Survey of Energy Resources 2007
Hydropower Country Notes
A high proportion of Japan's large potential for hydro generation has already been harnessed. Hydropower & Dams World Atlas 2006 (HDWA) quotes its gross theoretical capability as about 718 TWh/yr, of which 136 TWh is regarded as technically exploitable and 114 TWh as economically exploitable. Hydro generation (including pumped storage output) amounted to some 86.5 TWh, representing nearly 8.5% of Japan's electricity.
The Japanese WEC Member Committee reports that 745 MW of conventional hydro capacity was under construction in 2005. Most of the sites suitable for the installation of large-scale conventional hydroelectric plants have now been developed. The great majority of the larger hydro projects presently under construction or planned in Japan are pumped-storage schemes. HDWA reported that 7 520 MW of pumped-storage was under construction.
The technically exploitable capability for small-scale hydro developments is reported by the Japanese Member Committee to be 47 TWh/yr, a relatively high proportion (34%) of the total hydro level. Developed small-hydro capacity at end-2005 was about 3.5 GW, equivalent to 12.5% of total hydro capacity. Capacity planned for construction totalled 106 MW, with a probable annual generation of 478 GWh.