from 88 days at Hebgen Dam to 112 days at Three Forks. The average 

 annual precipitation at Ennis is 10.69 inches. Ordinarily about 59 

 percent of the total precipitation for the season falls between May 

 and September,, Snow may fall as late as mid- June or as early as Labor 

 Day. 



The rapid rate o f flow of the Madison River and the warming 

 effect of seepage and springs generally prevents solid ice from forming 

 on the river Such ice as does form is usually in the form of frazil 

 ice and usually occurs in the area just above Madison Reservoir. Dur- 

 ing extreme winters, ice may jam-up in the area above Madison Reservoir 

 and causes flooding of the floodplains as far upstream as 2$ miles 

 Effects of ice formation were not studied during thi3 investigation, 

 but some damage to the fishery undoubtedly occurs when ice forces the 

 river out of its banks and onto the flcodplain. 



Southwestern Montana is sparsely populated. For instance, 

 Madison County, which straddles the Madison River throughout most of 

 its length, has a population of only 5 S 998 or 1<,7 people per square 

 mile. There are only six towns in the Madison Valley; namely? Three 

 Forks, Ncrris, McAllister, Ennis, Jeffers, and West Yellowstone,, 

 These are all relatively small;, having a combined permanent population 

 of about 2,000 people,, The population of most of these towns is 

 materially increased by temporary residents during the summer. This 

 is especially true of West Yellowstone where the temporary population 

 may increase to as many as 2,000 people, a tenfold increase over the 

 winter population 



The economy of the Madison Basin is based upon livestock 

 grazing, and, particularly in the lower valley, wheat farming. Trade 

 from fishermen and tourists is an important source of revenue to 

 residents of the valley during the summer. Winter and summer range 

 for elk, deer, and moose is extensive and big-game hunting also is 

 important to the economy,, Prior to World War II, gold mining was an 

 active industry; but most of the mines have now been olosed and some 

 2,000 miners and their families, who formerly represented a large part 

 of the local population, have moved away. 



The Madison River can be reached at Three Forks by east-west 

 U. So Highway 10, at Norris by a good gravel road between Bozeman and 

 Norris, and at West Yellowstone by north-south U„ S. Highway 191. State 

 Highway 1 parallels the river from McAllister (near Madison Reservoir) 

 upstream tc West Yellowstone, Several trails and county roads branch 

 off this highway to the river. A county road closely parallels the 

 north and east shores of Madison Reservoir. Hebgen Reservoir Is nearly 

 encircled by trails. About the only sections not readily accessible 

 by car are Bear Trap Canyon and the lower 15 miles of the river. As a 

 general rule, the latter area can be reached only by going through 

 private property, much of which is posted against trespass. Eating 

 and sleeping facilities are available in most of the towns, and several 



