Amartya Kumar Bhattacharya

Modclark Model: Improvement and Application

This research is an investigation of a spatially distributed unit hydrograph model. The ModClark model (Peters and Easton, 1997) is an adaptation of Clarks unit hydrograph technique to accommodate gridded NEXRAD precipitation data. In this study, two features were added to the ModClark model: a spatially distributed loss model and a spatially distributed velocity field. A new formula to calculate the spatially distributed velocity field was derived. Maps of spatially distributed runoff curve numbers for Kansas and Oklahoma were developed. The improved ModClark model was applied to 25 storm events on six watersheds. The calibration results are excellent. Two global parameters, the time of concentration and the storage coefficient, were calibrated for each event. Based on the calibration results, two equations to estimate the time of concentration and the storage coefficient were developed. This model and the equations for the two parameters were applied to simulate four storm events on two watersheds. The results are satisfactory.

Significance of Hydro-geological and Hydro-chemical Analysis in the Evaluation of Groundwater Resources: A Case Study from the East Coast of India

The work described in this paper is aimed towards conducting a thorough and in-depth field based study on the groundwater development and water quality variation in the district of Purba Medinipur, West Bengal, India. 20 nos. locations were selected along the coastal belt of the study area to investigate the groundwater quality. Based on the field test results,contour line were plotted for Chloride concentration. The 3- Dimensional views of piezometric surface pre monsoon ( 2006 ), pre-monsoon and post-monsoon average piezometric surfaces (2004) had also been developed. The subsurface characterization and the groundwater quality analysis were thereafter utilized to obtain the probable path of saline water ingress into the aquifers of the study area. Owing to heterogeneity of the aquifer in the selected locations, the spatial irregularity in salinity was observed to be significant. The present study was carried out to understand the quality of ground water and delineate the subsurface formations in an area of Purba Midnapur district. The physico chemical studies involve pH value, hydraulic conductivity, total hardness, anions (HCO, Cl, CO) and Fe.

LAND SUBSIDENCE IN EAST CALCUTTA

In this paper two approaches have been mentioned to calculate subsidence. One is based on the linear theory (considering elastic property of the material) and the other on the logarithmic theory. In the linear theory coefficient of volume compressibility (denoted as mv) indicates the nature of soil towards compression and in the logarithmic theory compression index (denoted as Cc) indicates the same. The top 30 m. of the subsurface soil stratification in Calcutta generally indicates softer clayey soil in the first 15 m. having higher mv values and relatively stiffer clayey soil between 15 m. and 30 m. having lower mv values. Further below the compressibility of the layers diminishes due to increasing overburden pressure also. In the analysis section for subsidence in two localities in Central Calcutta, firstly data of soil characteristics and properties in different layers and change in piezometric level or depth of water table from 1956 to 2000 are represented. Based on these data intergranular pressures for different layers are calculated and finally total subsidence in the said time span is estimated using the linear theory. This comes out to be 0.3299 m (average) for East Calcutta region from 1956 to 2000 and hence estimated average subsidence rate is 7.50 mm/year.

Significance of Hydro-geological and Hydro-chemical Analysis in the Evaluation of Coastal Groundwater Resources in Eastern India

The work described in this paper is aimed towards conducting a thorough and in-depth field based study on the groundwater development and water quality variation in the district of Purba Medinipur, West Bengal, India. 20 nos. locations were selected along the coastal belt of the study area to investigate the groundwater quality. Based on the field test results,contour line were plotted for Chloride concentration. The 3- Dimensional views of piezometric surface pre monsoon ( 2006 ), pre-monsoon and post-monsoon average piezometric surfaces (2004) had also been developed. The subsurface characterization and the groundwater quality analysis were thereafter utilized to obtain the probable path of saline water ingress into the aquifers of the study area. Owing to heterogeneity of the aquifer in the selected locations, the spatial irregularity in salinity was observed to be significant. The present study was carried out to understand the quality of ground water and delineate the subsurface formations in an area of Purba Midnapur district. The physico chemical studies involve pH value, hydraulic conductivity, total hardness, anions (HCO, Cl, CO) and Fe.

An Analytical Study of Flood Management in Bangladesh

Bangladesh along with the state of West Bengal in India is situated in the lowest area of the Hindu Kush - Himalayan Region (HKH) and is famous as one of the highest flood prone countries in the world. Flood to some extent is an annual expected and well-come event for many reasons for this country. But extreme flood inundates more than half of the countrys landmass causing immense suffering to the human life, damages properties and economy. Aim of the flood management in Bangladesh is to minimize damages or to avoid disastrous situation. Though the country is in the eastern part of the lowest ridge of HKH but geography and location of the country make hydrology of Bangladesh very diverse, complex and unique. The North-Eastern part of the country has the river networks with upper hilly catchments having one of the worlds highest rainfall intensity and causes frequent flash floods. In the North-Western part rainfall intensity is lower, higher altitude and mighty perennial river network causes river flood. The South-Eastern part has moderate rainfall intensity, hilly as well as coastal plain land, flashy and tidal river network causes both the storm surge and flash flood. The South Western region has also moderate rainfall, coastal plain land and tidal rivers cause storm surge due to cyclone. Principles of flood management in the country based on these different types of floods and geographical conditions either by non-structural or structural measures. As a non-structural measure for flood loss minimization, flood forecasting and warning services has been emphasized. Structural measures began in late 60s by implementing number of flood control projects.

Effect of Very Mild Random Tremors on Saturated Sub-surface Flow

Very mild random tremors in a saturated soil are not uncommon. Mild earthquakes, nearby piling, and the passage of underground trains all lead to vibrations in a manner that cannot be exactly predicted. High pore pressures and low effective stresses in cohesionless soil can lead to soil liquefaction and complete loss of bearing capacity of the soil. As long as the saturated sub-surface water flow is Darcian, the governing partial differential equation is elliptic in nature at all points in the flow domain. While analytical methods can be used in limited cases, numerical methods are universally available to find out the velocity components and pressure at all points in the flow domain. Tremors disrupt the steady-state flow of saturated sub-surface water. Velocity and pressure patterns vary in a random way. The possibility of saturated sub-surface water pressure mounting followed by soil liquefaction arises. In this chapter, canonical equations related to the finite element method have been considered, and the problem has been analysed.

An Innovative Methodology for Groundwater Management with Reference to Saline Water Intrusion

An innovative method of control of saltwater intrusion into the coastal aquifers has been suggested in this paper. A new method consists of withdrawal by qanat-well structures with reasonable compensation by rainwater harvesting by means of recharge ponds and recharge well. The salient features of the methodology are described by considering a design example adopted in the Contai Polytechnic Institute Campus of the district of Purba Midnapur in the state of West Bengal, India.