Climate change, growth, and
managing the Edwards Aquifer
Hugo A. Loáiciga
Department of Geography
University of California
Santa Barbara, California USA
1
Loáciga et al 1996 (USEPA)
2
outline
• I. Introduction
• II. Is the Earth warming?
• III. Ground water impact predictions
• IV. Final Remarks
3
I. Introduction
4
5
San Marcos Springs
San Marcos Texas
6
Texas blind salamander: a EABFZ karst dweller; endangered
fishes, and aquatic plants, other invertebrates, are also threatened
7
Recharge mechanism: EABFZ
Puente (1978, USGS San Antonio office)
QI
del Ri
o
QA
R=QI+QA-Q0 + δ
δ: spatial recharge
Edwa
rds
QO
R
Glen R
ose
8
6
Texas climatic divisions: red division (6) is the Edwards Plateau
9
Recharge (106 m3)
10000
Precipitation (cm)
Precipitation: Division 6 Texas
1000
100
10
1930
1940
1950
1960
1970
1980
1990
2000
2010
Calendar Year
10
San Antonio is point measurement; Division 6 is spatial average
Precip. (cm)
San Antonio
Division 6 Texas
140
120
100
80
60
40
20
0
1930 1940 1950 1960 1970 1980 1990 2000 2010
Calendar Year
11
San Antonio precipitation vs. recharge (annual, calendar)
6
3
Recharge (10 m /yr)
3200
2800
2400
R = 19.027 P - 585.12
2
R = 0.5287
2000
1600
1200
800
400
0
0
20
40
60
80
100
120
140
Precipitation (cm/yr)
12
R
P
R-5
P-5
10000
6
3
Precipitation (cm) or recharge (10 m /yr)
Moving-averages
1000
100
10
1930
1940
1950
1960
1970
1980
1990
2000
2010
Year
No discernible secular changes in P, R
13
Variability of recharge
R-5
R-stdev(5)
10000.0
6
3
recharge or stdev recharge (10 m /yr)
R
1000.0
100.0
10.0
1930
1940
1950
1960
No discernible secular changes
1970
Year
1980
1990
2000
2010
14
Recharge
Pumping
1.00
9
3
Flux (10 m )
10.00
drought
0.10
Conflict
0.01
1930
1940
1950
1960
1970
1980
1990
2000
2010
Calendar year
15
Recharge
Spring flow
1.00
9
3
Flux (10 m )
10.00
0.10
drought
0.01
1930
1940
1950
1960
1970
1980
Calendar year
1990
2000
2010
16
Estimate storage capacity ? ST = sum[recharge-pumping-springflow]
3
Change in storage (10 m )
3
2
9
9
3
?S~ 5.5 x 10 m
1
0
-1
-2
-3
1930
1940
1950
1960
1970
1980
1990
2000
2010
Calendar year
17
Maximum annual yield: springflow+pumping Loaiciga (2008) J. Hydrogeology
70
50
9
3
Cumulative recharge (10 m )
60
40
9
3
slope = 0.76 x 10 m /yr
30
20
=5.5x109 m3
10
0
1930
A
1940
1950
1960
1970
1980
1990
2000
2010
Calendar year
18
Annual Precip and Recharge have short “memory”
Recharge
Precip
1.00
Autocorrelation
0.80
0.60
0.40
0.20
0.00
-0.20
0
2
4
6
8
10
12
14
16
18
20
Lag (years)
19
Cross correlation is poor beyond lag > 1 year
Crosscorrelation
0.80
0.60
0.40
0.20
0.00
-0.20
-20
-15
-10
-5
0
5
10
15
20
Lag (years)
20
Smoothed spectra: no dominant frequencies;
smoothed cross spectrum: suggests R ∼ P
precipitation
recharge
cross spectrum
Spectrum or cross spectrum
10.0000
1.0000
0.1000
0.0100
0.0010
0.0001
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
Frequency
21
II. Is the Earth Warming?
22
Long-term northern latitudes surface temperature, M. Budyko, 1977, AGU
Long-term cooling trend
impact
10 degrees C
K-T
23
Long-term atmospheric CO2 from Berner (1997) Science
RCO2 = CO2 concentration/300 ppmv
24
CO2
Ice Age
Higher deep sea δ18O à
colder sea temperature: cooling trend
380
180
T (atm.)
25
Feodorov et al. Science vol. 312 p. 1485, 2006
Scafetta & West
26
Temperature is important…
• but: hydrologically, this is what matters:
• ? S = P – ET – Q - D
• And we want to know about changes
in:
• δ (? S) = δP – δET – δQ - δD
27
III. Ground water predictions
28
Historical time series:
Simulate 1xCO2 (1990)
adjustments:
P2xCO2scenario = (P2xCO2/P1xCO2)Phistorical
T2xCO2scenario = (T2xCO2 – T1xCO2)+Thistorical
P2xCO2scenario , TCO2scenario
simulate 1xCO2
adjust to 2xCO2
D
D2xCO2
time
time
Drought threshold
Global warming prediction: a time tunnel approach.
Do past feedbacks hold in the future? Roe & Baker Science 2007
29
GCM grid
Nesting approach
Regional Climate
Modeling grid
The aquifer scale
30
N
100 W
NCAR’s Vegetation/Ecosystem Modeling and Analysis Project (VEMAP,
1995) grid and factors over the Edwards aquifer
Austin
S
#
30 N
S
#
S
#
Graticule
VEMAP Grid
Cities
Study Region
0 10 20 30 40 50 Miles
0.5° x 0.5° grid cells
San Antonio
Edwards Aquifer
31
GWSIMIV numerical grid
32
GWSIMIV numerical simulator
Texas Water Board (1997)
•
∂h 

∂h 

∂  T( x, y)  ∂ T( x, y) 
∂y 
∂h
∂x 


= S( x , y )
+ N ( x, y)
+
∂y
∂t
∂x
N = recharge – springflow - pumping
PCO2scenario, Tscenario àRecharge
à pumping
à Simulate h,
springflow
33
6
3
Minimum monthly spring flow (10 m )
32
Average precipitation
1978-1989
28
Comal
24
20
Recommend Pumping
5.0≤P≤ 6.5 x108 m3/yr
16
Max. yield ~ 7.6 x 108 m3/yr
12
Minimum
8
4
San Marcos
0
0
1
2
3
4
5
6
8
3
7
8
9
-1
Pumping rate (10 m yr )
34
6
3
Minimum monthly spring flow (10 m )
20.0
18.0
16.0
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
Comal
Drought conditions
1947-1959
Recommend Pumping
Minimum
0≤P≤2 x108 m3/yr ?
Max. yield ~ 7.6 x 108 m3/yr
San Marcos
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0
8
3
-1
Pumping rate (10 m yr )
35
Implication:
• The sustainable g.w. extraction rate must
be adaptive: it changes as recharge
changes its level over several years.
36
Population and climate
•
•
•
•
Z = total hydrologic response
H = human impact by groundwater extraction
C = climate impact by changed recharge
Then: Z = f(H,C)
∂f
∂f
∆Z =
∆H +
∆C
∂H
∂C
37
Scenario
Base: I
Climate
(recharge)
R1978-89(1)
Groundwater
use
1978-89 use
Climate
change: II
2 xCO 2
1xCO1
1978-89
use
groundwater
change: III
1978-89 use(3)
2050 use(4)
Total effects:
IV
2 xCO 2
1xCO1
2050 use
Notes:
(1): historical recharge during 1978-1989, whose mean was = 0.77 x 109 m3 yr-1;
(2) the historical recharge is scaled to 2xCO2 conditions according to equation (7);
(3) the average ground-water use during 1978-1989 equaled 0.567 x 109 m3 yr-1; 38
(4) the year 2050 ground-water use forecast equals 0.784 x 109 m3 yr-1.
RESULTS:
Edwards aquifer springs
Climate and groundwater use scenario(1)
Comal
San Marcos
Minimum flow
106 m3/month
Minimum flow
106 m3/month
I (Base)
4.8
4.8
II (Recharge change only)
13 ↑
6.0 ↑
III (Pumping change only)
0.0 ↓
3.8 ↓
IV (Recharge & Pumping
changes)
1.3 ↓
4.8
39
IV. Final remarks
• Climate change AND population change:
the latter is dominant in the EABFZ.
• Climate/hydrologic change (global warming
post-1700): a tougher problem to predict
than sometimes acknowledged (see IPCC
2007);
• Adapt: conserve, reuse, diversify sources,
• design considering variability and
uncertainty.
40