Panama: when a single lake sets the price of global trade.

Optical baseline. Satellite optical imagery — down to roughly 10 m ground sampling on the visible and near-infrared bands, refreshed every few days — photographs Gatun Lake and the upstream Alajuela (Madden) reservoir whenever the sky is clear. As the lake falls, the shoreline retreats — mudflats and exposed lakebed appear where there was water weeks before. That receding edge is a direct, visual measurement of stored volume.

Water-extent mapping — turning pixels into surface area. A water-extent index contrasts the green and near-infrared bands so that water goes strongly positive and land goes negative. Thresholding it per pixel produces a clean water mask; counting the masked pixels and multiplying by pixel area yields lake surface area in square kilometres, tracked image by image. Pair that time series with the reservoir's known depth-area-volume curve and the 2-D surface becomes a volume estimate.

Drought context. Standardised drought indices — precipitation anomalies and vegetation-condition indices over the watershed — place a single low reading in its multi-year context, so a dry month is distinguishable from a structural decline. In 2023, Gatun sat near 80 feet through the back half of the year against a more typical ~88 feet at the close of the wet season.

Why radar works here. All-weather radar — synthetic-aperture radar — emits its own microwave pulses and measures the echo, so it images day or night and straight through cloud and rain. A steel hull is a strong corner reflector: microwaves bounce off the metal and the deck structure and return a bright point against the radar-dark sea. Ships light up as discrete targets even when the optical scene is solid overcast.

Counting the queue. Detecting and counting those bright targets in the anchorage off Balboa (Pacific) and Cristobal/Colon (Atlantic) yields a vessel count at anchor. The image at the top of this page is the optical version of exactly that signal — dozens of ships parked offshore in August 2023. Tracking how that count rises and falls week to week is an instant, independent supply-chain throughput indicator: a growing anchorage means congestion is building before any official advisory confirms it.

Why the trees matter. Porous, forested soil absorbs heavy tropical rain and releases it slowly through the dry season, smoothing the flow into the reservoir. Strip the forest and bare soil sheds rain in fast, muddy pulses: the water floods through and runs to sea instead of being banked, and the runoff carries sediment that silts up the lake, eroding the very storage capacity the canal depends on.

What EO monitors. Optical time series flag deforestation and land-clearing as they happen. A vegetation index — the near-infrared-minus-red contrast that scales with healthy green biomass — tracks canopy vigour and stress across the watershed. Falling vegetation vigour over a slope is an early flag for erosion potential and, downstream, reservoir sedimentation.

Measuring water height from orbit. Radar and laser altimeters fire a pulse straight down and time the return to fix the water-surface height. Reference-grade radar altimetry, and newer wide-swath interferometric altimetry that maps a water body in two dimensions rather than along a single ground track, can resolve inland water-surface elevation to the centimetre class — an actual lake level, not a surface outline.

Why centimetres are money. The Panama Canal Authority sets a maximum permissible draft against the available depth over the lock sills. In the 2023 drought the Neopanamax draft limit was cut from the normal 15.24 m (50 ft) toward 13.41 m (44 ft) — nearly two metres of cargo a vessel could no longer carry through. A bulk or container operator can convert that lake level directly into a loadable draft, and therefore into a cargo mass / TEU ceiling, weeks before the ship reaches the lock.

Ship-type identification. A vessel's radar signature — how strongly it reflects radar — scales with its size and superstructure, and its polarimetric response differs by hull form. All-weather radar can transmit and receive in dual polarisation; the ratio and texture of those channels, fed to a machine-learning classifier, can separate a bulk carrier from a container ship from a tanker through complete cloud cover, no optical view required.

Dark vessels via radar + AIS fusion. Most ships broadcast their identity and position over AIS. Fuse the radar detections with the AIS feed and the interesting cases are the mismatches: a hard radar target with no matching AIS signal is a "dark vessel" — a ship that has switched off or is spoofing its transponder. Radar sees the physical object regardless of what the transponder claims.

Radar interferometry for the structures. Comparing the phase of repeat radar passes measures ground and structure displacement at millimetre-to-centimetre scale. Over the lock chambers, approach walls and surrounding terrain, radar deformation analysis can flag subsidence and slow movement — an early, remote check on the stability of the fixed infrastructure itself.

Soil moisture. Microwave soil-moisture radiometry measures the moisture in the top layer of soil across the watershed. Dry, parched soil absorbs the first rains rather than passing them downstream; soil already near saturation lets rain run off into the lake. Soil-moisture state is therefore a leading variable for how effective the coming wet season will be at refilling Gatun.

Gravimetry for the macro deficit. Satellite gravimetry detects tiny changes in Earth's gravity field caused by shifts in total water mass — surface water, soil moisture and groundwater combined. At regional scale this reveals a cumulative water deficit or surplus that a single lake gauge cannot, putting one reservoir's level inside the basin-wide water budget.

The choice. A vessel can join the queue and wait; it can bid for a priority slot at auction — which during the 2023 drought hit a reported US$4 million for a single passage (officially ~US$3.98M, paid by Japan's Eneos Group for an LPG carrier on 8 November 2023, on top of standard tolls); or it can reroute entirely, around Cape Horn or the Cape of Good Hope, trading days at sea and extra fuel and CO2 for certainty of passage. For a major line such as Maersk or MSC, the difference runs to millions of dollars per ship and weeks of schedule.

EO as the predictive engine. Lake level, soil moisture, anchorage counts and transit cadence are the live inputs to a supply-chain digital twin — a running simulation of the network. Feed the orbital signals in and the twin can model, roughly 30 days ahead, the fuel cost, CO2 and time-loss of waiting versus rerouting for a given vessel and cargo, turning a gut call into a costed decision.

What it is. The centre is a regional hub that brings Earth-observation data and services to governments across a region highly exposed to climate-driven hazards. Its mandate is climate resilience — turning satellite signals into decisions, not archives.

Why it matters for the canal story. It is built as an operational early-warning capability — among its thematic services are dedicated drought and wildfire monitoring alongside flood mapping, drawing on the same satellite signals described above and feeding regional disaster-risk-reduction decisions. The hydrology that governs the canal sits inside exactly the drought-and-forest signals such a hub is designed to watch.