secutive days. The purpose of sequential 

 sampling was to obtain a nnean dissolved 

 oxygen value for each point. Mean values 

 are more representative of dissolved oxygen 

 level at the points sampled than single readings , 

 and they are used to describe the dissolved 

 oxygen content of the intragravel water at 

 each point. 



Nine study areas were sampled in 1957 

 and 1958. A brief description of each study 

 area and a sunamary of the sampling effort 

 in summer 1957 and 1958 are given in table 



2. Figure 1 shows the locations of the study 

 areas sampled. 



Temporal changes in dissolved oxygen con- 

 tent . --The dissolved oxygen content of intra- 

 gravel water changes continually at every 

 point with time. Daily changes, seasonal 

 changes, and yearly changes are discussed 

 separately. 



OatZy .--Day-to-day changes at a point were 

 often appreciable and occurred in a random 

 fashion. Table 3 shows daily oxygen levels 



TABLE 2. — Area and location of study areas with respect to tide level, 

 sampling effort, and sampling dates 



TABLE 3. — Daily change in the dissolved oxygen content of intragravel water""" 

 at 8 points sampled concurrently 



[ In milligrams per liter ] 



■"" stream temperatures remained near 52 F. when these observations were made. 



^ Data provided by Northern Experiment Station, U.S. Forest Service, Juneau, Alaska. 



