MODFLOW-2005 and MODPATH6 models used to simulate groundwater flow and nitrate transport in two tributaries to the Upper Chester River, Maryland

A previously developed steady state three-dimensional groundwater flow
(MODFLOW-2005) and advective transport (MODPATH6) model was
used to examine subsurface nitrate transport to wells and receiving
streams in two subcatchments contributing to the Upper Chester River,
Maryland. Multiple scenarios of flow and transport parameter fields
(recharge, hydraulic conductivity, and porosity) were previously
calibrated against groundwater levels, stream discharge measurements,
and atmospheric tracer measurements, as described in
https://doi.org/10.1016/j.jhydrol.2018.02.006; those multiple scenarios
are also available as a USGS data release (https://doi.org/10.5066/F7SN087R).
Two of the flow and transport scenarios calibrated in Zell et al. (2018) were
selected to simulate nitrate transport, with MODPATH6 files updated as
necessary to represent advective transport from observation wells with
subsurface nitrate measurements. The development of the model input
and output files included in this data release and the application of the
models to nitrate transport simulation are documented in the Journal of
Environmental Quality article (https://doi.org/10.2134/jeq2018.11.0408).