Modeling Moisture Redistribution of Pulse Drip Irrigation Systems by Soil and System Parameters: New Regression-based Approaches

One of the strategies for increasing water use efficiency and reducing deep percolation drip irrigation systems is considering the patterns of moisture redistribution after cut-offing the irrigation process. An experimental study was conducted in the present research to evaluate the moisture redistribution process under surface and subsurface pulse drip irrigation systems and developing new regression-based methodologies for estimating moisture redistribution dimensions using both the soil and system parameters together. A physical model was made and the experiments were performed on three different types of soil texture (light, medium, and heavy) with three emitter flow rates (2, 4, and 6 lit/hr) in three emitter installation depths (0, 15, and 30 cm). The experiments were conducted for both continuous (CI) and pulse (PI) irrigation modes. The results showed that significant amounts of wetting dimensions and wetted area of the moisture bulb are related to post-cut-offing stage. Then, using the nonlinear regression analysis, several models were proposed to estimate the horizontal and vertical redistribution pattern as well as the wetted area (upper and lower parts of the emitter). The comparison of the measured and the stimulated values indicated that the non-linear regression models simulated the parameters associated with redistribution, accurately.

Moisture Redistribution in Full-Scale Wood-Frame Wall Assemblies: Measurements and Engineering Approximation

A counter-balanced mass measurement system was constructed to allow measurement of water loss from a full-scale wood-framed wall assembly. Water was injected onto a localized area of paper towel adjacent to the oriented strand board (OSB) wall sheathing. Moisture pins in the OSB and relative humidity/temperature sensors inside the insulated wall cavity monitored conditions as the wall dried out. The wetted OSB area’s moisture content dropped at a faster rate than the total mass of the wall, indicating moisture redistribution within the wall. A simple model was used to calculate overall moisture redistribution, which was characterized using a near-exponential decay function. This simplification of the inherently three-dimensional physics of moisture redistribution could be incorporated into the one-dimensional hygrothermal models often used in research and engineering practice.

Modelling the moisture redistribution in concrete floors with screed and flooring material with varying properties

Flooring materials and adhesives can be degraded by high pH moisture from e.g. concrete. One way to avoid this degradation, is to dry the concrete and the screed to a sufficient moisture state prior to application of the flooring material. One way to evaluate the moisture state in the materials sensitive to high pH moisture is to calculate the redistribution of moisture in the flooring system from application and onwards. The calculations require substantial knowledge in both moisture related material properties and mass transport calculations in porous materials. The availability of more user-friendly calculations tools stresses the need for a common methodology for both performance and documentation of the calculations. Several input parameters are needed for the calculation, such as boundary conditions, initial moisture distribution and material properties. The most important material properties are the water vapor sorption isotherms (desorption, absorption and scanning) and moisture transport coefficients. This study is investigating the sensitivity of the moisture redistribution calculations to different input parameters, and assumptions needed for the calculation. It is also clarifying what relative humidity intervals that are relevant for different materials in the system and identifying a required accuracy in the different material properties. A first part of round-robin studies with selected cases has been performed to evaluate difference between calculations tools and users.

Soil moisture redistribution and its effect on inter-annual active layer temperature and thickness variations in a dry loess terrace in Adventdalen, Svalbard

High-resolution field data for the period 2000–2014 consisting of active layer and permafrost temperature, active layer soil moisture, and thaw depth progression from the UNISCALM research site in Adventdalen, Svalbard, is combined with a physically based coupled cryotic and hydrogeological model to investigate active layer dynamics. The site is a loess-covered river terrace characterized by dry conditions with little to no summer infiltration and an unsaturated active layer. A range of soil moisture characteristic curves consistent with loess sediments is considered and their effects on ice and moisture redistribution, heat flux, energy storage through latent heat transfer, and active layer thickness is investigated and quantified based on hydro-climatic site conditions. Results show that soil moisture retention characteristics exhibit notable control on ice distribution and circulation within the active layer through cryosuction and are subject to seasonal variability and site-specific surface temperature variations. The retention characteristics also impact unfrozen water and ice content in the permafrost. Although these effects lead to differences in thaw progression rates, the resulting inter-annual variability in active layer thickness is not large. Field data analysis reveals that variations in summer degree days do not notably affect the active layer thaw depths; instead, a cumulative winter degree day index is found to more significantly control inter-annual active layer thickness variation at this site. A tendency of increasing winter temperatures is found to cause a general warming of the subsurface down to 10 m depth (0.05 to 0.26 °C yr−1, observed and modelled) including an increasing active layer thickness (0.8 cm yr−1, observed and 0.3 to 0.8 cm yr−1, modelled) during the 14-year study period.