Initial WSEL in an "empty" reservoir

Hi. I am modelling a reservoir since it begans to operate, and I am having some problems with it. Since it has no water in the first day and a relative small water level in the initial days, the initial WSEL is in the first day the same than the EBOT near the dam. When I put it in the model, it gives an error! I have 1 water body with 3 branches. I made a lot of experiences and I saw that the model only runned when I put a WSEL of 109 in all branches, being the EBOT and the real WSEL in the first day near the dam 81. Should I just run the model from that day (I have a real WSEL of 109 two months later the first day of dam operation). Can you help me please? Thank you very much[addsig]