The FY 1986-87 data base is relatively complete and 

 represents 14 to 17 samplings at most of the stations in the 

 monitoring network. However, in FY 1985 nutrient and 

 suspended sediment were monitored infrequently in the Clark 

 Fork above Rock Creek (near Clinton) . As a result, discus- 

 sions of nutrients and suspended sediments rely mostly on FY 

 1986-87 data. 



The USGS has been sampling periodically at six sites in 

 the upper Clark Fork Basin since March 1985 (Figure 3-15) . 

 Two of the sites are on the Clark Fork mainstem (at Deer 

 Lodge and at Turah Bridge, near Bonner) and four sites are 

 near the mouths of major tributaries between Deer Lodge and 

 Milltown Reservoir (Little Blackfoot River, Flint Creek, Rock 

 Creek, and Blackfoot River) . Field measurements include 

 stream discharge, specific conductance, pH, temperature, 

 bicarbonate and carbonate, and alkalinity. Laboratory 

 analyses include hardness; selected dissolved, total, or 

 total recoverable trace elements; and suspended sediment. 



The primary objective of the USGS sampling program is to 

 characterize the geographic and hydrologic variation in 

 trace element and suspended sediment concentrations. 

 Geographically, sampling locations were selected to describe 

 water quality conditions at the upper and lower end of the 

 upper Clark Fork segment and in the major tributary basins 

 entering this reach. Hydrologically, sampling was designed 

 to cover a wide range of flow conditions to describe the 

 variation in water quality with streamflow. However, because 

 of limited sampling frequency and below-normal streamflows, 

 efforts are made to sample during runoff events to document 

 conditions when suspended constituent concentrations are 

 likely to be at a maximum. 



In addition to periodic water quality sampling, the two 

 Clark Fork stations at Deer Lodge and Turah Bridge are 

 operated as daily sediment sampling stations to describe the 

 suspended sediment transport characteristics in the upper 

 basin. Funding for the periodic water quality sampling and 

 daily sediment sampling stations has been provided by both 

 state and federal sources since 1985. The EPA is funding the 

 sampling during 1988. 



A sampling program was also conducted by the USGS from 

 July 1986 to April 1987 to measure suspended sediment loads 

 entering and leaving Milltown Reservoir during the Phase I 

 emergency reconstruction of the Milltown Dam. As part of 

 this effort, three daily sediment stations were operated, 

 two upstream from the reservoir (Clark Fork at Turah Bridge 

 and Blackfoot River near Bonner) and one downstream from the 

 reservoir (Clark Fork above Missoula) (Figure 3-15) . Daily 

 sediment sampling at these stations was resumed when Phase II 



3-62 



