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All Topics | Topic "Unmet Water Demand, and WEAP solver"
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Author Message
Dr. Muhammad Shafqat Mehboob

Subject: Unmet Water Demand, and WEAP solver   
Posted: 8/30/2019 Viewed: 7319 times
Dear All,
while working on supply and demand analysis in WEAP, Can you tell me how WEAP distributes water among its various demand sites. for example if the I want to distribute 10 mcm among three demand site A,B and C where A's demand is 6 mcm, B's demand is 3 mcm and C's demand is 1 mcm. each demand site have same priority. Can you tell what will be unmet water demand in this case?
My second Question is WEAP gives totally different results if we change the WEAP Solver (LP or XA), do you know why is so?
My last question is that I run two scenario one with high population growth and one with low population growth rate, it is obvious that unmet water demand of High population growth rate is more as compared to low population growth rate, supply is same for both scenarios WEAP gives unmet water demand of low population scenario more than high population growth scenario?
I have spent my three days on it but couldn't get the logic?
waiting for your Reply.
Dr. Hossein Babazadeh

Subject: Re: Unmet Water Demand, and WEAP solver   
Posted: 9/1/2019 Viewed: 7308 times
Dear Muhammad,

First of all, you want to distribute 10 MCM for 10 MCM demand, therefore, you can satisfy all demand with 100% coverage. In the cases of the same priority, the shortage will apply equally percent on all demand.

Second, WEAP includes two MILP solvers (lpsolve and XA), and an option to link to another (Gurobi). lpsolve is open-source; XA and Gurobi are commercial. On very large models, the commercial solvers can perform much faster (up to ten times faster) than lpsolve, and are usually more robust. lpsolve is free for everyone to use; XA is free for everyone to use until 15 July 2020; Gurobi is free only for academic use ( http://www.gurobi.com/products/licensing-and-pricing/academic-licensing ). Keep in mind that, due to the nature of the complex numerical calculations performed by MILP solvers, each solver will yield slightly different results. This means that WEAP results can vary slightly depending on the solver used(Ref. WEAP HELP).

Finally, I think you have a mistake in your population scenarios. I recommend checking it again. I can do it if you send it by email.

Best Wishes,

Dr. Muhammad Shafqat Mehboob

Subject: Re: Unmet Water Demand, and WEAP solver   
Posted: 9/1/2019 Viewed: 7295 times
Thank You so much for your quick response,
1. Let me more specific, in the above example as I asked you earlier, instead of 10 mcm if I want to distribute 8 mcm, then how how it will distribute?
for example site A will receive 6/10*8? am I correct? and unmet demand will be (6-(6/10*8))?
2. There is a huge difference between results of both, I dont know what is issue with my WEAP.
3. For population scenario higher population is actually a daughter scenario (every thing is same except population, higher population scenario is under low population growth rate).
Mr. Matthew Scott

Subject: Re: Unmet Water Demand, and WEAP solver   
Posted: 12/4/2019 Viewed: 7007 times
Dear Hossein,
I'm interested in more details of the Sunset XA MILP Solver. You mention that it is free until July 2020. What about pricing after that? I'm currently working on some rather large models in Sri Lanka & would like to make sure that if we start to use the XA Solver then we can continue to use this through next year without incurring large future license costs.
I also couldn't seem to find out much information about it on the Sunset website. Can you point me to somewhere else please for help.
Thanks & regards,
Mr. Jack Sieber

Subject: Re: Unmet Water Demand, and WEAP solver   
Posted: 12/5/2019 Viewed: 7006 times

At the moment, we do not know if we will renew the XA license that everyone can use when our current license expires next July, although I think it is likely. We will know more when it is sooner to the expiration date.

If we do not renew it, I think individual licenses for XA cost $1800. (An individual license has no expiration date.) To obtain an individual license, you would need to contact Sunset Software directly. You can also contact them for more information about XA.

Best regards,
Topic "Unmet Water Demand, and WEAP solver"