https://etd.iisc.ac.in/handle/2005/30 Fri, 17 Apr 2026 19:51:27 GMT 2026-04-17T19:51:27Z https://etd.iisc.ac.in/handle/2005/6024 Anthropogenic Influence on River Water Quality Santy, Sneha Anthropogenic factors such as climate change, land use land cover change and industrial and population growth can influence river water quality. Climate change affects water quality due to changes in stream temperature and streamflow due to increased air temperature and varied precipitation patterns associated with warming. Land use land cover influences water quality mainly from the agricultural runoff, which carries the pollutants from fertilizers and pesticides and reaches the nearby water body. Population growth can increase the water demand and sewage generated hence aggravating pollution. Industrial growth has the potential to affect water quality through increased effluent loads. The work presented in this thesis contributes to quantifying such anthropogenic influences on river water quality using a coupled hydrological-water quality simulation model. The study area considered is a 238km stretch of Ganga river in India from Ankinghat to Shahzadpur, passing through Kanpur, which is identified as the most polluted stretch of Ganga river by the Central Pollution Control Board of India. Sensitivity studies with forcings such as climate change and land use are extremely important for any management decision on water quality. In the initial part of the thesis, the sensitivity of nine water quality parameters to climate change and land use change is assessed using idealized scenarios and a standalone water quality simulation model, QUAL2K. The key input model parameters contributing to model uncertainty and key locations are identified using first order reliability analysis. The water quality parameters considered are DO, BOD, ammonia, nitrate, total nitrogen, organic-, inorganic-, and total phosphorous and faecal coliform. The non-point source pollution is quantified using the export coefficient method, in which pollutants from all land use classes are considered. Eight climate change and six land use land cover scenarios are framed based on historical data analysis to assess their sensitivity to water quality parameters. DO is the most sensitive indicator to the climate change scenarios considered, while nutrients and faecal coliform are more sensitive to the land use scenarios. In general, the water quality parameters are found to improve with a rise in air temperature and deteriorate with a reduction in streamflow. An increase in the agricultural land area leads to higher nutrient concentration, while an increase in the built-up area causes an increase in faecal coliform concentration. An increase in forest land shows better water quality in terms of all water quality parameters. The key input variables contributing to the uncertainty of water quality simulation are the head water discharge, point and non-point pollution loadings, water temperature, and corresponding reaction rates. The key locations identified using first order reliability analysis are Kanpur downstream and Jajmau downstream. Risk assessment studies on water quality for future scenarios are limited in the literature. In the next part of the thesis, the effect of climate change on water quality, the risk of eutrophication and fish kill for the mid-and end of the 21st century for this river stretch are assessed. The risk of eutrophication and fish kill are quantified using simulated concentrations of nutrients and DO, respectively. Downscaled climate change projections for two climate change scenarios (RCP4.5 and RCP8.5) are used to drive a hydrological model coupled with a water quality simulation model. The simulations indicate a potential deterioration of water quality in this stretch in the mid-21st century, with a potential increase in pollutant concentration by more than 50% due to climate change alone. The risk of reduced dissolved oxygen and increased organic and nutrient pollution, and the risk of eutrophication and fish kills increase with warming due to the rise in the frequency of low-flow events and a reduction in streamflow during low-flow events. However, the risk of nitrate and microbial pollution is reduced due to increased denitrification and pathogen decay rates with warming. The risk of eutrophication and fish kill is found to increase by 43.5% and 15% due to climate change alone by the mid-21st century. The risk of eutrophication is found to increase by 6% due to land use change which can be attributed to an increase in nutrient loading with land use change. In the final part of the thesis, the individual effects of climate change, land use land cover change, population and industrial growth on river water quality are assessed with a coupled hydrological-water quality simulation model and the predominant factor contributing to pollution is identified. Also, the future water quality is projected for mid 21st century considering climate change, land use projections, population and industrial growth, and the proposed treatment for the stretch considered using socio-environmental scenarios. The effectiveness of the proposed treatment to offset the reduction in water quality from anthropogenic forcings is also assessed. The climate change effect is found to have a larger effect on water quality than other drivers, with a percentage contribution of above 70% because of the considerable sensitivity of water quality parameters to the amount of streamflow. Climate change projections combined with socio-environmental scenarios imply that the large increase in pollution due to climate change, land use land cover, industry, and population growth cannot be controlled by the current treatment proposals for 2050 by the authorities. However, providing adequate STPs to meet the population of 2050, and allowing only domestic sewage to reach STPs can help in achieving the objective of the Ganga Action Plan in the mid-21st century. The thesis comprises of five chapters. An introduction to the problem addressed, and the objectives of the work presented in the thesis are provided in Chapter 1. Details of the case study and analysis of the sensitivity of water quality parameters to climate change and land use with idealized future scenarios are discussed in Chapter 2. In Chapter 3, the risk assessment of low water quality, eutrophication and fish kill under changing climate and land use land cover is presented. Chapter 4 presents the analysis of the individual effects of all external forcings, including climate change, land use change, population and industrial growth. Conclusions drawn from the study are presented in Chapter 5. https://etd.iisc.ac.in/handle/2005/6024 https://etd.iisc.ac.in/handle/2005/6761 Design and Development of Biomimetic Sensor Technologies for the Identification of Emerging Contaminants Pavithra, N Sensors play a crucial role in addressing the need for the detection of antibiotics as emerging contaminants in water. The widespread use of pharmaceuticals/antibiotics in various sectors, including healthcare and agriculture, has led to their increased presence in water sources, posing a potential threat to both human health and the environment. Antibiotics in water can cause the development of antibiotic-resistant bacteria, a significant public health concern. Chemical/biosensors offer a rapid and sensitive means of detecting trace levels of antibiotics in water, enabling early identification of contamination. This early detection is essential for implementing timely mitigation strategies and preventing the further spread of antibiotic residues. Moreover, chemical/biosensors provide a cost-effective solution compared to traditional laboratory methods. Their ability to operate in real-time enhances the capability to assess the dynamic nature of antibiotic contamination. As of the present date, a multitude of sensing systems and methodologies have been devised. However, the widespread commercialization and large scale deployment of these sensors are impeded by their constrained sensitivity, selectivity, and environmental stability. The thesis, titled “Design and Development of Biomimetic Sensor Technologies for the Identification of Emerging Contaminants" seeks to address some pharmaceuticals that are emerging pollutants and metal ions in aqueous streams by proposing solutions to enhance the sensor characteristics through chemical/biosensors. Through systematic investigation and development, this research aims to contribute advancements that will facilitate the practical application and broader implementation of sensing technologies in environmental monitoring and the healthcare sector. Within the framework of this thesis, there is an in-depth exploration of the design and development of innovative sensing materials and analytical methods, with a particular focus on addressing emerging contaminants/pharmaceuticals and metal ions. The research employs biomimicking techniques to achieve the objectives. A systematic approach was adopted, commencing with the identification of the analyte and extending to the thorough evaluation of sensor parameters. Tetracyclines were selected as the primary analyte of interest due to their extensive usage against gram-positive and gram-negative bacteria, ranking as the second most widely used antibiotics globally, following penicillin. Dopamine emerged as a secondary analyte of interest, chosen for its relevance, as its concentration significantly impacts individual health. Additionally, tryptophan, an essential amino acid, levothyroxine provided as a supplement for thyroid deficiency, sodium ions indicative of hydration status through sweat analysis, and magnesium ions were chosen as analytes for comprehensive investigation within the thesis. This selection reflects a deliberate and diverse approach aimed at addressing various aspects relevant to environmental and human health. https://etd.iisc.ac.in/handle/2005/6761 https://etd.iisc.ac.in/handle/2005/6905 A Geochemical, Sr isotopic, and numerical study of river water, groundwater, and sea water interaction in the tidally dominated Hooghly (Ganga) estuary Panda, Biswajit An estuary is a partially enclosed, coastal water body where freshwater from rivers and streams mixes with saline water from the ocean. It is a dynamic system that is characterized by large changes in water chemistry (e.g., salinity) as well as water volume (tidal effects). Additionally, high nutrient availability makes estuaries productive ecosystems and the access to natural resources and water makes these regions densely populated. This thesis focuses on river water-groundwater-seawater interactions in the Ganga estuary in India (Hooghly estuary) and attempts to quantify the seasonally resolved groundwater discharge in this estuary. River water samples from the Hooghly estuary were collected during four seasons (monsoon and non-monsoon over two years between 2019-2021) over 200 km inland from the mouth of the river at Bakkhali (Bay of Bengal), covering both the estuary and the tidal river sections. Surface river water over varying salinities (0.1-25 psu) (n = 84) as well as depth-dependent river water samples (n = 17) from selected locations were collected. Additionally, suspended sediments from selected locations (n = 20) were analysed along with groundwater samples (n = 21) collected from both banks of the river. In-house measurements of cation concentrations using ICP-OES/ICPMS, anion concentrations using an ion-chromatograph and radiogenic Sr isotopes (87Sr/86Sr) using a thermal ionization mass spectrometer (TIMS) were performed on these samples. This study characterized the boundary between the tidal river section (no salinity changes with tidal action) and the estuary of the Hooghly River geochemically. The salinity change across the estuary over different seasons was modelled using an existing relationship of soil moisture equation with modified variables. Selected cations (Na+, K+, Ca2+, Mg2+, Sr2+) and anions (Cl-, SO42-) in all the surface water samples from the mid-stream, irrespective of sampling season, demonstrated conservative mixing between the fresh water and the surface Bay of Bengal end member. However, the surface river water 87Sr/86Sr demonstrated a non-conservative behaviour. The depth-dependent samples helped us in classifying the Hooghly estuary into Type 1 (well-mixed) based on established classification criteria. The 87Sr/86Sr of the depth-dependent samples also demonstrated a non-conservative behaviour in both the pre-monsoon and monsoon seasons indicating additional inputs of Sr into the estuary. To investigate the additional source(s) contributing the Sr with unique 87Sr/86Sr, selected sediment samples and groundwater samples were analysed. The 87Sr/86Sr of the groundwater showed limited variability and indicates enhanced dissolution of detrital carbonates in the west bank aquifer of the Hooghly estuary. The anion data is indicative of possible anthropogenic contamination. On he multi-endmember mixing plot of 87Sr/86Sr and Sr, the groundwater composition is best explained by mixing between the sediments and the river water, which indicates a strong interaction between the river and the aquifer. The major, trace, including rare earth elements (REE), concentration data for the suspended sediments show limited variations across salinity, depth, and season. The REE pattern demonstrated an average upper continental crust (UCC) like signature with a prominent Gd peak suggesting a possible anthropogenic input. A key observation is the significant difference between the 87Sr/86Sr of the sediments and the dissolved load indicating that there is a lack of equilibration between the dissolved and the suspended phases. The sediment 87Sr/86Sr is highly radiogenic and reflects the signatures of the Himalayan source rocks. The suspended sediments can be traced to their parent High Himalayan Crystalline series rock with additional input from the lesser Himalayas and meta-carbonates. The geochemical and isotopic compositions of surface river water, depth river water, groundwater, and sediments all indicate input of groundwater into the Hooghly estuary. Using mass balance considerations, the percent contribution of the groundwater to the estuary across seasons was estimated to be between 3 and 40%. To verify the results from the geochemical estimates, a numerical model using MODFLOW-SEAWAT was constructed based on the geometry of the Hooghly River cross sections, and using previously observed groundwater table conditions, tidal variations. and aquifer properties. The model was able to capture the diurnal nature of the bank seepage in a tidally dominated environment and demonstrated the invariability of the bank seepage with respect to tide induced salinity change. The model-estimates of groundwater seepage into the estuary broadly overlap but are on the higher side of the geochemical estimates. Overall, this study characterized the Hooghly (Ganga) estuary geochemically by analysing spatially distributed, including depth-dependent, river water samples across different seasons, over a duration of two years. Geochemical and radiogenic Sr isotopic data of the water samples and suspended sediments show lack of isotopic equilibration between the dissolved and suspended loads, while a non-conservative mixing in the Sr isotope space indicates seasonally varying contribution (3-40%) of groundwater to the estuary which was also verified using numerical modelling. Groundwater compositions reflect dissolution of detrital aquifer carbonates as well as anthropogenic sources while suspended sediments reflect the compositions of Himalayan provenances. https://etd.iisc.ac.in/handle/2005/6905 https://etd.iisc.ac.in/handle/2005/6793 An Integrated Assessment of Carbon and Water Use Efficiencies over India using Remote Sensing Chakraborty, Abhishek Carbon use efficiency (CUE) and water use efficiency (WUE) are essential characteristics of ecosystem functioning to understand the strength of carbon allocated by the vegetation as biomass from the sequestered atmospheric carbon and the strength of the linkages between the terrestrial carbon and water cycles, respectively. Knowledge of CUE and WUE at a fine spatiotemporal scale is vital for sustainable management, especially in a country like India, which exhibits diverse ecological and geographical gradients. Remote sensing offers continuous temporal monitoring and a spatially comprehensive understanding of CUE and WUE, making it a valuable tool for understanding the CUE and WUE at finer scales. Most previous studies have attempted to understand the impacts on the Indian ecosystem's carbon and water cycles using CUE and WUE separately. However, there is a lack of research on integrating CUE and WUE in a single framework. Such an integrated approach holds prominence in interpreting the tradeoffs and synergies between ecosystem carbon sequestration and water loss under variable climate and anthropogenic stress conditions prominent in the Indian context. This thesis aims to assess the spatiotemporal variability of CUE and WUE using remote sensing, focusing on comprehending the trends and drivers. The knowledge of sub-annual scale CUE is limited at a finer spatial scale due to a lack of insights on the net primary productivity. The thesis includes the development of a sub-annual (8-day scale) CUE product using an empirical framework that significantly correlates with in-situ-based data across India. Furthermore, the spatial patterns, role of drivers, sustainability, and resilience of vegetation carbon stocks are identified using CUE as a proxy. The results indicate a substantial control of soil moisture-temperature interplay and land management practices on CUE across India. A focus on the impact of the water table depth (WTD) dynamics on India's CUE and WUE is necessary, especially in the background of groundwater depletion across Indian landscapes. The standalone impact of WTD on CUE and WUE is considered, and the findings reveal that a combination of the regional climate, aquifer geology, and land management practices determine the WTD responses to the CUE and WUE. Moreover, a holistic understanding of India's long-term [1982-2018] ecosystem health is performed by combining the trends and resilience of CUE and WUE and examining the influences of water deficit on CUE and WUE. The results indicate an improvement in India's ecosystem health after the start of the 21st century, possibly due to a paradigm shift in irrigation technologies across India; however, a string of drought events resulted in exacerbated ecosystem health. The insights gained from this thesis can aid ecosystem managers and policymakers in identifying the hotspots of ecosystem degradation and providing sustainable management practices to optimize the carbon uptake at the cost of the most negligible water loss for India. https://etd.iisc.ac.in/handle/2005/6793