Presentation by Marjolein Mens (Deltares, Netherlands) at the Hydrology Suite User Days (Day 1) - Hydrology Suite introduction and River Basin Management software (RIBASIM), during the Delft Software Days - Edition 2023 (DSD-INT 2023). Tuesday, 28 November 2023, Delft.

1. Marjolein Mens
Integrated modelling for
drought risk management in
the Netherlands

2. Fresh water is everywhere
2
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3. Different regions – different drought risk
3
Source: Alterra
PEAT
SAND
CLAY, SILT
LOAM,
LIMESTONE
Main soil types of the Netherlands
water supply from large
rivers and lakes
no water supply
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4. Impact of climate change on drought risk
• Groundwater level decline
• Increased intake from rivers and reservoirs
• Salt water intrusion
• Salinization of groundwater
• Reduced water quality
• Decline of river water levels
4
Sea level rise
Decreasing
river
discharge
Increasing
precipitation
deficit
Increasing
water use
Source: Deltaprogramme (2015)

5. Integrated modelling for droughts
Requirements:
• Combine various physical processes
− Groundwater
− Surface water
− Unsaturated zone (understanding plant growth)
− Water distribution and water balance
− Water quality (salt water intrusion, salt seepage, temperature)
• Include human influence (water users, water management)
• Allow coupling with impact modules
5
Source: Van Loon et al. (2016)
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6. Change in groundwater regime due to climate change
6
bron: Nationaal Water Model, 2019
(via www.klimaateffectatlas.nl)
zomer winter
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7. Change in water demand and water supply
Climate
change
longer
droughts
sea level
rise
irrigation
water level
polders
flushing
evaporation
low river
flows
glacier decline +
snow melt
7
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8. Sea level rise and salt water intrusion
Source: Research programme on Sea Level Rise (KPZSS)

9. Rhine and Meuse river catchments: wflow_sbm
9
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10. National-scale Hydrological
Model (LHM)
10
RIBASIM (in prep.)
MetaSWAP
MODFLOW

11. National SOBEK Model (hydrodynamics)
• Main surface water system (rivers, canals)
• Discharge, water levels
• Chloride concentration
• Water temperature
11
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12. Impact modules: from water shortage to welfare effect
Example agricultural drought risk:
Current Stoom2050
Million
euro
per
year
Continuing current policy
Alternative strategy 1
Alternative strategy 2
Source: Mens et al. (2021)

13. From software to decision support
MODFLOW RIBASIM
MetaSWAP D-Flow FM (Delft3D FM 1D2D)
Software
National-scale
models
Computational
framework
LHM
(hydrology)
LSM
(hydraulics)
decision
support
indicators
wflow
Societal impact tools
wflow_rhine
wflow_meuse
Input data

14. Dilemma’s / fit for purpose
14
Decision-maker’s requirements:
1. Provide relevant model outcomes
2. Accepted by stakeholders
3. Short calculation time
4. Limiting model development costs
Model-builder’s requirements:
1. Scientifically and technically valid
2. Representing system dynamics
3. Accessible (well-documented)
dilemma
Result:
Complex model with
long computation times
https://doi.org/10.1016/j.envsoft.2021.105100
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15. Way forward (1): need for quick scan tools
Fast exploration of many future scenario’s, but consistent with authority model(s)
Various options:
1. Meta-models by using simplified cause-effect relationships
15
meta-models or rapid assessment models
System dynamics models
(when feedbacks are important)
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16. Way forward (1): need for quick scan tools
Fast exploration of many future scenario’s, but consistent with authority model(s)
Various options:
1. Meta-models by using simplified cause-effect relationships
2. Complex models, but coarser (time and space) and/or focused on most important processes
16
QWAST
DM
water network
10d
water demand + inputs
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17. Way forward (2): coupling floods and droughts?
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• Many challenges - one system
• Hydrological processes play central role
• Yet: sectoral approaches exist
• Evaluation of measures is fragmented
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18. Current modelling strategy
18
Temporal resolution
hour day month
week
flood event drought episode
impact
T=10
T=100
urban areas
agriculture
ecosystems
urban
areas
agriculture
ecosystems subsidence
urban areas
agriculture
navigation
industry
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19. Key messages for integrated modelling
• Combined use of detailed models for in-depth insight, and fast models for exploration
− How to ensure consistency?
• Changing requirements:
− Combination of floods and droughts → one system, but different time scales and spatial scales
− More insight needed into biodiversity (ecosystem functioning) under changing conditions
• What does this mean for integrated modelling:
− Combining different hydrological processes: interaction groundwater and surface water
− Connecting hydrology with societal impact tools: smart postprocessing, data exchange
− Droughts AND floods: requires smart model coupling (either online or offline)
− Framework for consistency between complex and quick-scan
19
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