Climate, Snow Cover, Microclimate, and Hydrology 



63 



12 



o _ 



^ 8 



o. 

 I 4 



FIGURE 2-14. Seasonal course (5-day means) of 1972 

 summer soil temperature on the trough, rim and basin of 

 a low-centered polygon at I cm and 10 cm depth. (After 

 Bunnell et al. 1975.) 



a calculated evaporation rate for a standard day (12 July 1973) was 2.3 

 mm, while average pan evaporation rate was 2.3 mm day"' for 10 to 16 

 July. In all cases, transpiration made up only a small fraction (7% to 

 15%) of total water loss. These observations are consistent with those of 

 Rouse et al. (1977) who found evapotranspiration from a shallow tundra 

 lake and a wet sedge tundra essentially identical. 



Soil temperature-moisture studies (Guymon 1976) showed negli- 

 gible vertical water movement in the mineral soil during the summer. 

 This suggests that virtually all rain falling on the dry tundra infiltrates 

 only into the surface organic layer and is subsequently evaporated and 

 transpired. Runoff originates from rain falling directly on ponds and 

 streams and on adjacent low areas where the water table is at or near the 

 surface. 



The runoff data of Brown et al. (1968) show zero flow during ex- 

 tended periods of no rainfall, indicating that the thawing active layer is 

 not a source of stream flow. Similarly, records of pond levels (Brown et 

 al. 1968, Hobbie 1980), pond chemistry (Brown et al. 1968), and lake 

 levels (Kane and Carlson 1973) indicate that in the absence of inlet and 



