Water Watch Review: 26 Days of Metro Rationing, by the Numbers

26 days into the San Juan metro water rotation plan (interruptions paused since September 2, plan still in force): Carraízo up 139 cm, La Plata down 179 cm since August 8, on AAA’s own 5:00 AM charts. The numbers first, then what they add up to.

At a glance

Carraízo, day by day

Three reservoirs, one scale

What it adds up to

What changed the picture over these 26 days was the rain that finally landed at the very end of the window. Carraízo spent most of the rotation sliding — 18 falling mornings against just 6 rises — before a single +172 cm jump on September 2, following 1.14 in of rain the day prior, pushed it up 139 cm net into observación, now 0.42 m above the ajustes line. Cidra barely moved net (up just 4 cm since August 8), but it also caught the same late rain, logging three straight rising mornings and sitting 1.80 m above the control line. La Plata saw comparable rainfall — 2.13 in over the final week — but it did not respond the same way: it kept falling, 23 down days out of 24, down 179 cm since the rotation began, now 4.09 m above control and still dropping at roughly 7.5 cm a day.

So the rain helped two of three reservoirs, not all three. Carraízo and Cidra are both now rising and, arithmetically, on pace to cross into the next band above within days if the pace holds. La Plata shows no such response and remains on a steady downward path toward control, arithmetically many weeks off at the current rate.

Numbers from AAA’s Monitoreo Diario charts, read each morning for our reservoir board; rain from USGS gauges within 12 km of each reservoir (a proximity proxy, not a basin measurement). Rates and pace dates are arithmetic over the stored readings, not forecasts. The narrative is drafted by Claude from the computed figures and checked number-by-number against them before publishing.