Evapotranspiration and groundwater exchange for border and drip irrigated maize field in arid area with shallow groundwater

Irrigation effectively guarantees the development of agriculture in arid areas, and groundwater is an essential source of supporting farmland water consumption in shallow groundwater areas. However, it is difficult to accurately quantify the contribution of groundwater to evapotranspiration (ET) on a short time scale, and the influence of different irrigation methods on the hydrological process of farmland are rarely involved. It is significant to understand this process for managing agricultural water use and assessing groundwater resources, especially in arid areas with shallow groundwater. The main purposes of this study were to evaluate the effects of border and drip irrigation on maize ET, and to assess the contribution of groundwater to crop water consumption under shallow groundwater. In this study, eddy covariance system and meteorological station were used to estimate actual ET and potential ET, and the groundwater depth, soil water content in the maize field were monitored. Water balance equation was used to clarify the effective utilization efficiency of irrigation water and water transformation process. The results showed that the total ET of maize growth period under border irrigation and drip irrigation were 490.3 mm and 536.9 mm, and the crop coefficient at the critical growth period were 1.11 and 1.22, respectively. According to the water balance calculation, the effective utilization efficiency of irrigation water under the two irrigation methods were only 0.72 and 0.66. The daily average water flux of groundwater evaporation under border irrigation was around 1.55 mm, which was less than 2.58 mm under drip irrigation over the whole growth period of maize. The contribution rates of groundwater evaporation to crop water consumption of border irrigation at whole growth stage was 26%, which was less than 41% of drip irrigation. These results highlighted the effects of irrigation methods and shallow groundwater on the crop evapotranspiration and field water flux exchange in arid regions, and provided a new perspective for understanding agro-hydrological processes.