FOEEST RANGERS 8 CATECHISM 9 



4. Does the forest influence the melting of snow as well as the 

 distribution of rainfall? 



Yes. In sections of the country where there is much snow, the 

 influence of forests in retarding snow melting is more important 

 than its effect on the disposition of rainfall. Snow melting may 

 begin earlier in the woods, but it usually lasts from four to eight 

 times longer than on open ground. Moreover, as the forest soil is 

 likely to freeze less deeply than soil in the open, it absorbs more of 

 the snow water. Spring freshets from melting snow on bare slopes 

 are an important source of river floods. By delaying the melting of 

 snow and feeding part of the snow water into the soil, forests prolong 

 the period of run-off, reduce flood crests to that extent, and equalize 

 stream flow in the rivers so fed. 



5. What is the most favorable condition of water conservation in 

 California? 



Where precipitation comes in the winter, as in California, storage 

 of water for use during the dry growing season is necessary. Surface 

 storage in reservoirs is desirable but is limited in some localities by 

 scarcity of sufficient desirable reservoir sites. California, however, is 

 uniquely favored by having beneath its great valleys, porous soil 

 [formations winch constitute great underground storage reservoirs, 

 into which the water from the streams is sunk by being spread upon 

 the gravelly out wash fans at the mouths of the streams. 



The maximum storage of run-off water in these underground 

 basins depends upon (1) regularity of flow and (2) the clearness 

 of the water. Water coming in sudden floods escapes largely to the 

 sea as waste, defying storage in reservoirs, while the mud which it 

 carries clogs up spreading grounds and thus prevents the water from 

 finding underground storage. The maintenance upon watersheds of 

 a vegetative cover, with its accumulation of dead-leaf mulch is the 

 only feasible means of human control of these factors. While a 

 forest is perhaps the most effective cover, any other vegetation, such 

 as chaparral, which will deposit a good mulch, is valuable. Whether 

 fire destroys the forest or not, it always burns up this mulch and 

 bares the soil; and before a new cover can grow and another mulch 

 be established, erosion has started its deadly work of removing 

 fertile soil and sealing the channels of underground water. 



6. How does the removal of forest cover by fire or destructive 

 logging affect the water supply? 



By the removal of the forest cover its water-absorbent qualities 

 are lost. The result is increased surface run-off and accelerated 

 erosion. Erosion loads the -water with sediments, which, in turn, 

 fill surface reservoirs and destroy their storage capacity and pre- 

 vent the sinking of run-off flow into underground storage basins. 

 Muddy water seals up the percolating channels. 



7. What is the meaning and significance of " accelerated erosion " ? 

 "Accelerated erosion " is erosion of soil increased above the rate 



which existed before land was cleared or burned over. Increased 

 silt and sediment in streams are direct evidence of increased super- 



