TOPOGRAPHICAL.— THE GREAT VALLEY. 



3 



The area of this lake, however, is quite variable, being considerably larger 

 after a wet season, or especially when several seasons wetter than the aver- 

 age have succeeded each other. The whole region between Kern Lake and 

 Fresno City, near the point where the San Joaquin having descended from 

 the Sierra Nevada turns northward and receives the overflow from the 

 south, is low and marshy, and one in which during the dry season the evapo- 

 ration exceeds the inflow from the streams coming down the Sierra. 



Sections across the Great Valley at right angles to its length show a more 

 or less gradual slope from the foot-hills of the enclosing ranges towards the 

 Sacramento and San Joaquin rivers. From Visalia to the north point of 

 Tulare Lake the descent is four and a half feet per mile, for a distance of 

 twenty-nine miles. Tulare River, from the crossing of the Southern Pacific 

 railroad, Mis at the rate of three feet per mile in eighteen miles. In the 

 extreme southern end of the valley the foil of the land from the vicinity of 

 Bakersfield to Tulare Lake is about five and a half feet per mile for thirty- 

 eight miles. In the section between Firebaughs' and Hills' ferries, the level- 

 lings show that the ground falls from the foot-hills to within four and a half 

 miles of the river at the rate of six feet per mile; thence it is nearly level 

 to within half a mile of the river, which it then approaches with an ascent of 

 one and a half feet per mile. At Banta's the valley is somewhat contracted, 

 and the descent of the ground towards the river more rapid, being at the 

 rate of eighteen feet per mile* 



The northern division of the Great Valley is decidedly narrower than the 

 southern, and gradually diminishes in breadth as we go north. So the de- 

 scent from the edge of the foot-hills to the Sacramento is more rapid than 

 the corresponding slopes in the southern division. Thus the rise from Sacra- 

 mento City to Folsom, at the base of the Sierra, a distance of eighteen miles, 

 is nearly 200 feet. As is usually the case with large rivers in broad valleys, 

 the Sacramento River runs on an elevated ridge, the banks of the river being 

 decidedly higher than the strip of land adjacent on both sides for a distance 

 °f three or four miles. At Colusa this difference of level amounts to as 

 tfiuch as twenty feet, and in heavy freshets caused by the rapid melting of 

 the snows on the Sierra, the river discharges itself in part through sloughs 

 Jnto these adjacent lower areas, which become filled with water, so that a 

 large region is sometimes submerged, the central part of the valley assuming 



Jo; 



* These figures are taken from the " Report of the Board of Commissioners on the Irrigation of the San 



oaqiun, Tulare, and Sacramento Valleys." 



