Combination Of Groundwater Research Articles

Saturated hydraulic conductivity (Ksat) and topographic controls on baseflow contribution in high-altitude aquifers with complex geology

Mountains in general are important sources of water resources and correspondingly, the Upper Indus Basin (UIB) in the Himalayas provides water for hundreds of millions of users. During low-flow periods, streamflow is fed by a combination of groundwater (baseflow), snow/glacier melt and recent precipitation. However, the proportion of stream baseflow generated by different sources and the factors that control these contributions remain poorly understood. In this paper, we focus on the Western Himalayan Liddar watershed (1243 km2) in the UIB and use a multi-method approach to characterize aquifers and baseflow generation in three nested catchments which represent varying geology and topography. Our multi-method approach includes geophysical surveys, slug tests, stable isotope compositions, young water fraction (Fyw) estimation and a Bayesian end member mixing model. Specifically, we hypothesize that Ksat of the subsurface plays a critical role in the contribution of groundwater to baseflow. The watershed is subdivided into three nested catchments (Limestone, hardrock and alluvium). Our results indicate that the upstream, steep, high-permeability limestone catchment has the relatively largest groundwater contribution to streamflow (63–78 %) and a low Fyw (38 %) than the other two sites. The mid-elevation hard rock catchment has a lower permeability on average but is highly variable due to fracture networks and geologic contacts, allowing a substantial groundwater contribution to streamflow (38–66 %) and a similar Fyw (36 %) to the limestone catchment. The downstream, low-slope catchment underlain by alluvium has a highly variable hydraulic conductivity and a substantially lower groundwater contribution to streamflow (26–45 %) and a higher Fyw (55 %). We find that both hydraulic conductivity and topography exert control on the magnitude of baseflow contribution to the stream. However, Ksat acts as a key control in groundwater contribution to baseflow as observed in headwaters and downstream region of the watershed. While unconsolidated deposits are often thought of as important high-porosity mountain aquifers, our results point to the importance of fractured and karstified bedrock in baseflow generation in high mountains. As climate change alters the snow- and ice-melt regimes of UIB rivers, our study underscores the critical importance of improving our understanding of baseflow sources.

Development of quaternary calcrete in the Tensift Al Haouz area, Central Morocco: Characterization and environmental significance

This study utilizes features of calcrete to elucidate the main environmental factors that affect its formation and distribution in the Tensift Al Haouz area, Central Morocco, one of semi arid regions where calcrete is ubiquitous and occurs in a variety of forms. More than hundred calcretes profiles were examined and described by field observations. Selected samples were analyzed by optical microscopy (OM), scanning electron microscopy (SEM), X-ray Diffraction (XRD), and chemical analysis (XRF). Two types of evolution and genesis are evidenced: 1) calcrete of pedogenic origin in the central and eastern part of the studied area, developed in the vadose zone with an upward gradational maturity pattern, ranging from incipient, nodular, to concretionary and to hardpan. 2) Combination of groundwater and pedogenic origin in the western part; the paired calcrete profiles consist from bottom to top of massive calcrete suggested to have a groundwater origin; it might be formed under wet to semi-arid climatic conditions and the gravel hardpan situated at the top suggested to have developed in the vadose zone by pedogenic processes under arid climate. In this study, we conclude that the vertical and lateral distribution of calcrete is related to differences in the topography, the nature of the bedrock, the texture of parent material and the climate.

Groundwater input affecting plant distribution by controlling ammonium and iron availability

AbstractQuestion: How does groundwater input affect plant distribution in Alnus glutinosa (black alder) carrs?Location: Alder carrs along the river Meuse, SE Netherlands.Methods: Three types of site, characterized by groundwater flow, were sampled in 17 A. glutinosa carrs. Vegetation and abiotic data (soil and water chemistry) were collected and analysed using a Canonical Correspondence Analysis. Based on the results, a laboratory experiment tested the effect of groundwater input (Ca2+) on pore water chemistry (NH4+ availability).Results: Environmental factors indicating groundwater input (Ca2+ and Fe2+), correlating with the NH+4 concentration in the pore water, best explained the variation in plant distribution. NH4+ availability was determined by Ca2+ input via the groundwater and subsequent competition for exchange sites in the sediment. As a result, nutrient‐poor seepage locations fully fed by groundwater were dominated by small iron resistant plants such as Caltha palustris and Equisetum fluviatile. More nutrient‐rich locations, fed by a combination of groundwater and surface water, allowed the growth of taller iron resistant plant species such as Carex paniculata. Nutrient‐rich locations with stagnating surface water were hardly fed by groundwater, allowing the occurrence of fast growing and less iron tolerant wetland grasses such as Glyceria fluitans and G. maxima.Conclusion: Groundwater input affects plant composition in A. glutinosa carrs along the river Meuse by determining nutrient availability (ammonium) and concentrations of toxic iron.

DNA damage in peripheral blood lymphocytes of individuals residing near a wastewater drain and using underground water resources.

Mahal is a linear village settlement situated about 0.5 km from an open waste-water drain, the Tung Dhab drain, which carries effluents from local industrial sites. Villagers generally have a low-to-middle socio-economic status and use ground water or a combination of ground water and tap water for drinking and for their other daily activities. The land in and around Mahal is used for agriculture and is irrigated by water from the Tung Dhab. The drain water contains heavy metals, and there is a possibility that these and other contaminants may reach the ground water table of Mahal and thereby compromise the health of the residents. The comet assay was performed on peripheral blood lymphocytes from Mahal villagers and revealed statistically significant increases in DNA damage as compared to a control group that does not use ground water. DNA damage was also significantly related to the age of the villagers and to the length of residence in the village. In the absence of other environmental exposures, it is concluded that the elevated DNA damage in the villagers is a consequence of continuous utilization of contaminated ground water.

The Origin and Distribution of Salts on Alluvial Fans in The Atacama Desert, Northern Chile

The Atacama Desert has been predominantly hyperarid since the middle Miocene. Combined ionic and X-ray diffraction analysis shows that calcium sulphate is prevalent on three similar alluvial fans in salar basins across a transect of different environments in Antofagasta Province, northern Chile. Differences between the fans were largely due to the effect of local factors on salt input, secondary redistribution and deposit preservation. Thus carbonate was notable in the High Andes (fan C) and Pre-Cordillera (fan B), whereas in the Central Valley (fan A) greater qualities of the more soluble salts (chlorides and nitrates) probably reflect the higher level of aridity and an oceanic source (the camanchaca). Calcium sulphate distribution on the alluvial fans and on adjacent hilltops indicates an aeolian origin. Evidence from the Pre-Cordillera (fan B), however, suggests that salt input may have been episodic, related to changes in conditions within the general aridity and possibly to stone pavement and soil development. Calcium sulphate sources range from an input in Andean precipitation and the camanchaca to abundant regional evaporite deposits. It is probable, however, that products of Andean volcanism constitute the dominant primary source of calcium sulphate, and that the salt has subsequently been distributed widely within the endoreic basins of the region by a combination of groundwater, surface flow and the wind. © 1997 John Wiley & Sons, Ltd.

Sources of water used by riparian Eucalyptus camaldulensis overlying highly saline groundwater.

Water sources of Eucalyptus camaldulensis Dehn. trees were investigated on a semiarid floodplain in south-eastern Australia. The trees investigated ranged in distance from 0.5 to 40 m from a stream, with electrical conductivity 0.8 dSm-1, and grew over groundwater with electrical conductivity ranging from 30 to 50 dSm-1. The sources of water being used by the trees were investigated using the naturally occurring stable isotopes of water and measurements of soil water potential. Xylem water potential and leaf conductance were also examined to identify the trees' response to using these sources of water. Trees at distances greater than about 15 m from the stream used no stream water. The trees used groundwater in summer and a combination of groundwater and rain-derived surface-soil water (0.05-0.15 m depth) in winter. In doing so they suffered water stress at electrical conductivities higher than approximately 40 dSm-1 (equivalent to approximately -1.4 MPa). Trees adjacent to the stream used stream water directly in summer, but may have used stream water from the soil profile in winter, after the stream had risen and recharged the soil water. E. camaldulensis appeared to be partially opportunistic in the sources of water they used.

Use of High-Vacuum Technology to Remediate Soils and Groundwater in Low-Permeability Formations: ABSTRACT

The combination of groundwater pump-and-treat with vapor extraction has been successfully practiced as an integrated remedial strategy in high-permeability geologic formations. However, the effectiveness of such systems can be severely restricted as formation permeability decreases. In silty clay, glacial till materials common throughout the upper midwest, conventional pump-and-treat/vapor extraction systems typically cannot produce sufficient groundwater recovery nor create adequate subsurface air flow to expedite site remediation. Remedial efforts are further hindered by the high adsorptive capacity of silts and clays, making removal of adsorbed organics more difficult. The application of high vacuums, using liquid-ring pumps, has enabled successful remediation at sites that are not amenable to conventional groundwater pump-and-treat/vapor extraction techniques. High vacuums (25 in. of mercury vs. 1 to 5 in. for a conventional system) can be applied to a network of extraction wells to increase groundwater recovery rates and maximize subsurface air flow in these low-permeability formations, resulting in increased volatilization of organic compounds and increased mass removal rates. In addition, subsurface oxygen levels are also increased, enhancing naturally occurring biodegradation. Increased groundwater recovery rates under the influence of a vacuum also can create a larger capture zone for each individual extraction well, substantially increasing site dewatering andmore » aiding vapor extraction from previously saturated sediments. Since vapor extraction is much more efficient at mass removal of volatile organics than groundwater extraction, the added dewatering because of the high vacuum will increase overall contaminant removal and decrease remedial time.« less

Thermal Infrared Investigations, Arbuckle Mountains, Oklahoma

Thermal-infrared images obtained on flights over the Tishomingo anticline and South Flank areas near Mill Creek in the Arbuckle Mountains, Oklahoma, were used to study the possibility of identifying some common rock types from their diagnostic reflection and emission characteristics, and to evaluate the usefulness of infrared images in structural geologic investigations. The areas flown are underlain by folded and faulted Paleozoic dolomite, limestone, sandstone, shale, and Precambrian granite. Images were obtained at 6:00 a.m., 11:00 a.m., and 2:00 p.m. The predawn (6:00 a.m.) image is the most useful in distinguishing rock types. Of particular interest is a thermal contrast of dolomite (warm) and limestone (cool), sufficient to distinguish those rock types and to reveal facies changes between them. Theoretical considerations indicate that this thermal contrast arises from a combination of albedo and thermal-inertia characteristics distinctive of dolomites and limestones in many areas. The daytime images display much stratigraphic and structural detail. Small-scale bedding detail is enhanced in the morning images of low-relief areas, and contrasts of alternating formations that form hogbacks and valleys are enhanced in the afternoon images of higher relief areas. The difference in features displayed in morning and afternoon images appears to be a function of the insolation on sunward and shadowed slopes of differing scale. Fault or fracture zones are best displayed in the predawn image; they appear cooler than surrounding ground, because of greater water content and concomitant evaporation. The abundance and throughgoing nature of lineaments (which coincide for the most part with joint systems) are more obvious in the infrared images than in aerial photographs. Lineaments striking northwest are preferentially enhanced in the morning images, and lineaments striking northeast are preferentially shown in the afternoon images. This enhancement cannot be ascribed to the effects of topography, insolation, or wind; it may relate to a combination of ground-water and vegetation effects.