The rotation between rice and winter rape (Brassica napus L.) system is widely distributed around the world especially in southern China (Frolking et al., 2002;S. Liu et al., 2010;M. Zhou et al., 2014), supplying us with food and raw materials for edible oil. Evapotranspiration (ET) is a key hydrological process, which closely links the Earth's energy and water cycles (