TEMPERATURE, PRECIPITATION, AND RIVER DISCHARGE EFFECTS ON NITRATE–NITROGEN CONCENTRATIONS IN TAP WATER USING CORRELATION COEFFICIENTS AND PRINCIPAL COMPONENT ANALYSIS

Abstract

 For the contribution to reduce a poisonous risk of Nitrogen, factors for nitrate-nitrogen concentration varience of tap water were discussed. Temperature, precipitation, river discharge and discharge from the Amagase dam effects on nitrate–nitrogen concentrations of tap water were measured in Suita city, located in the Lake Biwa and Yodo River basin. Concentration data for 2340 days were obtained at 22:00 each day during October 2007 through December 2015. The daily measured nitrate-nitrogen concentrations of tap water in Suita city and the monthly data of normal stage of water, which are reported in public, were compared. The varience coefficient of the daily measurement was larger, because the data were obtained not only on the normal stage day but also on the days of precipitation and larger discharge from the Amagase dam, which caused concentration changes. The correlation matrix and the principal component analysis clarified that the increase of nitrate-nitrogen concentration is affected by lower temperature or lower discharge from the Amagase dam, and that the decrease of the concentration is influenced by the higher temperature and the higher discharge.