A global water scarcity assessment
under Shared Socio-economicPathways
Hanasaki, N., Fujimori, S., Yamamoto, T.,
Yoshikawa, S., Masaki, Y., Hijioka, Y.,Kainuma, M., Kanamori, Y., Masui, T.,
Takahashi, K., and Kanae, S

Outline
Two papers were submitted to Hydrology and Earth System Sciences.
Hanasaki, N., Fujimori, S., Yamamoto, T., Yoshikawa, S., Masaki, Y., Hijioka, Y., Kainuma, M.,

A global water scarcity
assessment under Shared Socio-economic Pathways:
Part 1 Water use, Hydrol. Earth Syst. Sci., 2012.
Kanamori, Y., Masui, T., Takahashi, K., and Kanae, S.:

Hanasaki, N., Fujimori, S., Yamamoto, T., Yoshikawa, S., Masaki, Y., Hijioka, Y., Kainuma, M.,

A global water scarcity
assessment under Shared Socio-economic Pathways:
Part 2 Water availability and scarcity, Hydrol. Earth Syst. Sci., 2012.
Kanamori, Y., Masui, T., Takahashi, K., and Kanae, S.:

Draft papers are available (hard/soft copy) .

Highlights of Part1

Shared Socio-economic Pathways

SSPs: New socio-economic scenarios for global change study (post SRES)
SSP

Description

SSP1

Sustainability

SSP2

Middle of the Road

SSP3

Fragmentation

SSP4

Inequity

SSP5

Conventional Development

Similar to SRES, major socio-economic factors are quantitatively available
GDP (global total)

Population

Electricity production

Highlights of Part1

How people use water in each SSP?

Almost no description on water use in qualitative/narrative scenarios of SSPs
 Tried to develop a water use scenario COMPATIBLE with SSPs.
1. Developed simple (but robust) models on water use
IndustrialWater = Electricity × intensity

Scenario-dependent parameterQuantitative scenarios from SSPs

2. Developed THREE parameters for each model
INDEPENDENTLY from SSPs
Ex: Scenarios on industrial water intensity

Low efficiency
Mid efficiency
High efficiency
Rate historically observedin China/Thailand, Japan, and Israel

Highlights of Part1

How people use water in each SSP?

3. Linked three parameters and five SSPs focusing on narrative scenarios
SSP

Description

Technological change

SSP1

Sustainability

Rapid

SSP2

Middle of the Road

Moderate

SSP3

Fragmentation

Slow

SSP4

Inequity

Rapid/Slow

SSP5

Conventional Development

Rapid

IndustrialWater= Electricity × intensity

Low Eff
Mid Eff
High Eff

Highlights of Part1

Water use scenarios

Global total industrial water withdrawal

Change in industrial water withdrawal (2055 - 2000)

Highlights of Part1

Water use scenarios

Agricultural scenarios: Irrigation area

Industrial water withdrawal scenarios

Domestic water withdrawal scenarios

Crop intensity

Irrigation efficiency

Highlights of Part2

Is water available?
In Part 1 “potential water demand” was projected.
 Investigated the projected amount of water is hydrologically available.
What would be the future climate?
Scenario matrix

GCMMIROC-ESM-CHEM
HadGEM2 ESM
GFDL ESM2M
Time
1971-2000 (base period)
2011-2040
2041-2070
2071-2100

Highlights of Part2

Global water resources model H08
1. High spatial resolution (0.5°×0.5°)
2. High temporal resolution (daily)
3. Interaction between natural water cycle
and human activities

0.5°×0.5°
0.5°
67,420 cells
Regional simulation(e.g. Chao Phraya River)

HumanNature

Highlights of Part2

How can we know “water scarcity”

Method used in this study
Water withdrawal simulation- Withdraw from river- Daily interval- Rivers can be depleted,and withdrawal can fall
below demand

365

CWD =

∑ withdrawal

DOY =1365∑ demand

DOY =1

Water scarcity: CWD<50%

demandDOYavailability

deficit
DOYwithdrawal
JanDecHighlights of Part2

Water scarcity assessment

Change in CWD ratio
Stress increases including regions
mean annual runoff increases
 Climate policy has limited effectfor overall structure of water scarcity?
Stressed population
Population living in grid cells with thecondition of CWD < 50%Summary
Developed water use scenario compatible with SSPs.
Assessed water availability and use globally.
As far as we know, this is the first such study.
Two papers will be soon available online as discussion paper.
 During Open Discussion period, anyone can comment to these paper.
Next steps- Adaptation options- Working together with AIM/CGE
Next steps with YOUR help
- Better water use scenario (historical data, evaluating technical feasibility)- Further nexus (mitigation, LCS, land use, agriculture studies, and more)

Highlights of Part2

Why don’t you use WWR index?

Conventional method

AnnualWithdrawal
WWR =AnnualRiverDischargeAnnual river discharge change Increases in many parts of the world

Water scarcity: WWR>40%
Sometimes misleading results: where mean annual runoff increases,
WWR automatically decreases (indicating water scarcity is alleviated)
Runoff change

WWR change

Highlights of Part2

Climate policy has only little effect?

Figure 15 Region-wise total global population living in grid cells where CWD <0.5. The bars in left and right show the results of no climate policy and withclimate policy respectively.

Figure 16 Percentage of global population living in grid cells categorized as
Significant Degradation (ΔCWD<-0.05, red), Moderate Degradation (0.05≤ΔCWD<0, orange), and Alleviation or no change (0≤ΔCWD, blue). Eachcategory was subdivided into three by the change in the CWD recorded asHighly Stressed (CWD<0.5, dark), Moderately Stressed (0.5≤CWD<0.8, medium),and Less Stressed (0.8≤CWD, pale). The bars in left and right show the results of
no climate policy and with climate policy respectively.