San Juan
Community of Madrid · Tajo
Capacity
138 hm³
Coordinates
40.377°N, 4.320°W
Operator
CHT
51.4% full
Current fill
51.4%vs 7 days ago
-1.5%losing
vs 1 year ago
-8.0%year-over-year
7-day trend
→stable
Catchment Weather
Past 30 days + 14-day forecast · Open-Meteo
Technical specifications
| Total capacity | 138 hm³ |
| Usable capacity | 124.2 hm³ |
| Primary use | Multi-purpose |
| Operator | CHT |
| Autonomous community | Community of Madrid |
| River basin | Tajo |
Satellite imagery: Esri, Maxar, Earthstar Geographics. Map: Esri, HERE, Garmin, © OpenStreetMap contributors. 40.377, -4.320 · Open in Google Maps
About San Juan
As of October 6, 2026, San Juan is filled to 51.4% of its total capacity, holding roughly 71 hm³ of water out of a maximum 138 hm³. At this level the reservoir is within its normal operating range. Of that total, about 124 hm³ is usable (live) storage.
Over the most recent week on record the fill level has held broadly steady (-1.5 pts), and it is 8.0 points below its level on the same date a year earlier.
Across the readings we hold for San Juan — 418 data points between October 9, 2018 and October 6, 2026 — the level has ranged from a low of 16.7% (November 19, 2019) to a high of 92.8% (May 21, 2024). On average the reservoir is fullest around May and at its lowest around November.
It is operated by CHT primarily for multiple purposes. It lies within the Tajo basin at 40.377°N, 4.320°W.
Key facts
- Current fill level
- 51.4%
- Water stored
- 71 hm³
- Total capacity
- 138 hm³
- Usable capacity
- 124 hm³
- 7-day change
- ▼ 1.5 pts
- Year-on-year
- ▼ 8.0 pts
- Primary use
- Multipurpose
- River basin
- Tajo
- Operator
- CHT
- Coordinates
- 40.377°N, 4.320°W
- Last updated
- October 6, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 6 Oct 2026 | 51.4% | 71 |
| 29 Sep 2026 | 52.9% | 73 |
| 22 Sep 2026 | 55.1% | 76 |
| 15 Sep 2026 | 57.2% | 79 |
| 8 Sep 2026 | 62.3% | 86 |
| 1 Sep 2026 | 65.9% | 91 |
| 25 Aug 2026 | 71.0% | 98 |
| 18 Aug 2026 | 76.1% | 105 |
| 11 Aug 2026 | 81.9% | 113 |
| 4 Aug 2026 | 82.6% | 114 |
| 28 Jul 2026 | 82.6% | 114 |
| 21 Jul 2026 | 83.3% | 115 |