Simulating preferential soil water flow and tracer transport using the Lagrangian Soil Water and Solute Transport Model

We propose an alternative model concept to represent rainfall-driven soil water dynamics and especially preferential water flow and solute transport in the vadose zone. Our LAST-Model (Lagrangian Soil Water and Solute Transport) is based on a Lagrangian perspective of the movement of water particles (Zehe and Jackisch, 2016) carrying a solute mass through the subsurface which is separated into a soil matrix domain and a preferential flow domain. The preferential flow domain relies on observable field data like the average number of macropores of a given diameter, their hydraulic properties and their vertical length distribution. These data may be derived either from field observations or by inverse modelling using tracer data. Parameterization of the soil matrix domain requires soil hydraulic functions which determine the parameters of the water particle movement and particularly the distribution of flow velocities in different pore sizes. Infiltration into the matrix and the macropores depends on their respective moisture state, and subsequently macropores are gradually filled. Macropores and matrix interact through diffusive mixing of water and solutes between the two flow domains, which again depends on their water content and matric potential at the considered depths. The LAST-Model is evaluated using tracer profiles and macropore data obtained at four different study sites in the Weiherbach catchment in southern Germany and additionally compared against simulations using HYDRUS 1-D as a benchmark model. While both models show qual performance at two matrix-flow-dominated sites, simulations with LAST are in better accordance with the fingerprints of preferential flow at the two other sites compared to HYDRUS 1-D. These findings generally corroborate the feasibility of the model concept and particularly the implemented representation of macropore flow and macropore–matrix exchange. We thus conclude that the LAST-Model approach provides a useful and alternative framework for (a) simulating rainfall-driven soil water and solute dynamics and fingerprints of preferential flow as well as (b) linking model approaches and field experiments. We also suggest that the Lagrangian perspective offers promising opportunities to quantify water ages and to evaluate travel and residence times of water and solutes by a simple age tagging of particles entering and leaving the model domain

A topographic index explaining hydrological similarity by accounting for the joint controls of runoff formation

Surface topography is an important source of information about the functioning and form of a hydrological landscape. Because of its key role in explaining hydrological processes and structures, and also because of its wide availability at good resolution in the form of digital elevation models (DEMs), it is frequently used to inform hydrological analyses. Not surprisingly, several hydrological indices and models have been proposed for linking geomorphic properties of a landscape with its hydrological functioning; a widely used example is the “height above the nearest drainage” (HAND) index. From an energy-centered perspective HAND reflects the gravitational potential energy of a given unit mass of water located on a hillslope, with the reference level set to the elevation of the nearest corresponding river. Given that potential energy differences are the main drivers for runoff generation, HAND distributions provide important proxies to explain runoff generation in catchments. However, as expressed by the second law of thermodynamics, the driver of a flux explains only one aspect of the runoff generation mechanism, with the driving potential of every flux being depleted via entropy production and dissipative energy loss. In fact, such losses dominate when rainfall becomes runoff, and only a tiny portion of the driving potential energy is actually transformed into the kinetic energy of streamflow. In recognition of this, we derive a topographic index called reduced dissipation per unit length index (rDUNE) by reinterpreting and enhancing HAND following a straightforward thermodynamic argumentation. We compare rDUNE with HAND, and with the frequently used topographic wetness index (TWI), and show that rDUNE provides stronger discrimination of catchments into groups that are similar with respect to their dominant runoff processes. Our analysis indicates that accounting for both the driver and resistance aspects of flux generation provides a promising approach for linking the architecture of a system with its functioning and is hence an appropriate basis for developing similarity indices in hydrology

On how data are partitioned in model development and evaluation: Confronting the elephant in the room to enhance model generalization

This is the final version. Available on open access from Elsevier via the DOI in this recordData availability: No data was used for the research described in the article.Models play a pivotal role in advancing our understanding of Earth's physical nature and environmental systems, aiding in their efficient planning and management. The accuracy and reliability of these models heavily rely on data, which are generally partitioned into subsets for model development and evaluation. Surprisingly, how this partitioning is done is often not justified, even though it determines what model we end up with, how we assess its performance and what decisions we make based on the resulting model outputs. In this study, we shed light on the paramount importance of meticulously considering data partitioning in the model development and evaluation process, and its significant impact on model generalization. We identify flaws in existing data-splitting approaches and propose a forward-looking strategy to effectively confront the “elephant in the room”, leading to improved model generalization capabilities.National Natural Science Foundation of ChinaAustralian Research Council (ARC

Call–English as a Second Language

CALL for English as a second language1 is an interdisciplinary area of inquiry which has been influenced primarily by educational technology (Reiser, 1987) but also by fields such as computational linguistics2 and recently by applied linguistics as well. These related fields contribute diverse epistemologies which shape CALL research questions and methods. The diversity in CALL research can also be explained in part by the current variety of approaches to CALL development and use. Through the 1970s and early 1980s, pedagogical objectives in CALL were focused primarily, although not exclusively, on improving specified areas of learner\u27s grammatical knowledge through approaches borrowed from educational technology (Hart 1981, Hope, Taylor and Pusack 1984, Wyatt 1984). Today, in contrast, CALL is used for a variety of pedagogical objectives through many different types of software such as microworlds (Coleman 1985, Papert 1980), grammar checkers (Hull, Ball, Fox, Levin and McCutchen 1987), pronunciation feedback systems (Anderson-Hseih 1994, Pennington 1991), intelligent tutoring systems (Chanier, Pengelly, Twidale and Self 1992), concordancer programs (Johns 1986, Tribble and Jones 1990), word processing (Pennington 1993), and software for computer-mediated communication (Kaye 1992). These diverse approaches to CALL are predicated on different beliefs about teaching and learning (Higgins 1995, Kenning and Kenning 1990, Sanders and Kenner 1983, Stevens 1992). Rather than reviewing these CALL philosophies, this article will focus on the evolution of research traditions dedicated to the empirical study of CALL use for ESL. Accordingly, the term CALL research is employed to refer to empirical research on the use of CALL

Coincidence Doppler shift lifetime measurements in 73,74^{73,74}Se and 74^{74}Br using the EUROBALL Cluster cube array

Subpicosecond lifetimes of high spin states in the rotational nuclei $^{73}$Se, $^{74}$Se and $^{74}$Br have been measured using the $^{58}$Ni + $^{19}$F compound reaction and the Doppler Shift Attenuation method. Six EUROBALL Cluster detectors arranged in cube geometry allowed us to select the relevant transitions in $\gamma\gamma$ coincidence mode. The high counting statistics achieved in this setup also facilitated the determination of average sidefeeding times, which were found to agree rather well with the results of Monte-Carlo calculations of the particle and $\gamma$-ray evaporation process. The deduced quadrupole strengths and deformations are compared with the results of previous measurements and the predictions of Cranked Shell Model calculations. In $^{74}$Br, a large and constant prolate deformation of $\beta_2$=0.37(1) was found for the presumed $4^+$ and $3^-$ two-quasiparticle bands