Lebeau Creek South 



Climatic setting. The net annual precipitation balance (from the 

 MAPS database) is -5 inches, near the middle of the range of 

 evaporative intensity shown by Rocky Mountain sample sites. Mean 

 monthly precipitation for the Olney climatic station shows a 

 bimodal distribution, with a pronounced June peak and a broad 

 wintertime (November to January) peak. (Much of the catchment 

 contributing runoff to this site is 1000-2000 higher than the Olney 

 gauge, so precipitation records serve only as a general indication 

 of recent precipitation history.) Annual totals for the Olney 

 station are fragmentary; regionally, annual precipitation was above 

 average in 1993 (the year prior to sampling) and below average in 

 1994. 



Geologic setting. The WET44 site is along the margins of the 

 glacially scoured Stillwater Valley and is presumed to be underlain 

 by sediments of glacial origin. No local description of the 

 character of these sediments is available, however. Surficial 

 sediments in the contributing catchment are underlain by formations 

 of the Proterozoic-aged Belt series, including large areas of the 

 dominantly calcareous and dolomitic Helena Formation. Numerous 

 northwest-trending normal faults (structural elements of the Rocky 

 Mountain Trench) cross the general area. 



Hydrologic type. The WET44 site occurs along a mapped tributary 

 to Lebeau Creek and has surface water inlet and outlet channels 

 which are mapped as intermittent; discharge rates and duration are 

 not known for this stream. Forest road construction may contribute 

 to the wetland by artificially impounding the outlet stream. 



Basin characteristics. The Lebeau Creek site has a high catchment 

 to wetland area ratio in comparison to other Rocky Mountain sites. 

 In conjunction with the moist climate and steep slopes, this 

 characteristic implies a relatively rapid hydrologic flux through 

 the wetland. 



Water chemistry. Water in the Lebeau wetland is dilute, mildly 

 alkaline and calcium-bicarbonate in character. Mineral equilibria 

 indicate near-equilibrium with calcite and aragonite and only 

 slight oversaturation with dolomite. Ammonium and nitrate 

 concentrations were below reporting limits; phosphorous (total and 

 orthophosphorous ) and total organic carbon concentrations were 

 toward the lower end of the ranges shown by Rocky Mountain sites. 



The recoverable iron concentration was near the lower end of the 

 range shown for sites in this class, and copper was reported at the 

 detection limit. Other trace elements were below reporting limits. 



Chemical history. No other chemical data are known from this site. 



Sediments. The extractable selenium concentration reported for 

 this site is the highest for any of the Rocky Mountain sample 



