Presentation by Marc Bierkens (Utrecht University) at the iMOD International User Day, during Delft Software Days - Edition 2017. Tuesday, 31 October 2017, Delft.

1. Groundwater in Global Hydrology
Marc F.P. Bierkens
Department of Physical Geography, Utrecht University, Utrecht, the Netherlands
Deltares, Utrecht, the Netherlands
Contributions from: Inge E.M. de Graaf , Ludovicus P.H. (Rens) van Beek and Yoshihide Wada

2. Livestock (Globe: 16 km3) Irrigation (Globe: 1376 km3)
Industry (Globe: 257 km3)Households (Globe: 199 km3)
million m3/year 2000
Global demand for surface water and groundwater
Wada et al., HESS, 2011

3. Livestock (Globe: 16 km3) Irrigation (Globe: 1376 km3)
Industry (Globe: 257 km3)Households (Globe: 199 km3)
million m3/year 2000
The human imprint: Global water consumption (potential abstraction – return flow)
Wada et al., HESS, 2011
Most water use for irrigation
17% of agricultural area is irrigated
Supplying 40% of the food production
40% of irrigation water use from
groundwater

4. The importance of groundwater
under climate change
Increased groundwater use and decline in California

5. Determining groundwater depletion
Volume based methods (change in volume stored):
1. From groundwater level observations
2. From simulations with local groundwater models including
abstractions
3. From gravity trends observed with the GRACE satellite
Flux based methods (depletion = in – out)
• Using a global hydrological model
• And statistics of water demand
Decreasing
accuracy
PCR-GLOBWB
0.5°
Decreasing global
data availability

6. Running integrated global hydrology and water resources models
Wada et al. (2016)
Flux based methods @UU
PCR-GLOBWB 2
at half degree
or 5 arcminutes

7. Simulation of global terrestrial water by the
integrated global hydrological model PCR-GLOBWB
1980-2010 daily time step (time in months) at 5 minutes resolution
Soil saturation 0-30 cm
Soil saturation 30-100 cm
River discharge (m3/s)
Fractional snow cover

8. 88
Country abstraction (km3/year 2000) Total water demand (million m3/year 2000)
Groundwater abstraction (million m3/year 2000)
Major users km3/2000
India 190
USA 115
China 97
Pakistan 55
Iran 53
Mexico 38
Saudi Arabia 21
Globe 734
Groundwater Abstraction
Surface Water Availability (m3/s)

9. 9
Globe N[15,225] + A[420] km3 Globe 734 km3
Groundwater abstraction – Groundwater recharge
All in million m3/year 2000
India 71 km3
Pakistan 37 km3
USA 32 km3
Iran 27 km3
China 22 km3
Saudi Arabia 15 km3
Mexico 11 km3
Globe 256 km3 Wada et al., GRL, 2012
Groundwater
depletion
India 56 km3
Pakistan 29 km3
USA 25 km3
Iran 21 km3
China 17 km3
Saudi Arabia 12 km3
Mexico 9 km3
Globe 204 km3

10. Groundwater footprint of major aquifers
Gleeson, et al., Nature, 2012.
Global groundwater footprint = 3.5 times the
global area of productive aquifers

11. Fan et al. (Science, 2013)
First global groundwater map: permeability e-folding depth calibrated to head data
Numerical scheme: relaxation
Global groundwater models

12. GRACE and groundwater depletion

13. Running PCR-GLOBWB coupled to MODFLOW at 5 arcminutes
De Graaf et al. (HESS, WRR)
Global Groundwater model @UU

14. Global hydrogeological model
at 1 km
Z(x) = 1
Z(x) = 0 Random average ln-thickness
(from US aquifers)
Fixed CV ln-thickness
(from US aquifers)
Log-normal
dustribution
within aquifer
1. Aquifer thickness

15. Global hydrogeological model
Upper aquifers
1. Aquifer thickness

16. Global hydrogeological model
2. Permeabilities

17. Global hydrogeological model
3. Transmissivity
>

18. Global hydrogeological model
4. Adding confining layers

19. Global hydrogeological model
4. Adding confining layers
Delineation of coastal
confining layers
Hydraulic properties of
confining layers
Fine-grained
unconsolidated
coarse-grained
unconsolidated

20. Global hydrogeological model
4. Steady state groundwater depth (no abstractions)
Confining layer or
unconfined aquifer

21. Global groundwater depletion
Effects of increased capture
200 km3/year
2000-2010

22. Groundwater depletion 1960-2010 in 4 major exploited aquifers
simulated with a global groundwater model; Inge de Graaf (PhD student)
How much groundwater is there still?

23. How much groundwater is there still?
Highly uncertain!
*static head in well
Time to 100 m depth* (economic limit?), 300 m depth
(technical limit?) much shorter: decades in certain areas!

24. How much groundwater is there still?
Volume within 100 head from surface
Volume within 300 head from surface
% change 1960-2010 % change 1960-2050

25. Necessary improvements
• Calibrating against heads and
GRACE data and isotopes
• Adding a percolation delay for
deep unsaturated zones
• Improving the hydrogeological
model with regional
information wherever
possible (repository) using
iMOD

26. Groundwater depletion
• 25%-40% of water abstraction from groundwater: 800-1500
km3/year;
• groundwater depletion: 100-300 km3/year.
• Projections towards 2050: groundwater depletion 200-400 km3/year.
• Global groundwater footprint = 3.5 times the global area of
productive aquifers
Groundwater dependency of food production
• 40% of food production from irrigation; 15% from groundwater; 4%
from non-renewable groundwater.
How much do we still have? Largely unknown
• Rough estimates: order 20-30% depletion major exploited aquifers
• Time to 90% order 200 years major exploited aquifers
• Time to 100 m or 300 m is much shorter
Conclusions thus far

27. Comparison of estimates
Konikow (2011):
140 km3/year (2000-2008)
Wada et al. (2012):
205 km3/year (year 2000)
Pohkrel et al. (2012):
455 km3/year (year 2000)

28. GRACE and groundwater depletion

29. How much groundwater is there still?

30. Mechanism of GWD
30
Natural situation: P > Epot
Recharge = P – E - Runoff

31. Mechanism of GWD
31
Natural situation: P < Epot

32. Mechanism of GWD
32
Q
Single well

33. Mechanism of GWD
33
Q QQ
Many wells

34. Mechanism of GWD
34
Q QQ
Many wells: finite aquifer

35. 35
Global Groundwater Depletion 1900-2100
Wada et al., GRL, 2012

36. 36

37. 37
Net Contribution from TWS Change to Sea Level 1900-2100
Wada et al., GRL, 2012