On the value of soil moisture measurements in vadose zone hydrology: A review

Abstract

[1] We explore and review the value of soil moisture measurements in vadose zone hydrology with a focus on the field and catchment scales. This review is motivated by the increasing ability to measure soil moisture with unprecedented spatial and temporal resolution across scales. We highlight and review the state of the art in using soil moisture measurements for (1) estimation of soil hydraulic properties, (2) quantification of water and energy fluxes, and (3) retrieval of spatial and temporal dynamics of soil moisture profiles. We argue for the urgent need to have access to field monitoring sites and databases that include detailed information about variability of hydrological fluxes and parameters, including their upscaled values. In addition, improved data assimilation methods are needed that fully exploit the information contained in soil moisture data. The development of novel upscaling methods for predicting effective moisture fluxes and disaggregation schemes toward integrating large-scale soil moisture measurements in hydrological models will increase the value of soil moisture measurements. Finally, we recognize a need to develop strategies that combine hydrogeophysical measurement techniques with remote sensing methods.

Consequences of varied soil hydraulic and meteorological complexity on unsaturated zone time lag estimates

“…Utilising such numeric models with the correct assumptions and boundary conditions (Vereecken et al, 2008), in conjunction with generic or measured soil physical characteristics and weather data as inputs (Keim et al, 2012;Sousa et al, 2013) (Fig. 1), can be an alternative to field tracer studies.…”

“…Numerous studies have highlighted the crucial role of the unsaturated zone within the hydrologic cycle, and the need for realistic quantification of t u within hydrological models (Torres et al, 1998, Vereecken et al, 2008, Hooper, 2009). Sousa et al (2013) described a methodology to assess the importance of t u within the context of t T (the sum of unsaturated and saturated time lag: t T = t u + t s ) and advocated the use of measured rather than generic data collection to more accurately account for t T .…”

Spatial cross‐correlation patterns of European low, mean and high flows

“…The observations are concentrated on grassland in mid-latitude regions of the Eurasian continent. A variety of other in-situ observation techniques are increasingly used (see Vereecken et al [2008] for a review) and their systematic application may eventually augment available data sources.…”

State and parameter estimation of two land surface models using the ensemble Kalman filter and the particle filter

“…Shi et al, 2015) have focused on an accurate characterization of soil moisture dynamics simulated by LSMs. This is particularly surprising, as root zone moisture storage modulates spatiotemporal variations in climate and weather, and governs the production and health status of crops and the organization of natural ecosystems and biodiversity (Vereecken et al, 2008).…”