surface water-ground water interrelationships, and ground 

 water use. The authors noted degraded water quality in the 

 valley fill aquifer in the southern Deer Lodge Valley, but in 

 most areas water from the Quaternary valley fill was of 

 excellent quality. Water derived from Tertiary age sedimen- 

 tary rocks was excellent to good, with localized areas of 

 high total dissolved solids. They also indicated that water 

 use in the basin was low in comparison to the size of the 

 area and the amount of water available. With proper 

 management, the authors said, the aquifers could be developed 

 to ten times their use in 1975 without severely affecting the 

 water resource regimen in the area. 



McMurtrey et al. (1965) studied the geology and ground 

 water resources of the 180 square mile Missoula Basin, 

 including the Missoula Valley from Missoula to Huson and the 

 Ninemile Valley. They reported that the ground water was 

 generally of good quality and suitable for most domestic, 

 irrigation, and industrial uses. The Quaternary deposits 

 were the most important aquifer in the Missoula Basin, and 

 large yields could be expected from wells in the floodplain 

 of the Clark Fork and the low terrace bordering the flood- 

 plain. An estimated 30 million acre-feet of water is stored 

 in the Tertiary and Quaternary sediments, of which about 8 

 million acre-feet is available to wells. 



Geldon (1979) also studied the Missoula Basin. He iden- 

 tified three types of geologic units that furnish water to 

 wells, with the Quaternary-Tertiary alluvium supplying the 

 largest yield from unconfined sand and gravel layers. Geldon 

 also described the ground water in all units to be generally 

 of good quality. He predicted that continuing reliance on 

 ground water to supply an expanding population and agricul- 

 tural base would likely lower the water table in some areas, 

 causing some shallow wells to go dry. 



Juday and Keller (1978) conducted a study of the ground 

 water serving the Missoula Valley in 1978. Several hundred 

 wells were sampled in this study, and only three of these had 

 nitrate levels that approached or exceeded the federal 

 drinking water standard of 10 ppm. Col i form bacteria was a 

 problem in about 25 percent of the wells sampled. However, 

 the authors concluded that overall the ground water supply 

 serving the Missoula Valley was of high quality. Data 

 generated in their study are considered baseline water 

 quality data for the area (Missoula City-County Health 

 Department 1987) . 



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