42 



the occurrence in sequence of years with normal run-off conditions. 



2. The distribution of the seasonal water output to the several months of the year. 



,?. The effect of human activities upon the ri\-er discharge, referring particularly to : 



a. The acceleration of the flood discharge resulting from the reclamation of 



large areas which, under natural conditions, were subject to inundation. The 



4 s 



^ 



10 20 30 10 20 

 April May 



10 20 50 to 20 3/ 10 20 5/ lO 20 JO 10 20 31 10 20 30 10 20 51 

 June July Auqusf -September October November December 



SALINITY or WAim 



1320 



tlAR TlliEZ - Avsraqe Sa/imfy 



Data by 3hell Oil Co 



OTHER STATIONS- Surface at H.qh Tide 



Data by State Water Comission 



vA^-^ 



Ac 



10 20 JO 10 20 Jl 10 10 30 10 20 31 10 20 5/ 10 20 30 10 20 31 10 20 30 10 20 31 



April May June July August ■September October Noyember December 



10 20 30 10 20 31 10 20 30 10 20 31 10 20 31 10 20 30 10 20 31 10 20 30 10 20 31 



April May June July August September October November December 



Fig. 19. Salinity of water at points in Carquinez Strait, 1920. 



natural flood basins acted as retartling basins, prolonging the ri\'er's flood 

 stages, thereby impeding and delaying the arrival of ocean water in the upper 

 bays. The flood basin has already been materially reduced. 



h. The reduction of the discharge of the rivers into Suisun Bay, notably 

 at their low water stages, by the withdrawal of water for irrigation in the deltas 

 of the rivers and at up-river points. 



c. The regulating effect of storage reservoirs tending to augment the low 

 water discharge of the ri\ers. 



d. The accession of return water which, though relatively small in amount, 

 is, nevertheless, increasing as irrigated areas are lieing extended. This not only 

 affects the stream flow but also the quality of the water. The return water 

 contains more mineral matter in solution than the natural river water. 



e. The modifications of channel alignments and dimensions, resulting 

 from work done in building levees and jjarticularly from the work being done 

 by the United States in cooperation with the State in the lower reaches of 

 Sacramento River, which have a material effect upon the tidal flow in the lower 

 reaches of the rivers. 



