교육데이터 활용•지원 서비스

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://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. Changes in water-table position for each scenario simulation are categorized in figures in this data release as (1) within 7 feet of the land surface, (2) within 3 feet of the land surface, or (3) above land surface and are expressed relative to the water-table position simulated in the updated dry- or wet-weather base simulations. The descriptions focus primarily on changes to the distribution of groundwater towards the center of the model domain. Groundwater distributions towards the western edge (west of Grand Blvd.), southwest (south of US-20), and eastern edge (towards Ogden Dunes) of model domain show relatively small variations in the scenario simulations and are outside of the primary area of interest. The scenario of rerouting water from entry into the Gary sanitary sewer system at the weir at site CS-1 to County Line Road ditch through underground pipes (scenario 1a; figs. 3-6) used the MODFLOW Drain Return Package to transmit water from the US-12 ditch to a drain return cell at the intersection of County Line Road ditch and 5th Avenue. This simulated hydrologic modification produced an expanded area of shallow groundwater within 7 feet of the land surface in the areas surrounding the drain return cell location. A small groundwater mound developed in the dry-weather underground pipes simulation at the intersection of County Line Road and 5th Avenue, with the water table within 3 feet of the land surface. In the dry-weather underground pipes simulation (figs. 3 and 4), the portions of the area between Union Street and County Line Road ditch were inundated. Water-table position changes north of US-12 or west of Spencer Street were minimal. In the wet-weather underground pipes simulation (figs. 5 and 6), water ponded at the intersection of County Line Road and East 5th Avenue. Both dry- and wet-weather underground pipes simulations exhibited similar patterns of water-table changes, but differences between water-table positions in the underground pipes and updated wet-weather base simulations were minimal in areas away from the drain return cell. The scenario of diverting water from US-12 ditch to Spencer ditch then trenching to the County Line Road ditch (scenario 1b; figs. 7 and 8) required creation of new drain cells to connect the southern