MODFLOW-2005 and MODPATH models in support of groundwater flow model investigation of water resources at Chaco Culture National Historical Park

Situated in a remote corner of northwestern New Mexico, Chaco Culture National Historical Park (CCNHP) was once the center of a sophisticated social, political and architectural civilization with a 50,000-square mile sphere of influence. The park protects the greatest concentration of Chacoan historical sites in the American Southwest and is arguably the most significant prehistoric site in North America. Following decades of unsuccessful attempts to develop usable near-surface water sources, the National Park Service constructed a 3,100-foot deep well into the Gallup Sandstone aquifer in 1972, providing the park with the first reliable drinking water source since it was established in 1907. The ~100-foot thick Gallup Sandstone is sandwiched between thick confining sequences of the lower-permeability Mancos Shale. Both the Mancos Shale and the Gallup Sandstone are part of the San Juan Basin and critically, both units have long been targeted for oil and natural gas development. Groundwater-flow (MODFLOW-2005) and advective transport (MODPATH) models of the Mancos Shale and Gallup Sandstone units in the vicinity of CCNHP were created in order to determine groundwater-flow paths to the park well, and to test how potential hydraulic fracturing operations could influence the well. This USGS data release contains input and output files for the model simulations documented in the associated model report (https://doi.org/10.3133/sir20235097). In total, 204 groundwater-flow and 206 particle-tracking simulations were performed.