A mathematical model is developed to simulate the filling/emptying of navig
ation locks and to compute the stress on mooring lines of barges during loc
kage. The model, verified for different filling and emptying systems tend-f
illing systems with valves-in-gate or loop culverts and wall culverts with
side-ports), reproduces satisfactorily the hydraulic transient generated in
the lock chamber and the hawser force. A procedure is proposed to design t
he optimal valve operation for end-filling systems, which gives the minimum
lockage time, keeping the hawser force below the admissible value. It is c
oncluded that valving at a progressively increasing rate diminishes the loc
kage time in comparison to a valve operated at a constant rate.