sources of pollution in 68, 62, and 43 percent, respec- 

 tively, of the hydrologic basins inventoried through- 

 out the Nation. The same study showed mining and 

 silviculture as nonpoint sources in 30 and 15 percent 

 of the basins, respectively. As one would expect, the 

 proportion of the basins affected by the latter two 

 activities is highest in those regions where mining and 

 silviculture are most widespread. Again, it is impor- 

 tant to note that only several of the individual basins 

 listed as being affected by these activities are actually 

 problem areas. And the severity of the problem 

 within that basin, or even within that State, is gen- 

 erally minor in relation to other sources of nonpoint 

 pollution. Pollution from these sources can be signifi- 

 cant on a local basis, however. These and other 

 nonpoint sources of pollution and types of pollution 

 are summarized in table 7.14 in relation to the various 

 regions of the Nation. 



The most serious effects of nonpoint source pollu- 

 tion from forests and range lands are expected to be 

 on recreational uses in remote areas where land man- 

 agement activities are currently taking place. Other 

 serious effects can occasionally be expected in rela- 

 tion to fish spawning areas and in municipal water- 

 sheds for small towns where water treatment facilities 

 are minimal. Impacts on health will generally be 

 minor, but the use and enjoyment of water bodies 

 within forests and range lands are Hkely to be reduced 

 by nonpoint source pollution. If the effects of this 

 pollution are severe enough, local recreation-based 

 ventures could be affected economically. 



The increased emphasis on controlling nonpoint 

 source pollution has had a direct impact on manage- 

 ment activities and uses of forest and range lands. 

 Water quality objectives are being considered when 

 making decisions about land use and management. 

 Land and resource plans and implementation oppor- 

 tunities for all proposed projects must recognize 

 potential nonpoint source pollution, and insure that 

 all possible means are taken to prevent such pollu- 

 tion. 



This increased emphasis also requires a new way of 

 thinking about nonpoint source water quality stand- 

 ards and about how to meet them. Management 

 activities now reflect "best management practices" as 

 the best method of controlling nonpoint source pollu- 

 tion. The concept of best management practices is 

 based on the premise that if land management activi- 

 ties are carried out under the best management prac- 

 tices known, the level of nonpoint pollution will be 

 acceptable. Management decisions incorporating best 

 management practices for grazing, silviculture, min- 

 ing, and construction will determine to a large extent 

 the success of the control and abatement of nonpoint 

 source pollution from forest and range lands. 



Figure 7.11 





Relationships Between Land Use a 



■ 



nd Nutrient Concentrations in Streams 



IgH > 90% Forest 

 m > 75% Forest 

 im > 50% Forest 



■■1 



H^^l > 75% Cleared Unproductive 



BHHHJi 



l^^l > 50% Cleared Unproductive 







HH^I 



HHI Mixed 







HH^HI 



m^m > 50% Range. Remainder Predominantly Forest 







^^^I^HHII 



^^^ > 75% Range 







HHHIi 



^^mm > 50% Range: Remainder Predominately Agriculture 



^^^^^m 



I^^^HH > 50% Agriculture 







HHi^^^^^H 



mm^^ > 40% Urban 





i^^^^^^^^^m ^ 





^^^^^^^^^^^^^^^^^1 ^ 75% Agriculture 



>90% 



1 1 1 1 1 



1 1 1 1 1 1 



0.2 0.1 12 3 4 5 6 

 Total Phosphorus Total Nitrogen 

 Concentration, in Milligrams per Liter 



.«». . .^sik. _ .^dk. ^j^^L .^MJ^Hi^l 



ly 



Wmm 





'■«^ 



^m 







^. 2^^-^ .f^ 





■..::'-._ 



— * 



'"' ' -.if ■ 





-,.: . ; ■; 



Sediment from soil erosion is a major pollutant in many streams and 

 reservoirs. 



Opportunities for Mitigating 

 Water Problems 



As indicated in preceding sections, water problems 

 generally fall into three categories: inadequate sup- 

 plies, flood damage, and low quaHty. Management of 

 forests and rangelands presents opportunities for 

 mitigating each of these problems. It is obvious that 

 forest and range land management offers a solution 

 to these problems only in conjunction with other 

 approaches, but it can in some instances be a signifi- 

 cant element in an overall approach that includes 

 both structural and nonstructural problems and 

 mechanisms. 



308 



