Lake Kasumigaura originally was a brackish-water lagoon, with indirect connections to the Pacific Ocean via the Hitachigawa and Tone Rivers.

But today, fishing production has drastically decreased due to water quality deterioration that was partially caused by the closure of the tide gate in 1963 for purposes of desalination.

[3] Today, Lake Kasumigaura is used for fishing, irrigation, tourism, recreation, and for consumption by the surrounding public and local industry.

Other crops include tomato, cucumber, eggplant, watermelon, corn, edamame, sweet potato, kabocha, daikon and peanut.

The wide surrounding wetlands are wonderful for birdwatching, as large numbers of water fowl can be observed, primarily during the wintering period.

Legislation was enacted in 1982 to help prevent it, including a ban on the use and sale of phosphate-containing synthetic detergents, and the control of nitrogen and phosphorus contents in the effluent from factories.