Environmental Engineering Reference
In-Depth Information
Table 9.1.
Time scales for application of individual methods for estimating groundwater recharge. “Event” refers to a time period that may be less than but not more
than 1 day. “Steady” indicates that a method can provide a time-invariant estimate of recharge. Under “Data collection frequency”, 0 means that existing data are used
and no new data need to be collected, 1 means that data need to be collected at only one time, and m implies that data must be collected multiple times. Additional
details are discussed in the text. UZ is unsaturated zone. WB is water budget. GW is groundwater. WS is watershed. SW is surface water. HS is hydrograph separation.
R is recharge. D is drainage through the unsaturated zone. B is base low. CFC is chloroluorocarbons. SF
6
is sulfur hexaluoride.
Ty pe
Time scales
Recharge
Data
collection
frequency
Drainage or
Base low
Multi-
annual
Method
Focused
Diffuse
Event/daily
Weekly
Seasonal
Annual
Decadal
Millennial
Steady
Water budget
aquifer
x
x
R,B
x
x
x
x
x
m
soil column
x
R,D
x
x
m
watershed
x
x
R,D,B
x
x
x
x
m
stream
x
x
R,D,B
x
x
1,m
Models
UZ soil WB
x
R,D
x
x
0,1,m
UZ Richards
x
R,D
x
x
0,1,m
equation
watershed
x
x
R,D,B
x
x
0,1,m
(WS)
GW low
x
x
R,B
x
x
x
x
x
0,1,m
combined
x
x
R,B
x
x
0,1,m
WS/GW
empirical
x
x
R
x
x
x
0
Darcy methods
UZ
x
D
x
x
m
UZ unit
x
D
x
1
gradient
GW
x
x
R
x
x
x
x
m
SW/GW
x
R
x
x
m
