Subject: Reservoir calibration Posted: 7/2/2018 Viewed: 10551 times
Hi,
I am currently working with WEAP to represent my system. I have rivers flowing into a lake, from which water exits as seepage and forms another river. The catchments of the rivers flowing into the lake have been represented with the Soil Moisture Method. I have the storage capacity, initial storage, net evaporation and observed volume of the lake. The outflows from the lake result to the river I have mentioned and a diversion to a hydropower plant.
However, as I am trying to calibrate the lake by adjusting the parameters in the catchments (root soil conductivity, deep soil conductivity, etc), in the results section, WEAP only shows me the observed volume of the lake with the storage volume of the lake (in Observed and Computed Storage Volume). Would you be able to tell me why this is so? I would expect the simulated volume to fluctuate with changing parameters in the catchments.
Please let me know as soon as possible.
Thanks.
Regards,
Meghna
Mr. Jack Sieber
Subject: Re: Reservoir calibration Posted: 7/2/2018 Viewed: 10548 times
The Computed Storage Volume is the simulated volume in the reservoir, based on simulated inflows and outflows. Runoff from the upstream catchment will definitely affect the inflows, so the reservoir level should fluctuate in response to changing hydrologic conditions.
Are you saying that the simulated storage is always the same as the maximum Total Storage of the reservoir? A reservoir will only release water to meet downstream demands (instream or offstream), or to meet hydropower demands, or if the Top of Conservation level changes. Otherwise, the reservoir will fill to capacity and then stay there.
To learn more about reservoir operations, see the "Reservoirs and Power Production" and chapter of the WEAP Tutorial: https://www.weap21.org/Tutorial
Jack
Ms. Meghna Dave
Subject: Re: Reservoir calibration Posted: 7/2/2018 Viewed: 10541 times
Hi Jack,
Thanks for your response. Yes, the total storage of the reservoir does not seem to be fluctuating, and yet I have outflows from the system that are fluctuating. I am adjusting the parameters of the catchments contributing to the inflow, to no avail. How can I ensure that the reservoir releases water?
I have 2 outflows from the lake - one to a demand site (I have an average flow in cms to represent this) and the other to a hydropower plant (this is also represented as an average monthly flow).
Regards,
Meghna
Mr. Jack Sieber
Subject: Re: Reservoir calibration Posted: 7/2/2018 Viewed: 10531 times
My guess is that the inflow to the lake is larger than the downstream demands, which would mean that the lake will always be full. Look at the streamflow in the reach just upstream of the lake to see what the inflow is.
Jack
Ms. Meghna Dave
Subject: Re: Reservoir calibration Posted: 7/2/2018 Viewed: 10526 times
The inflows into the lake are via one transmission link (which works) and a return flow link from a demand site (this return flow link does not seem to be transmitting any water to my lake). The outflow to the hydropower plant is working too but not enough to fluctuate the storage volume, it seems.
However, I need to connect the lake to a river, and this flow from the lake to the river is governed by a set of equations. I tried to connect it via a "dummy' demand site and specified the equations in the transmission link to the "dummy", which is then connected to the river via a return flow link. It seems that the "dummy" demand site is not extracting the water. Would you know how I can work around this?
Meghna
Ms. Meghna Dave
Subject: Re: Reservoir calibration Posted: 7/2/2018 Viewed: 10516 times
Hi Jack,
In order to model the outflow from the lake in terms of the set of equations I have, I changed the link from the reservoir to the river headlow node to a diversion link, but it still does not reflect in the simulated volume of my storage. In the results section, when I select reservoir overflow, there seems to be a fluctuating overflow over the time period.
It seems as though my reservoir is not releasing water asintended. In the input values, I have entered the inflow (sum of the inflows to the lake), storage capacity of the lake, initial storage of the lake (lower than the storage capacity of the lake), volume-elevation curve, net evaporation and observed volume. I do not have any constraints regarding the operation of the lake. I just need it to model the inflows and outflows such that I can view the computed storage over time.
Please let me know if you have any suggestions to work around this.
Thanks,
Meghna
Mr. Jack Sieber
Subject: Re: Reservoir calibration Posted: 7/5/2018 Viewed: 10500 times
In the Results View, look at the Reservoir Inflows and Outflows report -- it will tell you all the inflows and outflows to the reservoir.
