While these technical studies were underway, the Com- 

 mission focused its efforts on negotiations with the Assini- 

 boine and Sioux Tribes of the Fort Peck Reservation. In May 

 of 1985 the Fort Peck-Montana Compact was signed into 

 law and the Commission again turned its attention to the 

 Northern Chcvcnne. 



When the Compaa Commission and the Northern 

 Cheyenne met again in Oaober of 1985, the attomeys for 

 the Tribe agreed to draft a scniement proposal to submit to 

 the Compact Commission. The Tribe's proposal for quanti- 

 fication of its reserved water rights was received in October 

 ofl988. Meanwhile, in 198T', thelcgisiature mandated that 

 the Commission focus its work on negotiations in the Milk 

 River Basin, to the maximum extent practicable. In 1989, 

 the Commission obained increased fiinding from the legis- 

 lature and authorization for additional personnel on the staff 

 of the Commission, so that the Commission could respond 

 to the Northern Cheyenne proposal without neglecting the 

 mandate to work on the Milk River Basin. 



In March 1 989, the RWRCC andTribe agreed to try to 

 havea water rights compact ready for radfication by the 1 99 1 

 Montana Legislature. Ratification of water rights compacts 

 is required by sute statute. Section 85-2-702, Montana 

 Code Annotated. In the spring and summer of 1989, the 

 RWRCC resumed legal and historical analyses of the tribal 

 claims. Initial responses to the Northem Cheyenne proposal 

 on key issues of priority date and reservation purpose were 

 sent to the Tribe in October. 



As new technical staff members were hired and trained, 

 the work of the former staff was reviewed and updated, 

 additional background information was obtained, and plans 

 for a comprehensive technical review were developed. The 

 first four months of 1 990 were devoted to intensive analyses 

 of the land and water resources of the Northem Cheyenne 

 Reservation. On May 1, 1990, the Reserved Water Rights 

 Compact Commission responded to the Tribe's proposal 

 with a counterproposal developed by the negotiating team 

 with knowledge of the results of the technical work discussed 

 in this report. 



B. Summary of Technical Analyses 



To estimate the amount of water necessary to fulfill the 

 present and potential future agricultural needs of the North- 

 em Cheyenne Reservation, the technical staff employed a 



four-part prtxredurc: geographic dau computerization, clas- 

 sification of soils and arable land, assessment of water 

 availability, and engineering design of economically feasible 

 irrigation systems. 



The staff of the Compaa Commission uses a Geo- 

 grapfuc Information System (CIS) for spatial analyses. Geo- 

 graphic Information Systems are used to store, retrieve, 

 manipulate and analyze resource data (ie. soils, hydrologic, 

 engineering, agricultural). A GIS enables the user to overlay 

 separate types of resource data for a particular area. The user 

 can then identify relationships between natural features and 

 man-made developments, compare past, existing and poten- 

 tial conditions and model present conditions that could 

 affea future management. 



The initial evaluation began with a survey of available 

 information from previous staff work, library sources and 

 other agencies. Information on soils, land use and land own- 

 ership, along with other types of data, were entered into the 

 GIS as base information for maps, overlays and statistics to 

 aid decision-making. 



The staff soils scientist evaluated soil types on the reser- 

 vadon and classified them as to whether they were physically 

 capable of producing crops under sustained irrigation. The 

 agricultural engineer then used this soil information to deter- 

 mine where irrigation would be feasible, based on engineer- 

 ing and economic criteria. 



The staff hydrologist evaluated stream flow and ground- 

 water data to determine the amount of water actually 

 available in the relevant basins. Scenarios were developed tor 

 the different levels of irrigation that would result from dif- 

 ferent water use efficiencies. 



On the Tongue River, the staff concluded that 4,027 

 acres could be irrigated on the Reservation, with a cost benefit 

 ratio of 1 : 1 or better. RWRCC's negotiating team accepted 

 this rado as a criterion of an economically feasible irrigation 

 system. The amount of water necessary to irrigate these 

 projects was estimated to be 10,497 acre feet per year. Litde 

 of this acreage is being irrigated at the present. 



On the Rosebud, a complete FIL analysis was not per- 

 formed because suflicient water was not available. A prelimi- 

 nary engineering review determined that any currently 

 nonirrigated land could only be served by partial service 

 irrigadon, which most likely would be uneconomical. 



