By Kenneth H. Reckhow and Michael D. Aitken
Even at the planning stages for the two large Corps of Engineers reservoirs (Jordan Lake and Falls Lake) in the Triangle area, water scientists in North Carolina understood that they would have great difficulty complying with water quality standards.
This has proven to be true, as both reservoirs are in violation of the North Carolina water quality standard for chlorophyll and are now subject to substantial reductions in nutrient (phosphorus and nitrogen) loading. Achieving compliance with this water quality standard is estimated to cost hundreds of millions of dollars, so it is understandable that questions are being raised about the wisdom and effectiveness of costly nutrient control measures.
All states are mandated by the federal government to set water quality standards for their surface water bodies, which North Carolina has done, and they conduct water quality monitoring programs to assess compliance with standards. If a water body is found to be out of compliance, which is the case for both Jordan and Falls Lakes, then the state must develop a plan (often in the form of a Total Maximum Daily Load, or TMDL) that describes what management actions will be implemented to achieve compliance.
These TMDL plans have been developed for Jordan and Falls Lakes and are in the early stages of implementation by the watershed jurisdictions. It has recently been suggested that the nutrient management actions implemented in the Jordan Lake watershed are having no discernible impact on Jordan Lake. In the minds of some individuals, this conclusion leads to the recommendation to abandon the Jordan Lake Rules (the agreed-upon plan to implement nutrient control measures in the watershed) and instead implement in-lake technologies to improve water quality in Jordan Lake. There are at least two fundamental errors in these perspectives.
First, even if all required nutrient management actions were implemented on the day that the Jordan Rules were approved, it would take years for a large water body like Jordan Lake to respond to reductions in pollutant inputs. The actual implementation of pollutant controls, which includes time to put management actions in place, requires additional time for the impact of these actions to be observable in the lake. One of us (Reckhow) recently chaired the National Academy of Sciences review of the Chesapeake Bay water quality program. A point emphasized in this review was that the public needs to be patient concerning the time required for improvements in water quality in the Bay. For example, people should not expect that implementation of stormwater detention basins in their neighborhoods would quickly result in observable water quality improvements in the Bay. We cautioned that several years, even a decade, might be necessary to see the improvements. However, we also recognized that if the jurisdictions in the Chesapeake watershed maintained their nutrient management implementation schedule, ultimately they would see the improvements that they expected.
Second, there are no technologies, new or old, that can provide any meaningful level of cleanup of algae in a lake the size of Jordan. In-lake techniques to improve water quality, such as harvesting, aeration, and algaecides, can be effective in ponds (or, at best, in small lakes), but they are not intended for large waterbodies. Further, there is no evidence that these techniques will result in compliance with the chlorophyll a criterion in Jordan Lake.
We are both engineers with great faith that many of today’s problems can be solved through technology. But we do not subscribe to blind faith in technology to correct preventable problems. A first principle of responsible stewardship for any public water supply is to protect the watershed. There are viable, proven means of reducing inputs of nutrients and other pollutants to reservoirs that are embodied in the Jordan and Falls Lake Rules. These inputs will only increase as the affected communities and municipalities grow if appropriate watershed management plans are not in place. And, standard engineering practice before implementing any proposed new technology is to evaluate it thoroughly, in context and at a relevant scale, especially when the consequences of failure have implications for public health.
The nutrient management plans for Falls and Jordan Lakes have been based on sound scientific analysis and active stakeholder involvement. For Falls Lake, to further ensure that a deliberative process continues, a careful re-examination and refinement of the modeling and assessment that resulted in the Falls Lake Rules is in progress. In our view, this adaptive management approach is a far more prudent strategy for effective management of lakes than is the hasty and ill-conceived abandonment of the Jordan Lake Rules that is currently under consideration by the General Assembly.
Kenneth H. Reckhow is professor emeritus, Nicholas School of the Environment, Duke University. Michael D. Aitken is professor and chair, Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, University of North Carolina at Chapel Hill.