Because factories around Lake Biwa pumped the water out of the ground, and many of them dumped effluents deliberately until the Water Pollution Control Law was amended to prevent them from discharging effluents into the ground, the contamination of underground water in the factory area near the lake has worsened, and some people have strongly urged quick action in order to protect the water in what is the world's most enclosed watershed area.
また、周辺の工場は地下水をくみ上げ、さらに汚染水地下水浸透禁止の水質汚濁防止法が改正されるまでは、汚染水を意識的に地下に浸透していた工場も多く、琵琶湖周辺の工場地帯の地下水汚染は進んでおり、世界一の閉鎖性水域の琵琶湖の水環境を守るために、早急の対策が必要と言われている。