uzf MODFLOW UZF water budget HORT+DUNN

[Sylvain 0]

Hi,

I have recently started using the UZF package to simulated groudwater flow in a regional model. I firstly developed a steady state model using spatially distributed recharge from a surface model. I was using the «recharge» and the «EVT» package. With this configuration i was able to obtain a water budget with % error < 0.001%. When i replaced the recharge and EVT packages by the UZF, the water budget output file shows a line with a component called «HORT+DUNN» which i suspect to be the surface runoff flow. This component is not well describe in the USGS MODFLOW documentation. The problem is that this volume of water is only present in the «IN» part. In then creates a poor water balance ~1% to 5% error. If i remove it from the balance, the % error is good (> 0.01%).

Any idea of how to deal with this water budget component?

Regards

[Michal 0]

Hi,

I agree it is poorly documented. I had to dig into the source codes to figure it out. It seems to be an excess infiltration volume rejected by the model. It can be routed to other packages as described in the ModelMuse documentation:

"If the applied infiltration rate is larger than the vertical hydraulic conductivity, the actual infiltration will be reduced to the vertical hydraulic conductivity. Any remaining potential infiltration will be available to the MVR package as rejected infiltration."

So I guess if you lower your infiltration rate this term should approach zero.

I have no idea why the text description in the budget file states "HORT+DUNN". Maybe somebody else could clarify that.

[Adel 0]

Are you able to input the prec. data directly to this module, or it has only the option for Recharge rate? please, if you have any documantation or information for how to enter a storm events to this UZF or SFR2 package, share that with me?

 

[Michal 0]

Yes, you input infiltration rate (L/T) at land surface as FINF (NCOL, NROW). The documentation is here:

https://water.usgs.gov/nrp/gwsoftware/modflow2000/MFDOC/index.html?uzf___unsaturated_zone_flow_pa_3.htm

https://pubs.usgs.gov/tm/2006/tm6a19/pdf/tm6a19.pdf

[Adel 0]

Thank you so much for your generouis response..

The FINF, it is for infilitration (recharge), but is there any way to directly input the rainfall date, like if you hava a storm for 48 hr, with (L/T) data? the figure below for the recharge rate

[Michal 0]

You can input rainfall as infiltraton rate FINF. UZF package should take care of calculating true groundwater recharge from this flux accordingly.

[Adel 0]

Thank you so much for your generouis response..

The FINF, it is for infilitration (recharge), but is there any way to directly input the rainfall date, like if you hava a storm for 48 hr, with (L/T) data? the figure below for the recharge rate

[Adel 0]

Thank you so much for your help!