Impact of climate change on hydrological extremes in Belgium prof. dr. ir. Patrick Willems...

Impact of climate change on hydrological extremes in Belgium

prof. dr. ir. Patrick WillemsK.U.Leuven – Hydraulics Division

Hydrological climate change impact research for Belgium

• Waterbouwkundig Laboratorium : impacts on high and low flows

BelSPO: CCI-HYDRclimate change scenariosfor hydrological impact analysisincl. extremes

• INBO: impact on natureincl. comparison with KNMI’06 scenarios

• VMM:− impacts on floods (non-navigable rivers 1st

category)− update urban drainage design guidelines

• MIRA-S & NARA 2009

• BelSPO: SUDEM-CLI: interfacing climatology –hydrology – ecology

• EU-FP7: Theseus: correlation with storm surge and wave scenarios Belgian Coast

Based on simulation runs by global and regional climate models & IPCC SRES greenhouse gas emission scenarios till 2100

DMI 25 km

Climate change scenarios for Belgium

GCM

RCM

31 runs (A2,B2) & 26 runs (A1B) by 10 RCMs

17 runs by ECHAM5 (A1B)

IPCC AR4: 27 runs by 21 GCMs (A2, A1B, B1)

Greenhouse gas emission scenarios

IPCC SRES, 2001 & 2007:

• Validation regional climate model runs for control period (monthly temperature, 1961-1990):


• Increase in monthly temperature:

winter:+1.5 to +4°C

summer:+2 to +7°C


GCMs 1961-1990 : RCMs 1961-1990 :

GCMs 2071-2100 : RCMs 2071-2100 :

zomers droger

winters natter

Climate change scenarios for Belgium• Change in monthly precipitation:

• Change in monthly precipitation:

winter:up to +60%

: increase in winter

summer:a.l.a. -70%

: decrease in summer (lower no. of small rain storms)

no. wet days summer:

a.l.a. -50%


• Change in precipitation– Intensity increase for most extreme storms

most extreme storm in 2 years


• Change in precipitation– Intensity increase for most extreme storms

most extreme storm in 10 years


Historical climate trends for Belgium

• Historical trend analysis– DJF rainfall extremes Uccle (10 min -> seasonal) 1898 –2005:

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

year [-]

-50

-40

-30

-20

-10

0

10

20

30

ano

mal

y in

ext

rem

es [

%]

w inter, 10-year w indow

w inter, 15-year w indowlong-term average

approxim ate cyclic varia tions

cyclic varia tions p lus c lim ate change

clim ate change effect

Multidecadal Multidecadal climate oscillationclimate oscillation

Global warming Global warming impactimpact

0.95

1

1.05

1.1

1.15

1.2

1.25

1.3

1.35

1960 1970 1980 1990 2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100

Per

turb

atio

n f

acto

r

SHMI-MPI-A2

SHMI-MPI-B2

CNRM-DE6DMI-ECC-A2

DMI-ECC-B2CNRM-DE5

ICTP-A2HS2 / HS3 / CNRM-DC9

SHMI-HC-B2ETH / HS1

CNRM-DE7 / SHMI-HC22GKSS-A2

GKSS-sn-A2 / METNO-A2SHMI-HC-A2

ICTP-B2DMI25 / KNMI

METNO-B2

Control period(1960-1990)

Scenario period(2070-2100)

Regional climate model simulations

Historical trend 30 years blocksize

Historical trend 30 years blocksize: part c.c. increase

• Consistency check with historical trend analysis– Example: Winter (DJF), daily rainfall extremes:

High = Wet

Mean = Mild

Low = DryCurrent


• Regional differences– Rainfall change about 10% higher along the Belgian coast

More wet in winter:


High = WetMean = MildLow = Dry

• Regional differences– Rainfall change about 10% higher along the Belgian coast

Less dry in summer:


High = WetMean = MildLow = Dry

Statistical downscaling

Large Scale

Hydrological scale

Dynamical downscaling

Statistical downscaling

General Circulation Models

(GCMs)

Regional Climate Models

(RCMs)

150 – 300 km; seasonally – monthly

± 50 km; weekly - daily

± 25 km; daily

river catchment; hourly

Month i Month i Month i

Wet day frequencyperturbation

Wet day intensityperturbation

Combined perturbation

Time series

Time series

• Day -> hour (river), 10-min (sewer system)• Based on quantile perturbations:

– change in rain storm frequency and rain storm intensity– dependent on return period rainfall intensity, season, weather type, …

• Time horizons till 2030, 2050, …, 2100

Perturbation tool

High = Wet

Mean = Mild

Low = Dry

DailyHourly10min

Perturbation tool

• Preserves physical consistency (dependency) between seasons and variables (precipitation, temperature and ETo)

Day-Winter

0.4

0.6

0.8

1

1.2

1.4

0.8 1 1.2 1.4 1.6 1.8

Eto Perturbation [-]

Rain

fall

Pert

urb

ation [

-]

High Mean Low

Day-Summer

0.4

0.6

0.8

1

1.2

1.4

0.8 1 1.2 1.4 1.6 1.8

Eto Perturbation [-]

Rai

nfal

l Per

turb

atio

n [-

]

ETo change factor ETo change factor

Pre

cip.

cha

nge

fact

or

Pre

cip.

cha

nge

fact

or

Winter Summer

High Mean Low

Perturbation of rainfall series

• Change in rainfall IDF-relations:– Based on Uccle 10 min rainfall series 1898-2005:

1 month

1 year10 years

100 years

Return period:


• Change in rainfall IDF-relations:– Daily rainfall results, climate model runs:

1 month

1 year10 years

100 years

Return period:


• Change in rainfall IDF-relations:– 10 min downscaling results, climate model runs:

1 month

1 year10 years

Return period:

Climate change impact on urban drainage

• Change in rainfall IDF-relations:– High, mean and low climate scenarios:

10 years

1 year

1 month

100 years 50 years

2 years

2 months


• Change in rainfall IDF-relations:– Shift in return period high climate scenario:

Perturbation of “design” storms

• Change in rainfall IDF-relations:– Change in composite storms, example T = 2 years:

High

Mean

Low

Hydro-impact modelling

Rainfall, ETo

Rainfall-runoff

River hydrodynamics

Physico-chemical river water quality

NAM, PDM: conceptual

Spatially distributed:SCHEME (KMI/IRM), MIKE-SHEWetSpa (VUB)

MIKE11InfoWorks-RS + quasi 2D overstromingen

Spills

Calculation nodesnumerical scheme

Right floodplainLeft floodplain

Bridge over tributary(culvert + weir)

MAIN RIVER

TRIBUTARY

MIKE11 EcoLab

• Impact of climate scenarios on hourly runoff peaks:

Hydrological impacts

-40

-20

0

20

40

60

80

0.1 1 10 100

Terugkeerperiode (jaar)

vari

atie p

iekafa

voere

n (%

)) )

High Mean Low

rainfall-increase ETo-

increase

High Mean Low

• Impact of climate scenarios on hourly runoff peaks:


Demer.shp-74 - -71-70 - -56-55 - -44

-43 - -34-33 - -19

(-70%) - (-50%)(-49%) - (-30%)(-29%) - (-22%)(-21%) - (-13%)(-12%) - 0

(-14%) - (-13%)(-12%)(-11%) - (-9%)(-8%) - (-3%)(-2%) - 3%

01% - 22%23 %- 24%25 %- 32%33% - 37%

Low scenario, Runoff peaks

Mean scenario, Runoff peaks

High scenario, Runoff peaks

Climate 2100, Flanders

RUNOFF PEAKS

Demer.shp-74 - -71-70 - -56-55 - -44

-43 - -34-33 - -19

(-70%) - (-50%)(-49%) - (-30%)(-29%) - (-22%)(-21%) - (-13%)(-12%) - 0

(-14%) - (-13%)(-12%)(-11%) - (-9%)(-8%) - (-3%)(-2%) - 3%

01% - 22%23 %- 24%25 %- 32%33% - 37%





RUNOFF PEAKS

Change in flood risks is highly uncertain Runoff peaks due to rainfall/ETo change decrease in low

scenario and increase in high scenario (up to 35%) Major influence due to sea level rise (Scheldt tidal river)

CLIMAR

• Sea level rise:

+20cm to +2m


about 20cm past 100 years

• Flood map current climate:

T = 100 yearCurrent climate

Impacts on floods

T = 100 yearHigh scenario

• Flood map after climate scenarios:

Impacts on floods

High = Wet

• Impact of climate scenarios on low flows extremes:


Demer.shp-74 - -71-70 - -56-55 - -44

-43 - -34-33 - -19





LOW FLOW PEAKS

(-88%)(-87%) - (-68%)(-67%) - (-63%)(-62%) - (-55%)(-54%) - (-48%)

(-56%) - (-55%)(-54%) - (-52%)(-51%) - (-47%)(-46%) - (-40%)(-39%) - (-30%)

(-35%) - (-32%)(-31%) - (-24%)(-23%) - (-21%)(-20%) - (-15%)(-14%) - (-10%)

Low scenario

Mean scenario

High scenario

Demer.shp-74 - -71-70 - -56-55 - -44

-43 - -34-33 - -19





LOW FLOW PEAKS

(-88%)(-87%) - (-68%)(-67%) - (-63%)(-62%) - (-55%)(-54%) - (-48%)

(-56%) - (-55%)(-54%) - (-52%)(-51%) - (-47%)(-46%) - (-40%)(-39%) - (-30%)

(-35%) - (-32%)(-31%) - (-24%)(-23%) - (-21%)(-20%) - (-15%)(-14%) - (-10%)

Low scenario

Mean scenario

High scenario

Low flow risks increase significantly in all scenarios May increase problems rel. water quality, navigation, drinking

water production, irrigation, ecological state river valley, ...

Demer.shp-74 - -71-70 - -56-55 - -44

-43 - -34-33 - -19





LOW FLOW PEAKS

(-88%)(-87%) - (-68%)(-67%) - (-63%)(-62%) - (-55%)(-54%) - (-48%)

(-56%) - (-55%)(-54%) - (-52%)(-51%) - (-47%)(-46%) - (-40%)(-39%) - (-30%)

(-35%) - (-32%)(-31%) - (-24%)(-23%) - (-21%)(-20%) - (-15%)(-14%) - (-10%)

Low scenario

Mean scenario

High scenario

Demer.shp-74 - -71-70 - -56-55 - -44

-43 - -34-33 - -19





LOW FLOW PEAKS

(-88%)(-87%) - (-68%)(-67%) - (-63%)(-62%) - (-55%)(-54%) - (-48%)

(-56%) - (-55%)(-54%) - (-52%)(-51%) - (-47%)(-46%) - (-40%)(-39%) - (-30%)

(-35%) - (-32%)(-31%) - (-24%)(-23%) - (-21%)(-20%) - (-15%)(-14%) - (-10%)

Low scenario

Mean scenario

High scenario

• Drier summer climate can have severe impacts• Mean water availability in Flanders and Brussels is very

limited: 1480 m3/(person.year)– International standards: <2000 “zeer weinig”, <1000 “ernstig

watertekort”– Causes:

• High population density:– high urbanisation, pavements: increased surface runoff, decreased

infiltration– high drainage in agriculture– groundwater abstractions for drinking water supply (region of Waregem:

groundwater table levels >100m lower than natural conditions)• (in Scheldt basin): less than half of available water is due to local rainfall• strong dependency on neighbouring regions (The Netherlands: Meuse and canal

Gent-Terneuzen)



• Change in overflow frequencies storage + infiltration facilities:– Reservoir model:


• Change in overflow frequencies storage + infiltration facilities:– Change in storage capacity needed:

constant through-flow [l/(s.ha)]:

Return period overflow [years]:

0.5 1 2 5 10 20

50 +35% +18% +17% +29% +24% +33%

40 +25% +16% +17% +25% +31% +27%

30 +18% +13% +12% +30% +29% +25%

25 +18% +14% +12% +31% +25% +22%

20 +16% +18% +13% +27% +26% +21%

15 +17% +20% +11% +22% +22% +13%

10 +17% +20% +19% +20% +24% +17%

5 +13% +17% +17% +18% +24% +20%

2 +13% +14% +14% +15% +30% +18%

1 +9% +10% +10% +10%

Climate scenarios for Belgium till 2100:

Impact on water systems:– Winter season:

• Rainfall increase• ETo increase• Sea level rise

– Summer season:• Rainfall decrease• ETo increase• More intense convective summer storms

Unclear impact on inland river floods

Increase in low flow / water scarcity problems

Increase in sewer floods

Climate change impact on hydrology

Increase in coastal flood risks

Climate change impact on hydrology

For specific conditions of river basins in Flanders/Belgium:• Climate scenarios up to 2100:

– Evolution towards more droughts– Impact on flood risk along inland rivers unclear (<-> coast)– Increase in short-duration rainfall extremes

• But: climate scenarios not equal to predictions !– Evolve along with our knowledge and understanding– High uncertainties; part of the uncertainties not accounted for

• Adaptation measures ?– Use climate scenarios in water management planning !– Take high uncertainties into account !

“concept of risk = probability * consequences”“no regret” measures, “climate proof” investments design a flexible strategy (adaptable measures/investments)

Actions or adaptation measures

• See river basin and subbasin management plans• New Sigmaplan

– Geactualiseerd Sigmaplan: gecontroleerde overstromingsgebieden en natuurgebieden (1650 ha in 2030) en dijkverhogingen in steden en industriegebieden

• Prediction of and warning for flood risks:• Real-time prediction and warning system• Real-time regulation of reservoirs: more efficient use of available storage capacity

by model-predictive control algorithms

• Against drier summer climate:– Maximum upstream holding of rain water in infiltration facilities,

ditches, low-lying spaces, ...– Revision of regulations (vergunningen- en heffingenbeleid) and

water-pricing system (sturend waterprijzenbeleid: variabele tarieven voor drinkwater, progressieve tarieven naargelang verbruik)

– Reduction of water consumption, water loss, reuse of water (sensibilisering rationeel watergebruik)

– “Water-audit” for new or renovated buildings– Innovation programmes for water efficient industrial production and

irrigation


• Against increased temporal variability of rainfall: drier summers + increased short-duration rainfall extremes:– calls for more attention to (local) rain water management (also at

municipal level)– additional (upstream and local) rain water storage and infiltration

needs

• More small scale solutions (at large scale)• More important role to local water managers


Accept increased frequencies of “water in the streets” local scale measures can significantly reduce the damage (for same flood frequency)


More local upstream storage (local terrain depressions) combined effect: reduces sewer flood frequencies & rain water feeds groundwater table


Better integration of water management and spatial planning / urban design


Multiple functions to open spaces (e.g. parks) in the city:

FWO research project together with K.U.Leuven - ASRO

(PhD researchers Isabelle Putseys

& Christian Nolf)

Better integration of water management and ecological / nature management


Role of wetlands:

SUDEM-CLI cluster project for BelSPO

(cooperation with U.Antwerp – ECOBE)

Better integration of water management and agriculture


Avoid winter runoff (and erosion) and increase infiltration by “adapted” agricultural management practices:• groenbemesting• ploegrichting• bufferstroken naast rivier

• Improved cooperation between water managers and spatial planners / urban designers, managemers of green zones in the city (parks, playing gardens)

• Improved interlinking between:– Guidelines for design of urban drainage systems (code van goede

praktijk voor het ontwerp van rioleringssystemen)– “Watertoets”– Building regulations (gewestelijke stedenbouwkundige verordening;

andere stedenbouwkundige voorschriften)

Additional needs

More info

Research project CCI-HYDR on “Impact of climate change on hydrological extremes (peak and low flows)

along rivers (Scheldt and Meuse basins) and urban drainage systems in Belgium”

(for Belgian Science Policy Office):

http://www.kuleuven.be/hydr/CCI-HYDR

Impact studies: Instituut voor Natuur- en Bosonderzoek (INBO): http://http://www.inbo.be

Vlaamse Overheid: Waterbouwkundig Laboratorium: http://www.watlab.be Vlaamse Milieumaatschappij: http://www.milieurapport.be http://www.watertoets.be/publicaties

Impact of climate change on hydrological extremes in Belgium prof. dr. ir. Patrick Willems...

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