New Challenges for Water Security
Water-related disasters represent the most frequent and most damaging natural disasters affecting human society. Environmental changes, including climate change, population increase, rapid social and economic development, and impacts of human activities on land use, bring enormous challenges for water security to human society, which attract global attention and call for joint solution.
Affected by the southeast monsoon and special topography in China, annual precipitation varies from more than 2000mm to less than 20mm from southeast regions to northwest areas. The uneven spatial and temporal distribution of water resources brings serious water issues in China, where water-related disasters take about 74% of all natural disasters. The mean economic loss produced directly by floods has taken about 1.8% of GDP in same term since 1990, and meanwhile, the economic loss caused by droughts was about 1.0-2.0% of GDP in same term, depending on yearly precipitation. Therefore, water security is a bigger issue in China.
Under changing environments, water security becomes more serious in the word. The following trends have been observed in China. Firstly, it seemed that more frequent floods occurred in south regions, especially in the Pearl River, the Yangtze River, and the Huaihe River, and resulted in huge losses. For example, about 1562 people died and economic loss reached up to 200 billion Chinese Yuan( 1US$ is about 6.6 Chinese Yuan) due to the floods occurred in the Yangtze River in 1998. Moreover, the rising of sea-level with global warming, will reduce the defense ability against flood along coast areas. Secondly, the shortage and conflicts of water resources become more intense. In last 3 decades, the runoff of most north rivers declined markedly. For example, the annual amounts of surface water resources in the Yellow River and the Haihe River have reduced by 14.5% and 40.8% respectively since 1980 (compared with the time-series of 1950-1979). Thirdly, the extreme events present an increasing trend. It seemed that we had more urban storm floods in last 20 years. For instance, the heavy storm floods occurred in 2004, 2007, 2010, 2011 and 2012, in Beijing city. Especially, the storm flood happened in July 21, 2012, caused a mortality of 79 people. In addition, violent typhoons also display a trend of increasing both in number and intensity. All these changes will definitely bring us new challenges and crises on water security.
What Should We Do?
In response to these new challenges, it is necessary to fully understand the changes and their trends. We also need infrastructures with higher standards, such as more robust flood prevention engineering (river dykes, reservoirs, and flood retention basins), and powerful management system, including monitoring system, forecasting system and decision supporting system, to reduce the risk of floods and to ensure water supply.
by Professor Jianyun Zhang – GGCS resilience session speaker and panellist
President of the Nanjing Hydraulic Research Institute