Abstract
Water losses from water distribution means have a high environmental impact in terms of natural resource depletion (water, energy, ecosystems). This work aims to develop an optical airborne surveillance service for the detection of water leaks (WADI—Water-tightness Airborne Detection Implementation) to provide water utilities with adequate and timely information on leaks in water transportation mains outside urban areas. Firstly, a series of measurement campaigns were performed with two hyperspectral cameras and a thermal infrared camera in order to select the most appropriate wavelengths and combinations thereof for best revealing high moisture areas, which are taken as a proxy for water leakage. The Temperature-Vegetation-Index method (T-VI, also known as Triangle/Trapezoid method) was found to provide the highest contrast-to-noise ratio. This preliminary work helped select the most appropriate onboard instrumentation for two types of aerial platforms, manned (MAV) and unmanned (UAV). Afterwards, a series of measurement campaigns were performed from 2017 to 2019 in an operational environment over two water distribution networks in France and Portugal. Artificial leaks were introduced and both remote sensing platforms successfully detected them when excluding the unfavorable situations of a recent rain event or high vegetation presence. With the most recent equipment configuration, known and unknown real leaks in the overflown part of a water transportation network in Portugal have been detected. A significant number of false alarms were also observed which were due either to natural water flows (groundwater exfiltration, irrigation runoff and ponds) or to vegetation-cover variability nearby water-distribution nodes. Close interaction with the water utilities, and ancillary information like topographic factors (e.g., slope orientation), are expected to reduce the false alarm rates and improve WADI’s methodology performance.
Highlights
Innovation is key for coping with future water challenges in fields like water management, land use and agriculture since water has become increasingly scarce and less predictable [1]
The optical sensor systems aimed at being used onboard a plane and UAV were designed by first performing a series of airborne measurements involving a thermal infrared camera with microbolometers and two hyperspectral cameras Hyspex (NEO, Oslo, Norway), one in the visible to nearinfrared spectrum (VNIR: 0.4–1 μm), and another one in the shortwave infrared spectrum
The Triangle/Trapezoid Method is a multispectral optical remote sensing method that is well known to be efficient for mapping evapotranspiration and soil moisture at the landscape (>1 km) and field scales (>100 m) from satellite images
Summary
Innovation is key for coping with future water challenges in fields like water management, land use and agriculture since water has become increasingly scarce and less predictable [1]. Improved leak management could boost the network efficiency and optimize water source uses leading to significant environmental benefits. Despite significant improvements over the past 20 years in understanding the economic management of real losses on water distribution systems, little information is available on the actual extent of transmission mains leakage, and how best to quantify and manage it. Detection of water leaks in transmission systems for water supply, irrigation, and hydropower plays a key role in water management efforts to mitigate natural resource depletion, decrease the related energy consumption and help utilities to provide costeffective services. Leaks from seals on transmission mains can go undetected for years causing a significant loss of water. Detection of leakages in large diameter underground mains is a key point but its timely detection faces major challenges
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