Technically, you only need a single reverse outlet to allow water to run in both directtions between two nodes. Perhaps you're asking about reversing flows involving three nodes in series?
But before you attempt to model any reverse flow, there are other options you should consider, such as combining adjacent storage into a single pond. For details please see
You also need to resolve other warning messages, especially any overfilled storage messages, before making decisions about modeling reverse flows. For general modeling tips please see