Long-term trend analysis of water table using ‘MAKESENS’ model and sustainability of groundwater resources in drought prone Barind area,NW Bangladesh   总被引：1，自引：0，他引：1  

ATM Sakiur Rahman  Md. Kamruzzama  Chowdhury Sarwar Jahan  Quamrul Hasan Mazumder 《Journal of the Geological Society of India》2016,87(2):179-193

In Bangladesh, agriculture plays a major role in the national economy. In the drought prone Barind area in NW Bangladesh, cropping intensity has increased almost double since late eighties of last century (from 1985) because of the introduction of groundwater irrigation. Long-term behavior of groundwater table (GWT) in the drought prone Barind area has been studied using MAKESENS model in the wake of massive installation of tube-wells. The study reveals that the maximum and minimum depths to GWT during 1991-2010 show on average declining trend of 4.51 m and 4.73 m. The long-term prediction for the period of 2020-50 assuming the current rate of groundwater withdrawal is that the declining trend will be 1.16 to 1.59 and 1.07 to 1.82 times more for maximum and minimum groundwater depths respectively in comparison to the present. The rigorous exploitation of groundwater for irrigation, decreasing rainfall and surface geological attributes lead towards declining trend of GWT. This will hamper the country’s food security and ultimately threaten its socio-economic sustainability. So the appropriate strategies for the management of groundwater resource on a sustainable basis should be the priority for maintaining agricultural productivity.  相似文献   

Paleoproterozoic granitoids in the basement of Bangladesh: A piece of the Indian shield or an exotic fragment of the Gondwana jigsaw?   总被引：1，自引：0，他引：1  

S.M. Mahbubul Ameen  Simon A. Wilde  Md. Zafrul Kabir  Eunuse Akon  Khalil R. Chowdhury  Md. Sharif Hossain Khan 《Gondwana Research》2007,12(4):380-387

We present the first precise age for Precambrian basement rocks in Bangladesh. These lie within the Dinajpur block, located between the Indian Craton to the southwest and the Shillong Massif to the east. There are no surface outcrops and the rocks were intersected by drill holes. They consist of a suite of tonalitic and granodioritic rocks, variously deformed to granitic gneiss and intruded by younger monzogranite. A tonalite obtained at a depth of 227.48 m in drill hole BH-2 at Maddhapara, in northwestern Bangladesh, records a SHRIMP zircon ²⁰⁷Pb/²⁰⁶Pb magmatic age of 1722 ± 6 Ma. Paleoproterozoic rocks with similar magmatic ages are unknown in the adjacent Indian blocks of the Chotanagpur Plateau (Indian Craton) or Shillong Massif. This lack of comparable ages may be due to the paucity of precise radiometric ages from the Indian terrains or, more likely, because there are real age differences, with the buried rocks at Maddhapara representing a separate and discrete microcontinental fragment (the Dinajpur block) that was trapped by the northward migration of India during Gondwana dispersal.  相似文献   

Mitigating parameter bias in hydrological modelling due to uncertainty in covariates     

Shahadat Chowdhury  Ashish Sharma   《Journal of Hydrology》2007,340(3-4):197-204

The uncertainty in hydrological model covariates, if ignored, introduces systematic bias in the parameters estimated. We introduce here a method to determine the true value of parameters given uncertainty in model inputs. This method, known as simulation extrapolation (SIMEX) operates on the basis of an empirical relationship between parameters and the level of input noise (or uncertainty). The method starts by generating a series of alternate model inputs by artificially adding white noise in increasing multiples of the known error variance. The resulting parameter sets allow us to formulate an empirical relationship between their values and the level of noise present. SIMEX is based on theory that the trend in alternate parameters can be extrapolated back to the notional error free zone.

We illustrate the strength of SIMEX in improving skills of predictive models that use uncertain sea surface temperature anomaly (SSTA) data over the NINO3 region as predictor to the southern oscillation index (SOI), an alternate measure of the strength of the El Nino southern oscillation. Our hypothesis is that the higher magnitude of noise in the pre 1960 data period introduces bias to model parameters where SSTA is the input variable. The relatively error invariant southern oscillation index (SOI) is regressed over SSTA and calibrated using a subset of the series from 1900 to 1960. We validate the resulting models using the less erroneous 1960–2003 data period. Overall the application of SIMEX is found to reduce the residual predictive errors during the validation period.  相似文献   

Dynamic response of cylindrical structures considering coupled soil-structure interaction under seismic loading     

Indrajit Chowdhury  Ronkoyel Tarafdar  Ambarish Ghosh  Shambhu Pada Dasgupta 《Bulletin of Earthquake Engineering》2016,14(8):2329-2360

This paper attempts to develop a mathematical model for estimating the seismic response of a cylindrical shaped nuclear reactor building resting in an elastic halfspace considering foundation compliance. Most of the research carried out on this topic has either been carried out by resorting to finite element method (FEM) which makes the computational cost expensive or based on the simplifying assumption of assuming the cylindrical structure as a multi degree lumped mass stick model with soil coupled as boundary springs. In the present paper an analytical model has been developed in which the deformation of the cylindrical body (including its shear deformation characteristics) has been taken into cognizance and then coupling with foundation stiffness a comprehensive solution has been sought based on Galerkin’s weighted residual technique. The results are finally compared with FEM to check the reliability of the same. The results are found to be in good agreement with the detailed finite element analysis.  相似文献   

Identification of pre-seismic anomalies of soil radon-222 signal using Hilbert–Huang transform     

Saheli Chowdhury  Argha Deb  Md. Nurujjaman  Chiranjib Barman 《Natural Hazards》2017,87(3):1587-1606

Concentration of Rn-222 in soil has been monitored continuously at Ravangla in the Sikkim Himalayan Region of eastern India for about 7 months from October 2015 to May 2016 to detect earthquake-induced anomalies. The recorded data clearly show that various physical and meteorological parameters influence the soil radon concentration, leading to very complex soil Rn-222 time series. The components due to such external influences have been removed from the present time series, and Hilbert–Huang transform (HHT) applied for analysis of the data. Two radon anomalies caused due to earthquakes of magnitude M _b = 5.0 that occurred on 19 November 2015 and 5 April 2016 within an epicentral distance of 500 km from the monitoring station have been identified on the soil Rn-222 time series. These two precursory anomalies occurred 9 and 10 days, respectively, before the occurrence of the earthquakes. The absence of spurious signals or missing anomalies demonstrates that HHT is advantageous for analysis of nonlinear non-stationary data, and hence, it is a promising technique to analyse soil radon behaviour for predicting the possibility of occurrence of earthquakes.  相似文献   

Reliability Analysis of Excavation Induced Basal Heave     

Subha Sankar Chowdhury 《Geotechnical and Geological Engineering》2017,35(6):2705-2714

The present study deals with the reliability analysis of basal heave caused by excavation considering uncertainty in the soil properties. The case study considered in the present work has been analyzed deterministically by Hsieh et al. (Can Geotech J 45:788–799, 2008). Taiwan building code is adopted in the method for analyzing the basal heave failure. The random variables (undrained shear strength and total unit weight of clay) are assumed to be normally distributed and uncorrelated. A series of parametric studies have been conducted to calculate the reliability index on the basis of the matrix formulation for the second moment method by Hasofer and Lind (J Eng Mech ASCE 100(1):111–121, 1974) considering different coefficient of variation of undrained shear strength and total unit weight of clay layers. It has been found that for a particular value of coefficient of variation of total unit weight, the reliability index with respect to occurrence of basal heave failure decreases with increase in the coefficient of variation of undrained shear strength. Moreover, the reliability index also decreases when the coefficient of variation of total unit weight increases. It has also been found that the probability of basal heave failure is lower with respect to factor of safety equals to 1.2, as compared to factor of safety equals to 1.0. Sensitivity analysis shows that the undrained shear strength of the bottommost layer and total unit weight of the second layer are the most significant random variables affecting the reliability index. Guidelines are provided for reliability based design where, for ‘target’ reliability index of 2.5 and 3.0, the factor of safety can be chosen such that all the related uncertainties are taken into account, especially with regard to undrained shear strength of the bottommost layer and total unit weight of the second layer. Design guidelines have been provided for this purpose.  相似文献   

Groundwater arsenic contamination and its health effects in India   总被引：2，自引：0，他引：2  

Dipankar Chakraborti  Mohammad Mahmudur Rahman  Bhaskar Das  Amit Chatterjee  Dipankar Das  Biswajit Nayak  Arup Pal  Uttam Kumar Chowdhury  Sad Ahmed  Bhajan Kumar Biswas  Mrinal Kumar Sengupta  Md. Amir Hossain  Gautam Samanta  M. M. Roy  Rathindra Nath Dutta  Khitish Chandra Saha  Subhas Chandra Mukherjee  Shyamapada Pati  Probir Bijoy Kar  Adreesh Mukherjee  Manoj Kumar 《Hydrogeology Journal》2017,25(4):1165-1181

During a 28-year field survey in India (1988–2016), groundwater arsenic contamination and its health effects were registered in the states of West Bengal, Jharkhand, Bihar and Uttar Pradesh in the Ganga River flood plain, and the states of Assam and Manipur in the flood plain of Brahamaputra and Imphal rivers. Groundwater of Rajnandgaon village in Chhattisgarh state, which is not in a flood plain, is also arsenic contaminated. More than 170,000 tubewell water samples from the affected states were analyzed and half of the samples had arsenic >10 μg/L (maximum concentration 3,700 μg/L). Chronic exposure to arsenic through drinking water causes various health problems, like dermal, neurological, reproductive and pregnancy effects, cardiovascular effects, diabetes mellitus, diseases of the respiratory and gastrointestinal systems, and cancers, typically involving the skin, lungs, liver, bladder, etc. About 4.5% of the 8,000 children from arsenic-affected villages of affected states were registered with mild to moderate arsenical skin lesions. In the preliminary survey, more than 10,000 patients were registered with different types of arsenic-related signs and symptoms, out of more than 100,000 people screened from affected states. Elevated levels of arsenic were also found in biological samples (urine, hair, nails) of the people living in affected states. The study reveals that the population who had severe arsenical skin lesions may suffer from multiple Bowens/cancers in the long term. Some unusual symptoms, such as burning sensation, skin itching and watering of eyes in the presence of sun light, were also noticed in arsenicosis patients.  相似文献   

Australian rainfall trends and their relation to the southern oscillation index   总被引：3，自引：0，他引：3  

R. K. Chowdhury  S. Beecham 《水文研究》2010,24(4):504-514

Rainfall is the key climate variable that governs the spatial and temporal availability of water. In this study we identified monthly rainfall trends and their relation to the southern oscillation index (SOI) at ten rainfall stations across Australia covering all state capital cities. The nonparametric Mann–Kendall (MK) test was used for identifying significant trends. The trend free pre‐whitening approach (TFPW) was used to remove the effects of serial correlation in the dataset. The trend beginning year was approximated using the cumulative summation (CUSUM) technique and the influence of the SOI was identified using graphical representations of the wavelet power spectrum (WPS). Decreasing trends of rainfall depth were observed at two stations, namely Perth airport for June and July rainfall starting in the 1970s and Sydney Observatory Hill for July rainfall starting in the 1930s. No significant trends were found in the Melbourne, Alice Springs and Townsville rainfall data. The remaining five stations showed increasing trends of monthly rainfall depth. The SOI was found to explain the increasing trends for the Adelaide (June) and Cairns (April) rainfall data and the decreasing trends for Sydney (July) rainfall. Other possible climatic factors affecting Australian rainfall are also discussed. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Hydrochemistry and origin of salinity in groundwater in parts of Lower Tista Floodplain,northwest Bangladesh   总被引：1，自引：0，他引：1  

Rumy Afroza  Quamrul H. Mazumder  Chowdhury S. Jahan  M. A. I. Kazi  M. A. Ahsan  M. A. Al-Mansur 《Journal of the Geological Society of India》2009,74(2):223-232

Hydrochemistry in parts of the Lower Tista Floodplain in northwest Bangladesh is dominated by alkalies and weakly acid, having highest concentration of sodium cations and bicarbonate anions respectively. Groundwater is characterized by sodium-calcium and sodium-potassium cation and bicarbonate-chloride-sulphate anion facies, and genetically ‘normal chloride’, ‘normal sulphate’, and ‘normal carbonated’ type, and soft to saline. Based on electrical conductivity values, the area is divided into northern fresh and southern saline groundwater zone, and values like salinity, Na%, SAR, and RSC and a good correlation between Na⁺ and Cl^?, and Cl^? and salinity reveals increasing salinity with depth indicating a mixing of fresh and saline bodies due to marine transgression (?) during Holocene period in the Bengal delta. The rock weathering is likely to affect the groundwater quality by dolomite dissolution and calcium precipitation, representing reverse softening process and is brine seawater. Water extracted from shallow zone (from 20 to 30 m) has suitability for drinking purpose, livestock consumption and irrigation purposes, and partially suitable for industrial use, but that from deeper zone (from 30 to 50 m) is generally poor and unsuitable especially for irrigation purposes with low alkali and moderate to high salinity hazard. So groundwater can be used for irrigation in the area of fine textured soil with proper management practices.  相似文献   

Mineralogical and geochemical characteristics of scheelite-bearing skarns,and genetic relations between skarn mineralization and petrogenesis of the associated granitoid pluton at Sargipali,Sundergarh District,Eastern India   总被引：1，自引：0，他引：1  

Sangita Chowdhury  David R. Lentz 《Journal of Geochemical Exploration》2011

Skarn rocks occur at the contact between calcite-bearing dolomitic marbles and granitoids (massive varieties with pegmatites) in close spatial association with the mica schist-hosted Proterozoic Pb–Cu–Ag sulfide deposits at Sargipali, Sundergarh District, Eastern India. The exoskarn (pyroxene–garnet) of variable width (1 to 30 m) occurs in marble proximal to the granitic intrusion, and endoskarn (pyroxene–epidote) is variably developed (< 1 to 10 m). Molybdenum-free scheelite with minor pyrrhotite (0.2%) is found only in late garnet–clinopyroxene exoskarn assemblages.  相似文献