Variability of stream water quality in some land management systems in the southern Kakioka Basin, Japan

Diurnal and seasonal changes of the concentration of eight inorganic ions (NO₃, NO₂, NH₄, PO₄, K, Na, Ca, Mg) in stream water were investigated at four study sites in the rural landscape of the Kakioka Basin, Japan. Study sites included two woodlands and two croplands with rural and urban settlements. The diversification of land use from woodlands and croplands to settlements enhanced ionic concentrations in the stream water. Monthly variations were significant in all the eight ions. The number of ions showing significant diurnal variations increased with the increase of human activities in the drainage basin. Principal component analysis was used to characterize the difference in water quality between study sites and the seasonal and diurnal patterns of fluctuation.