Study on River Water Quality and Agricultural Land Use

对日本北海道几个农业区的河流水质现状进行了研究。从水环境保护的角度出发，对土地的合理利用进行了考虑。乳业流域的河水浓度呈现出如下趋势：[天然河道森林流域]&lt；；[天然河道乳业流域]。在奶牛养殖流域中，NO3-N占总氮的80%以上，且牧场牛密度较大的流域NO3-N浓度较高，说明NO3-N淋溶现象明显。人口密集的黄牛流域也表现出严重的水污染。在相同的牛种群密度水平上，人工河道比天然河道具有更高的集中度。确定了河岸林带和湿地带作为缓冲过滤器的作用。由此可见，流域的发展和农场规模的扩大不仅受农场经营规模和条件的影响，而且还受河道条件和流域土地利用的影响。

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.