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A USGS Unmanned Aircraft Systems (UAS) Aquatic Airshow field testing and demonstration event occurred 4/30/2019 - 5/2/2019 on the Saco River near Biddeford, and the Androscoggin River near Lewiston in Maine, USA.

At the airshow, a group of USGS scientists and technicians gathered along with experts from Guideline Geo and Woolpert, to test non-contact sensors for measuring stream discharge using drones, also called unmanned aircraft systems or UAS.  Scientists at the event performed a breakthrough demonstration of river discharge measurement made by drone. River stage, width, bathymetry, and surface velocity were all measured by drone and analysed to produce an accurate river discharge value.

USGS scientists and field personnel traditionally conduct a discharge measurement  either by wading or working from a boat. Due to the potential danger and high risk to personnel safety, hydrologic measurement work is limited during very high flow events, ice break-up, or large floods, when large debris in the current presents hazards. Additionally, conducting measurements in remote areas is also limited by the lack of ability to transport equipment that is needed.

The successful discharge measurement was made possible using several cutting-edge prototype drones. A radar for measuring water speed was integrated on a commercially-available quadcopter drone. In addition, a light-weight, self-contained ground-penetrating radar (GPR) system was mounted on a hexacopter drone.

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Non-contact drone measurements were tested for accuracy by comparing them to ground-truth data collected by a team of USGS hydrologists and hydrologic technicians from the New England and Virginia-West Virginia Water Science Centers using a conventional acoustic doppler current profilers (ADCP), data loggers, and surveying techniques via boat and on foot.

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When fully developed and tested, this new technology will enable a team of two technicians with a drone to make fast, accurate, and safe measurements of rivers even when there are flood conditions, or when rivers contain floating trees, ice, or other dangerous debris. Additionally, this technology will allow for measurements to be conducted in remote areas or hard to access sites of interest. 

Two additional cutting edge prototype drones and methods were tested. A low cost and commercially available drone was used to collect high quality video to determine the speed of the water without touching it with innovative video analyzation techniques. Secondly, a small quadcopter drone mounted with a camera and onboard computer was used to take many photographs along programmed flight paths. The image data was then processed through structure for motion software to create high resolution maps of the sites as well as to generate 3d maps and digital elevation models.

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This event is part of a larger effort of USGS Water Mission Area to develop a next generation water observing system (NGWOS) using cutting edge research and technology. When fully implemented, the USGS Next Generation integrated water observing system will provide quantitative information on streamflow, evapotranspiration, snowpack, soil moisture, a broad suite of water quality constituents, connections between groundwater and surface water, and water use. This information will be directly coupled with the National Water Model and other advanced modeling tools to provide state-of-the-art flood and drought forecasts, drive emergency- and water-management decision support systems, and to address difficult water resource questions.