Base flow values for the three study streams discussed above are in 

 order of magnitude of size of watershed^. This is a rather strong 

 indication that base flow characteristics are, among other factors, 

 a function of watershed size. 



The effect of deforestation on the minimum flow of streams is 

 variable. Deforestation may decrease interception and transpiration 

 more than evaporation is increased, thus augmenting streamflow 

 whether at flood or at minimum stages. In other cases, denudation 

 has been found to reduce the minimal flow because of an increase in 

 surface nmoff with a resultant reduction of infiltration. Date of 

 summer minimal flow may be later as a result of deforestation. 



Continuing observations will show what effect, if any, clear cutting 

 has on magnitude of base flow and date of occurrence of minimal flow. 



Stream temperatures 



Fresh water temperature plays an important role in the life cycle of 

 salmon in the streams of Southeast Alaska, Temperature may influence 

 the spawning impulse; it influences egg incubation, and fry develop- 

 ment up to the point of emergence from the gravel. Stream tempera- 

 ture exerts its influence on various phases of the life cycle of the 

 salmon during all months of the year. Pink and chvia salmon fry do 

 not remain in the streams during the entire year, but the fry of 

 other species may spend one or more years in the parent stream, A 

 study of fresh water temperatures must, therefore, evaluate con- 

 ditions which occur from the time that salmon enter the stream to 

 spawn until the fry leave the parent stream for salt water. 



Maximum fresh water temperatures . Temperature of fresh water streams 

 in Southeast Alaska is moderate. The highest mean temperature recorded 

 for any month for any study stream was 57,4° (July, 1951, Old Tom 

 Creek), The highest instantaneous temperature recorded during the 

 period 1950 through 1953 on any stream was only 66°, occurring twice 

 during the period of record. Both of these maximum temperatures 

 occurred in Jiily of different years. Of 71 temperatures between 

 61° - 66°, all occurred diiring the months of June, July, and August; 

 5 in June, 3^ in July, and 30 in August, The study streams are 

 generally devoid of pink and chum salmon during these months, with 

 the exception of late August when a few early spawners may enter fresh 

 water. Duration of these maximum temperatures was short, averaging 

 3,7 hours. Longest duration was only 6,5 hours. 



Minimum fresh water temperatures . Water temperature records during 

 late fall and winter are not as complete as are the records during 

 spring and summer, 1953 is the only fuH year of record, covering all 

 months, available from each study stream. These records do, however, 

 permit an evaluation of minimum temperatures experienced during the 

 winter months, 



5/ Size of watershed in square miles: Harris River, 31»8; Maybeso 

 Creek, 15,2; Indian Creek, 8,6, 



33 



