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River level monitoring with IoT

The ability to remote monitor river levels is possible with IoT technology. IoT allows you to monitor river levels in multiple locations accurately, and the data can be transmitted back wirelessly in real-time. In this blog post, we look at the different components and sensors required to monitor river levels.

Libelium Smart Cities
Ultrasonic sensor fitted to the Libelium Plug&Sense

The two most common sensors that are used to measure river levels with IoT are ultrasonic sensors and depth sensors. In this post, we are going to focus on the use of the ultrasonic sensor.

To provide a simple explanation, we have broken the solution into Sensors, Network and Cloud.

  • Sensors – Libelium Plug&Sense (Smart Water Xtreme or Smart Cities), with the Ultrasonic Sensor (Maxbotix MB7040)
  • Network – The Libelium Plug&Sense supports LoRa, 3G/4G, Sigfox, WiFi and Zigbee/XBee. For remote locations, there is also the option of using a LoRa-Satellite gateway.
  • Cloud – A range of cloud platforms are supported. The most common platforms that we work with include Microsoft Azure, AWS, in addition to custom web applications and conventional database systems.


Libelium Plug&Sense sensor node allows you to connect a variety of sensors (up to six). For this scenario, we will be connecting the Maxbotix ultrasonic sensor. For river applications,  you may also want to include temperature, humidity and pressure, a weather station and even a water-flow-meter.

An ultrasonic sensor works by emitting sound toward an object and detecting the sound reflecting. The sensor then measures the time between each point to determine the distance between the sensor and the object being measured. The sound emitted by the sensor is at a high frequency, inaudible to the human ear, but it allows for a focused ‘beam’ (42KHz).

The Maxbotix I2CXL can detect the distance of an object at a range of up to 10m, with a 1cm granularity.

How do I power the sensor?

The Libelium Plug&Sense includes a built-in 6000mA-H battery and support for an external solar panel. The use of batteries and renewables allows the sensor nodes to be deployed in remote environments.


Smart Water
The Libelium Plug & Sense Smart Water has dozens of sensors to detect chemicals, turbidity and the presence of metals.

Wireless technologies such as LoRa, WiFi, 3G/4G and Sigfox are all supported by the Libelium Plug & Sense.  The flexible range of options allows you to choose the right wireless technology to send data back to your systems or application servers. For very remote locations, a technology such as LoRa (supported by the node) and a LoRa-Satellite gateway, allows water monitoring from any location in the world!


Data from the sensors (once transmitted) needs to be processed and stored. The use of cloud platforms such as Microsoft Azure is perfect for IoT. However, the platform supports sending data to Azure, AWS and familiar application/database servers. Once in the cloud, you can develop additional functionality such as alerting and notifications (i.e. if the river level exceeds a given level, or there is an upwards/downwards trend of significance).


The Sensor node is attached to a river structure such as a bridge or installed on a pole adjacent to the river that needs to be monitored. The Ultrasonic sensor is connected to the node and installed above the body of water. At this point, the sensor will be measuring the distance between itself and the body of water.

At this point, if you know the depth of the river at this point – any increase or decrease in the sensor value (i.e., 25cm) would indicate a reduction in water levels, while any increase (+15cm) would suggest an increase in water levels.

Ultrasonic Probe for River Monitoring
The node is installed on the bridge with the ultra-sonic sensor pointing towards the river. The sensors measure the distance between the sensor and the river to an accuracy of 1cm. These measurements are then used to assess the height of the river. The sensors work at a range of up to 7.6m (10m in the extended version). Data is then transmitted using LoRa/4G/3G/WiFi/Sigfox.

Sampling Intervals

The sensor node (Libelium Plug&Sense) will then transmit this measurement back to the cloud platform. Measurement intervals can be as little as a few seconds, but a practical range would be every 15 minutes. For higher-risk rivers or where pre-emptive flood detection is needed – you may want to measure levels every minute.

The only disadvantage of more aggressive sampling intervals is on the battery life of the sensor node.  More measurements mean more power consumption – an important consideration if the sensor node is being powered from the battery and solar.

Alert and notifications

Once the data is in a cloud platform, applications can be developed that do the following:

  • Visualise the water-level data on a dashboard.
  • Send text messages when water levels exceed a given value.
  • Generate alerts (text or e-mail) when the water levels increase at a given gradient.
  • Send messages via Slack, Microsoft Teams or WhatsApp when thresholds are exceeded.
  • Combine reports with weather data, to understand the correlation and risk factors associated with water levels and weather.

What else can I monitor?

In addition to water levels, we can monitor a wide range of parameters associated with water such as pH, ORP, Dissolved Oxygen, BOD/COD and conductivity. To learn more, review the following blog posts:


IoT is an excellent solution for remote monitoring river levels in a high accuracy manner. Ultrasonic sensors and the Libelium Plug&Sense offers a field-proven and reliable solution that supports a range of communications technologies. If you would like to speak to our team about IoT river monitoring solutions or any other smart water application, please get in touch.

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Joe Hughes is the CEO of Manx Technology Group. Joe has a background in software development, information security, networks, datacentres and enterprise IT.

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