Abstract
The brackish lake, which coexisting marine and freshwater, has rich ecosystem. The precious natural environment has to be maintained. The Lake Ogawara in Aomori Prefecture is a brackish lake. The Takase river estuary is tidal river, which connects the Pacific Ocean with the lake. The field measurements of water quality were carried out for this lake on August 27,1999. In the regional development, a balance of development and preserving of natural resource should be considered.
