Latest Update: Nutrient Pollution in Kentucky’s Waterways

The Division of Water (DOW) just released its 2021 Update to the 2019 Nutrient Loads and Yields in Kentucky Study, which seeks to provide additional insight into nutrient pollution in Kentucky’s waterways. Nutrient pollution is a growing concern in Kentucky. While nutrients naturally exist in waterways, problems can arise when human activity produces too many nutrients, creating more nitrogen and phosphorus in a waterway than the ecosystem can manage.

Nutrient-rich waterways promote algae and plant growth, which often lead to toxic harmful algal blooms (HABs) and insufficient oxygen for fish. This also results in local impacts to tourism and drinking water, along with downstream impacts to fishing livelihoods and tourism in the Gulf of Mexico’s “hypoxic zone.”

The latest update adds two more years of data (2018, 2019) to the prior study, Nutrient Loads and Yields in Kentucky: 2005-2017, while still reviewing long-term statewide changes in nutrient pollution, and areas of greatest nutrient concern.

Data was gathered from an additional five monitoring locations at the mouths of major tributaries to the Ohio River, provided by the Ohio River Valley Water Sanitation Commission (ORSANCO). These additional monitoring stations allow DOW to expand coverage of Kentucky’s drainage area from 76 percent to 82 percent, while identifying out-of-state nutrient contributions. Loads from the remaining 18 percent were estimated by looking at the relationship between the portion of land area used for agriculture, and nitrogen and phosphorus yields. This estimate indicates that approximately  105,000 tons of nitrogen and 12,000 tons of phosphorus leave Kentucky to the Mississippi River Basin annually.

As with the earlier study, the 2021 update found higher nutrient pollution in areas of the state with greater amounts of agriculture activity. However, the additional data also introduced greater variability in loads and yields than the previous study period.

A look at rain patterns across the study period shows that, along with 2011, the two added years of 2018 and 2019 had unusually high precipitation totals. Additional investigation will help determine if changes in rain amounts resulted in greater nutrient runoff than in typical years, and if new climactic trends emerge.

As the DOW continues to look at the issue of nutrients in Kentucky’s waters, it seeks to fill in the nutrient monitoring gaps and more accurately determine the source and amount of nutrient loss. Interested persons can explore this study through the divisions’ interactive Nutrient Reduction in Kentucky story map. The division will continue tracking nutrient pollution to improve the management, protection and restoration of the commonwealth’s water resources.