# A float-controlled self-contained laser gauge for monitoring river levels in tropical environments

## TL;DR

A low-cost, battery-powered water level gauge is developed for tropical environments, offering high precision and ease of use with smartphone data download.

## Contribution

A novel, low-cost, self-contained water level gauge designed for tropical conditions with no need for external power or solar panels.

## Key findings

- The gauge achieves a measurement precision of ±1 mm in controlled lab conditions.
- In field tests, it has a mean absolute error of 2.6 mm compared to a commercial device over a tropical rainy season.
- The device operates for over two months on 4 D-size batteries in remote locations.

## Abstract

•Very low cost, mechanical assembly from readily available PVC pipes, customizable to specific user needs.•No need for external power supply or solar panels.•Low power consumption and autonomy >2 months relying solely on 4x D-size batteries.•Simple to operate, direct data download on Android smartphone with Serial Bluetooth Terminal app.•Easy to maintain and repair.

Very low cost, mechanical assembly from readily available PVC pipes, customizable to specific user needs.

No need for external power supply or solar panels.

Low power consumption and autonomy >2 months relying solely on 4x D-size batteries.

Simple to operate, direct data download on Android smartphone with Serial Bluetooth Terminal app.

Easy to maintain and repair.

In this paper we present the design, construction and performance of a self-contained float-controlled water level gauge for monitoring water levels in streams and small rivers. This device is inexpensive (cost of about EUR 220), easy to build (no electronics skills or specialized tools required; assembled in a few hours) and straightforward to use. The gauge remains autonomously operational for several weeks in remote locations without the need for an external power supply or solar panel and in the harsh tropical climatic conditions. Data can be downloaded wirelessly in the field using an Android smartphone or tablet. This gauge is capable of a measurement precision of ±1 mm at temperatures ranging from 20 to 30 °C and accurate to within 2 mm of manual readings in a controlled laboratory environment. In the field, the mean absolute error (MAE) of measurements taken with the water level gauge compared to that obtained with the OTT-SE200 − a commercial float-controlled angle encoder water level gauge − over a full tropical rainy season and for a measurement range of 0.5 m, was 2.6 mm (n = 8,017).