Upstream-downstream relationships

The water quality profile of the Lake Biwa-Yodo River-Osaka Bay system is quite complicated because there are many different kinds of upstream-downstream relationships. The most obvious relationship is between Lake Biwa, with extensive watershed development, upstream and the great metropolitan region downstream. In the upstream Lake Biwa watershed, infrastructure development through the LBCDP has literally transformed water-use practices over recent decades, in that the new infrastructure for water intake and transmission has made the lake water much more attractive than river water or groundwater because of its abundance, stability, and good quality. Nearly 80 per cent of municipal and agricultural water supplies now come from the lake and nearly all of it is returned to the lake, either with treatment (mostly in the case of municipal supply) or without treatment (mostly in the case of agricultural return flow).

There are other more localized upstream-downstream relationships throughout the Lake Biwa-Yodo River system. For example, there are many problematic relationships between upstream waste-water effluent discharge points and downstream water intake points, particularly along the middle and lower stretches of the Yodo River. Within the short stretch of 30 km or so between the Hirakata confluence points of two major tributary rivers of Yodo River and the river mouth at the Osaka Bay inlet, there is a concentration of discharge and intake points (see fig. 3.7). Upstream of some major water intake points, there are treatment plants discharging wastewater, sometimes in large quantities, as well as streams and channels discharging contaminated water from areas undergoing extensive urban development. Obviously the water withdrawn for treatment must undergo an extensive purification process before being distributed for consumption.

This upstream-downstream relationship may be examined in more detail in terms of the institutional and political context in two cases, the first involving the Shiga Prefecture and downstream governments as a whole, and the second involving Kyoto and Osaka.

In the first case, the conflict is between downstream expectations and the upstream mandate. To put it simply, the downstream local governments require (as they may be entitled to because of their financial contribution to the LBCDP) that the upstream Shiga Prefecture should keep the lake water as clean as possible. The quality of water the downstream users get is greatly dependent on the quality of the Lake Biwa water. For the Shiga Prefecture, on the other hand, keeping the lake water clean is more a mandate than an obligation, since the lake was originally clean and for centuries the prefecture has been fostering this great natural asset. The mandate, however, does not mean that the prefecture can pay to maintain or restore the quality of the lake water, which leads naturally to the thinking that the financial burden has to be shouldered by others as well, including and especially the downstream users. However, it is difficult to decide how clean is clean enough and who is to pay how much to get the lake water to a desirable quality. The LBCDP expenditure on environmental conservation has not fulfilled the mandate, in the sense that the costs expended through the LBCDP arrangement, which includes national and downstream government contributions, have been far from realizing a clean lake.

1 Kuzuha (Osaka City)
2 Isosliima (Osaka Pref.)
3 Isoshima (Hirakata City)
4 Koya (Neyagawa City)
5 Niwakubo (Osaka City)
6 Niwakubo (Osaka City) Niwakubo (Osaka Pref.)
7 Niwakubo (Osaka Pref.)
8 Hitotsuya (Osaka Pref.) Hitotsuya (Osaka City) Hitotsuya (Amagasaki City)
9 Daido (Hanshin Corp.)
10 Kunijima (Amagasaki City)
11 Kunijima (Osaka City)
12 Kunijima (Hanshin Corp.)
Fig. 3.7 Water supply intakes and wastewater effluent discharge points along the Lake Biwa-Yodo River watercourse (Note: not to scale. Source: based on figure in Osaka-fu Suido-bu Suishitu Shikenjyo, 1995, p. 4)

The second case involves an interesting but difficult issue regarding the Yodo River water quality between Kyoto, upstream, and Osaka, downstream. For the Osaka water suppliers, it is crucial that the quality of the Yodo River be kept reasonably high (at least to the level of acceptable raw water quality, both technically and psychologically). Otherwise, not only does the cost of treating water become prohibitively expensive, but there is a strong psychological impact on Osaka citizens if they think that their raw water is heavily contaminated by Kyoto wastewater. Osaka already expends great effort to treat its raw water because the lake water and the water in the tributary rivers to the Yodo River upstream of the Kyoto wastewater discharges are already significantly problematic. The lake water is eutrophic and the river water is polluted by urban and agricultural discharges further upstream. For Kyoto, on the other hand, it is important to keep the quality of effluent discharges free of residual pollution over and above the level the downstream water users find acceptable, while keeping the cost of treatment reasonable. The downstream water supply systems have been asking Kyoto City to reduce its pollution impact further.⁴