Water Transpeirency 

 Water transparency was measiired by use of a 20-centimeter Secchi 

 disc. The depth at which the disc disappeared from sight was recorded. 

 Although this reading is subject to a number of errors, it is a useful 

 qualitative indication of water clarity. Figure 12 shows that transpar- 

 ency was reduced from a range of about 80 to 200 inches at Keswick to 

 from 10 to i+0 inches at and below Sacramento- Seasonal reductions are 

 due to unregulated storm inflows during the winter and to plankton levels 

 and to waste discharges during the summer. The relationships between 

 transparency, turbidity, ajid light transmission characteristics are dis- 

 cussed in greater detail in Chapter IV, Appendix B. 



Sediments 

 Bottom particle sizes were determined at all stations. Although 

 there were local differences between closely-spaced san5)ling points, the 

 averaged data shown in Figures 13 and lU indicate the general pattern 

 of particle size distributions in the river. Stations at miles 217.6, 

 168.2, lij-l+.l, 90.5, 81.5, 62.6, 37.2, 18.8, and 12.8 were resampled at 

 varying interveils; seasoneil variations at individual stations were about 

 the same as variations between closely-spaced points sampled at one time. 



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