The Canal That Runs on Rain
The Panama Canal lifts every ship 26 metres into a lake made of rain, then lets the water run out to sea. When the rain failed in 2023, the world’s great shortcut had to ration itself.
About 50 million gallons of fresh water (~190 million litres) flow from Gatun Lake to the ocean every time one ship crosses through the original locks. — Panama Canal Authority
Up 26 metres, across a lake, down again
Three lock steps at Gatun lift ships to the lake; Pedro Miguel and Miraflores lower them to the Pacific. Gravity does the work, and gravity only runs one way.
Gatun Lake carries ships 33 km of the roughly 80 km crossing. It sits about 26 m (85 ft) above sea level.
No pumps fill the locks. Each lockage opens valves and lets lake water fall into the chamber, and that water then goes out to sea. The newer Neopanamax locks (Agua Clara and Cocolí) store water in side basins and reuse about 60% of it.
ACP; Gatun Lake reference data · profile schematic, lock-step heights approximate
A lake that fell into the drought zone
October 2023 brought 41% less rain than normal, the driest October since 1950. Gatun Lake spent most of the year near its record low.
ACP lake data via WTW (2024); Riviera Maritime Media (2023) · strip runs light (low) → dark (full)
From 31 slots a day to 18
With less water to spend, the canal cut how many ships could book a crossing each day, step by step.
The cuts arrived just as the rainy season, which normally refills the lake, failed. Ships queued at both entrances, and some carriers rerouted via Suez or around the Cape of Good Hope.
World Weather Attribution found this was roughly a 1-in-40-year drought for an El Niño year. It found no clear evidence that climate change caused it, but rising demand on the lakes made the shortage worse.
Maritime Executive (Nov 2023, citing ACP); World Weather Attribution (2024) · booking slots, not completed transits
A one-year dip of nearly 3,000 ships
Annual transits fell by about a fifth in fiscal 2024, then recovered most of the way once the rains came back.
FY2024: 11,240 transits, down from 14,080. FY2025: 13,404, up 19.3%, with record revenue of about $5.7 bn.
Toll revenue held up even in the drought year because ships bid at auction for the scarce slots.
ACP annual reports and statements, FY2022–FY2025 (fiscal year Oct–Sep)
Why the world puts up with it
Before 1914, a ship going from New York to San Francisco had to sail around the bottom of South America.
The canal cut the route by about 7,900 nautical miles, roughly 60% of the voyage. The isthmus is narrow, but the land is high, and that is why the canal needs a lake: digging to sea level was tried in the 1880s and failed.
The Panama Canal handbook (1910s), Panama Canal Archive
Building more rain-catchers
The same lakes supply drinking water to Panama’s biggest cities, so the canal and the country compete for every drop.
Why it matters
- The lake is the canal. More than a third of the route is a dammed river valley. Without rain, the canal can’t move ships.
- Everything drains outward. Colón and Balboa are the drains. Every lock flight sends fresh water down to the ocean.
- Watershed, not ditch. The dashed line matters more than the blue line: forests and rivers across the watershed decide how many ships can cross.
- The next lake is west. Río Indio sits outside today’s watershed. Building it means flooding a new valley, and the people who live there have opposed the plan.
Sources & notes
- Panama Canal Authority (ACP), “The Panama Canal adapts strategic measures for water savings” (2023): ~50 million gallons of fresh water per transit; Neopanamax water-saving basins reuse 60%.
- Wikipedia / ACP, Gatun Lake (accessed 2026): surface 26 m (85 ft) above sea level; carries ships 33 km of the crossing; ships lifted in three steps at Gatun.
- Maritime Executive (Nov 2023, citing ACP): booking slots cut from 31 to 25/day by Nov 6, 2023 and to 18/day from Feb 1, 2024.
- Riviera Maritime Media (Nov 2023, citing ACP): October 2023 rainfall 41% below average, the driest October since 1950.
- WTW / ACP lake-level data (2024): Gatun Lake low of 79.24 ft (late Jul 2023), high of 81.83 ft (Nov 2023); record minimum 78.3 ft (May 19, 2016).
- ACP annual traffic (FY2022 Informe; FY2024 via Kuehne+Nagel/EFE; FY2025 via Baird Maritime): transits 14,239 / 14,080 / 11,240 / 13,404.
- The Panama Canal handbook (1910s), Panama Canal Archive: New York–San Francisco 13,135 nmi via Cape Horn vs 5,262 nmi via Panama.
- ACP via Baird Maritime / Hellenic Shipping News (2025): Río Indio reservoir ~$1.6 bn; expected to add ~15 transits/day; drinking water for >50% of people in Panamá, Panamá Oeste and Colón provinces.
- World Weather Attribution (2024): the 2023 drought is roughly a 1-in-40-year event in El Niño years; no clear attribution of the drying trend to climate change; canal needs ~7 billion litres/day.
Notes: the map and elevation profile are schematic (hand-drawn; distances along the profile approximate). “≈85 ft nominal” is the lake’s 26 m reference surface, not an operating limit. Booking slots are not identical to completed transits. Fiscal years run Oct–Sep.