erosion/runoff and viz

[ScubaTodd77]

I dive a private quarry that has beautiful blue water topside, but as soon as you descend, viz is always very blurry. Best I've seen it in the 15ft to 35ft range is maybe 20 ft viz. Usually its 0-8ft. Deepest part is 86 ft and it is as black as night starting round 55 ft. Bottom temp year round is a constant 45 degrees. There is a lotta construction going on around the quarry and a huge bare mountain hill, on the south side, but the quarry has tons of kudzu coverage on that end, however the east side has nothing but bare soil with plenty of runoff into the quarry. Other local quarries (within 100 miles) have the same nice blue topside water but with far greater viz. I dive this quarry year round and have been doing so for at least 4 years now. Can anyone explain why a quarry with beautiful blue water would have such bad viz. Viz does open up at the bottom but you would need stadium lights to see any further than 10 ft and there are never any fish in that 45 degree water. In four years of diving there I've seen one soft shell turtle and the rest have been dead fish laying at the bottom...which prolly explains the large soft shell down there. BTW it is a limestone quarry.

 

[g1138]

Limestone in water creates Calcium Carbonate (CaCO3). The water content may be too basic (pH level) to support aquatic life.
I'm having difficulty understanding what you mean about the viz. Is there a midwater area where there's just silt sandwiched between clear water?

 

[soltari675]

We dive in several quarries here in MO. The closest one we have is only about 35ft max. There is no construction nearby but it is all soil around about half of it. The vis is due to a couple reasons. One, the bottom of the quarry is likely silt. So anyone who touches the bottom, even barely, or gets too close with fits will move that silt and it takes a LONG time to settle, killing the vis. Also you have the spring at the bottom which churns the silt right where it comes in. If your quarry is not wide, but just deep and narrow, the bottom will be near 0 vis. Another reason is as the water cools off/heats up on top, the water will do this inversion thing, where the water kinda turns over. When it does, it churns up the silt a lot as well. We have another quarry we go to that is 120ft deep max and it is very very dark at the bottom as well. The light has a hard time getting past the silt and algae. And yes, if you get a lot of rain, you do get runoff which completely kills vis as well.

Fresh water fish don't really like the water in the 40's. If you do winter diving, you'll notice you can pretty much swim up to fish and they don't swim away. They stay still. In the summer, they will stay above the thermocline. As g1138 mentioned, for some fish the pH may be off enough that not all of the fish survive in there. The fish may have been introduced to the quarry, and with no natural predators, some will die just from the quarry not being able to sustain a large population. Eventually it might.

Just some ideas from a fellow quarry diver.

 

[SnorkelLA]

My philosophy- bad vis prepares you for just about any diving situation you can think of- so does pitch black water. Runoff from topside can likely sink and become suspended midwater, or be taking a VERY VERY VERY long time to settle if it's really fine. That's how the bottom of Lake DeGray is. Once you get pretty deep you get away from the rocks that make up the coastline and it's just pitch black as Davy Jone's locker and the silt has been settled for hundreds, maybe thousands or tens of thousands of years because of how deep it is, topside storms rarely affect it. This makes for fantastic vis-provided you have a decently bright dive light- but if you so much as look at that silt wrong it will plume into something resembling Hiroshima!

 

[MXGratefulDiver]

My philosophy- bad vis prepares you for just about any diving situation you can think of- so does pitch black water.

No, it does not ... bad vis prepares you for diving in bad vis. It does nothing to prepare you for surf entries ... or how to deal with current ... or surge. It doesn't prepare you for diving walls or overheads ... or getting back onto a pitching boat.

These are but a few off-the-cuff things it doesn't prepare you for ... heck, it doesn't even prepare you for communicating in crystal-clear water, if you're used to using light signals for communication.

The only thing that prepares you for diving in a given situation is diving in that situation ...

... Bob (Grateful Diver)

 

[SnorkelLA]

No, it does not ... bad vis prepares you for diving in bad vis. It does nothing to prepare you for surf entries ... or how to deal with current ... or surge. It doesn't prepare you for diving walls or overheads ... or getting back onto a pitching boat.

These are but a few off-the-cuff things it doesn't prepare you for ... heck, it doesn't even prepare you for communicating in crystal-clear water, if you're used to using light signals for communication.

The only thing that prepares you for diving in a given situation is diving in that situation ...

... Bob (Grateful Diver)

I was speaking in that if he can handle low vis well and be comfortable in it, he could handle the great vis well. I should have been more clear


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[DivemasterDennis]

We train in a local rervoir that has a substanial inflow and outflow, which make it pretty good vis for a freshwater lake. (15 -25 feet on a good day.) However, it is a silt bottom, and on training weekends it gets kicked up. As the temperature of the water rises, more little acquatic living things bloom, and that reduces viz. More than anything, rain can kill the vis through muddy runoff. Windy day can chrn up stuff that reduces the vis. Interestingly, below about 45 feet, the vis is constant at about 25 feet- too cold down there for the algae an divers to kick up the bottom. One of the "who knew's" of scuba that surprised me years ago when I started diving was that fresh water vis is generally lower than salt water vis. Go figure.
DivemasterDennis