Overview
An innovative California water resources firm found the winning combination for expanding measurements at Northern California stream gauging sites, by integrating the In-Situ Aqua TROLL multiparameter sonde with the Ott radar level sensor and SatLink logging transmitter.
Challenge
Across California, roughly 1,000 stream gauges track the flows of the state's waterways. The data shapes decisions on everything from flood response and drought planning to the management of ecosystems and the water supply. With California experiencing more frequent shifts between climate extremes, the state is now making a generational investment in a major upgrade and expansion of its stream gauge network through the California Department of Water Resources’ Stream Gage Improvement Program (CalSIP).
At some stations, the CalSIP upgrade includes adding something new: water quality monitoring. When climate changes, water quality is likely also changing. Dissolved oxygen, salinity and water temperature are all affected by climate shifts. Tracking them can reveal a lot about a stream's health. These parameters are especially critical for highly sensitive fish species like salmon and steelhead.
Davids Engineering, Inc. is working as a subcontractor with INTERA on the CalSIP upgrades at several stations. The work includes initiating water quality monitoring in three gauging stations nestled in the Cascade Mountain watersheds of Northern California. The stations are now poised to tell an even fuller story about the health of these waters.
Solution
The Davids Engineering team has been doing stream flow gauging for over 20 years, mostly in an agricultural context to provide data about surface water distributions to farmers and agricultural communities. The work at the Cascade sites was a different context in more natural watersheds.
“CalSIP has been a great opportunity for us to stretch out into that natural context,” said Dr. Jeff Davids, Chief Technology Officer and Vice President at Davids Engineering.
That stretch involved finding new technologies, including setting up telemetry for the data transmission, and identifying a radar level sensor for the level and flow measurements and a multiparameter sonde for the water quality measurements. Chris Sortor, an engineer on the project at Davids Engineering, set out to find the solutions.
Davids Engineering hadn’t done satellite telemetry before, so they asked California’s Department of Water Resources for advice. “They were the ones who turned us onto the [Ott] SUTRON SatLink 3,” explained Sortor. The SatLink 3 is a logging transmitter that can monitor and transmit up to 32 independent measurements from analog, digital and smart sensors. In this case, the SatLink 3 has built-in support for the GOES geostationary satellite. Sortor used Ott’s LinkComm software to do the setup.
For the water quality measurements, Davids Engineering did have some previous experience with measuring dissolved oxygen at various sites in California. However, they were having trouble with the reliability of the sensor they were using at those sites. Davids Engineering chose the Aqua TROLL 500 multiparameter sonde with a central wiper and sensors for dissolved oxygen, conductivity and temperature.
One feature of the Aqua TROLL important to Davids Engineering was the ability to interchange sensors. They were thinking ahead to the bigger picture beyond the three sites in the Cascades. The sensor flexibility meant that Davids Engineering would be able to meet the requirements of different sites in the larger network of 29 CalSIP sites that the team is installing or upgrading. At the three sites in the Cascades, the parameters of interest are dissolved oxygen, salinity and temperature. But at other sites, clients were interested in different parameters. “Overall, everyone wanted water level and flow. But the additional water quality parameters were different depending on the site,” said Sortor.
Rounding out the installation in the Cascades, the Ott Radar Level Sensor 500 provides the level data that is input to calculations of flow for two of the three sites. An acoustic device from another manufacturer was already in use at the third site.
The combination of Ott’s SUTRON SatLink 3 and RLS 500 with the In-Situ Aqua TROLL 500 is a good example of the strengths of the In-Situ lineup and the Ott lineup coming together, a joining of teams and products that took place in a broader sense when the companies merged in early 2026. These Davids Engineering efforts have been a good test case coming at a key time for Ott / In-Situ. “It’s been neat integrating both of those together,” said Sortor.
Results
The CalSIP contracts for the three Cascade sites were finalized in early 2025, and the work on designing the installations, procuring the monitoring equipment, and negotiating with landowners began in earnest. The team did water quality spot checking with a “traveling” Aqua TROLL 500 while the permanent installations were being built out, to start to get a handle on what to expect at the sites. Data started flowing from the permanent install at one of the three sites by midsummer 2026, with the last of the three sites operational by late September.
As the permanent sites have come online, the team continued the spot check with the traveling Aqua TROLL, which Sortor refers to as their “gold standard” that they calibrate and maintain frequently in the office. “We’re taking it out to the field and making sure that the ones that are permanently installed out there are comparing well to it. And so far, they’ve all matched up really well.”
Using the VuSitu phone app has helped everything go smoothly, he reports: “Honestly, it’s one of the best ways to interact and configure an instrument that I’ve come across so far.”
The big test of integrating the In-Situ and Ott equipment came when it was time to set up the Aqua TROLL 500 for SDI-12 communication with the SUTRON SatLink 3. Each sensor of the Aqua TROLL has its own address and parameter ID on the SatLink and is wired in its specific SDI-12 port on the SatLink to provide its measurement. Similarly, the Ott RLS 500 radar level sensor has its designated addresses on the SatLink. Being able to use VuSitu to set the order of the Aqua TROLL’s parameters and change the units if needed “was really smooth and easy to use,” Sortor said. “This is where the integration between the two sensors [RLS 500 and Aqua TROLL 500] comes together."
All the stream gauges in the California system report their data to the California Data Exchange Center, which maintains a website where the data can be accessed by anyone. “As we’ve been getting these sites online…there’s been a lot of good reports back and people are finding the data very neat to see,” Sortor notes. The data from the sites in the Cascades will provide information that directly supports fisheries health, a goal that resonates strongly with anglers, recreationalists, visitors, and the general public.
The work at the CalSIP stream gauging sites fits in well with the mission of Davids Engineering, explains Jeff Davids. “How do we navigate that hotter and drier future, one that is likely filled with more extreme events? We’re really passionate about developing a quantitative understanding of what that actually looks like. How do our stream flows change? How do our demands for irrigation water change? How do our aquifers respond to those different stressors?”
With their work to integrate water quality and stream gauging measurements at CalSIP sites well underway, Davids Engineering and partner INTERA are perfectly positioned to help the State of California understand and cope with its water future.
Since 1993, Davids Engineering, Inc. has provided professional engineering and scientific services to public agencies, private entities and individual landowners responsible for managing water resources in the western United States and beyond. Sustainable agricultural water management and environmental stewardship are core to their vision and the services they offer.
INTERA helps California navigate a changing water future by advancing innovative groundwater, recharge, and water resource management solutions. Our team supports sustainable water supplies, regulatory compliance, and informed decision-making that strengthens communities and the environment.
“We’ve been very happy with every piece of equipment we have purchased and haven’t had a ton of problems with it. And even when we do [have a problem], we’ve been able to get ahold of tech support and they’ve been super helpful. We’ve had a really good experience overall.” Chris Sortor, Engineer at Davids Engineering