Climate Change and Interdependencies with Water Security

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1 Faculty of Social Sciences, The University of Hong Kong HKU Engineering for Climate Extremes Partnership Workshop Climate Change and Interdependencies with Water Security Dr. Ji CHEN Department of Civil Engineering The University of Hong Kong 30 January 2018

2 To understand climate change Earth s climate varies naturally because of a variety of cosmological and geological processes Climate change refers to an additional, and relatively rapid, change induced by human actions The additional change several degrees C within a century will disrupt the foundations of life on Earth Ecosystems and life in general have evolved within a narrow band of climatic-environmental conditions Global warming and more frequent climate extremes have been widely reported by Intergovernmental Panel on Climate Change (IPCC, 2013). If a small change in climate will cause a dramatic change in hydrological cycle; it is expected that the frequency of occurrences of weather and hydrological extremes (e.g., super cold wave, super hot wave, super typhoons, super heavy rainstorms, super floods, and super droughts) will be increased along with climate change in the near future We need more research to explore the mechanism of climate change and the related influences A report by the Climate Change Science Program and the Subcommittee on Global Change Research. A supplement to the President's Fiscal Years 2004 and 2005 Budget. Published 2004

3 To project future climate change In 2000, the IPCC Special Report on Emissions Scenarios (IPCC SRES). The SRES team defined FOUR narrative storylines, labeled A1, A2, B1 and B2, describing the relationships between the forces driving greenhouse gas and aerosol emissions and their evolution during the 21st century for large world regions and globally Representative Concentration Pathways (RCPs) are four greenhouse gas concentration (not emissions) trajectories adopted by the IPCC for its fifth Assessment Report (AR5) in They describe four possible climate futures, all of which are considered possible depending on how much greenhouse gases are emitted in the years to come. The four RCPs, RCP2.6, RCP4.5, RCP6, and RCP8.5, are named after a possible range of radiative forcing values in the year 2100 relative to pre-industrial values (+2.6, +4.5, +6.0, and +8.5 W/m 2, respectively). (from IPCC WMO website)

4 To understand the global situation of climate extremes One of the major concerns with a potential change in climate is that an increase in extreme events will occur. For example, changes in total precipitation are amplified at the tails, and changes in some temperature extremes have been observed (Easterling et al., 2000) Climate change will bring greater variation in more frequent weather and climate extremes, and an increasing number of areas will face growing water scarcity by 2050, especially in lower income countries (World Water Council, 2015) The World Meteorological Organization (WMO) Commission for Climatology (CCl) decided to appoint a Rapporteur on climate extremes to keep an official, unbiased list of world weather extremes ü The goal of this database is to archive and verify extreme record events, such as the highest/lowest recorded temperatures and pressures on the Earth, the strongest winds, the greatest precipitation (over different time intervals) as well as the records involving the world's most destructive storms, hurricanes and tornadoes ü A data base is hosted by the Arizona State University (ASU) in USA and can be accessed at a dedicated WMO-CCl/ASU web site (

5 Climate extremes (National Climate Assessment) Heat Waves: ü periods of abnormally hot weather lasting days to weeks ü climate change has increased the probability of heat Drought: ü more occurrence of droughts due to global warming ü intensity of droughts would be extremely enhanced Heavy Downpours: ü increasing especially over the last several decades Floods: ü urban flooding, river flooding, coastal flooding, Hurricanes

6 Droughts all over the world Top Climate Change Concerns by Region Region Droughts or water shortages Severe weather, like floods or intense storms Long periods of unusually hot weather Rising sea levels Latin America 59% 21% 12% 5% Africa 59% 18% 16% 3% U.S. 50% 16% 11% 17% Asia /Pacific Middle East 41% 34% 13% 6% 38% 24% 19% 5% Europe 35% 27% 8% 15% Global 44% 25% 14% 6% ( (

7 To understand the situation of climate extremes in South China it was found that before 1984, the Tmin increased slightly and after that the variable has increased noticeably; it was observed that after 1984 the urbanization influence on climate was significant over the study area before 1984, the Tmax decreased, and after that the variable increased; the urbanization influence on the Tmax is negligible land use in 1980 and 21 stations land use in 2000 and 17 grids

8 Study of Impacts of Climate Change on Hydrological Processes in the Pearl River The Pearl River basin, the river network and streamflow gauge stations. The natural shape of the basin over the digital elevation map. The grid cells at 1 1 spatial resolution of the basin with the river routing direction.

9 Annual precipitation in the East River basin projected by 16 GCMs for A2, B1 and A1B scenarios during the period of A2 Historical Obs Model upper range Model lower range Modle Avg B1 A1B Precipitation (mm/year) Year Year Year

10 Differences between the future runoff and historical runoff ( ) for A1B, A2 and B1 scenarios during the three time domains, , and over the Pearl River basin

11 Droughts in HK: 1963 Drought 1963 Drought: Industrial loss HK$700 Million (People s daily) Ø 1-in-100 year drought in 1963 had highly destructive effects on water supply. Ø Water supplied only once every four days for four hours during 06/01/ /28/ Moderate dryness (-1.00 ~ -1.49): 12% Severe dryness (-1.50 ~ -1.99): 4% Extreme dryness (-2.00~ ): 2% ( 1.0 SPI drought 2011 drought month SPI in HK during drought / / / / / / / / / / / / / / /01

12 Droughts in South China and 2011 Drought in HK The drought disasters in South China in recent 60 years Year HK drought If the annual supply ceiling of 820 mcm had been lowered, Hong Kong might have inadequate fresh water supply in 2011 and might need to impose water rationing, which would seriously affect people's livelihood and the economy Hon Dennis Kwok in 2014 Adopted from HKSAR Water Supplies Department (WSD) ( Guangdong suffered severe droughts but still ensured water supply in HK in ( 75% 68% 76% 73% 89% Upper limit

13 Water supply in HK Dongshen-HK project: Ø80% of total fresh water consumption Ø Most 1.1 billion m 3 /yr mcm Hong Kong Total Water Consumption East River Water Supply Hong Kong Water Consumption & the East River Water WSD

14 Water supply in HK Tseung Kwan O Desalination Plant project (future): HK$ 8 billion Ø Provide 5% (up to 10%) of HK s fresh water demand, serving as a safe water source under extreme climate change Ø Supply 135,000 m 3 /d à270,000 m 3 /d by plan Ø About 30% more expensive than that by the East River Supply (WSD) (WSD)

15 Shi et al. (2018) developed a new method and a new index (SEDI) for identifying socioeconomic drought events under climate change To identify climate extremes (drought events) Cumulative water deficit Water deficit Drought duration Water shortage Ø comprehensively evaluating the impacts of both water shortage and drought duration Ø Considering the gap between water supply and water demand, streamflow is adopted as the principal input

16 The required water supply to meet the regional water demand is estimated using a five-stage water demand projection model proposed by Chen et al. (2015) Future water demand under three scenarios

17 Future drought analysis under 52 datasets ü 16 AR4 GCMs: SRES A2/A1B/B1, ü 1 AR5 GCM: RCP 2.6/4.5/6.0/8.5,

18 Impact of reservoir operation

19 To realize the sustainable development Chen et al. (2016) addressed the question if the construction of large dams should continue through a study of some key global socioeconomic data (population and water, food, and energy consumption) and the vital role of large dams in sustaining societies

20 (A) Global map of 2815 large dams (related reservoirs and hydropower stations) developed from 1900 to 2010; (B) The number of completed large dams per year and the accumulated reservoir capacity; (C) The dams classified by their main use in percent) (Chen et al., 2016)

21 The number of large dams completed in different periods Projections of population growth, water, food and energy consumption, and dam development for Ways to realize the sustainable development (Chen et al., 2016) to reduce the consumption, and to increase the production water resource conservation projects (e.g., dams) would be effective comprehensive evaluation of negative effects should be made before water projects are implemented

22 The University of Hong Kong