In the absence of controlling measures such as Best Management Practices (BMPs), silvicultural operations have the potential to significantly impact general water quality by generating nonpoint-source pollution.
From 1988 to 1998, an annual average of approximately 3,600 miles of rivers and streams were considered potentially impaired by pollution from silvicultural activities throughout the South.
When compared with other land uses in the South, silvicultural activities are consistently found to be minor nonpoint sources of water-quality impacts (see chapter 19). Silviculture was one of the lowest “leading sources” of pollution or impairment for rivers and streams between 1988 and 1998 as reported by Southern States.
BMPs are critical in mitigating water-quality degradation from silviculture. When appropriately implemented and maintained, BMPs are very effective in controlling nonpoint sources of pollution. They are particularly important in areas with steep topography.
On an individual site basis, most water-quality impacts are short term (first several years after harvest), decreasing over time as vegetation regrows. However, there is very little information available on the cumulative effects of past and ongoing timber harvesting on overall watershed health.
The major potential nonpoint-source impact resulting from silvicultural activities is sediment from roads and skid trails. Other minor nonpoint-source impacts on water quality include short-term increased peak flows during storms; short-term increased base flows; short-term increased nutrient concentrations (primarily nitrogen and phosphorous); short-term increases in herbicides, fertilizers, and derivative products; and thermal pollution (increased stream temperature).
