DSpace Community:

Seasonal fluctuation of spring outflows in contrasting lithological and geomorphological environments of the western mid-hill region, Nepal

2026-01-01T00:00:00Z

Title: Seasonal fluctuation of spring outflows in contrasting lithological and geomorphological environments of the western mid-hill region, Nepal Authors: Pokhrel, Gunanidhi; Rijal, Moti Lal; Krishan, Gopal Abstract: Springs are vital water sources in the mid-hill region of Nepal, yet understanding of their seasonal outflow variability and the hydrogeological controls remain limited. This study analyzed 175 perennial springs in the western mid-hill region of Nepal, with seasonal outflow (discharge) measurements conducted during the post-monsoon high-flow periods in 2022 (Q1) and 2023 (Q2), and the pre-monsoon low-flow period in 2024 (Q3). Spring outflow was measured using volumetric gauging and weir methods depending on outflow conditions. Mean outflow declined from 36.44 lpm in Q1 to 31.97 lpm in Q2 and 15.66 lpm in Q3, indicating strong dry-season recession. The Friedman test confirmed significant seasonal variation among Q1, Q2, and Q3 (χ2=298.16, p<0.001), while Wilcoxon signed-rank tests showed significant differences between all seasonal pairs. The Q1–Q2 decline was partly linked to interannual rainfall variability, as monsoon rainfall decreased by 27.4% from 2022 to 2023. During Q3, nearly two-thirds of springs shifted into the minimal discharge class (≤10 lpm). Carbonate-dominant regions showed higher and more variable outflows, reflecting fractured/karstic aquifer storage. These findings support priority-based springs conservation and recharge enhancement for dry-season water security. The study emphasizes the need to distinguish seasonal spring recession from long-term groundwater depletion through sustained monitoring.

An isotopic approach to address the groundwater evolution and process in the Indus basin, NW India

2027-01-01T00:00:00Z

Title: An isotopic approach to address the groundwater evolution and process in the Indus basin, NW India Authors: Krishan, Gopal; Pandey, Amit; Khobragade, S.D.; Vashisht, Rajesh Abstract: Groundwater recharge processes and connectivity between aquifers strongly influence the sustainability of groundwater use. In many intensively exploited alluvial systems, especially in semi-arid regions with intensive agriculture and multi-aquifer settings, both processes remain poorly understood. To address this gap, this study examines the spatial and temporal variations in groundwater isotopic composition (δ18O and δD) across shallow, intermediate, and deep aquifers in Punjab, India, a part of the Indus Basin, with the aim of identifying recharge sources, assessing evaporative influences, and understanding connectivity between the aquifers. In this regard, groundwater samples were collected during pre-monsoon, monsoon, and post-monsoon seasons and analysed for stable isotopes of oxygen and hydrogen. The δD-δ18O slopes for shallow (5.94) and intermediate depth aquifers (6.18) are observed to be lower than the Global (8) and Local Meteoric Water Lines (7.99), reflecting significant evaporative enrichment. The deep aquifers show relatively higher slopes during the pre- and post-monsoon seasons (>6.7), suggesting comparatively pristine water with limited evaporative modification. High d-excess values (>10‰) were observed in 9-22% of the samples, suggesting a contribution from glacialfed river and canal water. This contribution appears to be more pronounced in areas with intensive canal irrigation. Intermediate aquifers exhibit buffered seasonal isotopic variability; however, the close similarity in isotopic signatures between intermediate and shallow aquifers in certain regions suggests possible vertical leakage and hydraulic interaction between the two aquifer systems. Seasonal analysis of Δδ18O and Δd-excess reveals that most of the groundwater responds to rainfall infiltration and evaporation-driven enrichment, with canal-fed recharge dominating in areas adjacent to canal networks. This study provides an integrated isotopic perspective on recharge dynamics and inter-aquifer interactions in Punjab and emphasising the need for depthspecific groundwater management and protective measures to limit vertical connectivity and contamination risks. The findings have direct implications for sustainable groundwater use and policy interventions in agriculturally intensive regions of the Indus Basin.

Glacial lake expansion and GLOF hazard assessment of Kedartal, upper Ganga basin: insights from remote sensing, climatological and 2D hydro-dynamic modelling

2026-01-01T00:00:00Z

Title: Glacial lake expansion and GLOF hazard assessment of Kedartal, upper Ganga basin: insights from remote sensing, climatological and 2D hydro-dynamic modelling Authors: Patel, Lavkush Kumar; Yadav, Shiv Shankar; Padhi, Aadarsh; Thapliyal, Madhusudan; Singh, Surjeet Abstract: The Hindu Kush Himalaya (HKH) is among the world’s most vulnerable mountain regions, where accelerated glacier retreat has driven the expansion of glacial lakes and increased the potential for Glacial Lake Outburst Floods (GLOFs). This study assesses the potential GLOF hazard associated with Kedartal Lake, a lateral moraine- dammed glacial lake in the Upper Ganga Basin, by integrating climatic trend analysis with process-based hydrodynamic model ling. Multi-temporal satellite observations (2001–2025) with historical mapping, were used to quantify lake evolution. While two- dimensional hydrodynamic model (HEC-RAS) simulated down stream flood propagation under a worst-case dam breach scenario. Results revealed a seasonal expansion of lake area from 64455:86m (1990) to 105772:99m2 (2020), and 1; 33; 823:1m (2025), representing ~64.1% seasonal variation since 1990. The GLOF simulation results showed a high magnitude flood wave with the peak dis charge ~2;800m3 3=s within 15 minutes after initiation at the outlet. The flood wave attenuates as it travels down the Kedar-Ganga valley, reaching Gangotri town with a peak discharge of ~1;450m =s almost 45 minutes after the breach. Flood routing models indicate flow depths up to 2 metres in narrow gorge sec tions, and inundation depths ranging from 0 to 15 metres in the built-up areas near the confluence. Regional climatic analysis reveals a statistically significant warming trend (~0.013 °C yr; p < 0.001) and increasing extreme precipitation events, reinforcing climatic forcing as a primary driver of glacier mass loss and lake expansion. The projected hazard, consistent with SSP-based climate forecast, indicates a risk to Gangotri town. These findings demonstrate the utility of the proposed framework for identifying essential datasets, analytical methods, and monitoring requirements to support preliminary GLOF hazard assessment and future risk management in the basin.

Ice-flux divergence and strain rates reveal compressive-flow hotspots on Gangotri glacier

2026-01-01T00:00:00Z

Title: Ice-flux divergence and strain rates reveal compressive-flow hotspots on Gangotri glacier Authors: Islam, Anikul; Swarnkar, Somil; Varade, Divyesh; Sinha, Rajiv Abstract: Observation of glacier dynamics are critical for assessing hydro-climate processes in the high altitude regions of the world. This study investigated critical glacier ice parameters such as the ice flux divergence (IFD), surface mass balance (SMB) and the spatial pattern of ice surface deformation through logarithmic strain rate of the Gangotri glacier in the upper Bhagirathi basin using fully distributed models based purely on remote sensing data. The primary input for the investigations are based on the ice-thickness change rate, glacier velocity and the digital elevation model (DEM). The SMB referred to as the sum of the vertical and lateral changes of the glacier was observed to be 0.97 m of ice equivalent(m i.e.) yr 1 , indicating significance mass loss over the study period. The results derive several alignments with other published studies, and reveal key insights on the internal glacier processes through critical parameters such as highly variable longitudinal and shear strain rate indicated by standard deviations exceeding 0.025 yr 1 and 0.013 yr 1 , respectively. These highly variable and negative strain rates indicate significant compressive deformation of the glacier in certain regions of the ablation zone, resulting in ice cliffs and large crevasses that were observed in other studies.