On August 15th, volunteer citizen scientists collected water quality data as part of the annual Secchi Day on Beaver Lake event. Beaver Water District (BWD) staff then analyzed the data and produced a report for 2026, which is now available on the District’s website bwdh2o.org.
This year, 37 teams covered 35 sites where they gathered water samples and recorded Secchi depth readings to determine water clarity. Secchi depth is a measure of water transparency that involves lowering a black and white disk into the water and recording the maximum depth at which the black and white pattern can be distinguished from above the water’s surface. Water samples collected at each of the sites were then tested by BWD lab staff for chlorophyll-a, total phosphorus, and total nitrogen to determine algal density and nutrient concentration.
This year’s results were just slightly better than average. Secchi depths were slightly deeper than the 21-year long term average (LTA, see chart below), indicating better water clarity than the LTA. Average whole lake chlorophyll-a, which is a surrogate for algae in the lake, was well below the LTA. This likely points to suspended sediment as the main driver of water clarity on this year’s Secchi Day and not algae.
“Beaver Lake is the source of drinking water for more than 500,000 people in Northwest Arkansas, and Secchi Day gives us a community-powered look at the health of that resource,” said Matthew Rich, Environmental Specialist with BWD. “This year’s results tell an interesting story. Algae levels were well below average, yet clarity did not follow, which likely points to sediment. That’s exactly the kind of insight you get from 21 years of consistent data collection.”
“If you have ever wondered what’s happening in the lake, Secchi Day is the easiest way to be part of the answer. We would love to see new faces on the water next August,” Rich said.
To read the full 2026 Secchi report, visit BWD’s website at bwdh2o.org and go to the Water Data page to find the Secchi Day data report. If you would like more information about volunteer opportunities on the lake, please view our events page on the website or follow Beaver Water District on social media.