Effects of human impacts on watersheds on the present water quality in Mizoro-ga-ike Pond

Abstract

Water quality in Mizoro-ga-ike Pond in Kyoto City was investigated using water samples collected at 40 sites on 3 November 2003. Results of principal component analysis (PCA) on 13 dissolved chemical constituents indicated that tap water from a distribution reservoir of Kyoto city leaking into the pond from the southeastern corner had the most adverse impact on water quality. The inflowing water strongly impacted not only the southeastern part, but also the southwestern part of the pond. The inflowing water was characterized by lower concentrations of dissolved organic carbon (DOC) and higher values of pH, electrical conductivity (EC), Mg2+, SO42-, Na+, Cl-, and Ca2+ than in the pond water. Secondly, pollution through surface runoff from traffic on the north road was also considered to have a negative impact on the pond water. Water quality at sites on the north side of the pond was characterized by higher concentrations of filterable Fe, K+, filterable Si, soluble reactive phosphorus (SRP), and C2+. The first component of PCA using 10 chemical constituents involved in primary production showed intensive eutrophication in the northern part of the pond. Concentrations of filterable Fe, total phosphorus (TP), SRP, filterable Si, K+, Ca2+, and total nitrogen (TN) were higher in the northern than in the southern part. The second PCA component included factors of Sphagnum vegetations such as pH and Ca2+, and some sites on the east side is were plotted opposite the Ukishima hollows, which is characterized by Sphagnum vegetation, along this axis.