TRÊS IRMÃOS
São Paulo · TIETE
Useful capacity
3,447.98 hm³
Coordinates
20.669°S, 51.297°W
Operator
ONS
69.8% of useful capacity
Current fill
69.8%of useful capacity
vs 7 days ago
+1.9 ppgaining
vs 1 year ago
+7.3 ppyear-over-year
7-day trend
↑rising
Drought context
Storage vs October average
107%of normal
69.8% full on 2026-10-26, against an average of 65.5% for October across 2 years of readings (+4.3 points).
Rain over the last three months · 11 October 2026
Near normal
In the three months to 11 October 2026 the area around TRÊS IRMÃOS had rain close to normal for the season. Rainfall compared with the long-run record for the same season at this point (Copernicus Global Drought Observatory, SPI-3 index +0.15). Rain, not storage. Brazil drought figures →
Catchment Weather
Past 30 days + 14-day forecast · Open-Meteo
Technical specifications
| Total capacity | 13,372 hm³ |
| Usable capacity | 3,448 hm³ |
| Primary use | Hydroelectric |
| Operator | ONS |
| River | TIETÊ |
| Province | São Paulo |
| River basin | TIETE |
Satellite imagery: Esri, Maxar, Earthstar Geographics. Map: Esri, HERE, Garmin, © OpenStreetMap contributors. 20.669°S, 51.297°W · Open in Google Maps
About TRÊS IRMÃOS
As of October 26, 2026, TRÊS IRMÃOS is at 69.8% of useful capacity, holding 2,408 hm³ of 3,448 hm³. Of the 13,372 hm³ total capacity, that is 18.0%. At this level the reservoir is within its normal operating range.
Over the most recent week on record the fill level has risen by 1.9 percentage points, and it is 7.3 points above its level on the same date a year earlier.
Across the readings we hold for TRÊS IRMÃOS — 65 data points between October 26, 2025 and October 26, 2026 — the level has ranged from a low of 56.4% (November 28, 2025) to a high of 92.8% (March 27, 2026). On average the reservoir is fullest around March and at its lowest around November.
It is operated by ONS primarily for hydroelectric power. It lies within the TIETE basin at 20.669°S, 51.297°W.
Key facts
- Current fill level
- 69.8% of useful capacity
- Water stored
- 2,408 hm³
- Total capacity
- 13,372 hm³
- Usable capacity
- 3,448 hm³
- 7-day change
- ▲ 1.9 pp
- Year-on-year
- ▲ 7.3 pp
- Primary use
- Hydroelectric power
- River
- TIETÊ
- River basin
- TIETE
- Operator
- ONS
- Coordinates
- 20.669°S, 51.297°W
- Last updated
- October 26, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 26 Oct 2026 | 69.8% | 2,408 |
| 25 Oct 2026 | 68.6% | 2,365 |
| 24 Oct 2026 | 67.3% | 2,322 |
| 23 Oct 2026 | 68.6% | 2,365 |
| 22 Oct 2026 | 68.0% | 2,343 |
| 21 Oct 2026 | 68.4% | 2,357 |
| 20 Oct 2026 | 68.0% | 2,343 |
| 19 Oct 2026 | 68.0% | 2,343 |
| 18 Oct 2026 | 68.4% | 2,357 |
| 17 Oct 2026 | 67.7% | 2,336 |
| 16 Oct 2026 | 68.6% | 2,365 |
| 15 Oct 2026 | 69.2% | 2,386 |