gravel. In the latter case, water was withdrawn from a perforated pipe 

 which was driven into the gravel. 



Transparency . Water transparency was measured with a 20-centimeter 

 Secchi disc. The depths at which the disc disappeared from sight eind 

 subsequently reappeared were recorded. The average of these two distances 

 is considered the limit of visibility. 



Bottom Particle Size . Stream bottom particle size was deter- 

 mined by two methods. Particle sizes were measured at the riffle stations 

 with a 100-foot tape and graduated calipers. The tape was stretched across 

 gravel which was judged representative in conposition to that being sam- 

 pled for bottom organisms. The intermediate axis of the gravel particle 

 located directly londer each foot-mark was measiored by the use of calipers 

 graduated in millimeters (Wolman, 195^) • This method is useful in com- 

 paring the relative size of gravel in different areas, but has the dis- 

 advantage of not measuring the amD\xnt of ssmd and silt in the gravel. 



Bottom sediment sajnples were taken at stations other than those 

 located on riffles with a Petersen dredge. A pint sample of the material 

 collected was retained and sent to the Department of Water Resources Soils 

 Laboratory for determination of particle size distribution. 



Biological Collections 



Plankton . Quantitative plankton samples were taken from vari- 

 oiis stations throughout the svirvey. These samples were collected with 

 a Kemmerer water sampler. Three samples were taken at midstream and at 

 the quart^er points across the river at a depth of two to three feet. 

 The samples were con5)osited in a one-gallon jug and fixed by euiding sxif- 

 ficient formalin to result in a four percent solution. 



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