If you can't read the page above, here's a free page about the canal's current water problems.
"The passage of one ship is estimated to consume as much water as half a million Panamanians use in one day."
The article is probably intesting too, about a drought in Panama that limits the number of ships that can use the canal. I've never heard of that before and the canal is 109 years old. It was widened about 20 years ago and I guess it uses more water because the locks are bigger, but I don't know if that's what made the difference. Maybe the article will say.
"rainfall there has been 30 percent below average this year, causing water levels to plunge in the lakes that feed the canal and its mighty locks. The immediate cause is the El Niño climate phenomenon, which initially causes hotter and drier weather in Panama, but scientists believe that climate change may be prolonging dry spells and raising temperatures in the region."
I'll take this opportunity to brag that I went through the Panama Canal once. In 1971 I went to the yacht club (nowhere near as fancy as that sounds) in Cristobal on the Atlantic Coast, and the owner saw me but let me sit there overlooking the water for several hours after buying only one coke for the whole day. He may have seen me approach everyone who showed up, 2 or 3 people (it wasn't very busy), and ask for a ride back the United States. (The big ships do not dock at either end. They anchor off-shore and the Canal people send out a small boat with someone to have them sign the paperwork. Well, that was 50 years ago. Maybe now they don't even have to do that, but I bet they still greet the ships.)
I offered to work on the boat. Most were not going to the US. One guy would have taken me but his boat was being repaired, and he wanted to go to California while I wanted to go to the gulf or east coast.
Even though I was right near the side door, I don't know if the owner noticed when I slept in his side yard. He had a stack of corrugated galvanized 4x8 sheet metal, and I pulled one off and leaned it against the stack and slept underneath all of it. The following day I went back to sitting there. In a couple hours, when one guy said no, I think he was happy when I quickly lowered my request to just going to the Pacific. 4 people are needed to handle the ropes that keep boats from banging against the lock walls, but he had 2 sons and a nephew to help him. He took me anyhow, and I didn't have to do anything. It took about 6 hours iirc. His wife made hotdogs for all of us. I didn't cause any trouble.
I'd given up my plan to get back to the USA for free and a day or two later, I flew home. It was 150 dollars to Miami and then San Antonio.