October 15, 2020 – Beaver Lake Secchi Day Data Released for 15th Year

Despite the COVID pandemic, Beaver Water District’s Secchi Day on Beaver Lake sampling activities — with many, longtime and dedicated volunteers — continued this year on Aug. 15, 2020, with all the necessary precautions to ensure everyone was safe. Secchi Day is named for the Secchi Disk, a black and white device lowered into the water to measure transparency.

While most years there are nearly 40 sampling teams collecting data and water samples from 35 duplicated sites, due to the pandemic, 21 teams participated, with 20 percent duplication of the 35 sites.

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 today, on Oct. 15.

“Secchi depth is inversely related to both the concentration of chlorophyll-a, (a bioindicator of algae) as well as other suspended sediments in the water,” Rich said. “As chlorophyll-a and suspended sediments decrease, Secchi transparency increases. This exact trend also occurs naturally as you move from the headwaters of the lake toward Beaver Dam. When it comes to producing drinking water, greater Secchi transparency, and lesser chlorophyll-a and nutrient concentrations, are best. At all 35 sites in 2020, chlorophyll-a concentrations were lesser than, while Secchi depths were greater than, their long-term averages for each site. These results are positive because the leap from excess nutrients to water quality degradation can be short.”

After 15 years of data collection, Dr. James McCarty, BWD’s Manager of Environmental Quality, said we are maintaining the water quality in Beaver Lake.

To read this year’s Secchi Day report, go to the Secchi Day page on the BWD website at https://www.bwdh2o.org/education-outreach/secchi-day/ 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 pump, store, distribute and resell the water to their customers. For more information, visit www.bwdh2o.org.