Point of View

Preventing pollution much better than cleaning up Jordan Lake

July 12, 2013 

The N.C. House is poised to vote on a measure that would severely hamper efforts to clean up Jordan Lake for years to come.

Jordan Lake is a major drinking water supply for the Research Triangle area and a heavily used recreational area. Over the years, inputs of nitrogen and phosphorus have led to large algal blooms that impair this waterway, causing the U.S. EPA to require North Carolina to devise a plan (called a TMDL – total maximum daily load) to reduce nutrient inputs. Over several years, a variety of stakeholders worked out a plan involving compromise that was signed by Gov. Bev Perdue.

However, the General Assembly is now considering delaying pollutant controls for three years and suggests that using as-yet unidentified technology within the lake proper can clean it up. The best and cheapest way to improve water quality is to keep the nutrients from entering the lake in the first place.

Jordan Lake receives nutrients from urban areas in stormwater runoff and from agricultural areas and sewage treatment facilities. These nutrients cause algal blooms, the worst type of which is caused by blue-green algae, also called cyanobacteria, which are especially prevalent in summer.

Blue-green algae cause taste and odor problems to drinking water, produce toxins that may kill fish and make people ill, and cause dissolved oxygen to decrease to levels harmful to aquatic life. NCSU researchers have already found measurable amounts of toxins in Jordan Lake and have linked the blue-green blooms to nutrient inputs. Avoiding stricter nutrient controls for three more years will make a bad situation worse – more nutrient loading, more algal blooms and more toxin production.

Many people talk of the need to “clean up” Jordan Lake without any indication of what is meant by “clean up.” Since cleaning up the lake could cost hundreds of millions of dollars, we should be clear about what we mean so that we can assess if money is well-spent and if the goals have been met.

Fortunately, we have a succinct definition for lake cleanup; it is clearly stated in the N.C. water quality standards. Here, the relevant water quality standard stipulates the designated use (for example, recreational fishing or swimming) and the measured water quality criterion is 40 parts per billion of chlorophyll a (which is a measure of algae bloom strength) for Jordan Lake. With that definition, we can evaluate cleanup options based on their effectiveness in meeting the chlorophyll a water quality criterion.

Much has been made of installing numerous aerators in the lake itself as a means of controlling algal blooms and restoring the lake’s water quality. This has been based on the experience of Greenfield Lake in Wilmington, in which aerators were installed in 2005. The aerators have in fact increased dissolved oxygen levels in lake areas near the aerators. However, they have done nothing to reduce nutrient concentrations within the lake, and the number of algal blooms in Greenfield Lake has actually increased since the installation.

Artificial aeration or circulation using “new” technology will not lead to meeting the water quality criterion in Jordan Lake; this conclusion is based on the results of many studies involving in-lake aeration or circulation technology. Despite recent statements coming from NC DENR, the Jordan Rules are based on a plan that will meet the water quality standard, which is required for approval of the cleanup plan by NC DENR and the U.S. EPA.

Technology has a role to play in lake restoration; however, such technologies are best used to control and reduce nitrogen and phosphorus inputs on land before they reach the water. Once in the water, nutrients become extremely expensive to remove and disrupt the lake’s fish and wildlife communities.

Michael A. Mallin, Ph.D., is a research professor at the Center for Marine Sciences at UNC Wilmington. Kenneth H. Reckhow, Ph.D., is a professor emeritus in the Nicholas School of the Environment at Duke University.

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