25-Year Jordan Water Quality Trends

A US Geological Survey Report released late in 2018 provides a needed review of water quality trends for select NC rivers and streams over the last 25-years (1989-2013). Importantly, the report focuses on the quality of water flowing to drinking water reservoirs in North Carolina.  Here, I’ll briefly cover the results affecting Jordan Lake where data both in streams and the Lake were analyzed to gauge what’s happening and what’s needed to protect our drinking waters.

What’s happening? 

Over the 25-year study period, population in counties surrounding the Lake grew by 85%. Not surprisingly, during that period developed land use nearly doubled in watersheds draining to Jordan Lake, typically coming from less polluting forested land use.  Also, during that time, improvements have been made to waste water treatment plants that have reduced the discharge of pollutants even though the plants were serving more users.  Overall, there are a mixture of factors that have influenced water quality flowing to Jordan Lake.

What are the trends?

In a word, mixed.  Generally, monitoring of nutrients in streams near Jordan Lake showed improvement TP concentrations more than TN (See Figure 1). Conditions in Jordan Lake, however, were less promising with stations showing increased concentrations for both TN and TP.  Much like our estuaries, organic nitrogen was the primary form of N that increased during the period of study.

Conclusions

Increases in triangle-area population continue to put a strain on Jordan Lake both for adequate quantity and quality for its users.  Even though management efforts over the study period resulted in some in-stream water quality improvement, conditions continue to be poor at the lake demonstrating the continued need for policies protective of the Lake.

Figure 1. Trends in water quality of selected streams and reservoirs used for water supply in the Triangle area of North Carolina, 1989–2013: U.S. Geological Survey Scientific Investigations Report 2018–5077, 67 p., https://doi.org/10.3133/sir20185077. USGS 2018.
Monitoring Stations near and in Jordan Lake used in the 25-year study. Source: USGS 2018.

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