Subject: Circular Branch/ Variable refrence error Posted: 4/6/2016 Viewed: 16554 times
Hi WEAP Users,
When i want to Creat additional key assumption (Tutorail:Page 52), an error occured (Growth fuction can not be used in current accounts),
Also, are you using this function in the annual activity level, or in a key assumption?
Dr. Muhammad Abrar Faiz
Subject: Re: Circular Branch/ Variable refrence error Posted: 4/8/2016 Viewed: 16508 times
Dear Ma'am,
in key assumption. and i am using equ. Grouth (2.2%)
The Growth equation is different from the GrowthFrom equation because with Growth, you're only telling WEAP the growth rate. If you use the Growth equation in Current Accounts, WEAP doesn't know what number to start with. Is it a 2.2% growth on 7? or a 2.2% growth on 3 million?
So in current accounts, start with a "GrowthFrom" equation. If the growth rate stays the same for the duration of your model, you don't have to change the equation. If the growth rate changes, you can change it in the appropriate year using the Year TimeSeries Wizard in your Reference Scenario.
I am getting the same type of error when I try to use the Expression builder to update the area of a glacierised branch to the GlacierArea result of the previous time step. The expression I use is:
Area[km^2]=PrevTSValue(Glacier Area[M^2])
It it is a simple expression that uses outputs as inputs. From my point of view it should not be a problem, but it seems that WEAP does not like it...
Thanks,
Andrea
Dr. Andrea Momblanch Benavent
Subject: Re: Circular Branch/ Variable refrence error Posted: 2/23/2017 Viewed: 15336 times
I just realised that I am not using the same units (km2 vs. m2), but probably that is not the reason why I am getting a circular reference error, right?
Ms. Stephanie Galaitsi
Subject: Re: Circular Branch/ Variable refrence error Posted: 2/23/2017 Viewed: 15330 times
Hi Andrea,
WEAP should be able to calculate between km^2 and M^2 no problem, so you're right, that should not be the issue.
Is Glacier Area a user-defined variable that you have created? Have you checked the results for this variable to make sure that it is calculating correctly? How does it calculate? I'm trying to imagine why WEAP would give you a circular reference warning if you're referring to a previous time step value. Is Glacier Area a land-use type of your catchment?
Dr. Andrea Momblanch Benavent
Subject: Re: Circular Branch/ Variable refrence error Posted: 2/23/2017 Viewed: 15326 times
Hi Stephanie,
The Glacier Area is a result generated by the Soil Moisture method when the option "Model Glaciers?" in the catchment is selected. According to the user's manual, WEAP considers uniform ice accumulation and melt in the catchment (or branch, if you choose the option of different climate data in each branch), and calculates the Glacier Volume multiplying ice depth by catchment/branch area. Then, using an empirical relationship, it calculates the estimated Glacier area which would show the growth and shrinkage of glaciers. The manual points out that this Glacier area is not used for melt or snow accumulation, since only the total catchment/branch area is used for that purpose.
My idea is updating, for every time step, the area of the branch that I have defined as Glacierised to the value of the Glacier area resulting from the previous time step, so that I can consider the evolution of the glacier size. I would also have to update the area of the other branches in the catchment accordingly to keep the total area unchanged, and update the ice depth for the new area to keep the glacier volume.
To me, it sounds good in theory, but in practice I cannot even make the first stage of updating the branch area work... Any ideas of what could be the problem?
Thanks!
Ms. Stephanie Galaitsi
Subject: Re: Circular Branch/ Variable refrence error Posted: 2/24/2017 Viewed: 15317 times
Hi Andrea,
I didn't realize you were using the glacier routine. That's already pre-programmed to take the previous time step into account. If you're editing it dynamically, it will through off the calculations. You don't have to enter any data, you can let WEAP calculate the area.
Dr. Andrea Momblanch Benavent
Subject: Re: Circular Branch/ Variable refrence error Posted: 2/24/2017 Viewed: 15311 times
Hi Stephanie,
From what I have read, the manual clearly says that the area used to calculate melt and snow accumulation is static and equal to the area of the catchment/branch. I want to change that static area in my model by the output variable Glacier Area in previous time step.
Probably I am not explaining myself very clearly... Sorry about that.
Thanks
Ms. Stephanie Galaitsi
Subject: Re: Circular Branch/ Variable refrence error Posted: 2/27/2017 Viewed: 15293 times
Hi Andrea,
The area of the catchment is static - catchments are defined by their discharge points downstream. Within the catchment, you can have different land use types. The glacier should not be its own land use type (I think this is what you mean by your previous comment, where you define an area as glacierized), the glacier routine in WEAP assumes that the glacier can grow and shrink on top of the other existing land use types.
I'm trying to envision what you have in front of you, can you explain a little bit more?
