Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
6 results
Search Results
Item Land cover change and its implication to hydrological regimes and soil erosion in Awash River basin, Ethiopia: a systematic review(Springer Science and Business Media Deutschland GmbH, 2021) Tola, S.Y.; Shetty, A.The Awash River basin is one of the most developed basins in Ethiopia, and its water resources are crucial to development. The collective impact of land cover (LC) changes has driven a difference in the hydrological components, substantially impacting the availability of water resources and demand. This review aimed (i) to examine the extent of change quantitatively and its effects; (ii) to analyze the relationship with a mean annual rainfall that would further reveal the causes and potential LC type response to hydrologic variables in the Awash River basin, Ethiopia. The results have revealed that urbanization and agricultural activities in the basin are the most trending types of LC, while the forest, shrubland, grassland, and pasture land have been decreasing significantly in the subbasins. As a result, the change in these subbasins has triggered hydrologic variations (runoff, groundwater flow, base flow, and evapotranspiration), and its impacts on downstream basins have mostly been flood and drought. In addition, farmland, urbanization, and shrubland trends showed a significant positive interaction, while forest and water bodies had a substantial and slight negative relation to mean annual rainfall, respectively. Vegetation, bareland, urbanization, and agriculture/farmland are directly responsible for the hydrologic variation. LC change significantly affected hydrologic regimes and the distribution of spatial rainfall is correlated significantly to LC change pattern. Besides, due to the lack of LC management practices, the impact continues to propagate. Hence, this review helps to portray the potential implications and extent of effects of changes in LC on the hydrological regimes. As a result, the implementation of sound water management strategies and practices in response to changing environments to resurrect water scarcity and mitigate flood and sediment are needed straightaway. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.Item Flood susceptibility modeling based on morphometric parameters in Upper Awash River basin, Ethiopia using geospatial techniques(Springer Science and Business Media Deutschland GmbH, 2022) Tola, S.Y.; Shetty, A.The hydrological response, such as direct surface runoff, is linked to the characteristics of the watershed. Evaluation and knowledge of geomorphometric parameters in relation to floods and the identification of specific flood-prone sites in the basin are critical for mitigation measures. Despite advancements in geospatial tools, the utilization of geospatial data in many river basins prone to flooding and erosion is minimal. Morphometric aspects: linear, areal, and relief analysis of the Upper Awash River basin were performed in four subbasins to better understand the hydrological signatures behaviour. The topographic wetness index (TWI) and topographic position index (TPI) were also used to determine the extent of inundation. The aggregated parameters revealed that SB-1 is highly susceptible to flooding, SB-3 and SB-4 are moderately susceptible, and SB-2 is low. However, based on the geomorphologic instantaneous unit hydrograph, SB-2 and SB-4 demonstrated rapid response and a high flood generating potential. The degree of susceptibility was determined by incorporating the TWI and TPI through overlay analysis. Overall, the Upper Awash River basin accounts for 23%, 42%, and 36% of the total bay has been classified as high, medium, and low flood-prone, respectively. According to the study, topographic indices (TWI and TPI) are critical attributes that show specific flood potential areas and inundation extents in addition to morphometric parameter-based flood susceptibility analysis. The analysis provided input for holistic water and soil erosion management by providing the hydrological behaviour of the stream, geomorphological characteristics, basin responsiveness, and stream power to flood potential and denudation characteristics in the subbasins. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.Item Quantification of change in land cover and rainfall variability impact on flood hydrology using a hydrological model in the Ethiopian river basin(Springer Science and Business Media Deutschland GmbH, 2023) Tola, S.Y.; Shetty, A.Changes in land cover and climate are the dominant factors that significantly impact the hydrological process. However, the impact on flood response behaviour varies spatiotemporally. This study quantitatively assessed the effects of individual and coupled changes in land cover and climate on peak and high flows in the upstream and downstream parts of the Upper Awash River basin. Two time periods were chosen for comparison: baseline (1988–2001) and evaluation (2002–2015). The Soil Water and Assessment Tool (SWAT) was used to estimate the impact of these changes. The model satisfactorily simulated daily and extreme flows. The evaluation of annual maximal discharge variability between 1985 and 2015 at upstream and downstream stations showed significant positive and insignificant negative trends, respectively. However, the sub-basin’s annual wet day rainfall (PRCPTOT) showed a downward trend. The annual maximal discharge–PRCPTOT relationship was significant during the baseline but later had no significance. The SWAT model showed that the main factor that affected the changes in upstream flow was the land cover change, increasing peak and high flow by 38.69% and 11.95%, respectively, compared to the baseline period. However, combined changes resulted in downstream peak and high flow reductions of 19.55% and 50.33%, respectively. As a result, changes in flood characteristics are strong functions of land cover, especially in the upstream sub-basin and land cover and climate in the downstream sub-basin. Overall, the impact of changes in the cropland-dominated basin was noticeably different. The study assists water resource managers in understanding the causes of hydrological dynamics and developing mitigation strategies. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.Item Extreme hydroclimatic variability and impact of local and global climate system anomalies on extreme flow in the Upper Awash River basin(Springer, 2023) Tola, S.Y.; Shetty, A.Extreme hydroclimatic variability in a changing climate and the possible causes of extreme hydrological variability are essential for effectively mitigating floods. The study aims to investigate the variability of extreme hydroclimatic conditions and the relationship between anomalies in extreme local precipitation, ENSO indicators (Southern Oscillation index (SOI), Niño 3.4, and multivariate ENSO index (MEI)), and extreme flow indices in the Upper Awash River basin, Ethiopia. The analysis used standardized anomaly index and coefficient of variation statistics to examine variability, the modified Mann-Kendall and Pettitt tests for trend and change point analysis, and Spearman’s correlation test to explore relationships. The study revealed that the basin-wise extreme precipitation indices had less variability but higher variability spatially, while the extreme flow indices showed high variability. Furthermore, the basin experienced extreme wet to normal wet conditions in the 1990s compared to the 2000s. The maximum temperature increased significantly, while the minimum temperature decreased significantly (except at a few northwest stations), with a considerable shift in the 1990s and 2000s. Anomalies, extreme to normal wet conditions, and a decrease in extreme precipitation were consistent with the extreme flow at the basin outlet, Hombole station. However, the extreme flow indices at Melka Kunture increased significantly and shifted upward (2003/2005), and the anomalies in extremely wet and very wet precipitation in the northwest were possibly responsible for this change. The study also revealed that the annual wet and very wet days of precipitation strongly affected the extreme flow in the basin. The effect of annual wet day precipitation, annual maximum precipitation, and ENSO anomalies on extreme flow at the Hombole was significant. These findings enhance the understanding of extreme hydroclimatic variability and prospective flood predictability and aid flood risk management. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.Item Flood hazard map of the Becho floodplain, Ethiopia, using nonstationary frequency model(Springer Science and Business Media Deutschland GmbH, 2024) Tola, S.Y.; Shetty, A.Flood estimates based on stationary flood frequency models are commonly used as inputs to flood hazard mapping. However, changing flood characteristics caused by climate change necessitate more accurate assessments of the probabilities of rare flood events. This study aims to develop a flood hazard map based on the nonstationary flood frequency using a generalized extreme value distribution model for the Becho floodplain in the upper Awash River basin. The distributional location parameter was modeled as a function of rainfall amount of different durations, annual total precipitation from wet days, yearly mean maximum temperature and time as covariates. The one-dimensional Hydrological Engineering Center River Analysis System (HEC-RAS) hydraulic model with steady flow analysis was used to generate flood hazard map input, depth and velocity, and inundation extent for different return periods. The result indicated that the model as a function of rainfall, such as monthly rainfall (August) and annual wet day precipitation, provided the best fit to the observed hydrological data. Rainfall as a covariate can explain the variation in the peak flood series. The developed hazard map based on depth alone and the combination of depth and velocity thresholds resulted in more than 70% of the floodplain area being classified as a high hazard zone under 2, 25, 50, and 100-years return periods. The current study assists water resource managers in considering changing environmental factors and an alternative flood frequency model for developing flood hazard management and mitigation strategies. © The Author(s) under exclusive licence to Institute of Geophysics, Polish Academy of Sciences & Polish Academy of Sciences 2023.Item Characterization of the Surface Lake and Evaluation of Its Benefits on Unconfined Aquifer Interaction—A Study on Coastal Karnataka Lake, India(Springer Nature, 2024) Shetty, S.T.; Dhumale, S.; Shetty, A.; Tola, S.Y.Groundwater recharge is pivotal in addressing diverse water needs in rural India, like water supply, irrigation, and domestic requirements. A significant amount of recharge happens through lakes. However, minimal research has been conducted to evaluate the status of extinct lakes and their potential contributions to nearby unconfined aquifers. This study aims to bridge this gap by assessing critical aspects of groundwater recharge and investigating the role of an extinct lake in this process. Sixteen strategically positioned monitoring wells facilitated data collection, enabling a comprehensive analysis of the groundwater dynamics. The study revealed a substantial increase in built-up areas from 25.66 to 37.59% between 2004 and 2021. The rainfall-runoff relationship was found to be strong, with runoff levels varying from 703.8 to 3426 mm. Using the Korkmaz method, it was determined that around 48% of precipitation naturally replenishes unconfined aquifers. Soil samples near the monitoring wells have varying hydraulic conductivity values of 77.76 to 570.24 m/day, indicating their suitability for water storage. Lake restoration and bund construction emerge as a transformative intervention, positively influencing consistent water levels in wells, redirecting water flow, and enhancing 16.38% increased crop productivity. This emphasizes the lake’s significance in replenishing nearby wells, establishing its crucial role in groundwater recharge. These insights are vital for informed water resource management, particularly in sustaining the region’s water and agricultural needs. Understanding and harnessing the potential of extinct lakes emerge as imperative measures for ensuring long-term water security in rural India. © The Author(s), under exclusive licence to Springer Nature Singapore Pte Ltd. 2024.