The lowest mean water temperature recorded for any month for any stream 

 was 33.4° (January 1953, Indian Creek), The lowest instantaneous temp- 

 erature recorded was 30°, occurring in May, The longest duration of this 

 temperature was 11 hours. Temperatures of 32° occiarred several times 

 durdng January and February, 1953 j and held for as long as 6 days. Temp- 

 eratures of 33° were ccranon and persisted for periods up to 11 days. A 

 layer of ice 6 to 12 inches thick may form in the streams during extended 

 periods of cold weather, but the streams continue to flow under this ice 

 layer. 



Relationship between water temijerature and other factors . Data from all 

 study streams indicated a strong direct correlation between air and water 

 temperature (fig, ll). Other investigators have also found this, and in 

 the absence of canplete water temperature records, air temperatures may 

 be used to indicate them, Snowmelt seems to modify water temperature, A 

 change in time and rate of snoi-melt, or in total snow accumulation, may 

 influence the fresh-water temperature regime. The stream discharge 

 records permit an accurate determination to be made of dates of first and 

 last snowmelt, 



A strong inverse relationship seems to exist between water temperature and 

 stream stage, as shown in fig, H, A lowering stream stage resulted in a 

 rise in water temperature and vice versa. Highest water temperatures were 

 associated with the lowest stream levels; the lowest water temperatures 

 with the highest stream stages. 



During months of light precipitation - June, July, and August - stream 

 stage continuoTOsly lowers c Shallow i-ra-ter responds more quickly to changes 

 in air temperature than does deep water. Mean monthly water temperature 

 of Indian Creek, the shallowest of the study streams, was several degrees 

 colder during winter months, and generally warmed more qxaickly during the 

 summer months than the other streams. Precipitation was found to modify 

 maximum and minimum water temperatures during, and for a period of 2A to 

 48 hoijrs following, a storm but otherwise had little effect. The variations 

 were very small, however, and did not lower average water temperature during 

 the storm period. 



It is not expected that stream temperatures will change significantly as a 

 result of logging. Minimum stream and streambed temperatures are probably- 

 more important considerations than are maximum temperatures in the life 

 cycle of the salmon in Southeast Alaska. Continuing records will be kept on 

 all study streams to obtain water temperature records during all months of 

 the year. 



Stream channel change 



Continuous change in beds and channels of streams is a natural phenomena. 

 Most of the valleys and mountains of both the mainland and the islands were 

 buried under an ice sheet during the Pleistocene epoch, Glaciation has 

 resulted in the formation of broad, flat-floored and U-shaped valleys with 



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