Promoting an Eco-Friendly Lifestyle to Protect Lake Teganuma--Efforts of Abiko City in Chiba Prefecture

JFS Newsletter No.33 (May 2005)
"Initiatives and Achievements of Local Governments in Japan" Article Series No.9

Located in the northwest of Chiba Prefecture, Abiko City occupies a narrow, east-west stretch bordered on the north by the Tonegawa River and on the south by Lake Teganuma. During the Edo Period (1603-1867), the city was a prosperous post town along the Mito Kaido, the main road from Tokyo (formerly called Edo) to Mito in Ibaraki Prefecture. During the Taisho Period (1912-1926), several well-known writers of the time, such as Saneatsu Mushanokoji and Naoya Shiga, moved to Abiko, fascinated with its beautiful landscape and natural environment.

Now its population is about 130,000. Since Abiko is about 40 kilometers away, or only a 35-minute ride by train, from central Tokyo, the city is increasingly functioning as a bedroom community for the Tokyo metropolitan area.

Lake Teganuma is a symbol of Abiko. It is well-known as a paradise for waterfowl, and the Abiko City has a Bird Museum near the lake. During spring and summer, Pacific Golden Plovers, Barn Swallows, and Great Reed Warblers migrate to this area, and in winter, as many as 2,000 migratory ducks use the lake as a resting site.

At the same time, Lake Teganuma has also been known for its disgraceful record of having been the most polluted lake in Japan for 27 consecutive years starting from 1974, when the then-Environment Agency (now the Ministry of the Environment) began nationwide surveys of lake and marsh water quality. Since fiscal 2001 Abiko City has made Lake Teganuma the focus of a municipal promotion campaign on the theme of "Birds and people living in harmony in Abiko, on beautiful Lake Teganuma."

This month we interviewed officials from the city's Lake Teganuma Section, which is in charge of environmental conservation in the city. Here follows our report on Lake Teganuma, its history of water pollution, the measures being taken to improve its water quality and its outlook for the future.

Water Quality in Lake Teganuma

Before 1955, Lake Teganuma was fed by abundant springs, and its water was so clear that the bottom of the lake was visible. It is said that fishermen did not need to bring a water bottle with them when they took their lunch out on the lake. This shallow lake was once inhabited by many kinds of aquatic plants including a type of pondweed (Potamogeton dentatus) that is now endangered, and fish such as eel and pond smelt.

A great many waterfowl and other migratory birds also found habitat in the bountiful environment of Lake Teganuma. Children also used to enjoy swimming in the lake. Thus, the lake was a precious resource for people and all the other organisms living in and around it.

However, the lake's capacity to purify itself began to decline in the 1960s when its area was nearly halved due to large-scale land reclamation and accelerating urbanization. The population of Abiko City increased sharply and a large amount of household wastewater was directed into the lake, aggravating water quality problems.

The level of chemical oxygen demand (COD), a water pollution indicator, started rising rapidly around 1970 and reached a peak of 28 milligrams per liter (mg/L) in fiscal 1979. The nitrogen and phosphorus contained in household wastewater caused eutrophication and blooms of phytoplankton such as blue-green algae. Because Lake Teganuma is a closed water body, the abnormal growth of blue-green algae in summer was so extreme that it turned the blue water green and caused a noxious odor.

In December 1985, Lake Teganuma was designated as a targeted lake under on the Law Concerning Special Measures for Conservation of Lake Water Quality, and both the national and prefectural governments set out to implement comprehensive lake purification measures, including improvements to the local sewage system. One of the measures that greatly contributed to restoring water quality was the North Chiba channel project, conducted by the Ministry of Land, Infrastructure and Transport (the Ministry of Construction of the time).

The completion of North-Chiba Channel connecting the Tonegawa River and the Edogawa River allowed water for purifying the lake to be brought in from the channel starting in 2000. Accordingly, the lake's COD level dropped to 11 mg/L in fiscal 2001. Lake Teganuma was thus liberated from its long-time burden of having the country's worst water quality. However, its COD level has still not attained the national environmental standard of 5 mg/L, and Lake Teganuma still has a long way to go to meet this level of water purity.

Measures to Deal with Household Wastewater

Lake Teganuma covers 6.5 square kilometers and its perimeter is 38 kilometers long. In its catchment area, approximately 480,000 people live in seven cities - Matsudo, Kashiwa, Nagareyama, Abiko, Kamagaya, Inzai, Shiroi - and one village, Motono. There are no large-scale factories or other industrial facilities to speak of in this catchment area, and household wastewater accounts for 60 percent of the water pollution. Household wastewater in this context is defined as the water used and discharged in the course of daily household activities such as cooking, washing and bathing, as well as from toilets.

Establishing sewage systems is far and away the most critical measure, but sewage system construction takes a long time and incurs huge costs. Thus, in areas where sewage systems have not yet been completed, wastewater is discharged without treatment from households. Catchment area municipalities without sewage systems are promoting the installation of individual septic tanks.

Most household septic tanks treat only sewage, and local governments are providing subsidies to promote a transition to tanks that treat all household wastewater, including discharges from the kitchen, laundry and bath as well as the toilet. (Note: Following the revision of the Purification Tank Law on April 1, 2001, newly installing the former type sewage-only septic tanks is completely forbidden, and installing the latter comprehensive type of tank is obligatory.)

Please refer to the Ministry of the Environment website on prohibition of new installments of septic tanks that treat only wastewater from toilets (Japanese only)
http://www.env.go.jp/recycle/jokaso/data/law/law-p06.html

However, introducing sewage systems and wastewater treatment tanks cannot completely solve the problem of household wastewater pollution. The most important thing is for the 480,000 people living in the watershed to commit themselves to using water in a less polluting manner. For example, putting a strainer with a paper filter in the sink to purify washing-up wastewater, using up cooking oil and refraining from dumping it down the sink, and using the proper amount of detergent for doing laundry - it could make a big difference if every resident would make this kind of daily-life effort.

Understanding the Beauty of Lake Teganuma

Abiko City has been undertaking a variety of activities designed to awaken its citizens to an appreciation of the beauty and other values of Lake Teganuma. For example, the city hosts boat tours for citizens, including elementary and middle school students. Every October, it holds a "Teganuma Basin Forum" jointly with civic groups, neighboring municipalities, and local research institutes, to provide a forum for presentations and lectures about improving L. Teganuma's water quality and on other environmental issues.

Presentations by elementary and middle school students in particular engender great concern about the environment and L. Teganuma among the children, as well as impressing the other participants. With the participation of residents around the lake, Abiko City also conducts studies of aquatic organisms and the water quality of springs and rivers that flow into the lake. These efforts raise residents' awareness about restoring the lake environment.

In the spring of 1999, a "Teganuma Biotope" was completed on its north shore. "Biotope" (Biotop in German) is a term combining "bio" (living creature) and "top" (place). Citizens participated in creating this biotope by growing aquatic plants for purifying lake water, and this approach has been working well. Water pumped up from the lake is purified by passing through the plant communities in the biotope before being returned to the lake.
Teganuma Biotope(Japanese Only)

In addition, the city's website provides a virtual "Teganuma Aquarium," showing a variety of fish and aquatic organisms living in L. Teganuma with graphics and photos. The first page shows creatures still living in L. Teganuma, such as stone moroko (Pseudorasbora parva), carp, and crucian carp. Another page explains the ecology of creatures now very rare in the lake, such as mussel, eel, and mitten crab.
Teganuma Aquarium (Japanese Only)

Most people who live in and around cities and commute daily to urban centers lead busy lives and tend to forget how they are supported by the local natural environment. To all its citizens, including these busy people, Abiko City is trying to communicate the message that improving water quality and restoring the ecosystem of L. Teganuma is an important task for the whole region.

The city believes that citizen awareness and pride in the lake's beautiful ecosystem will be the first step toward creating a sustainable society in the area. When every citizen feels concern for the lake and tries to have a "Teganuma-friendly" lifestyle, community-level efforts will eventually lead to solutions for global environmental issues.

[Related webpage]
Abiko City
Abiko I Museum (partly English)
Abiko City Museum of Birds

(Staff writer Ichie Tsunoda)