1,721,022 research outputs found
Infiltration Measurements for Soil Hydraulic Characterization
Get PDFThis book summarises the main results of many contributions from researchers worldwide who have used the water infiltration process to characterize soil in the field. Determining soil hydrodynamic properties is essential to interpret and simulate the hydrological processes of economic and environmental interest. This book can be used as a guide to soil hydraulic characterization and in addition it gives a complete description of the treated techniques, including an outline of the most significant research results, with the main points that still needing development and improvement
Testing a new automated single ring infiltrometer for Beerkan infiltration experiments
No full textThe Beerkan method along with BEST algorithms is an alternative technique to conventional laboratory or field measurements for rapid and low-cost estimation of soil hydraulic properties. The Beerkan method is simple to conduct but requires an operator to repeatedly pour known volumes of water through a ring positioned at the soil surface. A cheap infiltrometer equipped with a data acquisition system was recently designed to automate Beerkan infiltration experiments. In this paper, the current prototype of the automated infiltrometer was tested to validate its applicability to the Beerkan infiltration experiment under several experimental circumstances. In addition, the accuracy of the estimated saturated soil hydraulic conductivity, K-s, and sorptivity, S, was assessed by applying different BEST algorithms to the data obtained with the infiltrometer. At this purpose, both analytically generated and real experimental data were used. The analytical assessment showed that the use of the infiltrometer along with BEST methods could lead to accurate estimates of the considered soil properties in most cases, which validated the design of the infiltrometer and its combination with BEST algorithms. Loamy soils and high initial water contents led to misestimating K-s and S or to failure of BEST algorithms, but advices about the infiltrometer design were developed to alleviate such problems. A comparison between the automated procedure and the original BEST procedure was made at three field sites in Sicily (Italy). Other experiments were carried out in an infiltration basin located in the pumping well field of Crepieux-Charmy (Lyon, France), in order to assess the ability of the automated infiltrometer to check clogging effects on K-s. The experiments showed that the automatic data collection increased measurement speed, allowed a more efficient data handling and analysis, and reduced sensitivity of the calculated hydraulic parameters on the applied BEST algorithm. (C) 2015 Elsevier B.V. All rights reserved
Beerkan multi-runs for characterizing water infiltration and spatial variability of soil hydraulic properties across scales
No full textA method is presented for characterizing the spatial variability of water infiltration and soil hydraulic properties at the transect and field scales. The method involves monitoring a set of 10 Beerkan runs distributed over a 1-m length of soil, and running BEST (Beerkan estimation of soil transfer parameters) methods to derive hydraulic parameters. The Beerkan multi-runs (BMR) method provides a significant amount of data at the transect scale, allowing the determination of correlations between water infiltration variables and hydraulic parameters, and the detection of specific runs affected by preferential flow or water repellence. The realization of several BMRs at several transects on the same site allows comparison of the variation between locations (spatial variability at the field scale) and at the transect scale (spatial variability at the metre scale), using analysis of variance. From the results, we determined the spatial variability of water infiltration and hydraulic parameters as well as its characteristic scale (transect versus field)
Laboratory testing of Beerkan infiltration experiments for assessing the role of soil sealing on water infiltration
No full textSoil surface sealing is a major cause of decreased infiltration rates and increased surface runoff and erosion during a rainstorm. The objective of this paper is to quantify the effect of surface sealing on infiltration for 3 layered soils with different textures for the upper layer and investigate the capability of BEST procedure to catch the formation of the seal and related consequences on water infiltration. Rainfall experiments were carried out to induce the formation of the seal. Meanwhile, Beerkan infiltration runs were carried out pouring water at different distances from the soil surface (BEST-H versus BEST-L runs, with a High and Low water pouring heights, respectively) for the same type of layered soils. Then, we determined saturated soil hydraulic conductivity, Ks, values from rainfall simulation and Beerkan infiltration experiments. Rainfall simulations carried out on soil layers having different depths allowed to demonstrate that infiltration processes were mainly driven by the seal and that Ks estimates were representative of the seal. Mean Ks values, estimated for the late-phase, ranged from 13.9 to 26.2 mm h−1. Soil sealing induced an increase in soil bulk density by 38.7 to 42.1%, depending on the type of soil. Rainfall-deduced Ks data were used as target values and compared with those estimated by the Beerkan runs. BEST-H runs proved more appropriate than BEST-L runs, those last triggering no seal formation. The predictive potential of the three BEST algorithms (BEST-slope, BEST-intercept and BEST-steady) to yield a proper Ks estimate for the seal was also investigated. BEST-slope yielded negative Ks values in 87% of the cases for BEST-H runs. Positive values were obtained in 100% of the cases with BEST-steady and BEST-intercept. However, poorer fits were obtained with the latter algorithm. The comparison of Ks estimates with rainfall-deduced estimates allowed to identify BEST-steady algorithm with BEST-H run as the best combination. The method proposed in this study could be used to easily measure the seal's saturated hydraulic conductivity of an initially undisturbed bare soil directly impacted by water with minimal experimental efforts, using small volumes of water and easily transportable equipment
Comparing Beerkan infiltration tests with rainfall simulation experiments for hydraulic characterization of a sandy-loam soil
No full textSaturated soil hydraulic conductivity, K-s, data collected by ponding infiltrometer methods and usual experimental procedures could be unusable for interpreting field hydrological processes and particularly rainfall infiltration. The K-s values determined by an infiltrometer experiment carried out by applying water at a relatively large distance from the soil surface could however be more appropriate to explain surface runoff generation phenomena during intense rainfall events. In this study, a link between rainfall simulation and ponding infiltrometer experiments was established for a sandy-loam soil. The height of water pouring for the infiltrometer run was chosen, establishing a similarity between the gravitational potential energy of the applied water, E-p, and the rainfall kinetic energy, E-k. To test the soundness of this procedure, the soil was sampled with the Beerkan estimation of soil transfer parameters procedure of soil hydraulic characterization and two heights of water pouring (0.03m, i.e., usual procedure, and 0.34m, yielding E-p=E-k). Then, a comparison between experimental steady-state infiltration rates, i(sR), measured with rainfall simulation experiments determining runoff production and K-s values for the two water pouring heights was carried out in order to discriminate between theoretically possible (i(sR)K(s)) and impossible (i(sR
Interweaving monitoring activities and model development towards enhancing knowledge of the soil-plant-atmosphere continuum
No full textThe guest editors summarize the advances and challenges associated with monitoring and modeling of the soil–plant–atmosphere continuum. They introduce the contributions in the special section, with an emphasis on the scale addressed in each study. The study of water pathways from the soil to the atmosphere through plants—the so-called soil–plant–atmosphere continuum (SPAC)—has always been central to agronomy, hydrology, plant physiology, and other disciplines, using a wide range of approaches and tools. In recent years, we have been witnessing a rapid expansion of interweaving monitoring activities and model development related to SPAC in climatic, ecological, and applications other than the traditional agrohydrological, and it is therefore timely to review the current status of this topic and outline future directions of research. The initiative for the special section of Vadose Zone Journal on SPAC emanated from several sessions we recently organized in international conferences and meetings. With a view to the specific research questions covered in this special section, this article introduces and reviews SPAC underlying issues and then provides a brief overview of the invited contributions. We have grouped together the 15 contributions under three main sections related to the local, field, and landscape spatial scales of interests. Within these sections, the papers present their innovative results using different measuring techniques (from classic tensiometers and TDR sensors to more advanced and sophisticated equipment based on tomography and geophysics) and different modeling tools (from mechanistic models based on the Richards equation to more parametrically parsimonious hydrologic balance models). They provide a snapshot of the current state of the art while emphasizing the significant progress attained in this field of research. New technological developments and applications are also highlighted
Reduction of feasible parameter space of the inverted soil hydraulic parameters sets for Kosugi model.
No full textEffective soil hydraulic parameters of Soil Vegetation Atmosphere Transfer (SVAT) models can be derived in a cost-efficient way by inverse modeling. Nevertheless, a serious drawback of SVAT models based on Richards??? equation is that they require as many as five unexploited correlated hydraulic parameters. To reduce the feasible parameter space, we propose a method to prevent nonphysical combinations of soil hydraulic parameter sets obtained by optimization. We adopt Kosugi???s (1994) soil hydraulic analytical model because it enables the feasible parameter space to be reduced by predicting parameter ?? from hm , which are the variance and mean of the log-transformed soil pore radius, respectively. To further decrease the parameter space we derive two models to predict saturated hydraulic conductivity, Ks, from three or four Kosugi's soil water retention parameters, respectively. These two models are based on the combination of the Hagen-Poiseuille and Darcy equations which employ three semi-empirical parameters (???1 , ???2 and ???3) calibrated on large UNSODA and HYPRES databases. Our derived models are compared to a version of the Mishra and Parker (1990) Ks model being modified to account for the parameters of Kosugi???s relationships. The results show that the uncertainties of the developed Ks model are comparable to the uncertainties of Ks measurements. Moreover, the developed Ks model outperforms the Mishra and Parker model. Therefore, the developed method will enable to substantially reduce the feasible range of the inverted Kosugi???s hydraulic parameters
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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