182 CONSERVATION OF GROUND WATER 



1 



A considerable fund of data has been developed as to the 

 water cost of vegetative cover. Some of this cost is in precipi- 

 tation that never reaches the ground but is intercepted by 

 trees or other vegetation. Interception is reported to account 

 for as much as 6 inches of water a year in some places. Experi- 

 ments have shown that water cost may be reduced by cutting 

 some of the timber, and thus reducing the interception of 

 precipitation. 20 Research in numerous experimental areas in 

 the West has shown the comparative water costs of various 

 types of vegetation. 



Davis County Addition to Wasatch Forest, Utah. 21 This 

 experimental area on the steep west front of the Wasatch 

 Range was established in 1934, after it had attracted nation- 

 wide attention to its devastating mud-rock flows in 1923 

 and 1930. Intense local rainstorms of the "cloudburst" type 

 are common to the area in summer, and the slopes are so 

 steep that soil or rock fragments are readily removed if not 

 held down. 



The mud-rock flows are a spectacular form of erosion and 

 deposition. In a few hours following a single storm, thou- 

 sands of tons of unsorted rock fragments ranging from clay 

 to large blocks have been spewed out of the mouths of 

 canyons and onto the Great Salt Lake valley plain. On the 

 productive land of this plain these sediments have spread 

 out over many acres, with a thickness as great as 12 feet 

 in the most destructive floods. Some of the small streams on 

 the Wasatch front have an average gradient of 50 per cent, 



20 Wilm, H. G., and E. C. Dunford, Effect of Timber Cutting on Water 

 Available for Stream Flow from a Lodgepole Pine Forest, U.S. Dept. Agr. Tech. 

 Bull. 968, 1948, 43 pp. 



21 References: Croft, A. R., Water Loss by Stream Surface Evaporation and 



Transpiration by Riparian Vegetation, Trans. Am. Geophys. 



Union, vol. 29, pp. 235-239, 1945. 

 Thomas, H. E., and W. B. Nelson, Ground Water in the 



East Shore Area, Utah, Utah State Engr., 26th Bienn. Rept., 



pp. 109-119, 1948. 

 Croft, A. R., A Water Cost of Runoff Control, Jour. Soil 



and Water Cons., vol. 5, pp. 13-15, 1950. 



