LaFoe Lake 



Climatic setting. The net annual precipitation balance for LaFoe 

 Lake (from the MAPS database) is approximately 8 inches. This 

 makes LaFoe Lake the wettest of the lowland sites among the sample 

 set. Mean monthly precipitation for the Libby Ranger Station 

 climatic station (at a lower elevation than the WET33 site) shows 

 a bimodal distribution, with a broad primary winter maximum and a 

 secondary June peak. Annual totals for the Libby station show a 

 3-year running average since 1950 generally meeting or exceeding 

 the average for the period of record, with the exception of the 

 1977 to 1982 period. Annual precipitation in 1993 (the year prior 

 to sampling) met the long-term average for the station. 



Geologic setting. LaFoe Lake and the contributing drainage basin 

 are underlain by the calcareous Wallace Formation of the 

 Proterozoic Belt series. Alpine glaciers occupied nearby headwater 

 areas, but their down-valley extent is uncertain. Glacial and 

 other surficial sediments overlying bedrock are undescribed, but 

 inferred to be relatively thin. LaFoe Lake lies over the trace of 

 the Quartz Creek Fault, a north-trending normal fault downdropped 

 to the west. 



Hydrologic type. LaFoe Lake occupies a small depression of 

 uncertain origin, fed by intermittent(?) streamflow and drained by 

 a perennial ( ? ) stream . 



Basin characteristics. The LaFoe Lake drainage basin features high 

 local relief and a comparatively high catchment to wetland area 

 ratio relative to other western sample sites. The lake itself lies 

 near a low drainage divide which may be controlled in some fashion 

 by the Quartz Creek Fault, the trace of which passes through this 

 gap. 



Water chemistry. The water chemistry of LaFoe Lake is dilute, 

 near-neutral and calcium-bicarbonate in composition. Mineral 

 eguilibria indicate undersaturation with respect to carbonate 

 phases. The ammonium and phosphorous (total and orthophosphorous ) 

 concentrations rank toward the upper end of the ranges shown by 

 Rocky Mountain sites; The total organic carbon concentration ranks 

 mid-range among Rocky Mountain sites. 



Iron and aluminum concentrations rank near the high end of the 

 range shown by Rocky Mountain sites; the reported copper 

 concentration ranked mid-range, and most other trace element 

 concentrations were below detection limits. 



Chemical history. One previous (partial) chemical analysis is known 

 from LaFoe Lake. This sample, collected in June of 1987, had a 

 specific conductance of only 62 microsiemens/cm, about one-third 

 the value recorded at the time of the DHES sampling. This may 

 provide some idea of the kind of seasonal variation in salinity 

 expected at this site from early to late summer. No analyses of 



