The 'classic' systems of leak detection The water meter networks used so far, such as ultrasound or time lag evaluation systems, implemented in the volumetric and pressure meter network are proving to be ineffective, either for early detection or for precise localisation. With the added drawback that they require a large amount of associated dedicated resources, both human and energy dependent, to power sensors.
An efficient way to detect water leaks in distribution networks is to use images taken from flying platforms such as satellites or drones. These snapshots can provide a detailed, large-scale view of the distribution network, allowing the detection of areas of anomalies that may indicate the presence of a leak. This technique enables cost-effective analysis and its regular use facilitates the rapid location and repair of leaks, helping to ensure the efficiency and sustainability of the water supply.
There are different flight platforms operating at different altitudes or orbits that can carry valid instruments to provide the kind of photographs needed for water leak detection:
- Satellites (large, medium and small), typically operating in medium and distant orbits.
- Microsatellites and CubeSats, which usually operate in low Earth orbits (LEO).
- Atmospheric fixed-wing, rotary-wing, multicopter and metrology airships.
High-quality, high-resolution images are essential to detect leaks.
Satellite imagery tends to have a higher resolution than drone imagery, but drones can provide more focused and detailed snapshots of specific areas due to their ability to fly at low altitude. Satellite imagery is often provided by space agencies:
European Space Agency is a space agency that offers synthetic aperture radar images through its Sentinel programme. They are available for free download via the Sentinel data portal. ESA.
The Japan Aerospace Exploration Agency (JAXA) offers synthetic aperture radar images via its website in the 'research data and products' section, available for download.
The main instruments on board the aircraft that allow the acquisition of quality images valid for leak detection are mainly of two types:
NIR (Near Infrared) cameras are capable of detecting changes in surface temperature and use near-infrared radiation, invisible to the human eye, to obtain images. These cameras can be lightweight and small in size, making them ideal for onboard microsatellites, CubeSats and drones.
Synthetic Aperture Radar (SAR) is a radar technique that can also be used to detect water leaks in distribution networks. It has an antenna that transmits high-frequency radar signals and then receives the reflected signals from objects in the scanning area. The SAR is capable of providing high resolution images and has the advantage of being able to operate independently of ambient light, which is very useful for leak detection in dark or covered areas. It is commonly used in buried pipe detection applications as it can detect changes in the electrical resistance of the soil due to the presence of water.
Water is a conductor of electricity and therefore affects the electrical resistance of the ground where it is located. By detecting these changes in electrical resistance, SAR can provide accurate images and thus determine the location and size of the leak.
In addition, it can also detect changes in water content in the soil, which can be useful for monitoring surface water distribution networks. To detect changes in the electrical resistance of the ground, SAR uses a technique called Ground Penetrating Radar with Polarization (GPR-P). GPR-P operates over a wide range of frequencies, typically between 100 MHz and 3 GHz. The selection of the appropriate frequency depends on the purpose of the measurement and the type of soil. For example, low frequencies are used to detect objects and anomalies deep in the ground and higher frequencies are used to detect anomalies close to the surface.
Crop moisture by remote sensing
The Normalized Difference Moisture Index (NDMI) is a good example of how these instruments work to provide a measure of the amount of water present in vegetation. It is calculated using satellite images that measure the reflectivity of the earth at different wavelengths. It is based on the idea that dry vegetation reflects more light in the near-infrared wavelengths and less light in the visible wavelength. Therefore, when vegetation is drier, the NDMI increases.
NDMI is used to monitor drought and assess the state of vegetation in different regions.
It is important to note that near infrared spectroscopy (NIR) and synthetic aperture radar (SAR) are tools and should be used in conjunction with other techniques and methods to confirm the presence of a leak and determine the best way to repair it. Therefore, once the images are obtained, they must be processed and analysed to detect possible anomalies.
Signs that may indicate the presence of a leak include increased soil moisture or excessive vegetation growth in areas where it would not be expected. Changes in surface colour or temperature are also often detected and may be indicative of a leak.
Upon detection of a potential leak, it is always necessary to send an investigation team to the site to verify the leak and determine the cause. This may include checking the distribution network infrastructure using flow detection equipment that can measure the velocity and direction of water flow in a pipe and pressure testing of the network is also prescriptive.
Some of the leak detection equipment involves the use of gas (helium) using a technique known as 'helium pressurisation test'.
In this method, the gas is injected into the pipeline or water distribution system and then a detector is used to discover the presence of helium in the area where a leak is suspected.
Elliot Early Water Leaks Detection System EEWLDS
Elliot Cloud develops a frontier technology process based on multispectral imaging and proprietary treatment and purification algorithms to offer its customers a monitoring, discovery and early warning system that allows maximum reactivity to a water leakage event in their distribution networks.
- Obtaining satellite images of the geographical area involved in GIS.
- Processing of satellite images and discovery of irrigated areas.
- Obtaining DRON images of the irrigation areas detected.