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| Technical Bulletin No. 0672: Forests as Nonpoint Sources of Pollution and Effectiveness of Best Management Practices |
| Type: |
Technical Bulletin No. 0672 |
| Published: |
July 1994 |
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| File Size: |
3,800 KB |
Category: |
Reports |
| File Type: |
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(Adobe PDF) |
Frequency: |
As Needed |
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| Bibliographic Citation |
| National Council for Air and Stream Improvement, Inc. (NCASI). 1994. Forests as Nonpoint Sources of Pollution and Effectiveness of Best Management Practices. Technical Bulletin No. 0672. Research Triangle Park, NC: National Council for Air and Stream Improvement, Inc. |
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| Abstract |
This report synthesizes available knowledge on the effects-of forest practices on water quality by examining six propositions:
The quality of water draining forested watersheds is normally the best in the nation whether the forests are left untouched or intensively managed. Available information supports this proposition.
Properly implemented Best Management Practices (BMPs)effectively control nonpoint sources of pollution from forestry operations under most circumstances. This proposition is generally true, but in some unstable areas conventional BMPs for road construction and forest harvest may not be sufficient to prevent adverse effects on stream channels and fish habitat.
Effects of present day management activities on water quality are usually transient and are rarely severe enough to cause significant damage to fish populations. Negative impacts of forest practices should be uncommon where conventional BMPs are used. Exceptions to this conclusion would include (a) unstable areas or areas with highly erodible soils; (b) the combination of management activities with extreme storm events and (c)possibly downstream depositional areas where there is potential for cumulative effects.
The potential for water quality impacts from forest management depends upon factors such as climate, soil types, topography, etc. Special control measures can be targeted where there is greater than normal risk for short- or long-term adverse effects (such as areas with high risk for landslides). This proposition is generally true, although we note that extreme storm events can have unavoidable effects on both managed and unmanaged landscapes and streams. The cost of special control measures may in some situations be prohibitive relative to the value of the reduced risk of water quality degradation.
The water draining forest watersheds is not “toxic” (as defined by the Clean Water Act and elsewhere) unless affected by spills or other unusual events. Water quality issues for forest streams do not involve “toxins,” with the possible exceptions of high nitrate concentrations and high aluminum concentrations. Both of these water quality parameters very rarely exceed toxic thresholds in forest streams.
The direct effects of forest practices on water quality within a small watershed may be different than the cumulative effects of the same practices on many small watersheds within a basin. This proposition may be generally true, but very little comprehensive information is available. Use of conventional BMPs at the site level to maintain water quality may be effective at minimizing cumulative effects within a basin. More research is needed to fully evaluate this proposition. |
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