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Bank Storage and Evaporation

Fri, 02/06/2004 - 11:08am — Eric
I actually have two questions. I am looking into the effects of bank storage for my reservoir. Is there a way to model a distributed withdrawal to see if water seeping into the banks is a factor during times when the reservoir is filling? Or is there another way that this process has been addressed in the past? Second, is there a way to output the volume of evaporation that is being calculated by the model? I have daily pan data for the reservoir and I would like to see how they measure up. Thanks[addsig]
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Hydrodynamics
Fri, 02/06/2004 - 11:38am — Tom

You can certainly model groundwater seepage by including a negative value in the distributed tributary for a branch, but keep in mind that the water leaves through the surface layer only. I need to put in a groundwater option that allows the user to specify which layers/segments water enters/leaves from, but haven't had a reservoir application requiring it, so I haven't done it. This would be important for a filling reservoir as groundwater seepage could have a very important impact on the hypolimnetic temperatures if the reservoir stratifies. The evaporation volume is output in the snapshot file as well as the rate.[addsig]
Tue, 10/10/2006 - 12:44pm — vickies

Hi Tom, Came across your post above when I was searching the forum for information on how to model seepage to groundwater. I think I have an application where there is seepage loss from the reservoir to groundwater. Just wondering if you've modified the code since this post to include this feature. Best regards, Vickie Singleton Virginia Tech
Thu, 02/19/2004 - 12:44pm — Eric

Thanks for the help. I have been using the default coefficients for evaporation to compare them to collected data. The model is underestimating the volume of evaporation by 10% - 20% per year over the five year period of simulation. The reservoir that I am modeling is in the southwest so I figure that evaporation plays a major factor. I would like to try to increase the evaporation to simulate this. I tried to use the different evaporation formulations outlined in the manual and other documents, but I think that I am applying them incorrectly because of the drastic change in results. For example with the Lake Hefner formula I entered the coefficients as a=0 b=4.99 c=0 Am I applying this correctly? Also, how does turning ON the Ryan-Harleman equation affect these coefficients, if at all?[addsig]
Fri, 02/20/2004 - 6:53am — Tom

Lake Hefner is not appropriate for your system. I believe the evaporation formula were developed for heated effluent from a power plant, which results in a great deal more evaporation. You have the freedom/flexibility to use any number for the coefficients related to wind, so play around with them. Increasing AFW increases the base evaporation rate regardless of the wind speed. increasing BFW linearly increases the effect of wind on evaporation. CFW non-linearly increases the effect of wind. Keep in mind that this will have an impact on temperatures as well.[addsig]