Right now
12 of 19 reservoirs unchanged in the last hour
6 rose, 1 fell and 12 held level, of the 19 reservoirs.
Newest reading: Aug 31, 2026, 6:45 AM
We read the USGS sensors behind AAA's daily bulletin. We publish the most recent reading for each of the 19 reservoirs, with the exact time it was taken.
The biggest changes
Yesterday's changes, reservoir by reservoir.
The largest falls
- LocoObservation-0.05m69.33 m
- La PlataOperational adjustments-0.05m44.66 m
- LucchettiSafety-0.01m170.99 m
Selected by: the 24-hour change, most negative first, among reservoirs that reported
These figures come from the 5:00 AM bulletin; the change is measured between two bulletins.
The largest rises
3 of 14
- Río BlancoObservation+0.20m24.49 m
- FajardoObservation+0.16m46.40 m
- GuayabalObservation+0.11m102.50 m
Selected by: the 24-hour change, most positive first, among reservoirs that reported
These figures come from the 5:00 AM bulletin; the change is measured between two bulletins.
The 19, at a glance
Every reservoir, drawn.
The phase lines sit at the same height on every card, so what moves is the water.
8 of 19 · Selected by: percent of each reservoir's own range, lowest first
Against its own normal
Lowest against normal
Patillas
4.00 m below normal for this date
A ±7-day window around August 31, 2026, this reservoir's own most recent reading. · 63.36 m
Selected by: the lowest percentile against normal, among reservoirs with 15 or more years of record
The latest report
Where these figures come from.
- Bulletin
- August 31, 2026
- Cut-off
- 5:00 AM (AST)
- Coverage
- 19 of 19 reservoirs reporting
- Newest reading on the island
- Aug 31, 2026, 6:45 AM
How we read the data
The large figure on this portal is the most recent reading we have received from the USGS gauge, with the exact time it was taken. The gauges measure every 15 minutes and transmit in hourly batches, so that figure refreshes through the day and can be several hours old overnight. We keep every one of those measurements.
Beside it we always publish the 5:00 AM AST reading, labelled as such. That is the one we use for everything that compares one day with another — the 24-hour, 7-day and 30-day changes, the history, the phase runs and the comparison against normal — because it is the same cut-off every day, and that is what makes those comparisons valid. Subtracting the 5:00 AM reading from the most recent reading would mix two different cut-off times and cannot be published: a single day's swing alone moves some reservoirs by 26 to 32 cm. Comparing two gauge readings with each other is a different matter — the one at the start of a window against the most recent one: there both ends are the same kind of sample from the same series, and that is the recent change we publish. What we never do is subtract a 5:00 AM figure from a reading taken at any other hour.
AAA's daily bulletin is drawn at 4:55 AM and carries the freshest reading that had arrived by press time; the 5:00 AM reading does not enter the record until around 5:57 AM. On days when levels move quickly the two figures can therefore differ by about a centimetre. Each is correct for its own cut-off.
We read the same USGS gauges that underpin the bulletin. The alert phases (Overflow, Safety, Observation, Operational adjustments, Control) are the thresholds AAA publishes for each reservoir; AAA prints them in Spanish, as Desborde, Seguridad, Observación, Ajustes and Control. AAA publishes those thresholds; which band a reading falls in, and at what time, is our determination from USGS data and not an official AAA notice.
Source
Data: U.S. Geological Survey (USGS)
Provisional data
Provisional data: values are preliminary, have not been reviewed or approved by the U.S. Geological Survey, and are subject to revision or removal as the record is finalized. Do not use them for decisions involving personal or public safety, or property.
Daily reservoir level bulletin: Autoridad de Acueductos y Alcantarillados de Puerto Rico.
This portal is not an official channel of the Autoridad de Acueductos y Alcantarillados. For service notices, consult AAA.