Old Hickory Lake is generally clean enough for swimming, boating, and fishing. As of 2025, the Tennessee Department of Environment and Conservation (TDEC) does not list Old Hickory Reservoir under any active bacteriological or fish tissue advisories, which means it meets the state’s standards for recreational contact and fish consumption. That said, the lake does face ongoing water quality pressures worth understanding if you spend time on or in the water.
No Active Advisories as of 2025
TDEC publishes an annual list of Tennessee streams, rivers, and reservoirs that carry warnings due to bacteria levels or contaminated fish tissue. Old Hickory Lake does not appear on the 2025 version of that list. For comparison, some nearby stretches of the Cumberland River system do carry advisories, so Old Hickory’s absence is a meaningful signal that routine monitoring hasn’t flagged persistent contamination problems.
This doesn’t mean the water is pristine at every point on every day. Bacteria levels in any lake fluctuate with rainfall, temperature, and seasonal runoff. A heavy storm can temporarily spike bacteria counts near shorelines, creek inflows, and areas close to stormwater drains. If the water looks murky or you notice runoff flowing in after a downpour, it’s worth waiting a day or two before swimming.
Where the Pollution Comes From
The biggest water quality challenge for Old Hickory Lake is nutrient loading, particularly phosphorus. EPA monitoring has found that roughly 97.6% of the phosphorus entering the reservoir comes from nonpoint sources, meaning it washes in from across the landscape rather than flowing out of a single pipe. The surrounding geology plays a large role here. The Cumberland River basin sits on phosphate-rich limestone, and as rainwater moves across and through that rock, it carries dissolved phosphorus into tributaries and eventually into the lake.
Agricultural runoff, lawn fertilizers, and urban stormwater all add to that natural baseline. On the point-source side, several municipal wastewater treatment plants discharge into the watershed, including facilities serving Hendersonville, Gallatin, Lebanon, Mt. Juliet, and other growing communities around the lake. Industrial operations have historically contributed nitrogen-rich effluent as well. Still, point sources account for only about 2.4% of the lake’s total phosphorus load, making diffuse runoff the far bigger factor.
Why Phosphorus Matters for Lake Quality
Excess phosphorus feeds algae growth. When algae blooms die off, the decomposition process consumes dissolved oxygen in the water, which can stress fish populations and degrade water clarity. In warm summer months, this cycle is more pronounced, particularly in shallow coves and near tributary inflows where nutrients concentrate. You may notice greenish water or surface scum in these areas during hot, calm stretches of weather. Blue-green algae (cyanobacteria) blooms can occasionally produce toxins that irritate skin and are harmful if swallowed, so it’s smart to avoid swimming in water that looks like spilled paint or has a thick green film.
The lake’s main channel and deeper areas tend to have better water quality than sheltered coves, simply because water moves through more quickly and dilutes nutrient concentrations.
Swimming and Recreation
For day-to-day recreation, Old Hickory Lake is considered safe. The state monitors for enterococcus and E. coli, the indicator bacteria used to assess whether water is safe for swimming. When levels exceed EPA standards on consecutive tests, a swimming advisory is issued. No such advisory is currently in place for Old Hickory.
A few practical tips can reduce your risk further. Avoid swimming near stormwater outfalls, marinas with heavy boat traffic, or creek mouths after rain. If you have open cuts or wounds, those are easier entry points for any bacteria present. And if you’re bringing young children who are likely to swallow water, choosing a time when the lake hasn’t received heavy runoff in the prior 48 hours makes a difference.
Fishing and Fish Safety
Old Hickory Lake supports healthy populations of largemouth bass, crappie, catfish, striped bass, and other sport fish. Because the lake does not carry a fish tissue advisory, there are no special consumption warnings beyond Tennessee’s general statewide guidance for freshwater fish. That guidance recommends limiting meals of certain predator species (like largemouth bass and catfish) to a few per month, particularly for pregnant women and young children, due to low-level mercury that accumulates in fish tissue across virtually all Tennessee reservoirs. This is not unique to Old Hickory.
The Growth Factor
The communities surrounding Old Hickory Lake, especially Hendersonville, Mt. Juliet, Lebanon, and Gallatin, are among the fastest-growing areas in Tennessee. More development means more impervious surfaces like roads and rooftops, which increase stormwater runoff volume and speed. It also means more wastewater treatment demand. The lake’s water quality in the coming years will depend heavily on how well infrastructure keeps pace with that growth and whether stormwater management practices limit nutrient-laden runoff from construction sites and new neighborhoods.
For now, Old Hickory Lake meets the standards for safe recreation. It’s not a mountain spring, but it’s a functional, monitored reservoir where swimming, skiing, and fishing are part of everyday life for thousands of Middle Tennessee residents.