The Study of the Hydrological Processes in the Soil by Lysimeter (I) : The Simulation of Recession Process

愛知演習林に設置されたラシメータを対象に，土中水移動に関する数値モデルを適用した結果を報告する。モデルは温度傾度と水分傾度の一次結合によって水と熱の流れを表現する構造を持つ。また，地表面では先ず熱収支を考慮して地表面温度を決定し，地表面と地上1.5mの微気象条件に従い，この地表面における温度と水分の状態を境界条件として土体内の水の温度の分布が決定され，これに応じて浸出量が決定される。同地区における4月末の気象条件を入力として，土体の飽和状態から出発して60時間の圧力分布，温度分布，浸出量，蒸発量が求められた。得られた結果は現象を良く説明していると判断される。今回は実験値が必ずしも十分でなく，モデルのパラメータにはいずれも標準的な数値を用いたが，今後，実験あるいは実測値との照合を行なって最適な値を求めれば，蒸発量の時間的な変化を高い精度で求め得ると考えられる。The numerical model on the hydrological processes in the soil was applied to the lysimeter in the Tokyo University Forest in Aichi, Inuyama Area. The model expressed flow of water and heat by the linear combination betwen temperature and moisture gradient. Further, the ground surface temperature was determined with due regard to the heat balance, and the evaporation was calculated according to the micrometeorological conditions among the ground surface and 1.5m above ground. The distribution of water and temperature in the soil was determined by regarding the condition of temperature and moisture on the ground as the boundary conditions, and according to that, oozing was determined. By inputting the meteorological conditions at the end of April in this area, the distribution of pressure and temperature, the oozing, and the evaporation were simulated during sixty hours after the soil had become saturated. According to the results, it was judged for the model to be able to explain the phenomena very well. Here, standard values were used as the parameters of the model. If the optimum values of them are obtained by cailbration between the measured and calculated values, it is expected that the change of evaporation with time can be obtained with high accuracy