Asis Mazumdar

Assessment of ecosystem health of tropical shallow waterbodies in eastern India using turbulence model

In the present study, a numerical model of the hydrodynamic and thermal structure of artificial shallow lakes in eastern India has been developed as a tool to assess the ecological water quality, driven by the meteorological forcings. It allows quantification of the vertical mixing processes that govern not only the thermal structure but also nutrient exchanges and the distribution of dissolved and particulate matter among water layers. Vertical temperature profiles were calculated by solving coupled partial differential equations for temperature (heat energy balance equation), one-dimensional momentum equation and a second order closure scheme for small-scale turbulence effects, i.e. turbulent kinetic energy and turbulent dissipation rates numerically using an implicit time integration method. The effect of advection due to the inflow and outflow is not taken into consideration as these shallow waterbodies are assumed to behave as a closed lake. The oxygen level measured at different layers during the simulation period in these waterbodies reflects hypolimnetic oxygen depletion due to the thermal stratification in the aquatic environment. The changes in the stratification regime in these waterbodies are expected to affect the water quality and the health of the ecosystem, primarily based on temperature and dissolved oxygen parameter and in particular, the certain features of the oxygen resources of the hypolimnion.

Removal of arsenic from drinking water using dual treatment process

This paper focuses on determining an efficient and simple method to remove arsenic from groundwater. Arsenic is a naturally occurring element widely distributed in the earth’s crust. Arsenic is very toxic when found in large quantities in drinking water. This report documents the selected treatment method and laboratory experimentation of arsenic removal from drinking water in small water delivery systems and domestic water systems. The objective is to expand upon research of new and existing arsenic removal technologies or promote a new, alternative process. Several treatment technologies have been considered to perform this function, but cost and reliability concerns prompted the decision to analyze small-scale, community-based filtration units, specifically. Based upon initial test data, the use of dual treatment method comprising of oxidation-coagulation-filtration and adsorption by activated alumina has proven to be more economic having more capacity and superior reliability as compared to other arsenic removal processes using various other media.

An Introduction and Current Trends of Damodar and Rupnarayan River Network

Rivers are the important primary resource of landed community for their primary sustenance. Losses of navigability, gradient fall within a short distance, deltaic formations in lower reaches, anthropogenic actions or manipulations such as construction of embankments and guard walls, silt depositions or encroachment of river beds, monsoon induced changes, etc., can cause a river to die. As per the current status of West Bengal (Eastern part of India) and Jharkhand rivers, the effect of the creation of reservoirs, industrial extractions, and climate change can be observed easily. Damodar and Rupnarayan river systems are two major river networks of eastern India which are one of the major sources of water for irrigation, agriculture, and industrial purposes of the people living in the river banks. The present note tries to give an overview of the current trends, geomorphological characteristics, and economical resources of the two rivers which can give an idea of the impact of vulnerabilities on the natural water resources of the two catchments.

Turbulence flow field around two eccentric circular piers in scour hole

ABSTRACT Flow pattern at single pier has been extensively studied by several investigators, but scanty work is available on turbulent flow pattern around piers placed in close proximity. The work explained in this research is concerned with an experimental study of the horseshoe vortex flow pattern and characteristics in a local equilibrium scour hole around two identical circular piers placed in the longitudinal direction to the flow with an eccentricity (transverse distance). Instantaneous three-dimensional velocities were measured by using an acoustic Doppler Velocimeter (ADV). The contours and distributions of the time-averaged velocity components, turbulence intensities and turbulence kinetic energy are presented at different azimuthal planes: 0°, 45°, −45°, 90° and −90°. Velocity vectors obtained from time-averaged velocity fields are used to show further flow features. The vorticity and circulation of the horseshoe vortex are determined by using a forward difference technique of computational hydrodynamics and the Stokes theorem, respectively. The eccentric pier arrangement and the interference between the piers play an important role in the creation and formation of the greater scour depth at the eccentric rear pier. Vortex strength of the eccentric rear pier is found higher than the front pier.

Accumulation of Carbon Stock Through Plantation in Urban Area

Emission of carbon dioxide (CO2) in urban area is higher compared to the rural area due to the presence of different emission sources within a small area. Carbon is sequestered by the plant photosynthesis and stored as biomass in different parts of the tree. Carbon sequestration rate (CSR) has been measured for young species (6 years age) of Albizzia lebbek in Indian Botanic Garden in Howrah district and Artocarpus integrifolia at Banobitan within Kolkata in the lower Gangetic plain of West Bengal in India by Automated Vaisala Made Instrument, GMP343 and aboveground biomass carbon has been analyzed by CHN analyzer. The specific objective of this article is to measure carbon sequestration rate and accumulation of biomass carbon stock of two young species of A. lebbek and A. integrifolia. The carbon sequestration rates (mean) as CO2 from the ambient air as obtained by A. lebbek and A. integrifolia were 14.86 and 4.22 g/h, respectively. The annual carbon sequestration rates from ambient air were estimated at 11.97 t C/ ha by A. lebbek and 3.33 t C/ha by A. integrifolia. The percentages of carbon content (except root) in the aboveground biomass of A. lebbek and A. integrifolia were 47.12 and 43.33, respectively. The total accumulated aboveground biomass carbon stocks in 6 years as estimated for A. lebbek and A. integrifolia were 6.26 and 7.28 t C/ha, respectively, in these forest stands. Therefore, urban plantation based on better carbon sequestrated species will help to accumulate more biomass carbon stock as well as to offset the increasing CO2 level in ambient air.

Mixing and Internal Waves in a Small Stratified Indian Lake: Subhas Sarobar

The formation and break-up or erosion of stratification is a major process in all natural and man-made lakes, which controls to a large extent the functioning of their ecosystems. The key challenge here is the specific role of shear generated and convective turbulence in the formation/destruction of stratification and their interactions with internal waves. Three aspects of hydrodynamics, i.e. the dynamical state, the physical mechanism and the energy level are very important elements in understanding problems of turbulent mixing and the formation of vertical thermal stratification. The result of the stratification is the formation of the seasonal thermocline.

Modification of Hunter’s Curve in the Perspective of Water Conservation

AbstractPlumbing-system designers, who routinely use Hunter’s curve for estimating domestic demand, actually solve complex problems based on the probabilistic approach. Recently, serious questions have arisen about the accuracy of Hunter’s curve. In some instances, using the curve to estimate the water-demand load has given highly inflated results. However, this consistent problem in applying the curve to design should in no way be interpreted as a criticism indicating that Hunter’s basic research and approach are incorrect. Many things have changed since 1940 when Roy B. Hunter’s BMS65 Methods of Estimating Loads in Plumbing Systems, was published as a national standard in the United States. In the context of water conservation, which should be the primary goal in the global water-stressed scenario, designers are giving importance to using low-water-use (demand) fixtures. Merely recommending the use of low-water-flow fixture cannot address the issue of water conservation. Hunter’s curve was based on 1940...

Estimation of Soil Carbon Stock and Soil Respiration Rate of Recreational and Natural Forests in India

Soil contains good amount of carbon stock. The amount of carbon stock depends on soil texture, climatic parameters, vegetation, land-use pattern, and soil moisture. The study has been conducted at four sites in the recreational and natural forests in India. The main objective of this study is to estimate the soil carbon stock and soil respiration rate of recreational and natural forests in plain land in eastern India. At Banobitan – a recreational forest, soil was slightly alkaline; moisture content ranged between 7.26% and 9.74%, and soil texture was sandy loam. Total carbon and soil organic carbon (SOC) ranged from 24.2 to 36.5 and 2.8–8.3 g/kg, respectively. At Indian Botanic Garden – a recreational forest, soil was slightly acidic in nature; moisture content varied between 16.2% and 21.7%, and soil texture was clayey loam. Total carbon and soil organic carbon in the soil varied between 58 and 80.1 and 8.3 and 12.6 g/kg, respectively. At Chandra – a natural forest, soil was slightly acidic in nature; moisture content ranged between 3.2% and 11.4%, and soil texture was sandy loam. Total carbon and soil organic carbon ranged from 15 to 23.2 and 1.4–1.5 g/kg, respectively. At Chilapata forest – a natural forest, soil was slightly acidic in nature; moisture content varied between 22.1% and 26.0% and soil texture was loamy. Total carbon and soil organic carbon in the soil varied between 45.7 and 62.5 and 7.4 and 12.8 g/kg, respectively. Estimated mean soil total carbon and mean soil organic carbon stock at Banobitan, Indian Botanic Garden, Chandra, and Chilapata forests were 43.70 and 7.99, 96.32 and 14.57, 27.31 and 2.07, and 75.52 and 13.73 Mg C/ha, respectively. Estimated annual soil respiration rates of Banobitan, Indian Botanic Garden, Chandra, and Chilapata were 2.07, 3.34, 0.61, and 4.18 t C/ha/year, respectively.

Determination of Urbanization Impact on Rain Water Quality with the Help of Water Quality Index and Urbanization Index

Rain water quality is a vital factor for deciding whether the water is drinkable or not. But increase in urbanization could degrade the quality of rain water. In the present study, rain water was collected from different sampling locations near and far from urban centers. The influences of urbanization were analyzed with the help of the relationship between water quality index (WQI) of the collected samples and urbanization index (UI) of the sampling location. The WQI was developed with the help of different water quality parameters and their standards. The index was developed as per the standards of drinking water prescribed by All India Public Health Engineering and with the help of “Water Classifier” software developed by Majumder (2008). The urbanization index for the present study was developed as a function of population density, change in population within sampling locations, and density of residential and commercial complexes areas within a radius of 5 km of the sampling locations. According to the results, the relationship between WQI and UI was inversely proportional in sampling locations of both South and North 24 Parganas, which are located in southern and northern outskirts of Kolkata but the slope of the relationship is more tilted in case of sampling points located in South 24 Parganas, than in case of the samples taken from North 24 Parganas. As most of the polluting commercial complexes (leather, textile) were situated in southern outskirts of Kolkata and huge number of residential complexes were present or in verge of completion in the region, there was a massive migration of population from different parts of Kolkata to South 24 Parganas, The service and IT sectors, the nonpolluting industries of Kolkata were concentrated in the northern outskirts. The justification of the relationship between WQI and UI in southern and northern outskirts of Kolkata can be attributed to the above fact. The present study, thus, concluded that there is an impact of urbanization on quality of rain water in Kolkata. The same study can be made in other metro cities of India to verify the veracity of the relationship. The present study was conducted with very few sampling locations but still the locations were situated in regions of different UI and WQI. The study can be repeated with more sampling locations within the city with samples, which have more diverse WQI and UI.

Impact of Climate Change on the Availability of Virtual Water Estimated with the Help of Distributed Neurogenetic Models

Impact of climate change on virtual water of a tropical multireservoir system was estimated with the help of models developed by neural network and genetic algorithm. Virtual water or embedded water or embodied water, or hidden water refers to the water used in the production of goods or services. For instance, it takes 1,300 m3 of water on an average to produce 1 t of wheat. The precise volume can be more or less depending on climatic conditions and agricultural practice. The virtual water has major impacts on productive use of water and global trade policy especially in water-scarce regions. The impact of climate change on virtual water could open a path for the efficient use of virtual water in the face of climatic uncertainties, which may directly impact availability of raw water. The present study tried to estimate the future virtual water with the help of neurogenetic models, which estimates stream flow as function of various hydrological, meterological variables, and basin characteristics. The models prepared were distributed in nature and also consider temporal variability. In total, two models were prepared with rainfall, time of concentration, and catchment loss as input and stream flow as output. One model was prepared by classifying the dataset, based on the magnitude of the variable, and the other model was prepared with normal dataset. First, the better performing model was identified and then output from RCM-PRECIS model was applied to the chosen model to estimate the impact of climate change on stream flow. The estimation results were used to calculate the amount of virtual water, and the result was compared with the present-day virtual water to analyze the change in virtual water availability due to climate change. According to the results, model prepared with normal dataset was identified as a better model, and from the estimations it could be concluded that virtual water availability would increase in case of both A2 and B2 scenario of climate change where the change would be more pronounced in case of the latter.