prevent unsaturated zone storage in UZF package

[RyanConway91]

I am working on setting up a loosely coupled groundwater-surface water model using MODFLOW6 and HSPF. I want to use UZF for recharge because I want to route runoff (with MVR) to simulate a wetland system. However, I do not want UZF to simulate unsaturated storage, as the HSPF will do that so I would be double counting. Can I just set thtr to 0 and thts 1e-10 to prevent storage? or is there a better way tot do this?

[emorway-usgs]

So HSPF won't calculate runoff flows? If it did, you could just specify which stream reach(es) or lake(s) should receive the runoff calculated by HSPF.

[RyanConway91]

HSPF does calculate runoff, and I plan on routing them to SFRs. I thought about using LAKs or SFRs for the wetlands, but its a large distributed wetland complex that can't be reasonably represented by SFRs or LAKs.

I like the UZF-based wetland approach used by Feinstein, Daniel T., et al. "A simple method for simulating groundwater interactions with fens to forecast development effects." Groundwater 58.4 (2020): 524-534.

They used SWB instead of HPSF, but more importantly, they ran a steady state model, so unsaturated zone storage by UZF was not an issue.

[emorway-usgs]

You might consider using the DRN package to represent wetlands. The groundwater seepage component of UZF is slated for deprecation because the DRN package offers the same functionality. Part of the motivation for the deprecation is because for transport, it's helpful to keep the rejected infiltration separate from the groundwater discharge component. UZF combines these two sources of runoff which can be problematic when they carry different concentrations/temperatures.

[RyanConway91]

I considered DRNS, but I like the linear conductance you get from SURF_DEPTH in UZF and more importantly I need to be able to route water through the wetland complex and DRN cant be a receiver for MVR. Thanks for the ideas though, I'll report back on what happens in transient run with very low theta_sat and theta_res