Abstract
Water quality of oxbow lakes in middle and lower reaches of Ishikari river basin, Hokkaido, was investigated with special notice to the Ianduse of their surroundings and the form of usage of water in oxbow lake itself. Water quality of oxbow lake during irrigation period of rice paddy was in good condition. Water quality was also good where its water is utilized as source of irrigation. However, with the increase of upland farming in the watershed, the water quality degraded. It is suggested that the irrigation use of water of oxbow lake will sustain the good condition of water quality, so that the conservation of oxbow lake as one of the important element of rural resources must focus on relation with surrounding agricultural activity.
