Spidel Waterfowl Production Area 



Climatic setting. The net annual precipitation balance for the 

 Spidel WPA (from the MAPS database) is -29 inches, ranking this as 

 one of the most intensely evaporative sites in the data set. Mean 

 monthly precipitation for the Broadview climatic station shows a 

 maximum in May; annual totals for the Broadview station are 

 incomplete but show generally below-normal values during the 1980s. 

 Annual totals after 1990 were not recovered for this station. 

 Regionally, precipitation totals for 1991 through 1993 were above 

 average for many stations. 



Geologic setting. The Spidel basin is a depression along the 

 western limb of the Bull Mountains structural basin. The Spidel 

 basin itself appears to be structurally controlled; WET63 is 

 underlain by the Lance Formation of latest Cretaceous age; western 

 portions of the Spidel catchment are underlain by the Bearpaw Shale 

 and Judith River Formations of late Cretaceous age, while the 

 eastern portion of the catchment is underlain by the Fort Union 

 Formation of early Tertiary age. The central portion of the Spidel 

 basin has accumulated an unknown thickness of lacustrine sediments. 



Hydrologic type. The Spidel wetland occupies a basin lacking 

 surface water outflow, and receiving surface water inflow from a 

 number of intermittent drainages. Local ground-water inflow may 

 also occur but probably is not volumetrically important. The 

 surface extent and shoreline position of the Spidel wetland is 

 inferred to be highly variable. 



Basin characteristics. The Spidel basin has a large catchment and, 

 based on the mapped extent of the wetland, a catchment to wetland 

 area ratio intermediate with respect to other sample sites of the 

 unglaciated great plains. A number of small impoundments within 

 the catchment may have altered the quantity and timing of runoff 

 received by the Spidel basin. The low gradient basin implies large 

 variations in surface area; water depths are unknown but inferred 

 to be no more than a few feet. 



Water chemistry. At the time of sampling, the Spidel WPA contained 

 transition "oligosaline/mesosaline" sodium sulfate water of 

 moderately high alkalinity. Mineral equilibria indicate 

 substantial oversaturation with carbonate phases. The ammonium 

 concentration was low in comparison both to unglaciated plains 

 sites and to other sites lacking surface water outflow. 

 Phosphorous concentrations ranked mid-range with respect to 

 regionally and hydrologically similar sites, and the total organic 

 carbon concentration was comparatively high. 



Arsenic, boron and iron concentrations ranked mid-range in 

 comparison to other sites in this class. Most other trace element 

 concentrations were below reporting limits. 



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



