Red River of the North Basin
National Water-Quality Assessment Program
Strobel, M.L., and Gerla, P.J., 1993, Hydrologic and Anthropogenic
Influences on the Occurrence of Saline Wetlands in the Red River of the
North Valley, Northeastern North Dakota: Prairie Ecosystems: Abstracts,
Wetlands Ecology, Management and Restoration, Wetland Symposium,
August 9-13, 1993, Jamestown, N.D., p. 44
Abstract
Large freshwater wetlands occupied many parts of the Red River of the North
valley prior to 1940. Most of these wetlands have been drained and placed
into agricultural production. However, many smaller wetlands still occur west
of the Red River of the North. In contrast to most wetlands in the Upper
Midwest, soils and water in these small wetlands have large sodium and
chloride concentrations that limit their use for agricultural production. The
purpose of this paper is to describe hydrogeologic conditions that are
responsible for forming these saline wetlands in the Red River of the North
valley.
The locations of saline wetlands generally correspond to the subcrop area of
the Lower Cretaceous and Paleozoic bedrock beneath variably thick glacial and
lacustrine sediments. Ground-water discharge from the bedrock aquifers occurs
as part of a regional flow system that extends westward from the Red River of
the North valley to the Rocky Mountains. Water in the wetlands originates
from precipitation and from saline ground-water discharged from deep bedrock
aquifers and shallow glacial aquifers.
Three hydrogeologic processes, which are related to texture of sediments,
topographic depressions, and flowing wells, could be responsible for the
formation of the saline wetlands. In areas where the most extensive saline
wetlands occur (near Kelly's Slough, Lake Ardoch, and Salt Lake), the wetlands
presumably overlie coarse-textured glacial and lacustrine sediments that allow
for significant areas of increased vertical flow. In particular, topography
of Kelly's Slough may indicate significant erosion of fine-grained lacustrine
sediments by ground-water discharge early in the history of the wetland.
In other areas, wetlands could have developed in naturally occurring
depressions by direct precipitation, surface inflow, and discharge of
ground-water from shallow aquifers. This generally occurs where the fine
texture of glacial and lacustrine sediments limits the volume of discharge
from the bedrock aquifers to the surface. The only discharge from these
topographic depressions is evapotranspiration. Evapotranspiration is greater
than precipitation and results in a seasonal deficit. This deficit, along
with the slow discharge of deep, saline ground-water to the depressions, has
led to large concentrations of dissolved solids. Seasonal fluctuation of
dissolved solids in water in the wetlands may be as much as 20,000mg/L.
Several small wetlands may have resulted from flowing wells. Numerous flowing
wells were completed in bedrock aquifers during the first half of this century
in eastern Grand Forks and Walsh counties. The distribution of these wetlands
is restricted to areas where the potentiometric surface of the bedrock
aquifers is above the land surface.
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U.S. Department of the Interior |
U.S. Geological Survey
