^vit^uxdccUimi 



PURPOSE 



In the fall of 1974 a two-year study was initiated on the Tongue River to 

 assess fish populations present for these purposes: 



1) To determine species composition and distribution, 



2) To establish and evaluate diversity indices for various habitat 

 zones or sections, 



3) To evaluate the potential impacts of water withdrawals. 



STUDY AREA 



The Tongue River's name originated from the Indian word "La-zee-ka," 

 meaning tongue, for a tree-covered limestone slab outlined by barren rock which 

 resembled a buffalo tongue. The headwaters of the Tongue River rise on the 

 eastern slope of the Bighorn Mountains of Wyoming and flow generally northeast 

 through Montana to join the Yellowstone River at Miles City. The length of 

 the Tongue River from the Montana-Wyoming border to its confluence with the 

 Yellowstone River is 326.5 km (202.9 mi). 



The Tongue River's flow in Montana is controlled by the Tongue River Dam. 

 The dam, completed in 1940 for storage of irrigation water, impounds 84.9 hm^ 

 (59,000 af) with a surface area of 1,416 ha (3,500 acres). 



The Tongue River drains approximately 13,932 km^ (5,379 mi2), 70 percent 

 of which is in Montana, with an average annual discharge of 11.9 m^/sec 

 (420 cfs). The maximum recorded discharge was 377 m3/sec (13,300 cfs) on 

 June 15, 1962. The two typical stream bed formations found are: (1) in strong 

 current, gravel cobblestones and outcropping of bedrock, and (2) in slack or 

 slow current, silt and sand. 



The average annual temperature for the basin varies from 4.4 to 11.1°C 

 (40-52OF). Average annual precipitation varies from 22.9 to 40.6 cm (9 to 16 in). 



The basin of the Tongue River is underlain by the Fort Union Formation 

 of the early Tertiary (Eocene) Age which has a total thickness of about 610 m 

 (2,000 ft). Ninety percent of the soils were formed on sandstones and shales 

 laid down in the Cretaceous or Tertiary periods. 



The river is an important source of water for irrigation, domestic use 

 by man and livestock, recreational use, and industrial use. With the 

 increase in coal development in the Tongue River drainage, the river takes on 



