« Sweunp Gulch 



Climatic setting. The net annual precipitation balance for Swamp 

 Gulch (from the MAPS database) is -4 inches, mid-range among Rocky 

 Mountain sites. Mean monthly precipitation for the Lincoln Ranger 

 Station climatic station shows a late spring peak, with relatively 

 even distribution the remainder of the year. (Water supply in the 

 headwater streams contributing to the Swamp Gulch wetland probably 

 are much more heavily influenced by winter snowpack than is the 

 Lincoln climatic station.) Annual total precipitation for the 

 Lincoln station was generally below average during the mid-1980s 

 and near or above the long-term average in the late 1980s and early 

 1990s. Total precipitation in 1993 (the year of the DHES sampling) 

 exceeded the long-term average by about 5 inches. 



Geologic setting. The Swamp Gulch wetland and upstream catchment 

 areas are underlain mainly by the Spokane and Empire formations of 

 the Proterozoic-aged Belt series; late-Proterozoic mafic intrusive 

 rocks (diorite) also occur in the lower Swamp Gulch drainage. 

 Early Tertiary-aged monzonite porphyry and intrudes the 

 Proterozoic-aged rocks near the mouth of Swamp Gulch; 

 mineralization of the diorite near this intrusive contact was 

 developed by the abandoned Carbonate Mine. Drainage from the 

 Carbonate Mine enters lowermost Swamp Gulch and the WET64 wetland 

 area. The immediate wetland area is underlain by undescribed 

 alluvial (and glacial?) sediments and by up to 15 feet of peat and 

 other palustrine sediments. 



Hydrologic type. The Swamp Gulch wetland is a complex of low- 

 gradient riparian and ponded areas at the confluence of streams 

 forming the upper Blackfoot River. Surface water inflow occurs 

 from several streams. Surface-water outflow is to the Blackfoot 

 River. Ground-water movement through the wetland occurs through 

 peat and presumably through the underlying unconsolidated 

 sediments, probably discharging to the Blackfoot River downstream 

 of the WET64 site. 



Basin characteristics. The Swamp Gulch wetland has a substantial 

 catchment and a relatively high catchment to wetland area ratio. 

 Water sources in the immediate WET64 area include both Swamp Gulch 

 and the Upper Blackfoot River, which is formed a short distance 

 upstream by the confluence of Pass Creek and Anaconda Creek. 

 Blackfoot River water is carried past the WET64 site by beaver 

 ponds and a minor diversion channel. The distribution of ponds and 

 channels within the wetland area surrounding the WET64 site is 

 believed to have been stable throughout the twentieth century. 



The overall thickness of peat and other high-organic sediments is 

 on the order of 3 feet or less, with 3 to 12 feet of silty 

 "catotelra" beneath. Ground-water flow through the shallow organic 

 peat is relatively rapid and occurs along preferential flow paths. 



At least two of the several streams entering the wetland complex 



