Delineating soil moisture dynamics within an evapotranspiration surface barrier using spatial‐temporal analysis

Evapotranspiration (ET) surface barriers store infiltrated precipitation during the recharge period and release the stored water to the atmosphere via ET. The primary purpose of a surface barrier is to reduce or eliminate drainage to the underlying waste zone. The objective of this study is to analyze the spatial and temporal dynamics of soil moisture within an ET surface barrier based on observed and simulated data. This study characterizes the water movement processes using contour plots of soil moisture content and flux rate in the depth‐time domain. Zero‐flux planes (ZFPs) divide the depth‐time domain into stored water, ET, and drainage zones. Some flow dynamics (e.g., flow rate and direction) that were not observed in the field were elaborated with simulation results to identify the depth of the recharge front of infiltrated water, the release front of stored water, and the bottom of the ET zone. The ET‐drainage divide marks the bottom of the ET zone and the top of the drainage zone. The results showed that the temporal analysis of soil moisture storage could indicate the degree of usage of the storage capacity of a surface barrier. The spatial‐temporal analyses of soil moisture content and flux rate can characterize the durations of the recharge/release processes and the depth of the stored water. Quantification of these processes and related zones provides beneficial understanding of the state and dynamics of soil moisture for a range of weather and vegetation conditions and is useful in optimizing the design of an ET surface barrier.