Frequently Asked Questions

HidroAlerta24 is an independent informational early-warning system for floods. It aggregates public data from multiple official and open sources to deliver a unified, real-time view of hydrological risk in Spain.

The system combines weather forecasts, river and reservoir levels, radar imagery, lightning detection, and official alerts in a single interactive map, making it easier to understand the hydrological situation at any moment.

No. HidroAlerta24 is an independent, informational project. It is not affiliated with any government agency.

For official alerts, always consult:

• AEMET – Spain's State Meteorological Agency
• Civil Protection – alerts and emergency plans

The data shown on HidroAlerta24 is indicative and does not replace official sources.

HidroAlerta24 aggregates information from multiple data sources:

• Open-Meteo – Weather forecasts, river flow rates, snow, and air quality
• OpenWeatherMap – Current weather data and official alerts
• SAIH network – Real-time levels and flow rates provided by the Hydrographic Confederations
• RainViewer – Precipitation radar imagery
• Blitzortung – Real-time lightning detection

Update frequency depends on each data source:

• Current weather data: every 10–20 minutes
• Reservoirs: every hour
• Radar imagery: every 5–10 minutes
• Weather forecasts: every 20 minutes
• Air quality: every 30 minutes

Times are approximate and may vary depending on availability and load on the original sources.

Yes, HidroAlerta24 is completely free, ad-free, and requires no registration to use the live map and access all system features.

HidroAlerta24 uses a four-level color-coded alert system:

• Green – Normal situation, no significant risk. Flow rates and rainfall levels are within usual parameters.
• Yellow – Caution. Possible heavy rain or moderately rising flow rates. Stay informed.
• Orange – Significant danger. Likely flooding that may affect flood-prone areas. Avoid streams and gullies.
• Red – Extreme danger. Severe flooding imminent or in progress. Immediately follow Civil Protection instructions.

Thresholds are based on accumulated rainfall, current and forecast flow rate, and river level relative to reference values.

Click the "Subscribe" button in the application header. In the form you can:

• Choose the minimum alert level you want to receive (yellow, orange, or red)
• Select the regions or basins of interest

You will automatically receive an email when an alert is activated in your selected area. You can change your preferences or unsubscribe at any time.

Yes. HidroAlerta24 works as a Progressive Web App (PWA). You can install it directly from your mobile browser:

• On Android (Chrome): tap "Add to Home screen" in the browser menu
• On iOS (Safari): tap the share button and select "Add to Home Screen"

If your device supports push notifications, you'll be able to receive alerts when warnings are activated in your areas of interest.

If you receive a red alert, act with maximum urgency:

• Immediately follow instructions from Civil Protection and 112
• Stay away from streams, gullies, rivers, and flood-prone areas
• Do not cross flooded areas by vehicle or on foot — just 6 inches (15 cm) of moving water can knock down a person
• Move to higher ground and seek shelter on upper floors of solid buildings
• Stay informed through official sources and stay away from basements and underground garages

See our complete emergency preparedness guide for more tips.

A reservoir is a body of water artificially retained by a dam. Its level is critical for flood management for one fundamental reason: flood routing.

The available free volume in the reservoir (called freeboard) determines how much flood water it can absorb before being forced to release water. When a reservoir is nearly full, its capacity to protect downstream populations is drastically reduced.

HidroAlerta24 monitors 117 reservoirs around the world so you can check their status in real time. Read more in our article on reservoirs and dam safety.

Flow rate is the volume of water passing a given point of a river per unit of time. It is expressed in cubic meters per second (m³/s).

It is measured by gauging stations using different technologies:

• Stage gauges: measure water level and convert it to flow rate using calibrated rating curves
• Ultrasonic sensors: measure flow velocity beneath the water surface
• Stage-discharge relationships: mathematical formulas calibrated for each specific river reach

These stations are part of the SAIH network, which transmits real-time data to the Hydrographic Confederations.

Yes. In the sidebar of the application you'll find buttons to export the data in several formats:

• CSV – For spreadsheets (Excel, Google Sheets)
• JSON – For programmatic processing
• PNG – Visual snapshot of the map and data

The data exported reflects the basins, reservoirs, and alerts visible at the moment of download.

No. The data shown on HidroAlerta24 is indicative. It may have:

• Errors in the original sensor measurements
• Delays in data transmission or updates
• Occasional failures of sensors or gauging stations

For decisions affecting your safety, always cross-check with official sources such as AEMET and the Hydrographic Confederations.

HidroAlerta24 is compatible with recent versions of the major browsers:

• Google Chrome (recommended)
• Mozilla Firefox
• Microsoft Edge
• Apple Safari

It works as an installable PWA on both Android and iOS. For the best experience, we recommend a screen at least 360 pixels wide.

Partially. The service worker caches the application interface for fast loading even on slow connections. However, real-time data (weather, flow rates, reservoir levels, alerts, and radar) requires an internet connection to update.

If you lose connection, you'll be able to see the last loaded information but won't receive updates until network access is restored.