MODPATH6 models used to evaluate effects of complexity on groundwater age metrics in the Fox-Wolf-Peshtigo watersheds, Wisconsin

This data release contains five groundwater particle-tracking models (MODPATH6) of
northeastern Wisconsin, USA, that were developed to work with three MODFLOW
models that have differing levels of complexity. The previously developed MODFLOW
models (https://doi.org/10.3133/sir20175010 and https://doi.org/10.5066/F73J3B3P)
were modified slightly to ensure proper functioning with MODPATH6. Modifications
to the original MODFLOW models included: 1. changing IPHDRY in the UPW package
so that the dry cell flag value (HDRY) was written to the binary heads (*.hds) file, 2.
selecting the compact budget option to ensure proper utilization of IFACE values by
MODPATH, and 3. the period length (PERLEN) was increased for one model, although
it has no effect on the simulation.

The goal of the modeling exercise was to evaluate the effects of the flow-model (MODFLOW)
based complexity on estimates of groundwater age metrics. Results of the evaluation illustrate
the importance of properly simulating perennial streams, as both hydraulically fully-penetrating
streams and hydraulically partially-penetrating streams influence groundwater ages in aquifers
by capturing groundwater of differing age that is associated with the aquifer depth from which
the groundwater is captured. This work was performed as part of the National Water Quality
Assessment (NAWQA) Project's groundwater Mapping and Modeling work plan to evaluate
effects of differing levels of model complexity on simulated results. This USGS data release
contains all of the input and output files for the simulations described in the associated
Groundwater paper (https://doi.org/10.1111/gwat.13088).