Turnover at SML

[chrisw]

I’ve read ad nauseam about the fall turnover in stratified lakes over the years. But I can’t say I know how to recognize it, or know for sure when it would happen seasonally at SML.

But if I had to guess, I’d say it’s probably going to be soon with the temperature drops and more frequent cold fronts. So who knows when turnover will be, or has it already started? And does it happen lake wide at the same time, or is it spread out from the upper ends to the dam? Once it does happen, what is the immediate change to striper activity, if any?

[31Airborne]

Prob hasn't happened yet - water is still too warm. Once WTs drop into the 50s it'll start.

Cold water is denser than warm water, therefore, heavier. As the top layer of water cools in the fall, it sinks. This process of sinking and mixing w/ the lower tiers of water create a churn (turnover). In many places on any given lake you'll see sediment from the bottom brought up to the surface layer by this churn. The lake can look silted, much like it does after a hard rain. The water can have a heavy, musty smell. The water also goes thru a period where the dissolved oxygen (DO) levels are low throughout the water column. This shuts the fish down (the dreaded 'turnover bite'). Does not happen everywhere at once. It occurs in phases, kinda like the spawn. On a lake the size of SML, the turnover may take weeks.

I agree w/ you that this week's colder weather will kick off the process, but we need a period of sustained cold to bring on the turnover.

[chrisw]

Does it usually start upriver and work toward the main basin, or the other way around? Shallower water should cool faster, so I would guess it would start upriver, but not sure. I wouldn’t think there would be a lot of difference in timing at the back of relatively short creek arms, even though they are shallow, but rather at the upper ends of the river arms, which are many miles away from the lower lake.

Is there much musty smell at SML? In a pond I would expect a strong smell, but the lake, especially the main basin, is pretty infertile, so may not be very noticeable.

[31Airborne]

Based on my observations, the turnover starts in the rivers and backs of creeks then progresses from shallower water to deeper. I'm sure someone has done some work on this. Prob worth some time rooting thru open source data.

I have picked up on the musty smell at SML in a few places. The smell isn't a function of biomass (plankton). It's caused by sediment, much of which is organic matter, being churned up off the bottom by the turbulence.

You'd be surprised how fertile SML is. Remember: it's fed by two major rivers and a host of creeks. All of these tributaries run thru agricultural areas at some point, giving them plenty of opportunities to pick up animal waste and ag fertilizer run-off. Then there's the run-off from residential areas. More fertilizer. Collectively, SML gets a steady feed of nitrogen and phosphorous. Lotsa food for phytoplankton and algae.

[gatorbait69]

I'm in Florida but take a few trips up to SML every year. My sucess is based on reading reports and I read a few in mid September that the turnover had already taken place. I didn't understand it based on water temperature but Dwayne from Captain's Quarters reported that it had already happened. I believe Billy Kohls also reported that it was a week away from happening in mid september. Interested to hear more thoughts on this.

Check this out.

www.smithmountainlakefishing.com/fishingreport

[31Airborne]

Not likely - was way too warm in SEP.

[greg]

I've always heard about the fall turnover of the lake, but like many I don't know how to recognize it for sure. I fish out of Hardy most of the time because it's convenient, and I find there's less congestion and traffic on that end. Back in September the water was really clean and visibility was great, which is my preference. Then all of a sudden the water was stained with less clarity, and there had been no rain to cause this change. Several people I talked to said it was because of the turnover, so maybe it has happened.

[chrisw]

I went out yesterday with some first class mates and took a screenshot of my sidescan. It looks like there is still a definite line between 25 and 30 feet depth. Not much visible on traditional sonar, but that is typical even in the summer months. So it looks like the thermocline is still present in the main lake region of the Roanoke where I was.