Temperature Profiling of Waterbodies with a UAV-Integrated Sensor Subsystem

Cengiz Koparan,Calvin Sawyer,Charles Privette,Ali Bulent Koc

doi:10.3390/drones4030035

Abstract

Evaluation of thermal stratification and systematic monitoring of water temperature are required for lake management. Water temperature profiling requires temperature measurements through a water column to assess the level of thermal stratification which impacts oxygen content, microbial growth, and distribution of fish. The objective of this research was to develop and assess the functions of a water temperature profiling system mounted on a multirotor unmanned aerial vehicle (UAV). The buoyancy apparatus mounted on the UAV allowed vertical takeoff and landing on the water surface for in situ measurements. The sensor node that was integrated with the UAV consisted of a microcontroller unit, a temperature sensor, and a pressure sensor. The system measured water temperature and depth from seven pre-selected locations in a lake using autonomous navigation with autopilot control. Measurements at 100 ms intervals were made while the UAV was descending at 2 m/s until it landed on water surface. Water temperature maps of three consecutive depths at each location were created from the measurements. The average surface water temperature at 0.3 m was 22.5 °C, while the average water temperature at 4 m depth was 21.5 °C. The UAV-based profiling system developed successfully performed autonomous water temperature measurements within a lake.

Highlights

Evaluation of the physiochemical parameters of lake water is crucial for lake management and water quality monitoring
Other than the thermal stratification, water temperature can be the direct indicator of dissolved oxygen (DO), toxic absorption, and salinity [6]
The system systemdeveloped developedfor for water temperature profiling consisted of a hexacopter and a node

Summary

Introduction

Evaluation of the physiochemical parameters of lake water is crucial for lake management and water quality monitoring. Change in water temperature can trigger several phenomena in a waterbody Some of these phenomena can occur naturally, causing no harm to the aquatic system, while others can cause negative impacts on water quality. Thermal stratification occurs at a depth of 3.6 m in many lakes where layers are formed with different temperatures [1] These layers are categorized from top to bottom where the warmest layer is on the top and the coolest layer is at the bottom as the epilimnion, the thermocline, and the hypolimnion [2]. An inverse stratification, where coolest layer forms on the top while the warmer layer rests at the bottom, occurs during winter [4] This phenomenon can impact many aspects of the lake, such as spatial distribution of fish, microbial growth, and oxygen content [5]. The growth rate of algae and aquatic plants are influenced by change in temperature, where reduced DO due to increased temperature can cause harmful effects to the aquatic life [7]

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