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Santa Cruz AMA HydrologySanta Cruz AMA Hydrology & Groundwater
Modeling
Keith Nelson [email protected]
Arizona Department of Water Resources
Overview of Hydrology (Upper Santa Cruz)
Hydrologic Models 1) Understand System; 2) Simulate Projections
Groundwater Flow Models
Stochastic Streamflow Model
Combining Streamflow and Groundwater Flow Models
Risk Analysis Examples
Santa Cruz AMA Goals § 45-562C: 1) “Maintain Safe-Yield Conditions”
2) “Prevent local water tables from experiencing long-term declines”
1. Flood Event
Transmission
Losses in Channel
2. Aquifer Recharge: Water Table Rise ->
Baseflow?
3. Periods of Low / No Recharge combined
w/ Aquifer Stresses & Flux: GWL Decline
Relation between Surface water flow and Groundwater Levels
0.1
1
10
100
1000
10000
7/1/00 7/2/02 7/2/04 7/3/06 7/3/08
Su
rfa
ce
wa
ter
flo
w (
cfs
)
3390
3395
3400
3405
3410
3415
3420
3425
3430
3435
Ob
se
rve
d g
rou
nd
wa
ter
lev
el
(ft)
Stream Flow - Santa Cruz River: Baseflow Gaining (green); losing (red)
<---Intensive Drought---->
1
10
100
1000
10000
10/1/95 9/30/97 10/1/99 9/30/01 10/1/03 9/30/05 10/1/07 9/30/09
flow
(cfs
)
Groundwater Elevations at (D-23-14) BCB1 (GWSI and transducer data)
Groundwater levels prior to 1972 reduced 10 feet to account for measurement-point offset. Connected points reflect
seasonal measurements observed at frequencies > than once per year
3550
3560
3570
3580
3590
3600
3610
1/1/1940 12/31/1949 1/1/1960 12/31/1969 1/1/1980 1/1/1990 1/1/2000 1/1/2010
Gro
un
dw
ate
r L
ev
el
(fe
et)
Surface Water Flow at Nogales: Winter flows,
December 1st - March 31st
0.01
0.1
1
10
100
1000
10000
1/1/1931 12/31/1940 1/1/1951 12/31/1960 1/1/1971 12/31/1980 1/1/1991 12/31/2000 1/1/2011
Hydrologic Model
DOS Batch Program
inter-changing modules
~8 hrs on a 2X2.66GHZ; 3G
RAM
Stochastic
Stream Model >
Convert to
Stream-aquifer BC’s
Translate
Stream BC +
Demand >
through 6 ACM’s:
Analysis of Simulated
Heads and Flows:
trends; patterns
Inter-arrival stats
(MATLAB; FOXPRO)
Simulated Heads at Tumacacori: Base Model (shown) Realization #2 ("dry")
Years 1-90 Infrequent Flood Recharge; Years 91-100 Frequent Flood
Recharge
3205
3210
3215
3220
3225
3230
3235
3240
3245
0 3650 7300 10950 14600 18250 21900 25550 29200 32850 36500
time (days) 100 years
Sim
ulat
ed h
eads
(fee
t)
Pumpage = 15,000 AF/YR; Mean = 3235'
Pumpage = 19,000 AF/YR; Mean = 3231'
(D-21-13)19acc: Nearby adjusted observed,
historical range (pre-effluent) = 22'
Distribution of Simulated Heads at Chavez Siding, 100X6 ACM
Assigned Pumpage 15K
0
50000
100000
150000
200000
250000
300000
3090 3100 3110 3120 3130 3140 3150
Distribution of simulated head elevation (feet above MSL) for each time step
Fre
qu
en
cy
(to
tal =
4.2
E6
)
Pumping 15K: 75% chance gaining conditions will occur less than half of the time
Pumping 13K: 30% chance gaining conditions will occur less than half of the time
Years with Simulated Net Groundwater Discharge Between NIWTP and Tubac (100 max)
[100 Stream Realizations X 6 ACM's] X 6 Well Pumping Demands (from 11K to 23K AF/YR)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 10 20 30 40 50 60 70 80 90 100
Years with Groundwater Discharge (net gain) between the NIWTP and Tubac (out of 100 years)
Cu
mm
ula
tive P
rob
ab
ilit
y (
pd
f's)
Assu
med
No
rmal D
istr
ibu
tio
n
11 K 13 K 15 K
17 K 19 K 21 K
23K
Relation Between Pumpage and Occurrence of Groundwater Discharge (Gain)
0
10
20
30
40
50
60
70
80
90
100
11000 13000 15000 17000 19000 21000 23000
Groundwater Pumpage (AF/YR)
Years
wit
h g
rou
nd
wate
r d
isch
arg
e (
net
gain
)
betw
een
NIW
TP
an
d T
ub
ac (
ou
t o
f 100 y
ears
) 95th percentile (6 ACM)
50th percentile (6 ACM)
5th Percentile (6 ACM)
Findings
Apply models that are not adversely biased!
Simulate many plausible realizations
Ensemble results reveal system central tendencies
Reduce risk of ‘model’ bias impacting projection
Sensitive to Flood Recharge Inter-arrival Periods and Duration periods (trends)
Inner Valleys Probably Require Simulation at Seasonal Stress Periods
Broader extents and/or aquifers buffered by aquitards or distance may be simulated at annualized stress periods (or longer) along losing reaches
Sensitive to ACM and boundary conditions
Tucson AMA Model
(DRAFT Projection)
1940-65: 33,750 AF/yr (28%)
1966-95: 52,780 AF/yr(51%)
1996-2010: 43,950 AF/yr (21%)
Typical Prescott AMA Hydrograph (Below)
Elephant Head/Amado-North
Chavez Siding (Tubac-north)
Canoa
Questions?
Thanks to ADWR Basic Data & Survey Units; Hydrologic
Research Center (San Diego); USGS (Tucson); U of A; Santa
Cruz AMA GUAC and staff; IBWC; FOSCR; AZ State Parks