### "Memories of Flowing Water"

### "Memories of Flowing Water"

The Kasumigaura Basin Water Quality Improvement Project was launched in the 2020s, and the sewage treatment coverage rate reached over 90%. However, the inflow of untreated wastewater remains an issue, and the introduction of environmentally friendly agricultural chemicals developed by Sumitomo Chemical and new river monitoring technologies are being promoted [12:1†concat-all.txt].

In the Oyama River Water Quality Improvement Project, the introduction of water quality measurement technology and analysis of water quality data for the entire watershed have progressed since the 2010s. 2021 saw the implementation of the "Mikumagawa-Oyama River Flash Release Experiment," which confirmed the effectiveness of improving the ayu habitat by removing riverbed sediment before releasing young ayu [12:2†concat-all.txt 12:2†concat-all.txt].

In 1998, the Yahagi River in Aichi Prefecture became contaminated with cadmium and lead due to effluent from a metal smelting company. In addition, PCBs (polychlorinated biphenyls) discharged from chemical plants in rivers flowing into the Seto Inland Sea had an adverse effect on the ecosystem, and local residents demanded environmental improvements. With corporate responsibility being questioned, Sumitomo Metal Mining and other companies are involved and measures are being taken [12:5†concat-all.txt].

In the Oyama River in Hita City, Oita Prefecture, citizens' groups began to take action in 1973 to address the problem of declining water volume caused by dam pumping to power plants. 2001 saw a public-private partnership to reconstruct the dam, which tripled the water volume. 2020s saw the introduction of flash flood releases, which improved the river environment [12:9†]. [concat-all.txt].

The Thames in the United Kingdom was severely polluted in the 19th century by untreated sewage and industrial effluent, but cleanup projects since the 1950s have dramatically improved water quality; by 2016, the river had recovered to over 125 species of fish, and the Thames Barrier, a tourism resource and disaster prevention measure, is being Installation is underway [12:0†concat-all.txt].

Since the 1980s, rivers in major cities in China have become a serious environmental problem due to heavy metal and organic chemical pollution. The government is promoting the "South Water North Control Project" and developing policies to both secure water resources in urban areas and counter pollution [12:15†concat-all.txt].

In Lake Biwa, water quality is being improved through the use of biofilter technology. The environmental technology introduced by Hitachi Zosen has attracted particular attention, contributing to the reduction of chemical fertilizers and the preservation of the ecosystem [12:19†concat-all.txt].

--- [12:19†concat-all.txt

### Related information
- Improvement of water quality in Kasumigaura (Kasumigaura Environmental Science Center, Ibaraki Prefecture) [12:4†concat-all.txt].
- Water quality improvement and disaster prevention measures in the River Thames (Thames Barrier) [12:0†concat-all.txt].