MODFLOW-NWT and MT3D-USGS models for evaluating heat flows, lags and dampening under high emission climate forcing for unsaturated/saturated transport in a synthetic watershed

A 3-dimensional (3D) synthetic model, built for running with MODFLOW-NWT and MT3D-USGS, explores the new unsaturated zone heat transport capabilities in MT3D-USGS. Model simulations explore potential responses to within a watershed to climate warming along system pathways. The response analysis uses output from a 30-year warming period on a synthetic watershed patterned after a humid temperate climate which incorporates two variable unsaturated thickness configurations, shallow and deep groundwater flow, and discharge to streams and other surface-water bodies. The climate forcing data in this archive relies on trends and noise from global climate model (GCM) simulations for the northern continental U.S. as it moves from top of unsaturated zone to a) the water table as recharge, b) stream channels as direct groundwater discharge, c) stream channels as groundwater baseflow including groundwater runoff and d) stream channels as total streamflow including surface runoff. All pathways are simulated either by MODFLOW-NWT or the Unsaturated-zone Flow (UZF1) package. The "moderate thickness" and "high thickness" versions of the synthetic model are applied to isolate the effect of variable unsaturated zone (UZ) thickness on lags and dampening. Furthermore, the model is used to investigate the thermal inertial effects imposed on the system by the infiltrating heat forcing signal are characterized both in terms of temperature (the dependent variablein MT3D-USGS) and heat flow (the combination of flow and temperature in the MT3D-USGS budget). Recharging heat flow is parsed into its conductive, dispersive and convective components, where the last term is found to dominate. Importantly, this investigation serves as a steppingstone to a real-world application that is far more complicated by nature's heterogeneity; an aspect of real-world simulations that is avoided in the current simulations. Temperatures simulated by MT3D-USGS were previously verified by comparing output from detailed 1-dimensional models to VS2DH output (ADD LINK). This USGS data release contains all the input and output for the scenarios described in the associated journal article. (https://doi.org/10.3390/w14182810).