described a method for measuring seepage 

 rate with equipment designed for permanent 

 installation in the streambed. 



Equipment required for measuring seepage 

 rate is expensive. Furthermore, it is possible 

 that the sampling effort required for statisti- 

 cal precision in nneasuring seepage rate in a 

 natural stream will limit the application of 

 this equipment. 



Compared with measuring seepage rate, 

 measuring dissolved oxygen content of intra- 

 gravel water is a simple task requiring in- 

 expensive equipment. It is also possible that 

 oxygen content alone will provide a suitable 

 index of quality of intragravel water in terms 

 of survival of salmon embryos. 



In view of these considerations, it is sur- 

 prising that more attention has not been given 

 to the observation of dissolved oxygen content 

 of intragravel water and to the manner in 

 which oxygen levels change with time and 

 differ between sites. Based on samples ob- 

 tained from nine points, Wickett (1954) made 

 comparisons of oxygen levels among areas 

 having normal gravel, consolidated gravel, 

 and heavy silt deposits. Chambers, Allen, 

 and Pressey (1955) sampled dissolved oxygen 

 content of water seeping through salnnon redds 

 by withdrawing 250 -ml. water samples from 

 standpipes driven into the streanabed. They 

 found much spatial variation. Data on oxygen 

 levels presented by Gangmark and Bakkala 

 (1959) showed temporal changes in dissolved 

 oxygen content of intragravel water to be of 

 considerable magnitude, but their data were 

 not intended to define precise relationships 

 between time and oxygen level. 



Observation of the dissolved oxygen content 

 of intragravel water was undertaken by the 

 Fisheries Research Institute in 1956 as a 

 part of a study to evaluate the effects of log- 

 ging on productivity of pink and chum salmon 

 spawning streams in the Hollis area of South- 

 eastern Alaska. The study was financed by 

 the Bureau of Commercial Fisheries, with 

 Saltonstall -Kennedy Act funds. Figure 1 shows 

 the location of streams where the reported 

 observations were made. 



The study of dissolved oxygen content of 

 intragravel water had two broad objectives: 

 (1) to establish whether or not oxygen supply 

 was an important factor associated with mor- 

 tality in spawning beds and (2) to develop 

 sampling techniques whereby dissolved oxygen 

 level could be measured routinely as an index 

 of environmental quality as it pertains to 

 mortality of salmon embryos. It is the purpose 

 of this paper to describe the methods adopted 

 to obtain samples of intragravel water for 

 the analysis of their dissolved oxygen content 



and to report observed spatial differences and 

 temporal changes in dissolved oxygen levels. 



The author wishes to acknowledge the many 

 helpful suggestions given by William L.Sheri- 

 dan, who was project leader during the period 

 this study was conducted. 



SAMPLING ESTTRAGRAVEL WATER FOR 

 DISSOLVED OXYGEN CONTENT 



It will be shown that dissolved oxygen 

 levels of intragravel water vary greatly in 

 space and with time. The nature of these 

 variations requires that large numbers of 

 oxygen readings be obtained simultaneously 

 if precise estimates of dissolved oxygen levels 

 are desired. It is also essential that water 

 samples be as small as possible to avoid 

 "contamination" of the sample with water 

 from other strata. The sampling requirements 

 therefore dictate to a great extent the design 

 of equipment and the methods employed. 



Obtaining Water Samples from Standpipes 



Water samples were obtained from stand- 

 pipes which were open cylinders having 20 

 holes, three -sixteenths of an inch indiameter, 

 spaced in the lower 3 inches of pipe. A small 

 hand drill was used to make the 3/l6-inch 

 holes. Standpipes were constructed of rigid 

 plastic pipe sold under the trade name 

 "Carlon." The inside diameter of the pipe 

 was three-quarters of an inch. 



Standpipes were driven into the streambed 

 with a driving rod as illustrated in figure 2. 

 The removable driving rod eliminated the 

 need of having a solid head on each standpipe. 



For routine sampling, the pipes were driven 

 to a depth of 10 inches beneath the streambed 

 surface. At this depth intragravel water could 

 enter a standpipe only from 7 to 10 inches 

 beneath the surface of the gravel. It was 

 observed that pink salmon commonly buried 

 their eggs at this depth inHoUis area streams. 



After a standpipe was driven into the streann- 

 bed, turbid water was removed by pumping. 

 Terhune (1958) described a vacuum pump that 

 was efficient for removal of turbidity. Stand- 

 pipes were left overnight before dissolved 

 oxygen determinations were made, since driv- 

 ing a pipe and clearing it of turbidity disturbed 

 the streambed and may have temporarily 

 facilitated the infiltration of above -gravel 

 water. 



A plastic standpipe could be driven into the 

 streambed three to eight times, depending on 

 gravel size and compaction, before damage 

 to its lower edge made it unserviceable. 

 Damaged standpipes were made serviceable 



