Accurate estimates of evapotranspiration and its components are essential for quantifying the water and energy fluxes and water resources management in arid regions. To this end, daily actual evapotranspiration (ET_a), pan evaporation, and concurrent microclimate from an arid shrublands were measured over two growing seasons (2014-2015) to determine water budgets and to test the validity of the complementary relationship (CR) at this temporal scale. The average ET_a is 229.32 ±45.86 mm during two growing seasons, while canopy transpiration, soil evaporation, and interception accounted for 68.1 ±16.5%, 29.1 ±2.5% and 2.8 ±0.6%, respectively. Actual evapotranspiration and Penman potential evapotranspiration, or pan evaporation exhibit complementary behavior, where the complementary relationship is asymmetric. Daily ET_a rates are significantly overestimated by the symmetric Advection-Aridity (AA) model. Employing the modified AA model, where parameters are calibrated locally and wet environment evapotranspiration is evaluated at wet environment air temperature as opposed to the measured air temperature, the prediction accuracy of ET_a is dramatically improved. With calibrated parameters, the E601B sunken pan can satisfactorily describe the dynamics of daily ET_a, while the D20 aboveground pan underestimates it to some extent. Moreover, the modified AA model is able to capture the dynamics of groundwater usage by vegetation during drying summer. These findings gain our new knowledge on the capability of CR theory to resolve special issue occurred in phreatophytic shrublands, and can also provide beneficial reference to water resource and eco-environment management in arid regions.

Accurate estimates of evapotranspiration and its components are essential for quantifying the water and energy fluxes and water resources management in arid regions. To this end, daily actual evapotranspiration (ET_a), pan evaporation, and concurrent microclimate from an arid shrublands were measured over two growing seasons (2014-2015) to determine water budgets and to test the validity of the complementary relationship (CR) at this temporal scale. The average ET_a is 229.32 ±45.86 mm during two growing seasons, while canopy transpiration, soil evaporation, and interception accounted for 68.1 ±16.5%, 29.1 ±2.5% and 2.8 ±0.6%, respectively. Actual evapotranspiration and Penman potential evapotranspiration, or pan evaporation exhibit complementary behavior, where the complementary relationship is asymmetric. Daily ET_a rates are significantly overestimated by the symmetric Advection-Aridity (AA) model. Employing the modified AA model, where parameters are calibrated locally and wet environment evapotranspiration is evaluated at wet environment air temperature as opposed to the measured air temperature, the prediction accuracy of ET_a大大改善了。通过校准的参数，E601B下沉锅可以令人满意地描述每日ET _a的动态，而D20地上锅则在某种程度上低估了它的动态。此外，改进的AA模型能够捕获夏季干旱期间植被对地下水利用的动态。这些发现使我们获得了有关CR理论解决特有植物灌木丛中特殊问题的能力的新知识，也可以为干旱地区的水资源和生态环境管理提供有益的参考。