The impact of urban groundwater upon surface water - eTheses ...

MONITORING NETWORKS AND METHODS
Run-off relatively short term component associated with precipitation events;
Interflow subsurface flow derived from a precipitation event which reaches the river
without recharging the underlying groundwater system;
Bank storage the release after a flood event of river water that has entered the adjacent
sediments with head gradient reversal during the flood event. This is at
maximum during the falling limb of the flood hydrograph. An effect similar to
bank storage may occur with the release from storage of groundwater unable to
discharge during the flood event;
Baseflow is the long term discharge that sustains the river during dry weather flow
(DWF) periods. This will contain a major component of groundwater
discharge from the underlying bedrock aquifer and drift deposits.
Anthropogenic inputs including treated sewage effluent and industrial
discharges also comprise a significant component in this urban catchment.
The identification of the groundwater component of river baseflow is best accomplished
under dry weather flow conditions when run-off and interflow are minimal. The groundwater
discharge will fluctuate, depending on the regional head conditions. These will vary over
time, and are dependent on recharge and abstraction rates. Groundwater discharge follows an
exponential decline or recession during DWF until a recharge event occurs marking the start
of a new recession period. This recession may be described (Fetter, 1994) by the expression:
Q=Qoe -at
Q= discharge at time t (m 3 s -1 )
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