Temporal Stability of Soil Water Content Patterns in Measurements and Simulations: Manifestation and Applications.

Since the concept of the temporal stability in soil water contents (TSWC) has been introduced by Vachaud and coauthors in 1985, a number of research questions has been addressed, e.g. how typical this phenomenon is, how to detect TSWC and what is it affected by, whether TSWC has seasonal characters, and in which soil layers TSWC can be seen. The TSWC has been primarily utilized a as method of reducing the number of sampling observations needed to characterize a field and for upscaling soil water content. Other TSWC applications, such as correcting area-average water contents for missing data, and evaluating the temporal stability in infiltration losses are of interest. The TSWC can be observed not only in measured soil water content time series, but also in water content series simulated for the same site with the Richards equation using different pedotransfer functions. This opens the opportunity of combining multimodeling with monitoring of the soil water regime as a viable approach to simulating water flow in the vadose zone. Moreover, the joint exploitation of TSWC in measured and simulated time series can improve the selection of the PTF set to apply multimodeling. The above properties TSWC in measurements and simulations are illustrated using the soil water content time series measured at 10 depths in 10-cm increment every 15 min for 12 months using Multisensor Capacitance Probes installed at USDA-ARS experimental site (Beltsville, MD). Reasons and mechanisms behind the TSWC undoubtedly present a motivating avenue for further research.