Issues

A new analytical approach is proposed to describe water infiltration into dual-permeability soils. The proposed model, validated in our study against numerical and experimental data, can be used to design devices and procedures for detecting dual-permeability behavior using water infiltration experiments.

We used hydraulic conductivity pedotransfer functions and power law upscaling in simulations of a tracer transport in soil. Using only pedotransfer functions caused a substantial difference between measured and simulated concentrations. After pedotransfer estimates were upscaled, the accuracy of simulations was the same as that of the calibrated model.

We present a comparison study on how well capacitance and time domain reflectometry water content sensors can estimate average water content values in non-uniformly wetted soils. This ability is important in studies where accurate average values are crucial.

A new sensor, based on ultraviolet absorption spectroscopy, was proposed in previous work for in situ measurement of nitrate in the vadose zone. This work investigated the interference of different ions and dissolved organic carbon (DOC) in the soil solution on the absorption by nitrate. High concentrations of DOC highly interfere with nitrate absorption. A methodology for sensor placement in the soil and value correction was developed and demonstrated to allow for an accurate estimation of nitrate concentration.

Cosmic-ray neutron probe (CRNP) soil moisture estimates were compared with measurements from a soil moisture sensor network revealing that near-surface numerically simulated estimates improved correlation. Additional calibration during the wet period significantly improved CRNP correlations over traditional one-time calibration taken under drier conditions.

Two different laboratory procedures were evaluated for calibrating impedance sensors to improve the accuracy of soil moisture measurements. Superior calibration accuracy was achieved using the dry-down procedure relative to the results obtained using an infiltration wet-up procedure. This result was particularly notable in clay-rich soils.

Correlations between spatial variability of soil water and hydraulic parameters were investigated using sensor network data and inverse modeling. The mean relative difference (MRD) of soil water content and saturation degree were used to describe spatial soil water content variability. The MRDs of soil water content were positively correlated with the θ_s and n parameters and negatively correlated with the α and K_s parameters of the van Genuchten–Mualem model.