Study On The Leymus Chinensis Community Of Water Requirement And GSPAC System Water In The Otinday Sandy Area

This paper based on Scientific Allocation of Water Resources for Vegetation Construction in the Sandy Area Between Beijing and Inner Mongolia(50139040),supported by National Committee of Natural Science Foundation, using dual crop coefficient approach presented in the FAO irrigation and drainage paper 56 (FAO56,1998,Crop evapotranspiration, Guidelines for computing crop water requirement).The simulation results were assessed by the approach of consisting in presenting a graphical representation of model simulated transpiration and evaporation compared with observed values and by the regression between observed and model simulated values forced to the origin. The evapotranspiration values assessed were analyzed according to the physiology chacterastics, change in canopy structures, climate factors and root zoon water content. The evapotranspiration and average daily evapotranpiration strength of growing stages were determined and the variations of them were revealed.The main results of the papers are as follows:Using observed values to calibrate, ascertain and checkout the water transfer parameter simulate for SWAP model, carried out water transfer simulate of unsaturated zone and root system layers in two different hydrology years for low-buried ground water and studied the rules of movement of water in GSPAC system.The main results of the papers are as follows:(1) The simulation results are similar between FAO56 and SWAP model, both can calculate water requirement. We can choice the one according to the materials and the purpose of the study.(2) In one day, the transpiration of Community of Leynms Chinensis increases gradually, and arrive at the maximum point at 11-12 clock, then declines gradually, consisting with the solar net radiation, the air temperature, wind speed and the vapor pressure deficit of the air present similar regulation.(3) During the initial period, the transpiration is small, and evapotranspiration is predominately in the form of soil evaporation for the Community of Leymus Chinensis. During the crop development period, transpiration is increased and evaporation is declined gradual with increasing of vegetation coverage. During the mid-season period, the evapotranspiration intensity reaches to maximum and evaporation reaches to minimum. During late season period, the transpiration and vegetation coverage gradual declining, however, the evaporation begin with increasing.(4) In the whole growing period of 2005, soil water storage eliminated 72.7mm in unsaturated zone, the groundwater table declined and the buried depth increased, resulte the supplies reduction of ground water. In the whole growing period of 2006, soil water storage added 46.4mm in unsaturated zone, the increasing of the soil moisture content are the direct reason to the raising of the groundwater table.