Emergy evaluation of the natural value of water resources in Chinese rivers.

Emergy theory and method were used to evaluate the economy of China and the contributions of water resources in Chinese rivers to the real wealth of the Chinese economy. The water cycle and energy conversion were reviewed, and an emergy method for evaluating the natural value of water resources in a river watershed was developed. The indices for China calculated from the emergy evaluation were close to those of developing countries. Despite a small surplus in its balance of payments, China had a net emergy loss from its trade in 2002. The efficiency of Chinese natural resource use was still not high and did not match its economic growth rate. Furthermore, the Chinese economy placed a stress on its ecological environment and natural resources. Several indices of Chinese rivers from the emergy evaluation were close to those of average global river water. The main average indices of Chinese rivers were transformity (4.17 x 10(4) sej/J), emergy per volume (2.05 x 10(11) sej/m(3)), and emdollar per volume (0.06 $/m(3)). The total value of all the rivers' water made up 13.0% of the GDP of China in 2002, and that of water consumption accounted for 2.1%. The value of the water resources in the Haiheluanhe River (11.39 x 10(4) sej/J) was the highest, followed by the Yellow River (10.27 x 10(4) sej/J), while the rivers in Southwest China had the lowest values (2.92 x 10(4) sej/J).