From September 2008 to October 2009, we carried out field surveys at five points of the main stream and tributaries of Kasumi River, Arakawa drainage system to investigate current status of the Nitrate-nitrogen pollution of the Sayama tea field, along with measuring detailed amount of the outflow load because no measurements had been conducted there. We carried out the measurements frequently, including the conditions of high water levels. We measured the concentrations of Nitrate-nitrogen, and found that they exceeded the environmental standard (10 mg · l^-1) at two points of the right bank where the tea plantation extends. The highest value was as much as 36.5 mg · l^-1 , that is, the Nitrate-nitrogen pollution is serious even in the Sayama tea field where fertilization standard to the tea is the lowest in Japan (450 kg · ha^-1 · y^-1).
 The outflow load of Nitrate-nitrogen increased remarkably at high water levels in the main stream, while a significant difference of the load was not found between ordinary and high water levels at the tributaries where tea plantation extends. We estimated the total nitrogen load from the tea plantation as much as 53 ∼154 kg · ha^-1 · y^-1 At the point where the highest concentration was observed, the load was as small as 53 kg · ha^-1 · y^-1 , however, the river discharge was also small which resulted in the highest concentration. Moreover, we found it necessary to reduce the amount of nitrogen fertilizer to 390 kg · ha^-1 · y^-1 in order that the concentration should be smaller than the environmental standard.

View full abstract

 It is said that, in the 21st century, water scarcity has become a grave concern, especially in arid and semi-arid regions where climatic conditions impose a constraint on water resources. Such a severe constraint poses a threat to economical growth. Increase in water demand associated with rapid economic development exacerbates incidences of water shortage. Water shortage is not only an issue concerning arid and semi-arid regions but likewise affects developing countries and regions where the effects of climate change are significant. The objective of this study was to clarify the relationship between socio-economic growth and water demand and to estimate the fine spatial gaps in the demand and supply of water in China. Regional water demand from different sectors (agricultural, industrial, domestic) was estimated using a macro framework of socio-economic growth. Water supply from regional resources was estimated using observed meteorological data. Spatial gaps were found in the demand and supply of water using a 0.5 degree macroscopic mesh. Further, the amount of water flowing in both the Yellow River and the Chang River was estimated using a cascade-type water flow model.

View full abstract