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

Qo= flow at the start of the recession (m 3 s -1 )
a= basin constant (days -1 )
t = time since the beginning of the recession (days)
MONITORING NETWORKS AND METHODS
Butler (1957) used a semilog plot of discharge against time to derive a near straight line for
baseflow recession. He used the recession equation in the form:
10 K
K
Q =
1
/ 2 t
K1= groundwater discharge at the start of the recession (Qo)
K2= time increment corresponding to one log cycle change in discharge
Q = discharge
t = time since start of the recession
By integration of this expression it is possible to derive the total discharge over a time period
(t1 to t2)
t 2
t 2
⎡− K1K
2 / 2.
3⎤
Total Discharge
= ∫Qdt = ⎢ t / K 2
t1
10
⎥
⎣ ⎦t1
Meyboom (1961) used the integral between time equal to zero and infinity to derive an
expression for the total potential groundwater discharge (Qtp) for the recession period.
Qtp=K1K2/2.3
If the actual discharge from a recession is subtracted from the total potential discharge this
leaves the remaining potential discharge (Qrp). If Qrp is subtracted from the new Qtp of the
94