A 35.8% rainfall deficit puts the Panama Canal on 32 transits a day

The scheduling logic runs through the lock chambers. Each transit sends roughly 200 million liters of fresh water down to the sea, and that water comes from rainfall held in artificial lakes; without it the locks do not lift ships at all ^[8][7]. Four fewer transits a day therefore retains about 800 million liters daily ^[1]. That is the trade the authority is making: fewer transits now, set against the risk of running short on water later.

The draft cut is what reaches stowage plans. Going from 15.24 to 14.63 meters removes 61 centimeters ^[2]. At former administrator Jorge Quijano's rule of about 200 containers lost per 30 centimeters of draft, that is roughly 400 boxes per vessel ^[15][3], around 2.5 percent of capacity on a 16,000-TEU ship ^[4].

The 2023-24 episode is the closest thing to a comparison, and it was harsher: 22 transits and 13.41 meters ^[11]. It produced 20 percent fewer vessels and a 17 percent fall in tonnage ^[12]. Put those two together and average tonnage per transiting vessel rose about 4 percent ^[7]: operators spent scarce slots on bigger and fuller ships, while marginal callers absorbed the squeeze. What that 20 percent does not tell you is how much came from the draft limit and how much from the slot cap, since both landed at once alongside demand shifts and voluntary rerouting, so the two effects are hard to separate cleanly.

It is also worth being clear about what the headline transit number does not measure. Daily slots are the published quantity; waiting time and the price of a booking slot are the quantities that show up in a charter party, and the canal's caps are a ceiling rather than a forecast of realized volumes. Maersk's position that it is too early to speculate about impact ^[17] is defensible on exactly that ground.

The other claim on the same watershed is domestic. It supplies drinking water to half of Panama's 4.6 million people ^[22], about 2.3 million ^[9], through infrastructure designed nearly a century ago ^[22]. Lockage and municipal supply draw on one hydrological account. The engineering answer, a 4,600-hectare reservoir on the Indio River, is not expected before 2031 ^[21], at least four years past the drought horizon the canal is currently planning around ^[8].

My working view: for 2027 planning, 32 is the optimistic case rather than the floor, because it assumes a dry season that forecasts already expect to start early and run into May behaves as modeled ^[10]. Anything that requires 32 transits and 14.63 meters to hold is, in the end, a bet on rainfall.