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All Topics | Topic "Supply data and input availability and expressions for system modelling."
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Author Message
Rebeca Doctors

Subject: Supply data and input availability and expressions for system modelling.   
Posted: 5/18/2016 Viewed: 3267 times
Hello,

I'm new to WEAP and I'm having some troubles in understanding the data that has to be put as input (in the case of the supply modeling). First, I would like to know if it's necessary to supply all data to the reaches so that the model works (and by all data I mean: Inflows and Outflows (Surface water inflow, groundwater inflow, groundwater outflow, evaporation, etc) physical data, costs...). What will happen if I don't have all this data?

Also, I haven't understood very well what is meant by "below river 'x' headflow" (supposing that I have a river called x), since it's already asking to provide average monthly inflow at head of river. Wouldn't it be the same? If not, what exactly is this measure?

What exactly is below a river 'x' inflow?

Say I have the data for a reservoir that is close to a river headflow. Could I use this value for the inflow at head of river?

Another issue I have is the following: Suppose I have a reservoir in a river (a) and another reservoir further in the same river (b). Again, I have data for reservoir inflows. Could I say that the difference between these two reservoirs (b-a) inflows is the inflow below reservoir a?

Finally, I want to model my system for different expressions. For example, I want to determine that a reservoir should only release water for a minimal threshold. How can I do this?

Sorry for all these questions (I have looked into the WEAP tutorial and I couldn't find theses answers).

Thank you in advance!

Kind regards,

Rebeca



Stephanie Galaitsi

Subject: Re: Supply data and input availability and expressions for system modelling.   
Posted: 5/19/2016 Viewed: 3259 times
Dear Rebeca,

There are two ways to model a river: you can enter in the flow data itself, or use catchments to calculate runoff.

It sounds like you are entering flow data. You can find an example of this in the Tutorial section "WEAP in One Hour" and the subsection "Entering Elements into the Schematic." You enter water in the headflow of the river (when you click on the name of the river), and then the individual reaches assumes this water, plus or minus the supply that has been taken out in the distance between the headflow and each particular reach.

There are many ways to take water in and out, and some of them, as you pointed out, are in the river reaches themselves. You don't have to enter this data, the model will still run (as the tutorial model does). There is always the issue of accuracy though - rivers usually do have additional surface water inflow as they move downstream.

Reservoirs typically change the streamflow patterns. If you have data for *inflow* you could use that for headflow directly above the reservoir. Just be certain it's not the reservoir *outflow*.

Instead of subtracting reservoir inflows from each other, I would program the headflow as I said in the previous paragraph, and then use the data you have to validate the outflow from the top reservoir - it should approximate the inflow to the second reservoir (depending on the distance, and other inflows and outflows happening in between the two reservoirs). You can plug in the second inflow as a streamflow gauge above your second reservoir and compare the data and the model results.

For your final question, I would recommend reviewing the Tutorial section "Reservoirs and Power Production" and the subsection "Modeling Reservoir Operation."
Rebeca Doctors

Subject: Re: Supply data and input availability and expressions for system modelling.   
Posted: 5/19/2016 Viewed: 3253 times
Dear Stephanie,

Thank you for your reply.
I'm not sure if I understood well what you said. To make it more simple, the difference between two reservoirs, for example, is the reach equivalent to "below reservoir a" ?

And regarding your last comment, I think I wasn't very clear. I've already checked the tutorial, but it doesn't really explain how I could model different conditions. Say I want a reservoir outflow to depend on another reservoir outflow (the second reservoir will only release water if the first one respects a given condition). How could I model this expression? I saw there is a way to add an expression in the "expression builder". Do you have examples of this? I couldn't find it in the tutorial.

Once again, thank you for your kindness and attention!
Stephanie Galaitsi

Subject: Re: Supply data and input availability and expressions for system modelling.   
Posted: 5/20/2016 Viewed: 3239 times
Dear Rebeca,

You want the WEAP to model the water in the river to approximate (as close as possible) the data for your inflows to the two reservoirs. If you start your model directly above the first reservoir, this is easy, because you can plug the inflow data into your model. At the downstream reservoir, you cannot plug in the inflow data - you have to let WEAP calculate the streamflow, and then you can validate WEAP's calculations against the inflow data you have for the second reservoir. On your first model run, it will probably not be very close. You will need to ask:

1) How is the upstream reservoir releasing water (and is that accurately programmed in WEAP)
2) How much more water comes into the system between the upstream reservoir and the downstream reservoir (and is that accurately programmed in WEAP)
3) How much water is removed from the system between the upstream reservoir and the downstream reservoir (and is that accurately programmed in WEAP)

For your second question, I directed you to the tutorial so you can read the section on reservoir operations. If that is not sufficient for you, then you will need to make an expression in the Expression Builder. This expression will depend on your system.

You can also check out the WEAP video about the Expression Builder: http://www.weap21.org/index.asp?action=220 (scroll down)
Rebeca Doctors

Subject: Re: Supply data and input availability and expressions for system modelling.   
Posted: 5/23/2016 Viewed: 3208 times
Hello again Stephanie and sorry for the delay in replying,

Thank you for the video, I'll check it out. And if I understood, WEAP does its own calculations (to see water inflow in a node, for example), so if I give how much will inflow in a first reservoir, and how much water it uses, and etc. it should give an approximation of the inflow on the second reservoir (downstream). Is that it?

Thank you once again!
Stephanie Galaitsi

Subject: Re: Supply data and input availability and expressions for system modelling.   
Posted: 5/25/2016 Viewed: 3201 times
Correct: you give WEAP a starting flow in the river (whether by entering data or using catchments) and after that you can build demand or supply nodes that augment or reduce that original flow, and WEAP will use those to calculate the new flow in later points of the river.
Rebeca Doctors

Subject: Re: Supply data and input availability and expressions for system modelling.   
Posted: 5/25/2016 Viewed: 3194 times
Thank you for all your attention and help!
Topic "Supply data and input availability and expressions for system modelling."