The municipal borders of Lake Biwa had never been established, but at a joint conference held by the municipalities on the shore of the lake, their delegates reached an agreement to establish the borders of Lake Biwa on May 8, 2007; a document was submitted to the Ministry of Internal Affairs and Communications after the approval of each municipality's assembly, and finally the establishment of borders was officially announced in the official gazette on September 28.
琵琶湖の市町境界については、今までどの市町にも組み入れられていなかったが、沿岸の各自治体で行う共同会議において2007年5月8日に境界の設定に合意し、各自治体の議会の同意を得た上で総務省に届け出を行い、9月28日付で官報に確定が公示された。