I imagined UI would be simply to click the center that the Hydrologist was at and drag to another center, then in addition to a potential boat-launch 0 drill sub, there would be a second option of a dotted arrow called flow-lane and some icon that when touched would flip the direction of flow so you can pick if the flow is going to the center the hydrologist is at or going away to the other center.

The Hydrologist specialist would just have a counter like the queen does 'time till flow lane change' and when you click the Hydrologist specialist the mechanic for flow lane establishment would be the same as factory production, flow lane change stopped (red flashing light mechanic) to pause timer and re-start it once a new flow lane is established.