November 14, 2018 – Beaver Lake “Secchi Day” Data Released for 13th Year

On Aug. 18 for the 13th year in a row, volunteer citizen scientists collected water quality data on Beaver Lake in Northwest Arkansas during the annual Secchi Day on Beaver Lake event. Beaver Water District (BWD) staff then analyze data and produce a report that helps answer this question: How is the water quality in Beaver Lake?

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. 18.

This year, 36 teams covered 35 sample sites throughout the lake. Sampling teams take Secchi disk readings to determine water clarity. They 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 black and white pattern can be distinguished from above the water’s surface.

“Secchi depth is inversely related to the concentration of chlorophyll-a. Therefore, as chlorophyll-a decreases, Secchi depth increases.” Rich said.

“When it comes to producing drinking water, greater Secchi depths and lesser chlorophyll-a concentrations are best,” he added. “With each year that passes, we get a better picture of the variability in water quality at the different sites that are sampled.”

This year’s data shows that most water quality parameters were fairly close to the previous 12-year average.  The average lake Secchi depth this year was around 9.6 feet, which is a slight improvement over the long-term average of 8.9 feet.  The average lake chlorophyll-a this year was 9.42 parts per billion (ppb) which was slightly greater than the long-term average of 7.32 ppb.  The higher average chlorophyll-a concentration this year was driven in part by some unusually high values observed in the headwaters of the lake.  However, both Secchi depth and chlorophyll-a averages were well within the normal variations for the 12-year dataset.

“Year after year, Secchi Day continues to provide BWD with excellent data concerning the water quality in Beaver Lake.  There has been quite a bit of variability in the last twelve years, but the silver lining is that at this point, we do not have any indication that water quality is degrading,” Rich said.

James McCarty, BWD’s Manager of Environmental Quality, added that “Secchi Day is only one example of the work we do. There isn’t a week throughout the year that either BWD or one of our partners like the United States Geological Survey or Arkansas Water Resources Center is not either on the lake or in the watershed collecting data.  This data helps us to keep watch on key indicators of water quality problems and helps to assess our restoration and protection efforts within the watershed.”

To read this year’s Secchi report, link to BWD’s website at then go to the Secchi Day page here ( and the report will be on the bottom left. Mark your calendar now. The 14th Annual Secchi Day & Science Festival on Beaver Lake will be held Aug. 17, 2019. The event includes many partners such as the U.S. Army Corps of Engineers-Beaver Lake, the U.S. Geological Survey, the University of Arkansas Cooperative Extension Service, Northwest Arkansas Stormwater, Hobbs State Park, Northwest Arkansas Master Naturalists, Beaver Watershed Alliance, Beaver Lake Fire Department, Ozarks Water Watch, One Community, The Ozark Society, and Girl Scouts Diamonds of Arkansas, Oklahoma and Texas. Secchi Day is one of the premiere water public awareness and education events in Arkansas.

About Beaver Water District

BWD’s Board of Directors meets monthly with the exception of December. The board consists of three members from Washington County and three from Benton County. They are elected to six-year terms. Every two years, a position comes open in each county. The board oversees BWD, which cleans and purifies drinking water sold at the wholesale price of $1.36 per 1000 gallons to Fayetteville, Springdale, Rogers and Bentonville. The raw water is sourced from Beaver Lake, which one in seven Arkansans relies upon as a source for water. BWD’s mission is to serve its customers’ needs by providing high quality drinking water that meets or exceeds all regulatory requirements and is economically priced consistent with our quality standards. For more information, visit