what do climate change models tell us? spainciwr.ucanr.edu/files/303456.pdf · the waapa model...

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The Botin Foundation and Rosenberg International Forum on Water PolicyUniversity of California Agricultural and Natural Resources

What do climate change models tell us?Spain

L. Garrote

UNIVERSIDAD POLITÉCNICA DE MADRID

Adapting Water Rights to Face Climate Change Impacts: A Comparison of California and SpainMadrid, Spain 25 April 2019

1

Introduction

• Projections of runoff– Studies made by Cedex

• Projections of water availability– WAAPA model, global for Europe and specific for Spain– Analysis of factors determining water availability

• Role of adaptation– Effect of policy on water availability

2

Studies of Cedex (2010, 2017) Methodology

Precipitation

Potential ET

Climate forcing Hydrologic model

Hydrologic projectionsActual ETRunoff Recharge

Study of 20106 projections SRES A26 projections SRES B2

Study of 20176 projections RCP4.56 projections RCP8.5

Results by basin

Comparison of studies by Cedex (2010-2017)

Similar results, slightly less reduction in runoff

Precipitation

Temperature

Actual ET

Runoff

Potential ET

Results of Cedex 2017

Large variability, strong reduction of runoff

Projected reduction of runoff (%)

Results of Cedex 2010-2017

Large variability, strong reduction of runoff (10% for RCP4-5)

Projected reduction of runoff (%)

Water availability

• Runoff is a proxy for changes in water availability

• But there are other factors…– Changes in variability– Water management: reliability, environmental flows, storage

• Simple model to estimate water availability– Streamflow, storage, demands and environmental flows– Analysis under climate change scenarios

7

WAAPA Model

WAAPA MODEL ALGORITHM

Reservoirs and

demands distributed in subbasin

One reservoir and one demand

per subbasin

GEOGRAPHICAL DATA

WAAPA MODEL DATA

WAAPA : Water Availability and Adaptation Policy Analysis

Potential Water Availability analysis

Performance(Volume Reliability)

Demand component dα

pαreq

Desir

edpe

rform

ance

pαα: Performance for dα

dαβamax

Maximum acceptable demand in the system

CONTROL SCENARIO

DEMAND-RELIABILITY CURVE

Presenter

Presentation Notes

Our main analysis tool is the demand reliability curve. The WAAPA model changes the demand in every point and computes supply reliability, producing the demand-reliability curve. If you specify a required reliability, you can define the maximum acceptable demand that can be supplied in the system.

PWA analysis under climate change

Reliability

Demand component dβ

pβreq

Desir

edpe

rform

ance

CONTROL SCENARIO

pββ: Performance for dβ

dαβ max

CLIMATECHANGE SCENARIO

Potential Water Availability change

DEMAND-RELIABILITY CURVE

Presenter

Presentation Notes

If we repeat the operation for the climate change scenario, we can estimate the water availability in the future scenario and the availability change.

Climate scenarios

11

100

1000

10000

100 1000 10000

ENSE

MBL

ES d

ata

(hm

3/yr

)

Cedex data (hm3/yr)

Comparison of streamflow data

A1BCTL-CRNMA1BCTL-ETHZA1BCTL-KNMIE1CTL-CRNM

100

1000

10000

100 1000 10000

A1B-

E1 2

070-

2100

(hm

3/yr

)

CTL 1960-1990 (hm3/yr)

Effect of Climate change on streamflow

A1B-LTCRNMA1B-LT-ETHZA1B-LT-KNMIE1-LT-CRNM

Effect of Climate change Validation with GRDC data

• Climate scenarios were taken from regional models in different projects: PRUDENCE, ENSEMBLES and CORDEX− 8 A2, 4 B2, 3 A1B, 5 RCP2, 5 RCP4, 5 RCP6, 5 RCP8− Time slices CTL: 1960-2000 FUTURE: 2070-2100

• Streamflow data were corrected for bias

• Significant reduction in most basins

Mod

elre

sults

(hm

3 /yr)

2010

-205

0 (h

m3 /y

r)

Analysis of European basinsC

HAN

GE

in R

UN

OFF

Scenario RC

P4.5C

HAN

GE

in A

VAIL

ABIL

ITY

Loop over 5 models

13

ANÁLISIS DE LA DISPONIBILIDAD (I)

13

Analysis of Uncertainty

Model uncertainty

Scenariouncertainty

Runoff: Model uncertainty larger than emission scenario uncertaintyAvailability: same level of uncertainty (storage)

Specific study of Mediterranean basinsSt

orag

e V

(km

3 )/ M

ean

Annu

alFl

owF

(km

3 /yr)

Mean Annual Flow F (km3/yr)/ Area S (km2)

15

Climate projections

15

Change in Mean Annual Flow

Cha

nge

in C

oeffi

cien

t of V

aria

tion

of A

nnua

l Flo

w

HIST

HISTPROJ

MAFMAFMAFMAF −

=∆HIST

HISTPROJ

CVCVCVCV −

=∆

16


16

Reduction in MAF and larger increase in CVStronger forcing in areas already exposed to water scarcity

Climate projections

17


17

Reduction in MAF and larger increase in CVStronger forcing in areas already exposed to water scarcity

Climate projections

18

Potential Water Availability

18

Potential Water Availability (km3/yr)

Prob

abili

ty o

f Exc

eeda

nce

Prob

abili

tyof

Non

-Exc

eeda

nce

19


19

Large uncertainty and significant reduction of PWAModel uncertainty larger than emission scenario uncertainty


20


20

Large uncertainty and significant reduction of PWAModel uncertainty larger than emission scenario uncertainty


21

Projected changes of MAF vs. PWA

21

Change in Mean Annual Flow

Cha

nge

in P

oten

tial W

ater

Ava

ilabi

lity

HIST

HISTPROJ

MAFMAFMAFMAF −

=∆HIST

HISTPROJ

PWAPWAPWAPWA −

=∆

22


22

Changes in MAF are a good proxy for changes in PWAWe found stronger dispersion in areas with high variability


23


23

Changes in MAF are a good proxy for changes in PWAWe found stronger dispersion in areas with high variability


24

Changes in MAF vs PWA

24

Change in Mean Annual Flow and Potential Water Availability

Prob

abili

ty o

f Exc

eeda

nce

HIST

HISTPROJ

PWAPWAPWAPWA −

=∆HIST

HISTPROJ

MAFMAFMAFMAF −

=∆

Prob

abili

tyof

Non

-Exc

eeda

nce

25


25

We found a range of behaviors:1 similar reduction; 2 less reduction PWA; 3 cross; 4 more reduction PWA


4

4

3

2

26


26

We found a range of behaviors:1 similar reduction; 2 less reduction PWA; 3 cross; 4 more reduction PWA


4

1 2

The role of adaptation

• Strong reductions of runoff and water availability

• Policy and management may modify availability– Water allocation to environmental flows– Investment in infrastructure or improved management– Governance: social arrangements to accept less reliability

• What is the impact of policy on water availability?– Simple analysis based on modelling framework

27

Adaptation options

Local management

Global management of

distribution

Global management of

supply and distribution

Every reservoir supplies local demands only

All reservoirs contribute to supply all demands, but reservoirs are operated

independently

All reservoirs are operated jointly to supply all demands

99%

95%

Reference Governance

Improved Governance

ReferenceManagement

ImprovedManagement

Every reservoir supplies local demands only

All reservoirs contribute to supply all demands

Water users do not share resources

Water users cooperate and share resources

POLICY: densification of water transport and distribution networks; enhancement of management capacity

POLICY: enhancement of legal framework for water sharing; capacity building to improve education of water users

28

Effect of adaptation: management and governance

29

Scenario RCP4.5

ReferenceManagemtGovernanMan&Gov

Demand

Duero Ebro

Tajo Guadalquivir

Adequate management and governance may compensate the reduction of availability

Effect of adaptation: Storage, Environmental Flow, Efficiency

• Policy target– Maintain acceptable reliability under climate change scenarios

• Main policy action– Demand reduction to maintain reliability under climate change

• Additional policy actions– Supply enhancement through increased reservoir storage– Increase water efficiency in urban use– Modify environmental flow conditions

30

Effect of adaptation: Storage, Environmental Flow, Efficiency

The range and effectivity of measures vary strongly across basins31

Conclusions

32

• Modeling tools– Model performance is very poor while describing the currently

observed features of hydrologic regime relevant for water availability– Model uncertainty is very wide, equal or greater than emission

scenario uncertainty. Is this of any use?

• Water availability projections– Climate change impacts on water availability are uncertain and

heterogeneous, but are expected to be strongly negative in Spain– Impacts are stronger in areas already affected by water scarcity

• Role of adaptation policy– Improved water management and water governance may

compensate adverse effects of climate on water availability– Effectiveness varies across basins, requiring local analyses

The Botin Foundation and Rosenberg International Forum on Water PolicyUniversity of California Agricultural and Natural Resources

What do climate change models tell us?Spain

L. Garrote

UNIVERSIDAD POLITÉCNICA DE MADRID

Adapting Water Rights to Face Climate Change Impacts: A Comparison of California and SpainMadrid, Spain 25 April 2019

33

what do climate change models tell us? spainciwr.ucanr.edu/files/303456.pdf · the waapa model...

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