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THE RIVER 



The Yellowstone River Basin of southeastern Montana, northern Wyoming, 

 and western North Dakota encompasses approximately 180,000 km2 (71,000 square 

 miles), 92,200 (35,600) of them in Montana. Montana's portion of the basin 

 comprises 24 percent of the state's land; where the river crosses the 

 border into north Dakota, it carries about 8.8 million acre-feet of water per 

 year, 21 percent of the state's average annual outflow. The mainstem of the 

 Yellowstone rises in northwestern Wyoming and flows generally northeast to its 

 confluence with the Missouri River just east of the Moritana-iNorth Dakota 

 border; the river flows through Montana for about 550 of its 680 miles. The 

 major tributaries, the Boulder, Stillwater, Clarks Fork, Bighorn, Tongue, and 

 Powder rivers, all flow in a northerly direction as shown in figure 1. The 

 western part of the basin is part of the middle Rocky i-lountains physiographic 

 province; the eastern section is located in the northern Great Plains (Rocky 

 Mountain Association of Geologists 1972). 



THE CONFLICT 



Historically, agriculture has been Montana's most important industry. In 

 1975, over 40 percent of the primary employment in Montana was provided by 

 agriculture (Montana Department of Community Affairs 1976). In 1973, a good 

 year for agriculture, the earnings of labor and proprietors involved in 

 agricultural production in the fourteen counties that approximate the 

 Yellowstone Basin were over S141 million, as opposed to $13 million for 

 mining and S55 million for manufacturing. Cash receipts for Montana's 

 agricultural products more than doubled from 1968 to 1973. Since that year, 

 receipts have declined because of unfavorable market conditions: some 

 improvement may be in sight, however. In 1970, over 75 percent of the 

 Yellowstone Basin's land was in agricultural use (State Conservation Needs 

 Committee 1970). Irrigated agriculture is the basin's largest water use, 

 consuming annually about 1.5 million acre-feet (af) of water (Montana DMRC 

 1977). 



There is another industry in the Yellowstone Basin which, though it con- 

 sumes little water now, may require more in the future, and that is the coal 

 development industry. In 1971, the North Central Power Study (North Central 

 Power Study Coordinating Committee 197i) identified 42 potential power plant 

 sites in the five-state (Montana, North and South Dakota, Wyoming, and 

 Colorado) northern Great Plains region, 21 of them in Montana. These plants, 

 all to be fired by northern Great Plains coal, would generate 200,000 megawatts 

 (mw) of electricity, consume 3.4 million acre-feet per year (mmaf/y) of water, 

 and result in a large population increase. Administrative, economic, legal, 



