分布物理型モデルを用いた霞ケ浦における水循環と溶存態窒素の挙動解析

摘要

There is a need to study water and nutrient transport system of a watershed in order to find effective measurements to reduce amount of non point source pollutant loads. Our research uses WEP model to simulate water and nutrient transport system of Koise watershed. Data of land covers, meteorology, rivers properties, fertilizer input, nitrate concentration in rainfall and others of Koise watershed was processed as inputs to WEP model. Hydrograph and inorganic nitrogen cycle of year 2007 were simulated. Simulation result pattern of year 2007 agrees well with occasional observed data and estimation from ANN model. Year 2008 hydrograph was simulated by the same set of parameter for verification purpose. High reproducibility rate of 0.98 and 0.91 is achieved. Sensitivity of uncertain parameters was analyzed in search of better parameter set to reduce simulation error. Discharge amount of pollutant loads is found to be hugely influenced by fertilizer input, nitrate concentration in rainfall and underground water.%不確実な要素の多い流域スケールにおける水·物 質循環の特性解明と霞ケ浦の水質改善に資すること を目的として，分布物理型モデルを用いた恋瀬川流 域の溶存態窒素の挙動解析を実施した. その結果， 以下の点が明らかになった. (1)恋瀬川流域の水循環解析にWEPモデルが有効で あった. 年間の水収支から，地下水流出と中間 流出が河川流量に大きく影響していることを示 した.