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Title: Effect of soil hydraulic properties on the relationship between soil moisture variability and its mean value

Author
item MARTINEZ, GONZALO - U.S. DEPARTMENT OF AGRICULTURE (USDA)
item Pachepsky, Yakov
item VEREECKEN, HARRY - JULICH RESEARCH CENTER

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2014
Publication Date: 8/1/2014
Citation: Martinez, G., Pachepsky, Y.A., Vereecken, H. 2014. Effect of soil hydraulic properties on the relationship between soil moisture variability and its mean value. Journal of Hydrology. 516:154-160.

Interpretive Summary: Knowing the variability of field soil water content is essential for a number of purposes, including designing soil water monitoring regimens, evaluating soil water flow predictive models, and establishing margins of safety for soil water conservation management practices. There are contradictory reports on the variability in soil water content as soils become drier or wetter. We investigated this topic for relatively dry soil conditions using soil water flow modeling. It appears that the dependence of soil water variability on average soil water content is controlled by the soils ability to transmit and to conduct water; this in turn is affected by the local climate. This result indicates that estimation of spatial variability of soil hydraulic parameters can be extracted from spatio-temporal data on soil water content. These results can be useful for producers and consumers of soil hydrology information in that monitoring soil water can provide information about soil hydraulic variability, which is otherwise time- and labor consuming to measure.

Technical Abstract: Knowledge of soil moisture and its variability is needed for many environmental applications. We analyzed dependencies of soil moisture variability on average soil moisture contents in bare soils using ensembles of non-stationary water flow simulations by varying soil hydraulic properties under different climatic conditions. We focused on the dry end of the soil moisture range and found that the magnitude of soil moisture variability was controlled by the interplay of soil hydraulic properties and climate. The average moisture at which the maximum variability occurred depended on soil hydraulic properties and vegetation. A positive linear relationship was observed between mean soil moisture and its standard deviation and was controlled by a soil moisture characteristic parameter. The influence of other controls needs to be studied further to see if such relationship persists and could be used for the inference of soil hydraulic properties from the spatiotemporal variation in soil moisture.