Water Retention Curve

The soil hydraulic parameters for analyzing soil water movement can be determined by fitting a soil water retention curve to a certain function, i.e., a soil hydraulic model. For this purpose, the program "SWRC Fit," which performs nonlinear fitting of soil water retention curves to 5 models by Levenberg-Marquardt method, was developed. The five models are the Brooks and Corey model, the van Genuchten model, Kosugi's log-normal pore-size distribution model, Durner's bimodal pore-size distribution model, and a bimodal log-normal pore-size distribution model propose in this study. This program automatically determines all the necessary conditions for the nonlinear fitting, such as the initial estimate of the parameters, and, therefore, users can simply input the soil water retention data to obtain the necessary parameters. The program can be executed directly from a web page at http://purl.org/net/swrc/ ; a client version of the software written in numeric calculatio...

The relations between soil pore structure induced by tillage and infiltration play an important role in flow characteristics of water and solutes in soil. In this study, we assessed the effect of long-term use of various tillage systems on pore size distribution, areal porosity, stained (flow-active) porosity and infiltration of silt loam Eutric Fluvisol. Tillage treatments were: (1) ploughing to

An experimental device was developed to monitor the field soil suction using miniature tensiometer. This device consists of a double tube system that ensures a good contact between the tensiometer and the soil surface at the bottom of the testing borehole. This system also ensures the tensiometer periodical retrieving without disturbing the surrounding soil. This device was used to monitor the soil suction at the site of Boissy-le-Ch\^atel, France. The measurement was performed at two depths (25 and 45 cm) during two months (May and June 2004). The recorded suction data are analyzed by comparing with the volumetric water content data recorded using TDR (Time Domain Reflectometer) probes as well as the meteorological data. A good agreement between these results was observed, showing a satisfactory performance of the developed device.

In assessing the impact of climate change on infrastructure, it is essential to consider the interactions between the atmosphere, vegetation and the near-surface soil. This paper presents an overview of these processes, focusing on recent advances from the literature and those made by members of COST Action TU1202 – Impacts of climate change on engineered slopes for infrastructure. Climate-and vegetation-driven processes (suction generation, erosion, desiccation cracking, freeze– thaw effects) are expected to change in incidence and severity, which will affect the stability of new and existing infrastructure slopes. This paper identifies the climate-and vegetation-driven processes that are of greatest concern, the suite of known unknowns that require further research, and lists key aspect that should be considered for the design of engineered transport infrastructure slopes in the context of climate change.

In order to predict volumetric water content, it is necessary to know the water retention curve in the soil, as well as the hydraulic conductivity function. These functions depend on parameters related to the soil physical characteristic such as texture. It is in this sense that the aim of this work is to compare the three versions of the Luus-Jaakola method.

In order to obtain the output hydrograph, classical surface hydrology works with models that regard infiltration mainly as a loss. For this reason, traditional software built upon this premise does not deliver water retention curves as a function of time. This work intends to model the infiltration process in a more accurate way in accordance with the other processes being

A century of research focused primarily on agricultural soils has largely ignored stony soils, which dominate some forests and are poorly understood in terms of the stone influence on soil hydraulic properties. Motivated by this knowledge gap, we quantified the influence of soil-containing stone fragments on bulk soil hydraulic properties by determining the water retention curve (WRC) of soil, stone and stone-soil mixtures with varied volumetric stone content. The measured WRC for seven different stone types based on their composition showed maximum and minimum saturated water contents of 0.55 m 3 m −3 in pumice and 0.025 m 3 m −3 in fine sandstone, respectively. The stony soil water retention function was measured using the simplified evaporation method. Contrasting scenarios were studied considering a broad range of stone inclusions; (i) negligibly porous, (ii) significantly porous but less porous than the background soil, (iii) more porous than the background soil. An averaging scheme to describe the WRC of stony soil was proposed based on the individual WRC of the background and stone inclusion which was in good agreement with the experimental data. The HYDRUS-3D model was also employed to simulate the evaporation experiment used for the WRC measurements. The model simulations supported the basic assumptions of the proposed averaging scheme.

In order to obtain the output hydrograph, classical surface hydrology works with models that regard infiltration mainly as a loss. For this reason, traditional software built upon this premise does not deliver water retention curves as a function of time. This work intends to model the infiltration process in a more accurate way in accordance with the other processes being

Continuous mathematical expressions of the soil hydraulic functions, namely, the water retention curve (WRC) and the relative hydraulic conductivity function (RHC), are indispensable for the solution of the equations describing flow processes in soils. The WRC model of Brooks and Corey is a widely used empirical, easy to derive but discontinuous expression that introduces the pore size distribution index, λ,

A model capable of describing the suction-induced consolidation curve (void ratio function) and water retention curve (WRC) of highly compressible materials (HCM) is developed, validated, and finally applied to describe the WRC of deinking by-products (DBP). DBP are a highly compressible by-product of paper recycling used in geoenvironmental applications. Validation is conducted by modelling the WRC and the void ratio function for a well documented silty sand from Saskatchewan, Canada. The WRC and void ratio function were used to predict its hydraulic conductivity function (k-function). The water content, suction, and volumetric deformation data of DBP are obtained using an experimental technique that allows determination of the WRCs of HCMs that is suitable for prediction of the DBP k-function. The results show that volumetric water contents are underestimated if volume changes are not accounted for, leading to inaccuracies in the WRCs, thus inaccurately predicted k-functions. It i...

Soil pore characteristics can have great impact on plant growt and environment. A study was conducted to evaluate the efects of different land use on porosity, pore size distribution (PSD) and soil water retention (SWR) of Fluvic Phaeozem in the Kolubara River valley, Serbia. The land use treatments included: natural forest, native meadow, and arable land managed in the same way for more than 100 years. Disturbed and intact soil samples were collected from three soil profiles at each of the three different land use types from depths of 0–15, 15–30 and 30–45 cm. The capillary rise equation was used to estimate effective pore sizes from water retention measurements. Pressure cells are used to mesure water retention in the water potential range from –33 to –1500 kPa. The bulk density (BD) was significantly (P < 0.05) larger for meadow (1.48–1.49 g cm–3) and arable land (1.28–1.42 g cm–3) than forest (0.99–1.29 g cm–3) at the top 30 cm of soil. There was no significant difference in BD between meadow and arable land in the subsurface soil layer (15–30 cm). Depending upon the increases in BD and disruption of pores by mowing and tillage management, total porosity decreased accordingly in meadow and arable land. Land use had significant effect on PSD. Volume of macropores (> 30 μm) were significantly higher for forest (10.93–16.19%) than meadow (4.77–5.74%) and arable (4.83–7.81%) land for 0–30 cm soil layer. Among the diferent land use types, forest and arable land had significantly higher mesopores (30–3 μm) volume compared with meadow. Mowing and tillage management significantly decreased volume of micropores < 3 μm diameter size at the 0–30 cm soil depth. The results showed that in the 0–0.15 m and 0.15–0.30 m depth soil layers, forest soils showed a significantly higher the available water capacity compared to meadow and arable lands. The S-index also detected clear differences among land uses. In this study, the soil water retention data are well described by the van Genuchten model. In conclusion, our results showed that total porosity, PSD, and moisture retention significantly changed because of the different management systems in the top 30 cm of soil, which can potentially influence crop yields and ecosystem function.