Impact of regional geology, land use and flow path on stream water chemistry in a small watershed

Stream water chemistry is dependent on the physical, chemical and biological processes occurring in the watershed. Understanding the governing mechanism of the stream water chemistry in a watershed is the first step for the water quality management. The study area drains a total catchment area of 1.46 km^2 and consists of forest （80%）, upland （15%） and rice paddy field （5%）. The studied area has two distinctive bedrocks, quartzite and schist. We periodically collected the stream water samples at mainstream and tributaries and the pH, electrical conductivity （EC）, alkalinity and the concentrations of cations and anions of the collected stream water samples were determined in the field and laboratory. The all collected water samples were nearly neutral and the EC and concentrations of Na, K, Ca, Sr, Si and HCO3 of the stream water samples collected from the schist terrain had greater values than those from the quartzite terrain. The mainstream running along the boundary of schist and quartzite terrains had the intermediate values of the tributaries. The stream water samples collected in and near the upland showed a high concentration of NO3^- than those of forest regardless the lithology. The stream pathway was also directly reflected on the chemistry of stream water. The stream water drained in the forest of quartzite terrain had the lowest values of alkalinity, EC and concentrations of cations and anions but the stream water drain in the upland of schist terrain had the highest values of EC and concentrations of cations and anions, especially NO3^-.

Impact of regional geology, land use and flow path on stream water chemistry in a small watershed