Surface Water-Groundwater Interaction CSIRO Land and Water Home Page

Flow Through-Recharge - example 2

Problem Description

Non-dimensional Ratios:

Geometry
2a /B 0.25 Ratio of lake length to aquifer depth.
2a /LR 0.02 Ratio of lake length to regional length of aquifer.
LL /LR 0.5 Position of the lake within the regional setting, normalised by the regional length.
 
Aquifer Properties
KH /KV 1 Hydraulic conductivity anisotropy.
SoB 1.0E-05 Aquifer elastic storage coefficient.
Sy 0.3 Aquifer specific yield.
 
Boundary Fluxes
RLs /Rs 15 Ratio of average lake recharge to average aquifer recharge.
RLaSy /Ra 0.5 Ratio relating theamplitude of fluctuation in lake recharge to the amplitude of aquifer recharge.
q /P 0.5 The phase difference between the lake and aquifer recharges, normalised by the period.
 
System Response
LR2Sy /KHBP 0.469 Non-dimensional response time describing the ability of the lake-aquifer system to propagate periodic forcing applied at the boundaries.
RsLR2 /KHB2 0.0586 A non-dimensional measure of the mean height of the regional groundwater mound above the groundwater level at the regional discharge boundary.
RaP /SyB 0.4 Ratio describing the size of potential fluctuation in advective flowpaths relative to the aquifer depth.

Near-Field Animation

Flow-through-Recharge:

Animated gif: 24 frames per period

See description below...
 
Description:
This examples depicts a Flow-through-Recharge regime in which the left-hand or up-gradient portion of the lakebed fluctuates between discharge (groundwater outflow to the lake) and recharge (lake water inflow to the aquifer). Because the amplitude of fluctuation in aquifer recharge is larger than the average or steady-state value, there is negative recharge during part of each cycle; see the recharge animation above. This causes the regional flow direction to temporarily reverse and forces the lake release zone 'up-gradient' into the aquifer. Note that the aquifer and lake recharges are exactly half a period out of phase. Aquifer recharge is always positive.

 

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