As many have commented here about pumps and pumping. There are no pumps used to raise ships in the locks. This is pointed out in every detailed description of the engineering design.
Gatun Lake is higher than both ocean levels. Water raised in the lower locks is or has been up until now— drained out into the oceans. Pumping these quantities of water would be quite expensive in energy to pump.
The canal was expanded in 2016 by adding another lane to increase traffic. The lake and freshwater supply was not increased. There is no crisis other than poor engineering.
EC
Water CAN BE pumped.
Why would you pump water if there’s plenty of it at the height of Lake Gatun. Hence, no pumps were built back in the day because there was plenty of water.
But, the demand for transit has increased tremendously. Ships loiter waiting transit. These wait times are costly.
To be sure, pumping water - if pumping water is feasible - will probably impact fees for transit. Such are the realities of the world.
Now, let’s ask the question: why are there any deserts in the world? Because the cost of pumping water, and desalinization where necessary, isn’t free.