Update: June 10, 2013 About Shiga


Lake Biwa

What is Lake Biwa Day?

In July 1,1980, Shiga Prefecture’s Ordinance for the Prevention of Eutrophication of Lake Biwa (Lake Biwa Ordinance) went into effect. This ordinance was the first in Japan to impose regulations on the discharge of nitrogen and phosphorous, which had been causing eutrophication of Lake Biwa. In 1981, the prefecture designated July 1 as “Lake Biwa Day” to commemorate the first anniversary of the enforcement of the Lake Biwa Ordnance.


In July 1996, the Shiga Prefecture Basic Environmental Ordinance went into force. The ordinance stipulated that July 1 was to be Lake Biwa Day, in order to widely promote understanding and awareness of environmental protection among residents and companies of Shiga Prefecture, and to enhance their motivation to participate in environmental conservation activities.

Water Quality of Lake Biwa

In 1977, a large-scale freshwater red tide occurred in Lake Biwa . However, due to subsequent efforts to improve the lake’s water quality, the inflow of phosphorous has decreased, which has led to reductions in both phosphorus concentration and eutrophication. Meanwhile, however, we have seen the emergence of a new problem: the level of chemical oxygen demand (COD), an indicator of organic matter pollution, has gradually increased in the lake, despite the reduced pollutant inflow into the lake. This gradual increase may be partly attributable to persistent organic pollutants, which are hard to decompose by microorganisms. Based on research findings obtained so far, Shiga Prefecture will promote further studies to see what impacts persistent organic pollutants have on Lake Biwa’s environment, including its ecosystems.

Global warming and Lake Biwa

The average annual temperature of Hikone City, Shiga Prefecture is increasing by 1.2℃ per 100 years. Similarly, the temperature of Lake Biwa’s surface has also been on the rise. Ongoing global warming may be causing new problems for Lake Biwa such as depleted oxygen levels in the hypolimnion of the northern basin Global warming is also considered to adversely affect the lake’s ecosystems, rice and other agricultural products, and people’s everyday lives.

Shiga Prefecture aims to realize a low-carbon society, where greenhouse gas emissions in 2030 will be reduced by 50% compared with 1990 levels. Toward this end, the Shiga Prefecture’s Ordinance to Promote a Low-Carbon Society went into effect on April 1, 2011. Moreover, Shiga Prefecture has drawn up its Roadmap for a Low-Carbon Society, which shows a course for moving ahead while striving for optimal balance between environmental conservation and economic development.

Biodiversity in and around Lake Biwa

The Lake Biwa water system is home to 1,000 or more species of aquatic fauna and flora, with more than 60 confirmed to be indigenous. However,nigorobunacrucian carp(Carassius auratus grandoculis), setashijimior Seta clam (Corbicula sandai), and other endemic species that are familiar to local residents have been listed as endangered in the 2010 Shiga Prefecture Red Data Book.

The factors contributing to the decline of endemic species include a decrease in the number of spawning and breeding grounds, and increase of invasive alien species, such as largemouth bass (Micropterus salmoides)and blue gill(Lepomis macrochiru). The propagation of introduced alien fish and plants has disrupted the pristine ecosystem of Lake Biwa. In recent years, the agriculture, forestry and fisheries industries have been seriously damaged by wild birds and animals, such as macaque, deer, and great cormorants. In the fishing grounds in Lake Biwa and connected rivers, serious concerns have arisen regarding great cormorants, which eat a large amount of fish and damage fishing implements. At the nesting places of the cormorants, tree branches are broken when they build nests, and trees are killed by the birds’ droppings, causing damage to forests and landscapes.

Biodiversity in and around Lake Biwa

In March 2006, the Ordinance on Symbiosis with Wild Fauna and Flora was enacted. This Ordinance aims to realize harmonious coexistence between people and wildlife by promoting measures to protect rare wild species and countermeasures against alien species and harmful wildlife. Through such legislation, Shiga Prefecture endeavors to achieve optimal coexistence with wild fauna and flora.

Forests and Lake Biwa

In Shiga Prefecture, forests cover 200,000 hectares, i.e. roughly half the total area of the prefecture, accounting for about 60% of the land area. Most rainwater falling in forests surrounding Lake Biwa flows into the lake, which nurtures rich ecosystems and thereby sustains our lives.

In addition to playing these roles as a water source, forests offer a variety of values such as disaster prevention and timber production.

Forests and Lake Biwa

Currently, an increasing number of forests are ill-managed and devastated due to various changes in socioeconomic conditions and people’s lifestyles. If we allow these forests to continue to deteriorate, the subsequent decline in the multifunctionality of forests will have significant impact on our everyday lives.

To address challenges regarding forestry, the Lake Biwa Afforestation Ordinance was enforced in April 2004. In turn, in April 2005 Shiga Prefecture implemented the Basic Plan for the Afforestation of Lake Biwa, whose basic principle is to realize the concept of the Ordinance by promoting regeneration of forests that sustain Lake Biwa and people’s daily lives. In 2006, Shiga Prefecture introduced a new prefectural tax for promoting forest regeneration, incorporating the following new approach: afforestation by involving residents in environmental conservation.

Waste management and Lake Biwa

Waste littered on the roads may be carried away by large and small rivers that flow into Lake Biwa. The litter can then reach the lakeside, impairing the beautiful landscapes and negatively impacting the lake. In recent years, problems concerning fishhooks and fishing lines discarded by sport fishers have become conspicuous, greatly affecting waterfowl and other wildlife living in or along the lake.

To address these littering problems, in 1992 the Ordinance for Prevention of Littering in Shiga Prefecture (Clean Ordinance) went into effect, setting forth provisions regarding anti-littering and beautification activities. The Ordinance designates May 30 as Zero Waste Day, July 1 as Lake Biwa Day, and December 1 as Environmental Beautification Day. On these days, local residents, companies and prefectural/municipal government agencies participate together in activities to clean up their respective cities and towns.

Also, the Omi Eco-Foster System, in which participating local companies and organizations engage in activities to beautify roads and other public places, has increased in popularity. In this manner, Shiga Prefecture strives to reduce litter and raise public awareness about anti-littering.


Cleaning activity by participants of the Omi Eco-Foster System

Agriculture around Lake Biwa

In 2003, Shiga Prefecture enacted its Ordinance for Promotion of Environmentally Conscious Agriculture, for the purposes of providing consumers with safer and more reliable agricultural products, as well as promoting the widespread practice and establishment of ecological agriculture that is friendly to Lake Biwa. The prefecture encourages eco-friendly cultivation of agricultural products that use less than half the normal amount of pesticides and chemical fertilizers and without discharging agricultural wastewater. Farm products produced in this manner are certified as “Eco-friendly Agricultural Products” by the prefecture.

Under the catchphrase “Eat Eco Shiga,” producers and consumers of Eco-friendly Agricultural Products collaborate together to protect Lake Biwa. Consumers are encouraged to continue purchasing and eating these products available at supermarkets, direct sales stores and consumer cooperatives, thereby protecting the prefecture’s natural environment and Lake Biwa.

Certification label for Eco-friendly Agricultural Products

Fisheries of Lake Biwa

In Lake Biwa, various fishing methods are used to harvest fish such as ayu(sweet fish), nigorobunacrucian carp, honmorokominnow, and biwamasu(Biwa salmon), shrimps such as sujiebishrimp, and clams such as setashijimi(Seta clam). Many of the traditional fishing methods have developed in a unique manner. These traditional methods devised by our ancestors have been handed down to the present day, although materials used for fishing implements have changed and new power sources have been introduced for fishing.


Making use of the harvests from Lake Biwa, a unique food culture has developed in Shiga, exemplified by such delicacies as funazushi(fermented crucian carp), tsukudani(food boiled in soy) of fish from the lake, and amenouorice (rice boiled with biwamasu[Biwa salmon]).


Meanwhile, though, the fish catch from Lake Biwa has continued to decline since around 1955 when the catch hit its peak. Various reasons for the decline have been considered. These include the decrease in the number of fish spawning and breeding grounds, and more recently, damage caused by alien species and great cormorant, both of which are predators of native fish.

To reinvigorate Lake Biwa’s fishing industry that thrived in the past, it is urgently necessary to reverse the decline of native fish and shellfish populations, and regenerate fishing grounds. Shiga Prefecture is taking measures to address these problems, in terms of native species’ breeding and habitat creation, human resource development and harmful species control.

Life around Lake Biwa

Since ancient times, people living around Lake Biwa have protected and maintained the lake with a sense of gratitude for the benefits the lake continues to offer, and have worked to bequeath the lake to future generations in sound condition.

In the Harie and Shimofuri district of Shin-Asahhi-cho, Takashima City, a large volume of riverbed water called “shozu” gushes out, which is used by local residents for cooking and other purposes in their daily lives. Many houses have kabata, unique washing spots using this spring water. The kabatareflect traditional relationships between people and water in the region.


The culture of Omi (old name of Shiga Prefecture) has been nurtured through the above-mentioned harmonious coexistence between Lake Biwa (water) and people. Cultural assets related to Lake Biwa and water have been selected and valued as “Omi Water Treasures.”

Landscapes in and around Lake Biwa

 The magnificent landscapes of Lake Biwa have been loved by people since ancient times, as The Eight Views of Omi and The Eight Views of Lake Biwa. People in Shiga Prefecture have lived in close connection with Lake Biwa. For example, local residents continue to use a unique fishing method with eri, a traditional fixed-trap netting in the lake, a farming method that makes use of aquatic plants growing in Lake Biwa as fertilizers in paddies and dry fields, and the kabatafor washing. These distinctive lifestyles and livelihoods associated with Lake Biwa and water have created attractive landscapes unique to Shiga.

In the rural districts, secondary natural environments have been formed mainly consisting of paddy fields, waterways and satoyama (literally “village forest,” which refers to natural woodland that coexists with a nearby populated area) all of which serve as habitats for various life forms, creating beautiful rural landscapes. Shiga Prefecture is committed to preserving these rural landscapes by promoting community-wide measures such as green planting on the slopes of farm roads and careful grass-cutting in coordination with farming activities.

The rice terraces in Hata, Takashima City, have been selected as one of Japan’s best 100 rice terraces. To preserve the rice terraces in Hata and five other areas, the prefecture has introduced the Shiga Rice Terrace Volunteer System and the Shiga Rice Terrace Trust System. These systems are intended to pass on to the next generations the rice terrace areas’ multilateral functions (e.g. beautiful sceneries and rich ecosystems), in cooperation not only with local farmers, but also with urban residents and companies.

Landscapes in and around Lake Biwa

Environmental technology and business

Shiga Prefecture, home to Lake Biwa, also strives to promote industries in an environmentally friendly manner. Enviro-Shiga, commenced in 1998, has now grown into one of Japan’s largest comprehensive trade fairs for environmental industry. Enviro-Shiga provides a venue for business talks, transactions and exchanges regarding the latest products, technologies and services designed to minimize environmental impacts, with the aim of achieving both environmental preservation and economic development.

Environmental technology and business

In recent years, companies have become increasingly aware that they should fulfill their social responsibility by contributing to their local communities and to the greater society. To this end, companies are actively implementing various programs. For example, company employees and their families participate in activities to preserve forests and paddy terraces, clean up lakeside areas, and participate in hands-on events for reed cutting.

Environmental activity base

The Lake Biwa Museum was established in April 1996, and opened to the public in October of the same year, after more than a decade of preparation. Its purpose is to conduct research on humanity’s historical relationship with lakes, collect and classify related data, and share its research findings with the people of Shiga Prefecture in order to pursue a better future. The Lake Biwa Museum is a research institute, cultural center, and life-long study facility, as well as a center of interaction and information.

The Lake Biwa Museum houses the Environmental Learning Center. As a hub for promoting environmental learning that leads to environmental conservation activities, the Center supports and coordinates environmental learning planning and provides information on environmental learning.

The Environmental Learning Center of the Lake Biwa Museum manages Ecoloshiga, which is full of information helpful in planning environmental learning and formulating environmental programs. Specifically, Ecoloshiga collectively offers information regarding examples of environmental programs, instructors, facilities (fields) for environmental learning, videos, books and other learning materials, and more.


Partnerships and international cooperation

The Lake Biwa basin area occupies about half the entire size of the Lake Biwa-Yodo River basin area. Lake Biwa not only serves as a source of tap water for 14 million people in the Kinki region, but also brings about significant benefits to people living in the downstream areas in various ways, such as flood control and the river environments. The lake is indeed a treasure for all residents in the basin area. For this reason, it is essential that all local governments in both the upstream and downstream areas work together and deepen collaboration that transcends prefectural boundaries in order to address common issues of the basin area.

In March 2003, the Third World Water Forum was held in the Lake Biwa-Yodo River basin area (Shiga, Kyoto and Osaka). At the Forum, a joint statement was announced by these three prefectures and Otsu, Kyoto and Osaka Cities. In this regard, together with other prefectures concerned, Shiga Prefecture established the Lake Biwa-Yodo River Basin Area Network Promotion Committee in August 2004, with the aim of establishing a network for water environment conservation. The committee promotes conservation programs in partnership with residents, non-profit organizations and other various entities.

In addition, to share our experience in protecting Lake Biwa with concerned people worldwide, Shiga Prefecture proposed to hold the First World Lake Conference in 1984, bringing together researchers, governments and residents to discuss measures to resolve various environmental problems regarding lakes and reservoirs around the world. Shiga Prefecture has been active in contributing to the preservation of other lakes and reservoirs sharing similar issues, by demonstrating Lake Biwa to the world as a model for lake conservation to achieve harmonious coexistence of people and nature.

the Third World Water Forum

After the success of the First World Lake Conference, Shiga Prefecture established the International Lake Environment Committee (ILEC) in 1986 as an international non-governmental organization. The objective of ILEC is to promote environmentally sound management of lakes and their environments by promoting international research and investigation, and by facilitating the exchange of findings and knowledge among experts throughout the world. ILEC collects and provides information and data on lakes and reservoirs, and helps organize the World Lake Conference, which has been held in various places around the world roughly once every two years.

What can we do for the environment in our life?

What we can do to protect the Lake Biwa environment is not limited to activities done in and around Lake Biwa, such as lakeside cleanups and reed cutting. There are lots of things we can do in our everyday lives.

Keep Lake Biwa clean

  • Filter kitchen wastewater with a draining bag, etc. to remove garbage that should not be discharged with wastewater.
  • Sprinkle water used for washing rice and milk cartons onto plants.
  • Use minimal amounts of shampoo and conditioner.
  • Before washing dishes, wipe them with old rags to remove stains.

Restore the rich ecosystems of Lake Biwa

  • Survey what kinds of organisms are living in Lake Biwa.
  • Participate in volunteer and environmental activities to protect Lake Biwa and rivers.
  • Do not release any non-native species caught into the lake and rivers, but eat or put them in collection boxes.

Become more interested in Lake Biwa

  • Increase opportunities to eat dishes using fish from Lake Biwa, e.g. tsukudani (food boiled in soy) of ko-ayu (lake ayu) and funazushi (fermented crucian carp).
  • Go to Lake Biwa and connected rivers to have more opportunities to commune and play with water.