LOWELL, AR — For the past 10 years, more than 100 citizen scientists and others have collected water quality data on Beaver Lake near Rogers in Northwest Arkansas during the annual Secchi Day event, typically held on the third Saturday each August. The big question on everyone’s minds is whether there are any trends that can be identified, now that there’s a decade of data to consider. To put it simply, how is the water quality in Beaver Lake doing?
Dr. Bob Morgan, Manager of Environmental Quality for Beaver Water District (BWD), and Sabrina Bowman, Environmental Specialist, shared data and comments about Secchi Day with BWD Board members during their regularly scheduled meeting held at noon today.
Bowman reported that eight new volunteer sampling teams participated this year and a total of 30 teams covered 35 sample sites throughout Beaver Lake. Many of the veteran teams have been participants every year since the event began in 2006. Sampling teams take Secchi disk readings to determine water clarity, and collect water samples which are tested for chlorophyll a, total phosphorus, and nitrate, 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.
Morgan said, “Overall, everything was slightly better this year than the average of the data over the past 10 years. However, the data tell us that the water quality is not rapidly changing one way or the other, at least in late summer. In other words, the lake water quality is maintaining, and that’s what we want to see.”
He added that one of the longtime volunteers said he helps collect data so that someday far into the future, maybe 50 years from now, people will have records of how clear and clean water in the lake used to be. That observation was very astute as our memories of what used to be tend to degrade over time. It maintains a record of what can be.
This year, the greatest Secchi depth was 5 meters, or approximately 16 feet. This occurred at site 29 near Beaver Dam. The lowest depth of 1.05 meters, a bit more than 3 feet, was measured at Site 1 at Hwy. 412 Bridge. The average Secchi depth for 2015 was slightly greater than the 10-year long term average of 2.7 meters. Near surface mean concentrations for both chlorophyll a and nitrate were lower in 2015 than in the last nine years. Secchi depth in late August is inversely related to the concentration of chlorophyll a. Therefore, as chlorophyll a decreases, Secchi depth increases.
To read this year’s detailed Secchi report, link to the District’s website at bwdh2o.org. Next year’s event will be held on Aug. 20, 2016. Secchi Day on Beaver Lake is made possible by 11 partners including BWD, the U.S. Army Corps of Engineers-Beaver Lake, the U.S. Geological Survey, the University of Arkansas Cooperative Extension Service, Hobbs State Park, Northwest Arkansas Master Naturalists, the Association for Beaver Lake Environment, Beaver Watershed Alliance, Arkansas Game & Fish Commission, Ozarks Water Watch, and One Community. Secchi Day is one of the premiere water public awareness and education events in Arkansas.
BWD’s board 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 and 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 $1.29 per 1000 gallons to Fayetteville, Springdale, Rogers and Bentonville. The raw water is sourced from Beaver Lake, which one in seven Arkansans relies on lake for safe, clean drinking water.