Foothills and Valleys Ecoregion Key
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1 
1st order, origin from Valley Foor groundwater output
  
1 
1st-2nd order or <30 miles long
  
1 
3rd-4th order or >30 and <60 miles long
  
1 
4th-5th order, >60 miles long and a direct tributary to the Yellowstone or Missouri River
  
 
2 
Cool-cold water tributaries that originate in the foothills and flow out to prairie rivers that are too warm to support coldwater fisheries
  
2 
Coldwater tributaries that flow to foothills and valley intermountain transitional rivers that maintain coldwater fisheries
  

Ecoregions are based on Omernik’s Level III Ecoregion delineations (see Woods, A.J. et al. 2002. Ecoregions of Montana. 2nd edition poster). The Foothills and Valleys Ecoregion (old #16, Omernik 1999) include the Middle Rockies Ecoregion (#17), Northwestern Glaciated Plains (#42) and the Northwestern Great Plains Ecoregion (#43) Level IV foothills areas defined as below 1600 m in elevation and non-forested.
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