http://localhost:8081/jspui/handle/123456789/31 2026-04-21T09:27:23Z 2026-04-21T09:27:23Z Dhamija, Sana http://localhost:8081/jspui/handle/123456789/20338 2026-04-09T07:57:00Z 2024-04-01T00:00:00Z

Title: GEOSTATISTICAL MODELLING, PLANT UPTAKE AND HUMAN HEALTH RISK ASSESSMENT OF ARSENIC IN GANGA BASIN, INDIA Authors: Dhamija, Sana Abstract: Arsenic (As) pollution has become a global concern due to its toxic and carcinogenic nature. Surface water sources are more amenable to pollution; therefore, the usage of groundwater increased rapidly. In order to ensure effective protection of groundwater sources, it is essential to take into account all geogenic and anthropogenic pollutants along with the related activities that may present a potential risk. Assessment of groundwater vulnerability to arsenic hazard may thus be considered a potentially valuable management tool for enabling major decisions on preventive groundwater protection, and there is an urgent need to develop a robust approach for the same. Groundwater vulnerability to geogenic groundwater contamination underlies the complex interplay between various intrinsic geological, hydrogeological, and geochemical characteristics in an aquifer system. Identifying the risks to groundwater quality in this regard is a very engaging process that needs to consider the source and nature of groundwater contamination from the perspective of ongoing external and internal processes within the area/region under study. Arsenic contamination in groundwater has stood out due to its worldwide spread and lethality. It is an established fact that most arsenic sources are predominantly geogenic in nature. Yet, the mechanisms of its mobilization in groundwater appear to be triggered by anthropogenic factors often. However, the propositions are still being debated and are in an ever-evolving stage. Given the above facts, the current work attempted to provide a comprehensive review of the occurrence of arsenic in the subsurface environment, along with the earlier and recent methods involved in groundwater vulnerability assessment, including mathematical, geostatistical, process-based simulation, and machine learning approaches. There are no universally applicable approaches to date, each with pros and cons. The study considered and compared available case studies and highlighted the potential of an integrated/hybrid approach to achieve the best possible outcomes.

2024-04-01T00:00:00Z Beyene, Tegegn Kassa http://localhost:8081/jspui/handle/123456789/20318 2026-04-08T07:37:52Z 2023-11-01T00:00:00Z

Title: HYDROLOGICAL DROUGHT PROPAGATION AND VULNERABILITY IN ETHIOPIA Authors: Beyene, Tegegn Kassa Abstract: In Ethiopia, precipitation variability and extremes, often associated with large-scale climate anomalies, have led to frequent devastating droughts that impact livelihoods. The major energy production of the country relies on hydropower, and frequent droughts affect energy production due to the decline of streamflow. Therefore, understanding drought severity, duration, and spatial extent is crucial to mitigating drought-related impacts. The research investigates temporal and spatial precipitation extremes and their connection to climate indices. A total of eight extreme precipitation indices were selected to investigate precipitation variability, trends and change point. Wavelet coherence and correlation coefficient were used to identify the relationship between precipitation extremes and climate indices. Most precipitation extreme indices show an increasing trend over the south and southwest regions and a change in precipitation time series between 1990 and 2012. The multiscale analysis presents strong coherence between precipitation anomaly and Nino 3.4 and IOD over the south and southeast regions. Similarly, spatial correlation shows IOD and Nino 3.4 to have a positive correlation to most precipitation extreme indices over the country's south, southwest, and southeast parts. The Northern Atlantic Oscillation (NAO) climate index negatively correlates with most precipitation extremes. We further investigated the duration, severity, and propagation time of meteorological and hydrological drought. Our results reveal that the long-term pattern of meteorological and hydrological drought is increasing in most parts of Ethiopia, with the southern part experiencing a particularly noticeable trend. The spatial analysis indicates that basin characteristics highly influence the drought propagation time from meteorological to hydrological. Highland areas take less time (1 to 6 months) to propagate from meteorological to hydrological drought compared to lowland areas, which take an extended period (9 to 12 months). Furthermore, the research examines the impact of drought on streamflow in the selected sub-basins, providing insights into the recovery period of rivers after drought events. The study investigates meteorological and hydrological drought using multiscale standardized and anomaly drought indices in four sub-basins: Ethiopia's Genale, Tekeze, Awash, and Baro basins. Two Archimedean copulas (Clayton and Gumbel) were used to identify the joint return period between drought duration and severity. We computed the streamflow required to recover from hydrological drought for selected sub-basins. Results revealed that drought frequency has increased over most sub-basins over the last two decades. Tekeze and Baro sub-basins required more than 4BCM and 2.5BCM streamflow to recover from the fifteen-month drought duration. The shortest drought duration occurred for three months in the Awash sub-basin, requiring only 0.21BCM streamflow for drought recovery. Finally, our study addresses the challenge of limited spatial data by using remote sensing and reanalysis data to assess hydrological drought vulnerability in Ethiopia. The analytical hierarchy process (AHP) is employed to assign weightage values to various influencing factors, namely, Land use/land cover, soil texture, population density, elevation, drainage density, aridity index, slope, rainfall departure, and water storage deficit index. The study results categorized hydrological drought-vulnerable areas into six categories. Most of the highly vulnerable regions are in the northeast (lower Awash) and southeast lowlands (Wabi-Shebelle and Genale-Dawa basins). The southwest (most Baro-Akobo basin) part of the country falls under low to no vulnerability zones of hydrological drought, covering only 8% of the country's area.

2023-11-01T00:00:00Z Vishwakarma, Rajesh Kumar http://localhost:8081/jspui/handle/123456789/20301 2026-04-08T07:32:46Z 2024-06-01T00:00:00Z

Title: HYDROLOGICAL AND ENVIRONMENTAL ASSESMENT OF AN URBAN STORMWATER SYSTEM Authors: Vishwakarma, Rajesh Kumar Abstract: Over recent decades, the unprecedented pace of global urbanization has ushered in a multitude of challenges, with rapid drainage of stormwater emerging as a complex issue in burgeoning urban areas. This thesis addresses the imperative to evaluate the viability of metropolitan town stormwater drainage systems and seeks solutions to the challenges posed by urbanization. The Government of India's sub-committee for the development of "National Sustainable Habitat Parameters on Urban Stormwater Management" introduces key indices crucial for the planning, execution, and maintenance of sustainable stormwater management policies. Indices such as the Natural Drainage System Index (NDSI), Drainage Coverage Index (DCI), Permeability Index (PI), Water Bodies Rejuvenation Index (WBRI), Water Body Vulnerability Index (WBVI), Water Logging Index (WLI), Area Vulnerability Index (AWI), Stormwater Discharge Quality Index (SWDQI), and Rainfall Intensity Index (RII) were evaluated for tier-I (Delhi, Mumbai, and Chennai) and tier-II (Varanasi, Chandigarh, Roorkee) cities in India. The study employed the Analytical Hierarchy Process to rank these indices and derived an "Overall Sustainability Index" for each city, offering a nuanced understanding of their stormwater management policies. In tandem, the investigation shifts its focus to the sub-tropical urban area of Roorkee, conducting rainwater quality studies from 2016 to 2019. Results indicate alkaline precipitation events dominated by Ca2+ and HCO3-. Principal Component Analysis (PCA) and trajectory analysis shed light on ion sources and temporal variability, while the study hypothesizes anthropogenic contributions to sulphates and nitrates.

2024-06-01T00:00:00Z Ravikumar, Guntu http://localhost:8081/jspui/handle/123456789/20112 2026-03-31T12:23:14Z 2023-11-01T00:00:00Z

Title: INVESTIGATION OF CHARACTERISTICS, DRIVERS, AND PREDICTABILITY OF COMPOUND DRY AND HOT EXTREMES Authors: Ravikumar, Guntu Abstract: Compound drought and hot extremes (CDHE) are periods of prolonged dry and hot weather exhibiting adverse impacts on nature and humankind than their counterparts. Understanding compound extremes is in its infancy due to complex dynamical climate systems involving interactions and feedback with the different processes at different scales. A multitude of studies have investigated the characteristics, drivers, and future trends of CDHE. However, most of this research has focused on the hottest three-month period, with limited attention given to the Indian Summer Monsoon and its intraseasonal variability. This study has investigated the characteristics, drivers, and predictability of CDHEs during the ISM, considering intra-seasonal variation. Our detailed investigation of the last seven decades of CDHE during the Indian Summer Monsoon has shown alarming observations. Our results confirmed a threefold increase in CDHE frequency for the recent period (1977–2019) relative to the base period (1951–1976), exhibiting a strong spatial pattern. Further investigation revealed that CDHE likelihood and spatial diversity in CDHE occurrence is a function of the strong negative association between precipitation and temperature and soil moisture-temperature coupling, respectively. Investigation into the temporal evolution of CDHE confirms the strengthening of the negative association between precipitation and temperature, indicating a higher number of CDHEs in the future. Our complexity-based approach outperformed traditional and contemporary approaches in predicting CDHE at a seasonal scale on a grid resolution across India’s mainland. This thesis has employed a comprehensive approach, utilizing statistical methods and modelling techniques to investigate the various climatological and hydrological elements contributing to CDHEs. The overall contribution of this thesis demonstrates that CDHEs are the new normal and explains the spatial diversity of their likelihood with improved prediction accuracy.

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