T Unlocking the Mokelumne’s secrets
Scientists say new rover is smart, safe and revolutionary
“We’re in a revolution, an exciting one, from analog to analytical and digital. And it comes at an important time. The climate is changing. We need better tools to predict weather patterns and runoff, to keep the river and ecosystem healthy.” JEFF TOONE, EBMUD SUPERVISING HYDROGRAPHER
his week, a very smart little rover has been plying the waters of Lodi Lake and the Mokelumne River. It has three hulls, a GPS system, and innovative sensors allowing it to peer underwater with amazing acuity. While it is a small boat, expectations for it are sizable. In fact, scientists with the East Bay Municipal Utility District believe the trimaran will allow them to see the lake and river as never before. And it may also spare water scientists the sometimes-risky job of plunging into the river, or sometimes dangling over it, manually checking water flows. The bright-orange rover’s powerful acoustic system will allow hydrographers to chart the depths of the lake and river, providing a detailed, 3-D portrait. The sensors are also able to mark the speed and shape of currents through the river and lake. Coupled with a temperature gauge, the craft is expected to provide an unprecedented lode of data. In coming months, in fact, the rover could unlock many of the Mokelumne’s secrets.
‘The fun part of the job’
It’s a sunny morning at the Lodi Lake launching ramp. Red-winged blackbirds dart through the nearby tules and honey bees cruise the blackberries.
The East Bay team is assembled for a shakedown cruise.
“This is the fun part of the job,” said John Urness, an assistant water resources specialist. “Being outside, heading out on the water.”
Urness and Jeff Toone, supervising hydrographer, are co-leaders of the rover program. Together, they carried the trimaran to the grey-green waters of Lodi Lake and prepared for launch.
Along with a GPS system, the boat is fitted with what’s known as an acoustic doppler profiler. It’s the brains and brawn of the operation. Similar to a fish finder on steroids, the instrument shoots out sound waves. It captures their rebounds, or echos, and records them, sort of like a giant robotic ear that can take notes.
Ultimately, notes from the profiler, called a Hydrosurveyor, can be translated into pictures, 3-D images of the lake and river bottoms. (In water circles, the study of river and lake beds is known at bathymetry.)
Previously, much of the river and lake were mapped with an aerial Lidar system. Those data are still useful, but the new rover can gaze more deeply into water, up to 200 feet.
Plus it has an adaptive focus allowing it to see features, both deep and shallow, in greater detail.
The boat is equipped with an electric motor and is entirely capable of being remotely piloted. But these maiden voyages are to check and recheck the craft’s workings and learn their complexities.
So the rover is tethered to a pole jutting from the bow of a 22-foot Jetcraft fishing-type vessel. The Jetcraft pulls the little boat along, making sure it stays precisely on a pre-established grid.
The crew aboard the Jetcraft — seasoned scientists all — share a bubbly sense of excitement.
“This is sort of like exploring,” said Urness “We’ll be seeing new things in new ways.”
Piloting the Jetcraft is Ed Rible, a fisheries and wildlife biologist whose job it is to help manage and nourish the river’s fish population. Through years of research, East Bay biologists have learned how super-sensitive the Mokelumne’s steelhead and Chinook salmon are to the flow, depth and temperature of the water.
“We’re hoping this system can add to our knowledge of the river and our ability to manage the fishery,” he said.
As the rover and its gadgetry become fully operational, they will answer important questions.
Are mud and gunk building up in the lake and river, and if so, where? How deep? How fast?
Is the capacity of Lodi Lake changing?
Are water temperatures rising or dropping in the lake and river? How might that affect the fishery?
Are flows around ag pumps affecting fish?
Moreover, the information will help EBMUD meet legal and environmental requirements, said Toone. The utility operates both the Camanche and Pardee dams upstream from Lodi Lake and sends Mokelumne water to customers in the East Bay area.
For years, Kathy Grant, the City of Lodi’s watershed coordinator, has worked with local students and teachers to measure the clarity and temperature of Lodi Lake.
She’s not directly involved in the East Bay’s explorations, but is keenly interested in the results.
“We see the lake getting more shallow and warmer over time,” she said. “If this program can shed light on that, it would be really useful.”
Making the Mokelumne safer
The system is designed and built in San Diego by SonTek, which sells Hydrosurveyors and related technology all over the globe. Depending on varied options and upgrades, most of the units run around $30,000, said Joel Edelman, senior product and sales specialist for the firm.
By allowing water agencies to view the bottom of a river or stream, scientists have a much better idea of where and how to chart the flow.
“From the surface, a spot may look perfect for measurement. But there could be a boulder disrupting the flow there that can’t be seen from above,” he said.
With advanced equipment, workers don’t have to slog around in the water placing measuring devices.
“There’s a real safety advantage,” Edelman said.
In Australia, SonTek’s gear has been used to probe water at the base of mining pits, allowing workers to stay a safe distance away.
On the Mokelumne, Toone said there are two measuring stations that once required hydrographers to climb aboard small carts and pull themselves out over the water on a cable.
“You could lose a finger if it got caught between the cable and a pulley. If you slipped out in a storm, you could be in real trouble,” Toone said.
The new addition will largely take over those duties.
The trial sessions this week went well, with minor glitches resolved. Initially, the GPS signal between a base station and the rover was weak; adding a taller antenna fixed that.
The rover’s promise, Toone said, could mean a cleaner, safer river. And it reflects an ongoing revolution in environmental monitoring. For instance, years ago weighted ropes and piano wires were the best tools to measure watery depths. No more.
Today, Toone and his East Bay colleagues must blend a passion for the environment and a zeal for technology.
“We’re in a revolution, an exciting one, from analog to analytical and digital,” he said. “And it comes at an important time. The climate is changing. We need better tools to predict weather patterns and runoff, to keep the river and ecosystem healthy.”
Even during this week’s trial runs, the smart little rover has been gleaning information. It will take a few weeks to scour the data and turn it into portraiture.
So while there aren’t any major findings just yet, Toone, a SCUBA diver, is eager to see where the rover will lead.
“There is something exciting about revealing natural surroundings that are so close to us — but usually hidden from view.”