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Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Implementing hydrology (groundwater and rivers)
into RAMS
Gonzalo Miguez Macho,Group of non-linear Physics
Universidade de Santiago de Compostela, Galicia, Spain
Ying Fan (1), Chris P. Weaver (2), Robert L. Walko (3), Alan Robock (2)
Departments of (1) Geology and (2) Environmental SciencesRutgers University, New Brunswick, New Jersey, USA(3) Department of Civil and Environmental Engineering
Duke University, Durham, NC , USA
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
What does groundwater do for climate?
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
What does groundwater do?
- redistributes soil water in space
- sustains stream flow in humid and sub-humid climate, receives loosing streams in arid climate
- temporarily holds wet-period infiltration, and later supplies dry-period evapotranspiration
1. Atmosphere
2. Soil-Vegetation 3. River Network
4. Groundwater
OceanNear Surface
Subsurface
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
10
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0.50.40.30.20.10.0
Soil Water Content
Silt Loamcapillary rise 0.45meffective porosity 0.35pore-size distrib. index 1.20
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0.50.40.30.20.10.0
Soil Water Content
Sand Loamcapillary rise 0.25meffective porosity 0.25pore-size distrib. index 3.30
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0
De
pth
Belo
w L
and
Surf
ace (
m)
0.50.40.30.20.10.0
Soil Water Content
Clay Loamcapillary rise 0.90meffective porosity 0.45pore-size distrib. index 0.44
Equilibrium soil water profile above a water table at four depths (1, 2, 5, and 10m) for the three soil types in Salvucci and Entekhabi (1995).
The water table acts as a lower boundary condition for the unsaturated soil
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Water table depth (m) measurements over the U.S.
Shallow water
tables cover large
areas of North
America.
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Temporal Variability30
20
10
0R
ain
fall (
mm
)
3603303002702402101801501209060300
2.0
1.5
1.0
0.5
0.0
(m)
3603303002702402101801501209060300Day in 2003
1.6
1.4
1.2
1.0
0.8
0.6
(m)
270265260255250245240235230225220215210205200195190185180Day in 2003
6.0
5.0
4.0
3.0
W
ate
r T
ab
le D
ep
th
3603303002702402101801501209060300Day in 2003
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5.6
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4.8
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W
ate
r T
ab
le D
ep
th
270265260255250245240235230225220215210205200195190185180Day in 2003
(a)
(b)
(c)
(d)
(e)
(f)
Bound Brook Hourly Precipitation Station
Morrell 1 Well (depth = 3.35m)
Readington School 11 Well (depth = 15.24m)
Readington School 11 Well (depth = 15.24m)
Morrell 1 Well (depth = 3.35m)
Bound Brook
Rainfall
Station
Readington
School 11
Well
Morrell 1
Well
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
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1 Oregon
California
3 Idaho
4 Montana
5 Utah
6 New Mexico
2
7 Texas
8 Nebraska
9 Kansas
10 Louisiana
Year since 01-01-1990 Period (days)
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
A strong annual
cycle is present at most sites,
along with even longer-term
variability.
The memory of both event-scale
and seasonal-to-interannual
variations are contained in the
groundwater record.
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Equations:
Mass balance in groundwater storage:
Darcy’s Law for lateral groundwater flow:
Darcy’s Law for groundwater – river exchange:
Mass balance in surface water storage:
River flow routing from cell to cell to the ocean:(linear reservoir model)
rQQyRx
dt
dSn
g−+∆∆= ∑
8
1
( ) ( )∑
−= rr
rb
rbrbr Lw
b
KzhQ
snrhs QIQQ
dt
dS−++= ∑
7
1
Qs = Ss / ks
Incorporating water table dynamics into the Regional Atmospheric Modeling System (RAMS)
−
⋅=
∫ ⋅+∫ ⋅∞∞
s
hhwQ
nwtdwtd n dzKdzKn
n
2
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Atmospheric model grid cell
Soil-Hydro modelgrid cell
rQQR
dt
dn −+= ∑
8
1
wtd
Recharge
Water table depth
Lateral flowDischarge to rivers
Mass balance
Land surface
Recharge4m
Water table 1
15 Soil Layers
Water table 2
Ql lateral flow
Qr river discharge
variable thickness
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
−
⋅=
∫ ⋅+∫ ⋅∞∞
s
hhwQ
nwtdwtd n dzKdzKn
n
2Lateral flow
wi,j
i, j
Q1
Q2 Q3
Q4
Q5Q6
Q7
Q8
Plan view
h i,j
Mean sea level
Sg
Q8
Q4
R Qr
Cell ij
Cross section view
width of flowcross section
TransmisivityHead difference
divided by distance
conductivity
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Surface water (rivers and lakes)
snrhs QIQQ
dt
dS−++= ∑
7
1
s
ss
k
SQ =
( )rbedwtdrcondQr −⋅=
Surface runoff
Groundwater
discharge River inflow from
neighboring cells
River outflow
Mass balance
Residence time
River
conductanceRiver bed
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Simulation domain (hydro 12.5 km res., atmosphere 50 km res.)and elevation (m) for the hydro cells.
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Initial conditions for water table depth, river flow and soil moisture
-First calculate “equilibrium water table depth” at high resolution (~1.25 km):
Start at the surface and find the depth at which the mean annual recharge compensates lateral flow (recharge estimated from VIC model 50 year simulation at 1/8º resolution).
Dry climate
Humid climate
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
1.25 km res.
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Topography exerts greatest influence
1.25 km res.
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Simulation Period 1: Hydrology spin-upGroundwater + River flow: 10 yr (1987-1997), using observed Prep. and VIC estimated ET and surface runoff
1. Atmosphere
2. Soil -Vegetation 3. River Network
4. Groundwater
Ocean
P
Q
Inf
1 layer
ET
Water table
Qr to rivers
forcing
water table
response
baseflow
Example for a location in Kansas
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Simulation Period 2: Unsaturated soil layers and vegetation addedGroundwater + River flow + Unsaturated Soil + Vegetation: 12 months (01-01-1997 to 12-31-1997), 60-sec step, using observed atmospheric and radiation forcing
1. Atmosphere
2. Soil -Vegetation 3. River Network
4. Groundwater
Ocean
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Infiltration (mm)
Soil moisture (volumetric)
Water table depth (m)
Quick in learning
Slow in forgetting
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Simulation Period 3: Evaluating the impact of the newly implemented processes. Compare to gravitational drainage or no drainage at the bottom. Atmospheric and radiative conditions from observations or reanalysis.6 months (05-01-1997 to 09-30-1997)
Groundwater
Control Run: RAMS-Hydro
3 Experiments:
Free-Drain (FD) No-Drain (ND)
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Monthly precipitation from observations
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Water table depth
The pattern doesn’t vary much. Water table depths oscillate (order 1m) around the equilibrium value
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Soil moisture in the root zone (top 2m)
Soil moisture horizontal distribution resembles the water table map, even after a dry summer. Groundwater increases persistence of soil moisture conditions
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Recharge : flux of water to or from the water table
Blue areas are regions where groundwater is supplying water to the unsaturated soil layers on top
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Difference in root zone soil moisture: water table run – free drainage run
Run with free drain scheme is much drier in shallow water table areas
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Difference in root zone soil moisture: water table run – no drain run
Run with no drain scheme is much wetter over extensive areas
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Conclusions:
-Groundwater has a strong influence on near surface soil moisture distribution at continental scale.
-There is a large spatial variability in water table depth across a continent. Any uniform treatment of soil water drainage (free drain, no drain) will likely bias certain regions.
-Groundwater is quick in learning and slow in forgetting the climate forcing. This has important implications for atmospheric processes and land-surface feedbacks. Past climatic events are preserved in the subsurface and can be recalled at a later time to affect soil water fluxes and river flow.
Gonzalo Miguez MachoNon-linear Physics Group
Universidade de Santiago de Compostela
Groundwater
Control Free-Drain No-Drain
?
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