GeoJournal - This paper examines the farm income differences, income inequality of farm households, parameters of income variability that ascertain vulnerability levels, and cost-income variability... 相似文献
Fluvio-deltaic aquifers are the primary source of drinking water for the people of Bangladesh. Such aquifers, which comprise the Ganges-Brahmaputra-Meghna Delta, are hydrogeologically heterogeneous. Because of widespread groundwater quality issues in Bangladesh, it is crucial to know the hydrostratigraphic architecture and hydrochemistry, as some aquifer units are contaminated, whereas others are safe. Geophysical methods provide a potentially effective and noninvasive method for extensive characterization of these aquifers. This study applies and investigates the limitations of using electrical resistivity imaging (ERI) for mapping the hydrostratigraphy and salinity of an aquifer-aquitard system adjacent to the Meghna River. Some electrical resistivity (ER) sections showed excellent correlation between resistivity and grain size. These suggest that ERI is a powerful tool for mapping internal aquifer architecture and their boundaries with finer-grained aquitards which clearly appear as low-ER zones. However, in parts of some ER sections, variations in electrical properties were determined by porewater resistivity. In these cases, low ER was indicative of brine and did not indicate the presence of finer-grained materials such as silt or clay. Accordingly, the following hydrostratigraphic zones with different resistivities were detected: (1) aquifers saturated with fresh groundwater, (2) a regional silt/clay aquitard, and (3) a deeper brine-saturated formation. In addition, shallow silt/clay pockets were detected close to the river and below the vadose zone. ERI is thus a promising technique for mapping aquifers versus aquitards; however, the observations are easily confounded by porewater salinity. In such cases, borehole information and groundwater salinity measurements are necessary for ground-truthing.
A simple theoretical approach to predict the deformation behaviour of soft ground reinforced by columnar inclusions such as stone columns./granular piles, sand compaction piles, lime or cement columns, etc., is presented in this paper. The analysis is performed based on the deformation properties of the column material and the surrounding soil. The interaction shear stresses between the column and the surrounding soil are considered to account for the stress transfer between the column and the soil. The solution is obtained by imposing compatibility between the displacements of the column and the soil for each element of the column-soil system. Numerical evaluations are made for a range of parameters to illustrate the influence of various parameters on the predictions. The proposed method is verified with finite element analysis and a reasonable agreement is obtained between the predictions. 相似文献
Stochastic Environmental Research and Risk Assessment - Drought is considered to be one of the most devastating natural hazards, causing widespread environmental and social damage in many parts of... 相似文献
Sediment samples were collected from ten selected sites of the lower Meghna River estuary,and six heavy metals were analyzed with Atomic Absorption Spectrophotometry(AAS)to assess the contamination level and the metals’association with sediment grain size.The current results revealed that the mean concentrations of the studied metals were ranked in descending order of iron(Fe)(1.29×103 mg/kg)>zinc(Zn)(42.41 mg/kg)>lead(Pb)(12.48 mg/kg)>chromium(Cr)(10.59 mg/kg)>copper(Cu)(6.22 mg/kg)>cadmium(Cd)(0.28 mg/kg).The geo-accumulation,contamination,and pollution load indexes suggested that the lower Meghna river estuary was not contaminated by Fe,Zn,Pb,Cr,and Cu.The mean size of the sediment ranged from 28.92 to 126.2 mm,and the Pearson correlation coefficient showed a significant association between Fe and Pb(coefficient of determination,r2=0.836;p<0.05),and no significant correlation was found between individual metals and grain size,indicating no or low influence on the metals distribution. 相似文献
The study analyzed the food security and dietary diversity of tea workers in Lakkatura Tea Garden and Ootterbhag Tea garden in greater Sylhet district of Bangladesh. A total of 200 respondents (100 from each tea estate) were interviewed to evaluate the food security and dietary diversity. The study found that average daily per capita calorie intake by tea workers was 2095.96 kcal. In addition, around 85.30% of the total calorie intake was received from the rice consumption. Average per capita daily intake of rice was estimated at 538.51 gm which is higher than the national average. It was also observed that 71.7 and 65.0% households were food secure in Lakkatura and Ootterbhag Tea garden, respectively. In Lakkatura Tea Garden, 61.67% tea workers have medium dietary diversity and in Ootterbhag Tea Estate 49.47% tea workers have low dietary diversity. Using the logit model analysis, this study provides food consumption patterns of tea workers and determine the factors responsible for food security. Household size, farm income and daily calorie intake were found having significant influence on households’ food security. For improving socioeconomic conditions of tea workers, educational institution should be set up to improve their educational status and government should give loans for them at a low interest rate and create alternative job opportunity in off season.
Oceanic tidal fluctuations which propagate long distances up coastal rivers can be exploited to constrain hydraulic properties of riverbank aquifers. These estimates, however, may be sensitive to degree of aquifer confinement and aquifer anisotropy. We analyzed the hydraulic properties of a tidally influenced aquifer along the Meghna River in Bangladesh using: (1) slug tests combined with drilling logs and surface resistivity to estimate Transmissivity (T); (2) a pumping test to estimate T and Storativity (S) and thus Aquifer Diffusivity (DPT); and (3) the observed reduction in the amplitude and velocity of a tidal pulse to calculate D using the Jacob‐Ferris analytical solution. Average Hydraulic Conductivity (K) and T estimated with slug tests and borehole lithology were 27.3 m/d and 564 m2/d, respectively. Values of T and S determined from the pumping test ranged from 400 to 500 m2/d and 1 to 5 × 10?4, respectively with DPT ranging from 9 to 40 × 105 m2/d. In contrast, D estimated from the Jacob‐Ferris model ranged from 0.5 to 9 × 104 m2/d. We hypothesized this error resulted from deviations of the real aquifer conditions from those assumed by the Jacob‐Ferris model. Using a 2D numerical model tidal pulses were simulated across a range of conditions and D was calculated with the Jacob‐Ferris model. Moderately confined (Ktop/Kaquifer < 0.01) or anisotropic aquifers (Kx/Kz > 10) yield D within a factor of 2 of the actual value. The order of magnitude difference in D between pumping test and Jacob‐Ferris model at our site argues for little confinement or anisotropy. 相似文献
