Inorganic pollutants in the Padma River, Bangladesh

The water and bed-sediment pollution status of the Padma River was determined by analysis of representative samples for selected metals and ions. Water and bed-sediment samples were collected at a T-dam, Rajshahi, Bangladesh, for 7 months. Water and silt-metal content analysis was performed using atomic absorption spectrophotometry or other analytical methods. The data showed the variation of the metal ion-levels in water as follows: Ca 17.11–48.37 ppm, Na 17.51–20.09 ppm, K 1.00–3.60 ppm, Cr 2.80–7.00 ppm, and SO₄ 4.17–5.48 ppm; in bed sediment, the levels were Cr 35–1050 ppm and Pb 12–48 ppm. The occurrence of Na, K and Ca was in the normal range (US EPA permissible limit), but the levels of Cr in water were much higher than the permissible limit. The SO₄ ion content was well below the pollution level. The concentration of Pb in the bed sediment was within the permissible limit for the standard International Atomic Energy Agency (IAEA) Soil-5a, but the concentration of Cr in the bed sediment was significantly higher than the permissible limit for the standard IAEA Soil-5a. Thus the Padma river water was polluted with Cr. The occurrence of some ions showed a monthly variation. Received: 19 August 1999 · Accepted: 12 October 1999     

Thin-layer element for interfaces and joints

The idea of using a thin solid element, called a thin-layer element, in soil-structure interaction and rock joints is proposed. A special constitutive model is used and various deformation modes such as no slip, slip, debonding and rebonding are incorporated. The shear stiffness is found from special laboratory tests and the normal stiffness is assumed to be composed of participation of the thin-layer element and the adjoining solid elements. A parametric study shows that the thickness of the thin-layer element can be such that the ratio of thickness to (mean) dimension of the adjacent element is in the range of 0.01 to 0.1. A number of simple and practical problems are solved to illustrate the success of the thin-layer element for soil-structure interaction problems.     

Response of wheat plants to sodium and calcium ion interaction under saline environment

Wheat being a glycophyte crop, responds differently to saline-sodic soil environmental conditions. The application of calcium is multidimensional with respect to sodium ion and plant part response. This study was conducted to record the response of shoot and root to sodium and calcium interaction under saline environment. Wheat seed of variety Punjab 85 were raised in quartz sand. Later on the seedlings were transplanted to pots containing Hoagland’s nutrient solution along with NaCl at 0 mM. and 50 mM. Calcium was applied as CaSO₂ 2H₂O at 3 mM. and 6 mM. Under saline conditions shoot showed positive response to sodium ion in the presence of higher calcium. Relative water contents were higher in the root system at 6 mM of CaSO₄. 2H₂O under saline condition. Growth responses to potassium and Magnesium in the presence of sodium induced salinity with calcium ion interaction remained variable.     

Empirical and numerical analyses of support requirements for a diversion tunnel at the Boztepe dam site, eastern Turkey

This paper presents the engineering geological properties and support design of a planned diversion tunnel at the Boztepe dam site that contains units of basalt and tuffites. Empirical, theoretical and numerical approaches were used and compared in this study focusing on tunnel design safety. Rock masses at the site were characterized using three empirical methods, namely rock mass rating (RMR), rock mass quality (Q) and geological strength index (GSI). The RMR, Q and GSI ratings were determined by using field data and the mechanical properties of intact rock samples were evaluated in the laboratory. Support requirements were proposed accordingly in terms of different rock mass classification systems. The convergence–confinement method was used as the theoretical approach. Support systems were also analyzed using a commercial software based on the finite element method (FEM). The parameters calculated by empirical methods were used as input parameters for the FEM analysis. The results from the two methods were compared with each other. This comparison suggests that a more reliable and safe design could be achieved by using a combination of empirical, analytical and numerical approaches.     

Post-processing and forecasts updating in automated systems of flash flood forecasting

This paper completes the series of three articles devoted to automated forecasting of flash floods [3, 5] and describes an effective approach of forecast updating through post-processing operations, which can be useful only in conjunction with such fast and efficient real-time re-calibration algorithms as SLS-based methods are. In particular, a proposed methodology is aimed to reduce negative consequences of scarce or low-quality data that can corrupt optimized parameters and, therefore, lower forecasting efficiency. A new modification of SLS-based optimization that supposes simultaneous re-calibration of the model and correction of the model input by generating of ensemble noises (SLS-E) is presented.     

Species composition and forest structure in tropical moist deciduous forest of Bangladesh—a case study in Thakurgaon

This study was conducted in the tropical moist deciduous forest in Bangladesh to describe the species composition, diversity, and the forest structure. There were three plots established in Ranishonkoil, Ruhia, and Baliadangi forest beat in Thakurgaon. A total of 126 tree species, 1,991 stems (663 ha^?1) of ≥10-cm girth were listed. Tree communities in these forest region differed in dominance, composition, diversity, and structure; and tree stand density varied from 651 to 685 ha^?1. Species diversity (H¹) ranges from 3.11 to 3.48. Meliaceae, Myrtaceae, and Rubiaceae were the most abundant families within the three plot area. Study site 2 is more diverse at spatial scale and taxonomic levels due to high rainfall and favorable edaphic condition. This study will help the foresters as baseline information for monitoring and sustaining diversity of tropical moist deciduous forests in Bangladesh.     

Predictions of future hydrological conditions and contribution of snow and ice melt in total discharge of Shigar River Basin in Central Karakoram, Pakistan

The high mountains of Hindu-Kush Karakoram and Himalaya(HKKH) contain a large volume of snow and ice, which are the primary sources of water for the entire mountainous population of HKKH. Thus, knowledge of these available resources is very important in relation to their sustainable use. A Modified Positive Degree Day Model was used to simulate daily discharge with the contribution of snow and ice melt from the Shigar River Basin, Central Karakoram, Pakistan. The basin covers an area of 6,921 km2 with an elevation range of 2,204 to 8,611 m a.s.l.. Forty percent of the total area is glaciated among which 20% is covered by debris and remaining 80% by clean ice and permanent snow. To simulate daily discharge, the entire basin was divided into 26 altitude belts. Remotely sensed land cover types are derived by classifying Landsat images of 2009. Daily temperature and precipitation from Skardu meteorological station is used to calibrate the glacio-hydrological model as an input variable after correlating data with the Shigar station data(r=0.88). Local temperature lapse rate of 0.0075 °C/m is used. 2 °C critical temperature is used to separate rain and snow from precipitation. The model is calibrated for 1988~1991 and validated for 1992~1997. The model shows a good Nash-Sutcliffe efficiency and volume difference in calibration(0.86% and 0.90%) and validation(0.78% and 6.85%). Contribution of snow and ice melt in discharge is 32.37% in calibration period and 33.01% is validation period. The model is also used to predict future hydrological regime up to 2099 by using CORDEX South Asia RCM considering RCP4.5 and RCP8.5 climate scenarios.Predicted future snow and ice melt contributions in both RCP4.5 and RCP8.5 are 36% and 37%, respectively. Temperature seems to be more sensitive as compared to other input variables, which is why the contribution of snow and ice in discharge varies significantly throughout the whole century.     

Water quality variations in different climates of Iran: toward modeling total dissolved solid using soft computing techniques

In present paper, wavelet analysis of total dissolved solid that monitored at Nazlu Chay (northwest of Iran), Tajan (north of Iran), Zayandeh Rud (central of Iran) and Helleh (south of Iran) basins with various climatic conditions, have been studied. Daubechies wavelet at suitable level (db4) has been calculated for TDS of each selected basins. The performance of artificial neural networks (ANN), two different adaptive-neurofuzzy inference system (ANFIS) including ANFIS with grid partition (ANFIS-GP) and ANFIS with subtractive clustering (ANFIS-SC), gene expression programming (GEP), wavelet-ANN, wavelet-ANFIS and wavelet-GEP in predicting TDS of mentioned basins were assessed over a period of 20 years at twelve different hydrometric stations. EC (μmhos/cm), Na (meq L^?1) and Cl (meq L^?1) parameters were selected (based on Pearson correlation) as input variables to forecast amount of TDS in four studied basins. To develop hybrid wavelet-AI models, the original observed data series was decomposed into sub-time series using Daubechies wavelets at suitable level for each basin. Based on the statistical criteria of correlation coefficient (R), root mean square error (RMSE) and mean absolute error (MAE), the hybrid wavelet-AI models performance were better than single AI models in all basins. A comparison was made between these artificial intelligence approaches which emphasized the superiority of wavelet-GEP over the other intelligent models with amount of RMSE 18.978, 6.774, 9.639 and 318.363 mg/l, in Nazlu Chay, Tajan, Zayandeh Rud and Helleh basins, respectively.