Measuring borehole water levels with Aquatara.

Aquatara measures the depth to the water surface in a borehole using sound. A small device with a speaker and a microphone sits on the borehole collar and connects to an Android phone over USB. The Aquatara app sends a short sound pulse down the borehole, records the echo reflected from the water surface and calculates the distance from the collar to the water.

Every measurement is stored on the phone together with the borehole it belongs to, the time, the operator and the recorded waveform, and can be sent by email for reporting.

When you trigger a measurement, the speaker emits a 2 ms tone burst at 1 kHz while the microphone records. The microphone first picks up the outgoing pulse itself, then the echo returning from the water surface. The app finds these two peaks in the recording and measures the time between them, Δt. Because the sound travels down and back up, the distance to the water is

distance = Δt × c / 2

where c is the speed of sound in the air inside the borehole. The speed of sound depends on air temperature, so the temperature used in the calculation directly affects the result — a 1 °C error changes the measured distance by roughly 0.17 %, or about 17 cm at 100 m. This is why Aquatara lets you calibrate the temperature for each borehole.

• The Aquatara device, charged.
• An Android phone with a USB-C port (or a USB OTG adapter) and the Aquatara app installed.
• For calibration: a dip meter or tape to measure the water level by hand at least once per borehole.
• Optionally, an email app on the phone for sending readings.

The device has no buttons of its own — every measurement is started from the app. Check the battery indicator on the device before going to site.

• The current version is designed for water levels of 8 m and deeper. Calibration requires a dipped distance of at least 8 m.
• Accuracy depends on the temperature used in the calculation. Without calibration the app uses the default temperature from the settings (15 °C unless changed).
• Obstructions in the borehole (pump, cables, joints, changes in diameter) and loud background noise can produce additional reflections. Check the received pulse chart when a result looks wrong.

Install the Aquatara app on your Android phone using the installation link provided by Aquatara. The app asks for two permissions:

• Microphone — required. Without it no measurement or calibration is possible.
• Location — optional. Used only to fill in borehole coordinates from the phone's GPS.

1. Plug the Aquatara device into the phone's USB port.
2. Android may ask whether to open Aquatara for this USB device. Confirm — you can tick Always so the app opens automatically next time.
3. The app shows a short Device connected message. The indicator in the top right corner of every screen turns green and shows a USB icon.

If the cable is unplugged, the app shows Device disconnected and the indicator changes to a grey, crossed-out USB icon. Always check the indicator before triggering a measurement — without the device the phone would use its own speaker and microphone and the result would not be meaningful.

Before the first measurement, open Default settings and fill in at least:

1. Units — distance (m, ft or yd) and temperature (°C, °F or K). All values in the app are entered and shown in these units.
2. Operator — your name. It is stored with every reading you save.
3. Organization and Default email to send measurement — used when readings are shared by email.
4. Default temperature — a typical air temperature in boreholes in your region (see Why calibration matters for regional values).
5. Default measurement range — the range of water levels you expect.

Tap Save at the bottom of the screen. All settings are described in the Settings reference.

The app converts the echo time into distance using the speed of sound, which depends on the air temperature inside the borehole. That temperature is often different from the air temperature at the surface and varies by region — see Why calibration matters.

Calibration works backwards: you measure the water level once by hand, Aquatara measures the echo time, and the app calculates the temperature that makes the two agree. This calibrated temperature is saved with the borehole and used for later measurements there.

Calibrate a borehole:

• before the first measurement at that borehole;
• when conditions change significantly, e.g. between seasons;
• whenever a manual dip check disagrees with Aquatara readings.

• The device is charged and the indicator in the app shows it is connected.
• The phone is not muted. The app raises the media volume to at least 50 % automatically, but cannot override mute.
• The device sits on the collar, pointing vertically down into the borehole.
• The surroundings are as quiet as possible — running engines, pumps and wind can mask the echo.

The chart shows the amplitude of the recorded sound over time. Two red vertical lines mark the peaks the app used: the first is the outgoing pulse, the second is the echo from the water surface. The distance between the two lines corresponds to the measured water level.

In a good measurement the two peaks clearly rise above the rest of the signal. If the second line sits on a small bump among many similar ones, or the chart shows several strong peaks, the app may have picked the wrong reflection — adjust From / To and repeat the measurement.

The horizontal axis can show time in milliseconds or distance (with zero at the first peak) — see Chart abscise axis label in the settings.

After a successful measurement the main button changes to Save measurement. Tap it to store the reading. The reading is saved with the borehole name, time, the operator name from the default settings, the borehole coordinates and the recorded waveform.

To repeat a measurement instead of saving it, go back to the borehole and tap Take measurement again.

1. In a readings list, tap Select readings, then tap the readings you want to send. Tap View readings to leave selection mode.
2. Tap Share. For a single reading, use Send via email on its details screen.
3. If a preferred email app is set in the settings, or only one email app is installed, it opens directly. Otherwise choose an app and whether to use HTML formatting.
4. Review the prepared email in your email app and send it.

The prepared email contains:

• recipient: the default email from the settings; subject: “Aquatara readings”;
• the readings grouped by borehole and sorted by time, each with recording time, measured depth, temperature assumed, operator and notes;
• a signature with the operator name and organization;
• the recorded waveform of each reading as a .wav attachment.

Collar

The top of the borehole casing. All Aquatara distances are measured from here.

Below collar

Measured distance from the collar down to the water surface.

Dipped distance

Distance to the water measured by hand with a dip meter or tape.

Casing

The pipe lining the borehole, typically steel or PVC.

Pulse

The short tone burst emitted by the device to start a measurement.

Echo

The part of the pulse reflected back from the water surface.

Peak

A local maximum in the recorded signal. The app uses the first two peaks above half of the maximum amplitude.

Peak magnitude

Height of a peak relative to the loudest point of the recording (0–1).

Confidence (rms)

Magnitude of the first detected peak divided by the RMS level of the whole recording. Higher values mean the peak stands out more clearly.

Speed of sound

Calculated from the selected temperature; converts echo time to distance.

Calibrated temperature

Air temperature derived from a calibration and saved with the borehole.

Default temperature

Air temperature from the settings, used when no calibration is available.

Measurement range

From / To distances that limit where the app looks for the echo and how long it records.