I want to Model a closed Basin. I mean that all of the rivers flow to a Lake. I think that it is not bad that WEAP will be equiped to another subject named "Lake" or "Sink". Of course I found a way. I got a "Virtual River" and then put a "Reservoir" on it. My "Virtual River" has headflow equal to zero, and for "Reservoir" I have its Elevation-Volume curve and its evaporation. It works!

yes as you suggested it is usefully if WEAP has one link for Lake. And also it is true you can manage the lake using virtual River and Reservoir. In my understanding it is oke since your lake is closed. What you suggest if the lake have an out let after collecting inflow from different rivers.How you mange the out flow and the water level information. Do you have any exposer please share for us.

Thanks