Modelling surface freshwater
temperature
Tracking spatio-temporal variations with a
global hydrological model
Rens van Beek
Department of Physical Geography, Utrecht University
Overview
•
•
•
•
Introduction
Methods
Results
Summary
Acknowledgements:
Tessa Eikelboom, Yoshihide Wada, Marc Bierkens, and Michelle van
Vliet (WUR)
Introduction
• Water temperature influences physical,
chemical and biological processes:
– Ice formation;
– Hydrochemistry;
– Aquatic habitats.
• Rivers transport heat along the Earth’s
drainage network:
– Local effects;
– Regional effects.
Water quality and temperature
Trends in water
temperature New Zealand
(www.mfe.govt.nz)
Water temperature and O2 for the
Murray River (www.gemswater.org)
Great Lakes
Thermal regimes
http://coastwatch.grerl.noaa.gov
Great Lakes
Spatio-temporal variations
http://coastwatch.grerl.noaa.gov
Modelling surface freshwater
temperature globally
• Rationale:
–
–
–
–
–
Trends of temperature and discharge
Effect on regional energy balance
Substitute for scarce long-term records
Amenable to different environmental settings
Strong physical basis yet computationally
expedient
• Objective:
Evaluate simulated surface freshwater
temperatures against observations for different
environmental settings.
Methods
• PCR-GLOBWB model description
• Simulated vs. observed discharge (GRDC)
• Simulated vs. observed water temperature:
–
Timeseries:
• Rivers
• Lakes
– Climatology:
• Rivers
Model Structure PCR-GLOBWB
Model resolution:
• Regular grid of 0.5° (50 km);
• Daily time step
Each cell describes:
• The vertical flow of water through four
compartments:
– Canopy;
– Three soil compartments.
• Soil and canopy are fed by rainfall and snowmelt
and depleted by evapotranspiration;
• The transfer of runoff to the drainage network.
• Subgrid parameterisation at 1 km
Between cells:
• Kinematic wave routing of water along drainage
network;
• Surface water represents either streams or lakes
that can cover multiple cells and buffer stream
flow.
• Reservoirs (+ operation), lakes, wetlands,
floodplains included (+ evaporation)
Model Structure PCR-GLOBWB
QChannel
PREC
Epot
PREC
Epot
Canopy
River ice
Eact
QDR
T
Tw
Snow cover
RS
TA
Snow/Rain
Store 1
P
RS
QSf
LH(Epot)
TA
Store 2
Q
QBf
Snow/Rain
P
Store 3
QChannel
Surface water energy balance
S↓
Advected energy:
Base flow: mean annual temperature
L H
λρ w E
Direct runoff and precipitation:
daily temperature
ρ wC p qsTs
As
ρ wC p Q ( x)T ( x)
A
ρ wC p [QT ( x) +
∂ (QT )
dx ]
∂x
dx
Energy balance (J m-2 s-1) for a rectangular channel
ρ wC p
∂ (hT )
∂ (vhT )
= − ρ wC p
− ( S ↓ (1 − α w ) + L7 + H + λρ w E ) + ρ wC p qsTs
∂t
∂x
Ice growth and hydraulic effects
dz
dE
1
=−
if Ta < 0
dt
λ f ρ w As dt
Effects on river hydraulics:
P= 2h + W → P = 2h + 2W
⎛ ni + nb
nc = ⎜⎜
2
⎝
3
2
3
2
⎞
⎟
⎟
⎠
2
01/07/2000
3
31/12/2000
Simulations
Not-included in PCR-GLOBWB:
• Dynamic vegetation
• Sub-grid snow redistribution and temperature lapse
• Permafrost and active-layer dynamics
• Soil/surface energy balance
• Lake stability and mixing
• Not calibrated
• Natural flow, forced with CRU TS 2.1 and ECMWF ERA-40
Observations
USGS River Stations and NOAA Lake Observations
GRDC Climatology
long-term stations
GEMS
Holdridge Life Zone Classification
Ocean
Boreal Forest
Hot Desert
Tropical Dry Forest
Tundra
Cool Desert
Chapparal
Tropical Seasonal Forest
Cold Parklands
Steppe
Warm Temperate Forest
Tropical Rain Forest
Forest Tundra
Temperate Forest
Tropical Semi-Arid
GRDC long-term inventory
Results: Runoff
Large-basins (≥ 100 000 km2)
All stations (N= 1938)
Results: Discharge
GRDC long-term inventory: large-basins (≥ 100 000 km2)
Seasonality
Inter-annual variability
100
75
50
25
0
100
75
50
25
0
-25
-50
-75
-100
171
Ar
ka
ns
Ar as
ka ab
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ka s
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ns Jo ue
as hn bl
o
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ol
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or rad nim
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or o ee's eo
ad lo
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U
o r
G De tah Si y
re la S lv
en w ta er
R are tel
iv
Po
er Tr ine
to
C e
m J am nto
ac ac p n
Sa Wa kso bel
n sh n R ls
So Joa ing ive
ut qu ton r
h in
Fo V DC
rk ern
S
W
t
hi C Mc alis
te ro ke
R ix nz
iv M ie
er ill
C tow
en n
te
rto
n
Results: River water temperature
USGS Daily temperature
Coverage [%]
Alpha [-]
3
2.5
2
1.5
1
0.5
0
Error drainage area [%]
Spearman correlation [-]
1
307
0.75
0.5
0.25
0
Results: River water temperature
USGS Daily temperature
Results: Lake water temperature
NOAA Daily temperature
Lake
Spearman Correlation Slope Standard error
Erie
0.93
1.11
3.58
Huron
0.88
0.98
3.65
Michigan
0.92
0.99
3.13
Superior
0.87
1.20
3.70
Results: River water temperature
July
January
35
35
GEMS monthly climatology
30
Observed temperature (degrees Celcius)
Observed temperature (degrees Celcius)
30
25
20
15
10
5
25
20
15
10
5
0
0
0
5
10
15
20
25
Simulated temperature (degrees Celcius)
30
35
0
5
10
15
20
25
Simulated temperature (degrees Celcius)
30
35
GEMS monthly climatology
rSt
Ku
.L
su
a
O
M wr
b
r
iss e
R
iss nc e Am iv e
Ya ip
Ri ur R r
ng pi
v
tz R i e r ive
v
M e
-M r
ek R er
...
i
v
o
M ng er ( Vic
ek R
C k
on ive ha ...
Lo g
n
r
we Ri - C g J
M r G ver hia ...
ek a
n
on n g Kh g...
g es on
Ri
g
ve R iv ...
Am B r - er az rah Nak a..
on m
h .
as a p on .
R utra ..
ive
r - Riv
O er
bi
do
s
Alpha
Ri
ve
Correlation
Le
na
d
1.25
Tu
Pa nd
Fo r k ra
r e la
s n
Bo t T ds
re u nd
al
r
Co Fo a
ol r es
D t
Te
es
m
pe St ert
ra e p
te pe
W
Ho For
ar
m
t D est
Te
e
m Ch se
Tr p er app r t
o p at
e ar
Tr Tr ica F al
o p o p l S ore
i
e
Correlation,icAlpha
al cal [-] mi st
S D -A
Tr ea r y F rid
o p so
o
ica na res
lR lF t
a i ore
n
Fo st
re
st
Co
l
1.25
1.00
0.75
0.50
20
15
10
0.25
0.00
5
0
T [°C]
Holdridge Life Zones
Tropical
Rain Forest
30
25
Tropical
Seasonal
Forest
Tropical Dry
Forest
Warm
Temperate
Forest
Cold
Parklands
Tundra
1.00
0.75
0.50
0.25
Mean temperature
0.00
30
25
20
15
10
5
0
T [°C]
Correlation, Alpha [-]
Results: River water temperature
Forest
Tundra
Boreal
Forest
Cool Desert
Steppe
Tropical
Semi-Arid
Temperate
Forest
Major Rivers
Chapparal
Hot Desert
Results: ΔT
Average difference between water and air temperature for GEMS
stations for different climates
30
25
20
15
10
5
0
-5
r
N
ov
em
be
r
D
ec
em
be
r
ob
e
ct
O
em
be
r
st
Se
pt
Au
gu
y
Ju
l
Ju
ne
M
ay
Ap
ril
M
ar
ch
ry
Fe
br
ua
ry
-10
Ja
nu
a
Average difference air and water
temperature
35
Months
Tundra
Cool Desert
Chapparal
Tropical Seasonal Forest
Cold Parklands
Steppe
Warm Temperate Forest
Tropical Rain Forest
Forest Tundra
Temperate Forest
Tropical Semi-Arid
Boreal Forest
Hot Desert
Tropical Dry Forest
Results: ΔT
Difference between monthly water and air temperature, 2000
10
>
0
-1
5
-5
2.
5
.5
-2
1
-1
5
0.
.5
-0
.5
-0
0
-0
5
0.
--
1
--
-1
5
-2
.5
2.
--
-5
-0
-1
<
-1
0
5
Degree centigrade
Summary and conclusion
• Performance:
– Limited performance on daily scale:
• Small watersheds with daily measurements;
• Unresolved processes in case of lakes.
– Improved performance on a monthly scale:
• Interaction between simulated discharge and ice breakup: performance poorest for (sub) arctic rivers;
• Little variation between air and water temperature in
tropical regions.
• Rivers discernibly transport heat with water.
• Simulating water temperatures with global
hydrological models shows promise…
Thank you for your attention
Questions, no doubt?