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Water Quality

Primary Question (chapter 19): What are the history, status, and likely future of water quality in southern watersheds?

Related Questions (chapter 21): How have forest management activities and other forest uses influenced water quality, aquatic habitat, and designated uses in forested watersheds? (chapter 22): What are the implementation rates and effectiveness of BMPs in the South?

Land uses and management strongly influence the quality of the water flowing from forests. We examined the overall condition of southern water quality and primary sources of water-quality impairment (chapter 19), forest management’s effects on water quality (chapter 21), and the effectiveness of water-quality protection efforts through BMPs employed during forest treatments (chapter 22).

Water quality in the South has been heavily influenced by a long history of intensive land uses. Conversion of forests and forested wetlands to primarily agricultural uses started in the late 1700s, and extensive logging began after the Civil War. These activities resulted in severe soil erosion and heavy sedimentation of nearly all southern waterways. Urban expansion permanently altered hydrology and created chronic point and nonpoint pollution. The legacies of these actions are still evident and complicate our ability to discern the effects of current management and to measure trends in water quality. These historical legacies and the effect of ongoing urbanization continue to influence water quality, stream channel stability, and aquatic life in the South.

Beginning with the passage of the Clean Water Act in 1972, public agencies have focused increasing attention on minimizing pollution—including nonpoint-source pollution—from land-disturbing activities. However, water quality in southern streams and rivers remains variable.

We evaluated key aspects of water quality of southern waters and found:

• Based on a national watershed characterization program, approximately 30 percent of the South has relatively good water quality, 36 percent has moderate water-quality problems, and 15 percent has more serious water-quality problems; approximately 19 percent of the South, primarily in western Texas, does not have sufficient information to provide a characterization of the status of water quality (chapter 19, fig. 46).

• As reported by southern States, the leading causes (pollutants) of water-quality impairment from 1988 to 1998 were siltation and sedimentation, bacteria and other pathogens, and nitrogen, phosphorous, and other nutrients (chapter 19).

• The leading sources of water-quality impairment in the South from 1988 to 1998 were agriculture and urbanization. Approximately 70 percent of all pollution came from nonpoint sources (chapter 19).

As for forest management effects:

• States reported an annual average of approximately 3,600 miles of rivers and streams as impaired by silvicultural activities from 1988 to 1998. Silviculture ranked 10^th out of the 11 major sources of water-quality impairment during this time (chapter 19 and chapter 21).

• Southern forests play an important role in maintaining and improving water quality in the South. Forested watersheds have consistently been shown to have lower sediment and nutrient yields and better aquatic biological conditions than nonforested watersheds (chapter 19).

• When properly implemented and maintained, silviculture BMPs are effective in controlling nonpoint-source pollution. In their absence, however, water quality can be significantly impacted by forest management activities (chapter 21).

• All southern States have adopted voluntary BMPs to protect water quality during silviculture operations. Twelve of the 13 Southern States have conducted surveys to measure BMP implementation; Oklahoma is in the process of conducting its first survey (chapter 22).

• States report generally high rates of implementation. However, compliance rates vary from 35 percent to 100 percent depending on the State, ownership, or BMP category. Overall BMP compliance tends to be highest on public and industrial private land and lower on nonindustrial private land. Direct landowner assistance appears to be positively correlated with proper BMP implementation (chapter 22).

• Differences in monitoring methods among States and within States over time preclude reporting of regional BMP trends (chapter 22).

• There is very little information available on the cumulative effects of past and ongoing timber harvesting and management on overall watershed health (chapter 19 and chapter 21).