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Flood Risk in a Changing Environment Qiuhong Tang Institute of - - PowerPoint PPT Presentation
Flood Risk in a Changing Environment Qiuhong Tang Institute of - - PowerPoint PPT Presentation
Global Change of Hydrology and Flood Risk in a Changing Environment Qiuhong Tang Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences Global Flood Partnership Conference 2019 11-13 June 2019
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Water Related Hazards
Emerging challenges of water related hazard require understanding the global water system and the natural and human-induced factors that influencing the water system. 2012/Beijing Over 90% natural hazards are water related, including drought and flood (United Nations Environment Programme).
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Global Water System
Humanity has become an important driving force of changes to the Earth’s hydrosphere and hydro-hazards.
Climate extremes Hydrological extremes
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Global Change Hydrology
Global Change Hydrology, an emerging discipline representing an evolution of hydrological sciences towards the linkage with global environmental change for understanding and quantifying the human fingerprint in the global water system.
Global Change Hydrological Sciences
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Scales in Hydrology
Global Change Hydrology can be across scales.
Anne Van Loon, 2015
Global
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- 1. How to depict the broad array of
human-induced factors in a human-water model?
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Bucket Model
It considers the impact of human-induced climate change.
Tang and Oki, 2016. Terrestrial Water Cycle and Climate Change, AGU Geophysical Monograph
Hydrological model
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Tang 2006.
Land Surface Model (LSM)
Vegetation Soil Snow Permafrost Runoff
It considers the impact of changes in underlying surface (including vegetation, snow, permafrost)
Land cover and land use change
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LSM with water management
1) Water demands
Wilting Point Targeted Soil Moisture Level Requirement
Non-Irrigated Irrigated 1.0 IF IF: Irrigation fraction
Irrigation Groundwater withdrawals
Tang, JHM 2007, J Climate 2008; Leng et al. 2014
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LSM with water management
Liu et al. 2016
Reservoir model
2) Water supply
It considers the impacts of water management.
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The Distributed Biosphere-Hydrological (DBH) model
Tang et al. JHM 2007.
SVAT scheme Mass/Energy
Photosynthesis
CO2 Hydrologic scheme Human activity Nontraditional data sources Climate model
Snow melt Chemical tracers
The model is a coupled human-water model that can represent most major human-induced factors that influencing the terrestrial water cycle.
Human Water Use (Irrigation) SiB2 Simple Biosphere Model Climate Change
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- 2. How to separate human and climate
impacts on the hydrological cycle?
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Yellow River run dry in the 1990s
Source: YRC; Yang et al. 2004
Drying days (zero low)
Huang et al. 2009
Red -crowned Crane North China Plain
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What factors contribute to the drying?
Change in Temperature Change in Precipitation
Source: Tang et al. 2008
Candidate Factors
- Climatic Changes
- Water withdrawals
- Vegetation changes
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Model settings
Photo credit: Sina, Hudong wiki, Yellowriver.gov.cn
DBH enables direct comparisons with the managed flow, rather than the ‘naturalized’ flow.
794,712 km2
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Effects of irrigation
TNH LZ QTX TDG LM SMXHYK LJ
Evaporation increases
2.1 6.9 10.5 22 0 AVG ID IF3 MAX MIN
Surface temperature decreases
- 0.1 -0.32 -0.4 0 -1.6
AVG ID IF3 MAX MIN Averaged (AVG) In Irrigation Districts (ID) Irrigated Fraction>0.3(IF3) MAXimum MINimum
TNH LZ QTX TDG LM SMX HYK 500 1000 1500 2000 2500
Discharge along river (m
3/s)
Observed Case 1 Case 2 Case 3
Case 2_ No irrigation Case 3_ With irrigation
60% 40%
Observed With Irrigation Without Irrigation Source: Tang et al. 2007
From upstream to downstream
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Major drivers contributing to the drying
Upper Reaches Middle Reaches Lower Reaches
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- 3. How to assess water-related risks and
build resilience?
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Climate change impact assessment
Climate Change Scenarios (RCPs) Assessment Model (DBH) Socio-economic Change Scenarios (SSPs) Impacts on water, agriculture, …
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Climate Change Impacts
Schewe et al. PNAS 2014 Elliott et al. PNAS 2014
Relative change in annual discharge at 2 oC compared with present day, under RCP8.5. Median potential end-of- century renewable water abundance/deficiency in average cubic kilometers per year under RCP 8.5
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Risks at different sectors
Identified areas with high risk.
Liu et al.; Yin et al.
Hydropower Crop yield Heatwave Ecosystem shift
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Risk atlas under climate change
Tang & Ge (Eds) 2018
Map license: JS-(2016)01-143
With the risk atlas, scientific knowledge can be translated to policy and management practices.
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Flood Risk in a Changing Environment
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Projected change in flood frequency. Multi-model median return period (years) in 21C for discharge corresponding to the 20C 100-year flood.
Increasing flood frequency under climate change
Hirabayashi et al. 2013
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A large portion of people lives in flood- prone area
Europe
Managed surface
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Modeling with flood control measures
The Baiyangdian Lake Basin The Xiong’an New Area
Established in April 2017, the Xiong’an area is located about 100 km southwest
- f Beijing. Its main function is to serve
as a development hub for the Beijing- Tianjin-Hebei economic triangle. Dams at upper reaches Lake Dikes City The Lake
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Experimental design
- Exp 1: Flood risk of a historical 50-year flood (the August
1963 flood)
- Exp 2: Present flood risk, using the same historical 50-
year flood with the flood control works
- Exp 3: A future 50-year flood with the heightened dike
and reservoirs The historical 50-year design storm was estimated based on the historical observations. The future 50-year design storm was estimated using the bias- corrected climate data from five general circulation models (GCMs) (HadGEM2-ES, GFDL-ESM2M, IPSLCM5A-LR, MIROC-ESM-CHEM, and NorESM1-M) under the RCP8.5 scenario from ISI-MIP.
Wang et al. HSJ 2019 accepted
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50-year storms
The 50-year design storm for the historical (1952-2010) and future (2032-2090) periods.
311 mm 379 mm
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50-year floods
The 50-year design flood into the lake for the historical (1952-2010) and future (2032-2090) periods.
Without Reservoirs With Reservoirs
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Results: inundation area
(a) Exp 1: historical run (b) Exp 2: present run with flood control works (c) Exp 3: future run with flood control works
The Lake The Lake The Lake
(a) (b) (c)
Wang et al. HSJ 2019 accepted
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Flood risk with flood control measures at Haihe River Basin, August 1963 flood
Actual inundation area Assumed inundation area with flood control works
Beijing Beijing
North China Plain North China Plain
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Take home message
- A new discipline of Global Change Hydrology
emerges.
- Understanding human-induced impacts to the
global water system is the key mission of Global Change Hydrology
- Considerable advances have been made in the
past, but more efforts and collaborations are required in order to understand the risks under changing environment and to shape the future of Global Change Hydrology.
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