Water Quality Monitoring Technology Protects One Million People

Water Quality Monitoring Helps Protect One Million People

The San Francisco Public Utilities Commission (SFPUC), deployed the latest YSI

and WaterLOG technology to monitor water quality in the Crystal Springs Reservoir.

The reservoir serves as the local water supply for over one million people in San Mateo and San Francisco Counties, as well as a State Fish and Game Refuge for wildlife in the area. Excess water from the SFPUC is stored in the reservoir after being dechloraminated at the Dechloramination Facility and undergoes treatment again as needed for supply to customers.


Crystal Springs Reservoir serves as a local water supply as well as a State Fish and Game Refuge.

The Storm 3 Data Loggers and YSI EXO2 Sondes provide data to help the San Francisco Public Utilities Commission better understand how discharges impact water quality.


SFPUC field service technician heading out onto Crystal Springs Reservoir to deploy the YSI buoys.

Primary Parameter - pH

A key measurement parameter for the San Francisco Public Utilities Commission is pH because pH levels that are either too acidic or too basic can impact aquatic wildlife. The San Francisco Bay Regional Water Board requires that the pH in Crystal Springs Reservoir meet a pH standard of 6.5-8.5. The SFPUC was careful to choose accurate and reliable instruments for monitoring.

“San Francisco Public Utilities needed equipment that would be user friendly, well built, and most of all dependable to keep the water in the Crystal Springs Reservoir pH neutral post-discharge from the Dechloramination Facility. To do this they needed to create an early detection system that would alert the staff when standards were moving out of the pH range,” commented YSI Engineer Sean Harmon. “We chose the combination of the EMM68 Buoy, Storm 3 Data Logger, and EXO2 Water Quality Sonde to accomplish this task."

The Sondes contain a pH sensor, monitoring the water quality every few minutes. The data from the Sonde is collected by the WaterLOG Storm 3 data logger and pushed to the Cloud-hosted Data Collection Platform (DCP) site, where the SFPUC can view the data 24/7 in graphical or tabular form.

By using custom alarm notifications based on the data collected by Storm 3, an early warning is provided to let the SFPUC know when the pH levels rise above or drop below the pH range set forth by regulators of 6.5 to 8.5 in the reservoir.


Storm 3 Data Logger shown inside the Buoy

Instrument Feedback

“With multiple employees using the equipment and viewing the data, they needed something that would be both easy to train employees on, and easy to use,” stated Harmon. “The Bluetooth options of the EXO2 Sonde and the user-friendly web interface of the Storm 3 Data Logger allowed easy maintenance and calibrations during monthly maintenance trips. San Francisco was very pleased with their choice of equipment and the quality of data.”

Ultimately, the water quality data collected with the YSI technology, will assist the SFPUC in complying with prescribed standards and will create a comprehensive analysis of the Crystal Springs Reservoir. By doing so, they will protect fish and the wildlife in the Reservoir.


YSI Buoy comprised of an EXO2 Sonde and Storm 3 Data Logger on Crystal Springs Reservoir.

A special thanks to the San Francisco Public Utilities Commission for the information and pictures included in this blog post. 



Additional Blog Posts of Interest:

Monitoring Wastewater in Hawaii Protects Local Beaches

Monitoring Coral Reefs in the Caribbean: Protecting Our Rainforests of the Ocean 

Water Instrumentation Provides Insight for Ecological Research

10 Tips to Prevent Biofouling on Water Quality Instruments

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