Application of Unsaturated Water Supply Techniques in the Large-Scale Weighing Lysimeter System.

    Groundwater, soil water and evapotranspiration are important components of water balance in the field. Lysimeters have become standard instruments for evapotranspiration measurements. It is wildly used in field evapotranspiration, rainfall infiltration experiment, and experimental hydrology. However, a large-scale lysimeter is required to simulate the actual condition with great fluctuation of groundwater level. Thus it would result in extremely complex construction and costly routine maintenance. In present study, unsaturated or tension water supply techniques was applied to improve the weighing lysimeter system. The modified lysimeter shows some of the new characteristics, which are: the volume and weight of the contained soil column is abruptly decreased as compare to a normal water supply system; the convenience for construction or establishment of the lysimeter system is greatly improved; the supply and drainage system can simulate the change of groundwater level, which can reflect the actual conditions and allow researches on soil water dynamic during crop growth. A series of testing experiment results showed that the performance of the new lysimeter are satisfactory and may fully display water transformation in the crop rooting system such as root system development, water consumption, soil water and groundwater transformation, and groundwater level dynamic.