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Stochastic methods based on time-series modeling combined with geostatistics can be useful tools to describe the variability of water-table levels in time and space and to account for uncertainty. Monitoring water-level networks can give information about the dynamic of the aquifer domain in both dimensions. Time-series modeling is an elegant way to treat monitoring data without the complexity of physical mechanistic models. Time-series model predictions can be interpolated spatially, with the spatial differences in water-table dynamics determined by the spatial variation in the system properties and the temporal variation driven by the dynamics of the inputs into the system. An integration of stochastic methods is presented, based on time-series modeling and geostatistics as a framework to predict water levels for decision making in groundwater management and land-use planning. The methodology is applied in a case study in a Guarani Aquifer System (GAS) outcrop area located in the southeastern part of Brazil. Communication of results in a clear and understandable form, via simulated scenarios, is discussed as an alternative, when translating scientific knowledge into applications of stochastic hydrogeology in large aquifers with limited monitoring network coverage like the GAS. [ABSTRACT FROM AUTHOR]

Four bench-scale solute injection experiments were conducted in a natural undisturbed basaltic fractured core of the Serra Geral Formation (SGF) (Brazil) to assess the performance of the equivalent apertures on conservative solute transport. Fracture aperture is particularly important in controlling solute transport in fractured-rock aquifers. The spatial heterogeneity of fracture apertures complicates solute transport modeling. Scientific researchers and mainly hydrogeology professionals still adopt a single value for the fracture aperture field, i.e., an equivalent aperture. However, there is a lack of information about the most suitable equivalent aperture associated with solute transport phenomena, especially for basaltic fractured aquifers. The objective of this study was to evaluate the performance of three types of equivalent apertures on conservative solute transport in a basaltic aquifer sample. The fracture aperture field was measured using the advanced high-resolution and nondestructive technique, x-ray micro-computed tomography. The performance of the equivalent apertures was evaluated using an analytical solution of the one-dimensional advection-dispersion equation (ADE) compared to observed breakthrough curves. As a result, the arithmetic mean of the measured aperture field was 111.74 ± 54.26 μm. The analytical solution of ADE coupled with mass balance aperture was able to predict breakthrough behavior, especially for low volumetric flow rates. This study demonstrates that the mass balance aperture should be adopted as an equivalent aperture instead of the hydraulic and friction loss equivalent aperture when inertial forces of macroscopic flow are negligible. The findings provide a step forward towards better understanding of groundwater contamination risk in basaltic fractured aquifers. [ABSTRACT FROM AUTHOR]

There was an error during production which resulted in the alpha symbol (α) being omitted from the article in some locations. [ABSTRACT FROM AUTHOR]

The Guarani Aquifer System (GAS) is the largest transboundary groundwater reservoir in South America, yet recharge in the GAS outcrop zones is one of the least known hydrological variables. The objective of this study was to assess the suitability of using remote sensing data in the water-budget equation for estimating recharge inter-annual patterns in a representative GAS outcropping area. Data were obtained from remotely sensed estimates of precipitation ( P) and evapotranspiration (ET) using TRMM 3B42 V7 and MOD16, respectively, in the Onça Creek watershed in Brazil over the 2004-2012 period. This is an upland flat watershed (slope steepness <1 %) dominated by sandy soils and representative of the GAS outcrop zones. The remote sensing approach was compared to the water-table fluctuation (WTF) method and another water-budget equation using ground-based measurements. On a monthly basis, the TRMM P estimate showed significant agreement with the ground-based P data ( r = 0.93 and RMSE = 41 mm). Mean(±SD) satellite-based recharge ( R) was 537(±224) mm year. Mean ground-based recharge using the water-budget ( R) and the WTF ( R) methods were 469 mm year and 311(±75) mm year, respectively. Results show that 440 mm year is a mean (between R, R and R) recharge for the study area over the 2004-2012 period. The latter mean recharge estimate is about 29 % of the mean historical P (1,514 mm year). These results are useful for future studies on assessing recharge in the GAS outcrop zones where data are scarce or nonexistent. [ABSTRACT FROM AUTHOR]