Environmental Engineering Reference
In-Depth Information
Table 9.2.
(
Cont.
)
Space scales
1
m
2
10
m
2
100
m
2
1
ha
1
km
2
10
3
km
2
10
6
km
2
Relative
expense
Relative
complexity
Chapter
recession-
4
x
x
2
3
curve
displace-
ment
chemical
4
x
x
x
5
4
HS
tracer
4
x
x
x
4
3
injection
Tracer methods
UZ
7
x
x
3
2
chloride
UZ tritium
7
x
x
3
3
UZ
chlorine-36
7
x
x
4
3
UZ applied
7
x
x
x
4
3
UZ heat
8
x
x
3
3
GW
7
x
x
2
2
chloride
GW
7
x
x
3
3
carbon-14
GW tritium
7
x
x
3
3
GW
7
x
x
4
3
chlorine-36
GW CFC
7
x
x
3
3
GW SF
6
7
x
x
3
3
GW
7
x
x
x
5
4
tritium/
helium-3
GW
7
x
x
4
3
applied
SWGW heat
8
x
3
3
take estimates derived from annual or multian-
nual data to develop estimates for shorter time
intervals. Methods based on tracers typically
provide a recharge estimate that is an aver-
age value for the time interval between tracer
application and sampling. An estimate based
on chlorofluorocarbon (CFC) concentrations in
groundwater (
Section 7.3.3
) could provide an
average recharge rate for perhaps the previous
20 years, but no information would be provided
calculations with smaller time intervals (e.g.
daily or weekly) and summing over the period
of interest. As discussed in
Chapter 2
, the inter-
val over which calculations are made affects
estimated recharge rates. For water-budget
methods, shorter time intervals generally pro-
duce larger estimates of recharge (
Section 2.2
).
While it is possible to upscale estimates by
summing estimates generated with shorter
time intervals, it is generally not possible to
