Assessing the influence of watershed land use patterns on the major ion chemistry of river waters in the Shimousa Upland, Japan

To assess the influence of land use pattern on the major ion chemistry of river water, seasonal changes in major ion concentrations were studied in the Shimousa Upland, Japan where urbanisation is still in progress. Water samples were collected from 24 sites from the Ohori River basin and analysed four times representing four seasons from August 2006 to April 2007 during baseflow or low flow conditions. The proportion of different land uses in the drainage area of each sampling site were estimated from a detailed digital land use map published by the Geographical Survey Institute of Japan by using Arcview/GIS. Electrical conductivity (EC) and the concentrations of Na+, K+, Cl− and NO showed significant seasonal variation (p≤0.05). The correlation analysis…