EVALUATION OF LAND-USE AND RIVER WATER-QUALITY OF THE TSUKUBA MOUNTAINS ECOSYSTEM, JAPAN

A short term study in late winter and early spring on river water quality of the Tsukuba mountain ecosystem in central Japan was carried out at 130 sites. The pH, electrical conductivity (EC) and chemical composition were measured. The data were processed statistically by correspondence analysis using pH and EC values and concentrations of nitrite nitrogen (NO2-N), nitrate nitrogen (NO3-N), phosphorus (PO4-P) and dissolved silica (SiO2) to make less scores on samples, and by cluster analysis using the scores to define the relationships between river water quality and land use. The presence of chemical elements such as NO2-N, NO3-N, PO4-P and SiO2 was found to be associated with human intervention and NO3-N was also formed as a result of biological activity in upland fields or forests. Concentrations of the chemicals were very low in the water within forests. Building of roads, quarries or recreation facilities, and use of upland fields changed the quality of water while the presence of a golf course induced high EC value. Paddy fields were found to maintain the water quality. Since it was observed that the river water quality can be maintained or improved by the presence of natural riverbeds, paddy fields and forests, the protection of these forms of land use should be encouraged.