dissolved oxygen, nitrate concentrations, dissolved solids, suspended sedinnent, 

 pesticides, and temperature. Relationships between management and various forms 

 of water pollution depend on the management practices used at the site. 



Compliance with best management practices where they exist generally results 

 in water quality that is within standards. Across the 50 States, 23 have voluntary 

 best management practices programs, 13 have regulatory programs, 5 use a 

 combination of voluntary and regulatory measures, and 9 lack a formal program. 



Generally, the quality of water draining from forest and rangelands is very good. 

 However, the review of available information indicates that the three principal con- 

 cerns over forest management are suspended sediment, nitrates, and water tempera- 

 ture, with suspended sediment being chief in importance (fig. 26). In a few specific 

 locations, timber harvest can markedly increase nitrate levels. High levels of sus- 

 pended sediment and adverse stream channel changes are potential problems in 

 some regions, especially following road construction and some harvesting and 

 grazing practices. Removal of overstory from along streambanks can raise water 

 temperatures enough to adversely affect fish survival. 



Water Demand-Supply Comparisons 



It is apparent that precipitation provides enough surface and ground water (1 .4 trillion 

 gallons a day) to meet present and prospective withdrawals (some 500 billion gallons 

 a day by 2040). By 2040, water consumption will still amount to only 10 percent of 

 precipitation. There are, however, serious imbalances caused by the geographic, 

 seasonal, and annual variations in supplies. 



Figure 26 — Suspended sediment is tlie most important concern about the effects of forest management on 

 water quality. 



45 



