RESULTS PART I: BLACKFOOT RIVER ENVIRONMENT 



5000 



4000 



3000 



2000 



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Blackfoot River Discharge: USGS Bonner gauging station #12340000 



During 2004 and 2005, 

 the Blackfoot River watershed Discharge (cfs) 



was subject to a 5"' and 6"^ year ^^^ 

 of consecutive drought. Mean 

 discharge was 1,241 cfs in 



2004 and 1,232 cfs in 2005, 

 compared to a 69-year mean of 

 1,563 cfs (Figure 6). 



Since the beginning of 

 drought in 2000, annual flows 

 in the Blackfoot River USGS 

 Bonner gauging station have 

 ranged from 61-96% of normal, 

 and averaged 80% of normal 

 over this six-year period. 

 During this time, minimum 

 monthly flows ranged from 47- 

 80% of normal. Critical late 

 summer low flows (July and 

 August) were 66-76% of normal with monthly flows as low as 53% in 2003 (Table 1). 

 The 2000 to 2005 annual hydrographs also show consistent lack of normal high (i.e. 

 flushing) flows, with the exception of 2002 (Figure 6). The Blackfoot River near Bonner 

 fell below "minimum instream flows" of -700 cfs on 207 days in 2004 and 1 74 days in 



2005 based on provisional USGS flow data. Minimal river flows were estimated at 300 

 cfs during mid-winter periods in both years (USGS 2006). 



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M J J 



S O N D 



Figure 6. Blackfoot River hydrographs at the USGS 

 Bonner gauging station, 2000-2005 provisional data. 



Table 1. Provisional mean monthly flow statistics for the Blackfoot River at the USGS 

 Bonner gauge, 2000-2005. 



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