Still below the limit: fecal coliform in Valdosta river data 2019-01-02

Three weeks in a row! The Valdosta river water quality testing data WWALS obtains through a weekly open records request shows all stations tested below the Georgia state limit last Wednesday.

Graph, Withlacoochee River Basin, Withlacoochee

However, like the week before, there are no data for the two stations at the state line, on the Withlacoochee River and on the Alapahoochee River.

The highest Fecal coliform reading in the Withlacoochee River Basin last week was at GA 133 (St. Augustine Road) at the Withlacoochee River.

GA 133, Withlacochee River, Withlacoochee

There was a slightly higher reading in the Alapaha River Basin, but still below the 200 cfu/100ml Georgia limit.

Graph, Alapaha River Basin, Alapaha

That was at Johnson Road over Mud Creek (which goes into the Alapahoochee River, then the Alapaha, then the Suwannee).

Johnson Road, Mud Creek, Alapaha

Limits

What do all those horizontal lines mean? And what do the colors indicate, both on the graphs and on the WaterReporter map?

Map, Stations

The thick yellow-green line is the Georgia state limit for Fecal coliform in recreational fresh water, from this table:

Georgia Fecal Coliform Standards
Bacteria Levels (Fecal coliform)
Use Classification 30-Day Geometric Mean
(cfu/100 ml)
Maximum
(cfu/100ml)
Drinking Water requiring treatment 1,000 (Nov-April)
200 (May-Oct)
4,000 (Nov-April)
Recreation 200 (Freshwater)
100 (Coastal)
Fishing
Coastal Fishing
1,000 (Nov-April)
200 (May-Oct)
4,000 (Nov-April)
Scenic River No alteration of natural water quality
Wild River No alteration of natural water quality
Source: Bacterial Monitoring, Georgia Adopt-A-Stream.

All the rivers in the Suwannee River Basin are classified by Georgia as “fishing”, but we think they should recreational.

We also observe people swimming (and fishing) year-round, not just May through October, so we think the summer limit of 200 colony-forming units per 100 mililiters (cfu/100ml)should apply year-round.

Nonetheless, we’ve included magenta and violet lines for 1,000 and 4,000 cfu/100ml.

That source also refers to some more thresholds, these for E. coli. Since that’s a specific type of Fecal coliform, we’ve used the same thresholds for both types of bacteria.

Designated
Swimming
Moderate
Swimming
Area
Light
Swimming
Area
Infrequent
Swimming
Area
E. coli
(cfu/100 ml)
<235 <298 <410 <576
(from US EPA 1986, 2002a)

Those designated, moderate, light, and infrequent swimming area designations seem vague and unspecified, but those are the numbers we have to work with. So we used them for letter grades from A+ to F:

  • A+: 0-100
  • A: 100-200
  • A-: Georgia Limit 200 cfu/100 ml to 235 EPA Designated Swimming
  • 235 B+: 235-298 EPA Moderate Swimming Area
  • 298 B: 298-410 EPA Light Swimming Area
  • 410 B-: 410-476 EPA Infrequent Swimming Area
  • 576 C: 576-1,000
  • 1000 D: 1,000-4,000
  • 4000 F: 4,000 and up

Hm, maybe we should use darker colors.

Anyway, the important lines are 200 (or maybe 235), 1,000, and 4,000. If readings are above 1,000 retest and watch out. If above 4,000, steer clear.

Of course, all such indications are merely advisory. It takes 24 hours just to test for Fecal coliform, and conditions could change a lot in that amount of time. Plus what makes one person sick might not affect another.

It does seem safe to assume that the higher the levels of Fecal coliform, the less safe the waters.

More

For more see Water Quality Testing, which includes how you can sign up to help.

 -jsq, John S. Quarterman, Suwannee RIVERKEEPER®

You can join this fun and work by becoming a WWALS member today!

Map in Water Reporter

Here is the map of this data in Water Reporter. Click on one of the diamond shapes to see graphs.

 -jsq, John S. Quarterman, Suwannee RIVERKEEPER®

You can join this fun and work by becoming a WWALS member today!

-jsq

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