Effects of climate and land-use change on thermal springs recharge—A system-based coupled surface-water and groundwater-flow model for Hot Springs National Park, Arkansas

First posted June 14, 2021 For additional information, contact: Director, Lower Mississippi-Gulf Water Science CenterU.S. Geological Survey640 Grassmere Park, Suite 100Nashville, TN 37211 A three-dimensional hydrogeologic framework of the Hot Springs anticlinorium beneath National Arkansas, was constructed to represent complex hydrogeology park and surrounding areas depths exceeding 9,000 feet below ground surface. The framework, composed 6 rock formations 1 vertical fault emplaced thermal springs, discretized into 19 layers, 429 rows, 576 columns incorporated a 3-dimensional steady-state groundwater-flow model in MODFLOW-2005. Historical daily mean spring flows were simulated for one stress period approximately 34 years (1980–2014), chosen record historical climate data used quantification boundary conditions. manually calibrated 88,000 cubic per day observed over 12-year (1990–1995 1998–2005) at springs collection system. Calibration achieved by calculating starting heads general head conditions from Bernoulli equation then adjusting horizontal hydraulic conductivities conductance head-dependent flux boundaries. coupled surface-water developed Precipitation-Runoff Modeling System (PRMS) using PRMS-simulated gravity drainage as specified recharge condition model. Together, models (1) locate groundwater forward reverse particle-tracking capabilities MODPATH, (2) simulate effects variable rates on (3) assess possible land-use change long-term variability springs.Forward backward maps indicated that most prevalent this study within about 0.6–0.9 mile springs. Forward particle tracking area southwest corresponded location where predominant lithologies are Arkansas Novaculite, Sandstone, Bigfork Chert. Backward second localized northeast dominant lithology is probable Chert, Sandstone.The changes spring-flow generally resulted reductions flow attributed urban development more extreme climates characterized elevated surface air temperatures. predicted linear relation between discharge cumulative volume applied positive slope indicates precipitation events supply may fact increase rates.