Introduction

The Metropolitan Region of Kansai, which encompasses the cities of Kyoto, Osaka, and Kobe and surrounding municipalities in the Lake Biwa-Yodo River-Osaka Bay water system (see fig. 3.1),¹ has a population of some 18 million, of whom 14 million are served by the water of Lake Biwa (see table 3.1). The region is also characterized by major industrial developments, particularly along the Osaka Bay and Seto Inland Sea strip, as well as by extensive paddy agriculture in the Lake Biwa lowland areas. A complex web of water supply and wastewater networks serves and supports the region and its high level of municipal, industrial, and agricultural activities.

Fig. 3.1 The Lake Biwa-Yodo River-Osaka Bay area and part of Kansai Metropolitan Region

The Kansai Metropolitan Region has historically been dependent on Lake Biwa and the Yodo River for its water resource needs. The Biwa-Yodo system, therefore, had to be gradually transformed over the past century or so from a natural water system to a managed water system, through the installation of flood control facilities and the development of water resource management and control systems. The latest and the greatest of the sequence of engineering projects for water management is called the Lake Biwa Comprehensive Development Project (LBCDP), which was completed in March 1997 after 25 years. Thanks to the construction of a new weir and of levees around the lake, Lake Biwa water can now be discharged into the Yodo River in much greater quantities and with less variability to satisfy urban, industrial, and agricultural needs around and downstream of the lake at times of severe drought. Flooding problems can also be dealt with more easily now by resorting to newly installed pumping facilities and control gates for all of the rivers and irrigation channels that flow into Lake Biwa (Nakamura and Akiyama, 1991;Nakamura, 1995).

Table 3.1 Population served by Lake Biwa water, 1994

The Kansai Region, however, has still to deal with many unresolved problems of water management, particularly with respect to water quality. The improved water resource systems and infrastructures around Lake Biwa will promote further development of the watershed that will bring about environmental issues of greater magnitude and of a more complex nature. Water quality issues, which are by themselves inherently quite difficult to deal with owing to their growing complexity, are now intertwined with quantity issues, making the management of the Biwa-Yodo-Osaka Bay system extremely challenging both for the upstream and for the downstream regions.

This chapter will attempt to highlight some unique features of the water system in the region and to describe briefly its evolution as well as the implications for the current physical and institutional structures. It will also attempt to address the issues facing individual sub-regions and municipalities as well as the issues facing the entire water system within the broad context of water quality management, e.g. upstream-downstream relationships, the upgrading of the waste-water management system, the water quality of Osaka Bay, and control of Lake Biwa eutrophication, all with reference to such emerging concerns as sustainable water use, integrated watershed management, and the attainment of a sound ecosystem.