Abstract:Water vapor concentration for different landuse types(tea garden,rape field,wheat field,and fallow land) in the Taihu Lake watershed was measured using static chamber/IRUA method.Diurnal(6:00-15:00)and monthly variations of evapotranspiration were compared among these landuse types.In the monthly evapotranspiration analysis,increasing trends of evapotranspiration rates were observed for all the four landuse types in spring.However, evapotranspiration rate for tea garden decreased by 36.73%after pruning and peak evapotranspiration rate for rape field [2.14 mmol/(m²·s)〕appeared in early flowering stage.Diurnal variations of evapotranspiration rates for these four landuse types showed single peak curves,which reached a maximum value between 12:00 and 15:00.However,diurnal variation of evapotranspiration rate for tea garden became little after pruing,while diurnal variations of evapotranspiration rates for rape field and wheat land increased with the growing stages of rape and wheat.Daily mean values of evapotranspiration rates of the four landuse types were in the order of tea garden [2.24 mmol/(m²·s)]>rape field[1 .48 mmol/(m²·s)]>wheat land [1.28 mmol/(m²·s)]>fallow land [1.16 mmol/(m²·s)].Between 12:00 and 15:00 in late March and between 9:00 and 15:00 in late April,evapotranspiration rate of tea garden was significantly greater than those of rape field,wheat land and fallow land.