Izaak Walton League
Save Our Streams Monitoring
Sligo Creek
The Friends of Sligo Creek Water Quality Committee began monitoring a site in the downstream portion of Sligo Creek regularly using the Izaak Walton League's Save Our Streams method in spring 2008. The location can be seen on this map. One reason we picked this site is that it sometimes has been found to have small minnow mayflies, once in a study commissioned by the WSSC in September 1994 and another time in a macroinvertebrate survey by Friends of Sligo Creek in June 2005. We are not aware of any other part of Sligo Creek where small minnow mayflies are so regularly found. Another reason is that the location is among the most beautiful in Sligo Creek, occuring right at the transition from the Piedmont to the Coastal Plain geological regions.
If you are interested, please email Alessandra Sagasti. Please come out and join us!
In the Save Our Streams method, letter codes (A = 1-9, B = 10-99, C = 100 or more) are used to record the number of organisms. The number of organism types found under each category (sensitive, less sensitive, and tolerant) are multiplied by the indicated index value. While the A, B, and C ratings do not contribute to the water quality rating, the letters track the population size in each category to see how the macroinvertebrate community changes over time.
| Sensitive (index value=3) | Less Sensitive (index value=2) | Tolerant (index value=1) |
|---|---|---|
| Caddisflies (except net spinners) | Dobsonflies Crayfish | Aquatic worms |
| Mayflies | Fishflies Scuds | Black flies |
| Stoneflies | Common net spinning caddisflies | Midge flies |
| Water snipe flies | Crane flies Aquatic sowbugs | Leeches |
| Riffle beetles | Damselflies Clams | Lunged snails |
| Water pennies | Dragonflies Mussels | |
| Gilled snails | Alderflies |
Water Quality Rating
| Excellent (>22) | Good (17-22) | Fair (11-16) | Poor (<11) |
|---|
| Date | Rating | Small Minnow Mayflies | Watersnipe flies | Riffle Beetles | Fishflies | Common netspinning caddisflies | Crane flies | Scuds | Aquatic Sowbugs | Clams | Aquatic worms | Leeches | Black flies | Midge flies | Lunged snails |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| August 2, 2010 | Poor (10) | A (index value=3) |
- | - | - | A (index value=2) | - | - | A (index value=2) | - | A (index value=1) | - | A (index value=1) | A (index value=1) | - |
| May 16, 2010 | Poor (10) | B (index value=3) |
- | - | A (index value=2) | B (index value=2) | - | - | - | - | B (index value=1) | - | - | B (index value=1) | A (index value=1) |
| October 31, 2009 | Poor (9) | A (index value=3) |
A (index value=3) | - | - | A (index value=2) | - | - | - | - | A (index value=1) | - | - | - | - |
| July 11, 2009 | Fair (15) |
B (index value=3) | A (index value=3) | - | - | B (index value=2) | A (index value=2) | - | - | A (index value=2) | B (index value=1) | - | - | B (index value=1) | A (index value=1) |
| April 19, 2009 | Poor (7) | - | A (index value=3) | - | - | A (index value=2) | - | - | - | - | A (index value=1) | - | - | B (index value=1) | - |
| October 4, 2008 | Poor (10) |
A (index value=3) | - | A (index value=3) | - | A (index value=2) | - | - | - | - | A (index value=1) | - | - | A (index value=1) | - |
| July 28, 2008 | Poor (7) |
A (index value=3) | - | - | - | B (index value=2) | - | - | - | - | A (index value=1) | - | - | A (index value=1) | - |
| April 13, 2008 | Poor (8) | - | - | - | - | A (index value=2) | - | A (index value=2) | - | - | A (index value=1) | A (index value=1) | A (index value=1) | A (index value=1) | - |
Here are the results of a general macroinvertebrate survey Friends of Sligo Creek carried out at this site in 2005:
| Date | Total | Mayflies (Ephemeroptera) | Caddisflies (Trichoptera) | True Flies (Diptera) | Leeches | Aquatic Worms (Oligochaeta) |
|---|---|---|---|---|---|---|
| June 4, 2005 | 29 | 8 (small minnow mayfly) | 3 (netspinner caddisfly) | 15 (7 black fly, 8 midge) | 2 | 1 |