La capacidad del suelo de almacenar y regular el flujo de agua depende en gran medida de su su tasa de infiltración y profundidad. Los disturbios como el pastoreo y el fuego son moduladores fuertes del sistema vegetación-suelo, ya que son capaces de alterar la tasa de infiltración y la profundidad del suelo. En sistemas montanos estacionales, esto repercute sobre la capacidad de liberar lentamente el agua almacenada hacia el caudal de los arroyos. Nos propusimos indagar si las variaciones en la estructura de la vegetación, debidas en su mayoría al pastoreo y al fuego, de los bosques de altura de Polylepis australis Bier de las sierras de Córdoba se asocian a variaciones en las propiedades del suelo en general y, en particular, a aquellas que regulan la capacidad de almacenar agua. Para abarcar la variabilidad completa de estructura de la vegetación seleccionamos 28 sitios distribuidos en tres establecimientos con distintos manejos, y restringimos las variaciones topográficas. No detectamos asociaciones entre la estructura de la vegetación y la topografía; es decir, en general, logramos restringir el efecto topográfico. Por otro lado, aquellos sitios con vegetación más estructurada presentaron suelos con menor densidad aparente y mayor contenido de materia orgánica y capacidad de campo. En relación a la capacidad de almacenamiento de agua, los suelos más profundos y con mayor tasa de infiltración fueron los menos densos, con mayor contenido de materia orgánica y mayor capacidad de campo, asociados a una vegetación más estructurada. Es decir, mientras más conservado se encuentra el sistema vegetación-suelo de los bosques de P. australis, mayor cantidad de agua puede ingresar al suelo y ser almacenada. En consecuencia, las alteraciones del sistema vegetación-suelo, dadas principalmente por el pastoreo y el fuego, reducen la capacidad de almacenar agua de los bosques de altura del centro de la Argentina. | Soil water storage capacity and flow regulation relies mostly upon infiltration rate and soil depth. Disturbs such as grazing and fire strongly modulate the vegetation-soil system, and are capable of altering the infiltration rate and soil depth, as well. In mountain seasonal ecosystems, this impacts on soil capacity to slowly release water into streams. We aimed at analyzing if changes in vegetation structure and soil properties, mainly as a consequence of grazing and fire, of highland Polylepis australis Bitter woodlands of Córdoba mountains, also include alterations in general soil properties and, in particular, in those related to soil water storage capacity. In order to encompass the complete variability in vegetation structure we selected 28 sites in paddocks with different managements, restricting topographic variations. We did not find associations between vegetation structure and topographic variables, which indicates we could restrict the topographic variability. Sites with more structured vegetation had soils with lower soil bulk density and higher soil organic matter content and field capacity. Regarding soil water storage capacity, deeper soils with higher infiltration rates were those with more dense soils and higher organic matter content and field capacity, associated to more structured vegetation. This means that while vegetation-soil system of P. australis woodlands is more conserved, the soil presents more opportunities of infiltrating and storing water. Consequently, alterations on the vegetation-soil system, mainly given by grazing and fire, reduce soil water storage capacity of highland woodlands of central Argentina. | Fil: Poca, María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina | Fil: Cingolani, Ana María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina | Fil: Gurvich, Diego Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina | Fil: Whitworth Hulse, Juan Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina | Fil: Saur Palmieri, Valentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina

In the southwestern United States, precipitation in the high mountains is a primary source of groundwater recharge. Precipitation patterns, soil properties and vegetation largely control the rate and timing of groundwater recharge. The interactions between climate, soil and mountain vegetation thus have important implications for the groundwater supply. This study took place in the Sacramento Mountains, which is the recharge area for multiple regional aquifers in southern New Mexico. The stable isotopes of oxygen and hydrogen were used to determine whether infiltration of precipitation is homogeneously distributed in the soil or whether it is partitioned among soil-water ‘compartments’, from which trees extract water for transpiration as a function of the season. The results indicate that “immobile” or “slow” soil water, which is derived primarily from snowmelt, infiltrates soils in a relatively uniform fashion, filling small pores in the shallow soils. “Mobile” or “fast” soil water, which is mostly associated with summer thunderstorms, infiltrates very quickly through macropores and along preferential flow paths, evading evaporative loss. It was found that throughout the entire year, trees principally use immobile water derived from snowmelt mixed to differing degrees with seasonally available mobile-water sources. The replenishment of these different water pools in soils appears to depend on initial soil-water content, the manner in which the water was introduced to the soil (snowmelt versus intense thunderstorms), and the seasonal variability of the precipitation and evapotranspiration. These results have important implications for the effect of climate change on recharge mechanisms in the Sacramento Mountains.

A shallow alluvial coastal aquifer in the Batinah area of Oman, with sea-water intrusion that extends several kilometres inland, has been studied experimentally, analytically and numerically. The water table is proved to have a trough caused by intensive pumping from a fresh groundwater zone and evaporation from the saline phreatic surface. Resistivity traverses perpendicular to the shoreline indicated no fresh groundwater recharge into the sea. Using an analytical Dupuit-Forchheimer model, developed for the plain part of the catchment, explicit expressions for the water table, sharp interface location and stored volume of fresh water are obtained. It is shown that by the pumping of salt water from the intruded part of the aquifer, this intrusion can be mitigated. Different catchment sizes, intensities of fresh groundwater pumping, evaporation rates, water densities, sea level, incident fresh water level in the mountains and hydraulic conductivity are considered. SUTRA code is applied to a hypothetical case of a leaky aquifer with line sinks modeling fresh water withdrawal and evaporation. The numerical code also shows that pumping of saline water can pull the dispersion zone back to the shoreline.

In order to determine if artificially collected water fog in the mountainous located in central the region of Veracruz state is suitable for human consumption; a preliminary sampling was made, from January to March (2010), the period with more fog frequency. The objective was to analyze the physical, chemical and biological aspects concerning water quality. It was found that this water is not suitable for direct human consumption, since it contains heavy metals such as mercury, coliform organisms and high amounts of ammonia nitrogen, though it is suitable for direct use in agriculture. However, it is possible to apply a sanitation treatment for human use at a cost of 0.00341 USD L-1 not including the labor cost neither the necessary infrastructure. Various causes can lead to this water pollution are discussed and it is concluded that collected fog water is not suitable for human consumption, but it might be used for agriculture.

A mathematical model of a highly heterogeneous functioning karst aquifer is described. The aquifer is in a high-relief karst massif and, as is common for such locations, data are scarce and there are no borehole, piezometer or pumping-test data. The scarcity of data in this case required a parsimonious approach to ensure that the level of complexity of the model was commensurate with the amount, type and quality of the available data. Parsimony also requires the model to include the minimum essential components that account adequately for the data, which in this and similar cases are the functional dualities of the karst system: duality in recharge, flow and discharge. The model is three-dimensional (3D) in the sense that the aquifer is discretized into 3D voxels, although the flow is one-dimensional (1D) and vertical in the vadose zone, and horizontal and two-dimensional (2D) in the saturated zone. The parsimonious model was designed by coupling a 1D unsaturated gravity-driven flow along the vertical (along each column of voxels that discretize the aquifer) and a 2D unconfined Darcy flow in the saturated zone. In the context of this type of aquifer, preferential recharge through the network of karst conduits implies a rapid rise in the water table, the location and extension of which are model parameters. The karst springs are simulated by drains. The methodology, which is completely general, is illustrated by application to the karst aquifer in the Sierra de las Nieves mountains in southern Spain.

The Regional Deep Cretaceous Aquifer (RDCA) is the principal groundwater resource in Syria. Isotope and hydrochemical data have been used to evaluate the geographic zones in terms of renewable and non-renewable groundwater and the inter-relation between current and past recharge. The chemical and isotopic character of groundwater together with radiometric ¹⁴C data reflect the existence of three different groundwater groups: (1) renewable groundwater, in RDCA outcropping areas, in western Syria along the Coastal and Anti-Lebanon mountains. The mean δ¹⁸O value (−7.2 ‰) is similar to modern precipitation with higher ¹⁴C values (up to 60–80 pmc), implying younger groundwater (recent recharge); (2) semi-renewable groundwater, which is located in the unconfined section of the RDCA and parallel to the first zone. The mean δ¹⁸O value (−7.0 ‰) is also similar to modern precipitation with a ¹⁴C range of 15–45 pmc; (3) non-renewable groundwater found in most of the Syrian interior, where the RDCA becomes confined. A considerable depletion in δ¹⁸O (−8.0 ‰) relative to the modern rainfall and low values of ¹⁴C (<15 pmc) suggest that the large masses of deep groundwater are non-renewable and related to an older recharge period. The wide scatter of all data points around the two meteoric lines in the δ¹⁸O-δ²H diagram indicates considerable variation in recharge conditions. There is limited renewable groundwater in the mountain area, and most of the stored deep groundwater in the RDCA is non-renewable, with corrected ¹⁴C ages varying between 10 and 35 Kyr BP.

Saltwater intrusion is one of the most pressing environmental concerns in coastal areas with increased water demands. Water extraction decreases the level of fresh groundwater, reducing the water pressure and allowing saltwater to flow further inland. Tools for simulating, monitoring and managing saltwater intrusion can provide valuable support in decision-making for management options. In this work, such a tool was developed for the arid coastal aquifer of La Paz in Baja California, Mexico. A geomodel was generated by using a transient electromagnetic method (aquifer geometry, saltwater intrusion). This geomodel, in turn, was used to construct a three-dimensional density-dependent flow model to simulate groundwater flow and saltwater intrusion during the past decades. The results confirmed that a large cone of depression had formed due to excessive pumping in the agricultural area. This successively led to the inversion of the hydraulic gradient and seawater intrusion advancement on the order of 6–8 km inland in the northern-central portion of the aquifer. Freshwater recharge mostly originates from the mountainous southeastern portion of the basin. It supplies water for the city of La Paz and counteracts the saltwater intrusion advancement. The alternation of advancement and retreat of the freshwater–saltwater interface could be attributed to changing climate effects and/or policy changes.

Temperature, discharge, and stable isotope ratios of five karst springs in a mountainous area of Zigui County, Hubei Province, Central China, were analyzed. The purpose was to illustrate the heat exchanges linked to circulation depth in the exposed karst water systems through the development of a method for estimating heat input and heat flux during a rainstorm. Meteorological water in the study area conformed to a local meteoric water line (δD = 8.37 δ¹⁸O + 12.99) with a mean δ¹⁸O elevation gradient of −4.0‰ km⁻¹, which was used to estimate mean circulation depths of 209–686 m. The mean spring temperatures defined a vertical gradient of −5.4 °C km⁻¹, which resembled that of the stable atmosphere of the Earth, indicating that the thermal response patterns are mainly controlled by surface air temperature. Thermal convection after rainfall events dominated heat exchange between baseflow and recharge water, leading to a warmer and colder recharge during summer and winter, respectively, whereas thermal conduction dominated the heat exchange only between groundwater, surrounding geology, and the interface air under a condition of no rainfall, resulting in only small temperature variations of the baseflow. Successful application of the method for estimating heat exchange showed that the characteristics of shallow circulation, strong karstification, and well-developed epikarst readily allowed disruption of the thermal balance of the Yuquandong system, resulting in a poor heat regulation capacity, a larger variation of heat input, a lower mean heat flux, and lower baseflow temperatures compared to those of the Dayuquan system.

The Badain Jaran Desert (BJD) in China is a desert with impressive sand dunes and a groundwater situation that has attracted numerous researchers. This paper gives an overview of the mysteries of groundwater in the BJD that are exhibited as five key problems identified in previous studies. These problems relate to the origin of the groundwater, the hydrological connection between the BJD and the Heihe River Basin (HRB), the infiltration recharge, the lake–groundwater interactions, and the features of stable isotope analyses. The existing controversial analyses and hypotheses have caused debate and have hindered effective water resources management in the region. In recent years, these problems have been partly addressed by additional surveys. It has been revealed that the Quaternary sandy sediments and Neogene-Cretaceous sandstones form a thick aquifer system in the BJD. Groundwater flow at the regional scale is dominated by a significant difference in water levels between the surrounding mountains and lowlands at the western and northern edges. Discharge of groundwater from the BJD to the downstream HRB occurs according to the regional flow. Seasonal fluctuations of the water level in lakes are less than 0.5 m due to the quasi-steady groundwater discharge. The magnitude of infiltration recharge is still highly uncertain because significant limitations existed in previous studies. The evaporation effect may be the key to interpreting the anomalous negative deuterium-excess in the BJD groundwater. Further investigations are expected to reveal the hydrogeological conditions in more detail.

The McMurdo Dry Valleys (MDVs), Antarctica, exist in a hyperarid polar desert, underlain by deep permafrost. With an annual mean air temperature of −18 °C, the MDVs receive <10 cm snow-water equivalent each year, collecting in leeward patches across the landscape. The landscape is dominated by expansive ice-free areas of exposed soils, mountain glaciers, permanently ice-covered lakes, and stream channels. An active layer of seasonally thawed soil and sediment extends to less than 1 m from the surface. Despite the cold and low precipitation, liquid water is generated on glaciers and in snow patches during the austral summer, infiltrating the active layer. Across the MDVs, groundwater is generally confined to shallow depths and often in unsaturated conditions. The current understanding and the biogeochemical/ecological significance of four types of shallow groundwater features in the MDVs are reviewed: local soil-moisture patches that result from snow-patch melt, water tracks, wetted margins of streams and lakes, and hyporheic zones of streams. In general, each of these features enhances the movement of solutes across the landscape and generates soil conditions suitable for microbial and invertebrate communities.