I (RESTS 



tion of forested land is entirely un- 

 treated with pesticides of any sort, 

 and the greatest part of the remainder 

 would be treated only at intervals 

 of several to many years. For ex- 

 ample, a single application of 2,4,5-T 

 to control overtopping brush on re- 

 generation areas probably would not 

 be repeated within the life of the 

 new stand. 



Numerous monitoring studies with 

 insecticides such as DDT and its suc- 

 cessor materials during the past two 

 decades have demonstrated the mag- 

 nitude of direct and secondary input 

 into streams to be expected from 

 broadcast aerial applications. These 

 also indicate both the hazards of 

 applying highly toxic or persistent 

 materials in this way and the meas- 

 ures required to avoid or minimize 

 direct contamination of waters. Again, 

 fewer though significant studies with 

 ground and aerial applications of 

 herbicides demonstrate that careful 

 regulation of mode, rate, and season 

 of application allows use even in 

 streamside areas with no or minimal 

 contamination. Since phenoxy and 

 amitrole herbicides degrade fairly 

 rapidly in the forest floor, confining 

 application to places and seasons 

 where overland flow will not occur 

 within a month or two avoids possible 

 runoff. 



But, plainly, continued systematic 

 experiments with pesticides or other 

 easily detected markers under a large 

 variety of field conditions is needed 

 to insure a high degree of predictabil- 

 ity. Moreover, the increasing con- 

 straint on the use of some materials 

 is likely to place a high emphasis on 

 development of nontoxic or easily 

 decomposed materials, and on alter- 

 native strategies of pest control. 



The Effects of Fire — Concentra- 

 tions of dissolved solids in forest 

 streams are normally low, and in- 

 creases of any magnitude are usually 

 associated with major disturbances 

 or additions. From time to time 

 concern has been expressed over the 

 effects of fire, clearcutting or other 



destruction of cover, increased area 

 of nitrogen-fixing vegetation, and 

 forest fertilization. Unfortunately, at- 

 tention is sometimes directed solely 

 to maximum concentrations in the 

 waters from the affected areas. When 

 the aggregate of small watersheds 

 forming a single forested drainage 

 basin is viewed as a system over 

 time, however, events affecting small 

 areas and at long intervals, such as 

 clearcutting in a sustained-yield for- 

 est, necessarily have only minor in- 

 fluences on the quality of large- 

 volume streams issuing from the 

 entire basin. In contrast, drastic 

 large-area events such as a major 

 wildfire or insect pandemic could 

 increase outflow concentrations for a 

 relatively brief period. 



Plant ash remaining after severe 

 fires can temporarily raise the base 

 content and alkalinity of streams 

 from affected areas. Accelerated de- 

 composition of organic matter in and 

 on the mineral surface after fire may 

 increase nutrient outflow, though this 

 has not been demonstrated. These 

 several changes are probably trivial, 

 however, in comparison with more 

 serious and long-lasting effects on 

 water temperature, turbidity, and 

 flow characteristics, especially if re- 

 establishment of cover is long de- 

 layed. 



But fires are of many kinds, and 

 forest landscapes vary enormously in 

 susceptibility to post-fire erosion. 

 Turbid streams, floods, and disastrous 

 mudflows are well-known conse- 

 quences of fire in the steep brush- 

 lands of southern California. (See 

 Figure VII-5) There are many such 

 landscapes with highly combustible 

 vegetation where uncontrolled fire is 

 a major hazard to watershed values, 

 including water quality. Well-docu- 

 mented case histories, as well as 

 small-scale experiments, thoroughly 

 demonstrate the flood peaks, gulley- 

 ing, sediment transport, and channel 

 tilling, as well as long-term impair- 

 ment of water quality following 

 severe wildfires on sensitive soils and 

 slopes. Hence, research on fire be- 



havior and control, fuel reduction 

 prescribed fire, and wildfire detec- 

 tion and suppression are essential to 

 maintenance of water quality. This 

 point is too often overlooked, and 

 efforts at economic analyses or "total 

 social costs" fail to weigh the proba- 

 bility — and overwhelming damage — 

 of major wildfires against the costs 

 and minor damages of roads or other 

 measures that facilitate fire control. 



Disastrous effects on water quality 

 from wildfire are far from universal, 

 however. In some places, wildfire 

 may be followed by significant sur- 

 face washing or mass movement but 

 part or all of the sediment comes to 

 rest and is stabilized before reaching 

 the streams. Furthermore, there are 

 large areas of stable soils and slopes 

 that resist detachment and maintain 

 adequate hydrologic capabilities even 

 after severe fires. 



Much remains to be learned about 

 soil and water behavior following 

 fire, and especially about mass move- 

 ment on steep or unstable slopes, 

 about the possibilities of adverse 

 precipitation events in the interval 

 before revegetation of newly burned 

 surfaces, and about seeding or other 

 measures to hasten such revegetation. 

 The sheer magnitude and obviousness 

 of the immediate post-fire conse- 

 quences, the costs and complexities 

 of long-term studies on large burns, 

 and concern with newer threats to 

 water quality tend to divert attention 

 from quantitative studies of recovery 

 processes. 



Nevertheless, present knowledge 

 allows arraying likelihood and pos- 

 sible extent of wildfire influences on 

 a scale from none to very great, 

 according to landscapes, fuel type, 

 and fire characteristics. Such knowl- 

 edge also allows use of prescribed 

 fire, at times of low hazard, for a 

 variety of purposes — preparation for 

 regeneration, improvement of wild- 

 life habitat, and, notably, reduction 

 of accumulated fire fuels that would 

 otherwise vastly increase wildfire 

 hazards. In most of the southern 



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