Papers by Dr. Sumedha Chakma
Process Safety and Environmental Protection
Environmental Monitoring and Assessment
MethodsX
Future climate projections are a vital source of information that aid in deriving effective mitig... more Future climate projections are a vital source of information that aid in deriving effective mitigation and adaptation measures. Due to the inherent uncertainty in these climate projections, quantification of uncertainty is essential for increasing its credibility in policymaking. While quantifying the uncertainty, often the possible dependency between the General Circulation Models (GCMs) due to their shared common model code, literature, ideas of representation processes, parameterization schemes, evaluation datasets etc., are ignored. As this will lead to wrong conclusions, the inter-model dependency and the respective independence weights need to be considered, for a realistic quantification of uncertainty. Here, we present the detailed step-wise methodology of a "mutual information based independence weight " framework, that accounts for the linear and nonlinear dependence between GCMs and the equitability property.
Soil erosion is a major environmental problem worldwide, and almost half of India’s total geograp... more Soil erosion is a major environmental problem worldwide, and almost half of India’s total geographical area is susceptible to it. The Revised Universal Soil Loss Equation (RUSLE) has been widely used globally to estimate soil erosion, and Soil erodibility factor, denoted by K-factor, is an essential component of RUSLE. Although previous studies have assessed soil erodibility in India, they have been limited to small scales such as watersheds or districts. A national scale assessment of soil erodibility doesn’t exist and is critical to developing a systematic understanding of soil erosion over India. In this study, we estimated soil erodibility factors over India using RUSLE Nomograph and Environmental Policy Integrated Climate (EPIC) model approaches at a high resolution of 250 m. Our results showed that the K-factor estimated using the Nomograph approach was more accurate than the observed soil erodibility factors. Additionally, we developed erodibility indices such as CR (Clay Rat...
Water science and technology library, 2023
Water science and technology library, 2023
<p>Groundwater is a key source of water used in many essential activities across th... more <p>Groundwater is a key source of water used in many essential activities across the world, including irrigation (42%), public water supply (36%), industrial uses (24%), and power production. Furthermore, the quality of groundwater is quickly degrading owing to uncontrolled operations. Most developing countries, including India, have polluted groundwater due to an oversupply of heavy metals, fluoride, rich nutrients, and hydrocarbons. Various technologies like the Pump & Treat method were used to treat it but they are very expensive and less effective, so there is a need to develop low cost and effective technology for its treatment. A Permeable Reactive Barrier (PRB) is an effective groundwater remediation method. The key advantage is that it does not require the running of pumps or treatment vessels, saving on operation and maintenance expenses and enabling the economic worth of property to be maintained during rehabilitation. The goal of this research is to find low-cost materials that can be employed as reactive materials in a PRB to remove inorganic pollutants from groundwater and the aquifer. To that end, numerous low-cost material samples were exposed to characterization tests, batch testing, and a washing process to analyze the material's adsorption and desorption capabilities at varied doses, concentrations, and contact periods. Few of the low-cost materials functioned admirably, removing all contaminants (>98%), whereas others were deemed inappropriate for several reasons. The best-performing material is then adopted for two bench-scale column tests to imitate the PRB.</p>
<p>Soil erosion has always been a threat to the environment and agricultural practi... more <p>Soil erosion has always been a threat to the environment and agricultural practices throughout the world. For a country like India, where agriculture contributes primarily to its economy, it becomes a major problem. Identifying these vulnerable regions and planning for mitigation is crucial for sustainable soil resource management. For this, mapping or modeling soil erosion at a national scale is required to understand the variability of soil losses throughout the country. Performing field-based experiments to estimate soil losses over a large country is always expensive and tedious. Revised Soil Loss Equation (RUSLE), an empirical model, has been more prominent worldwide due to its simplicity and less forcing data requirements. In this study, average annual Potential Soil Erosion (PSE) was estimated over India using IRED (Indian Rainfall Erosivity Dataset), ISED (Indian Soil Erodibility Dataset), SRTM (Shuttle Radar Topographic Mission), DEM (Digital Elevation Model), and LULC (Land-use/Land-cover) obtained from NRSC (National Remote Sensing Institute) India. PSE was further analyzed using LULC categories and soil types to visualize the impact of soil erosion in each class. As erosion significantly affected agricultural activities, financial losses over the nation were also estimated, considering the severity of soil erosion. Further, Sediment Delivery Ratio (SDR) and Specific Sediment Yield (SSY) were also mapped over the national boundary to visualize the actual soil displacement at a grid scale of 250 m. Using the SSY map, the incoming sediment load to reservoirs/dams/lakes was also estimated considering its watershed areas. This study will be helpful for the experts in the field of sustainable soil resources management for planning mitigation measurements against soil losses in India.</p><p><strong>Keywords: </strong>Soil Erosion, Sediment Yield, Sediment Delivery Ratio, India, RUSLE, LULC</p>
Simulation of fate and transport mechanisms in the porous systems from contaminant transport mode... more Simulation of fate and transport mechanisms in the porous systems from contaminant transport models are affected by uncertainty associated with input model parameters. Sensitivity analysis (SA) provides tools to quantify the sources of uncertainty to the variations in the model output metrics. To quantify the uncertainty associated with physical non-equilibrium contaminant transport model, global SA was conducted for the problem mimicking reactive transport in the saturated soil column conditions. Five global SA methods, namely Morris, RSA (Regionalized Sensitivity Analysis), Sobol, FAST (Fourier Amplitude Sensitivity Test), and PAWN, were tested based on the temporal moments of contaminant concentrations for two output metrics: zeroth temporal moment (ZTM) and mean residence time (MRT). The ranking order of ten input model parameters from global SA methods for two output metrics was compared. Morris SA implied that the ZTM at outlet of the soil column is highly sensitive to sorptio...
Journal of Earth System Science
Science of The Total Environment
Journal of Environmental Chemical Engineering
Modeling Earth Systems and Environment
Variably saturated flow in an unsaturated zone is a critical subject due to its diverse applicati... more Variably saturated flow in an unsaturated zone is a critical subject due to its diverse applications in earth science, waste management, agriculture, and geotechnical problems. The governing Richards equation (RE) of the mathematical models for unsaturated flow is very nonlinear, attracting researchers to solve it quickly and accurately. In this paper, a numerical model is proposed to solve mixed form of RE. In time, backward Euler method is implemented to discrete the equation, and in space, the equation is discretized by the finite difference method. Because of the dependence of both water content and unsaturated hydraulic conductivity on soil water pressure head, the equation must be solved iteratively using the Picard scheme. It is assumed that initial suction head is 1000 cm and suction head at top boundary is 75 cm throughout the simulation. The model is first tested for a homogenous soil water system using numerical simulation data from the literature. The comparison between simulated and observed value demonstrate that the new algorithm is robust and practical with fast convergence. Later, model is extended for layered soil water system assuming a constant pressure head surface boundary condition and van Genuchten parameter is used to define the soil constitutive relationship for each soil layer. The model shows promising results, allowing it to be used for further applications, such as managed aquifer recharge, plant water uptake, and coupled with the advection-dispersion transport equation to predict solute movement.
Global and Planetary Change
Springer International Publishing eBooks, 2022
Journal of Environmental Chemical Engineering
AGU Fall Meeting Abstracts, Dec 1, 2019
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Papers by Dr. Sumedha Chakma