168 CONSERVATION OF GROUND WATER 



forest or grass cover on the land are the minimizing of over- 

 land flow from intense storms and the protection of the soil 

 from erosion when overland flow does occur. A major factor 

 in these benefits is the increased infiltration under such cover; 

 surficial forest litter is exceedingly permeable, and as far down 

 as roots can penetrate, the plant material will increase the 

 permeability of soils, particularly those which are mineralogi- 

 cally of dense texture. 



Proof that by our use of the land we can change the propor- 

 tion of water that will infiltrate into the ground is no longer 

 limited to the results of research in experimental areas. The 

 nationwide program of soil conservation, embraced by more 

 and more of the public in the past 15 years, has done much to 

 reverse the trend of progressive erosion and deterioration of 

 soil. The return of once-cultivated land to forest or grass cover, 

 contour farming, strip cropping, terracing, and other prac- 

 tices have been successful in reducing runoff and getting more 

 water into the soil, as shown by reports from farmers and 

 others in many sections of the country. 



On the other hand, the several factors controlling the infil- 

 tration-runoff proportion vary so greatly over the nation that 

 it is difficult to make generalizations as to the effect of specific 

 land practices upon the water resources. As an example, it 

 is common practice in some parts of California to burn the 

 brush cover of foothill slopes used for stock range. An effort 

 has been made to determine the effect of this practice upon 

 the water resources, based on analysis of field studies, experi- 

 mental research, and expert opinions. The conclusions from 

 this analysis are as follows: 11 



Evidence is presented indicating that removal of vegetative 

 cover will increase both runoff and erosion by decreasing the in- 

 filtration capacity of the soil and through some changes in soil 

 structure. There is also the contrary evidence that burning has 



11 Adams, Frank, P. A. Ewing, and M. R. Huberty, "Hydrologic Aspects of 

 Burning Brush and Woodland Grass Ranges in California," Calif. Div. Forestry 

 rept., p. 78, January 1947. 



