Soil water properties are related to crop growth and environmental aspects and are influenced by the degree of soil compaction. The objective of this study was to determine the water infiltration and hydraulic conductivity of saturated soil under field conditions in terms of the compaction degree of two Oxisols under a no-tillage (NT). Two commercial fields were studied in the state of Rio Grande do Sul, Brazil: one a Haplortox after 14 years under NT; the other a Hapludox after seven years under NT. Maps (50 x 30 m) of the levels of mechanical penetration resistance (PR) were drawn based on the kriging method, differentiating three compaction degrees (CD): high, intermediate and low. In each CD area, the infiltration rate (initial and steady-state) and cumulative water infiltration were measured using concentric rings, with six replications, and the saturated hydraulic conductivity (K(&#952;s)) was determined using the Guelph permeameter. Statistical evaluation was performed based on a randomized design, using the least significant difference (LSD) test and regression analysis. The steady-state infiltration rate was not influenced by the compaction degree, with mean values of 3 and 0.39 cm h-1 in the Haplortox and the Hapludox, respectively. In the Haplortox, saturated soil hydraulic conductivity was 26.76 cm h-1 at a low CD and 9.18 cm h-1 at a high CD, whereas in the Hapludox, this value was 5.16 cm h-1 and 1.19 cm h-1 for the low and high CD, respectively. The compaction degree did not affect the initial and steady-state water infiltration rate, nor the cumulative water infiltration for either soil type, although the values were higher for the Haplortox than the Hapludox.<br>As propriedades hídricas do solo relacionam-se com o crescimento das culturas e com aspectos ambientais e são influenciadas pelo estado de compactação do solo. O objetivo deste trabalho foi determinar, em campo, a infiltração de água e a condutividade hidráulica de solo saturado em função do estado de compactação de Latossolos sob sistema plantio direto (SPD). Duas áreas de lavouras comerciais do Rio Grande do Sul com dimensões de 50 x 30 m, foram estudadas: uma em um Latossolo Vermelho distrófico (LVd) cultivado por 14 anos em SPD; e a outra em Latossolo Vermelho distroférrico típico (LVdf) cultivado por sete anos em SPD. Mapas representando níveis de resistência mecânica do solo à penetração (RP) foram confeccionados utilizando-se o método da krigagem e, neles, foram identificados três estados de compactação (EC): maior, intermediário e menor. No campo, sobre cada faixa de EC, foram medidas, em seis repetições, a taxa de infiltração (inicial e estável) e a lâmina infiltrada acumulada de água, com auxílio de anéis concêntricos, e a condutividade hidráulica em solo saturado (K(&#952;s)), com auxílio de permeâmetro de Guelph. A avaliação estatística foi realizada com base no delineamento inteiramente casualizado, empregando o teste da diferença mínima significativa (DMS) e a análise de regressão. A taxa de infiltração estável não variou entre os estados de compactação, com valor médio de 3 cm h-1 no LVd e de 0,39 cm h-1 no LVdf. A condutividade hidráulica do solo saturado para o LVd foi de 26,76 cm h-1 no menor EC e de 9,18 cm h-1 no maior, ao passo que para o LVdf foi de 5,16 e 1,19 cm h-1, respectivamente para a menor e maior compactação. O estado de compactação não interferiu na taxa de infiltração inicial e estável nem na lâmina de água infiltrada acumulada de cada solo, porém os valores foram maiores para o LVd que para o LVdf.

Groundwater use for agricultural purposes has been intensified in the State of Sergipe, mainly in the regions with more serious water shortage from surface sources. However, irrigation is still restricted to small areas like home gardens. In part, this problem is due to lack of studies on characterization of water resources, including availability and quality of groundwaters, detecting the spatial distribution of viable sources of groundwater for different uses. The potential hazards related to soil salinity and sodicity, toxicity of specific ions for crops, and clogging of components of microirrigation systems were evaluated. Physicochemical data of water from 278 deep wells located in Piauí River Basin, in the State of Sergipe, Brazil, were used considering the FAO restriction criteria for irrigation purposes. Maps of spatial distribution of groundwater quality indicators in the watershed were prepared by ordinary kriging procedures. Groundwaters showed good quality for irrigation use, mainly in the center-downstream portion of the river basin. There was a trend in increasing the salt concentration in water from the coast to inland in the Piauí River Basin area. | O uso de água subterrânea para fins agrícolas tem-se intensificado no Estado de Sergipe, sobretudo na região de maior escassez de águas superficiais; no entanto, a irrigação ainda está restrita a pequenas áreas, como hortas familiares, justificado, em parte, pela ausência de estudos de caracterização hídrica, incluindo disponibilidade e qualidade das águas subterrâneas, que permitam o conhecimento da distribuição espacial das fontes de água viáveis para uso. Avaliaram-se os riscos potenciais relativos à salinização e sodificação de solos, à toxicidade de íons específicos às culturas e à obstrução em sistemas de irrigação localizada, a partir de dados secundários de 278 poços localizados na bacia hidrográfica do Rio Piauí, considerando-se os critérios de restrição ao uso da água para irrigação estabelecidos pela FAO. Mapas de risco foram gerados por procedimentos de krigagem ordinária, para as variáveis indicadoras de qualidade da água, que possibilitaram a visualização do comportamento espacial das águas na bacia. Verificou-se que as águas subterrâneas apresentam boas condições para uso na irrigação, principalmente na porção centro-litorânea da bacia, visto que houve tendência de aumento na concentração de sais das águas no sentido centro-cabeceiras.

Este experimento objetivou analisar as alterações no comportamento espacial dos atributos do solo: matéria orgânica (MO), argila dispersa em água (ADA) e grau de floculação (GF) em áreas ocupadas com vegetação natural em regeneração e em pastagem. As amostras de solo foram coletadas na profundidade de 0,0-0,2 m em uma grade amostral com 64 pontos, espaçados 10 m. Os dados foram submetidos à análise descritiva e, em seguida, foi realizada a análise geoestatística. Observaram-se os maiores valores para ADA e os menores valores de GF na área de pastagem. Todos os atributos apresentam dependência espacial para as duas áreas em estudo, com ajuste dos modelos esférico e exponencial. A confecção dos mapas temáticos por meio da krigagem ordinária permitiu melhor visualização da distribuição espacial dos atributos de solo. This experiment aimed to analyze changes in spatial behavior of the attributes of soil: clay dispersed in water (CDW), degree of flocculation (DF) and organic matter (OM) in areas occupied by native vegetation in natural regeneration and pasture. Soil samples were collected at a depth of 0.0-0.2 m in a grid with 64 sampling points, spaced at 10 m. The data were submitted to descriptive and geostatistics analysis. The highest values were observed for the CDW and the lowest values of DF in the pasture. All attributes show spatial dependence for the two areas of study, with adjustment of the spherical and exponential models. The preparation of thematic maps using the ordinary kriging allowed better visualization of the spatial variability of soil attributes.

Understanding the response of groundwater levels in alluvial and sedimentary basin aquifers to climatic variability and human water-resource developments is a key step in many hydrogeological investigations. This study presents an analysis of groundwater response to climate variability from 2000 to 2012 in the Queensland part of the sedimentary Clarence-Moreton Basin, Australia. It contributes to the baseline hydrogeological understanding by identifying the primary groundwater flow pattern, water-level response to climate extremes, and the resulting dynamics of surface-water/groundwater interaction. Groundwater-level measurements from thousands of bores over several decades were analysed using Kriging and nonparametric trend analysis, together with a newly developed three-dimensional geological model. Groundwater-level contours suggest that groundwater flow in the shallow aquifers shows local variations in the close vicinity of streams, notwithstanding general conformance with topographic relief. The trend analysis reveals that climate variability can be quickly reflected in the shallow aquifers of the Clarence-Moreton Basin although the alluvial aquifers have a quicker rainfall response than the sedimentary bedrock formations. The Lockyer Valley alluvium represents the most sensitively responding alluvium in the area, with the highest declining (−0.7 m/year) and ascending (2.1 m/year) Sen’s slope rates during and after the drought period, respectively. Different surface-water/groundwater interaction characteristics were observed in different catchments by studying groundwater-level fluctuations along hydrogeologic cross-sections. The findings of this study lay a foundation for future water-resource management in the study area.

This experiment aimed to analyze changes in spatial behavior of the attributes of soil: clay dispersed in water (CDW), degree of flocculation (DF) and organic matter (OM) in areas occupied by native vegetation in natural regeneration and pasture. Soil samples were collected at a depth of 0.0-0.2 m in a grid with 64 sampling points, spaced at 10 m. The data were submitted to descriptive and geostatistics analysis. The highest values were observed for the CDW and the lowest values of DF in the pasture. All attributes show spatial dependence for the two areas of study, with adjustment of the spherical and exponential models. The preparation of thematic maps using the ordinary kriging allowed better visualization of the spatial variability of soil attributes. | Este experimento objetivou analisar as alterações no comportamento espacial dos atributos do solo: matéria orgânica (MO), argila dispersa em água (ADA) e grau de floculação (GF) em áreas ocupadas com vegetação natural em regeneração e em pastagem. As amostras de solo foram coletadas na profundidade de 0,0-0,2 m em uma grade amostral com 64 pontos, espaçados 10 m. Os dados foram submetidos à análise descritiva e, em seguida, foi realizada a análise geoestatística. Observaram-se os maiores valores para ADA e os menores valores de GF na área de pastagem. Todos os atributos apresentam dependência espacial para as duas áreas em estudo, com ajuste dos modelos esférico e exponencial. A confecção dos mapas temáticos por meio da krigagem ordinária permitiu melhor visualização da distribuição espacial dos atributos de solo.

In most arid areas, due to scarce hydrogeological data, it is a challenge to locate groundwater sources and to meet water demand for residential, irrigation, and mining uses. In this study, an innovative method is presented, using magnetic resonance sounding (MRS), to detect areas suitable as groundwater sources on the Mongolian Plateau. First, a target investigation area was identified with a small number of MRS surveys of potential areas by determining whether aquifers exist, whether the aquifers have relatively large water contents and relaxation times, and whether there are hydraulic connections among the aquifers. Next, an intensive MRS survey (158 points in total) was conducted in the target investigation area, and eight boreholes were drilled. A comparison of the borehole data and MRS data showed that when the MRS data had a high signal-to-noise ratio, the aquifer depth and transmissivity estimated by MRS were associated with a deviation of only 4.85 m from the measured depth, and an uncertainty in transmissivity of 15.53%, respectively. These values indicated that the proposed method is highly accurate. Finally, a kriging interpolation method was used to construct distribution maps of groundwater levels, aquifer thickness, transmissivity, and water yield, based on the borehole and MRS data. The reliability of the results was assessed from several perspectives. The findings showed that this step-by-step approach is an effective method of groundwater source detection in arid areas with scarce hydrogeological data.

Wetlands provide unique goods and services, as habitats of high biodiversity. Hydrology is the principal control on wetland functioning; hence, understanding the water source is fundamental. However, groundwater inflows may be discrete and easily missed. Research techniques are required with low cost and minimal impact in sensitive settings. In this study, the effectiveness of using a three-dimensional (3D) temperature model and botanical indicators to characterise groundwater discharge is explored at the CEH (Centre for Ecology and Hydrology) River Lambourn Observatory, Boxford, UK. This comprises a 10 ha lowland riparian wetland, designated for its scientific interest and conservation value. Temperature data were collected in winter at multiple depths down to 0.9 m over approximately 3.6 ha and transformed into a 3D model via ordinary kriging. Anomalous warm zones indicated distinct areas of groundwater upwelling which were concurrent with relic channel structures. Lateral heat propagation from the channels was minimal and restricted to within 5–10 m. Vertical temperature sections within the channels suggest varying degrees of groundwater discharge along their length. Hydrochemical analysis showed that warmer peat waters were akin to deeper aquifer waters, confirming the temperature anomalies as areas of groundwater discharge. Subsequently, a targeted vegetation survey identified Carex paniculata as an indicator of groundwater discharge. The upwelling groundwater contains high concentrations of nitrate which is considered to support the spatially restricted growth of Carex paniculata against a background of poor fen communities located in reducing higher-phosphate waters.

Groundwater pollution source identification (GPSI) provides information about the temporal and spatial distribution of pollution sources and helps decision makers design pollution remediation plans to protect the groundwater environment. The Bayesian approach based on the Markov Chain Monte Carlo (MCMC) approach provides an efficient framework for GPSI. However, MCMC sampling entails multiple model calls to converge to the posterior probability distribution of unknown pollution source parameters and entails a massive computational load if the simulation model is directly called. This study aimed to develop an innovative framework in which an improved MCMC approach was linked to a surrogate model. Sensitivity analysis was incorporated into the MH-MCMC approach, named SAMH-MCMC (sensitivity analysis based Metropolis Hastings-Markov Chain Monte Carlo), to speed up the convergence of the posterior distribution in a novel way to control the search step size. Three computationally inexpensive surrogate models for the simulation model were proposed: support vector regression, Kriging (KRG), and multilayer perceptron, and the most accurate model was chosen. The feasibility and advantages of the developed framework were evaluated and validated through two hypothetical numerical cases with homogenous and heterogeneous media. The proposed approach has strong convergence robustness as it considers the sensitivities of the unknown parameters that characterise groundwater pollution sources and can achieve high identification accuracy. Furthermore, the KRG surrogate model has a higher accuracy than other surrogate models, owing to its linear unbiased estimation characteristic. Overall, the framework developed in this study is a promising solution for identifying groundwater pollution source parameters.