observed over a 9-day period at eight points 

 sampled concurrently in study area D. The 

 least difference between minimunn and maxi- 

 mum readings was l.Z nng./l. while the 

 greatest difference was 4.3 mg./l. Oxygen 

 levels increased slightly with discharge at 

 points low in dissolved oxygen. Points high 

 in dissolved oxygen showed little change with 

 increased discharge. Temperature remained 

 near 52° F. during the period of sampling. 



Seasonal ---Seasonail changes in dissolved ox- 

 ygen content of intragravel water were of 

 large magnitude. Samples were obtained from 

 31 points in study area C during August and 

 November 1957 and during March and August 

 1958 (table 4). Dissolved oxygen levels were 

 at a very low level during August 1957. 

 They had increased significantly, however. 



by November 1957, and a second significant 

 increase had occurred by March 1958. 



There was only a slight decline in oxygen 

 level during August 1958, which was in sharp 

 contrast to the previous year. Furthermore, 

 the mean dissolved oxygen level of points 

 san-ipled was significantly higher during August 

 1958 than during November 1957, despite the 

 fact that water temperatures were approxi- 

 mately 10° F. cooler in November than in 

 August. 



ypariy.- -Examination of dissolved oxygen 

 levels observed in nine study areas during 

 late August and early September of 1957 and 

 1958 revealed that a pronounced difference 

 existed between these years (see appendix). 

 Very low dissolved oxygen levels prevailed 



TABLE A. — Seasonal change In dissolved oxygen content 

 of intragravel water (study area C) 



