HS2.1.4

The cryosphere is an important component of the Earth’s climate system and is exceptionally sensitive to global warming. Studies have shown the decline in the ice and snow cover with increasing temperatures in the Himalayan Mountainous Region (HMR), the third-largest deposit of ice and snow. The melting of ice and snow contributes to the discharge and affects the availability of water in the downstream areas. The introduction of satellite-based observations in conjunction with land surface modelling is paramount as the scarcity of ground data in the mountainous region limits the study.

The study focuses on the snowmelt contribution of the HMR to the discharge of Ganga Basin. An integrative approach of NASA Land Information System Framework (LISF)-NOAH Land Surface Model and Runoff Routing Model is used to estimate the snowmelt contribution to discharge. The snowmelt contribution has been compared for the period 2008-2018 based on two model runs, i.e., control with experiment run wherein satellite-based snow cover observations (MODIS) has been assimilated in the model based on Direct Assimilation (DA). Assimilation of snow cover data helps to model the snowmelt efficiently as compared to control run which is then used to simulate discharge and snowmelt contribution to discharge.

The simulated DA mode results are more congruous with the station observed data and is helpful in producing a snowmelt baseline for the HMR. The snowmelt baseline can be used for comparing future snowmelt contributions to discharge in the context of environmental change.

How to cite: Maurya, V., Gupta, M., Pant, N. C., and Sahai, A. K.: Assimilation of EO based data into LSM to compute the contribution of snowmelt to discharge in the High Mountainous Region., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-274, https://doi.org/10.5194/egusphere-egu22-274, 2022.

The assessment of soil-water balance is associated with several challenges, such as the mitigation effects of droughts and flooding, particularly under climate change. Such alerting threat has pushed forward the efforts that the governments are doing to mitigate this risk. Aiming at contributing to better characterize the soil-water balance in small agricultural catchments, the European Union has launched a project of OPtimal strategies to retAIN and re-use water and nutrients across different soil-climatic regions in Europe (OPTAIN). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 862756. In the framework of this project, the Soil Water Assessment Tool Plus (SWAT+) model was applied to the Cherio river basin, located near the city of Milan, Northern Italy, to develop novel strategies for natural/small water retention measures (NSWRM). The topography of the basin is complex, in which the northern part of the basin is a mountainous area, while the middle and lower part is mainly covered by urban, forest, and agricultural areas. The digital elevation model, land uses, soils, river network, and a long dataset of observed meteorological variables from 2002 to 2020 were prepared and elaborated to satisfy the model requirements. The application of the SWAT+ model was done by delineating the watershed, mapping land use and soil and their associated parameters, and creating the Hydrologic Response Units (HRUs) that identify hydrological homogenous areas inside the basin. As a result, the SWAT+ was used to simulate the hydrological processes and a sensitivity analysis was performed to identify the sensitive parameters affecting the simulated discharge based on the Sobol method. Model calibration was then performed using the observed discharges recorded at a flow gauge close to the basin outlet. The results show that differences between the simulated and observed discharges are very significant and appear to be related to the insufficient quality of precipitation inputs, rather than to model limitations or poor parameter calibration. This returns to the role of the uncertainty associated with the temporal and spatial measurement of the precipitation even in small catchments when the hydromorphological characteristics are complex. The findings of this research can be used to have a better understanding of hydrological fluxes variability across the basin and to assess the proper NSWRM to improve the qualitative and quantitative management of water resources in the Cherio river basin.

How to cite: Negm, A., Gaini, P., Chiaradia, E. A., and Gandolfi, C.: SWAT+ application to a small catchment for NSWRM assessment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-630, https://doi.org/10.5194/egusphere-egu22-630, 2022.

The variable runoff generation layer concept is proposed based on the new understanding of hillslope hydrological experiments to address the problem of flash flood forecasting in hilly regions. This concept has expanded the depiction of interflow from soil horizon to soil-weathering bedrock interface and provided a unified description of the infiltration excess and the saturation excess runoff and their conversion mechanism by meticulously depicting the formation and development process of interflow. Based on the concept of variable generation layer and the theory of kinematic wave model, the calculation formulas of infiltration excess (Horton), saturation excess (Dunne) surface runoff, and interflow of the unit grid are derived. The nonlinear reservoir method, 2-d diffusion wave equation, and 1-d diffusion wave equation are applied to calculate the groundwater flow, the surface runoff routing, and channel flow routing separately, based on which established the variable runoff generation layer distributed hydrological model (VRGL). The VRGL model is applied to the Tunxi watershed, a typical humid watershed of the hilly region. 24 flood events ranging from 2010 to 2019 were studied, and the results showed that the relative error of the flood peak and the flood volume were both within ±20%, and the Nash-Sutcliffe efficiency (NSE) was around 0.84. It is indicated that the accuracy of the VRGL model is high enough for flash flood forecasting in hilly regions.

How to cite: Zhao, J., Liang, Z., Liu, J., Li, B., and Duan, Y.: Variable Runoff Generation Layer distributed hydrological model of hilly regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1908, https://doi.org/10.5194/egusphere-egu22-1908, 2022.

Roads presence and landslides occurrence in steep slope mountain areas are often strictly connected. In recent decades, the use of Airborne Laser Scanning (ALS)-derived high-resolution topographic data amplified the possibilities to better represent landscapes and related physical processes at the basin scale. Additionally, the adoption of topographically-based hydrological models allows to simulating water overland flows dynamics and investigating the occurrence of specific degradative phenomena. In this regard, snowpack melting plays a key role in altering superficial water dynamics in mountain landscapes, but accurate investigation about the interaction between snowmelt runoff and human infrastructures (such as roads) in the occurrence of hillslope failures is still obscure. This research aims to assess the relationship between snowmelt runoff, road presence and terrain instabilities affecting a landslide-prone steep slope mountain meadow (northern Italy). An innovative multi-modeling approach was tested to detect the alteration of snowmelt overflows due to the road’s presence, as well as to investigate its relationship with the activation of a shallow landslide. The role of the road in altering snowmelt runoff was investigated both considering its presence and assuming its absence by a novel Digital Elevation Model (DEM) editing procedure. Different hydrological and slope stability models were interactively implemented, starting from pre-event ALS-derived DEM to propose predictive basin-scale simulations. Results attested the relevant role played by the road in altering snowmelt runoff overland flows, as well as their combined contribution in the foreseen activation of the observed shallow landslide. Starting from on-field observations conducted after the landslide triggering, the accuracy of instabilities predictions was tested through the computation of the Area Under the Receiver Operating Characteristic curve (AUC-ROC) and the Cohen’s kappa-index. This work could be a useful tool for planning mitigation interventions able to reduce the occurrence of similar risk scenarios, also providing specific suggestions for developing and promoting efficient sustainable actions for mountain landscapes.

How to cite: Mauri, L., Cucchiaro, S., Grigolato, S., Dalla Fontana, G., and Tarolli, P.: Investigating the interaction between snowmelt runoff and road in the activation of hillslope instabilities affecting a landslide-prone mountain basin through a multi-modeling approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4691, https://doi.org/10.5194/egusphere-egu22-4691, 2022.

Anthropogenic activities such as dam regulation have altered the streamflow and sediment relationships in the Himalayan River basins. The effect of dams and barrage operations on streamflow and suspended sediment has been widely studied, but the impact of dam construction in this context is poorly understood. The goal of the study is to create a conceptual framework to explore the shifts in streamflow-sediment interdependence across the continuum of natural-to-post dam construction periods in the Eastern Himalayan Tista River basin. Previous studies have either used sediment rating curve (SRC) or hysteresis, but we have employed both to answer whether these two methods are independently diagnostic of changing streamflow and sediment relations in different stages of dam development in the basin? The Tista basin will have the highest density of dams globally if all the proposed 29 dams are commissioned in the future. Currently, a total of 13 major dams for hydropower (>25 MW) in the mountain basin and a diversion barrage in the alluvial plain for irrigation are functional. Cumulatively, the reservoir of these dams and barrage can store ~89 million m³ of water. The interannual and inter-seasonal streamflow and suspended sediment data from the gauge station located at the alluvial plain downstream of all the 14 regulation structures were analysed for the pre-dam, dam-construction, and post-dam periods. We observed that the annual streamflow is predominantly determined by the heavy monsoon rainfall-runoff in the basin that reduced to 28% during the post-dam condition. The same in the non-monsoon post-dam condition was reduced by 58% mainly due to regulation to satisfy the sectoral demand for water. The mean annual sediment was recorded ~11 Mt, ~46 Mt and ~14 Mt during the pre-dam, dam construction and post-dam period, respectively, while the reservoir trapping reduced 56% of sediment during the non-monsoon post-dam period. The SRC exhibited that erosive behaviour (b-value) of the river increased due to massive streamflow during the monsoon season but fairly increased during annual post-dam condition suggesting the role of dam released sediment starved streamflow to erode. High a-value and clockwise hysteresis demonstrated the sediment-surplus condition due to dam construction activities, which altered the mountain landscape through deforestation and excavation of mountain slope, resulting in further erosion and sedimentation. The post-dam high a-value indicates that reservoirs released sediment downstream by drawdown-flushing with reduced streamflow which develops a complex single-valued hysteresis, implying controlled discharge and carrying capacity. Consequently, due to regulation, the uneven sediment distribution across the river continuum has increased flood vulnerability and riverbank erosion, constraining the ecosystem services. The findings of the study will be beneficial for policies on future water-sharing and management of sediment and flood by the river managers and hydropower companies.

How to cite: Ghosh, K. and Munoz-Arriola, F.: Streamflow-sediment relations across the continuum of natural-to-post dam construction periods in the Himalayan river basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6129, https://doi.org/10.5194/egusphere-egu22-6129, 2022.

Climate change leads to the degradation of mountain glaciers in Central Asia and subsequent formation of glacial lakes [Harrison et al., 2018]. Due to the fact that glacial lakes are located, as a rule, in hard-to-reach areas, where there are no systematic observations, it is rather difficult to predict outbursts. One of the ways to assess the risks associated with glacial lakes outburst (GLOF) is mathematical modeling. We used a complex of three models to estimate possible hazard in the downstream valleys. A lake outburst hydrograph was obtained with a model developed by Yu.B. Vinogradov [Vinodradov,1977], based on the emergence and expansion of the intraglacial channel. For the debris flow source, we applied an upgraded transport-shift model, the equations were obtained using the data of the Chemolgan experiment [Vinogradova, Vinogradov, 2017].  A two-dimensional model called FLO-2D was used to investigate quantitative characteristics of the debris flow in the river valley [O'Brien et al., 1993]. The prerequisites and modeling of possible glacier lake outburst were considered for the Bodomdara River valley (Tajikistan) using detailed field data. According to the route survey results, it was established that Lake Bodomdara Upper is a glacial one, which, in turn, may lead to a cascade outburst flood. The bowl of Lake Bodomdara Lower is relatively stable, its outburst is possible without cascade flooding at anomalously high temperatures, snowmelt combined with extreme rainfall. Two probable scenarios were considered: I - the outburst of the Lake Bodomdara Lower (the volume was 328 thousand m³ according to the bathymetric survey results) and II - the cascade outburst of the Lakes Bodomdara (with the volume of 700 thousand m³). A digital elevation model (DEM) ALOS PALSAR (12.5 m) was used as relief data, and for the Bodomdara river cone - DEM based on images from an unmanned aerial vehicle. The outburst flood hydrograph for the scenario I was obtained using the lake breakthrough model developed by Yu.B. Vinogradov, and for II - using an empirical formula. The material increment was estimated in the transport-shift model of debris flow formation. The resulting hydrograph was used for zoning the Bodomdara and Shahdara valleys with a total length of 75 km based on the FLO-2D model. According to the modelling results at the top of the estuary cone of the Bodomdara river discharge under scenario I, the maximum flow will be 111 m³/s, under scenario II - 525 m³/s.

1. Harrison S., Kargel J. S., Huggel C. et al. Climate change and the global pattern of moraine-dammed glacial lake outburst floods // The Cryosphere, 2018, vol. XII, 4, p. 1195–1209.

2. O'Brien J., Julien P., Fullerton W. Two-dimensional water flood, mudflow simulation // Journal of Hydraulic Engineering, ASCE, 1993, vol. CXIX, No 2, p. 244–259.

3. Vinogradova T.A., Vinogradov A.Yu. The experimental debris flows in the Chemolgan River basin // Natural Hazards, 2017, vol. LXXXVIII, 1, p. 189–198.

4. Vinogradov Yu.B. Glacial outburst floods and mudflows. Leningrad, Publishing House “Gidrometeoizdat”, 1977, 154 p.

How to cite: Yudina (Kurovskaia), V., Chernomorets, S., Krylenko, I., Vinogradova, T., Savernyuk, E., Gulomaydarov, A., Zikillobekov, I., Pirmamadov, U., and Raimbekov, Y.: Modeling of glacial lake outburst in the Shakhdara river basin using the complex of mathematical models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6228, https://doi.org/10.5194/egusphere-egu22-6228, 2022.

In the recent scenario of global warming, the release of organic and inorganic carbon from the melting glaciers has been a subject of scientific research since it can have a pronounced effect on the riverine carbon cycle and primary productivity. Apart from being one of the largest Himalayan glaciers, Gangotri glacier provides water to the Bhagirathi River (Ganga River) which is the most important perennial river in India in terms of economy and livelihood. In the last decade, the melting and recession of Gangotri glacier have increased significantly leading to the formation of glacial lakes and debris-covered areas. As a result, primary productivity and microbial activity have increased in the subglacial areas which release a great amount of soil CO₂ that has not been documented previously in the literature. In the present study, the Bhagirathi River, which is the proglacial melt-stream of the Gangotri glacier has been sampled during the Post-monsoon period. A total of 27 samples including river, groundwater, geothermal spring, and reservoir were collected and have been analyzed for pH, surface temperature, Electrical conductivity (EC), major ions, and stable isotopes of carbon. From the study of major ion abundance patterns and mixing ratios, it has been inferred that carbonate weathering is predominant in the basin, though the major rock type of the area are silicates. The (HCO₃^- ≈ Dissolved Inorganic Carbon, DIC) values of river water show no correlation with altitude (mean = 42.8 mg/L), while δ¹³C values show a decreasing trend with a decrease in altitude, with an overall range between -10 and - 5‰. As altitude decreases, organic matter activity increases, and thus more CO₂ is washed out from the Soil Organic Matter (SOM), which makes the δ¹³C values of the river depleted. The δ¹³C of groundwater (mean = -11.8‰) and reservoir water (mean = -9.4‰) are depleted than river water due to mixing of soil carbon in them, and δ¹³C of geothermal spring water (mean = -3.6‰), shows enriched values since these are places of active CO₂ degassing. The source of DIC in the river water is mainly carbonate weathering in the upstream part and soil CO₂ in the downstream part of the study area. Quantifying pCO₂ values of the river water and calculating carbon flux from the river would provide important information on whether the Bhagirathi River is acting as a carbon source or sink to the atmosphere.

How to cite: Chatterjee, N., Tiwari, S. K., Gupta, A. K., and Sharma, K.: Isotopic and geochemical studies in the Upper Ganga Basin, Uttarakhand, India: Implications on Dissolved Inorganic Carbon systematics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8389, https://doi.org/10.5194/egusphere-egu22-8389, 2022.

With their complex topography and orographic effects, the amount of solar radiation reaching a surface (insolation) can vary over short distances and time frames in mountainous areas, affecting the spatio-temporal variability of hydrological and ecological processes and contributing to the biodiversity of mountain ecosystems.  The combined effects of variable topography and meteorological conditions on insolation can complicate assessments of how land cover changes affect insolation in mountainous regions as measurement data is often limited to few locations. To incorporate the spatio-temporal variability of sky conditions as well as the spatial variability of terrain in estimates of solar radiation across a montane headwater basin over two summers, we extended an open-source geospatial model of surface solar radiation, r.sun.hourly, to permit the spatially and temporally explicit parameterization of atmospheric conditions at user-specified spatial and temporal resolutions with temporal raster datasets.  Sensitivity analyses indicated that of the three atmospheric parameters in the model, the coefficient of real-sky direct beam solar radiation (coeff_bh) (an index of cloudiness to clear sky conditions) had the greatest influence on insolation estimates for our study area, located in the southern Appalachian Mountains of the southeastern USA, and we developed a workflow for estimating coeff_bh from publicly available geostationary meteorological satellite images (GOES-13, 1 km spatial and 15-minute temporal resolutions).  The extended r.sun.hourly model was parameterized with a bare-earth digital elevation model (1/9 arc-second DEM obtained from the USGS National Map 3-D Elevation Program), the estimated coeff_bh temporal raster datasets (downscaled from 1 km to the DEM resolution), and monthly mean Linke Turbidity values to estimate global solar radiation across the basin at a 15-minute resolution over two summers.  Estimates of instantaneous (15-minute interval) and cumulative total (for 12-hour period bracketing solar noon) global solar radiation were evaluated with pyranometer (Eppley 8-48) measurements of global solar radiation collected by the U.S. Department of Agriculture Forest Service Coweeta Hydrological Laboratory for a total of 144 days (dates with recorded precipitation during daylight hours or incomplete imagery datasets were excluded from analyses).   Despite the low spatial resolution of the satellite images from which the real-sky direct beam radiation coefficient was estimated and the proximity of the ground measurement location to the edges of a GOES-13 cell (< 90 m north and < 230 m east), both instantaneous and daily total estimates of global solar radiation corresponded well with measurements (R² = 0.81, p-value < 0.001, n = 7056 and R² = 0.89, p-value < 0.001, n = 144). Estimate errors tended to be lower on cloudier days (MAPE = 6.8%, n = 61) than less cloudy days (MAPE = 13.6%, n = 83).  Offsets in the timing and magnitude of peaks and troughs in insolation over time (with passing clouds) between measurements and estimates were also greater during partly cloudy conditions.  Although these findings are for one location, they suggest the potential of the extended r.sun.hourly model to provide high-resolution estimates of solar radiation, over extensive areas and timeframes, in mountainous regions with remotely sensed elevation and meteorological data.

How to cite: Belica, L., Castro Garrido, M., Petrasova, A., and Nelson, S.: Exploring a method to estimate real-sky global solar radiation in mountainous areas at high resolutions with an open-source geospatial solar radiation model and GOES-13 geostationary meteorological satellite data., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12493, https://doi.org/10.5194/egusphere-egu22-12493, 2022.

Water resources in the Himalayan region are highly exposed and vulnerable to climate variability and climate change. We investigate the potential impact of climate change on hydroclimatic extremes and spatiotemporal distribution of water balance components of the Himalayan river basin, taking the Tila River Basin of Nepal as a test site. This study integrates CMIP6 climate model outputs with a semi-distributed hydrologic model to produce streamflow projections. We analyze climate change impact in three timeframes: near (2026-2050), mid (2051-2075), and far (2076-2100) future under SSP 245 and SSP 585 scenarios. Results showed that the projected change in precipitation, evapotranspiration, and water yield is as high as 50%, 45%, and 75%, respectively. Both low and high flows are projected to increase under future climate scenarios. High altitude regions, with dominant snow- and glacier-covered areas, are more vulnerable to climate change impact. Our results are of practical importance for planners and decision-makers to formulate adaptation strategies under a changing climate.

How to cite: Baniya, R., Regmi, R. K., Talchabhadel, R., Sharma, S., Panthi, J., Ghimire, G. R., Bista, S., and Thapa, B. R.: Hydrologic response to climate change: A case from a high-mountain river basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-503, https://doi.org/10.5194/egusphere-egu22-503, 2022.

The study investigates the interactions between surface water and meteo-climate processes in an Alpine valley (Grosina, northern Italy) characterized by anthropogenic modifications affecting the hydrologic cycle. Grosina valley, an accessory valley of Valtellina on the border between Italy and Switzerland, features a central-alpine climatic type. The valley is composed of two main branches - Eita (62 km²) and Sacco (71 km²). Along the Eita stream, close to its confluence with the Sacco stream, a dam was built in 1960 for hydro-power exploitation and regulation purposes. After the confluence, the river takes the name of Roasco. Anthropogenic modifications of the natural water system include two diversion channels in the main branches that connect them to the dam and a third diversion tunnel that brings a high volume of water into the dam lake from a hydroelectric plant located outside the watershed.

The study general aim is two-fold: i) setting up a prototypal operational hydrologic model (forecast period of about one week) for water use management and ii) applying a hydrologic model for estimating impacts of climatic changes on water resources and the hydrologic cycle in the medium/long-term (decadal and multi-decadal analyses). The first step of this project is common to the two aims and involves the definition of the conceptual model and the implementation-calibration of a hydrologic model in such a challenging environment, representative of the multiple and concurrent uses of water resources in mountain areas.

The modeling of the Grosina valley catchment has been carried out exploiting the potentialities of the GEOframe system, an open-source, semi-distributed hydrologic model. It is a component-based model since it is developed starting from the creation of single modules (components) that describe the principal physical processes of the hydrologic cycle. After identifying Hydrological Response Units (HRUs) and their connections through a geomorphological analysis, contributions and losses to the system were considered by exploiting the components of meteorological data interpolation (from 22 stations), radiation calculation, partitioning between solid and liquid precipitation, and evapotranspiration. Then, the calibration of the model was performed by comparing the simulated flow to discharge data recorder at the diversion points, the dam, and a hydrometer placed at the end of the valley (hourly timestep). This phase proved to be very complex and demanding since only the measure of the derived flow, namely the flow captured for hydropower purposes, was available. Therefore, at the diversion points, it was chosen to estimate the natural flow as the sum of the derived flow and the minimum environmental flow (MEF), focusing the match between observation and simulation on the baseflow behavior rather than the discharge peaks. The calibration phase led to a good correspondence between simulated and observed flow with Nash-Sutcliffe Efficiency values greater than 0.6 at all points investigated.

How to cite: Citrini, A., Camera, C., Marini, L., and Beretta, G. P.: Preliminary results regarding the simulation of a streamflow strongly influenced by anthropogenic use in an alpine context: the case of the Grosina valley (northern Italy)., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1882, https://doi.org/10.5194/egusphere-egu22-1882, 2022.

Ground thermal regime of high mountain catchments impacts the partition between infiltration and runoff, latent and sensible heat fluxes, frozen and liquid subsurface water and the presence (or absence) of permafrost. In the context of global warming, hydrological modifications associated to ground thermal changes are of critical importance for extensive headwater regions such as the Qinghai-Tibet Plateau (QTP) and the Himalayas, which are major water towers of the world. Improving our ability to quantify these changes is therefore a key scientific challenge both regarding basic science and continental-scale water resource management. Many watersheds of the QTP have seen their hydrologic budget modified over the last decades as evidenced by strong lake level variations observed in endorheic basins. Yet, the role of ground thermal changes in these variations has not been assessed.

Lake Paiku (central Himalayas, southern TP) has exhibited important level decreases since the 70s and thus offers the possibility to test the potential role of ground thermal changes and permafrost thaw on these hydrologic changes. We present distributed ground thermo-hydric simulations covering the watershed over the last four decades to discuss their implications on the lake level changes. We use the Cryogrid model to simulate the surface energy balance, snow pack dynamics and the ground thermo-hydric regime while accounting for the phase changes and the soil water budget. Because the surface radiative, sensible and latent heat fluxes in alpine environments are strongly dependent on the physiography, the model is forced with distributed downscaled forcing data produced with the TOPOSCALE model to account for this spatial variability. Simulated surface conditions are evaluated against meteorological data acquired within the basin, ground surface temperature loggers and remotely sensed surface temperatures. The simulations show that, contrary to large scale estimates of permafrost occurrence probability, an significant part of the basin is underlaid by permafrost (>20%). We also show that over the 1980-2020 period, ground temperature warmed up by 1.5 to 2°C per centuries. The permafrost limit rose from 5100 to 5300 m asl (in 40 years). Unfrozen surface conditions increased by around 25 days per century and evaporation increasing by +22% over the period. To represent the impact of these changes on the lake level, we included them in a simple hydrological budget calculation including the contribution of glacier melt and lake evaporation. This approach shows that ground thermo-hydric changes in the catchment have significantly contributed to the lake level changes. These first results highlight the potential of thermo-hydric simulation to better quantify hydrological changes to come in the QTP.

How to cite: Martin, L., Westermann, S., Magni, M., Brun, F., Fiddes, J., Lei, Y., Kraaijenbrink, P., Mathys, T., and Immerzeel, W.: Impact of recent ground thermal changes on the hydrology of a Tibetan catchment and implications for lake level changes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5028, https://doi.org/10.5194/egusphere-egu22-5028, 2022.

Climate change is considered as the important factor for change in water balancing components (WBCs) at the river basin scale. In this study, the Soil and Water Assessment Tool (SWAT) hydrological model is used for the assessment of WBCs for the Kalada river basin (KRB) in the Western Ghats, India. To assess the climate change impacts of near (2021 – 2040), mid (2041 – 2060), and far (2081 – 2100) future for moderate scenarios under representative concentration pathways (RCP) 4.5 and worse scenarios (RCP 8.5) were considered by using the present (2018) fixed land use. The multi-optimization techniques have been used for model calibration and verification of climatic data of the five General Circulation Models in the study area. The results indicated that the actual evapotranspiration (ET), surface runoff, and water yield are decreased (16 to 27%) in all-time slices for both RCP 4.5 and 8.5 emission scenarios but the decreasing trend is non-uniform. This is because of the decline of rainfall by 50 to 230 mm and the increase of temperature by 2 to 5 ℃ in the study area. Furthermore, results indicated that the wet season showed less decrease in comparison to winter and summer, but impacts are high because more than 80% of rain occurred in the monsoon season.

Keywords: Water Balancing Components; Climate change; Surface runoff; GCMs; SWAT model.

How to cite: Sinha, R. K., Sharma, S. K., and T.I., E.: Climate change impacts on water balancing components for a tropical river basin, Western Ghats India., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6905, https://doi.org/10.5194/egusphere-egu22-6905, 2022.

The climate change has a significant contribution in the uncertainty in the river flow. In this study, the uncertainty in the river flow of Pamba River Basin (PRB) in South India is investigated due to climate change impacts. In order to assess the hydrological impact in the basin for future preparedness and planning for sustainable use of water resources, an ensemble of five general circulation models (GCMs) and hydrological model SWAT (soil and Water Assessment Tool) were used. The objective of the present study was to understand the surface runoff change over the PRB in the near future (2016-2030) under representative concentration pathways (RCP) 4.5 and 8.5 of the downscaled ensemble GCM data. Furthermore, spatial runoff change at sub-basin scale and percentage runoff change at monthly scale in the PRB were assessed. Hence, to study the impact due to climate change, SWAT model was simulated with base period historical data (1984 – 2015) and future climate data (2016 – 2030), and then changes at spatial and monthly scale were plotted. The results shows that at basin scale, there is an overall increase in the mean runoff by the 1.4 % and 3.0% under RCP4.5 and RCP 8.5 scenarios respectively. At seasonal scale, winter shows a tremendous increase in the runoff with around 38% increase in both RCP 4.5 and RCP 8.5, followed by summer with 17.9% and 18.6% for RCP 4.5 and RCP 8.5 scenarios respectively. Notably, Monsoon witnesses a negative trend in both the scenarios with -18.6% and -15.5% runoff change from the base period. This study will be useful in future water resources management in the basin at micro-level due the spatial and temporal variations.

Keywords: Climate change; SWAT model; GCMs; runoff change; spatial, and temporal change.

How to cite: Sharma, S. K., Sinha, R. K., and T. I., E.: Hydrological Impact Assessment of Climate Change on a Tropical River Basin in Southern India, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7263, https://doi.org/10.5194/egusphere-egu22-7263, 2022.

Operational water-resource planning faces an increased challenge with a changing seasonal snowpack in mountain watersheds due to global and regional climatological factors. An example region is the Western United States, where there is a demonstrated decline in extent and amount of seasonal snow in mountain ranges such as the Sierra Nevada, California, or the Rocky Mountains, Colorado. Causes for the shift include precipitation phase changes or increased amounts of dust on snow. Like the Colorado Basin River Forecast Center (CBRFC), regional forecasters cannot currently account for these factors when their prediction method relies on an empirical snow model based on historic calibration records. To evaluate the options and supplement the current method of the CBRFC, we run a physical-based snow energy balance model for past water years in a subset region; the East River Watershed, Colorado. The results are compared with in-situ measurements, remote sensing observations, and the predictions by the current model. This assessment is an effort to include the process based model in day-to-day CBRFC operations and to create a foundation to expand to larger domains. This project also bridges the gap between scientific advancements and benefits for society with more accurate water resource forecasting.

How to cite: Meyer, J., Skiles, M., Kormos, P., Hedrick, A., Trujillo, E., Havens, S., and Marks, D.: Operational water forecast assessment of a spatially distributed process-based snow model; a case study in the East River Watershed, Colorado, USA, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10454, https://doi.org/10.5194/egusphere-egu22-10454, 2022.