J-Power, Marubeni Corp. and JGC Corp. are among Japanese companies that signed agreements Friday to develop water and power projects in China and gain from increased demand in the fastest-growing major economy.

Electric Power Development Co., the official name of J-Power, will offer technology to China Power International Development Ltd. to increase fuel efficiency at coal-fired thermal generators, a document prepared by Japan's trade ministry and China's National Development and Reform Commission shows.

Japanese companies, faced with a shrinking population and stagnating demand at home, are seeking to tap China's appetite for improved water supply and more efficient power production. Friday's meeting is the third China-Japan environment forum since 2006, reflecting improved ties since Prime Minister Junichiro Koizumi left office in Tokyo two years ago.

Trading house Marubeni and JGC agreed with a Chinese partner to address water pollution at dams in China and ease water shortages, according to the document. The partners will seek joint water filtration projects in northern China, it said.