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Introduction

The quality of water draining forested watersheds in the South is typically the highest in the country (Brown and Binkley 1993, Clark and others 2000). For this reason, the effects of forestry activities on water quality have been widely studied (Brown and Binkley 1994; National Council for Air and Stream Improvement 1994, 1999; Riekerk and others 1989; Stickney and others 1994; Swank and others 1989). It has been found that pollution impacts on water quality from forestry activities are generally local in nature, short-lived, less frequent, and less extensive in nature than activities related to either agricultural or urban activities (Bethea 1985, Dissmeyer 2000). For a complete discussion on various types and sources of pollution and the relative impacts of silvicultural versus other land use activities on water quality in the South (see chapter 19). Chapter 8 describes the many laws and regulations governing silvicultural nonpoint-source impacts on water quality.

Without adequate controls, however, forestry operations do have the potential to significantly affect high-quality water sources and critical fisheries habitat. Silvicultural operations that can cause nonpoint-source pollution include road and skid trail construction, tree cutting and removal, site preparation and stand regeneration treatments, herbicide application, fertilizer application, and prescribed burning. The major types of potential pollutants produced by these sources include sediment, logging equipment fluids, nutrients from harvested areas and applied fertilizers, forestry pesticides, and increased water temperature or thermal pollution.

This chapter describes how forest management activities and pollutants influence water quality. Prior to the enactment of the Clean Water Act (CWA) in 1972, research on forest water quality examined the impacts of forestry activities characterized by the absence of controls over how and where trees were cut or how they were removed. Since that time, however, water-quality research has begun to focus on the effectiveness of BMPs for maintaining water quality while harvesting trees. In response to the CWA, there is a growing body of research on the effectiveness of BMPs in protecting water quality. Chapter 22 specifically describes the range of appropriate silvicultural BMPs and addresses the effectiveness of BMPs in protecting water quality in the South.

While there is a considerable amount of overlap between chapter 15, chapter 19, chapter 20, chapter 22, and chapter 23, this chapter focuses specifically on the impacts of silvicultural activities on water. From public meetings and written comments obtained when the Assessment was being planned, a list was compiled of major points to address in this chapter. These included:

• Evaluate how these activities have influenced and can influence hydrologic response.
• Include a consideration of all relevant water-quality parameters: biological, chemical, and physical.
• Examine effects of pesticides, sediment, and fertilizer.
• Examine the influence of these activities on municipal water supplies.
• Discuss how impacts may differ depending on the size and intensity of harvest and other treatments.
• Identify any differences in water-quality impacts of hardwood versus pine management and plantations versus natural stands.

Each of these items is discussed in the “Results” section of this chapter, with the exception of the influence of forestry activities on municipal water supplies and designated uses (for a definition of designated uses, see chapter 19). Specific information on these topics was not identified during research conducted for this chapter. However, the impacts of individual water-quality pollutants, including sediment, nutrients, and pesticides/herbicides resulting from forestry activities on designated uses, such as drinking water supply, primary contact recreation, or wildlife habitat, are generally discussed in sections related to individual pollutants.