North Widgeon Slough WPA 



Clinatic setting. The net annual precipitation balance for North 

 Widgeon Slough (from the MAPS database) is -20 inches, placing this 

 site near the less intensely evaporative end of the range shown by 

 Great Plains sites. (Research on Brush Lake indicates that this 

 value considerably underestimates actual evaporative losses in this 

 area, and emphasizes the need to view these values only as 

 comparative indicators of evaporative intensity.) Mean monthly 

 precipitation for the nearby Westby station shows a broad 

 summertime peak with a June maximum. Annual totals for the Westby 

 station, though incomplete for recent years, show the persistent 

 regional deficit of the 1980s, and totals exceeding the long-term 

 average in the early 1990s. Total precipitation in 1992, the year 

 prior to sampling, was about an inch below the long-term average. 



Geologic setting. The North Widgeon Slough area is underlain by 

 a pitted surface of late Wisconsin-aged calcareous glacial till; 

 other glacial deposits of local distribution may occur within the 

 lake catchment. North Widgeon Slough and it's catchment are 

 outside of the area of distribution of the Clear Lake aguifer and 

 other permeable gravel aguifer systems. Surficial glacial deposits 

 are underlain by sandstone and shale of the early Tertiary 

 (Paleocene) Fort Union Formation. 



Hydrologic type. North Widgeon Slough is an ice-block depression 

 (kettle) with ephemeral channelized surface-water inflow, and 

 lacking surface water outflow under present hydrologic conditions. 

 The relationship of North Widgeon Slough to local ground-water 

 systems is undescribed; both local ground-water inflow and outflow 

 may be inferred for different conditions. 



Basin characteristics. Unlike the other smaller sampling sites in 

 the Medicine Lake area (Brush Lake, Comertown Preserve, Mallard 

 Pond, North Goose Lake), North Widgeon Slough has a catchment 

 extending well beyond the wetland basin itself, and a catchment to 

 wetland area ratio ranking mid-range among sampling sites of the 

 glaciated plains. The depth of the slough is unmeasured but 

 inferred to be no more than a few feet. North Widgeon Slough may 

 drain to the northwest during periods of higher precipitation. 



Water chemistry. At the time of sampling, North Widgeon Slough 

 contained moderately alkaline "mesosaline" water of sodium-sulfate 

 composition. Mineral eguilibria indicate substantial 

 oversaturation with carbonate phases. The ammonium concentration 

 ranks toward the upper end of the range shown for sites in this 

 class; phosphorous (total and orthophosphate) and total organic 

 carbon concentrations rank low to mid-range in comparison to sites 

 in the same classification. 



Arsenic and boron concentrations ranked toward the upper end of the 

 ranges shown by sampling sites in this class. Lead and nickel were 

 reported at their respective detection limits. In the case of 



