Water Level Ground Sensors: a guide to picking up the right technology

Deploying a BWI virtual station on the same river segment as a physical water level ground sensors will immediately start providing you with water level forecasting capabilities. This is why running BWI will instantly level your existing water level physical measurement infrastructure up! 

For those of you who have not yet deployed such an infrastructure, here’s a guide on how to choose water level ground sensors. Indeed, ground sensors capable of measuring water levels come in various types, each utilizing different technologies. Each type of sensor has its advantages and limitations, and the choice depends on factors such as accuracy requirements, environmental conditions, and cost. Each technology also comes with distinct installation, maintenance, maturity, advantages, and limitations. In addition, the choice of which sensor to use depends on various factors including the specific application, environmental conditions, accuracy requirements, budget constraints, and ease of installation and maintenance. Here are some common ones in the form of a guide on how to choose your type of water level ground sensors:

1. Pressure Transducers: These water level ground sensors measure water level indirectly by sensing the pressure exerted by the water column above them. As water level increases, the pressure exerted on the sensor increases. As a consequence, this change in pressure then converts into a measurement of water level.

• Ideal for applications where accuracy is paramount and there’s a need for continuous monitoring of water levels.
• Also suitable for groundwater monitoring in wells or boreholes where direct contact with water is possible.
• Best suited for relatively stable environments where changes in atmospheric pressure and temperature can be accounted for.
• Can be used for surface water level measurements if the sensor is placed in a stilling well or housing to protect it from wave action and debris too. 
• May require additional measures to prevent damage or interference from surface disturbances.

Installation Requirements: Positioned at the base of wells or boreholes to gauge the pressure exerted by the freshwater column.

Maintenance: Minimal, occasional calibration may be necessary.

Maturity: Established and widely utilized for freshwater level measurement.

Advantages: Simple installation, consistent accuracy.

Limitations: Susceptible to fluctuations in barometric pressure, temperature, and air pockets.

 

2. Ultrasonic Sensors: Ultrasonic sensors emit high-frequency sound waves that bounce off the water surface and return to the sensor. Therefore, by measuring the time it takes for the sound wave to return, the sensor can calculate the distance to the water surface, thus determining the water level.

• Suitable for applications where non-contact measurement is preferred to avoid sensor fouling or where access to the water surface is limited.
• Ideal for monitoring water levels in open channels, tanks, or reservoirs.
• Works well in environments with minimal obstructions that could interfere with ultrasonic waves.
• Well-suited for surface water level measurements, especially in calm water bodies.
• Non-contact operation makes them ideal for open channels, lakes, and reservoirs.

Installation Requirements: Positioned above the freshwater surface with unobstructed views.

Maintenance: Regular cleaning required to prevent debris or algae buildup.

Maturity: Commonly deployed in freshwater environments.

Advantages: Contactless operation, applicable to open channels or tanks.

Limitations: Vulnerable to environmental factors like temperature and wind.

 

3. Radar Sensors: Similar to ultrasonic sensors, radar sensors emit electromagnetic waves instead of sound waves. These waves bounce off the water surface and return to the sensor, allowing it to calculate the distance to the water surface and determine the water level.

• Best suited for applications requiring high precision and resilience in harsh environmental conditions.
• Ideal for monitoring water levels in large bodies of water such as rivers, lakes, or reservoirs.
• Suitable for applications where a clear line of sight to the water surface is available and where cost is not a primary concern.
• Generally suitable for surface water level measurements, providing resilience in severe conditions.
• Suitable for deployment on bridges or shoreline structures for reliable monitoring of water levels in rivers, lakes, or coastal areas.

Installation Requirements: Mounted above water surfaces, requiring clear sightlines.

Maintenance: Routine cleaning essential for consistent performance.

Maturity: Established but potentially costlier technology.

Advantages: High precision, resilience in adverse conditions.

Limitations: Elevated cost, possible complexity.

 

4. Capacitance Sensors: Capacitance sensors measure changes in capacitance between electrodes as the water level changes. When water covers the electrodes, the capacitance increases, and this change determines the water level. 

• Suitable for applications where direct contact with the water is feasible, such as groundwater monitoring in wells or boreholes.
• Ideal for environments where soil composition changes are minimal and temperature fluctuations are moderate.
• Also, offers good accuracy and reliability for continuous monitoring of water levels.
• Not typically recommended for surface water level measurements due to their design, which requires direct contact with the water.
• May not withstand the dynamic conditions and debris present in surface water environments.

Installation Requirements: Buried or installed in stilling wells for direct contact with freshwater.

Maintenance: Periodic cleaning to prevent sensor fouling.

Maturity: Widely adopted for continental freshwater monitoring.

Advantages: Reliable accuracy, straightforward installation.

Limitations: Sensitive to soil composition variations and temperature fluctuations.

 

5. Resistive Sensors: Resistive sensors measure changes in electrical resistance caused by the presence of water. As the water level increases, the resistance between two electrodes changes, allowing the sensor to determine the water level.

• Similar to capacitance sensors, resistive sensors are suitable for applications where direct contact with the water is possible.
• In addition, a cost-effective option for groundwater monitoring in wells or boreholes.
• Further, works well in environments with stable soil conditions and controlled temperature variations.
• Similar to capacitance sensors, resistive sensors are not usually suitable for surface water level measurements due to their need for direct contact with the water.
• Also, maybe susceptible to damage from surface disturbances and debris.

Installation Requirements: Buried or installed in stilling wells, requiring direct contact with freshwater.

Maintenance: Regular cleaning to maintain accuracy.

Maturity: Commonly employed in freshwater monitoring.

Advantages: Cost-effective, consistent accuracy.

Limitations: Susceptible to soil composition changes and temperature variations.

 

6. Acoustic Sensors: Acoustic sensors use sound waves to directly measure the depth of water. These sensors emit sound pulses that travel through the water and reflect off the bottom. By measuring the time it takes for the pulse to return, the sensor can calculate the water depth.

• Ideal for applications where accurate measurements of water depth in dynamic environments are required, such as rivers, estuaries, or coastal areas.
• Suitable for monitoring water levels in areas with significant wave action or currents.
• Provides reliable measurements even in challenging environmental conditions.
• Ideally suited for surface water level measurements, including in situations with waves and currents.
• Further, can provide accurate depth measurements in rivers, estuaries, and coastal areas, where other sensors may struggle.

Installation Requirements: Deployed in freshwater bodies with stable mounting and anchoring.

Maintenance: Frequent inspection and cleaning to prevent fouling.

Maturity: Well-established for freshwater depth measurement.

Advantages: Accurate measurements in dynamic environments.

Limitations: On the contrary, vulnerable to noise interference from external sources.

 

7. Hydrostatic Sensors: Hydrostatic sensors measure water pressure at a specific depth underground. By comparing this pressure to a reference point, typically atmospheric pressure, the sensor can determine the water level.

• Suitable for applications requiring long-term stability and reliable accuracy, such as groundwater monitoring or tank level measurement.
• Ideal for installations where the sensors are submerged at a specific depth in a well or borehole.
• Works well in environments with stable atmospheric pressure conditions and sufficient water column depth.
• Also, can be used for surface water level measurements if submerged at an appropriate depth in the water body.
• Typically deployed in stilling wells or housings to protect the sensor and ensure accurate readings.

Installation Requirements: Submerged at specific depths in wells or boreholes, requiring stable positioning.

Maintenance: Minimal, periodic calibration recommended.

Maturity: Widely utilized for continental freshwater level monitoring.

Advantages: Reliable accuracy, long-term stability.

Limitations: On the contrary, affected by atmospheric pressure changes, requires adequate water column depth.

 

All in all, the selection of a specific sensor depends on the unique requirements and conditions of each monitoring application. Thus, it’s essential to carefully evaluate the advantages and limitations of each technology before making a decision to deploy. Indeed, not all of the mentioned sensors are equally suitable for surface water level measurements in particular – which is what BWI clients are mostly interested in.

Ultrasonic sensors and radar sensors are the most commonly used for surface water level measurements due to their non-contact operation and resilience in dynamic environments. Acoustic sensors are also well-suited for surface water monitoring, especially in areas with significant wave action or currents. Other sensors, such as pressure transducers and hydrostatic sensors, can be adapted for surface water level measurements with proper installation and protection from surface disturbances. Once your physical ground sensors are deployed, come to BWI to supercharge your water level monitoring infrastructure with virtual station-powered water level forecasting capabilities!