Conserving water value for the long term
Japan is a land of extremes - its heavy rainfall no panacea for its periodic droughts. Steve Higham reports on the country's dam building programme and below, describes one city's approach to water conservation.
Thus, according to the Water Resources Development Public Corporation (WARDEC), established as a non-profit organisation in 1962 under government legislation, the country's heavy rainfall actually yields a value of less than one-fifth of the world average. Much of this drains to the sea and in the 1990s some areas were affected by serious drought. In 1994 low rainfall brought drought to the Kanto region, and the Chubu and Shikoku regions suffered as a result of the 1996 drought.
To meet this pressing water demand and to combat further threats of drought, WARDEC has implemented extensive development of seven major river systems, namely projects along the Tone, Ara, Toyo, Kiso, Yodo, Yoshino, and Chikugo rivers. Since its inception, the Corporation has completed and is operating 47 water resources development facilities - many of them huge - and is currently involved in 18 projects for the construction of facilities to supply water to the Kanto, Chubu, Kinki, Shikoku, and Northern Kyushu regions. A further two projects, the Kuribaragawa and Koishiwaragawa dams, are also being considered.
Under construction in the Tone and Ara river systems is the Tone Chuo canal, the Boso canal (Togane dam), the Hirakawa dam aimed at flood control and supply during severe droughts, the reconstruction of the Musashi canal for domestic and industrial water, the construction of the Kuribaragawa dam and the Takizawa dams.
Also in this basin is the Omoigawa development (at an estimated 1999 cost of ¥2,450 million) at the Nanma sam site and scheduled for completion in 2008. It will be a rockfill structure, 105m-high with a crest length of 545m. Active storage capacity amounts to some 100,000,000m3 and will create a reservoir with a 101,000,000m3 capacity. The project aims to maintain and regulate normal river functions (including emergency water supply during droughts).
Work in the Kiso and Toyo river systems includes the Aichi Canal Stage II project, the Tokuyama dam, reconstruction of the Kisogawa barrage to control salinity damage, the Toyogawa Canal Stage II project, and the Toyogawa Comprehensive Canal (Ohshima dam) project. This latter scheme is a concrete gravity dam, almost 70m-tall with a crest length of 160m. It will have an active storage capacity of 11,300,000m3 and will provide irrigation water in the Aichi and Shizuoka Prefectures.
The Tokuyama dam in this 255km3 catchment area is a large rockfill project. It will cost almost ¥15,000 million and when completed in 2007 will have a crest length 415m-long and 161m-high. It will have a volume of nearly 14,000,000m3. This is an interesting project with multipurpose aims: it will provide flood control, regulate river functions, provide 424,000kw of power, and provide water for industrial and domestic use for the prefectures of Gifu and Aichi.
Along the Yodo river system, work is continuing on the Niu and Kawakami dam projects, while along the Yoshino, one of Japan's three large rivers, test filling the reservoir is in progress at the Tomsato dam.
On the Chikugo river, WARDEC has four projects underway to provide water for agriculture for the Ryochiku Plain and lower Chikugo river as well as supplies for domestic and industrial use.
For the fiscal year 1999, the budget for the construction and management of
WARDEC's projects amounted to ¥365.1 billion, but who pays for it? Projects
are state-assisted - for example the government will contribute ¥70 billion
of the above ¥365.1 billion figure and a further ¥77.6 billion was provided
for by treasury loans and investments - but other funding comes from grants
for flood control, and state subsidies for the agricultural sector. Moreover,
the Corporation is able to proceed with large scale projects - dams are expensive
and require long implementation periods - without particular regard for cost
allocation since the projects' beneficiaries are required to refund construction
costs once they have been completed.