to the existing channel system through new navigational channels. The new lock chambers are long, wide, and deep. They use rolling gates instead of miter gates, which are used by the original locks. Rolling gates are used in almost all existing locks with dimensions similar to the new ones, and are a proven technology. The new locks use tugboats to position the vessels instead of electric locomotives. As with rolling gates, tugs are successfully and widely used for these purposes in locks of similar dimensions. Water saving basins The new locks have water-saving basins to reduce the volume of water that is needed in lock operation. The operation of both the old and new locks uses gravity and valves. There is no pumping involved. Operation of the locks, old and new, uses water from Gatun Lake. Even in the current situation with two lock lanes, water supply can be limited at the end of Panama's dry season, when the lake's water level is low. The addition of a third set of locks meant that this water supply issue needed to be addressed. Three basins are associated with each lock chamber. The volume lost per cycle is two-fifths of the "moving water" chamber volume. The other three-fifths is reused. An equal savings of water, based on the same principle, could be reached by adding more lock chambers. Constructing a stair of eight chambers (instead of three) to elevate would use an water slice per cycle. However, this would require ships to travel through eight locks, making ship handling less efficient. Water usage is calculated per single lock cycle. It is determined by the water volume in a lock chamber between the levels it handles. Essentially, each cycle uses the volume of water discharged by the lock chamber (its width multiplied by its height and depth). When the locks are in stairs, as in the Panama Canal, only the first (highest) lock chamber matters for this calculation. None of the lower locks use additional water; they have the same volume. Moreover, the ship's underwater volume does not matter, because that volume is present both before and after the change in water level and thus is part of the non-moved volume. The water used per lock operating cycle is therefore equal to the amount of water that flows into the first (upper) lock chamber when filling it from Gatun Lake. Reducing this volume