Introduction to
Environmental Isotopes
Stefan Uhlenbrook and Jochen Wenninger
UNESCO-IHE, VU Amsterdam and TU Delft, Delft, Netherlands
5 November 2009, Dutch Hydrology Meeting to receive the
Darcy Lecture 2009, by Dr. Peter Cook, VU Amsterdam
Outline of This Lecture
1. Introduction
2. How can environmental isotopes help to
detect and quantify global change impacts
on water?
Evaporation
Runoff generation
Groundwater
Precipitation
3. Concluding Remarks
2
4
3
5
6
1
0
G
lo
ba
l
Te
m
pe
ra
tu
re
(°
C
)
IPCC Projections
2100 AD
N
.H
. T
em
pe
ra
tu
re
(°
C)
0
0.5
1
-0.5
1000 1200 1400 1600 1800 2000
Lower Risk for
Instabilities
High Risk
for Instabilities
It is Getting
Warmer!
The context – ONE
'climate colonialism'
A massive land-grabbing
scramble in Africa as
foreign companies -
some with foreign aid
money support - rapidly
establish enormous
monoculture fields in
tropical countries.
Prof Seif Madoffe, SUA
Sugar Cane – Kilombera Basin,
Tanzania
The context – TWO
Global Changes
Climate (temperature, precipitation, radiation …)
Land use, land cover
De-forestation / re-forestation
Urbanisation
Etc.
Population (amount, density, structure, …)
Water use in space and time
Economic development
Change of diet (more meat => more water)
N- and P-fluxes to water bodies
Pollution (new substances etc.)
Change in composition of species
etc. etc. etc.
…. and many interdependencies/feedbacks!
Picture from Fairless, 2007, Nature
EIEIET ETES ES
SS SS
QR QR
QR QR
QS QS
P P
P P
Impacts of land use change on hydrological
processes P=Q+E+dS/dt
Short-term dynamics (e.g. interception, flood generation) vs.
long-term dynamics (e.g. groundwater recharge, base flow)
PQQEEQEE ggfuTusssII dtdSdtdSdtdSdtdS
II EdtdS Interception processes
sss QEdtdS Surface water processes
g
g Qdt
dS
Groundwater processes
Water Balance Equation: P=Q+E+dS/dt
Where:
Root zone moisture processes fuTu QEEdtdS
Possible changes in all variables due
to climate and/or land changes!!
Weatherley catchment, South Africa
How can Environmental
Isotopes help??
Environmental Isotope – Basics
16
O
8
Mass number (= protons + neutrons)
Atomic number (= protons)
18
O
8
8 protons (positive), 8 electrons
(negative), 8 neutrons (neutral)
8 protons, 8 electrons, 10
neutrons
- Nuclides with same atomic number (i.e. an element) but different mass
number are called isotopes
- 92 natural elements have more than 1000 stable and radioactive isotopes
- Protons and neutrons in the nucleus have approximately the same
weight
- Electrons (negative charge) are lighter and are located in electron shells
Some common environmental isotopes
Source: Kendall, 1998
Picture from Fairless, 2007, Nature
EIEIET ETES ES
SS SS
QR QR
QR QR
QS QS
P P
P P
Investigation of different compartments of the water
cycle using environmental isotopes
P=Q+E+dS/dt
Meteoric Water Line (MWL): The Concept
Source: IAEA
Observing evaporation using environmental
isotopes in big systems
Agarwaal et al., 2002
Transpiration Evaporation
Soil moisture
sensors
Data Logger
Soil
Balance
Percolation
Rhizon water
samplers
Better Understanding of Evaporation Fluxes
using Environmental Isotopes
Wenninger et al., in preparation
Evaporation is the driving factor in isotopic fractionation
Transpiration and Percolation do not cause fractionation
Quantification between fractionating and non-fractionating losses
Conservation of mass and isotopes
ztvpif mmmmmm
ppiizzttvvff xxxxxx
Isotope Mass Balance
p; precipitation
t; transpiration
v; evaporation
z; percolation
i; f
f; final WC
i; initial WC
Total
j
j m
mx piTotal mmm with:
(e.g. Robertson et al. 2006, J. of Hydrol.)
Isotope Depths Profiles and Evaporation Line
-70
-60
-50
-40
-30
-20
-10
-10 -8 -6 -4 -2
Irrigated water Soil water percolated water MWL
y = 3.8x-18.6
R2 = 0.95
GM
WL
Comparison between different evaporation estimations:
(a) measured using hydrometric data and HYDRUS 1D, and
(b) calculated using isotope mass balance.
(a)
(b)
(a)
(b)
New way to estimate evaporation fluxes?!
Lysimeter A Lysimeter B
Evaporation E (mm) 19 77
Transpiration T (mm) 99 0
T/Etotal ratio 84% 0
Picture from Fairless, 2007, Nature
EIEIET ETES ES
SS SS
QR QR
QR QR
QS QS
P P
P P
Investigation of different compartments of the water
cycle using environmental isotopes
P=Q+E+dS/dt
Studying hillslope processes with
environmental isotopes
Spring A (Zipfeldobel)
Spring B (Zängerlehof II)
Investigation Period
0 , 0
0 , 4
0 , 8
1 , 2
1 , 6
2 3 . 1 0 . 9 9 2 9 . 1 0 . 9 9 0 4 . 1 1 . 9 9 1 0 . 1 1 . 9 9 1 6 . 1 1 . 9 9
D
is
ch
ar
ge
[l
/s
]
Z i p f e l d o b e l s p r i n g Z a e n g e r l e h o f I I s p r i n g
E v e n t 1 E v e n t 2 E v e n t 3
0
2
4
6
8
Pr
ec
ip
ita
tio
n
[m
m
]
Spring A Spring B
(Uhlenbrook, Didszun, Wenninger, 2008, Hydr. Sci. Journal)
Hydrochemical Dynamics: Dissolved Silica
Spring A
Spring B
40
60
80
100
120
140
24.10.99 26.10.99 28.10.99 30.10.99 01.11.99S
ta
nd
ar
di
ze
d
co
nc
en
tra
tio
ns
[%
]
0,2
0,6
1,0
1,4
D
is
ch
ar
ge
[l
/s
]
Silica Discharge
40
60
80
100
120
140
24.10.99 26.10.99 28.10.99 30.10.99 01.11.99S
ta
nd
ar
di
ze
d
co
nc
en
tra
tio
ns
[%
]
0,2
0,3
0,4
0,5
0,6
D
is
ch
ar
ge
[l
/s
]
Silica Discharge
Hydrochemical Dynamics: Deuterium
Spring A
Spring B
-100
-90
-80
-70
-60
-50
23.10.99 25.10.99 27.10.99 29.10.99 31.10.99
δ
D
v-
sm
ov
[‰
]
0,2
0,3
0,4
0,5
0,6
D
is
ch
ar
ge
[l
/s
]
Deuterium Precip. Discharge
-100
-90
-80
-70
-60
-50
23.10.99 25.10.99 27.10.99 29.10.99 31.10.99
δ
D
v-
sm
ov
[‰
]
0,2
0,6
1,0
1,4
1,8
D
is
ch
ar
ge
[l
/s
]
Spring Precip. Incr. Mean Discharge
0
0,4
0,8
1,2
1,6
24.10.99 26.10.99 28.10.99 30.10.99
D
is
ch
ar
ge
[l
/s
]
direct Runoff
deep
GW
Discharge
shallow
GW
Results of Hydrograph Separation at both
Springs/Hillslopes
Spring A
Spring B0,0
0,2
0,4
0,6
24.10.99 26.10.99 28.10.99 30.10.99 01.11.99
D
is
ch
ar
ge
[l
/s
]
direct Runoff
deep & shallow GW
Discharge
Example: Interpretation of Dominant Processes
at the Hillslope Scale
(Mc Donnell, 1990, WRR)
(Picture: P. Mosley)
pre-event water
event
water
Event (new) and
prevent (old) water!
“ … all nice, but we need
measurements at catchment
scale!”
(Keith J. Beven)
0
5
10
15
20
25
30
35
0 10 20 30 40 50 60
Time
St
re
am
D
is
ch
ar
ge
Quickflow, Stormflow
Baseflow
The bench mark paper:
Sklash & Farvolden, 1979: The role of ground-
water in storm runoff. Water Resources Research.
Tracer-based Hydrograph Separation in the
Weatherley Catchment, South Africa
Wenninger, Uhlenbrook, Lorentz, 2008, Hydr. Sci. Journal
Picture from Fa
