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Reservoirs

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

Where they stand now

The newest reading was taken at 6:45 AM; each reservoir shows its own.

3 are in Operational adjustments: Carraízo, La Plata, and Cidra.

19 of 19 reservoirs reporting

The 19 reservoirs

The 19 reservoirs on August 31, 2026.

Showing 19 of 19 reservoirs

Filter and sort

Phase
Percent of range0% – 100%
24-hour change-1.00 – +1.00 m

Each figure is the reservoir seen from the side: the water rises to the measured level and the crest is drawn at the overflow point. The phase lines sit at the same height on every card, so the water is what moves and one reservoir can be compared with another. Ordered from least margin to most.

  1. Río Blanco

  2. Toa Vaca

  3. Cidra

  4. Fajardo

  5. Matrullas

  6. Carraízo

  7. Lucchetti

  8. La Plata

  9. Guayo

  10. Guayabal

  11. Loco

  12. Patillas

  13. Cerrillos

  14. Carite

  15. Caonillas

  16. El Guineo

  17. Guajataca

  18. Dos Bocas

  19. Garzas

The same data as the chart, as a table. Phase and percent are from the most recent reading; the 24-hour change is measured between bulletins.
ReservoirPhaseMost recent level5:00 AM bulletin levelPercent of range24-hour change
Río BlancoObservation24.50 m24.49 m51%+0.20 m
Toa VacaSafety147.11 mNo data59%0.00 m
CidraOperational adjustments400.06 mNo data61%+0.04 m
FajardoObservation46.40 mNo data63%+0.16 m
MatrullasSafety733.16 m733.16 m64%+0.04 m
CarraízoOperational adjustments37.15 m37.14 m65%+0.07 m
LucchettiSafety170.99 m170.99 m67%-0.01 m
La PlataOperational adjustments44.66 m44.66 m69%-0.05 m
GuayoSafety442.72 m442.72 m72%+0.05 m
GuayabalObservation102.50 m102.50 m74%+0.11 m
LocoObservation69.32 m69.33 m74%-0.05 m
PatillasSafety63.38 m63.36 m79%+0.05 m
CerrillosSafety167.26 m167.26 m80%0.00 m
CariteSafety541.71 m541.70 m89%+0.02 m
CaonillasSafety250.53 mNo data91%+0.05 m
El GuineoSafety901.53 m901.53 m92%+0.04 m
GuajatacaSafety195.89 m195.89 m95%+0.02 m
Dos BocasSafety89.68 m89.68 m97%+0.02 m
GarzasSafety736.06 m736.07 m100%+0.02 m

No mode compares heights between reservoirs. Every reservoir is read against its own thresholds.

Colour is never the only signal: the phase is written beside it in every mode.

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.

Selected by: the lowest percentile against normal, among reservoirs with 15 or more years of record

Largest 24-hour fall

Loco

-0.05 m

Selected by: the most negative 24-hour change in v_latest

Largest 24-hour rise

Río Blanco

+0.20 m

Selected by: the most positive 24-hour change in v_latest

AAA alert phases

  • Overflow — At capacity; the excess leaves over the spillway.
  • Safety — Normal operating level.
  • Observation — Below the safety mark; under monitoring.
  • Operational adjustments — AAA reduces withdrawal to stretch the reserve.
  • Control — Critical level.
  • Out of service — Below the point of reliable withdrawal.

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.