World Lake Day, designated by the United Nations General Assembly in December 2024 to be observed on August 27, traces its origin to the opening day of the first World Lake Conference, which was hosted by Shiga Prefecture in 1984 in Shiga, Japan. Since then, Shiga Prefecture has been actively working to mainstream lake environmental issues within the global water agenda.
Shiga Prefecture is home to Lake Biwa, the largest lake in Japan. Lake Biwa provides water not only to Shiga, but also to the prefectures of Kyoto, Osaka, and Hyogo, supporting the daily lives of 14.5 million people and industries across the Kansai region. It is also valued as a treasure trove of diverse ecosystems. People in Shiga have been connected to Lake Biwa since ancient times, benefiting from its abundant resources and living in harmony with the forces of nature.
However, in 1977, Lake Biwa experienced its first major outbreak of freshwater red tide. After synthetic detergents containing phosphorus were identified as the main cause, a social movement known as the Soap Movement spread across Shiga, led by primarily housewives, calling for residents “to use powder soap and avoid using synthetic detergents.”
As a result of this movement, Shiga enacted the Eutrophication Prevention Ordinance in 1979 to regulate phosphorus. Thanks to reduction in inflow load, outbreaks of red tide have been successfully suppressed.
A prefecture-wide convention was held in 1980 to commemorate the enactment of the ordinance, and July 1, the day the ordinance went into effect, was designated as Lake Biwa Day on that occasion. Since then, Lake Biwa Day has become a symbolic day for residents to express their appreciation for the lake and take part in environmental protection, with cleanup activities held throughout the prefecture each year.
Therefore, starting this year, Shiga Prefecture will designate the period from July 1 to August 27 as the “Lake Biwa Activity Priority Period.” In my presentation, I will introduce various initiatives and activities related to Lake Biwa that take place during this time.
In addition, in 2021, Shiga Prefecture established the Mother Lake Goals (MLGs)—a Lake Biwa-specific version of the SDGs—together with its citizens, as a new policy framework to promote lake environmental conservation.
The MLGs are also aligned with the achievement of the SDGs. We believe that the MLGs will contribute to sustainable lake management, and I will introduce our efforts to collaborate with residents in working toward these goals.