The Research Of Wetland Water Surface Evaporation And Reeds Evapotranspiration Under Different Groundwater Table

Wetlands, influenced by human activities and climate changes, are facing with a series of ecological and environmental problems, such as area decrease, water pollution, plant decline and biodiversity threat etc. In arid and semi-arid area, the biggest threat to wetlands is water shortage. Wetland evapotranspiration (ET) is the impotent factor of wetland hydrology. Insights of wetland ET can provide accurate and reliable data for the implementation of wetland protection and restoration. The objective of this study was to determine evaporation from water and soil surface and ET of a common wetland plant, reed, through experiment; evaluated and calibrated ET calculation methods, and finally regional ET variation was investigated for Jingwei wetland near Xi'an.This experimentincluded water evaporation, soil evaporation and reeds ET. The result showed that reeds ET increased with the growing stages, and it increased in sunny days and droped sharply in rainy or cloudy weather condition. Groundwater table had big an effect on ET. The deeper groundwater table was, the less the reeds transpiration was. The only difference between soil evaporation and reeds transpiration was the biggest soil evaporation presents after rain.For the study region, ET can be better estimated by Hargreaves Method.The water evaporation coefficient, soil evaporation and reeds transpiration changing trend function in Xi'an are also determined. The result showed the result stimulated by Hargreaves mothed had high precision. And the water evaporation calculated by a new mothed based on water potential theory was less satisfactory.The effect of groundwater table on evapotranspiration was simulated by the experiment results..Groundwater table was influenced by the topography and aroused significantly different patches distribution pattern. Precipitation also had an effect on groundwater table and increased ET.