Creedmcin Coulee National Wildlife Refuge 



Climatic setting. The net annual precipitation balance for the 

 Creedman Coulee site (from the MAPS database) is -25 inches, mid- 

 range in comparison to sites of it's classification. Mean monthly 

 precipitation for the Fort Assiniboine climatic station shows a 

 pronounced June maximum. The 3-year moving average of annual total 

 precipitation shows an apparent periodicity with maxima on 4 to 6 

 year intervals. The moving average remained near or above the 

 long-term mean from 1974 through 1993; in 1993 (the year prior to 

 sampling) total precipitation exceeded the long-terra mean by about 

 7 inches. 



Geologic setting. Creedman Coulee is underlain by late Pleistocene 

 till of undescribed character. The till is inferred to be 

 calcareous, shaley and of low permeability. The valley floor of 

 Creedman Coulee is underlain by modern alluvium of unknown 

 character and possibly by glaciof luvial sediments. 



At the wetland site and throughout most of the Creedman Coulee 

 basin, glacial sediments are underlain by the late Cretaceous 

 Bearpaw Shale; in some of the upper basin the Judith River 

 Formation underlies the surficial deposits. 



Hydrologic type. WET17 is located on Creedman Reservoir, an 

 artificial impoundment of Creedman Coulee. The reservoir has an 

 outflow structure and is inferred to discharge water fairly 

 regularly due to the relatively dilute water chemistry shown. 



Basin characteristics. No information on the maximum depth or 

 volume of Creedman Reservoir is available. The catchment area to 

 wetland area ratio ranks mid-range for sample sites in this 

 classification. Numerous small stock-watering reservoirs scattered 

 throughout the catchment probably influence the timing and quantity 

 of runoff received by Creedman Reservoir. 



Water chemistry. At the time of sampling, Creedman Reservoir's was 

 relatively dilute and moderately alkaline, with similar equivalent 

 proportions of divalent (calcium and magnesium) and monovalent 

 (sodium and potassium) cations and bicarbonate-dominated anion 

 chemistry. Mineral equilibria indicate moderate oversaturation 

 with carbonate phases. Nitrogen concentrations (nitrate plus 

 ammonium) were low in comparison to the range shown by this site 

 classification; phosphorous concentrations (total and 

 orthophosphorous) were mid-range for sites of this classification, 

 as was the total organic carbon concentration. 



The boron concentration reported for WET17 was among the highest 

 in the data set, and the highest for any site with surface water 

 outflow. The arsenic concentration ranked near the middle of the 

 range for this class, and the chromium concentration was 

 comparatively high. The iron concentration ranked comparatively 

 low, and the other trace elements were below detection limits. 



