November 18, 2021 — Beaver Lake Secchi Day Data Released for 16th Year

Beaver Water District’s (BWD) professional laboratory staff have completed the analysis of collected water samples from BWD’s 16th Annual Secchi Day on Beaver Lake. The event was held Aug. 21, 2021, with the help of dedicated volunteers.

“This year, we had 25 sampling teams collecting data and water samples at 31 of our normal 35 sites,” said James McCarty, Manager of Environmental Quality. “Poor weather conditions hampered efforts to collect data in the areas near Indian Creek and Beaver Dam.”

Secchi Day is named for the Secchi Disk, a black and white device lowered into the water to measure transparency. The task of sampling teams is to take Secchi disk readings to determine water transparency. Teams also collect water samples that are then tested by BWD lab staff for chlorophyll-a, total phosphorus, and total nitrogen to determine algal density and nutrient concentration. Secchi depth is a measure of water transparency that involves lowering a black and white disk into the water and recording the maximum depth in which the alternating black and white pattern can be distinguished from above the water’s surface.

Matthew Rich, Environmental Specialist with BWD, spoke about results and data from Secchi Day with the BWD’s Board of Directors at their monthly meeting held on Oct. 21.

“Secchi depth is not only effected by the amount of nutrients and sediment within the lake, but also weather conditions above the surface of the lake,” Rich said. “Windy and rainy conditions will reduce the ability to see the Secchi disk because of wave action generated by rough weather. In addition, clouds that produce the rainstorms will block incoming sunlight, thus further reducing Secchi depths. While we did see some reduction in water transparency as compared to last year’s data, the change was minimal and well within the range that we ordinarily see. This type of result really highlights the importance of understanding year-to-year variability of these water quality parameters.”

After 16 years of data collection, Dr. James McCarty, BWD’s Manager of Environmental Quality, said despite the less than ideal weather for Secchi Day 2021, long-term averages of Secchi Day data indicate that the high level of water quality in Beaver Lake is being maintained.

To read this year’s Secchi Day report, go to the Secchi Day page on the BWD website at and the report will be on the bottom left.

About Beaver Water District

The mission of Beaver Water District (BWD) is to sustainably provide our customers with safe, economical drinking water. BWD provides the clean water, sourced from Beaver Lake, to Fayetteville, Springdale, Rogers, and Bentonville. These cities in Northwest Arkansas then store, distribute and resell the water to their customers. For more information, visit