Subject: Demands and priorities Posted: 1/29/2014 Viewed: 15549 times
I have two questions; it will be appreciated if you can help me.
-If there is a reservoir with capacity of 60 million m³ and this reservoir is supplying 2 demand sites; urban demand (priority =1)and agricultural demand (priority =2). If the reservoir is full at the n time step and the demand in the same time step for the urban demand site is 20 million m³ and for the agricultural demand site is 30 million m³, so at this time step the demands are satisfied for both sites. At next time step n+1, there will not be enough water for both demand sites, if we assume that the river inflow is low also. My question is how I can say to WEAP that if in the next time step (n+1) the urban demand site will not be satisfied, do not supply all the demand of the agricultural demand site in the n time step.
-If there are 3 demand sites, DS1 and DS2 get the water from the same source and they have different priority, DS1 =1 and DS2=2. The other demand site DS3 has priority 1 but satisfies its requirements from other source (river 2). My question is will the demand site DS3 affect the supply coverage of the DS2??? Will the water release downstream from river 1 to cover the demand of the DS3 first because it has higher priority than DS2, even if they are not supplied from the same source??? And if yes, how can I prevent this happens??
Thanks in advance,
Devaraj de Condappa
Subject: Re: Demands and priorities Posted: 1/30/2014 Viewed: 15518 times
For your 1st question, I don't think you can tell WEAP to do calculations in step n, then n+1, and then based on results of step n+1 possibly go back to step n. Jack Sieber would confirm if it is possible but to my understanding WEAP proceeds forward during calculation time steps and never goes back. I could see however a possible alternative. Do you know that you can also set a priority to fill the reservoir? By default this priority is 99 (hence a reservoir will always staisfy all demands) but you can set another value. For instance in your case you could have urban demand priority 1, reservoir priority 2 and agriculture priority 3. Or urban and reservoir priority 1, agriculture 2. By setting a relative high priority to the reservoir, WEAP will be conservative in releasing water which can models the way a reservoir is operated (we do not want to empty too fast a reservoir). You can play with different priority arrangements and find out which one could maybe work.
For your 2nd question, if I understand well river 1 discharges into river 2? If the case, I think that indeed WEAP may constrain supply to DS2 so that DS3 get satisfied as much as possible, considering also DS1. But I am not sure, I advise you to explore. Maybe here again Jack can confirm. And if it is the case then maybe again you can play with the priority, ie setting a lower priority for DS3 compared to DS2 (ie priority DS3 = 3). If river 1 and river 2 are not connected then WEAP calculates the coverage of DS3 independently to DS2.
Hope this helps.
Subject: Re: Demands and priorities Posted: 1/30/2014 Viewed: 15517 times
Deva is correct on both points.
1. WEAP is a simulation tool, not an optimization tool. This means that like the real world, you have to make guesses about the future and cannot go back and change the past. Deva mentioned the option of increasing the reservoir filling priority higher than the agriculture demand site. Another possibility is to try using the Buffer Zone and Buffer Coefficient to reduce reservoir releases.
2. If river 1 flows into river 2, then a lower priority demand on river 1 (DS2) will be satisfied after the higher priority demands on river 2 (DS3). This is because WEAP considers the priorities of the system as a whole. If you really do want DS2 to get allocated water before DS3, then make the priority for DS3 lower than for DS2. If the two rivers are not connected, allocations to DS2 are not constrained by allocations to DS3.
Subject: Re: Demands and priorities Posted: 2/4/2014 Viewed: 15461 times
Dear Jack and Devaraj,
Thanks alot for your reply and your help. I am trying to change the priority of the demand sites and the reservoirs in order to make the system behaves more close to the reality.
I have another question if you can help me with it please, if I have artificial aqueducts that connect a reservoir with another reservoir or supplying water from a river reach to another reservoir, should I use a transmission link or diversion to present them on WEAP??
Devaraj de Condappa
Subject: Re: Demands and priorities Posted: 2/4/2014 Viewed: 15457 times
You should use a diversion.