The nearby Sullivan Flats-Big Draw Aquifer is another 

 system with favorable characteristics for high-yield wells but 

 with apparent constraints on the scale of development. In this 

 case, the aquifer discharges virtually all of its modest annual 

 flux (1,700 AF/year) through a spring that appears to be heavily 

 appropriated for surface water use. 



The Mission Valley . This southern region of the Flathead 

 Valley has a complex deposit ional history that accounts for a 

 variety of known local aquifer systems. These are underlain by a 

 thick sequence of glacial and glaciofluvial debris that is a 

 widespread regional aquifer. 



Heterogeneous interstratif ied glacial deposits form the 

 regional ground water flow system. It is recharged along the 

 Mission Mountain front and at the north end of the Mission 

 Valley. Regional flow paths are toward the south and west, 

 discharging toward lower Mission Creek and the Flathead River 

 (Boettcher 1982) . Locally favorable aquifer characteristics 

 allow for yields of several hundred gpm from some municipal and 

 irrigation wells, and flowing wells are possible in several 

 areas. Annual recharge to the system probably far exceeds 

 withdrawals, suggesting that the area is physically capable of 

 supporting additional ground water development. Large additional 

 withdrawals would occur at the expense of reduced head in the 

 aquifer and reduced ground water discharge to the surface 

 environment. 



The shallow aquifers overlying the regional flow system 

 exhibit their own hydraulic characteristics and some degree of 

 functional separation from the regional aquifer. Some of these 

 are confined by surficial deposits of lakebed silts, resulting in 

 local artesian aquifers in which wells may flow. The shallow 

 aquifer of the Post Creek area is the most significant of these 

 and supports domestic, irrigation, and commercial water uses 

 often designed around flowing wells. Recharge to these flow 

 systems may (as in the case of the Post Creek Aquifer) be 

 abundant, but at the same time, existing uses are somewhat 

 vulnerable to well interferences because of relatively low 

 aquifer pressures. 



Jocko Valley . The Jocko Valley contains several hundred 

 feet of valley-fill sediment, at least some of which must 

 receive recharge from the Jocko River and irrigation systems in 

 the area. The hydrologic characteristics of the aquifer material 

 are not yet well described, and the aquifer's capability to 

 support large ground water withdrawals has not been demonstrated. 

 The existing wells are mainly small ones, used for domestic and 

 stock water. 



4-21 



