霞ヶ浦
Lake Kasumigaura originally was a brackish-water lagoon, with indirect connections to the Pacific Ocean via the Hitachigawa and Tone Rivers. In 1963, the construction of a gate near the confluence of these rivers disconnected the lake from its sources of ocean water. As a result, the salinity of Lake Kasumigaura declined, and today the lake contains fresh water. This lake was famous for its traditional fishery during the Edo period. 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.