Estimation of Mechanism of Water Quality Formation from Discharge Water Separation using PCA

Study of the mechanism of water quality formation in reclaimed land (I)

Abstract

Discharge water chemistry at a reclamation farmland catchment at the Gojo Yoshino area in Nara Prefecture is explained as a mixture of representative soil water, groundwater and rain water.Rain water, soil water and groundwater were determined as the source waters (end-members) using Principal Components Analysis (PCA), which deal with nine conservative solutes (alkalinity, nitrate, sodium, potasium, calcium magnesium, chloride, dissolved silica and sulfate).
Based on PCA, discharge water chemistry was characterized by two independent components: the former has a strong positive correlation with sodium, calcium, magnesium, chloride and dissolved silica, and the latter with nitrate and potassium.Discharge water separation at storm runoffs into three end?members results in large contributions of rain water and soil water to discharge water, and12%to 19%of the discharge water was groundwater.Agreement of measured and calculated concentrations using this separation method was not so good except for alkalinity and nitrate.The reason for this appears to be instantaneous large changes in soil water chemistry during storm runoffs.