MODFLOW-NWT model scenarios used to evaluate potential effects of proposed drainage modifications on groundwater discharge in the vicinity of Long Lake, Indiana Dunes National Lakeshore, near Gary, Indiana

A previously developed three-dimensional groundwater-flow model that used the MODFLOW-NWT code was updated to simulate the effects of various proposed drainage modifications aimed at reducing discharge to a sanitary sewer system near Long Lake in Indiana Dunes National Lakeshore, near Gary, Indiana. The original steady-state model documented in the USGS report (https://pubs.usgs.gov/sir/2013/5003/) and data release (https://dx.doi.org/10.5066/F7D21VS2) was calibrated to a low groundwater level/dry weather condition of October 2002 and a high groundwater level/wet weather condition of March 2011. For this study the 2002 and 2011 simulations were updated with elevation data collected from a 2017 survey of primary surface-water features that affect groundwater levels to create dry- or wet-weather base simulations (figs. 1 and 2). Eight scenario models were created by modifying the updated 2002 and 2011 base simulations. The scenarios examined the effects of potential modifications to the hydrologic system: (scenario 1a) diverting water from US-12 weir (site CS-1) to County Line Road ditch through underground pipes [figs. 3-6], (scenario 1b) diverting water from US-12 ditch to Spencer ditch, then trenching Spencer ditch to the County Line Road ditch to drain to the Little Calumet River [figs. 7 and 8], (scenario 2) Extending and altering US-12 ditch to flow east toward County Line Road ditch and drain to the Little Calumet River [figs. 9 and 10], and (scenario 3) installing culverts under US-12 and adjacent railroad lines to connect US-12 ditch with West Long Lake [figs. 11-14]. This data release contains all files and associated information needed to run these additional simulations.