Reservoirs

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.