Soil hydraulic properties estimation from one‐dimensional infiltration experiments using characteristic time concept

Many different equations ranging from simple empirical to semi‐analytical solutions of the Richards equation have been proposed for quantitative description of water infiltration into variably saturated soils. The sorptivity, S, and the saturated hydraulic conductivity, Ks, in these equations are typically unknown and have to be estimated from measured data. In this paper, we use so‐called characteristic time (tchar) to design a new method, referred to as the characteristic time method (CTM) that estimates S, and Ks, from one‐dimensional (1D) cumulative infiltration data. We demonstrate the usefulness and power of the CTM by comparing it with a suite of existing methods using synthetic cumulative infiltration data simulated by HYDRUS‐1D for 12 synthetic soils reflecting different USDA textural classes, as well as experimental data selected from the Soil Water Infiltration Global (SWIG) database. Results demonstrate that the inferred values of S and Ks are in excellent agreement with their theoretical values used in the synthetically simulated infiltration experiments with Nash–Sutcliffe criterion close to unity and RMSE values of 0.04 cm h−1/2 and 0.05 cm h−1, respectively. The CTM also showed very high accuracy when applied on synthetic data with added measurement noise, as well as robustness when applied to experimental data. Unlike previously published methods, the CTM does not require knowledge of the time validity of the applied semi‐analytical solution for infiltration and, therefore, is applicable to infiltrations with durations from 5 min to several days. A script written in Python of the CTM method is provided in the supplemental material

Recuperação em área de empréstimo usada para construção de usina hidrelétrica Recovery of nativa area used for construction of hydroelectric power station

A recuperação de áreas de empréstimo usada para construção de hidrelétricas é um processo lento que requer o uso de plantas de cobertura, como fonte de matéria orgânica e a aplicação de nutrientes e corretivos como condicionadores dos atributos do solo. Portanto, objetivou-se, com este trabalho, estudar a recuperação de atributos físicos do subsolo de um Latossolo Vermelho distrófico, utilizado no terrapleno e fundação da Usina Hidrelétrica de Ilha Solteira, SP. O delineamento utilizado foi em blocos casualizados com oito tratamentos e quatro repetições. A pesquisa foi implantada em 1992. Os tratamentos se constituíram do uso de adubos verdes, braquiária e correção do solo. Após 13 anos foram avaliados: porosidade total do solo, macroporosidade, microporosidade, densidade do solo, estabilidade de agregados, resistência do solo à penetração, teor de matéria orgânica e produção de matéria seca da braquiária. Os tratamentos adotados estão recuperando, de forma lenta, os atributos físicos do subsolo exposto. Os efeitos da recuperação do solo estão atingindo a profundidade de 0-0,10 m.<br>The recovery of native area used in hydroelectric power station construction is a slow process, and it requires the use of covering plant as a source of organic matter, application of nutrients and amendments as soil conditioner. Thus, this study has the objective to study the recovery of physical attribute of subsoil in a distrophic Red Latosol, used in the embankment and foundation of Hydroelectric Power Station, Ilha Solteira, São Paulo, Brazil. The design used was randomized blocks with eight treatments and four replications. The research started in 1992. The treatments consisted of green manure, pasture and soil amendment. After 13 years, total porosity, macroporosity, microporosity, bulk density, aggregate stability, resistance to penetration, organic matter of soil and dry matter of pasture production were evaluated. The adopted treatments are slowly contributing towards recovery of physical attributes of exposed subsoil. The effects of the soil recovery are reaching 0-0.10 m depth