Columbia, SC (WLTX) - Some folks drive over the Broad River every single day to work and noticed it seems to have changed colors.
Usually it's a muddy brown, murky color, but lately it's been this vibrant deep sea blue color, and we wanted to find ot why.
First, let's tackle why the Broad River is so often muddy, which is referred to as "turbidity," or "matter" in the water. For that we turn to the experts at the U.S. Geological Survey (USGS).
"We've had some pretty hard rains. They [rains] may be relatively short in time, but they've generally been pretty hard, and just that hard rainfall causes some runoff through the upper drainage basin that's coming down, and you'll see the Broad is brown quite a bit of the time," says John Shelton, Associate Director with the USGS in Columbia.
So hard rainfall stirs everything up apparently. But Shelton says there's another possible factor to this equation, and it's going on in the reservoirs upstream.
Shelton says, "Pretty high rainfall events higher up in the basin that's creating the muddy water to come into the reservoirs, and maybe the reservoirs are holding that water."
So that might explain why the water in the Broad is so beautiful blue lately, even though we've had some pretty hard rainfall recently. The reservoirs hold muddy water from upriver rainfall events. Also, by holding that water, the movement of the river is slower, so it stirs up less mud. In that case, it looks like that vibrant blue of the river is only temporary until those reservoirs are opened.
"Then at some period of time they may have to release, so they may release muddier water. So depending on what the reservoir releases are, in relation to the rainfall events, it could vary on what we see as muddy water going to the city," explains Shelton.
Interesting fact; when the Broad and Saluda River meet, forming the Congaree, water gets diverted into the canal at the water treatment plant, which is part of the city's drinking water.
Shelton says, "When the water is muddy or more turbid, that's more matter in the water that they have to filter out. They have to filter out and treat it. So the cleaner the water, the easier it is for them to treat."
So now you know, when the water has that lovely blue color, it means there's less "matter" in it, and the city is having an easier time of delivering clean water to your tap, and that matters.