Date of Award
Master of Science (MS)
Soil salinization associated with saline groundwater discharge results in decreased agricultural production in the central glacial Lake Agassiz plain of North Dakota. Saline discharge occurs in a belt of ephemeral wetlands in the lake plain. The physical and chemical hydrology of .the Lunby-stewart saline discharge wetland were investigated in order to provide information which could facilitate land management strategies applicable to this and other discharge wetlands.
Hydrologic data used to characterize the wetland were obtained from monitoring wells, staff gages, precipitation gages, borings, and earth electrical resistivity soundings. Temporal and spatial variations were observed in the water table, the vertical groundwater gradient, and hydrogeochemistry of this wetland.
The non-integrated wetland hosts two intermittent lakes fringed by saline soils of lacustrine origin. Low permeability sediments underlying the wetland have -7 hydraulic conductivities ranging from 1.0 x 10 m/s to 2.8 -9 x 10 m/s.
The temporal and spatial variability of the water table, vertical groundwater gradients, and salinity observed during the study .period, in conjunction with previous work on North Dakota wetlands, indicate that precipitation (rather than groundwater input or surface runoff) is the primary source of water supplying evapotranspiration losses. The dominance of chloride and presence of boron in ground and surface water at the wetland suggests input from a regional groundwater flow system. Salinity originates from Lower Cretaceous strata underlying the wetland at a depth of 30 to 43 metres.
According to geochemical models, calcite and gypsum are precipitated in the lacustrine glacial sediments as shallow groundwater undergoes evapotranspiratative losses, but dolomite is dissolved. Also, cation exchange of sodium for calcium and magnesium on smectitic clays occurs within the lacustrine sediments and till. Geochemical modeling results were consistent with x-ray diffraction data which indicate the presence of calcite and gypsum in a soil epipedon.
Soil types at the wetland are related to moisture and topography. Soil development and salinity are associated with geomorphic position within the wetland; low-lying soils generally have higher moisture content because of a shallow water table.
Goebel, Dean R., "Hydrogeologic Characterization of a discharge wetland in northeastern Grand Forks County, North Dakota" (1992). Theses and Dissertations. 108.