SOUTH LAKE TAHOE, Calif. — One of the longest-running watershed monitoring events on the West Coast returns Saturday.

The 19th annual Snapshot Day runs from 9 a.m. to noon May 18.

A collaborative effort between the League to Save Lake Tahoe, the Nevada Division of Environmental Protection, the Tahoe Water Suppliers Association and the Truckee River Watershed Council, the event aims to collect data — a snapshot — about the health of streams and lakes in the Tahoe-Truckee watershed.

Data collected in 2018, according to the League, painted a healthy picture with a few notable exceptions.

Only 22% of the sites monitored in 2018 showed elevated levels of turbidity, which was down from 30% of the sites in 2017. Turbidity is a measure of the water’s cloudiness and an indicator of the presence of fine sediment pollution, the leading cause of clarity loss in Lake Tahoe, per the League.

“This is a positive trend and one we hope continues in 2019. But it needs to be tempered by the fact that prior to this, we had four years of drought followed by a big winter in 2017 and significant spring runoff,” Emily Frey, natural resources associate for the League, said in a news announcement. “Measuring consistently year after year is critical for getting an accurate read on this and other water quality trends.”

No experience is necessary to participate in Snapshot Day, although the League does as for participants to RSVP online at http://ow.ly/Il1t30nlhmh.

Volunteers should meet at Lake Tahoe Community College at 1 College Drive in South Lake Tahoe — enter the main building on campus and follow the signs. Refreshments will be provided.

The League advises wearing layers and bringing sunglasses, a sun hat, sunscreen and a reusable water bottle. Volunteers also should be prepared to possibly wade in the water.

For questions, visit keeptahoeblue.org or email protect@keeptahoeblue.org.