6 Vnivcrsitij of California Publications in Zoology [Vol.22 



as applying here, but some points will receive special notice for the 

 purpose of comparing' conditions there and here when the data will 

 permit.* 



GENERAL FEATURES OF THE SAN JOAQUIN RIVER BASIN 



Tlie writer has not yet had sufficient opportunity to collect detailed 

 information on this topic. The California report by Clapp and Hen- 

 shaw (1909), to the United States Geological Survey, upon the surface 

 water supply gives an excellent discussion of the most important fea- 

 tures and it forms the main basis for this present brief discussion. 



GENERAL CHARACTERISTICS 



Two points of difference from the typical river basin in its latitude 

 are interesting characteristics of the San Joaquin. First, its drain- 

 age is northwestward away from the equator. Second, it consists 

 throughout of a rather deep trough witli comparatively abrupt sides 

 and unusually flat bottom, the level of which is repeatedly broken by the 

 deltas of tributaries entering in most eases very nearly at right angles. 

 The land surface. varies markedly in character with the differences in 

 these tributaries, but with a constant tendency to the formation of 

 swamps and marshes at the lower points through the deposit of the 

 lighter organic matter not left in the tributary deltas. This condi- 

 tion is very prominent from some distance above Stockton on to the 

 mouth of the river. Stockton itself is on the eastern border of an area 

 of swampy peat land through which the course of the river can be 

 maintained only by extensive systems of levees. Even then great 

 stretches of the lower levels are inundated each year, and Stockton 

 has the perennial problem of escaping from floods. 



It is quite evident from the foregoing that the lower valley as a 

 whole is fertile, with a deep soil of goml texture. The lower part is 

 fairly well settled but there is as yet no adequate control of tlie water 

 supply and an extensive area is practically undeveloped. The few 

 cities are small and far apart. None of them is so situated as to 

 cause any appreciable contamination of the river water near Stock- 

 ton. The whole basin is under the direct influence of the "dry" and 

 "wet" seasons. With its low levels, this results in sluggish, almost 

 stagnant flow of the main river during the first, and a brisk flow during 

 the run-off of flood waters incident to the second. 



* This paper is published by permission of Dr. H. M. Smith, commissioniT of the 

 United States Bureau of Fisheries. 



