Andrew Tinka tosses a floating robot into the Sacramento River. Photo: Jerome Thai
A fleet of 100 floating robots took a trip down the Sacramento River on Wednesday,
May 9, 2012, in a field test organized by engineers at the University of California,
smartphone-equipped floating robots demonstrated the next generation of water
monitoring technology, promising to transform the way government agencies
monitor one of the state’s most precious resources.
The Floating Sensor Network project, led by associate professor Alexandre
Bayen, a researcher at the Center for Information Technology Research in the
Interest of Society (CITRIS), offers a network of mobile sensors that can be
deployed rapidly to provide real-time, high-resolution data in hard-to-map
waterways. One area that stands to benefit from this technology is the
Sacramento-San Joaquin River Delta, with its complex network of channels that
direct drinking water to two-thirds of California’s
population and irrigation water for 3 million acres of agriculture.
Having a high volume of sensors moving through the water can shed light on
processes that are influenced by how water moves, such as the spread of
pollutants, the migration of salmon, or how salt and fresh water mix in the
Delta’s ecosystem, the researchers said. The field test gave researchers a
picture of how water moves through a junction in the river with a resolution
never before achieved.
“We are putting water online,” said Bayen, who holds joint appointments in
UC Berkeley’s Departments of Electrical Engineering and Computer Sciences and
of Civil and Environmental Engineering. “Monitoring the state’s water supply is
critical for the general public, water researchers and government agencies,
which now rely upon costly fixed water sensor stations that don’t always
generate sufficient data for modeling and prediction. The mobile probes we are
using could potentially expand coverage in the Delta—on demand—to hundreds of
miles of natural and manmade channels that are currently under-monitored, and
help agencies responsible for managing the state’s limited water supply.”
Such a flexible system could be critical in the event of an emergency,
including a levee breach or oil spill, the researchers noted. The sensors could
be thrown into action from a dock, shore, boats, or even helicopters.
“If something spills in the water, if there’s a contaminant, you need to
know where it is now, you need to know where it’s going, you need to know where
it will be later on,” said Andrew Tinka, a PhD candidate in electrical
engineering and computer sciences and the lead graduate student on the project. “The Floating Sensor Network project can help by tracking water flow at a level
of detail not currently possible.”
The May 9 launch in Walnut Grove,
Calif., marked a milestone in the
project, which is supported by CITRIS and the Lawrence Berkeley National
Laboratory (Berkeley Lab). It was the first time researchers deployed their
full arsenal of floats, each equipped with GPS-enabled mobile phones encased in
12-in-long watertight capsules marked with fluorescent tape. The researchers
wrote specific programs to run on the open source platforms used in the robots
and on the smartphones.
The project is an evolution of earlier research led by Bayen called Mobile
Century and Mobile Millennium, which uses GPS-enabled smartphones to monitor
traffic flow. Instead of a map of traffic, the Floating Century mobile probes
created a map of water flow.
Every few seconds, the phones in the floats transmitted location data back
to servers at Berkeley Lab’s National Energy Research Scientific Computing
Center (NERSC), where the data was assimilated using a computer model called
REALM (River, Estuary and Land Model). Information was processed to create a
map that allowed researchers to track the devices on their computer monitors.
“Not only is this project interesting from a data collection perspective,
but it also presents a new challenge for us on the data processing side,” said
Shane Canon, head of the Technology Integration Group at NERSC. “While the
total amount of data is not unusual, the streaming rate is higher than we
usually see, and the researchers are looking to access the data in near real time.”
The REALM model was developed by researchers at the Berkeley Lab and the
California Department of Water Resources. It was later expanded to integrate
data from mobile robots by Qingfang Wu, a UC Berkeley graduate student in civil
and environmental engineering.
“Part of the novelty of this project is the use of the NERSC computer
cluster to run large-scale data assimilation problems,” said Wu. “The floating
sensor project demands the ability to process hundreds of parallel versions of
REALM and integrate the results into an estimate of the hydrodynamics of the
Although the sensors in the test were set up to monitor the speed of water
currents, the researchers said the floats could be equipped with sensors for a
variety of measurements, including temperature, salinity, or a contaminant of
Of the 100 floats in the fleet, 40 were autonomous devices fitted with
propellers to help them move around obstacles or targeted areas.
“The major constraint on floating sensors in inland environments is their
tendency to get stuck on the shores,” said Tinka. “Currently, using floating
sensors requires close human supervision. We are developing autonomous,
actuated sensors that can use propulsion to avoid obstacles.”
The Floating Sensor Network’s fleet of robots includes prototypes with
advanced capabilities, including models that can dive below the surface of the
water, versions equipped with salinity sensors to measure the water quality in
rivers, and versions with depth sensors that can map out the shape of the
channels in which they float.
“Our development efforts show the versatility of this technology and how it
can adapt to the challenges faced in different applications,” said Bayen. “For
example, the capability to measure depth is particularly important in
situations where it is impractical or dangerous to send personnel to do the
job, such as in military operations in combat zones. Floating sensor fleets
also provide capabilities which can be used to improve our understanding of the
shape of domestic rivers and deltas.”
The floating sensor network has been tested in collaboration with the U.S.
Department of Homeland Security and the U.S. Army Corps of Engineers to assess
water discharge downstream from broken levees. The researchers are also
planning a deployment to monitor the ecosystem of Lake
Tahoe in the coming months.
Floats are retrieved at the end of experiments, but the researchers
acknowledged the possibility that devices can get lost. The researchers said
they expect the expense of individual sensors to go down with continuing
advances in mobile communications so that the system can better tolerate a
certain level of device dropout.
“In the future, cost and size will go down, while performance and autonomy
will go up, enabling monitoring at unprecedented scales,” said Bayen. “We
expect this to become an invaluable tool for the future management of a
critical resource in this state and around the world.”