Abstract
At Mt. Tanigawa which was one of the source of Tone River basin, rainfall and snowfall of the summit were continually collected, and each nitrogen component was analyzed. The nitrogen concentration of mountain stream water which escaped from Mt. Tanigawa was also continually collected and analyzed. Then the research of river water quality was carried out for 5 times per year from mountain stream to Tone Oozeki Barrage located in most downstream edge of Gunma pref., and the transition of nitrogen concentration was observed. At the Tone Oozeki Barrage, the great bulk of water was taken as water supply resource of the Metropolitan area.
The nitrogen concentration at the summit rainfall and snowfall agreed well with that of mountain stream water. The nitrogen concentration of Tone River was over 1mg/1 from Numata city in the upstream area. At the Tone Oozeki Barrage, the nitrogen concentration was 2 to 3mg/1 through the year. These values were rather high as the resource of water supply.
