| Survey & investigation
completed in the early 1980’s, when an enlarged spillway, now 112m in length, was constructed and 93 post-tensioned anchors were installed in the dam wall to reduce the risk of overturning. “Due to the steep, heavily vegetated terrain in the vicinity of Chichester Dam, deploying traditional survey techniques are difficult, time consuming and costly,” added Turnball. “Traditional surveys are currently undertaken for the site on a two-yearly basis in accordance with regulations.” To enhance public safety and understand Chichester Dam’s behaviour, Rezatec’s Geospatial AI initially interprets three years of historic satellite data to create a retrospective analysis. This first step establishes a baseline trend of what is ‘normal’ and what isn’t. Turnball and the team at Hunter Water then receive monthly updates, using data collected at six-to-twelve- day intervals, to flag and locate any arising issues, down to a few millimetres of displacement. In addition to monitoring precise structural movements, the satellite data analyses vegetation moisture and vigour to pick up indicators of seepage.
Harnessing satellites Another technology that harnesses satellite
technology to remotely monitor water and tailings dams is DAMSAT, available from HR Wallingford. The system’s development was funded by the UK Space Agency, and it uses satellite Earth Observation techniques – including the analysis of spectral responses from satellite images and signals from navigation satellite systems – combined with real-time in-situ monitoring devices. The technology can monitor and predict a host of safety indicators including: dam movement; leakage and pollution; and water level changes. Extensively piloted on over 30 tailings and water dams in Peru, DAMSAT offers a suite of individual modules that can be selected to best suit the particular dam and users’ needs. The system recently won two prizes at the New Civil Engineer’s Techfest Awards: Technology Provider Trailblazer and Technology Leader Trailblazer. Every dam has its own pattern of behaviour, which includes: expanding and contracting; greening and browning; slowly settling; and steady seepage, so DAMSAT warns users about departures from these. It also compares current and past satellite images to detect changes on site, allowing interrogation of historical evidence. Using weather forecasts, DAMSAT also assesses how heavy rainfall will impact the water level in the reservoir, and the subsequent load on the dam and its ancillary structures. The system uses a combination of Interferometric Synthetic Aperture Radar (InSAR) and Global Navigation Satellite System (GNSS), to monitor movement. It also uses several wavelengths of optical satellite data to monitor leakage and pollution indicators, and integrates ten-day advanced satellite weather forecasts from either the National Oceanic and Atmospheric Administration (NOAA) or the European Centre for Medium range Weather Forecasting (ECMWF) twinned with hydrometeorological models to predict water level changes in advance. Usefully, DAMSAT also displays information about the possible impacts downstream if there is a dam breach using cutting-edge numerical models,
EMBREA and the Life Safety Model. EMBREA is a breach model that simulates complex modern dams, and the Life Safety Model helps with the development of emergency plans by assessing the risks to people and evacuation times for various scenarios. In fact, the Life Safety Model represents the behaviour of each individual person, vehicle and building and their interactions with the floodwater and mud. Alongside its EO and modelling components,
DAMSAT is able to add in situ sensors, or complement existing ones, to allow real-time measurement and for independent calibration and validation of measurements from the EO datasets. All this information is then integrated into a cloud- based platform which generates alerts for behavioural changes or unusual weather conditions that could cause infrastructure failure. And DAMSAT is not a one-size-fits all solution, but rather is made up of a number of modules that can be selected to best suit the particular dam and the users’ needs. This may mean incorporation of historical monitoring device data streams, higher or lower resolution data, general surveillance of the dam or more targeted monitoring of an existing area of concern.
Working together A new consortium of Swiss hydropower companies
and science firms are working together to help optimise hydropower production through the use of satellite data. Supported by the Pilot and Demonstration programme of the Swiss Federal Office of Energy (SFOE), climate tech start-up Wegaw and hydrology experts as well as the WSL Institute for f
Below: Hunter Water is working alongside partner Detection Services to expand Rezatec’s Dam Monitoring service across Chichester Dam in New South Wales, Australia
Above: UK utility Bristol Water is to remotely monitor its 15 dams from space using DAMSAT technology, developed by HR Wallingford. View of the Chedder Reservoir, one of the structures to be monitored
www.waterpowermagazine.com | April 2022 | 15
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