Hydrology of Alaska— W aananen 155 



the precipitation at Shungnak is somewhat greater. Tempera- 

 tures range from the low 8o's to the — 50's with sub-freezing 

 temperatures prevailing over most of the year. Annual tem- 

 peratures average about 20°F. 



The variations in climate and topography and the effects of 

 permafrost and glaciers make the hydrology of Alaska highly 

 complex. Permafrost is present in interior and northern 

 Alaska. Though permafrost usually acts as an impervious layer 

 there are opportunities for storage or release of water from the 

 active layer between the ground surface and the permafrost, or 

 changes may occur in the permafrost with resultant changes in 

 the local water regimen. Glaciers may store part of one year's 

 precipitation and release it in another year or years, thus dis- 

 torting the usual pattern of stream flow and the precipitation- 

 runoff relations. 



Surface water supplies are available throughout the territory 

 in summer. Minimum flows occur generally in Avinter. The 

 streams in southeastern Alaska are least affected by winter con- 

 ditions. In interior and northern Alaska the smaller streams 

 are usually immobilized in the winter and the development of 

 such streams for water supplies is complicated by considera- 

 tions of storage, heating and transmission. In many areas, how- 

 ever, potential surface water supplies may be infeasible because 

 of the distances from desired points of use. 



Ground water supplies are available in many areas but up to 

 date definite information has been obtained for only a few 

 areas. Ground waters may provide useful sources at many 

 locations, particularly where surface water supplies are not 

 within easy reach. Little is known yet about the possibilities 

 for ground water development in Arctic areas. As an example 

 of the problem, Eskimos in northern Alaska sometimes obtain 

 their summer water supplies from small wells dug into the 

 permafrost which accumulate water from melting permafrost 

 or ground ice. The subject of Alaskan water supplies is ably 

 discussed by A. J. Alter, Director, Division of Sanitation and 

 Engineering, Alaska Department of Health, in an article "Water 



