Long-term flow records are available for, three USGS gaging 

 sites on the Madison River below Hebgen Dam.*" The mean flow 

 for a 39-year period of record at the gage below Ennis Dam 

 (near McAllister) was 1,762 cfs. Flows ranged from 210 to 

 9,550 cfs. The mean flow for a 13-year period of record at 

 the gage upstream of Ennis (near Cameron) was 1,4 32 cfs. 

 Flows ranged from 2 75 to 8,8 30 cfs. The mean flow for a 6 7- 

 year period of record at the gage below Hebgen Dam (near 

 Grayling) was 999 cfs. Flows ranged from 5 to 10,200 cfs. 



Water quality throughout the Madison River can generally 

 be described as good. The water is moderately hard; the pH 

 ranges from 8.3-8.5; and dissolved oxygen averages 10 mg/1. 

 Other selected chemical properties are given in Table 1. 



Table 1. Selected chemical properties of the Madison River 

 near Three Forks, Montana in summer and fall, 1977 

 and spring, 1978 (data from Bahls et al., 1979). 



Summer Fal l Spring Mean 



Specific Conductance 



(umhos @ 25 C) 321 _ - _ 



Total Alkalinity (mg/1 CaC03) 114 _ - _ 



Phosphate (PO4 as P in mg/lj .009 .014 .033 .019 



Total Phosphorous (P in mg/1) .025 .020 .053 .033 

 Nitrate plus Nitrite 



(NO3+NO2 as N in mg/1) <'.01 .02 .04 



Ammonia (NH3 as N in mg/1) <.01 <.01 .02 



Kjfeldahl Nitrogen (N in mg/1) .33 .19 .21 .24 



Reach #1 encompasses a 40-mile section between the 

 river's mouth (river mile 0) and Ennis Reservoir (river mile 

 40) . The upper 14 miles of reach #1 (river miles 26 to 40) 

 lie within the narrow Bear Trap canyon. The river within the 

 canyon is characterized by turbulent riffle-run areas inter- 

 spersed with pools and large boulders. Gradient averages 

 21 ft per mile. 



Near the mouth of Cherry Creek at river mile 26, the 

 river enters the lower Madison valley. The channel becomes 

 braided forming many islands and side channels. Boulder, 

 cobble and gravel comprise the bottom si±)Strate. Weed beds 

 are also common. The channel generally exceeds 300 ft in 

 width. Depths rarely exceed 4 ft. Well defined riffle-pool 

 areas are absent. The immediate floodplain is vegetated with 

 willow, alder and numerous cottonwoods . Gradient averages 

 16 ft per mile. 



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