as running and see the result/reservoirs/elevtion The coresponding elevation of initial storage in my natural lake is the minimum ellevation. but in the obserbed it is not.
I need help on how to make the elevation get lower than the initial storage elevation.
and
how to keep the out flow from reservoir(natural lake) pernial. as inthe natural case.

Actually I did not get your point exactly. If you tell me more specially with numbers, I can help you more. But:
1- if you define evaporation in your lake, water elevation can be less than something that you expect.
2- You, yourself can input initial storage, so change it!

nice day

Sorry for my Expretion
Totally my problem was fixing the spillway level in the reservoir so that water will never get out unless that level is exceeded