See the Complete Report at the Project Website

ACCOMPLISHMENTS – W-1188, 2007

See the complete Report at the Project Website

OBJECTIVE 1: To develop and improved understanding of the fundamental soil physical properties and processes governing mass and energy transport, and the biogeochemical interactions these mediate.

Interrelated, biotic and abiotic processes were examined at four sites in the northern Mojave Desert by University of Nevada. Infiltration through Av horizons evolves from a matrix-dominated process on the younger soils to a preferential flow-dominated process on older surfaces. USDA Salinitiy Lab worked on models for colloid and microorganism transport and retention in porous media. Experimentsand models demonstrated that much greater retention is possible in the smallest regions of the pore space that are associated with lower flow rates.WashingtonStateUniversityshowed that transient flow mobilized more colloids than steady-state flow. Mechanical straining of colloids was partly responsible for the smaller colloid mobilization in the fine than in the coarse sands. Larger flow rates led to increased colloid mobilization and europium elution.Wyoming developed a new model based on a noniterative solution of the Richards equation. It calculates soil water flow heat transport, and soil water freezing for grid cells at the watershed level.The fate and transport of 17-estradiol (E2) and testosterone (T) in soils were investigated by North Dakota. Soil water content and organic matter were significant in explaining hormone distributions in the soil. Soil humic substances can immobilize the majority of hormones.UC Riverside initiated an investigation on the fate of pharmaceutical products applied to turfgrass with reclaimed wastewater.A new equilibrium equation was derived to predict the ion distribution between the exchanger and solution phases.Scientists from the Batelle Pacific Northwest Division compared different model approaches to the saturation-dependent anisotropy. The tensorial connectivity-tortuosity (TCT) model had the smallest average error.Iowa scientists tested diffusion-based coupled soil heat and water transfer theory.Work is planned on coupled water and heat transport under transient conditions.Near-surface soil heat fluxes account for as much as 80% of net radiation as the evaporation zone proceeds below the surface.A lattice-Boltzmann model approach was chosen by Tucsonto simulatemicroscopic liquid-air interphase processes. Moreover, dehydration studies on initiation and evolution of surface crack networks in active clay soils were performed in conjunction with X-Ray Computed Tomography (CT) observations.Mixing bentonite with sand- or silt-like materials reduces susceptibility to formation of desiccation cracks.UC Davis combined field experiments and numerical simulations to study effects of various irrigation and fertigation systems. Soil salinity measurements showed considerable leaching around drip lines due to spatially-varying soil wetting patterns that occur under drip irrigation.UtahStatetested water retention and gas diffusion in 3 different particle-sized media.Their focus is on maintaining plant health in the absence of gravity. Highly localized non-uniform water contents may lead to potential problems with oxygen supply to plant roots within zones of higher water content.Oregonproposed a mechanism for enhanced evaporation consisting of thermally driven convective venting of the fractures occurring at night. Salt is depositing in the smaller pores and surface precipitation occurs over the area of small pores. Thus, the surface patchiness is associated with the location of smaller pores.CaliforniaStateUniversity characterized groundwater flow in the fractured granite aquifers in the foothill areas of western Sierra Nevada, Madera County of California. Variations in the results suggested that both the flow patterns and the model parameters were scale-dependent and related to heterogeneity within the aquifer.Montana works on the critical drivers that govern catchment water, carbon, and gas behavior and movement and how they are integrated by larger-scale measurements. This research will address the landscape controls on riparian buffering of the quantity, quality, and timing of water delivered from alpine headwater watersheds.

OBJECTIVE 2: To develop and evaluate instrumentation and methods of analysis for characterizing mass and energy transport in soils at different scales

Nevada has been examining Raman Spectra Fiber Optic Distributed Temperature Sensing.Theyanalyzed dual-probe heat-pulse (DPHP) data for estimating volumetric water content of near-surface materials.The variability of ET rate for moderately dense desert shrubland contributed to over 78% of the variance in total ground-water discharge.WashingtonStateUniversitydetermined the effective vapor diffusion coefficients and the diffusive resistances through wheat residue layers.They also evaluated the effect of wildfire on soil water repellency. Remotely sensed hyperspectral imagery was collected to map post-wildfire ground cover and soil condition.An electric circuit model was developed by Wyomingfor the Hydra probe sensor measuring real permittivity, imaginary permittivity and temperature. The real permittivity can be converted into soil water content by using a soil-specific calibration.USDA-ARS, Minnesota, contribute to a better understanding of the surface energy balance by measuring apparent thermal conductivity (a) and apparent volumetric heat capacity (Ca) which permits accurate monitoring of soil heat flux under freezing and thawing conditions.UC Riverside found that humic substances and dissolved organic matter reduce the surface tension at the liquid-air interface. Capillary pressure is lowered at the same water content in soils containing DOM. HYDRUS now considers the concentration dependence of surface tension and the contact angle dependence of capillary pressure.Pacific Northwest Division performed experiments to study the behavior of radioactive contaminants that escape from corroded tanks. Experimental installations included continuous soil water content monitoring devices.Iowa state examined the effect of low connectivity of intra-granular pores on diffusion and retardation of an inert conservative tracer. Most of the study of systems is completed, starting from equilibrium, and some follow-up studies on dynamic systemshave started.UC Davis usedthe multi-functional heat pulse probe (MFHPP)for measuringcoupled water, heat, and solute transport simultaneously. Neutron computed tomography was applied successfully in a single root water uptake experiment showing spatially-variable soil water content gradients in the rhizosphere.University of Arizona conducted a preliminary image binarization study suitable for CT data. The various methods considerable deviate from each other, some of them underestimating and some of them overestimating measured porosities.UtahStateUniversity evaluated the Penta-needle Heat Pulse Probe (PHPP): It can provide good estimation of 2-D soil water fluxes.Evaluation of self filling tensiometers showed that they were not suitable for forest soil application under freeze/thaw conditions.CaliforniaStateUniversity contributed to a better understanding of the San JoaquinRiver regional hydrology. Stable isotope analysis in different groundwater zones revealed that groundwater collected near to the river showed more depletion than samples taken form the river.Montanadeveloped a software to generate synthetic Time Domain Reflectometry (TDR) waveforms for evaluating probes,and predicting travel time analysis.Montana is evaluating flood generation, streamwater residence times, sources and pathways of runoff, riparian buffering of hillslope runoff, water quality dynamics, and the heterogeneity of CO2 generation and flux across watersheds.KansasStateUniversitycontributed to the volumetric characterization of the spatial sensitivity of the DPHP method. Moreover, diurnal water-table fluctuations observed in shallow wells in vegetated riparian zones are a diagnostic indicator of groundwater consumption by evapotranspiration (ETG).

OBJECTIVE 3: To develop and evaluate scale-appropriate methodologies for the management of soil and water resources

Nevada contributed to the restoration of disturbed lands in the Mojave Desert; particularly re-vegetation of military lands. The optimal macroscopic hydraulic conductivities for both horizontally and vertically heterogeneous soils depended on the pressure head conditions at the land surface.USDA Salinity Lab implemented a nutrient management plan using cyclic and blending irrigation strategies for dairy lagoon water application (interagency project with EPA).Contaminant concentrations (salts, heavy metals, nutrients, hormones, and antibiotics) were quantified in various lagoon water samples.WashingtonStateused DEMs to calculate topographic and hydrologic parameters that served as inputs to WEPP. The model results of sediment yields and runoffs were compared with field observations, and showed that different resolutions cause considerable differences in erosion modeling results.Wyoming scientists initiated a study on the leaching potential of trace elements like Arsenic and Selenium from Coalbed Methane water disposal ponds. Coalbed Methane extraction involves pumping from coal seams to reduce the water pressure and release the gas. The marginal quality water is generally released into streams and surface ponds.Three different methods for delineatingnitrogen management zones were tested by North Dakota. Even though this field site had significant variation in soil ECa, topography, and soil color, zone management seemed to result in uniformity of yield across the site.UC Riverside investigated metal uptake of corn in biosolid-treated sand media. The effect of particle-size distribution on uptake of Cu and Ni was less pronounced than that on Cd and Zn, while the uptake of Cr and Pb were dominated by their chemical speciation of the biosolids.Pacific Northwest Division investigated the saturation-dependent anisotropy of unsaturated hydraulic conductivity. The model showed that the anisotropic coefficient of any one of the fluids depends only on the saturation of the fluid being considered but not on saturation of other fluids.IowaStateestimated the distribution and extent of drainage across the U.S.Long-term simulations suggest that at least half of the N loss reduction goal could be met by reducing N application rates.Model simulations demonstrated how to reduce losses of NO3-N in subsurface drainage.No-till practice significantly increased SOC storage and reduced nitrate–Nleaching rate, but slightly decreased crop yield and increased N2O emissions.Arizona integrated easily obtainable data with hydraulic property data to generate heterogeneous soil hydraulic parameters for a field injection test and 3-D modeling of a contaminant plume. The parameter estimates were used to simulate a field injection experiment. Good agreement was obtained between the simulated and observed moisture contents.UC Davis predicted thewater-content dependent soil moisture variability by stochastic analysis of the unsaturated Brooks-Corey flow in heterogeneous soils for eleven textural classes. The  parameter, which describes the pore-size distribution of soils, controls the maximum value of the soil moisture standard deviation. UtahStateUniversity developed a methodology to describe the process of obtaining soil properties from maps of electrical conductivity. Correlating vegetation maps with the EMI map to link hydrological properties with vegetation community structure is further pursued.UC Riverside coupled ageochemical modeling code with HYDRUS to simulate a broad range of low-temperature biogeochemical reactions in water, soil and ground water systems. A new module CW2D for biochemical transformation and degradation processes in subsurface flow constructed wetlands has been released.A model that can consider transport of solutes facilitated by the presence of colloids has also been developed. Numerical models were applied to simulate transport of various contaminants.A major upgrade of HYDRUS-2D/MESHGEN-2D software package called HYDRUS (2D/3D) was released.CaliforniaStateUniversity applied remote sensing information and the DEM for estimating spatio-temporal snow depth behavior for the UpperSan JoaquinRiver watershed above Friant Dam.Montana found that a vegetated cap system designed to prevent leaching of meteoric water failed to function as desired during both years of available data.A method was developed to examine the impact of geographic location and spatial distribution of land use/land cover change on the spatial, seasonal, and temporal patterns of streamwater nitrogen (N).Upon KBr tracer application, Kentucky identified spatial correlation lengths for anion concentration of approximately 1 m. At the landscape scale, surface soil water content is spatially closely associated with profile water storage. Relations between soil texture and surface soil moisture strongly vary with spatial scale, support, and distance.Texas A&M adopted a multi-facet approach to field soil hydraulic property characterization including: a bottom-up approach, a top-down approach, and an artificial neural network approach.UC Davis initiated an extensive characterization and geostatistical analysis of the geology, hydraulic properties, and nitrogen distribution in a 16 m deep vadose zone across a nectarine orchard.Unsaturated flow and transport simulations for both types of heterogeneity representations of the vadose zone were implemented with HYDRUS. The flow velocity distribution in the MPHR-based simulations is more variable than in the SFA-based simulations.

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