Environmental Engineering Reference
In-Depth Information
Sand
Outwash
Sandy and silty clay
Moraine
Clay
Detroit
Sandy clay
0
10
20
30 km
Watershed boundary
FIGURE 1.4
Simplified map of near surface geology, Rouge River watershed. (From Murray et al., J. Environ. Qual , 33, 163,
2004. With permission, American Society of Agronomy.)
A thick lower clay unit of glacial origin (labeled as the lower clay unit) is located directly
beneath the surficial units. The lower clay unit ranges in thickness from 30 to 60 m and
exhibits a consistent hydraulic conductivity horizontally and vertically on the order of
1 × 10 −8 centimeters per second (cm/s), which essentially makes the unit an effective con-
fining layer (Rogers 1996). The thickness, horizontal distribution, and low and uniform
hydraulic conductivity of the lower clay unit have influenced near-surface groundwater
within the entire study area. The presence of the lower clay unit has essentially prevented
groundwater from migrating to deeper aquifers. Instead, groundwater in near-surface
aquifers discharges to surface water (Rogers and Murray 1997). Inspection of the ground-
water flow direction at each contaminated site revealed a good correspondence with the
direction of surface water flow.
1.4.1.3  Surface Hydrology
• Regional climate and stream type relationships (e.g., influent/effluent stream
types , drainage density)
• Watershed area
• Surface water characterization: streams, wetlands, lakes
• Floodplain structure and flood frequency
• Water quality issues
Example :
Situated within the humid microthermal climate zone of the Midwestern United States,
the Rouge River is effluent, meaning it is fed by groundwater entering as baseflow. Thus,
any significant contamination of groundwater that does not readily degrade or attenuate
will ultimately be delivered to the surface water drainage network (Murray et al. 2000).
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