr.

Simulating groundwater flow in karst aquifers with distributed parameter models—Comparison of porous-equivalent media and hybrid flow approaches

“…Both the SPCE (approaches 1 and 3) and HM (approach 2) simulated observed average spring discharge at Wakulla and Spring Creek Springs within the calibration criterion of 10 percent, and head residuals were within the calibration criterion of plus or minus 5 ft (Davis and others, 2010;Gallegos, 2011;Gallegos and others, 2013). Thus, for average spring discharge and tracer-test time of travel, the three modeling approaches produce similar results, and all are considered acceptable calibrations (Davis and others, 2010;Kuniansky and others, 2011;Gallegos and others, 2013;Kuniansky, 2014). For the HM (approach 2), however, simulated water levels were lower than observed levels, resulting in biased residuals (Gallegos, 2011;Gallegos and others 2013).…”

“…The SCPE approach has been successfully applied for waterresources investigations where the models can be calibrated to flow and head (water level) information and regional-or subregional-scale water budgets are sought (Bush and Johnston, 1988;Geraghty and Miller, Inc., 1991;Davis, 1996;Williams, 1997Williams, , 2006McGurk, 1998;Teutsch and Sauter, 1998;HydroGeoLogic, Inc., 2000;Svensson, 2001;Knowles and others, 2002;McGurk and Presley, 2002;Sepúlveda, 2002;Agyei and others, 2005;Davis and Katz, 2007;Grubbs and Crandall, 2007;Davis and others, 2010;Sepúlveda and others, 2012). In general, the SCPE approach can simulate transient springflow for monthly or annual averages, but may not reproduce detailed storm-event hydrographs as well as other model types because of the onset of non-laminar flow during storms (Hill and others, 2010;Kuniansky and others, 2011;Gallegos and others, 2013;Saller and others, 2013;Kuniansky, 2014). Simulations of advective transport using a single-continuum model are infrequently performed with varying degrees of success.…”

“…Extensive mapping of the sinks and submerged conduit system of the Wakulla Springs-Leon Sinks, Florida, has been accomplished over the past 20 years by cave divers of the Global Underwater Explorers (http://www.gue.com/) as part of the Woodville Karst Plain Project (WKPP; Woodville Karst Plain Project (2015); Kernagis and others, 2008 The WKPP maps served as the basis for three model approaches used to simulate the FAS in the vicinity of Wakulla Springs: (1) SCPE with laminar flow only (Davis and others, 2010), (2) HM that consists of a single continuum coupled to a one-dimensional pipe-flow network capable of simulating laminar and non-laminar flow, an application of MODFLOW-CFP mode 1 (Shoemaker and others, 2008;Gallegos, 2011;Gallegos and others, 2013;Kuniansky, 2014), and (3) SCPE model in approach 1, but with laminar and turbulent flow in the SCPE, an application of the CFP mode 2 (Shoemaker and others, 2008;Kuniansky and others, 2008;Davis and others, 2010;Kuniansky and others, 2011;Reimann and others, 2012;Kuniansky, 2014). Groundwater flow can be non-laminar within a SCPE model layer for the CFP mode 2 approach and so model layer 2, the layer with the submerged conduits, is allowed to have laminar or non-laminar flow.…”

“…The most commonly applied distributed parameter code is MODFLOW, a code that solves the potential flow equation describing saturated groundwater flow (Harbaugh, 2005). Much of the general material on mathematical models presented herein was previously published in Kuniansky (2014) and has been summarized for this report. Application of a porous-equivalent media model with and without turbulence and a hybrid model (porous media with one-dimensional pipe network) were made for the Woodville Karst Plain near Tallahassee, Florida.…”

“…Results from these applications described herein are presented in a manner that can be understood without a rigorous mathematical definition in hopes that some of the concerns about when and how to apply distributed parameter models to the FAS can be better understood (Pittman, 2013). Kuniansky (2014) provides discussion of two other classes of mathematical models that have been applied to karst aquifers: lumped parameter models and fitting models. A discussion of these two other mathematical model types is beyond the scope of this report.…”