Newer urban soils, frequently composed of several types of anthropogenic materials, may contain basic oxygen furnace (BOF) slag, which is a steel industry byproduct and considered a potential alternative material for road construction. An understanding of the flow and solute transfer processes through urban soils thus requires hydraulic characterization of these materials. The BEST (Beerkan Estimation of Soil Transfer Parameters) algorithm serves to estimate the full set of unsaturated soil properties by means of conducting an inverse analysis of Beerkan water infiltration data. This study aimed at characterizing unsaturated hydraulic properties of the BOF slag and its evolution during a 1‐yr period through water infiltration experiments and use of an adapted BEST method for inverse analysis. Results indicate the evolution with time of BOF slag hydraulic parameters due to their physicochemical changes when exposed to rainfall events. Moreover, the findings of this study highlight the initial spatial variability of hydrodynamic characteristics, which after a certain period shifts to mostly homogeneous behavior. This study has contributed to the hydrodynamic characterization of BOF slag by providing hydraulic conductivity and water retention curves, as required for modeling water and thus solute transfer processes vs. time, which is relevant to BOF slag reuse and environmental considerations.

Abstract. In this paper, we present and analyze a novel global database of soil infiltration measurements, the Soil Water Infiltration Global (SWIG) database. In total, 5023 infiltration curves were collected across all continents in the SWIG database. These data were either provided and quality checked by the scientists who performed the experiments or they were digitized from published articles. Data from 54 different countries were included in the database with major contributions from Iran, China, and the USA. In addition to its extensive geographical coverage, the collected infiltration curves cover research from 1976 to late 2017. Basic information on measurement location and method, soil properties, and land use was gathered along with the infiltration data, making the database valuable for the development of pedotransfer functions (PTFs) for estimating soil hydraulic properties, for the evaluation of infiltration measurement methods, and for developing and validating infiltration models. Soil textural information (clay, silt, and sand content) is available for 3842 out of 5023 infiltration measurements (∼ 76%) covering nearly all soil USDA textural classes except for the sandy clay and silt classes. Information on land use is available for 76 % of the experimental sites with agricultural land use as the dominant type (∼ 40%). We are convinced that the SWIG database will allow for a better parameterization of the infiltration process in land surface models and for testing infiltration models. All collected data and related soil characteristics are provided online in *.xlsx and *.csv formats for reference, and we add a disclaimer that the database is for public domain use only and can be copied freely by referencing it. Supplementary data are available at https://doi.org/10.1594/PANGAEA.885492 (Rahmati et al., 2018). Data quality assessment is strongly advised prior to any use of this database. Finally, we would like to encourage scientists to extend and update the SWIG database by uploading new data to it.

In the vadose zone, preferential flow and transport are much more common than uniform water flow and solute transport. In recent decades, several models have been developed for preferential water flow and physical nonequilibrium solute transport. Among these models, the dual-permeability approach is an interesting tool for the conceptualization and modeling of preferential flow. However, this approach has been mainly studied from a numerical point of view. In this study, we developed a new analytical model for water infiltration into dual-permeability soils. The model is based on the analytical model originally proposed for single-permeability soils. The proposed model relies on the assumption that the water exchange rate at the interface between the matrix and fast-flow regions does not change cumulative infiltration at the soil surface, so that the total cumulative infiltration can be set equal to the sum of independent cumulative infiltrations into each region. This assumption was investigated using numerically generated data. The proposed analytical model was then used to evaluate the effects of fast-flow region hydraulic properties and hydraulic conditions on total cumulative infiltration for the case of single-and multi-tension water infiltration experiments. Finally, both single-and dual-permeability models were evaluated with respect to their ability to fit experimental data and associated problems of non-uniqueness in optimized parameters. The proposed model could serve as a new tool for modeling and characterizing preferential flow in the vadose zone.Abbreviations: BOF, basic oxygen furnace; CVRMSE, coefficient of variation of the root mean square error;

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