CLIMATE 43 



Ovando, at 4,101, has nearly six. It is a matter of further 

 interest in this connection to point to the snowfall in Yellowstone 

 Park at 6,200 feet elevation as being normally Sy 2 feet and at 

 Red Lodge, 5,548 feet elevation in the Absaroka, 9% feet. Both 

 of these stations, which represent the highest east of the Divide, 

 are within 80 miles of the summit and in the direct path of the 

 southwesterly winds which sweep across the range at points un- 

 protected by any high barriers to the windward. The Bitter 

 Roots, which shelter the main divide further north, have no 

 influence here, having merged with the main range some 200 

 miles to the northwest. 



If we reckon 10 inches of snow on an average as equal to 

 one inch of water, the equivalent of the winter's precipitation 

 in acre feet would amount to a considerable volume in stream 

 flow and is important in its relation to power and irrigation. 

 It is an important factor as related to the vegetation of the 

 region. In this respect, however, it is not equally distributed, 

 and much of it doubtless is lost by evaporation, but it is swept 

 by winds into gulches and into sheltered pockets in the lee of 

 peaks where, piled to great depths, it furnishes a constant supply 

 for innumerable streams throughout the warmer season. In this 

 form it is less significant to the vegetation of the crests and 

 exposed slopes, except as these are forested and so enabled to 

 hold the snows that they receive. In such cases, which are 

 numerous, the snows become of the utmost importance, and 

 furnish conditions highly favorable for certain species. The 

 countless lakes and streams fed by the melting snows furnish a 

 natural irrigation system, and by furnishing suitable habitats 

 for trees along their banks facilitate the spread of forests over 

 intervening and adjoining areas. 



Locally rainfall conditions vary within wide limits. The 

 western slopes of the Bitter Roots are amply watered. The 

 rain bearing winds from the west sweep up their high inclines 

 and deposit their burden in frequent showers and heavy snows. 

 There is probably no part of the Rocky Mountains more heavily 

 watered than the higher Bitter Roots and their western slopes, 

 or with snows so deep. In the lee of this range lies the Bitter 

 Root Valley, and Hamilton, near the center of the Valley and 

 at the foot of the mountains on the east has an annual rainfall 



