The Great Valley 139 



able to hold the waters within bounds and destructive inunda- 

 tion may result. Many miles of levees have been built along 

 the stream banks and the cultivation of fertile bottom lands has 

 thus been made possible. Yolo Basin is a level expanse extend- 



Courtesy Stockton Chamber of Commerce 

 FIG. 41. Black bottom lands of Great Central Valley, San Joaquin County. 



ing some 30 miles along the Sacramento River south of Sacra- 

 mento that is subject to annual overflow on which only swamp 

 tules and coarse grasses grow. 



Agriculture an Important Industry in 

 the Valley 



Agriculturally the Great Valley is an important part of 

 California. The determining factor is water. As has been 

 stated, high mountain ranges surround the Great Valley. The 

 Coast Ranges, which lie between the Valley and the sea, inter- 

 cept the moisture-laden winds, and air-currents carry clouds 

 high above the Valley to be condensed and fall as snow and 

 rain upon the higher slopes and crest of the Sierra Range. 

 From these high snow-capped mountains waters in perennial 



