Water and the Hydrogeology of Watersheds - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 98

Marsh vegetation
Groundwater seeping
to the surface
FIGURE 3.39
Groundwater seep in the Rouge River watershed where groundwater contamination is discharging to surface
water. (Photo by Daniel T. Rogers.)
(Alley et al. 1999). Since streams and rivers flow through varied terrain and geology, it is
possible that one stream may exhibit the three types of connections depicted in Figures
3.36 through 3.38.
At any specific location, a stream is either gaining, losing, or disconnected depending on
geographic, geologic, hydrologic, and anthropogenic factors.
During one study of the Rouge River watershed in southeastern Michigan, the direc-
tion of groundwater flow was evaluated at several hundred sites within the watershed
(Rogers 1993, 1994). Groundwater flow direction was established using a minimum of 6
and a maximum of 80 monitoring wells per site, and each monitoring well was surveyed
by a licensed surveyor. In a more detailed study of the lower branch of the Rouge River,
Murray et al. (2000) installed 54 groundwater monitoring wells along the river along with
18 well points installed into the river's bed sediment.
The results of these studies conclusively show that groundwater flow is discharging
through the bed sediment into the river and in a downgradient direction, consistent with
the direction of surface water flow.
This is significant for an urban watershed like the Rouge for these reasons: (1) the direct
connection between groundwater and surface water means that contaminants released
within the watershed may impact shallow groundwater and (2) this contamination could
also reach surface water and the lower Great Lakes (Rogers 1996, 1997; Rogers and Murray
1997; Murray et al. 2000). Figure 3.39 is a photograph showing one of numerous ground-
water seeps within the Rouge River watershed, and Figure 3.40 provides a close-up view
of this seeping water.
3.6.2 Lake Interaction with Groundwater
Lakes interact with groundwater in three basic ways. Some lakes receive groundwater
through the entire bed of the lake, some lakes have water loss through the entire bed of
the lake, and perhaps most commonly, lakes receive groundwater at some locations of
the bed and have water loss to groundwater at other locations. These three scenarios are
depicted in Figure 3.41 (Winter et al. 1998). Scenario A represents water loss from a lake to