Water dynamics and groundwater recharge in a deep vadose zone

Understanding soil water dynamics and accurately estimating groundwater recharge are essential steps in achieving efficient and sustainable management of groundwater resources in regions with deep vadose zones. The objective of this study was to understand transient data and the dynamics nature of water from deep sections at the thick vadose zone, and to estimate groundwater recharge by applying Darcy's law of unsaturated water fluxes. The study was conducted during year 2009–2013 at Luancheng Agro-ecosystem Experimental Station of Chinese Academy of Sciences, which is located in the North China Plain. The water contents were measured with water probes and matric suctions using pressure transducers at depths of 9 and 11 m and were combined with laboratory measurements of unsaturated hydraulic conductivity to estimate groundwater recharge. The results indicated that the soil water content at 9- and 11-m depths increased following the rainy season and then gradually stabilized. And the intensity and continuity of precipitation events played an important role in soil water changes. The soil water dynamics between different depths (9 and 11 m) indicated a time lag (approximately 5–11 days). The groundwater recharge ranged from 7.60 to 19.75 mm resulting from hysteresis over the study period.