equivaJcnt to a 50th percentile feasibility rating which is 

 discussed more completely in DNRC's methodology 

 document. 



2. Project Description 



First, the soils along theTongue River were classified for 

 arability (see Soils section). Then site specific irrigation 

 projects were designed on these lands to determine the 

 economic feasibility of individual projects. (See Appendix 

 R Projects were designed on lands adjacent to theTongue 

 River and on contiguous lands away from the river until the 

 B/C for a project went below 0.8. (See Appendix G) At this 

 point, no fiirther projects were designed. The following 

 tables summarize the results of the projects evaluated in the 

 FlLanalvsis of Northern Chevenne Indian Reservation. 



B. Rosebud Creek 



1 . Feasibly Irrigable Land Analysis 



The amount of feasibly irrigable land on the Rosebud 

 depends on the availability (amount and timing) of water, 

 the suitability of the soils adjacent to the water source, and 

 the economic variables used in the analysis, such as interest 

 rate, crops raised, crop prices, and crop yield. 



Rosebud Creek, like most eastern Montana creeks, has 

 a high flow in the spring and little flow in late summer, fall, 

 and winter. This means that fiiU service irrigation is limited 

 to the amount of flow in July and August (less than 2 cfs). 

 The standard approach in full service irrigation design is to 

 base the design acreage on the amount of water available 8 

 years out of i for the crop's peak use period. Therefore, the 

 Rosebud would be able to support less than 1 50 acres of new 

 irrigation. 



The customary way to irrigate on these creeks is to 

 spread water in the spring during high flow. This will gen- 

 erally provide enough water for one full cutting of hay. The 

 Rosebud is a relatively flat meandering stream; land next to 

 it is usually flooded by natural flows each year. Floodplain 

 land is also partially sub-irrigated along the Rosebud which 

 is an ideal way of using the Rosebud s water, from an eco- 

 nomic point of view. Any increase in consumptive use from 

 the current situarion would adversely impact downstream 

 users, both Indian and non-Indian. 



TOTAL FEASIBLE 



4,027.3 



10,497 



73.0 



28 



