In recent years, at a number of lakes such as Lake Biwa, dams have been built in the rivers that connect the lakes to the outer sea, and large-scale river improvement projects have taken place.
また、近年の琵琶湖等、いくつかの湖沼では外洋へ注ぐ河川に堰が造られたり、大規模な河川改修がおこなわれた。