Tew Waterfowl Production Area 



Climatic setting. The net annual precipitation balance for the 

 Tew WPA (from the MAPS database) is -27 inches, ranking Tew toward 

 the more intensely evaporative end of the range shown by 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. WET67 is located on a small structurally 

 controlled(?) basin underlain by the Lebo Shale Member of the early 

 Tertiary Fort Union Formation. Descriptions of the surficial 

 sediments overlying the Fort Union Formation are not available, but 

 they are inferred to consist of relatively thin and locally derived 

 lacustrine or paludal deposits. 



Hydrologic type. The WET67 site is a small area of internal 

 drainage lacking discrete surface water inflow or outflow under 

 present hydrologic conditions. Inflow is inferred to be by local 

 runoff and direct precipitation. 



Basin characteristics. The small local catchment provides this 

 site with a low catchment to wetland area ratio. At low stages 

 separate water bodies apparently exist within the mapped 

 catchment; during wet conditions the sampled wetland may merge with 

 an adjacent water body outside of the local catchment. Some 

 ground-water outflow may occur, but the basin sediments are 

 probably of low permeability and unlikely to allow very rapid 

 ground-water recharge. The wetland basin has apparently been 

 modified by the construction of the county road adjacent to the 

 WET67 site; this modification may alter the geometry of the water 

 body during high-stage conditions. The water depth of the wetland 

 is unknown but inferred to be shallow. 



Water chemistry. At the time of sampling, the Tew wetland 

 contained moderately alkaline, "oligosaline" water lacking a 

 dominant anion or cation. Mineral equilibria indicate 

 oversaturation with carbonate phases. The equivalent concentration 

 of chloride is high compared to most sample sites. The nitrate 

 concentration was below reporting limits and the ammonium 

 concentration was low in comparison to other sites of the plains. 

 Phosphorous concentrations, however, were very high, exceeded only 

 at a few hypersaline or seasonal, closed-basin sample sites. The 

 total organic carbon concentration was among the lowest in the 

 sample set. 



Most of the trace elements analyzed occurred in concentrations 

 below reporting limits. The iron concentration ranked near the top 

 of the range shown by plains sites, the arsenic concentration 

 ranked mid-range and the boron concentration was the lowest 



