An open-source and low-cost data acquisition system for surface water monitoring: analysis of measurement uncertainty

Agricultural activities are strongly dependent on the availability of water resources, despite this, little is known about local water availability. This is due to the high acquisition cost and difficult sensors handling. This article aims to assess low-cost equipment (sensor and datalogger) capable of monitoring the water level in dams and rivers based on the Arduino platform. For this purpose, the following were used: Ultrasonic sensors HC-SR04 and DHT11 for humidity and temperature. The data was stored on a micro SD card integrated into the Arduino nano. The total cost was $17.98 (dollars). The equipment was calibrated from 0.1 to 4.0 m in length and considering surface inclinations of 0, 5, 10 and 15° in relation to the horizontal. The results show that there was a tendency to underestimate the data in relation to the distribution of errors and an acceptable error of less than 0.04 m can still be considered for all slopes and distances evaluated. The ultrasonic sensor must be installed perpendicular to the target surface, as using a single calibration for various inclinations results in overestimated measurements. The equipment proved to be viable and low-cost for monitoring water levels in dams and rivers.