of about 100 inches on top of Big Mountain. This precipitation results in an estimated average runoff of 

 36 inches per year at the highest elevations and approximately 9 inches at the mouth of Big Creek. 



Streamflow begins to increase in April as the snowpack melts with warming spring temperatures. Peak 

 streamflow usually occurs in late May or June. Not all snowmelt or rainfall of the study area becomes 

 surface runoff, at least not immediately. Some may infiltrate the ground to become groundwater that 

 percolates downward in the soil and bedrock and resurfaces in wet areas, small ponds, and perennial 

 streams at various elevations below the point of infiltration. Slow release of groundwater provides the 

 stream baseflow starting in mid July to mid September. 



Table -2 displays the average monthly air temperatures and average monthly precipitation at Glacier 

 International Airport (Kalispell, Montana). This National Oceanic and Atmospheric Administration 

 weather station is 16 air miles southeast of the headwaters of Big Creek. 



Table - 2: The average monthly air temperatures and average monthly precipitation at Glacier 

 International Airport (Kalispell, Montana). 



As previously described, peak streamflow usually occurs in late May or early June from spring 

 snowmelt. Flood flows rarely overtop the channel banks of Big Creek and erode adjacent land areas. 

 High flows that erode the upper banks of the channel occur every three to five years. The last high flow 

 was in the spring of 1 998 from the snowmelt of an unusually deep snowpack. There was a stream flow 

 guage located at Lookout Bridge at Big Creek. Stream flow measurements were taken there from early 

 spring till late fall for several years. During that time 2424 flow levels were recorded. The maximum 

 recorded flow was 2,404 cubic feet/second and the minimum flow was 9 cubic feet/second, with the 

 mean flow being 187 cubic feet/ second. Figure - 3 shows a comparison of the water flow in cubic 

 feet/second for the 1 992 water-year at the water quality monitoring site in lower Big Creek and on the 

 mainstem of North Fork of the Flathead River, at Glacier Rim 



