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All Topics | Topic "About Groundwater Balance (and results) of a coupled WEAP-Modflow approach"
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Mr. Eduardo Rubio

Subject: About Groundwater Balance (and results) of a coupled WEAP-Modflow approach   
Posted: 1/15/2020 Viewed: 7034 times
Greetings from Chile.

We are working in the analysis of a coupled surface-groundwater model, to understand the correct results of the graph: Groundwater inflows and Outflows (GIO).

We have several "groundwater boxes (GB)" coupled with Modflow. We don´t have any runoff infiltration link between these GB´s, due to we understand that MODFLOW take care of this specific connection (cell by cell).

When we analyze the GIO, we believe this seems to be a "vertical" balance, I mean, it includes recharge, pumping, with the specific details of where the water goes and comes from.

Nevertheless, we cannot find or see if WEAP quantifying (throw MODFLOW) the specific flow between the GB´s, that are also part of the GW mass balance.

So the questions are:
1. The graph of WEAP: Storage Capacity, is based on the results of Modflow? I mean, includes the horizontal groundwater flows tha
t are related to the cells that were linked in the coupled process?

The spirit of this question is if the GIO graph could be related to a "zone budget" of Modflow, at least in the storage variation.

2. Is there any way to see the flows between the GB in WEAP, or we have to
check the output results of modflow (*.out)?

Thanks in advance for any guidance in this process.

Mr. Chuck Young

Subject: Re: About Groundwater Balance (and results) of a coupled WEAP-Modflow approach   
Posted: 1/16/2020 Viewed: 7024 times

Answers to your questions:

1. Yes, the storage graph shows the net change in storage based on the boundary flows (GHB, Fixed Head), recharge, pumping, RIV package, and lateral flows. Yes, the GIO result is similar to what Zone Budget provides.

2. In your GIO results you should see a result that is labeled something like:

Inflow from GroundwaterNode X

Outflow to GroundwaterNode X

where GroundwaterNode X is the name of a neighboring groundwater basin which has its name assigned to neighboring cells in the MODFLOW linkage file. If the two groundwater basins do not have neighboring cells in the linkage file then there will not be any results.

Please let me know if you have additional questions.

Mr. David Poblete

Subject: Re: About Groundwater Balance (and results) of a coupled WEAP-Modflow approach   
Posted: 1/15/2021 Viewed: 6090 times
Hi Chuck and Eduardo, I also have a question regarding the Modflow results when run coupled in WEAP.

When showing the Groundwater inflows and outflows, there is one Destination called "Outflow to Outside of Area". When dealing with basins ending at sea, there is no problem as we assume that that water is flowing to the sea, but when the Modflow space is within the basin, when need to take that water and transfer to the river or to a next Groundwater node (that's what I whant).

I'm using a Demand node linked to the cells that used to have Constant Head boundary conditions (downstream) in the original Modflow model. The comsumption is 0 but the actual demand should depende on the groundwater volumen or to some cell heads. We use a demand to get a similar value to was reported in previous projects, but we are still having this "Outflow to Outside of Area".

So my questions is: How to take that water that should leave the Modflow donwstream cells into a WEAP element so it does not leave the system?

Mr. Chuck Young

Subject: Re: About Groundwater Balance (and results) of a coupled WEAP-Modflow approach   
Posted: 1/21/2021 Viewed: 6043 times
Hi David,

In my experience the "Outflow to Outside of Area" is the sum of any constant head or general head boundaries. It is also possible that if the WEAP groundwater node has reached its capacity then it may generate "Outflow to Outside of Area." Please check that the groundwater node has not reached capacity (Supply and Resources\Groundwater\Storage).

It is also possible to check the water budget from the MODFLOW simulation in the .out file for a particular timestep and compare it with the WEAP results to confirm that the model is performing as you want it to.

Please feel free to email me directly if I can help further.


Topic "About Groundwater Balance (and results) of a coupled WEAP-Modflow approach"