--- title: "Water Level / Depth Sensors & Monitoring | Aethair" description: "Water level is the height of a water surface above a fixed datum. How it is measured and logged for flood, river, and groundwater monitoring." url: https://aethair.io/parameters/water_level/ --- Measurements · Fluid / Level / Flow # Water Level / Depth Also known as water depth, stage height, level sensor Water level / depth (pressure- or acoustic-derived). [Schedule a call](https://calendly.com/d/ctdd-mkr-v9v/aethair-demo-website) [Configure Water Level / Depth Monitoring](https://aethair.io/build/?params=water_level) At a glance m Fluid / Level / Flow 1 way to measure it - **Thiamis** 6 external instruments What it is ## What is water level? Water level, or depth, is the height of a water surface, usually expressed in meters relative to a fixed reference datum. In rivers and channels it is called **stage**; in wells it is the depth to the water table; in reservoirs and tanks it is the fill height. Whatever the setting, it is the elevation of the surface above an agreed zero, and because that zero is arbitrary, a level reading is only meaningful once its datum is defined. Water level is one of the most fundamental hydrological measurements: it is easy to log continuously, responds directly to rainfall, abstraction, and tides, and forms the basis for deriving flow through a known relationship between stage and discharge. Because it is simple, dependable, and continuously loggable, water level is the backbone parameter of hydrology, flood warning, and groundwater monitoring. In flood management, water level is the primary early-warning signal: a rising stage at an upstream gauge gives the time needed to alert communities and close flood barriers before a river tops its banks. In hydrology and water withdrawal, level drives the flow estimates that permits and water balances depend on. In groundwater, it tracks the health of an aquifer, revealing over-pumping, recharge, and the influence of nearby wells. In reservoirs, tanks, and treatment works it governs storage, safety, and process control. For hydrologists, water utilities, regulators, and site operators, water level is therefore a control and safety variable, watched continuously with alarms because its rate of change is often as important as its value. How it is measured ## How Water Level / Depth Is Measured Several professional sensors are used, all logged on a Thiamis gateway for continuous measurement. A **submersible pressure transducer** sits below the surface and derives depth from the water pressure above it. It is vented to the atmosphere so that barometric changes are canceled. **Ultrasonic** and **radar** sensors mount above the water and measure the distance down to the surface without touching it, which suits corrosive, dirty, or debris-laden water. Each is referenced to the site datum, and pressure sensors in particular need that referencing and periodic checks against a manual dip to counter drift. An instrument on Thiamis 6 A third-party instrument connected to a Thiamis gateway, reporting into the same Environet account. ### Placing water level sensors Level is measured at a representative, hydraulically stable point (often within a **stilling well** or against a staff gauge), away from turbulence, eddies, and the direct plunge of inflows that would make the surface jump. Pressure transducers are secured at a known, fixed elevation so their datum stays constant; non-contact ultrasonic and radar sensors are mounted clear above the highest expected level with an unobstructed view of the surface. The location is chosen so that the measured level genuinely represents the water body and, where flow is to be derived, corresponds to the point the stage-discharge relationship was built for. ### Every device and option that measures Water Level / Depth 6 | Device / option | Type | Base platform | Measures | | - | - | - | - | | [YSI](https://aethair.io/sensors/ysi-water-quality-sondes/) · EXO1, EXO1S, EXO2… | Water Quality Sondes | Thiamis | Water Level / Depth [Dissolved Ammonia (NH₃)](https://aethair.io/parameters/ammonia/) [Ammonium (NH₄)](https://aethair.io/parameters/ammonium/) [Blue-Green Algae](https://aethair.io/parameters/bga/) [Chloride](https://aethair.io/parameters/chloride/) [Chlorophyll](https://aethair.io/parameters/chlorophyll/) [Conductivity](https://aethair.io/parameters/conductivity/) | | [In-Situ](https://aethair.io/sensors/in-situ-water-quality-sondes/) · Level TROLL 300, Level TROLL 400, Level TROLL 500… | Water Quality Sondes | Thiamis | Water Level / Depth [Dissolved Ammonia (NH₃)](https://aethair.io/parameters/ammonia/) [Ammonium (NH₄)](https://aethair.io/parameters/ammonium/) [Blue-Green Algae](https://aethair.io/parameters/bga/) [Chloride](https://aethair.io/parameters/chloride/) [Chlorophyll](https://aethair.io/parameters/chlorophyll/) [Conductivity](https://aethair.io/parameters/conductivity/) | | [Eureka Water Probes](https://aethair.io/sensors/eureka-water-probes-water-quality-sondes/) · Manta+ 20, Manta+ 25, Manta+ 30… | Water Quality Sondes | Thiamis | Water Level / Depth [Dissolved Ammonia (NH₃)](https://aethair.io/parameters/ammonia/) [Ammonium (NH₄)](https://aethair.io/parameters/ammonium/) [Chloride](https://aethair.io/parameters/chloride/) [Chlorophyll](https://aethair.io/parameters/chlorophyll/) [Dissolved CO₂](https://aethair.io/parameters/dissolved_co2/) [Dissolved Oxygen](https://aethair.io/parameters/do/) | | [Temposonics](https://aethair.io/sensors/temposonics-water-level-flow/) · TankSLAYER, RefineME, SoCLEAN… | Water Level & Flow | Thiamis | Water Level / Depth [Volume (totalized)](https://aethair.io/parameters/volume/) [Water Temperature](https://aethair.io/parameters/water_temperature/) | | [Spectra Scientific](https://aethair.io/sensors/spectra-scientific-water-quality-sondes/) · Spectra Litmus 6, Spectra Litmus 4 | Water Quality Sondes | Thiamis | Water Level / Depth [Dissolved Ammonia (NH₃)](https://aethair.io/parameters/ammonia/) [Ammonium (NH₄)](https://aethair.io/parameters/ammonium/) [Blue-Green Algae](https://aethair.io/parameters/bga/) [Chloride](https://aethair.io/parameters/chloride/) [Chlorophyll](https://aethair.io/parameters/chlorophyll/) [Conductivity](https://aethair.io/parameters/conductivity/) | | [YSI](https://aethair.io/sensors/ysi-water-quality-sondes/) · 6600 V2, 6600EDS V2, 6920 V2… | Water Quality Sondes | Thiamis | Water Level / Depth [Dissolved Ammonia (NH₃)](https://aethair.io/parameters/ammonia/) [Ammonium (NH₄)](https://aethair.io/parameters/ammonium/) [Blue-Green Algae](https://aethair.io/parameters/bga/) [Chloride](https://aethair.io/parameters/chloride/) [Chlorophyll](https://aethair.io/parameters/chlorophyll/) [Conductivity](https://aethair.io/parameters/conductivity/) | [Configure Water Level / Depth Monitoring](https://aethair.io/build/?params=water_level) Where it is monitored ## Solutions That Monitor Water Level / Depth Each one links to the solution page showing what that industry measures it for. ### [Hydrology, Level & Flow](https://aethair.io/solutions/hydrology/#measure-water_level) Core parameter Water level is the backbone measurement of hydrology, underpinning flood warning, stream gauging, reservoir operation, and groundwater management. ### [Water Quality Monitoring](https://aethair.io/solutions/water-quality/) Often added Rivers, lakes, drinking water, and stormwater Related ## More in Fluid / Level / Flow [Water Pressure](https://aethair.io/parameters/water_pressure/) [Volume (totalized)](https://aethair.io/parameters/volume/) [Flow Rate](https://aethair.io/parameters/flow/) [Fluid Differential Pressure](https://aethair.io/parameters/differential_pressure_fluid/) [Fluid Particle Count (ISO 4406)](https://aethair.io/parameters/particle_count_fluid/) [Velocity](https://aethair.io/parameters/velocity/) Questions ## Water Level / Depth FAQ How is water level measured without floats? Modern gauges use submersible pressure transducers, which sense the pressure of the water column above them, or non-contact ultrasonic and radar sensors mounted above the surface, which measure the distance down to it. Pressure sensors are vented to cancel barometric changes, while radar and ultrasonic avoid contact with dirty or corrosive water. What is the difference between stage and discharge? Stage is the water level (the height of the surface above a datum), while discharge is the volumetric flow rate passing the site. They are linked by a site-specific stage-discharge rating, so a continuously measured level can be converted into a continuous flow once that relationship is established. Why does the datum matter? Because water level is a height relative to an arbitrary zero, a reading is meaningless unless that zero is defined and kept constant. Referencing every gauge to the same datum is what lets levels be compared over time and between sites, and what keeps a relocated or serviced sensor consistent. How do I monitor water level? Pair a Thiamis gateway with a vented pressure transducer, or an ultrasonic or radar sensor, referenced to your site datum for continuous level logging with alarms. Use the configurator to combine water level with flow, velocity, and volume for a complete hydrological or hydraulic monitoring station.