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1.
The Deccan Traps or the basalts of western India are the largest exposure of basic lava flows covering about 500,000 km2. Groundwater occurrence in the Deccan Traps is in phreatic condition in the weathered zone above the hard rock and in semi-confined condition in the fissures, fractures, joints, cooling cracks, lava flow junctions and in the inter-trappean beds between successive lava flows, within the hard rock. Dug wells, dug-cum-bored wells and boreholes or bore wells are commonly used for obtaining groundwater. The yield is small, usually in the range of 1–100 m3/day. The average land holding per farming family is only around 2 ha. Recently, due to the ever increasing number of dug wells and deep bore wells, the water table has been falling in several watersheds, especially in those lying in the semi-arid region of the traps, so that now the emphasis has shifted from development to sustainable management. Issues like climatic change, poverty mitigation in villages, sustainable development, rapid urbanization of the population, and resource pollution have invited the attention of politicians, policy makers, government agencies and non-governmental organizations towards watershed management, forestation, soil and water conservation, recharge augmentation and, above all, the voluntary control of groundwater abstraction in the Deccan Traps terrain.  相似文献   

2.
The basalt flow in Irbid district covers an area of about 300 km2 and forms different shapes: elongated strips, sub-rounded spots, and arc-like outcrops. The basalt flow in the study area has thicknesses ranging from 1 to 30 m. This study is conducted to evaluate the basaltic rocks as a construction material in eight different places of Harrat Irbid. Thirty-six rock cores were prepared from the collected fresh basaltic rock samples to study the physical and mechanical properties. The basaltic rocks in the study area have desirable physical and mechanical properties; the rocks have high apparent specific gravity values (2.70–2.90), bulk specific gravity (2.60–2.84), absorption values (0.33–1.60 %) that indicates the texture is crystalline, porosity (0.22–2.15 %), void ratio (0.002–0.022), water content (0.35–1.08 %), degree of saturation (41–68 %), rebound number of Schmidt hammer hardness test (average 44.10), point load strength(average 11.35 MPa),uniaxial strength (average 106.83 MPa) which is classified as medium strength, basalt uniformity of wear (0.206), and very high durability which is equal to 99.52 % in average, recorded after the second cycle of the test. Based on field observations and physical and mechanical tests, this study confirms that the genesis of basalt in the study area is strongly related to Harrat Al-Shaam basalt. Therefore, this study adds a new area of about 300 km2 to the Harrat Al-Shaam area. Additionally, this study strongly recommends the use of the basaltic rocks that have been tested in this study for some industrial applications (e.g., in construction).  相似文献   

3.
In 1973, traces of China’s early Neolithic Hemudu culture (7,000–5,000 BP) were discovered in the village of Hemudu in Yuyao County, Zhejiang Province, in the lower Yangtze River coastal plain. The site has yielded animal and plant remains in large quantities and large numbers of logs secured with tenon and mortise joints, commonly used in wooden buildings and other wooden structures. For hydrogeologists, the most interesting structure is an ancient wooden well. The well is believed to be about 5,600 years old, which makes it the oldest wooden well yet found in China. The well site contains over 200 wooden components and can be divided into inner and outer parts. The outer part consists of 28 piles around a pond. The inner part, the wooden well itself, lies in the middle of the pond. The walls of the well were lined with close-set timber piles reinforced by a square wooden frame. The 28 piles in the outer part of the site may have been part of a shelter for the well, suggesting that the people of the Hemudu culture were already concerned with water hygiene and protection of their water source.  相似文献   

4.
Declining water level trends and yields of wells, deterioration of groundwater quality and drying up of shallow wells are common in many parts of India. This is mainly attributed to the recurrence of drought years, over exploitation of groundwater, increase in the number of groundwater structures and explosion of population. In this subcontinent, the saving of water has to be done on the days it rains. India receives much of its rainfall in just 100 h in a year mostly during the monsoon period. If this water is not captured or stored, the rest of the year experiences a precarious situation manifest in water scarcity. The main objective behind the construction of subsurface dams in the Swarnamukhi River basin was to harvest the base flow infiltrating into sandy alluvium as waste to the sea and thereby to increase groundwater potential for meeting future water demands. An analysis of hydrographs of piezometers of four subsurface dams, monitored during October 2001–December 2002, reveals that there is an average rise of 1.44 m in post-monsoon and 1.80 m in the pre-monsoon period after the subsurface dams were constructed. Further, during the pre-monsoon month of June, much before construction of subsurface dams in October 2001, the water level was found fluctuating in the range of 3.1–10 m, in contrast to the fluctuation ranging from 0.4 to 3.1 m during the period following the construction of dams. Hence, the planning of rainwater harvesting structures entails thorough scientific investigations for identifying the most suitable locations for subsurface dams.  相似文献   

5.
Only recently has significant attention been paid to groundwater in hard rocks. The reason is probably the normally limited yield of water wells in such lithologies. Their importance for water-supply has increased, especially in the Third World, during recent years. In shield areas in temperate regions, hard rocks have been important for rural water supply for a long time. The relatively new attention to hard rock hydrogeology is also due to the fact that crystalline rocks are vulnerable to acidification and that several countries plan to use deep repositories in crystalline rocks for spent nuclear fuel. Added to this, new hydrogeological investigation methods for fractured aquifers have come into use in pre-investigations for rock installations. This paper gives a brief overview of the occurrence and properties of aquifers in crystalline rocks, and also examines some practical aspects of their use.  相似文献   

6.
The thermal baths and bottled water industry are highly related to the hydrogeology of hard rocks in Portugal. In the last 15 years, almost all classical dug wells or simple spring arrangements were replaced by drilled wells. The completion of these new wells was normally preceded by geological, geophysical, and hydrogeological surveys as well as by exploration and observation wells. A step-by-step approach resulted in a positive well location in most sites. Some small-scale, low-enthalpy geothermal projects are in operation in some locations.  相似文献   

7.
The combined effects of low rainfall, groundwater withdrawal in excess of 300 GL/year and reduced recharge in areas covered by pine plantations has caused the water table in a sandy unconfined aquifer on the Gnangara Mound in Western Australia to drop by up to 5 m and aquifer storage to decline by about 500 GL over the last 20 years. Groundwater has become acidic in areas of high drawdown, with pH values typically being less than 5.0 at the water table, and elevated concentrations of SO4 2?, Al, Fe, Zn, Cu, Ni and Pb. Trends of increasing acidity and base cation concentrations in deep water supply wells in the Mirrabooka wellfield indicate that about 0.7 keq/ha/year of base cations are being leached from soil within cones of depression of pumping wells. These results indicate that the assessment of the sustainable yields of aquifers under conditions of low rainfall needs to consider geochemical interactions between groundwater, aquifer sediments, soils and vegetation, and not be just based on aquifer hydraulics and water-balance changes.  相似文献   

8.
Sa'ar–Nayfa reservoir is mainly made up of carbonate sediments with bands of shale that contain a substantial amount of proven oil in the Hiswah Oilfield, Sayun–Masila Basin, eastern Yemen. Several vertical wells have been drilled and penetrated these sequences. This study is concerned on the petrophysical evaluation and well log analysis of the Lower Cretaceous of 11 wells at the Hiswah Oilfield, Hadramawt Governorate, eastern Yemen. Computer-assisted log analyses were used to evaluate the petrophysical parameters such as shale volume, total porosity, effective porosity, water saturation, hydrocarbon saturation, flushed zone saturation and reservoir and pay flags. Cross-plots of the petrophysical parameters versus depth were illustrated. The Lower Cretaceous Sa'ar–Nayfa reservoir reflects that the matrix components are mainly carbonates and shales. Moreover, the lithological-geologic model reflected that these shales are strongly affecting the porosity and, consequently, the fluid saturation in the Sa'ar–Nayfa reservoir. In this study, the thickness of the Sa'ar–Nayfa reservoir increases from central toward north-eastern and north-western parts within the Hiswah Oilfield. The porosities analyses of the investigation of the Sa'ar–Nayfa reservoir for the 11 studied wells concluded that the average total porosity ranges from 5.4 % to 16.8 % while the effective porosity ranges from 5.2 % to 14.8 %. Water saturation of the Sa'ar–Nayfa reservoir ranges from 6.9 % to 75.8 %. On the other hand, hydrocarbon saturation matches with water saturation in a reverse relationship. Sa'ar–Nayfa reservoir is interpreted as good quality reservoir rocks with high average effective porosity reaching to 20 % and high hydrocarbon saturation exceeding 93 %. The Sa'ar–Nayfa reservoir reveals promising reservoir characteristics especially the upper reservoir unit, which should be taken into consideration during future development of the oilfields area. The hydrocarbon saturation map of the Sa'ar–Nayfa reservoir shows a regular pattern of distribution with a general increasing to the northeast, northwest and east directions while decreasing southwest wards, recording the maximum value of 93.1 % at the Hiswah-21 well.  相似文献   

9.
The deep wells drilled along the eastern escarpment of the Jordan Valley penetrate confined aquifers that produce thermal and mineralized artesian water. Uncontrolled flows from poorly constructed and uncapped artesian wells over the last 30 years have caused the deterioration of the quality of shallow groundwater and surface water. They also have been accelerating the discharge of saline water from deep aquifers and have caused the loss of shallow fresh groundwater resources through the downward percolation of fresh water to replace the extracted deep salty groundwater. A lack of adequate controls on the construction and maintenance of artesian wells is leading to widespread water quality problems in the region, which limits the ability of future generations to access high-quality water, a clear breach of the principle of intergenerational equity.  相似文献   

10.
The characteristics of the recent tsunami deposits threw light on some sources of deposition on the beach of the Red Sea. The studied area is delineated by latitudes 25°6′ N and 25°9′ N and longitudes 34°50′ E and 34°53′ E; it covers an elongate area of about 12 km2 along the Red Sea coast, North Marsa Alam City (4 km). The area is bounded by Wadi Asalay to the north and Wadi Sifayn from the south. For evaluation of the area, a lot of information allows us to interpret the conditions prevailing during deposition of the sediments especially at the coast. To achieve the target, five wells were drilled to study core samples, well logging measurements, and 69 vertical electrical sounding stations were carried out. The studied area and adjacent areas were geologically surveyed to note geological features related to Paleo-earthquakes. From geological and geophysical studies, the dominant rock types at the western portions of the studied area are sandstone, sandy clay, clay, clayey sandstone, and gravels; at the middle portion of the studied area, the rocks are hard, but the eastern side of the area, especially at the beach of the Red Sea, several cycles of depositions of coral reefs occurred with intercalations of clastic deposits such as clay, sand, sandstone, conglomerate, gravels, pebbles, and a lot of fossils and shell fragments. The rocks are characterized by heterogeneous properties and ill-sorted. The area includes large numbers of faults due to highly tectonism of the area. The results indicated that the area has lateral variation of sediments. The carbonate rocks at the beach contain clastic fragments, and carbonate blocks are included within clastic rocks. With increasing the distance from the beach to the west, the sediments are less heterogeneous. The beach of the Red Sea was subjected to Paleo-tsunami waves due to highly Paleo-seismic activity inside the Red Sea and left their signature in geological column especially at the beach. The observation of some geological features such as Paleo-liquefaction and landslides indicate that the area subjected to strong earthquakes related to rifting of the Red Sea.  相似文献   

11.
Kingdom of Bahrain often suffers from urban flooding problems despite being a desertic country. An attempt has been made in this contribution to study the efficacy of the storm water injection systems not only in tackling urban flooding problems but also in augmenting the depleting ground water resources of the country. Two pilot studies were carried out in a centrally located area, one in a relatively open area and another in a densely populated location. A set of one recharge well and one observation well of about 40 m depth and 30 m apart was drilled in each site. Storm water was injected into the recharge wells after allowing it to pass through a specially designed natural filter system. Ground water levels were monitored at the observation wells on monthly basis and water samples were collected periodically during and after the rainfall events for chemical analysis. Initial results showed that the volume of storm water injected is proportional to the volume of storm water generated in an area. However, in the long run, the injection well having favourable hydrogeological situation and lesser silts in the storm water performed better in terms of total recharge despite having lesser volume of storm water available. Ground water quality for some parameters such as lead and cadmium remained an issue of concern, but could be controlled through construction of stricter filter system. Dilution of the injected storm water with the host ground water too significantly reduced the risks of contamination. The injection well located in the open area performed better than that of the densely populated area despite having lesser volume of storm water available. Site selection of the recharge wells, therefore, plays a vital role in the efficacy of a storm water injection system.  相似文献   

12.
The Paris–Abu Bayan area located along the Darb El Arbaein road is involved in the New Valley Project in the Egyptian Western Desert (EWD) as part of ongoing efforts since the 1960s. In this dryland area, groundwater stored in the Nubian Sandstone Aquifer System (NSAS) serves as the only water resource for a number of different uses. A major concern is the significant groundwater withdrawals from 74 pumped wells since the beginning of agricultural activities in 2000. The recent rapid expansion of agricultural activity and the lack of sufficient groundwater recharge as a result of unplanned groundwater development have led to severe stress on the aquifer. Field measurements have shown a rapid decline in groundwater levels, creating a crisis situation for this sole source of water in the area. In this study, mathematical modeling of the groundwater system (single aquifer layer) of the Paris–Abu Bayan reclaimed area was implemented using MODFLOW to devise a new strategy for the sustainable use of groundwater, by applying a number of scenarios in a finite-difference program. The conceptual model and calibration were developed by generating and studying the hydrogeological records, NSA parameters, production wells, and water level measurements for 2005 and 2012. Three management scenarios were applied on the calibrated model to display the present and future stresses on this aquifer over a 30-year period (2012–2042). The results clearly show a high decline in the heads of the NSA, by about 13.8 m, due to the continuous withdrawal of water (first scenario: present conditions, 102,473 m3/day). In the second scenario, the water level is expected to decrease significantly, by about 16 m, in most of the reclamation area by increasing the pumping rates by about 25% (over-pumping) to meet the continuous need for more cultivation land in the area. To reduce the large decline in water levels, the third plan tests the aquifer after reducing the water withdrawal by approximately 25%, applying modern irrigation systems, and suggesting two new reclaimed areas in the northeastern and northwestern parts (areas 1 and 2), with 20 new wells, at 500 m3/day/well. The results in this case show that groundwater levels are slightly decreased, by about 9.5 m, while many wells (especially the new wells in the northern part) show a slight decrease in groundwater levels (0.8 m). The results comparison shows that the groundwater level in the modeled area is lowered by 0.3 m/year with an increase in the number of wells to 94 and increased cultivation area by about 18% (third scenario), versus 0.45 m/year and 0.60 m/year recorded for the first and second scenarios, respectively. Therefore, based on the results, the third scenario is recommended as a new strategy for improving groundwater resource sustainability in the region.  相似文献   

13.
High arsenic levels in groundwater of the aquifers, belonging to the Pliocene terrestrial layers and Quaternary alluvial sediments, have become a significant problem for the inhabitants living in Sarkisla (Turkey). The main objective of this study was to determine the origin and arsenic contamination mechanisms of the Sarkisla drinking water aquifer systems. The highest arsenic concentrations were found in Pliocene layers and alluvial sediments with concentrations ranging from 2.1 to 155 mg/kg. These rocks are the main aquifers in the study area, and most of the drinking groundwater demand is met by these aquifers. Groundwater from the Pliocene aquifer is mainly Ca-HCO3 and Ca-SO4 water type with high EC values reaching up to 3,270 μS/cm, which is due to the sulfate dissolution in some parts of the alluvial aquifer. Stable isotope values showed that the groundwater was of meteoric origin. Tritium values for the groundwater were between 8.31 and 14.06 TU, representing a fast circulation in the aquifer. Arsenic concentrations in the aquifers were between 0.5 and 345 μg/L. The highest arsenic concentrations detected in the Pliocene aquifer system reached up to 345 μg/L with an average value of 60.38 μg/L. The arsenic concentrations of the wells were high, while the springs had lower arsenic concentrations. These springs are located in the upper parts of the study area where the rocks are less weathered. The hydrogeochemical properties demonstrated that the water–rock interaction processes in sulfide-bearing rocks were responsible for the remarkably high groundwater arsenic contamination in the study area. In the study area, the arsenic levels determined in groundwater exceeded the levels recommended by the WHO. Therefore, it is suggested that this water should not be used for drinking purposes and new water sources should be investigated.  相似文献   

14.
This study is a contribution to our understanding of the hydrocarbon potentials of the Nkporo Shale in the Anambra Basin, Nigeria. The main objective was to simulate the hydrocarbon generation and expulsion in the Nkporo source horizons encountered in Igbariam-1, Iji-1, and Ajire-1 wells drilled in the basin, using the one-dimensional Genesis Zetaware basin modeling software. This software enabled the integration of burial and thermal influences on Nkporo source rocks with kinetic parameters, in order to define the timing of hydrocarbon generation and expulsion in relation to the main structural episodes in the basin. The Nkporo source horizons encountered in Igbariam-1 well (2,650 m) has not expelled hydrocarbons but has a remaining potential of 380 mg/gTOC. Conversely, in Iji-1 well (3,450 m) and Ajire-1 well (3,250 m), the Nkporo source rocks expelled oil of about 110–127 mg/gTOC and gas of about 85–125 mg/gTOC. The time of expulsion was in Eocene–Oligocene (51–30 My) at the rate of 10.5–11.5 mg/gTOC/My. The remaining potentials for Nkporo source rocks in Iji-1 and Ajire-1 wells are 160 and 125 mg/gTOC, respectively. The result shows an increasing trend in maturation, generation, and expulsion of hydrocarbons with increasing depth towards the southwestern part of the basin. This resulted in an increase in the generated hydrocarbon volumes to the south due to (a) increased burial depth and early maturation and (b) changing source lithofacies—more marine. The fault system linking potential reservoirs such as Owelli Sandstone to the source rock suggests a possible migration of the generated hydrocarbons to those reservoirs at that time.  相似文献   

15.
Summary The long-term response to sustained compressive loading of two crystalline hard rocks of the Canadian Shield has been investigated. Static fatigue tests conducted on granite and anorthosite have shown that in a humid environment the long-term strengths of these crystalline igneous rocks could be less than 60 percent of their dry instantaneous strengths. Such reduction in strength has implications for the design and construction of deep tunnels, mines and other underground installations. The particular case of a nuclear fuel waste vault located at a depth of one kilometer is considered.Considering a service life of 1,000 years, a vault one kilometer deep in granite could suffer time-dependent spalling in highly stressed regions of the rock where the maximum principal stress exceeds about 130 MPa. Anorthosite has a lower instantaneous strength than granite and it is sensitive to static fatigue as well. A vault in anorthosite would be subject to time-dependent spalling of the perimeter rock in places where the maximum principal stress is above 80 MPa.  相似文献   

16.
Water quality tests were performed on two long-screened alluvial aquifer wells (15–30 m of screen) that had been completed in a heterogeneous aquifer that exhibits extreme temporal water quality variability. When stressed, the total dissolved solids (TDS) in one well decreased from 10,600 to 3,500 mg/L and in another well the TDS increased from 136 to 2,255 mg/L. Nested short-screened monitoring wells were constructed in chemically distinct horizons affecting each well. Water level measurements and solute and isotopic samples were obtained from the production wells and the monitoring wells during a water quality test. Results of a time drawdown tests demonstrate transmissivity differences between horizons. Ambient water quality in the production wells and aquifer cross-contamination are controlled by well-bore mixing due to head differences of as little as 0.01 m between chemically distinct horizons which are linked by the production well screen. During non-stress periods, the ambient well-bore chemistry is controlled by the horizon with the greatest hydraulic head, whereas during stressed conditions, horizon transmissivity controls the well-bore chemistry. In one well, aquifer cross-contamination, driven by an ambient head differential of 1.2 m, persisted until about 1,600 well-bore volumes were purged.  相似文献   

17.
The Dead Sea is worldwide a major bromine provider for industry with an average concentration of 5.2 g/l of bromide compared to 0.065 mg/l in seawater and with a Cl/Br weight ratio in the Dead Sea water of about 42 compared to around 300 in oceanic water. The origin of the high bromide concentration in the Dead Sea has not yet been adequately clarified. In the course of this study, the bromide concentrations in the different surface and groundwater bodies in Jordan were analyzed and the types of rocks with which these waters were in contact were identified. Analyses carried out up to about 30 years ago and recent analyses confirm the natural origin of bromide in the water and also confirm that the analyzed sources are not polluted by anthropogenic bromide sources. It was found that a variety of these surface and groundwater sources contain high concentrations of bromide which discharges into the Dead Sea and contribute to its high bromide concentration. The present study concludes that the late Cretaceous early Tertiary oil shale deposits form the major source of the bromine species in the surface and groundwater feeding the Dead Sea. Some bromide is also contributed by the Triassic and Jurassic rocks containing evaporate salts containing bromides. Phosphate rocks of late Upper Cretaceous age contribute also with appreciable amounts of bromine species to the different water sources and hence to the Dead Sea water. At present, dissolution and erosion of bromide-rich sediments laid down by the predecessor water bodies of the present Dead Sea such as the Lisan Lake are being transported into the Dead Sea and contribute relatively large amounts of secondary bromide to the Dead Sea water.  相似文献   

18.
Understanding the linkage between temporal climate variability and groundwater nitrate concentration variability in monitoring well records is key to interpreting the impacts of changes in land-use practices and assessing groundwater quality trends. This study explores the coupling of climate variability and groundwater nitrate concentration variability in the Abbotsford-Sumas aquifer. Over the period of 1992–2009, the average groundwater nitrate concentration in the aquifer remained fairly steady at approximately 15 mg/L nitrate-N. Normalized nitrate data for 19 individual monitoring wells were assessed for a range of intrinsic factors including precipitation, depth to water table, depth below water table, and apparent groundwater age. At a broad scale, there is a negative correlation between nitrate concentration and apparent groundwater age. Each dedicated monitoring well shows unique, non-uniform cyclical variability in nitrate concentrations that appears to correspond with seasonal (1 year) cycles in precipitation as well as longer-period cycles (~5 years), possibly due to ENSO (El Niño Southern Oscillation) or the Pacific North American (PNA) pattern. These precipitation cycles appear to influence nitrate concentrations by approximately ±30 % of the critical concentration (10 mg/L NO3–N). Not all wells show direct correlation due to many complex local-scale factors that influence nitrate leaching including spatially and temporally variable nutrient management practices and soil/crop nitrogen dynamics (anthropogenic and agronomic factors).  相似文献   

19.
塔中地区中古44和中古10两条走滑断裂切割了塔中低凸起中古43井区,它们对油气输导具有控制意义。油气从中—下寒武统沿两条走滑断裂向上运移后,在下奥陶统鹰山组内向两侧输导,呈"T"字形的油气充注方式。从断裂向两侧,V/Ni值呈减小趋势,原油密度、黏度、含硫量和含蜡量等物性参数,距离断裂由近到远,均表现为逐渐变大的趋势,这些都证明油气是由走滑断裂向两侧运移的。水、油、气井的目的层海拔分别为-4 700 m以下、约-4 600～-4 500 m和-4 500 m以上;出油气层位在海拔-4500 m以上的井,平均气油比较高,在海拔-4 500 m以下的井,平均气油比较低。研究井区油气开发的连通半径平均约600 m,小于油气成藏的连通半径。在开发和成藏两种时间尺度下隔挡层的物性上限有着显著差别。  相似文献   

20.
Overexploitation of groundwater resources in Sana’a Basin, Yemen, is causing severe water shortages associated water quality degradation. Groundwater abstraction is five times higher than natural recharge and the water-level decline is about 4–8 m/year. About 90 % of the groundwater resource is used for agricultural activities. The situation is further aggravated by the absence of a proper water-management approach for the Basin. Water scarcity in the Wadi As-Ssirr catchment, the study area, is the most severe and this area has the highest well density (average 6.8 wells/km2) compared with other wadi catchments. A local scheme of groundwater abstraction redistribution is proposed, involving the retirement of a substantial number of wells. The scheme encourages participation of the local community via collective actions to reduce the groundwater overexploitation, and ultimately leads to a locally acceptable, manageable groundwater abstraction pattern. The proposed method suggests using 587 wells rather than 1,359, thus reducing the well density to 2.9 wells/km2. Three scenarios are suggested, involving different reductions to the well yields and/or the number of pumping hours for both dry and wet seasons. The third scenario is selected as a first trial for the communities to action; the resulting predicted reduction, by 2,371,999 m3, is about 6 % of the estimated annual demand. Initially, the groundwater abstraction volume should not be changed significantly until there are protective measures in place, such as improved irrigation efficiency, with the aim of increasing the income of farmers and reducing water use.  相似文献   

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