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71.
Modelling groundwater over-extraction in the southern Jordan Valley with scarce data 总被引：1，自引：0，他引：1
To deal with the challenge of groundwater over-extraction in arid and semi-arid environments, it is necessary to establish management strategies based on the knowledge of hydrogeological conditions, which can be difficult in places where hydrogeological data are dispersed, scarce or present potential misinformation. Groundwater levels in the southern Jordan Valley (Jordan) have decreased drastically in the last three decades, caused by over-extraction of groundwater for irrigation purposes. This study presents a local, two-dimensional and transient numerical groundwater model, using MODFLOW, to characterise the groundwater system and the water balance in the southern Jordan Valley. Furthermore, scenarios are simulated regarding hydrological conditions and management options, like extension of arable land and closure of illegal wells, influencing the projection of groundwater extraction. A limited dataset, literature values, field surveys, and the ‘crop water-requirement method’ are combined to determine boundary conditions, aquifer parameters, and sources and sinks. The model results show good agreement between predicted and observed values; groundwater-level contours agree with the conceptual model and expected flow direction, and, in terms of water balance, flow volumes are in accordance with literature values. Average annual water consumption for irrigation is estimated to be 29 million m3 and simulation results show that a reduction of groundwater pumping by 40% could recover groundwater heads, reducing the water taken from storage. This study presents an example of how to develop a local numerical groundwater model to support management strategies under the condition of data scarcity. 相似文献
72.
Elisabeth C. Kosters Bart E. J. M. VanMierlo Nico H. Verbeek Bart J. Posthumus Thomas M. McGee Jan Brouwer 《Sedimentary Geology》1992,80(3-4):199-212
More than 400 km of high-resolution, partially digitally acquired seismic data were collected in a 30 × 60 km area offshore from the Dutch mesotidal barrier island shoreline, in order to analyze the Holocene transgressive sequence.
The investigated area was subaerially exposed during the most recent (Weichselian) Pleistocene lowstand and glaciated during the previous (Saale/Illinoian) glacial period. Sea level was probably at a level comparable to that of the present during the intervening Eem/Sangamonian highstand.
The area's seismic signature is characterized by several levels of channelization, separated by major, area-wide high-amplitude reflectors. The lowermost aerial reflector represents the Saale boulder clay. The largest channel system, which cuts this reflector, was incised during the Older Dryas cooling event and filled during the Allerød warming period. It was subsequently re-incised during the Younger Dryas and refilled during the early Holocene. The most pronounced and extensive reflector represents the base of the Holocene, and almost everywhere equals the planed-off top of the Eem highstand section. This reflector is overlain by aggradational facies, separated by one level of channelization and one planed-off (ravinement?) surface. The most prominent type of seismic facies above the lowermost level of channelization is a set of progradational clinoforms, which is interpreted as a preserved ebb-tidal delta system. This system is associated with the first Holocene shoreline of ca. 7500 yrs BP.
The eastern part of the study area contains sand ridges with a complex pattern of internal cross-stratification. Ridge-crest sediments are very well-sorted with a mean grain size of 2.8-2.6 φ (ca. 0.15 mm), whereas sediments in the troughs are well-sorted with a mean grain size of 1.8-0.8 φ (0.25–0.5 mm). Origin of these ridges is tentatively thought to be related to reworking since 5000 yrs BP, when the dynamic regime was more or less similar to that of the present and sediment supply had decreased substantially. 相似文献
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Anthropogenic Climate Change: A Reason for Concern Since the 18th Century and Earlier 总被引：1，自引：0，他引：1
During the last 20 years the concept of anthropogenic climate change has left academic circles and become a major public concern. Some people consider ‘global warming’ as the major environmental threat to the planet. Even though mostly considered a novel threat, a look into history tells us that claims of humans deliberately or unintentionally changing climate is a frequent phenomenon in Western culture. Climate change, due to natural and anthropogenic causes, has often been discussed since classical times. Environmental change including climate change was seen by some as a biblical mandate, to ‘complete the Creation’. In line with this view, the prospect of climate change was considered as a promising challenge in more modern times. Only since the middle of the 20th century, has anthropogenic climate change become a menacing prospect. The concept of anthropogenic climate change seems to be deeply embedded in popular thinking, at least in Europe, which resurfaces every now and then after scientific discoveries. Also, extreme weather phenomena have in the past often been explained by adverse human interference. A list of claims of anthropogenic climate modifications is presented; the remarkable similarity of the anthropogenic climate change debate in the second half of the 19th century is compared to the present situation. Of course, the present threat seems much more real than any of the historical predecessors, which turned out to be overestimated. 相似文献
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Hydrogeology Journal - Groundwater monitoring wells or boreholes often show complex flow behaviors that are essential to understand for the characterization of aquifer systems. In karst or... 相似文献
78.
Fandel Chlo&#; Miville Fran&#;ois Ferr&#; Ty Goldscheider Nico Renard Philippe 《Hydrogeology Journal》2022,30(3):927-946
Hydrogeology Journal - Anisotropic fast-marching algorithms are computationally efficient tools for generating realistic maps of karst conduit networks, constrained by both the spatial extent and... 相似文献
79.
Karst groundwater vulnerability mapping: application of a new method in the Swabian Alb, Germany 总被引：22，自引：6，他引：16
Nico Goldscheider 《Hydrogeology Journal》2005,13(4):555-564
Groundwater from karst aquifers is an important drinking water resource, which is, however, particularly vulnerable to contamination. Karst aquifers consequently need special protection. This paper discusses the concept of groundwater vulnerability mapping and the special characteristics of karst aquifers that are relevant in this context. On this basis, a new method of groundwater vulnerability mapping is proposed—the PI method. It can be applied for all types of aquifers, but provides special tools for karst. Vulnerability is assessed as the product of two factors: protective cover (P) and infiltration conditions (I). The method was first applied and compared with two other methods (EPIK and the German method) in a test site in the Swabian Alb, Germany. The results obtained with the different methods are discussed and an outlook on the role of vulnerability maps within an overall groundwater protections scheme is given.
Resumen Las aguas subterráneas en medios kársticos suponen un recurso importante para uso de boca, pero es particularmente vulnerable a la contaminación, por lo que los acuíferos kársticos requieren una protección especial. Este artículo discute el concepto de cartografía de vulnerabilidad de las aguas subterráneas y las características propias de los acuíferos kársticos que son relevantes en este contexto. Con esta base, se propone un nuevo método para cartografiar la vulnerabilidad de las aguas subterráneas, denominado "PI". Puede ser aplicado a todo tipo de acuíferos, pero proporciona herramientas especiales en medios kársticos. Se establece la vulnerabilidad como resultado de dos factores: la cubierta protectora y las condiciones de infiltración. El método ha sido aplicado por vez primera y comparado con otros dos enfoques (EPIK y el método alemán) en un emplazamiento ubicado en Swabian Alb (Alemania). Se discute los resultados obtenidos con estos métodos y se incide en cuál es el papel que desempeñan los mapas de vulnerabilidad en el contexto de los esquemas generales de protección de las aguas subterráneas.
Résumé L'eau souterraine des karsts est une importante ressource d'eau potable, cependant particulièrement vulnérable à la pollution. C'est pourquoi les aquifères karstiques nécessitent une protection particulière. Ce papier discute le concept de cartographie de la vulnérabilité de l'eau souterraine et les caractéristiques particulières des aquifères karstiques qui sont concernés dans ce contexte. Sur cette base, une nouvelle méthode de cartographie de la vulnérabilité de l'eau souterraine est proposée: la méthode PI. Elle peut être appliquée à tous les types d'aquifères, mais fournit des outils spécifiques au karst. La vulnérabilité est évaluée comme étant le produit de deux facteurs: les conditions de couverture protectrice (P) et d'infiltration (I). La méthode a été mise en oeuvre pour la première fois et comparée à deux autres méthodes (EPIK et la méthode allemande) sur un site test du Jura souabe (Allemagne). Les résultats obtenus avec les différentes méthodes sont discutés et le rôle des cartes de vulnérabilité dans un schéma général de protection des eaux souterraines est passé en revue.相似文献
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