The new locks actually use about 8% less water than the historic locks due to water recycling
https://www.britannica.com/topic/Panama-Canal/Locks
"The basins were completed in June 2016 and include 158 valves consisting of 20,000 tons of structural material. Officials say those water-saving basins are the largest in the world and facilitate a 60 percent reuse of water. Whereas the existing locks use 52 million gallons (197 million litres) with each use, the new locks use 48 million gallons (182 million litres)".