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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Environmental Microbial & Food Safety Laboratory » Research » Publications at this Location » Publication #299997
Title: Effects of soil hydraulic properties on the spatial variability of soil water content: Evidence from sensor network data and inverse modeling

Author
item QU, WEI - Julich Research Center
item BOGENA, HEYE - Julich Research Center
item HUISMAN, ALEXANDER - Julich Research Center
item MARTINEZ, GONZALO - US Department Of Agriculture (USDA)
item Pachepsky, Yakov
item VEREECKEN, HARRY - Julich Research Center

Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2014
Publication Date: 9/19/2014
Citation: Qu, W., Bogena, H., Huisman, A., Martinez, G., Pachepsky, Y.A., Vereecken, H. 2014. Effects of soil hydraulic properties on the spatial variability of soil water content: Evidence from sensor network data and inverse modeling. Vadose Zone Journal. 13(12):99.

Interpretive Summary: Information about spatial and temporal variability of soil water content has multiple uses, including plant water status diagnostics, monitoring, forecasting, and management. Networks of soil water content sensors allow scientists and growers to obtain exhaustive information about spatial and temporal variations in soil water contents. However, a methodology is needed so that these data can be used to explain how the spatial variability is related to the temporal one, and whether they have common controls. Our hypothesis was that such a methodology should be based on a joint characterization of the ability of soil to transmit and to retain water. We demonstrated that this assumption leads to reliable relationships between temporal variability of soil water contents and spatial variability of soil hydraulic parameters. When further confirmed, this finding can be of use in a multitude of hydrological projects where relatively easily obtained soil water monitoring data can be used to estimate soil hydraulic properties, which are much more difficult to measure., In addition, the estimated variability of soil hydraulic properties can be used to predict the magnitude of the temporal variability of soil water contents. This information should be useful to other scientists.

Technical Abstract: Improved understanding of the temporal variability and stability of soil water content (SWC) and its relation to local and nonlocal controls is a major challenge in modern hydrology. The objective of this study was to assess the effect of soil hydraulic parameters on temporal stability of SWC with an inverse modeling approach. Using observed time series of SWC at 5-cm, 20-cm and 50-cm depths obtained with a wireless sensor network and the process-based HYDRUS 1D model, van Genuchten-Mualem (VGM) parameters were inversely estimated for 41 locations within the TERENO test site Rollesbroich. We used the shuffled complex evolution (SCE) algorithm to optimize VGM parameters ('r, a, n and Ks) for two cases: no prior information and with prior information about the correlation between VGM parameters. The results showed that the inversely calibrated HYDRUS-1D model was able to reproduce the observed time series of SWC reasonably well for both optimization strategies. Furthermore, we found a linear relationship between the mean relative difference (MRD) of SWC and 's. Also VGM parameter of log10(Ks), n, and log10(a) were strongly correlated with the MRD of saturation degree for the prior information case, but no correlation was found for the case where prior information was not considered during inverse parameter estimation except at 50 cm depth. Based on these results, we suggest that establishing relationships between spatio-temporal variability of SWC and spatial variability of soil properties presents a promising research avenue to better understand local controls on SWC variability and temporal stability.