In the model I am working on we have some lakes that are reservoirs and some that are just lakes (all with HRU class LAKE). It is my understanding that those that are classified as reservoirs will be overwritten by the reservoir functions while those that are just LAKE will be left as is. In the Reservoir Mass Balance file the reservoir losses (ET) are about where we expect them. In the WatershedMassEnergyBalance (from the custom output :WriteMassBalanceFile) file the Lake Evaporation from Lake to Atmosphere is very small (annually 1 mm) and does not seem to account for the ET losses in the reservoir and at one point were actually negative.
Are reservoir processes not accounted for in the Mass Balance for the entire watershed? If I wanted to determine total AET from open water would I add the two together? Is it possible for there to be a negative transfer from lake to atmosphere through lake evap? We are using LAKE_EVAP_BASIC.
Lake Evaporation in the Mass Balance
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jrcraig
- Posts: 57
- Joined: Tue Jul 05, 2016 1:08 pm
Re: Lake Evaporation in the Mass Balance
The low rate of lake evaporation could be due to the fact that this is averaged over the entire watershed (i.e, if the lakes covered 1/100th of the basin with 100 mm/yr evaporation, it would average out to 1mm/year of lake evaporation watershed-wide). You would be better off generating a custom output From: SURFACE_WATER (or whatever your lake storage is) To: ATMOSPHERE for the lake HRUs only.
The reservoir evaporation is lumped in with the cumulative watershed outflow in the mass balance calculations, and wouldn't show up in the mass balance SURFACE_WATER->ATMOSPHERE reported in the Mass Balance file.
The negative Lake ET concerns me though- this could currently happen if your lake storage is negative; this should not happen and will be added to the bug list.
The reservoir evaporation is lumped in with the cumulative watershed outflow in the mass balance calculations, and wouldn't show up in the mass balance SURFACE_WATER->ATMOSPHERE reported in the Mass Balance file.
The negative Lake ET concerns me though- this could currently happen if your lake storage is negative; this should not happen and will be added to the bug list.
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MarkRag
- Posts: 1
- Joined: Thu Mar 07, 2019 5:12 am
Re: Lake Evaporation in the Mass Balance
How do you recognize the negative Lake ET bug btw?
This is why professionals think highly of these mig welders and their features.
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rchlumsk
- Posts: 156
- Joined: Fri Sep 16, 2016 3:18 pm
Re: Lake Evaporation in the Mass Balance
Hi MarkRag
In the rvi file, adding the command ":WriteMassBalanceFile: will produce the 'WatershedMassEnergyBalance.csv' file, where you can check all of the various fluxes during the simulation. Noticing a negative set of values in any of the ET fluxes, including the one from Lake to Atmosphere, is where bugs like that can be checked and QA/QC'd.
In the rvi file, adding the command ":WriteMassBalanceFile: will produce the 'WatershedMassEnergyBalance.csv' file, where you can check all of the various fluxes during the simulation. Noticing a negative set of values in any of the ET fluxes, including the one from Lake to Atmosphere, is where bugs like that can be checked and QA/QC'd.
Robert Chlumsky
rchlumsk@uwaterloo.ca
rchlumsk@uwaterloo.ca
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LausitzModeler
- Posts: 4
- Joined: Tue May 25, 2021 6:04 am
Re: Lake Evaporation in the Mass Balance
Hi,
I have a similar problem as sgrass_nhc in March 2019.
We are currently modelling a watershed with a large manmade reservoir. The reservoir is defined as a subbasin with a single HRU and the :Reservoir section includes the :HRUID command.
We expected the evaporation from the reservoir to be significant for the watershed water balance. However, reservoir stages are not decreasing due to evaporation losses. Additionally, the evaporation from the reservoir does not appear as lake evaporation or another flux in any of the MassBalance output files. And the watershed hydrograph is higher than expected. If reservoir evaporation is lumped together with the outflow in the mass balance as Prof. Craig wrote; is the watershed hydrograph in turn overestimating actual runoffs by the amount of water, which is not evaporated from the reservoir area? I am not that familiar with the Raven source code though, so please correct me if that is not the case and reservoir evaporation is handled differently during simulation.
If that is the case however, is there an elegant way to include evaporation from a manmade reservoir and get an output for it?
My only idea was to include the amount of evaporation from the reservoir as a :ReservoirExtraction time series in m3/s, which unfortunately would make calibrating parameters like OW_PET_CORR more difficult.
We are currently using Raven Version 3.0.4 because Version 3.5 was released after we started building our model.
Did anything change from Version 3.0.4 to 3.5 regarding the processing of reservoir evaporation for manmade reservoirs? (The user manual seems to be the same for reservoir evaporation.)
Best Regards,
LausitzModeler
I have a similar problem as sgrass_nhc in March 2019.
We are currently modelling a watershed with a large manmade reservoir. The reservoir is defined as a subbasin with a single HRU and the :Reservoir section includes the :HRUID command.
We expected the evaporation from the reservoir to be significant for the watershed water balance. However, reservoir stages are not decreasing due to evaporation losses. Additionally, the evaporation from the reservoir does not appear as lake evaporation or another flux in any of the MassBalance output files. And the watershed hydrograph is higher than expected. If reservoir evaporation is lumped together with the outflow in the mass balance as Prof. Craig wrote; is the watershed hydrograph in turn overestimating actual runoffs by the amount of water, which is not evaporated from the reservoir area? I am not that familiar with the Raven source code though, so please correct me if that is not the case and reservoir evaporation is handled differently during simulation.
If that is the case however, is there an elegant way to include evaporation from a manmade reservoir and get an output for it?
My only idea was to include the amount of evaporation from the reservoir as a :ReservoirExtraction time series in m3/s, which unfortunately would make calibrating parameters like OW_PET_CORR more difficult.
We are currently using Raven Version 3.0.4 because Version 3.5 was released after we started building our model.
Did anything change from Version 3.0.4 to 3.5 regarding the processing of reservoir evaporation for manmade reservoirs? (The user manual seems to be the same for reservoir evaporation.)
Best Regards,
LausitzModeler