Deterioration of Water Pollution in Kasumigaura - July 1996

Deterioration of Water Pollution in Kasumigaura - July 1996

Pollution in Kasumigaura is caused by phosphorus and nitrogen in domestic and agricultural wastewater from the Tsuchiura and Tsukuba Cities area in Ibaraki Prefecture, which has led to eutrophication. In 1973, a large outbreak of blue-green algae was observed, resulting in mass mortality of farmed fish. Urbanization has reduced the amount of wetlands, and the natural purification function of the lake has also declined. The lake is shallow, with an average depth of approximately 4 meters, and its residence time is as long as 200 days or more, making it prone to accumulation of incoming pollutants. In addition, wastewater containing zinc and lead from factories in Tsuchiura and Ryukesaki cities, as well as fertilizers and pesticides from agricultural lands, have also magnified the problem. In particular, wastewater from the livestock industry accounts for 33% of Kasumigaura's total nitrogen load and 20% of domestic wastewater, and combined with the delay in environmental measur
es by corporations, the pollution has become more serious.