since the opening of the China-Kazakhstan oil pipeline in 2006 and the Central Asia-China natural gas pipeline in 2009.

### The "Silk Road Economic Belt" strategy may bring huge development space {#Sec19}

On September 17th, 2013, Xi Jinping, the Chinese president, stated during his visit to Kazakhstan that China and Kazakhstan shall adopt an innovative cooperation mode and construct the "Silk Road Economic Belt" together, to reinforce economic ties of Asian-European countries and expand the development space. This Economic Belt covers a vital Asian-Pacific region in the east, a Central Asia rich of resources in the middle, and developed European economic entities in the west. Countries along this Economic Belt have strong economic complementation and great potential for mutually beneficial cooperation. With attractive geopolitical interests, the "Silk Road Economic Belt"and ecosystem is very acute, and structural water shortage has become an important constraint against sustainable economic and social development of these countries (or regions). Under the centralized planning economic system of the Soviet Union, upstream countries of the Aral Sea basin (Kyrgyzstan and Tajikistan) and downstream countries (Uzbekistan and Kazakhstan) complement each other. Upstream countries offer water resources to downstream countries for farmland irrigation, while downstream countries supply energy resources (petroleum, natural gas, and coal resources) to upstream countries. After the collapse of the Soviet Union, conflicts of energy structure, agriculture mode, and economic structure between upstream and downstream countries became increasingly prominent. With population growth and the economic rehabilitation of five Central Asian countries, the imbalance of water supply and demand as well as water competition