Study on River Water Quality and Agricultural Land Use

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The present state of river water quality of several agricultural areas in Hokkaido, Japan, was studied. From standpoint of water environment conservation, some consideration was made to the land use as it ought to be.River water concentrations of dairy farming basins show following tendency ; [Forest basin with natural river channel] << [Dairy farming basin with natural river channel] < [Dairy farming basin with artificial river channel]. It is remarkable that 80% of total nitrogen take form of NO_3-N in dairy farming basins, and that the concentration is higher in basin of large cattle population density per pasture, which suggests the apparent evidence of NO_3-N eluviation.Densely populated basin of cattle also shows severe water pollution in relation between river flow and concentration. Artificial river channel indicates higher concentration than that of natural river channel on same level density of cattle population. The function of riparian forest and wetland zones as buffer filter is confirmed.From the fact mentioned above, development of river basin and enlargement of farm keeping give impact not only by scale and condition of farm management, but also influences by the condition of river channel and land use of the basin.The concept about direction of river environment conservation was mentioned using two axs correspond to input and output of load.