1.4 Flow-through Conditions

A flow-through condition occurs when the water table is higher at one side of the feature than the surface-water stage (river, lake, and wetland) and lower at another location (Figure 7). In this scenario, groundwater is discharging into the surface water and surface water is seeping into the groundwater system. Under flow-through conditions, surface water is added to and lost from the surface feature’s volume and/or flow over a specified time interval. Generally, the surface-water stage reflects the water table in most settings. Representative monitoring wells illustrate that water levels in wells at different depths (open only at the bottom) are higher than the surface-water stage in the area where effluent conditions are present and lower in areas that are influent. Flux rates of groundwater are dependent on the magnitude of the hydraulic gradient at the boundaries, and the hydraulic conductivities of the geologic sediments and the banks and bottom of the surface-water feature.

Figure showing conceptual model of flow-through conditions under steady-state, isotropic and homogeneous conditions
Figure 7 – Conceptual model of flow-through conditions under steady-state, isotropic and homogeneous conditions. Numbers represent relative values of head. Dashed lines are equipotential lines and arrows represent general groundwater flow directions. Monitoring wells are only open at the bottom. Water levels in up-gradient monitoring wells (left) are higher than the surface-water stage. Water levels in down-gradient monitoring wells (right) are lower than the surface-water stage. In this example, the surface-water stage represents the water table (Woessner, 2020).

License

Groundwater-Surface Water Exchange Copyright © 2020 by William W. Woessner. All Rights Reserved.