The part of the lake to the north of the Biwako Ohashi Bridge, which was built at the narrowest point, is called the Northern Lake or 'Taiko,' while the part to the south is called the Southern Lake; accordingly, the water quality and water flow differ between them.
最狭部に架かる琵琶湖大橋を挟んだ北側部分を北湖（太湖）、南側部分を南湖と呼び、水質や水の流れなどが異なる。