Reservoir surface area warning message

Chris,

I'm working on the Cowlitz River Dam Break Study for Tacoma Power. Your program continually gives us the following warning on our models:

Warning:
Surface area table entries below entry no. 1 is not exactly compatible with the volume table. The volume table should be checked for possible errors. If possible, use a surface area table rather than a volume table.

This warning appears in the analysis output just after the reservoir volume table is shown and just before a reservoir surface area table is shown (The model must have developed the surface area table since it was not entered.)

We have no Surface area data available to us. We need to be able to enter volume.

Can you please explain the meaning of this warning, and whether or not it is significant?

Dear Dan :

Surface area is the preferred method of defining reservoir volume since the reservoir storage (level-pool) routing uses area in its computations, and the volume to surface area conversion algorithm used in the program does not always provide an adequate conversion.

If you have any additional questions or need any further information, please contact me again.

Sincerely,

Chris E. Maeder, M.S.
Senior Technical Engineer
chris.maeder@bossintl.com

Chris,

The resulting outflow hydrograph seems reasonable but the reservoir volume shown in Analysis Results is much higher than actual. I am comfortable using volume rather than surface area as long as this bogus volume calculation is irrelevant.

We are also having another problem. Even though our inflow hydrograph lasts for 80 hours and the boundary condition for the routing hours is left blank, the model always ends at 30 hours. How can we get the model to run longer? We confirmed that the inflow hydrograph is smooth and have tried numerous other approaches with no success. I would like to show how long it takes for the flow to return to normal - probably several days. Note: The peak flow at the last cross section is reached at 24 hours and then the slope is very gradual. I look forward to your response to the above questions.

Thanks,
Dan