The nutrient release from bottom sediment in a lake occurs under anoxic condition in the hypolimnion, and influences the water quality in the whole lake. The purpose of this study is to make the influence of bottom sediment on water quality clear. Annual change of water quality in Kawahara Lake was investigated, and laboratory tests and field tests to clear the consumption of dissolved oxygen and nutrient release were carried out. From the test data, the oxygen transfer coefficient and the nutrient release rate were discussed. By comparison the test results between the change of water quality in Kawahara Lake, the efficiency of the tests was confirmed.