| Date | O2 (ppm) | Nitrate (ppm) | Alk. (ppm) | pH |
| 9/16/98 | 8 | 1.6 | - | 7.35 |
| 2/24/99 | 11 | 4.4 | 52 | 7.5 |
| 10/6/99 | 9.5 | 1.1 | 67 | 6.4 |
| 1/19/00 | 9.2 | undect. | 40 | 11 |
| 10/11/00 | 10.8 | 2.2 | 40 | 6 |
| 10/30/02 | 9.8 | 1.1 | - | 6.61 |
| 10/12/04 | 8.15 | 1.1 | - | 7.75 |
| 10/20/04 | 7.9 | 1.65 | - | 7.8 |
| 12/1/04 | 9.2 | 0.44 | - | 7.9 |
| 11/14/07 | 10.1 | undect. | - | 7.6 |
The chemical data shows Holmes run to be slightly basic in pH. Nitrate levels were surprisingly high considering the amount of bordering vegetation to control runoff from non-point sources. The higher levels of nitrate and slightly depressed oxygen levels are consistent with the biological indicators we used to classify Holmes Run as "fair" in terms of water quality. We only examine a small portion of the watershed, and it would be interesting to get a better look at what the chemistry is like upstream and at Lake Barcroft.
For comparison the class occasionally visits the headwater streams of the Thorton River outside of Sperryville, VA. The watershed of these streams is mostly Shenandoah National Park, and there are few sources of pollution input outside of roads (Rt. 211 and Skyline Drive). Below are a picture and some chemical data taken from this stream.
| Date | pH | O2(ppm) | NO3(ppm) | NH4(ppm) | PO4(ppm) |
| 12/2/06 | 8.1 | 13.4 | undect. | undect. | undect. |
| 12/8/07 | 7.9 | 10.5 | undect. | undect. | undect. |
The chemical data from Thorton River suggests that there is some degree of human input of chemicals into Holmes Run.