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All Topics | Topic "Constraints"
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Author Message
Janak Timilsena

Subject: Constraints   
Posted: 12/14/2009 Viewed: 23942 times
I am working to set the constraints for the groundwater extraction. I am running the model in daily time step. In my project, constraint is in annual basis (i.e. it can not exceed 90 mgd for wateryear). Some of the time steps could be more than 90 mgd and some of the time step could be less than 90 mgd, but end of the water year the average should not be exceeded 90 mgd. I have tried to use the following function in max flow volume;

PrevTSValue(Maximum Flow Volume[Million gal],1,365,1<90)

but it constraints everytime step, which i donot want.

Do you have any suggestion to incorporate this type of constraint in WEAP?
Jack Sieber

Subject: Re: Constraints   
Posted: 12/14/2009 Viewed: 23941 times
Very interesting idea! What you are trying to do is constrain the flow through the transmission link in the current timestep so that it doesn't push the average (over the past year) above some threshold (90 million gallons per day (MGD)). In order to do this, you need to calculate the flow in the current timestep that would cause the average to be exactly 90 MGD, then constrain the flow through the link to be at most this flow. The answer is to subtract the total flow over the previous 364 days from 90 * 365 to get the "available" flow for the current day. Also, you need to make sure the answer is not negative.

Max(0, 365 * 90 - PrevTSValue(Flow[MGD], 1, 364) )

Note: PrevTSValue(Flow[MGD], 1, 364) will sum up the flow, in MGD, over the previous 364 days.


Topic "Constraints"