https://etd.iisc.ac.in/handle/2005/41 Tue, 07 Apr 2026 23:32:59 GMT 2026-04-07T23:32:59Z https://etd.iisc.ac.in/handle/2005/7914 Assessing the state of the glaciers in the Parvati basin of the Himalaya under a changing climate Pradeep, S The Himalayan cryosphere is one of the most climate-sensitive components of the Earth's system, acting as a critical water tower for millions of people across South Asia. Snow and glacier melt from this region contribute significantly to the headwaters of major rivers. However, rising temperatures and changing precipitation regimes over recent decades have led to changes in the cryosphere, including rapid glacier retreat, altered snowfall patterns, and the formation of glacial lakes, raising concerns over long-term water security, hazard risks, and ecological stability. Despite the importance of these dynamics, many existing assessments lack regional-scale resolution and overlook spatial heterogeneity in cryospheric processes. Hydrological modelling in the Himalaya has traditionally focused on larger river basins, offering limited insight into sub-basin scale responses and local community perspectives. This thesis addresses these gaps through a comprehensive, basin-specific inquiry into the cryospheric and hydrological evolution of the Parvati basin, Western Himalaya. The research is structured into three interlinked components: (i) quantification of glacier volume and mass changes, (ii) assessment of glacial lake formation, and (iii) simulation of future runoff under climate change scenarios using the Spatial Processes in Hydrology (SPHY) model, contextualized with field-based societal observations. The overarching aim is to enhance understanding of the coupled cryospheric-hydrological processes under present and projected climate scenarios, while incorporating perspectives from downstream communities. Chapter 2 evaluates glacier volume and mass changes in the Parvati basin to understand how regional glaciers have responded to recent climate shifts. Glacier volume for the year 2000 was estimated using a laminar flow-based approach and scaling relationships, providing a basin-wide assessment of ice reserves. To quantify mass loss over time, two complementary methods were applied: the Improved Accumulation Area Ratio (IAAR), based on climatic inputs, and the Geodetic method, using elevation data derived from satellite imagery. Both approaches indicate substantial glacier thinning and mass loss between 2000 and 2015, with an estimated reduction in glacier mass of around 14 percent. The results reveal marked spatial variability in glacier response, reflecting differences in elevation, slope, and debris cover. Together, the volume and mass balance estimates offer a regional-scale understanding of cryospheric change in the basin and establish a critical baseline for assessing future water availability and glacial hazards. Chapter 3 shifts focus to the potential formation of glacial lakes in response to continued glacier retreat and thinning due to climate change. As ice mass is lost and glacier surfaces lower, topographic depressions may become exposed, allowing meltwater to accumulate and form lakes, which can pose a significant risk of glacial lake outburst flood (GLOF). A semi-automated geospatial tool has been developed that identifies future lake formation sites by integrating modelled ice thickness with surrounding terrain features. Ice thickness is estimated using a laminar flow-based method that incorporates surface slope and ice velocity, while probable lake locations are inferred from bed topography and over-deepened glacier zones. Application of the tool to 132 glaciers in the Western Himalaya resulted in the identification of numerous potential glacial lake sites with implications for future water storage and downstream risk. These findings contribute to a better understanding of where and how deglaciation may reshape the Himalayan landscape and provide essential inputs for GLOF hazard assessments and regional hydrological modelling. Chapter 4 integrates the cryospheric insights into a distributed hydrological modelling framework using the SPHY model. The model incorporates dynamic glacier change and simulates runoff under four Coupled Model Intercomparison Project (CMIP) 6 scenarios (Shared Socio-economic Pathways (SSPs) 126, 245, 370, and 585) until 2050. Current simulations indicate a snow-dominated regime, with snowmelt and glacier-melt contributions to be around 42-47% and 21% of total runoff, respectively. Spatial decomposition shows increasing cryospheric contribution with elevation, with upstream sites like Tosh receiving higher contribution of their runoff from snowmelt. Future projections suggest show a progressive decline in snowmelt contributions and a rise in runoff from rainfall and baseflow, with notable increases in glacier runoff under higher emission scenarios. These trends imply reduced seasonal buffering, particularly during the late summer, with potential implications for water supply reliability. To contextualize these hydrological changes at the community level, a social survey was conducted in Pulga village, situated within the Parvati basin. The survey assessed water sources, agricultural practices, and perceptions of climate change. Findings reveal heavy dependence on snow and glacial-fed streams, with current changes in snowmelt timing raising uncertainty about the reliability of water sources in the future. Villagers reported diminished snowfall and earlier snowmelt, consistent with model outputs. Lack of irrigation infrastructure makes agriculture more vulnerable during dry months, despite sufficient drinking water. These insights highlight the need for basin-specific assessments that capture village-level variations in water availability and socio-aspects, which are often missed in broader hydrological studies. Collectively, this thesis makes a multi-spatio-temporal resolution assessment of climate change impacts on a Himalayan catchment. It (i) provides a detailed, spatially distributed record of glacier mass change, (ii) identifies zones of glacial lake development, and (iii) incorporates glacier information into a calibrated runoff model that accounts for cryospheric retreat. The inclusion of local knowledge through social surveys offers a novel linkage between scientific modelling and community-level water realities. By structuring the thesis as a staged assessment, from glacier retreat to lake formation potential, future hydrological changes, and social aspects, the research delivers an integrated narrative of Himalayan cryosphere-hydrology interactions under climate change. The work lays a foundation for further research and decision-support systems in Himalayan basins. It emphasizes the need for long-term in situ measurements, improved representation of permafrost and debris-covered ice in models, and enhanced coordination between physical science and regional water governance. Methodologically, it demonstrates the value of combining high-resolution remote sensing, empirical terrain analysis, distributed modelling, and community engagement to inform sustainable water management. The thesis contributes to broader climate resilience efforts by offering insights into how local hydrological regimes are being reshaped by global climate dynamics. https://etd.iisc.ac.in/handle/2005/7914 https://etd.iisc.ac.in/handle/2005/6970 Design, Optimization and Field Validation of Low Head Hydro Powered Turbine Pumps and Piston Pumps for driving stream flows in the range 40-120 l/s and 5-20 l/s respectively Unni, Rohan P This thesis focuses on developing optimized self-operating pumps using flows and head of perennial streams or rivers for decentralized irrigation and drinking water supply needs of local communities living by the river basins. The study identifies two flow zones for the identical head of 2-4 meters, where such hydro-powered pumps are in lacunae both from technological and market perspectives. The first flow zone is relatively higher flows from 40 to 120 l/s, which forms a gap between the capacity handling of classical ram pumps and modern axial flow propeller turbine pumps. The first problem is to design a propeller turbine for a real site in the field (Girdalpara village, Sukma, Chhattisgarh), carrying out lab and field tests in order to get the validation of the design. Further, this problem scales the propeller for flows ranging from 40 l/s to 250 l/s for over 4 site conditions. The first problem also identifies a couple of challenges to optimize the output (delivered) flow from the turbine pumps for identical head conditions (drive head to turbine and delivery head from pump). The first of this challenge is working on the pitch to chord length of the blades of the propeller so that efficiency can be increased for given head and flow, or adopting larger flow capacities for the same drive head and propeller diameter. This is investigated through CFD simulation and validated with lab results. It is found that efficiency can be retained, and overall pumping flow capacity can be increased by 5-10%. This finding has been proved for the village site Neelawaram in Sukma district. The second challenge of the turbine pump is related to the draft tube losses, which can be a serious threat to the efficiency of the pump. The second problem of the thesis is to tackle a flow zone of lower flows in the range of 5-20 l/s, which is currently managed by ram pumps for different sizes starting from 1 inch to 8-inch inlet drive pipes. However, it was evident from the previous field projects that the ram pumps have perpetual problems of repair and maintenance, as far as water hammer in the drive pipe along with the rubber clacks of the impulse/slam valves from previous field projects. that he participated. This led to finding an alternative technology, and one recent invention called the tyre piston pump was subjected to thorough investigation using physical experiments. A comprehensive theoretical framework of analysing this unconventional pump based on dimensional analysis was done, after which the experimental findings were superimposed. It was found that the pump was versatile for different flows for the same geometrical piston diameter and tyre diameter. One of the optimization techniques realized while increasing the piston diameter for the same tyre size, by which not only the output (delivered) flow increased, but also the operating efficiency. The d/D diameter was found to be an effective optimization tool with efficiencies nearing 40-45%, which was comparable with small turbine pumps and large ram pumps. Finally, the thesis concludes with the impact on the downstream ecosystem when a fixed quantity of flow is always taken out of the stream using any of the two technologies. While the hydrology of the stream defines the limiting flow that can be taken out from the given catchment, the author defines a head criterion, i.e. delivery to drive head for these pumps so the delivery flow can be standardized and matched with hydrological effluent behaviour of the river basin. This also adds to the social and economic perspective of water management, which brings with it a holistic essence to the application of hydro powered technologies. https://etd.iisc.ac.in/handle/2005/6970 https://etd.iisc.ac.in/handle/2005/6382 Ecology of the terrestrial carbon cycle: Influence of climate and animals Naidu, Dilip G T The terrestrial carbon (C) cycle involves fluxes between multiple pools that determine ecosystem functions and regulate global climate. These fluxes and pools are influenced by changes in abiotic (temperature, precipitation etc.) and biotic (animals, microbes, etc.) factors. In this thesis, I address three questions on how these abiotic and biotic drivers influence the size and stability of these fluxes and pools. In the first chapter, I investigate how covariation between decadal trends (2001-2019) in temperature and precipitation influence the two opposing C-fluxes in the soil-C pool – (1) C-influx through primary production (NPP), and (2) C-efflux through soil heterotrophic respiration (Rh). I estimate how any imbalance between these opposing fluxes affects the vulnerability of soil-C across the globe. I find that changes in C-influx may not compensate for rising C-efflux, under wetter and warmer conditions. Soil-C loss can occur in both tropics and at high latitudes, and precipitation emerged as the key determinant of soil-C vulnerability in a warmer world. This implies that hotspots for soil-C loss/gain can shift in the coming decades to make the soil-C pool vulnerable to climate change despite widespread increase in NPP across the world. In the second chapter, I explored the influence of climate on long-term correlations in vegetation fluctuations (i.e., persistence, measured by the Hurst exponent from time-series data). I found evidence for stronger persistence in warm and dry regions of the world, and there were non-linear relationships between persistence and two key climate variables (i.e., temperature and precipitation). While average temperature and precipitation together explained nearly three-fourths of the spatial variation in vegetation persistence, they had limited ability to explain the observed temporal changes in persistence. We find evidence for change in vegetation persistence across the globe driven by background change in climate. This provides some new insights into the resistance/resilience of vegetation in different ecosystems. In the third chapter, I investigated how animals – large mammalian herbivores – influence the terrestrial carbon cycle. Their influence on the size of the soil-C pool is well known, but how herbivores control the temporal stability of soil-C has remained largely unknown. I used a long-term field experiment in the Trans-Himalaya (2005-present) to estimate the consequences of herbivore-exclusion on interannual fluctuations in soil-C. I found high interannual variability in soil-C, and herbivores promote temporal stability of soil-C. Grazing by herbivores also mediated the influence of nitrogen on the stability on soil-C. Therefore, conserving large mammalian herbivores in grazing ecosystems can help achieve nature-based climate solutions. Overall, this thesis explores the linkages between three aspects of the terrestrial carbon cycle and climate, and herbivores. It highlights the non-linearities in vegetation-soil-animal interactions which are important for the stability of the terrestrial carbon cycle. https://etd.iisc.ac.in/handle/2005/6382 https://etd.iisc.ac.in/handle/2005/7920 From Sanitation to Soil: Evaluating Faecal Sludge-Based Amendments for Nutrient Circularity and Sustainable Agriculture Ramakrishna, Girija Globally, especially across developing regions, cities face a dual challenge: managing faecal sludge (FS) from on-site sanitation systems in a safe and sustainable manner, while simultaneously restoring soils degraded by prolonged reliance on synthetic fertilisers. Synthetic fertilisers, though widely used, contribute significantly to greenhouse gas emissions—particularly nitrous oxide (N₂O)—and further degrade soil health over the long term. Meanwhile, the availability of traditional organic amendments such as farmyard manure (FYM) is declining due to reduced livestock ownership and changing rural livelihoods, creating resource constraints for nutrient recycling. With over 3.4 billion people lacking access to safely managed sanitation and climate-smart agriculture seeking alternatives to energy-intensive fertilisers, the reuse of FS has emerged as a promising circular solution. This intersection is particularly pronounced in India, where more than 60% of urban households depend on on-site sanitation systems for wastewater management, while large areas of agricultural land face nutrient depletion and declining organic carbon levels. Despite the nutrient richness and organic matter content of treated FS, its reuse remains largely informal, unregulated, and underexplored. Concerns over treatment variability, microbial safety, and the absence of national reuse standards continue to hinder its integration into mainstream nutrient recycling frameworks. Despite growing interest in FS reuse, key knowledge and implementation gaps persist. Most of the existing studies have overlooked the evaluation of FS quality specifically in relation to soil application and its suitability for agriculture. Comprehensive assessments of agronomic performance and microbial safety under field conditions—particularly in comparison with widely used organic amendments and synthetic fertilisers—remain scarce. There is also limited evidence on how treatment variability influences immediate and residual nutrient availability and microbial contamination risks across diverse cropping systems. Furthermore, the absence of national regulatory benchmarks for FS use in India makes it challenging to assess risks and develop safe, context-specific reuse guidelines. This thesis addresses the interconnected scientific, policy, and agronomic gaps by providing a comprehensive assessment of the characteristics, agronomic performance, and safety of FS-based amendments derived from nature-based treatment systems—widely used in India and other developing regions. Drawing on faecal sludge characterisation, two-season field trials across diverse cropping systems, and a global regulatory review, the study provides new insights into the suitability of FS products for safe agricultural use. The research evaluates their comparative performance with conventional organic and synthetic fertilisers and develops comprehensive quality criteria tailored to FS reuse in agriculture. The findings culminate in evidence-based recommendations to support the safe, context-specific application of FS within sustainable nutrient management strategies. The first component of the study characterises FS products from three widely used nature-based treatment processes in India: unplanted drying beds, planted drying beds, and co-composting units, with a focus on their soil application potential. Thirty samples collected from full-scale treatment sites were analysed for physicochemical parameters, plant essential nutrients (macronutrients, micronutrients), and heavy metals. The treatment processes significantly influenced the faecal sludge properties, revealing significant differences in conductivity, total organic carbon, total nitrogen, and total potassium content. Co-composting resulted in higher conductivity (4.9 dS/m) and potassium content (1.09%) but lower total nitrogen (2.15%) and organic carbon contents (28%). The results revealed a balanced nutrient profile with a wide range of micronutrients and high variability. All products met the Indian Fertiliser Control Order (FCO) standards for composts, including thresholds for heavy metals, confirming their suitability for agricultural use. These findings underscore the need to consider treatment processes in shaping FS quality and inform soil application rate and recommendations tailored to sludge source and crop type. The second and third components of this research assessed the agronomic performance and microbial safety of FS-based amendments through two field experiments involving diverse cropping systems—maize–cowpea and fenugreek–radish—over two growing seasons. The study compared three FS-based products (unplanted drying bed sludge, planted drying bed sludge, and co-compost) against conventional inputs including farmyard manure (FYM), city compost, synthetic fertilisers, and a control. FS-based amendments achieved 85–90% of the yields of maize and fenugreek (first-season crops) relative to synthetic fertilisers. In the second-season crops (cowpea and radish), FS treatments outperformed synthetic fertilisers and matched the performance of FYM. FS products consistently enhanced yields, as well as crop nitrogen and protein content, with results comparable to those of conventional fertilisers. Soil nutrient assessments indicated that FS amendments improved nitrogen and organic carbon levels, sustained nutrient availability across seasons, and outperformed synthetic fertilisers in secondary macronutrients. Microbial safety—a major barrier to FS reuse—was assessed by analysing edible plant parts (cobs, seeds, roots, and leaves) for E. coli and faecal coliforms. Across both cropping systems, produce from FS-amended plots consistently showed microbial contamination levels within acceptable limits set by global safety standards, particularly when appropriate waiting periods and postharvest hygiene practices were followed. Maize cobs, cowpea plants, and seeds exhibited minimal contamination, meeting global safety benchmarks. In contrast, fenugreek displayed elevated contamination levels, largely attributed to early harvest and surface exposure, whereas radish—harvested five months after amendment application and analysed post-washing—demonstrated consistently low contamination. Importantly, indicator organisms were also detected in plots treated with FYM and city compost, underscoring that microbial risk is not unique to FS products. Contamination was additionally observed in control and synthetic treatments, suggesting environmental exposure as a contributing factor. Among the FS products, co-composted FS emerged as the safest treatment, yielding produce with the lowest contamination levels. These findings provide evidence that, when properly treated and managed, FS-based amendments can perform on par with conventional organic inputs in terms of microbial safety. They underscore the importance of treatment quality, crop selection, harvest timing, and hygiene practices in mitigating microbial risks across all organic fertilisers. Overall, the study demonstrates that stabilised FS-based amendments, when properly treated and managed, can safely enhance crop productivity and soil health. They offer a viable alternative to traditional organic inputs and serve as a complementary strategy to synthetic fertilisers within regulated, sustainable nutrient recycling frameworks. The fourth component of this research presents a comparative review of international regulations governing sludge reuse across 35 countries. It traces the evolution of quality standards—from early emphasis on heavy metal thresholds to more comprehensive frameworks encompassing pathogens, emerging contaminants, and physicochemical criteria. However, most global regulations are designed for sewage sludge from centralized systems, with limited attention to faecal sludge (FS) from on-site sanitation systems, which predominate in developing regions. Due to fundamental differences in composition, sewage sludge guidelines cannot be directly applied to FS. Addressing this regulatory void, the study proposes a draft set of quality criteria tailored to Indian conditions. Drawing from international benchmarks and national guidelines, the proposed framework outlines limits for nutrients, heavy metals, pathogen indicators, and key physicochemical parameters relevant to agricultural application. These recommendations offer a foundational step toward developing national standards that enable safe, regulated FS reuse—balancing agronomic benefits with public health protections. Together, the thesis presents one of the first integrated studies in India that combines sludge characterisation, comprehensive field-level agronomic trials across diverse cropping systems, and regulatory policy analysis to holistically evaluate FS reuse potential. It advances the science of sludge-to-soil recycling by showing that FS amendments—when properly treated, timed, and managed—can deliver agronomic benefits comparable to traditional fertilisers. The work also contributes a policy-ready, evidence-based framework to support the broader goals of resource circularity and sustainable agriculture. Several novel contributions emerge from this research. First, it establishes the critical role of treatment processes in determining the agronomic suitability of FS products. Second, it provides robust, field-level validation of FS reuse across diverse cropping systems under real-world conditions, benchmarked against conventional fertilisers. Third, it introduces a context-specific regulatory framework—addressing a long-standing policy vacuum around FS reuse in India. Finally, the thesis outlines key directions for future research, including the long-term cumulative impacts of FS application, tracking of specific pathogenic strains, socio-economic factors affecting adoption, and comparative climate impacts of sludge reuse versus conventional fertilisers. By linking science, agriculture, and sanitation policy, this thesis seeks to shift the conversation on faecal sludge from a waste disposal problem to a resource opportunity. In doing so, it contributes to advancing sustainable agriculture, closing nutrient loops, and promoting climate-resilient development—both in India and beyond. https://etd.iisc.ac.in/handle/2005/7920