Blackfoot Meadows 



Climatic setting. The net annual precipitation balance for 

 Blackfoot Meadows (from the MAPS database) is -2 inches, placing 

 the site near the humid end of the range shown by the sample sites. 

 Mean monthly precipitation for the Basin climatic station (across 

 a major drainage divide from the site) shows a bimodal 

 distribution, with a primary June maximum and a secondary January 

 peak. The three-year running average of annual precipitation for 

 the Boulder station (also at some distance from the site) shows 

 values below the long-term mean for much of the 1980s and near or 

 above the long-term average for 1990-93, with precipitation in 1993 

 (the year of sampling) almost 6 inches above average. [Water 

 supply to Blackfoot Meadows is probably supported mainly by winter 

 snowpack, however, which is not reflected in data from these low- 

 elevation stations.] 



Geologic setting. Surficial deposits in the upper Little Blackfoot 

 basin have been interpreted as glacial in origin, derived from 

 local igneous lithologies. Blackfoot Meadows itself is underlain 

 by alluvial and paludal deposits of unknown depth. Bedrock in the 

 contributing drainage basin is composed of felsic to intermediate 

 volcanic and intrusive lithologies of late Cretaceous and early 

 Tertiary age. Outcrops in the immediate area of Blackfoot Meadows 

 are Tertiary rhyolitic tuffs. 



Hydrologic type. Blackfoot Meadows is an area of low hydraulic and 

 topographic gradient along the channel of the Little Blackfoot 

 River. Inflow is from the Little Blackfoot and tributary streams, 

 and outflow is via the Little Blackfoot River. The valley profile 

 and cross-section suggest alluvial deposition in an over-deepened 

 or geologically impounded valley segment. Beaver activity now 

 influences throughflow and stream gradients. 



Basin characteristics. The catchment contributing to this wetland 

 has high relief and an intermediate catchment to wetland area ratio 

 for Rocky Mountain sites. The distribution of different hydrologic 

 regimes within the wetland is probably relatively transient due to 

 the activities of beavers. 



Water chenistry. Water chemistry at this site is mildly acidic 

 and very dilute. Mineral equilibria indicate substantial 

 undersaturation with respect to the phases evaluated, but censored 

 data and poor ion balance limit the usefulness of these 

 calculations. Nitrate and ammonium concentrations were below 

 detection limits; the orthophosphorous concentration was mid-range 

 among sites of this class, and the total organic carbon 

 concentration was toward the lower end of the class range. 



Arsenic was reported at twice the detection limit (mid-range for 

 sites of this class), and iron was reported at a concentration mid- 

 range for the sample set. Most other trace element concentrations 

 were below detection limits. 



