Seeing Clearly: Measuring Water Quality with Watershed Rangers

Earlier this spring, I had the opportunity to join an after-school field trip to the San Lorenzo River with students from Gault Elementary School. After a few months of assisting the Coastal Watershed Council part-time with communications activities, I really enjoyed the chance to witness some of the organization’s educational programs firsthand. On a breezy, golden afternoon, I watched students measure the water clarity of the San Lorenzo while experiencing a hands-on connection to their local river and the process of doing science at the same time.

Author Erin Loury gets sworn in as an honorary Watershed Ranger

To my surprise, the field trip activities kicked off with Education Coordinator Sam Adelson swearing me in as an honorary Watershed Ranger! Standing before the group, I pledged to care for our community and the river and to keep exploring, helping, and sharing what I know. Sam then presented me with my very own Watershed Ranger badge, explaining to the students that they would soon be receiving badges too when they completed the program at the end of the school year.

We were at the river that day for the students to see whether it offered good habitat for the steelhead trout they had been learning about. Showing photos to the group, Sam reviewed the life cycle of these special fish that are born in freshwater, swim to the ocean to grow, then return to rivers to lay their eggs. The class then made observations about the quality of the habitat on the San Lorenzo. Were there plants along the banks that could keep the river cool with their shade, or provide bugs for fish to eat? Were there rocks of the right size for steelhead to build their nests? (Yes to both).

It all starts with tiny eggs… CWC Education Coordinator Sam Adelson reviews the steelhead life cycle with the class

As a hands-on component of this activity, the students measured the water clarity of the river. Sensitive fish like steelhead need cool, clear, flowing water to thrive. Cloudy or turbid water may sometimes be a sign of excessive algae growth, which can deplete the oxygen available in the water for fish to breathe when these plants die and decompose.

The students measured water clarity using a tall, skinny piece of equipment called a transparency tube, which they filled with river water and lowered in a small black-and-white circle, observing at what point it disappeared from view. That circle is a miniature version of a device called a Secchi disk, which researchers have used to measure the famous clarity of Lake Tahoe for more than 50 years, and which I used myself as a graduate student at nearby Moss Landing Marine Laboratories more than a decade ago, lowering the disk into the ocean to measure water clarity on research trips. It was a treat for me to see the Watershed Rangers using a scaled-down version of this familiar method on the banks of the San Lorenzo.

Watershed Rangers fill transparency tubes with river water to measure how clear it is.

The river water was wonderfully clear that day, with some of the groups able to see the Secchi disk nearly down to the bottom of their 120-cm-long tubes. For the last portion of the field trip, the students were given free time to play and explore along the riverbank. I was heartened to see that, like true scientists, a few wanted to use that time to repeat their water clarity measurements. To add some variety to their observations, Sam stirred a handful of sand into the collected water so the students could compare the experience of measuring cloudy water to their earlier clear samples.

As a wildlife bonus for the afternoon, we spotted several birds at the river and even a little garter snake on the walk from the bus drop-off. I was inspired to see how CWC is helping local students build a connection to the San Lorenzo River environment, while also gaining experience with real scientific methods that provide information needed to care for the river. This work is clearly so important!