Lakeside Wetland 



Climatic setting. The net annual precipitation balance for the 

 Lake Bowdoin area (including the Lakeside wetland) is -28 inches, 

 placing the Bowdoin sites at the more evaporative end of the range 

 shown by sites in this classification. Monthly mean precipitation 

 for the Malta 7NE climatic station shows a broad summer peak with 

 a maximum in May; the Malta climatic station, with a longer period 

 of record but farther from Lake Bowdoin, shows a pronounced June 

 maximum. Annual totals for the Malta 7NE station, shows the years 

 1988 to 1992 below the average for the period of record. The total 

 for 1993 (the year prior to sampling) exceeded the average for the 

 period of record by about 2.5 inches. 



Geologic setting. The natural catchment of the Lake Bowdoin area 

 is underlain primarily by the Late Cretaceous Claggett Shale, with 

 the overlying Judith River Formation exposed in some higher- 

 elevation areas. The apex of the Bowdoin Dome lies a few miles to 

 the north; this structural dome is a significant hydrocarbon trap 

 and supports an active natural gas field. Surficial sediments 

 underlying the Lake Bowdoin basin are generally described as 

 "alluvium", mapped as a broad east-west band underlying the lake. 

 These deposits are apparently continuous with permeable gravels 

 underlying lower Beaver Creek to the east, which are believed to 

 be glacial in origin. 



Hydrologic type. The Lakeside wetland is a small internally 

 drained basin altered and augmented by dikes, ditches, inlet and 

 outlet control structures, and transportation and utility 

 corridors. Inflow is diverted directly from the Dodson South 

 Canal. Outflow is controlled by a headgate and ditch delivering 

 water to the Dry Lake Unit and to peripheral ponds nearby. 



Basin characteristics. The natural catchment of the Lakeside 

 Wetland is minimal in area, with almost all water in the system 

 imported from the Milk River Irrigation Project. Water management 

 objectives for the Lakeside Unit emphasize maintaining low 

 salinity, requiring that a proportionately high water flux through 

 the basin be maintained. The depth of the basin is not available 

 but is inferred to be only a few feet. 



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

 contained dilute (for the region), alkaline water of nonspecific 

 composition; divalent and monovalent cations contributed about 

 equally to the solute load, and C02 species and sulfate both 

 contributed significantly to the anion equivalence. The dilute 

 nature of the site reflects the import of Milk River Project water 

 to the site in accordance with the refuge management objectives. 

 Equilibrium calculations indicate oversaturation with carbonate 

 minerals. Ammonium and nitrate concentrations were both below 

 detection limits (unusual for Great Plains sites) and 

 orthophosphorous and total phosphorous concentrations were both 

 near the bottom of the ranges for sample sites outside of the Rocky 



