Chemical Regime and its Variation in Volcanic Lakes

Research Project

Project/Area Number	10640416
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	Meteorology/Physical oceanography/Hydrology
Research Institution	HOKKAIDO UNIVERSITY
Principal Investigator	CHIKITA Kazuhisa Hokkaido Univ., Grad. School of Sci., Asso. Pro., 大学院・理学研究科, 助教授 (70142685)
Co-Investigator(Kenkyū-buntansha)	NISHIMURA Yu-ichi Hokkaido Univ., Grad. School of Sci., Inst., 大学院・理学研究科, 助手 (20208226) TACHIBANA Harukuni Hokkaido Univ., Grad. School of Engng., Asso. Pro., 大学院・工学研究科, 助教授 (90002021)
Project Period (FY)	1998 – 1999
Project Status	Completed (Fiscal Year 1999)
Budget Amount *help	¥2,200,000 (Direct Cost: ¥2,200,000) Fiscal Year 1999: ¥900,000 (Direct Cost: ¥900,000) Fiscal Year 1998: ¥1,300,000 (Direct Cost: ¥1,300,000)
Keywords	Volcanic lakes / Water chmistry / Geothemal activity / Water budget / Chemical mass budget / pH変動 / 酸性湖 / 地下水湧出
Research Abstract	Chemical regime and its variation in two volcanic lakes, Lake Onneto and Lake Kussharo, Hokkaido were examined by estimating their water and chemical mass budgets. Each of the lakes has a geothermal area in the drainage basin, producing hot springs. The chemistry of lake water is thus considered to be controlled by variations in the discharge and chemistry of hot groundwater originated from the geothermal area. Hydrological and limnological observations and water samplings in Onneto and Kussharo were performed for a period of 26 Aug. to 2 Oct. 1998 and of April 1999 to Feb. 2000, respectively. As a result. Groundwater input to Onneto and Kussharo was estimated at 0.012 to 0.049 mィイD13ィエD1/s and at 2.96 to 9.43 mィイD13ィエD1/s, respectively. Calculation of chemical mass budget revealed that a seasonal variation in chemistry of Onneto is dominated by shallow groundwater within the Me-akan Volcano. In order to accurately estimate the water budget in Kussharo, the hydrological data in the ice-cover period proved to be necessary, when the great fluctuation of lake level by surface seiche are neglected.