Experiment on phreatic evaporation of bare soil and soil with crop in Huaibei plain

Sixty lysimeter experimental data of Wudaogou test station were used for further studying on the variation rules between phreatic evaporation and groundwater level under different soil types and vegetation conditions in Huaibei plain, China. The differences of phreatic evaporation between bare soil and soil with crop were compared from three aspects of zero groundwater burial depth, depth increased and critical depth, and the relationships between phreatic evaporation and meteorological factors were also analyzed. Six phreatic evaporation optimal formulas and correlation parameters for lime concretion black soil and fluvo-aquic soil were obtained by daily and ten days data fitting. The evaporation capacity calculated by Penman-Monteith formula was in place of observed values to improve the fitting accuracy. Taking bare soil phreatic evaporation plus increased-water consumption of crop as the total evaporation in vegetation area, increased-water consumption statistical method in different growth stages and burial depthes is recommended for phreatic evaporation calculation in vegetation areas, and it is a simple, applicable and high accuracy method.