Kasumigaura

Kasumigaura is a freshwater lake located in eastern Ibaraki Prefecture, Japan. It is the second-largest lake in the country by surface area, covering about 220 square kilometers. The lake lies predominantly in Ibaraki, with shorelines touching the cities of Itako and Tsuchiura, and forms part of the region’s river and wetland networks on the Kanto Plain.

The lake is relatively shallow, with depths generally a few meters. It receives inflow from surrounding rivers and drains through waterways that connect to the wider river network in the region. Seasonal changes and nutrient input influence water quality and aquatic productivity, including algal growth in some years.

Ecologically, Kasumigaura supports a variety of aquatic plants and animals and serves as an important habitat for migratory and resident birds. It sustains local fisheries and supports recreational activities such as boating, fishing, and birdwatching. The surrounding shores and islands provide breeding and feeding grounds for wildlife, contributing to regional biodiversity.

Environmental challenges include eutrophication from agricultural runoff and urbanization, which can lead to algal blooms and reduced water clarity. Management efforts have focused on reducing nutrient inflows, dredging and weed control, and maintaining water quality to support irrigation needs and municipal water supplies as well as recreational use.

The lake is a key regional resource, underpinning irrigation for nearby farmlands, supporting water supply for adjacent communities, and attracting visitors for nature observation and outdoor activities. Kasumigaura remains an important symbol of the rural-urban interface in Ibaraki Prefecture.