In order to adequately and uniformly assess the potential effects of water 

 withdrawals on the many aspects of the present study, projections of specific 

 levels of future withdrawals were necessary. The methodology by which these 

 projections were done is explained in Report No. 1 in this series, in which 

 also the three projected levels of development, low, intermediate, and high, are 

 explained in more detail. Summarized below, these three future levels of 

 development were formulated for energy, irrigation, and municipal water use 

 for each of the nine subbasins identified in figure A-1. 



ENERGY WATER USE 



In 1975, over 22 million tons of coal (19 million metric tons) were mined 

 in the state, up from 14 million (13 million metric) in 1974, 11 million (10 

 million metric) in 1973, and 1 million (.9 million metric) in 1969. By 1980, 

 even if no new contracts are entered, Montana's annual coal production will 

 exceed 40 million tons (35 million metric tons). Coal reserves, estimated at 

 over 50 billion economically strippable tons (45 billion metric tons) (Montana 

 Energy Advisory Council 1976), pose no serious constraint to the levels of 

 development projected, which range from 186.7 (170.3 metric) to 462.8 (419.9 

 metric) million tons stripped in the basin annually by the year 2000. 



Table A-1 shows the amount of coal mined, total conversion production, 

 and associated consumption for six coal development activities expected to take 

 place in the basin by the year 2000. Table A-2 shows water consumption by sub- 

 basin for those six activities. Only the Bighorn, Mid-Yellowstone, Tongue, Powder 

 and Lower Yellowstone subbasins would experience coal mining or associated 

 development in these projections. 



IRRIGATION WATER USE 



Lands in the basin which are now either fully or partially irrigated total 

 about 263,000 ha (650,000 acres) and consume annually about 1,850 hm^ (1,5 rmaf) 

 of water. Irrigated agriculture in the Yellowstone Basin has been increasing 

 since 1971 (Montana DNRC 1975). Much of this expansion can be attributed to 

 the introduction of sprinkler irrigation systems. 



After evaluating Yellowstone Basin land suitability for irrigation, con- 

 sidering soils, economic viability, and water availability (only the Yellowstone 

 River and its four main tributaries, Clarks Fork, Bighorn, Tongue, and Powder, 

 were considered as water sources), this study concluded that 95,900 ha (237,000 

 acres) in the basin are financially feasible for irrigation. These acres are 

 identified by county and subbasin in table A-3; table A-4 presents projections 

 of water depletion. 



Three levels of development were projected. The lov/est includes one-third, 

 the intermediate, two-thirds, and the highest, all of the feasibly irriaable 

 acreage. 



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