The impact of intensive groundwater abstraction on recharge to a shallow regional aquifer system: evidence from Bangladesh   总被引：1，自引：0，他引：1  

Mohammad Shamsudduha  Richard G. Taylor  Kazi M. Ahmed  Anwar Zahid 《Hydrogeology Journal》2011,19(4):901-916

Quantitative evaluations of the impact of groundwater abstraction on recharge are rare. Over a period (1975??007) during which groundwater abstraction increased dramatically in the Bengal Basin, changes in net groundwater recharge in Bangladesh are assessed using the water-table fluctuation method. Mean annual groundwater recharge is shown to be higher (300??00?mm) in northwestern and southwestern areas of Bangladesh than in southeastern and northeastern regions (<100?mm) where rainfall and potential recharge are greater. Net recharge in many parts of Bangladesh has increased substantially (5??5?mm/year between 1985 and 2007) in response to increased groundwater abstraction for irrigation and urban water supplies. In contrast, net recharge has slightly decreased (??.5 to ???mm/year) in areas where groundwater-fed irrigation is low (<30% of total irrigation) and where abstraction has either decreased or remained unchanged over the period of 1985??007. The spatio-temporal dynamics of recharge in Bangladesh illustrate the fundamental flaw in definitions of “safe yield??based on recharge estimated under static (non-pumping) conditions and reveal the areas where (1) further groundwater abstraction may increase actual recharge to the shallow aquifer, and (2) current groundwater abstraction for irrigation and urban water supplies is unsustainable.  相似文献   

Pb isotopic variability in the modern-Pleistocene Indus River system measured by ion microprobe in detrital K-feldspar grains   总被引：1，自引：0，他引：1  

Anwar Alizai  Peter D. Clift  Sam VanLaningham  Ali R. Tabrez  The Edinburgh Ion Microprobe Facility 《Geochimica et cosmochimica acta》2011,75(17):4771-4795

The western Himalaya, Karakoram and Tibet are known to be heterogeneous with regard to Pb isotope compositions in K-feldspars, which allows this system to be used as a sediment provenance tool. We used secondary ion mass spectrometry to measure the isotopic character of silt and sand-sized grains from the modern Sutlej and Chenab Rivers, together with Thar Desert sands, in order to constrain their origin. The rivers show a clear Himalayan provenance, contrasting with grains from the Indus Suture Zone, but with overlap to known Karakoram compositions. The desert dunes commonly show ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁶Pb/²⁰⁴Pb values that are much higher than those seen in the rivers, most consistent with erosion from Nanga Parbat. This implies at least some origin from the trunk Indus, probably reworked by summer monsoon winds from the SW, a hypothesis supported by bulk Nd and U-Pb zircon dating. Further data collected from Holocene and Pleistocene sands shows that filled and abandoned channels on the western edge of the Thar Desert were sourced from Himalayan rivers before and at 6-8 ka, but that after that time the proportion of high isotopic ratio grains rose, indicating increased contribution from the Thar Desert dunes prior to ∼4.5 ka when flow ceased entirely. This may be linked to climatic drying, northward expansion of the Thar Desert, or changes in drainage style including regional capture, channel abandonment, or active local Thar tributaries. Our data further show a Himalayan river channel east of the present Indus, close to the delta, in the Nara River valley during the middle Holocene. While this cannot be distinguished from the Indus it is not heavily contaminated by reworking from the desert. The Pb system shows some use as a provenance tool, but is not effective at demonstrating whether these Nara sediments represent a Ghaggar-Hakra stream independent from the Indus. Our study highlights an important role for eolian reworking of floodplain sediments in arid rivers such as the Indus.  相似文献   

天山西部伊犁河灌区地下水地球化学特征   总被引：3，自引：0，他引：3  

麦麦提吐尔逊·艾则孜  海米提·依米提  艾尼瓦尔·买买提 《地球化学》2011,40(2):179-187

根据2009年伊犁河灌区地下水监测和取样分析资料,运用相关分析法、主成分分析法、半方差函数与克里格插值法,对伊犁河灌区地下水地球化学特征与地下水总溶解固体(TDS)时空分异特征进行了分析.结果表明,研究区58.18%地下水样为淡水,40.00%为微咸水,1.82%为咸水.地下水阴离子以C1和SO2-4为主,阳离子以Ca...  相似文献   

Biotransformation potential of hexavalent chromium by Bacillus pumilus-S4, Pseudomonas doudoroffii-S5 and Exiguobacterium-S8 in association with hydrophytes     

S. Ejaz  F. Z. Rizvi  S. Anwar  M. Faisal 《International Journal of Environmental Science and Technology》2013,10(4):709-718

Three chromium-resistant bacteria Bacillus pumilus-S4, Pseudomonas doudoroffii-S5 and Exiguobacterium-S8 were isolated from chromium-contaminated wastewater/soil and could resist very high concentrations of potassium chromate in Luria agar (up to 25 mg ml^?1) and acetate minimal medium (2 mg ml^?1). The strains showed growth at diverse pH and temperatures and could resist multiple heavy metals. Pseudomonas doudoroffii-S5 reduced (8.27 mg hexavalent chromium 24 h^?1) at a lower initial potassium chromate concentration (100 μg ml^?1), but overall more chromate (28.4 mg hexavalent chromium 24 h^?1) was reduced at a higher initial concentration (1,000 μg ml^?1). The addition of various heavy metals (zinc sulphate, copper sulphate, and manganese sulphate at 50 μg ml^?1) in the chromium reduction media did not significantly affect the hexavalent chromium reduction potential of these isolates. The chromium removal/detoxification potential of these strains increased when used in conjunction with hydrophytes Eichornia crassipes and Pistia stratiotes. Interestingly, the whole process runs automatically with less energy input, that is, the bacterial strains support the growth of plant while in turn the plant releases exudates that help bacterial growth.  相似文献   

Electrical properties and geochemistry of carbonate rocks from the Qasr El‐Sagha Formation,El‐Faiyum,Egypt     

Esmat A. Abou El‐Anwar  Mohamed M. Gomaa 《Geophysical Prospecting》2013,61(3):630-644

Understanding petrographical, geochemical and electrical properties of rocks is essential for investigating minerals. This paper presents a study of the petrographical, geochemical and A.C. electrical properties of carbonate rock samples. The samples collected show six lithostratigraphic rock units. Electrical properties were measured using a non‐polarizing electrode at room temperature (～20°C) and a relative atmospheric humidity of ～50% by weight in the frequency range from 42 Hz to 5 MHz. The difference in electrical properties between the samples was attributed to the change in composition and texture between the samples. Electrical properties generally change with many factors (grain size, chemical composition, grain shape and facies). The dielectric constant decreases with frequency and increases with conductor composition. The conductivity increases with the increase of conductor paths between electrodes. Many parameters can contribute to the same result of the electrical properties. The main objective of the present study is to shed more light on the relation between the texture and geochemical composition of measured samples (carbonates that contain clays and quartz grains) through electrical laboratory measurements (conductivity and dielectric constant as a function of frequency).  相似文献   

Development of temperatures in the Kingdom of Bahrain from 1947 to 2005     

Nadir Ahmed Elagib  Anwar S. Addin Abdu 《Theoretical and Applied Climatology》2010,101(3-4):269-279

A new look is focused in this study on the analysis of mean temperatures for Bahrain, as observed at its International Airport for the 59 years extending from 1947 to 2005. The temporal trends indicate significant warming of the dry-season temperatures of 0.166°C decade^?1. In particular, the summer months of May to July and October demonstrate statistically significant trends of 0.172 to 0.247°C decade^?1. There is a tendency for the wet season months to show both decreases and increases in their temperatures though the temporal trends are not significant. The decade of 1991-2000 emerged as a period of conspicuous warming as well as increase in the occurrence of unusual mean temperatures and the number of months per year with above-average temperature. No significant trend in intraannual and intraseasonal temperature variabilities is discerned, but the wet season shows predominantly higher within-season variability in temperatures as compared to the dry season. Further analyses have been carried out on the available extreme temperature data for the period 1981-2005 in an attempt to search for a possible source of climatic and/or non-climatic factors, such as intensifying desertification and rapid urbanization. By and large, the rates of diurnal temperature ranges have increased due to significantly higher rates of increasing maximum in comparison to increasing minimum temperatures. The warming rate of the overall dry season during the day is seven times that during night. However, the nocturnal temperature for the overall wet season has warmed significantly at a rate more than three times that of the overall dry season. There is a sufficient evidence that sources of rapid urbanization around the area of records seem to be a major contributor to the observed rates of temperature. Both the urbanization and the effect of the large water body of the Gulf surrounding the Island of Bahrain seem to have offset the effect of desertification on temperature changes.  相似文献   

End bearing capacity comparison of screw pile with straight pipe pile under similar ground conditions     

Adnan Anwar Malik  Jiro Kuwano  Shinya Tachibana  Tadashi Maejima 《Acta Geotechnica》2017,12(2):415-428

In the present study, the end bearing capacity of screw and straight pipe pile under similar pile tip area and ground conditions were investigated. The effect of increasing overburden pressure was also considered in this research. Pile load tests on close-ended screw and straight pipe piles were conducted in the small scale. Dry Toyoura sand was used to develop the model ground. The sand was compacted at relative density of 70, 80 and 92 %. It was observed that in case of straight pipe pile, load settlement curve plunges downward without increase in load around settlement equals to 10 % of pile tip diameter, whereas in case of screw pile, the load settlement curve plunges around settlement equals to 15 % of pile tip diameter. Moreover, the screw piles having helix-to-shaft diameter ratio 2–4.1 showed 2–12 times higher end bearing capacity than straight pipe piles with similar pile shaft diameter. It was also observed from the test results that the end bearing capacity of single-helix screw pile was in average 16.25 % less than straight pipe pile with similar pile tip area and ground conditions irrespective of the effect of increasing overburden pressure.  相似文献   

A comparison between vertically integrated and multilevel models of tidal dynamics in channels     

Anwar Ali 《Estuarine, Coastal and Shelf Science》1982,14(4):405-419

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Evaluation of aquifer environment under Hazaribagh leather processing zone of Dhaka city     

Anwar Zahid  K. -D. Balke  M. Qumrul Hassan  Matthias Flegr 《Environmental Geology》2006,50(4):495-504

Hazaribagh is a densely populated area of Dhaka city where about 185 leather processing industries have been operating and discharging solid and liquid wastes directly to the low-lying areas, river and natural canals without proper treatment. The area is covered by alluvial deposits of Holocene age and is underlain by Pleistocene Madhupur clay. The Dupi Tila Formation of Mio-Pliocene age underlain by this yellowish gray to brick red clay bed serves as the main water-bearing aquifer of Dhaka city. To assess the environmental degradation as well as the groundwater environment, major anions, cations and heavy metals of water samples, heavy metals and organic carbon content of sediment samples were analyzed in this study. Analyses of tannery effluent detect high concentration of Na⁺, Mg²⁺, Cl⁻ and SO ₄ ²⁻ followed by Ca²⁺, NH ₄ ⁺ and K⁺ with remarkable contents of some trace elements, mainly Cr, Fe, Mn, S, Ni and Pb. Higher accumulations of Cr, Al and Fe are observed in topsoil samples with significant amounts of Mn, Zn, Ni and Cu. Concentrations of ions and all the investigated trace elements of sampled groundwater were within the maximum allowable limit for drinking water of the Department of Environment, Bangladesh (DoE), and World Health Organization (WHO). However, excessive concentrations of Cr, Pb, etc., have already been reported in the shallow groundwater (10–20 m) of the area. Due to excessive withdrawal the vulnerability of groundwater contamination in deeper parts cannot be avoided for the future.  相似文献   

A study of groundwater irrigation water quality in south-central Bangladesh: a geo-statistical model approach using GIS and multivariate statistics     

M. Atikul Islam  Md. Mostafizur Rahman  Md. Bodrud-Doza  Md. Iftakharul Muhib  Mashura Shammi  Anwar Zahid  Yeasmin Akter  Masaaki Kurasaki 《中国地球化学学报》2018,37(2):193-214

Southern Bangladesh’s irrigation and drinking water is threatened by saline intrusion. This study aimed to establish an irrigation water quality index (IWQI) using a geostatistical model and multivariate indices in Gopalganj district, south-central Bangladesh. Groundwater samples were taken randomly (different depths) in two seasons (wet-monsoon and dry-monsoon). Hydrochemical analysis revealed groundwater in this area was neutral to slightly alkaline and dominating cations were Na⁺, Mg²⁺, and Ca²⁺ along with major anions Cl^? and HCO₃ ^?. Principal component analysis and Gibbs plot helped explain possible geochemical processes in the aquifer. The irrigation water evaluation indices showed: electrical conductivity (EC) >750 µS/cm, moderate to extreme saline; sodium adsorption ratio (SAR), excellent to doubtful; total hardness (TH), moderate to very hard; residual sodium bicarbonate, safe to marginal; Kelly’s ratio >1; soluble sodium percentage (SSP), fair to poor; magnesium adsorption ratio, harmful for soil; and IWQI, moderate to suitable. In addition, the best fitted semivariogram for IWQI, EC, SAR, SSP, and TH confirmed that most parameters had strong spatial dependence and others had moderate to weak spatial dependence. This variation might be due to the different origin/sources of major contributing ions along with the influence of variable river flow and small anthropogenic contributions. Furthermore, the spatial distribution maps for IWQI, EC, SSP, and TH during both seasons confirmed the influence of salinity from the sea; low-flow in the major river system was the driving factor of overall groundwater quality in the study area. These findings may contribute to management of irrigation and/or drinking water in regions with similar groundwater problems.  相似文献