A proposição de índices de qualidade do solo tem crescido de forma considerável nos últimos anos para análises de sustentabilidade ambiental e da produção agrícola. No entanto, não há, nas condições brasileiras, o desenvolvimento de qualquer indicador de qualidade do solo vinculado à recarga de água subterrânea. O objetivo deste estudo foi gerar um índice de qualidade do solo, relacionado à recarga de água subterrânea (IQS RA), válido para as condições da Bacia Hidrográfica do Alto Rio Grande e proceder a seu mapeamento por meio de técnicas geoestatísticas. O IQS RA proposto é uma combinação linear de três indicadores relacionados à infiltração de água no solo: densidade do solo, condutividade hidráulica saturada e macroporosidade. Para sua validação, foi considerada a participação do deflúvio base (ou subterrâneo) no deflúvio total para quatro sub-bacias da Bacia Hidrográfica do Alto Rio Grande, analisando o comportamento desses indicadores hidrológicos tendo-se como referência a distribuição espacial do IQS RA. O índice gerado mostrou-se uma ferramenta importante para avaliação do potencial do solo para recarga de água subterrânea, uma vez que ele reflete a influência dos usos da terra no comportamento do deflúvio base e, consequentemente, na dinâmica da produção de água pelas sub-bacias. | In the last years, soil quality indexes for analyses of the environmental sustainability and agricultural production have been proposed in increasing numbers. However, none of these indexes is related to the groundwater recharge soil quality index for conditions in Brazil. The objective of this study was to generate a soil quality index related to the groundwater recharge (SQI GR) of the physiographical conditions of the Upper Rio Grande Basin and to draw a map of SQI GR using geostatistical procedures. The proposed SQI GR consists of a linear combination of three properties related to water infiltration into the soil: bulk density, saturated hydraulic conductivity and macroporosity. To validate the index, the participation of the base flow in the total flow of four sub-basins of the Upper Rio Grande Basin was considered, analyzing the behavior of this hydrologic indicator taking the spatial distribution of SQI GR as reference. This validation process indicated the importance of SQI RG as tool to evaluate the groundwater recharge potential since it reflects the influence of different land uses on the base flow behavior and, consequently, on water yield from sub-basins.

En la simulación de producción de agua en una cuenca montañosa pequeña de Venezuela se evaluó el modelo Soil and Water Assesment Tool (SWAT). Los valores diarios simulados se compararon con los medidos en un canal de aforo según índices de regresión y de diferencia. SWAT sobrestimó los valores diarios de escurrimiento superficial y subestimó los de caudal de base. No obstante, la cantidad total de agua producida en el período del experimento se simuló con precisión, lo cual sugiere que para mejorar el funcionamiento de SWAT deben realizarse ajustes simultáneos al valor de número de curva y a los factores de agua subterránea. Se concluye: a) la evaluación y calibración de SWAT es poco transferible debido a la gran cantidad de variables que pueden ser modificadas, por lo que es conveniente contar con información que permita ajustar las simulaciones particulares, y b) la coincidencia de valores acumulados medidos y simulados no implica buen funcionamiento del modelo en cuanto a lapsos parciales, podría existir compensación de errores en tendencias inconsistentes. | A water yield simulation from SWAT model was evaluated in a sloped small watershed in Venezuela. Simulated daily values were compared with measured values obtained from a gauge channel by the use of difference and regression based indices. Results indicated that SWAT overestimated the daily surface runoff values and underestimated the base flow values. In spite of that, total water yield for the whole experiment period was simulated accurately; it is therefore suggested that simultaneous fine-tunes of curve number values and underground water parameters should be done. It was concluded that a) transfer of SWAT calibration and validation may be difficult, because of the great amount of values that can be modified, and, consequently, it is convenient to have available sufficient information that allows proper adjustment of particular simulations and b) similarities in the cumulative simulated and measured values do not imply a proper model performance related with short or partial lapses, because error balances can occur for inconsistent value trends

En la simulación de producción de agua en una cuenca montañosa pequeña de Venezuela se evaluó el modelo Soil and Water Assesment Tool (SWAT). Los valores diarios simulados se compararon con los medidos en un canal de aforo según índices de regresión y de diferencia. SWAT sobrestimó los valores diarios de escurrimiento superficial y subestimó los de caudal de base. No obstante, la cantidad total de agua producida en el período del experimento se simuló con precisión, lo cual sugiere que para mejorar el funcionamiento de SWAT deben realizarse ajustes simultáneos al valor de número de curva y a los factores de agua subterránea. Se concluye: a) la evaluación y calibración de SWAT es poco transferible debido a la gran cantidad de variables que pueden ser modificadas, por lo que es conveniente contar con información que permita ajustar las simulaciones particulares, y b) la coincidencia de valores acumulados medidos y simulados no implica buen funcionamiento del modelo en cuanto a lapsos parciales, podría existir compensación de errores en tendencias inconsistentes. | A water yield simulation from SWAT model was evaluated in a sloped small watershed in Venezuela. Simulated daily values were compared with measured values obtained from a gauge channel by the use of difference and regression based indices. Results indicated that SWAT overestimated the daily surface runoff values and underestimated the base flow values. In spite of that, total water yield for the whole experiment period was simulated accurately; it is therefore suggested that simultaneous fine-tunes of curve number values and underground water parameters should be done. It was concluded that a) transfer of SWAT calibration and validation may be difficult, because of the great amount of values that can be modified, and, consequently, it is convenient to have available sufficient information that allows proper adjustment of particular simulations and b) similarities in the cumulative simulated and measured values do not imply a proper model performance related with short or partial lapses, because error balances can occur for inconsistent value trends

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.