José F. Muñoz

Acid leaching of copper in a saturated porous material: Parameter identification and experimental validation of a two-dimensional transport model

Abstract In this study, a two-dimensional mathematical solute transport model is proposed to simulate the leaching of copper ore tailings using sulfuric acid as the leaching agent, injection wells to introduce the leaching agent, and pumping wells to retrieve the pregnant copper leach solution. To calibrate the model, a tracer experiment and a leaching experiment were performed, both under conditions of a single-direction flow pattern established between two boundaries of constant height. These experiments enabled the model hydraulic, dispersion and reaction parameters to be determined. Validation of the model was performed by comparison of the numerical results given by the model with experimental results obtained from a second leaching experiment, performed under conditions of a radial flow pattern established through the use of four injection wells and one pumping well and making use of the parameters estimated previously during the calibration process. The comparison between predicted and measured leaching behavior was good (20–22% error). The study has significant implications for applications related to the use of the proposed numerical model for predicting the performance of in-situ soil washing alternatives.

Evaporation from shallow groundwater in closed basins in the Chilean Altiplano

Abstract The hydrological cycle in arid and semi-arid climates is highly controlled by evaporation. The correct quantification of this process is essential for improving the accuracy of water balance estimates, especially in closed basins. The objective of this paper is to characterize evaporation rates from shallow groundwater using the chamber approach in six closed basins in the Altiplano of northern Chile. Measurements were made at 49 locations with water-table depths ranging from 0.09 m to 3.3 m. Estimated daily evaporation rates appeared to be strongly related to groundwater depth and soil texture. In particular, the highest rates were recorded in areas with high groundwater tables and coarse-grained soils. Evaporation curves were derived by fitting exponential and power relationships as functions of the groundwater depths that we proposed to use in the study area. An application of these curves for the Salar de Pedernales basin produced an estimated evaporation flow of 530 L s-1, using the average curve. Citation Johnson, E., Yáñez, J., Ortiz, C. & Muñoz, J. (2010) Evaporation from shallow groundwater in closed basins in the Chilean Altiplano. Hydrol. Sci. J. 55(4), 624–635.

Opus simulation of water dynamics and nitrate transport in a field plot

Abstract In this paper, Opus, an agricultural contaminant transport model, was used to simulate a year of soil water flow and nitrate transport as well as crop growth for an arable cultivated soil, near Grenoble, France. This study is explicitly related to the cultivation of irrigated maize, a major crop in the area. The results have shown that, in terms of water balance, the simulations of water flow match the general measured trends. Drainage and evapotranspiration were estimated with errors of 4 and 20%, respectively. Runoff estimation was exactly accurate. Nitrogen movement and nitrogen concentration in the root zone were simulated well, and the cumulative leach beyond the root zone was estimated with an error less than 11%. The results for crop growth were good. Some reasons for these results are discussed.

Sources of surface water for the Soncor ecosystem, Salar de Atacama basin, northern Chile

Abstract The Salar de Atacama is located in the most arid desert in the world. Despite its extreme conditions, it has many ecosystems of high ecological value. The Soncor ecosystem, a sequence of lagoons, is the most important environment of the region as it acts as the centre for the breeding of the Andean Flamingo. This salt flat also contains significant mining deposits and is an important water source for the region. Freshwater and brine—enriched in lithium and potassium—are being pumped from the aquifers near to the Soncor ecosystem, which has so far not been greatly affected by this groundwater extraction. However, there is a potential risk that future anthropogenic effects may disturb this fragile environment. The objective of this study is to determine the origin of the water sources of the Soncor ecosystem so as to adequately manage its water resources. Three hypotheses previously proposed in the technical literature were investigated in order to determine proactive actions to protect this fragile ecosystem. The study utilized classic hydrogeological techniques, such as the construction of stratigraphic profiles, piezometric maps and stream gauging, combined with less-common isotopic techniques, such as the 87Sr/86Sr ratio. The results confirmed the hypothesis that the origins of the water sources are associated with groundwater inputs coming from the east side of the salt flat, in the north of the basin. Editor Z.W. Kundzewicz; Associate editor M. Acreman Citation Ortiz, C., Aravena, R., Briones, E., Suárez, F., Tore, C., and Muñoz, J.F., 2014. Sources of surface water for the Soncor ecosystem, Salar de Atacama basin, northern Chile. Hydrological Sciences Journal, 59 (2), 336–350.

A TDR-waveform approach to estimate soil water content in electrically conductive soils

A new methodology to determine moisture content in electrically conductive soils is developed.New aspects of TDR waveform are used to estimate soil moisture.TDR measurements in electrically conductive soils can be done without modifying the sensors. Time domain reflectometry (TDR) has been widely used by the scientific community as a reliable method to indirectly measure the volumetric water content (?) of soils, and in most soils TDR can provide observations of ? at high temporal resolution with acceptable accuracy. This technique induces an electrical wave in waveguides inserted into the soil, estimates the soil bulk dielectric permittivity (e) based on an interpretation of the reflected electromagnetic signal, and then relates e with ?. In electrically conductive soils, the reflected signal can be highly attenuated by the effect of the soils bulk electrical conductivity, resulting in very large errors in the estimation of ?; the traditional TDR methodology is thus subject to large errors and uncertainties. This work presents a simple and empirical waveform interpretation methodology based on variables less sensitive to the soils electrical conductivity than those used in the traditional TDR methodology. This approach extends the applicability of TDR sensors with reliable and accurate measures of ?, making it possible to more accurately measure soil water contents in settings that have traditionally been difficult to observe, and without modifying the TDR sensors.

A hydrogeochemistry and isotopic approach for the assessment of surface water–groundwater dynamics in an arid basin: the Limarí watershed, North-Central Chile

This paper describes the results of a hydrochemistry and isotopic study of surface water and groundwater dynamics at the Limarí River basin, arid North-Central Chile. The study involved two sampling campaigns, performed in April (Fall, at the end of the irrigation season) and December 2010 (late Spring, at the peak of the irrigation season). The main results show the effect of La Paloma and Hurtado dams on the chemical and isotopic compositions of the Grande and Hurtado rivers (main tributaries of the Limarí River), the influence of return flows to the Limarí River from surface water irrigation in agricultural areas, the local effects of metallurgical operations in the El Ingenio Creek, the effect of water–rock interaction processes, and the nearby coastal belt influence on the Punitaqui Creek area and the lower part of the Limarí River. In addition, this study shows an active interaction between surface water and shallow groundwater, and a minor importance of local precipitation events, on the hydrological behavior in the study area. An exception is the Rinconada de Punitaqui zone where the results are consistent with the origin of the water being associated with local precipitation. Also, sources of sulfate, which is present in high levels especially in surface waters, have been assessed. The results of this study, based on an integrated use of chemical and isotopic tracers, provide sound and useful information to establish the level of interaction between surface water and groundwater, allowing the development of a hydrological conceptual model for the area.