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HS2.1.4

EDI
Mountain hydrology under global change: monitoring, modelling and adaptation

Despite only representing about 25% of continental land, mountains are an essential part of the global ecosystem and are recognised to be the source of much of the world’s surfaces water supply apart from important sources of other commodities like energy, minerals, forest and agricultural products, and recreation areas. In addition, mountains represent a storehouse for biodiversity and ecosystem services. People residing within mountains or in their foothills represent approximately 26% of the world’s population, and this percentage increases to nearly 40% when considering those who live within watersheds of rivers originated in a mountain range. This makes mountains particularly sensitive to climate variability, but also unique areas for identifying and monitoring the effects of global change thanks to the rapid dynamics of their physical and biological systems.
This session aims to bring together the scientific community doing hydrology research on mountain ranges across the globe to share results and experiences. Therefore, this session invites contributions addressing past, present and future changes in mountain hydrology due to changes in either climate and/or land use, how these changes affect local and downstream territories, and adaptation strategies to ensure the long-term sustainability of mountain ecosystem services, with a special focus on water cycle regulation and water resources generation. Example topics of interest for this session are:
• Sources of information for evaluating past and present conditions (in either surface and/or ground water systems).
• Methods for differentiating climatic and anthropogenic drivers of hydrological change.
• Modelling approaches to assess hydrological change.
• Evolution, forecasting and impacts of extreme events.
• Case studies on adaptation to changing water resources availability.

Convener: David Haro Monteagudo | Co-conveners: Andrea MomblanchECSECS, Marit Van TielECSECS, Santiago Beguería
Presentations
| Thu, 26 May, 08:30–11:43 (CEST)
 
Room B

Thu, 26 May, 08:30–10:00

Chairpersons: David Haro Monteagudo, Marit Van Tiel, Andrea Momblanch

08:30–08:35
Welcome and introduction

08:35–08:41
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EGU22-274
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ECS
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Virtual presentation
Vikrant Maurya et al.

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.

08:41–08:47
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EGU22-630
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ECS
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Virtual presentation
Amro Negm et al.

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.

08:47–08:53
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EGU22-1908
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ECS
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Virtual presentation
JianFei Zhao et al.

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.

08:53–08:59
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EGU22-4691
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ECS
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On-site presentation
Luca Mauri et al.

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.

08:59–09:05
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EGU22-6129
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ECS
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Virtual presentation
Kausik Ghosh and Francisco Munoz-Arriola

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.

09:05–09:11
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EGU22-6228
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ECS
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Virtual presentation
Viktoriia Yudina (Kurovskaia) et al.

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.

09:11–09:17
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EGU22-6695
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Virtual presentation
Fabian Drenkhan et al.

Tropical high-Andean wetlands, locally called bofedales, represent key ecosystems sustaining biodiversity, carbon sequestration, human water provision and fodder production for livestock farming. They are highly sensitive to climatic and anthropogenic disturbances, such as changes in precipitation patterns, glacier retreat and peat extraction, and are thus of major concern for watershed management. However, the eco-hydrological dynamics and responses of bofedales to impacts from global change are little explored.

In this study we map seasonal bofedales extent in the glaciated Vilcanota-Urubamba basin (Southern Peru) at unprecedented spatial resolution in the region. Therefore, we developed a supervised classification based on the Machine Learning algorithm Random Forest. As a baseline, Sentinel-2 MSI Surface Reflectance imagery between 2020 and 2021 and NASADEM elevation data were included. A total of 27 vegetation and topographic indices were computed and iteratively selected with cross-validated feature selection. As a result, the Wide Dynamic Range Vegetation Index, Normalised Difference Infrared Index and Compound Topographic Index adopt a major role for successful wetland extent classification. We identify a total wetland area of 282 km² (630 km²) at the end of the dry (wet) season in 2020 (2021). The observed high seasonal variability in bofedales extent within the study region suggests the presence of a pronounced intra-annual hydrological regime of drying, soaking and wetting.

For a more thorough assessment of the suggested pattern, we combined borehole water level and outlet river stage data from an arduino sensor network covering five bofedales sites in two micro-watersheds. These confirmed distinct wetting and drying regimes with all levels reducing and increasing during the dry and wet season, respectively, indicating a strong relationship between wetland area extent and water table levels. Based on these findings and a scoping review, a conceptual hydrological model has been proposed. As an initial attempt for model parameterisation, we undertook a statistical analysis, cross-correlating borehole levels, river stage and precipitation inputs to identify lag-times related to the intra-annual storage dynamics of the bofedales. A 4-hour lag-time was observed for outlet river stage to precipitation. However, results for water table response to precipitation were varied, with lag-times from 1 to 46 days, likely owing to the complex topography and hydrological processes within these ecosystems.

Our combined study of supervised wetland classification and eco-hydrological in-situ analysis provides first insights to understanding of high-Andean wetland dynamics. The proposed conceptual model offers a framework to further assess the capacity and residence times of bofedales that can support local decision-making. In view of severe impacts from climate and land use changes, locally tailored conservation and adaptation practices are urgently needed including innovative water storage enhancement interventions. These can be combined with traditional bofedales management by local, native livestock herders. In this regard, nature-based solutions, such as headwater and wetland protection and the implementation of additional water storage, can provide a cost-effective and flexible solution. These interventions leverage natural processes that sustain ecosystem services and increase the buffer function of bofedales to water loss from e.g. glacier shrinkage in headwaters and increasing water demand further downstream.

How to cite: Drenkhan, F., Martínez Mendoza, M., Ross, A., Montoya, N., Baiker, J. R., and Buytaert, W.: Seasonal water storage dynamics of tropical high-Andean wetlands in Peru, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6695, https://doi.org/10.5194/egusphere-egu22-6695, 2022.

09:17–09:23
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EGU22-7051
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On-site presentation
Clément Roques et al.

We investigate spatial and temporal behaviors of spring discharge, transit times and intermittency of a network of springs located in an alpine catchment (Natural conservation area of the Massif of Saint-Barthélemy, Pyrenees, France). Field observations have revealed unprecedented variability of behaviors across the catchment, with springs involving sustained high discharge rates during baseflow while others showing intermittency of wetting and drying periods. This dynamic is expected to be directly dependent on the volume and transmissivity of the connected aquifer set by specific geomorphological (topography scaling, rockslides, deep seated landslides, detritic sediments) and geological features (lithology, faults).  Here we aim at understanding the relative controls of those factors in controlling the observed hydrogeological behaviors across the catchment.

We performed two field missions during 2021 high and low flow regimes. More than 20 flowing springs and wetlands have been systematically mapped and sampled for environmental tracer analysis. We found that about 30% of the stream and wetland network contract between high and low flows. The springs responsible for this intermittence are connected to high transmissive shallow aquifers with low storage capacities organized within shallow soils and rockslides. However, perennial springs are influenced by deep groundwater flow paths within the bedrock. The analysis of anthropogenic dissolved gases like CFCs and SF6 revealed an average transit time of the order of 10 years for perennial springs with important variabilities across the catchment. The relatively high residence times is also confirmed by high Helium concentrations. We used the gathered dataset to calibrate a hydrogeological model designed to test the relative controls from specific geomorphological and geological characteristics. By comparing models with different structural settings, we found that topography and aquifer compartmentalization, through the decreasing trend in hydraulic conductivities, are key parameters in setting the spatio-temporal pattern of saturated areas and the distribution of transit times across the catchment. In perspective, we discuss the potential evolution of the extent, discharge magnitude and the transit time of seeping groundwater under changing recharge scenarios.  

How to cite: Roques, C., Chatton, E., Chrétien, G., Servière, L., Pasquier, X., Abhervé, R., Gauvain, A., Aquilina, L., and de Dreuzy, J.-R.: Spring discharge, transit times and intermittency in an alpine catchment: how geomorphology shapes the spatio-temporal dynamics?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7051, https://doi.org/10.5194/egusphere-egu22-7051, 2022.

09:23–09:29
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EGU22-7320
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ECS
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On-site presentation
Davide Gisolo et al.

Land cover changes affect the local hydrological cycle, including actual evapotranspiration (ETa).  Encroachment by shrubs on abandoned grasslands is an increasing phenomenon in the Alps, a region already suffering climate change effects. In addition, shrub encroachment is thought to occur faster on steep slopes. Unfortunately, steep mountain slopes are rarely studied because of complex morphologies, despite a need for data to better understand these changing ecosystems.

Four growing seasons (two wet – 2014 and 2015 and two dry – 2016 and 2017) of eddy covariance, meteorological, hydrological, and soil data were collected at an abandoned grassland on a slope encroached by shrubs in the Italian Western Alps. The objectives were to: 1) study the ETa differences between two land cover types, grassland and shrubland, based on Hydrus 1D model simulations. 2) Compare the simulated ETa from the two land covers (ETaSim grass and ETaSim shrub) with the observed eddy covariance-derived evapotranspiration (ETaObs).

The simulated ETa from shrubland showed a better agreement with the observed ETa (R2=0.4 to 0.5, slope=0.8 to 1.3). The simulated ETa from shrubland (ETaSim shrub) was higher compared to the simulated ETa from grassland (ETaSim grass) with the observations (ETaObs) in between, confirming that ETaObs represents a mixture of shrubland and grassland contributions. The relative contribution was different for each year due to meteorological conditions. On average across all years, a 51:49% contribution from respectively grassland and shrubland resulted in a good approximation of ETaObs, in particular in 2015 and 2016 growing seasons, characterised by long dry spells. In those growing seasons, the differences between cumulative ETa from simulations and observations were below 10 mm. In the other two growing seasons, more frequent rainfalls and the absence of long dry spell caused cumulative ETa underestimation (-25 mm) in 2014 and overestimation (66 mm) in 2017. Differences between shrubland and grassland were enhanced during dry spells, leading to a cumulative ETaSim shrub more than 100 mm higher than the cumulative ETaSim grass. In the longest dry spells of the growing seasons, ETaObs was closer to ETaSim shrub, confirming the role of deeper roots of shrubs.

The results indicate that the shrub-covered area, expected to increase, plays already a key role in the local hydrological cycle, particularly with changes in water availability.

How to cite: Gisolo, D., Bevilacqua, I., van Ramshorst, J., Knohl, A., Siebicke, L., Gentile, A., Previati, M., Canone, D., and Ferraris, S.: Actual evapotranspiration of abandoned grassland on a slope in the Western Italian Alps: Impact of shrub encroachment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7320, https://doi.org/10.5194/egusphere-egu22-7320, 2022.

09:29–09:35
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EGU22-8389
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ECS
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Virtual presentation
Nikitasha Chatterjee et al.

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.

09:35–09:41
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EGU22-8477
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ECS
Bryan Marinelli et al.

As climate change continues to alter the dynamics of hydrological flows, quantifying the associated environmental impacts become more and more vital.

Here we present a study focusing on analyzing the spatial and temporal distribution of flow components, particularly the contributions of glacier melt, snowmelt, rainfall-runoff, and groundwater flow to river discharge in the high mountain Santa River catchment. The catchment is located in the Cordillera Blanca of Peru, the region with the largest glacier cover in the tropics, and has an area of 12,279 km², an average discharge of 133 m3/s, and average annual precipitation of 750 mm.

We used the spatially distributed cryospheric-hydrological model SPHY, forced with W5E5 meteorological data (1979 - 2019) to simulate daily spatial discharge components. Additional static inputs such as a digital elevation model, land use maps, soil hydraulic properties, and glacier extent, thickness, and debris cover were collected from freely available remote sensing-based datasets.

The model runs at a spatial resolution of 500 x 500 meters with daily time steps. Data from 1995 to 1997 were used to spin up the model. Calibration (1998 - 2001) and validation (1998 - 2018) were performed through the comparisons of simulated and observed discharge. The model's performance was evaluated by the percent bias (1.5%; -7.2%), Nash-Sutcliffe efficiency (0.81; 0.65), and R2 (0.82; 0.68). With the best runs, the complete 41 years were simulated.

Further analysis evaluates how glacier melt and snowmelt compensate the discharge amount in dry periods to meet environmental flow requirements and the derived environmental services chain.

The overall outcome of this assessment will define spatially distributed compensated zones, ensuring an informed management of glacier covered watersheds, as well as open up new horizons to better understand, and mitigate, the impacts of climate change.

How to cite: Marinelli, B., Lutz, A., Breuer, L., Weeser, B., and Correa, A.: Spatially assessing the role of glacier and snowmelt for meeting environmental flow requirements in a high mountain Andean catchment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8477, https://doi.org/10.5194/egusphere-egu22-8477, 2022.

09:41–09:47
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EGU22-9979
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ECS
Florentin Hofmeister et al.

The extent to which climate change affects the frequency and magnitude of flood events in mountain catchments is still unclear due to strong regional differences and a limitation in streamflow observations in space and time. However, recent flood events in Western and Southern Alps from August 2021 highlight the need for new monitoring strategies of peak flood events to better compute return periods of flood events. In particular, measuring peak events in small Alpine catchments can be enhanced by using automated tracer measurement systems. We present results from a hydrometric program using an automated salt dilution system at three different sites in the Tyrolean and South Tyrolean Alps from 2020 and 2021. The AutoSalt system triggers salt slug injections in response to water level changes in the creek while two downstream electrical conductivity probes record the passage of the breakthrough curve with high temporal resolution (5 sec). We collected in total 288 discharge measurements ranging from 0.1 m³/s to 15 m³/s. Besides the requirement of complete mixing of the tracer, the main challenge in automated salt dilution is the monitoring and control of the system components to ensure a high reliability and quality of observation data. The internal quality check of the AutoSalt system allowed us to record mainly discharge measurements (81 %) with a very low measurement error < 7% while 19 % of the discharge measurements had an error range of 7 % to 15 %. Based on the collected discharge measurements and their uncertainties, we constructed robust rating curves with error bars for each site. In a next step, we will use the collected observation data to validate hydrological model results for these three different Alpine catchments to strengthen the robustness of the model for long-term climate change modeling.

How to cite: Hofmeister, F., Rubens Venegas, B., Sentlinger, G., Disse, M., and Chiogna, G.: Automated discharge measurements with salt dilution in Alpine creeks and uncertainty quantification, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9979, https://doi.org/10.5194/egusphere-egu22-9979, 2022.

09:47–09:53
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EGU22-10333
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ECS
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Virtual presentation
Ekaterina Kornilova et al.

Climate change and deglaciation in the 20th and 21st centuries cause runoff changes of a high-mountain regions. Modeling allows to predict runoff changes and possible extreme events in the future. In this research, we performed hydrometeorological data analysis, model calibration and validation in the key parts of the Terek River basin and simulated runoff and it’s components for a long-term historical period.

The Terek River flows from the highlands of the Central Caucasus and streams in an easterly direction, flowing into the Caspian Sea. Runoff modeling of the Terek River was carried out to the Mozdok outlet. The average height of the river basin is 1700 m, the basin area is 20600 km2, of which 34% is the high-altitude part of the basin (>2000 m). A rise in both amount of water availability and potential natural hazard is characteristic of the North Caucasus that is considered to be caused by recent climate change. Mean annual runoff during 1978-2010 increased compared to 1945-1977 by 5-30 % in the foothills and by 30-70% in the plain area.

The ECOMAG runoff formation model (author Y. Motovilov) was adopted for the high-mountain part of the Terek River basin. The input data for the model are meteorological data (temperature, precipitation, air humidity deficit), soil and landscape information, and a digital elevation model, output modeling results – water discharges in a river network. In addition, the runoff formation model allows to analyze all components of water balance in different parts of a river basin and to divide the hydrographs by types of nutrition.

As a result, a long-term historical period from 1977 to 2018 was modeled. Due to the regional features of the river basin, an additional block of the model was included to account the glaciation. In addition to the daily runoff data, the separation of the flow into components in a key part of the river basin (the Baksan River) was used to validate the model. Based on the results of the calibration and verification of the model, a good agreement was obtained between the model and actual discharges for hydrological stations in the mountainous part of the basin. The NSE criterion for the 2009-2018 verification period was 0.75, the simulated and actual volumes of runoff differ by less than 10%.

The Terek River runoff formation model was developed under the financial support of RFBR 21-55-10003. Validation of the model based on the separation of the flow into components were designed within the framework of the Governmental Order to Water Problems Institute, Russian Academy of Sciences, subject no FMWZ-2022-0001.

How to cite: Kornilova, E., Krylenko, I., Rets, E., and Motovilov, Y.: Runoff modeling in the High-Mountain River Basin: A Case Study of the Terek River (Caucasus, Russia), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10333, https://doi.org/10.5194/egusphere-egu22-10333, 2022.

09:53–09:59
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EGU22-12493
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ECS
Laura Belica et al.

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.

Thu, 26 May, 10:20–11:50

Chairpersons: Andrea Momblanch, Marit Van Tiel, Santiago Beguería

10:20–10:26
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EGU22-503
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ECS
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On-site presentation
Rupesh Baniya et al.

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.

10:26–10:32
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EGU22-1882
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ECS
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On-site presentation
Andrea Citrini et al.

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.

10:32–10:38
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EGU22-5028
Léo Martin et al.

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.

10:38–10:44
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EGU22-5821
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ECS
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On-site presentation
Ivo Pink et al.

The Himalayas are of exceptional importance for the water resources in Asia and provide fresh water for more than 1.4 billion people. However, they are also the source of frequent floods with the highest death-per-event rates in the world. The floods are caused by intense monsoon precipitation, but snow melt and glacier melt contribute to the flood peaks. Both, extreme precipitation and melt contributions are predicted to be impacted by climate change but it remains unclear how these changes will alter the flood risk in the region.

This study investigates the impact of climate change on peak runoffs in the transboundary Karnali River Basin (KRB) in Nepal / China using both hydrological and statistical modelling. The fully-distributed cryospheric-hydrological model SPHY is applied for the period 2002-2015 and calibrated and validated using the GLUE framework. The Nash-Sutcliffe efficiency, PBIAS of peak flows and extended GLUE are used as performance indicators for the selection of behavioural parameter sets. The model is run with the selected parameter sets and the outputs of 13 downscaled and bias-corrected CMIP-6 models of three different scenarios (historical, ssp245, ssp585) to quantify the climate-change-induced changes in peak flows until the end of the century. Extreme Value Analysis is then applied to estimate the exceedance probability from the simulated annual maximum flows for the climate models, scenarios and hydrological parameter sets.

The results indicate an increase in flood hazard frequency and magnitude until the end of the century. The mean magnitude of an event with 2% annual exceedance probability (AEP) increases by 23% (±19%) in the period 2020 - 2059, and 42% (±19%) in the period 2060 - 2099 for ssp245, and 28% (±23%) in the period 2020 - 2059 and 82% (±41%) in the period 2060 - 2099 for ssp585 compared to the baseline period (1975 - 2014). Flows with a 50 year return period (2% AEP) during the baseline period (10,900 m3/s) are projected to occur every 9 years in the period 2020 - 2059 and 7 years in the period 2060 - 2099 for ssp245 scenario, and every 9 and 3 years for ssp585 scenario, respectively. Glacier and snowmelt contributions are projected to change in terms of seasonality and quantity but the increase of peak flows is mainly driven by the increase in extreme precipitation.

How to cite: Pink, I., Reaney, S., Bovolo, I., and Hardy, R.: Increased flood hazards within the Himalayan Karnali River catchment predicted for an ensemble of CMIP-6 climate change scenarios, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5821, https://doi.org/10.5194/egusphere-egu22-5821, 2022.

10:44–10:50
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EGU22-6024
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ECS
Shaktiman Singh et al.

Tajikistan occupies only 11% of the territory of Central Asia. However, more than 65% of the region’s water resources are formed in the mountainous areas of this country. Changing water availability in mountain regions has a strong impact on water-dependent economic sectors such as energy and agriculture. Anthropogenic climate change is projected to bring about considerable changes to both the timing and volume of water in the long term through rising temperatures, increased snow and glacier melt and a more variable rainfall regime. However, there is limited understanding of what the impact on Tajikistan’s water resources will be, associated with uncertainty around the climate projections and the rate of depletion of the region’s glaciers. In Tajikistan, two-thirds of agricultural production is irrigated, but many farmers still must make a living from rain-fed land, which is even more vulnerable to drought and climate change. In addition to climate change impacts, the potential for conflict in the region is exacerbated by the current high population growth rate of between 2.5% and 3.4% per year. As living standards improve and demand resources increase, pressures on scarce water resources heighten.

Water resources management in Tajikistan is in a state of transition from a centralized administrative approach that existed for more than 30 years to a more integrated river basin approach, as proposed under the current sector reforms. While the current reforms are an essential move towards Integrated Water Resources Management (IWRM), there is still much to be done in the development and implementation of such a strategy. Some of the main issues in this regard is the absence of reliable information on water resources and the need to update old monitoring systems to better understand the behaviour of the water resources systems in the country.

This research focuses on the Zarafshan River, where efforts to implement IWRM started a few years ago, and it is an example of an application for the development of IWRM in other basins in the country. We will present the work carried out to better understand the hydrological balance in the basin incorporating snow and ice melt dynamics by combining the SWAT model with satellite images of daily snow cover.

How to cite: Singh, S., Bhardwaj, A., Sam, L., and Haro Monteagudo, D.: Tackling the global change challenges to water security in Tajikistan, the water tower of Central Asia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6024, https://doi.org/10.5194/egusphere-egu22-6024, 2022.

10:50–10:56
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EGU22-6905
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ECS
Rakesh Kumar Sinha et al.

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.

10:56–11:02
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EGU22-7263
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ECS
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Virtual presentation
Swatantra Kumar Sharma et al.

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.

11:02–11:08
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EGU22-7604
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Virtual presentation
Roger Clavera-Gispert et al.

The natural border between Andorra, France and Spain are the Pyrenees, a South-Western European mountain range with a great environmental diversity: from Atlantic to Mediterranean climates, from high mountains to cliffs touching the sea, and from humid to semi-arid  conditions. Thus this region is particularly sensitive to climate and global change. On the other hand, this territory is the primary source of water in the region, feeding the runoffs and recharge zones of the region's main catchment basins. Rapid changes in the environment can have an influence on the availability of water resources downstream, increasing the uncertainty to an already tough water management situation.

Scientists use hydrological data to detect and quantify climate variability and change. Although data from gauging stations are basic to study the temporal evolution of water resources, more than these punctual data are needed for a regional study, as many relevant variables of the water cycle, such as evaporation, are seldom observed. Furthermore, models are necessary to study the future climate, but we need first to check if the models faithfully reproduce the intended processes. Therefore, hydrological modeling plays an important role in water resources studies, as they allow us to quantify the main components of the water balance (precipitation, evapotranspiration, drainage/recharge, runoff and streamflow) and the main stocks (soil moisture and snow) for the entire region. 

We have used observation values from non-influenced gauging stations and hydrological outputs of two different modeling tools (the fully distributed model SASER, and the semi-distributed model SWAT) to study the historical evolution (1979-2014) of the natural continental water cycle in the Pyrenees. The comparison of observational data with models, as well as models between them, will allow us to detect, evaluate and analyze the main sources of uncertainty.

We computed monthly, seasonal and annual statistics for three time periods (1979-2014, 1989-2014 and 1999-2014). Thus, we made and analyzed trends for the time series of the different variables applying a time series pre-whitening. These trends have been calculated with the Sen's slope estimator assuming that they are linear. The significance of the trends was estimated with the Mann-Kendall test on the pre-whitened time series with the statistical significance tested at the 95% level.

This work is a contribution to the EFA210/16 PIRAGUA project.

How to cite: Clavera-Gispert, R., Quintana-Seguí, P., Beguería, S., Palazón, L., Zabaleta, A., Cenobio, O., and Barella-Ortiz, A.: Study of historical evolution (1979-2014) of key water cycle variables in the pyrenees using observations and modeled data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7604, https://doi.org/10.5194/egusphere-egu22-7604, 2022.

11:08–11:14
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EGU22-7621
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Highlight
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Virtual presentation
Pere Quintana-Seguí et al.

Mountainous areas are an important source of water resources, especially in the Mediterranean. The PIRAGUA project aims at assessing the water resources of the Pyrenees in the past and in the future. To this aim, different modelling approaches were used in order to assess the water resources of the Pyrenees and their future evolution. 

In this study, statistically downscaled climate scenarios, generated within the CLIMPY project were used in order to force four different modelling tools: SWAT, SURFEX, RECHARGEand GIS-Balan. SWAT is a semi-distributed hydrological model, SURFEX is a distributed physically based land-surface model, RECHARGE is a simple potential recharge estimation method base on water balance model for effective precipitation computation and GIS-Balan is a GIS-based groundwater model. 

With SWAT and GIS-Balan we used a delta-change approach to apply the scenarios, and with SURFEX and RECHARGE we used an analogue methodology, which used the SAFRAN-PIRAGUA gridded dataset of meteorological variables as the observational dataset. This way, we covered many sources of uncertainty, and provided an incomplete, but large, representation of the sources of uncertainty (GCMs, RCPs, downscaling methods and hydrological models) at play.

In this exercise, we found that the resulting uncertainties are rather large for almost all variables except temperature. Temperature will very likely increase more than 4 degrees at the end of the century for the RCP85 scenario. Precipitation changes, however, are quite uncertain, although we should expect decreases on the northern slope of the Pyrenees. On the southern slope, the different projections disagree on the sign of the change. They also agree on increases of precipitation on the eastern basins of the domain (Mediterranean), while it is very likely that there will be less solid precipitation (snowfall) in the future. From here, the uncertainties increase, due to the non-linearity of the hydrological models. In the SWAT approach, aridity does not change on average. However, SURFEX projects a likely increase in aridity all over the domain. In terms of water yield, SWAT presents a drier future on the northern and western slopes, but wetter on the southern and eastern slopes. SASER shows a similar picture but is generally much drier than SWAT in the future. In terms of seasonality, the water yield will decrease mainly in summer, but also in spring and autumn and, according to SASER, also in winter, especially for the RCP85 scenario. The RECHARGE model leads to a general decrease of the potential recharge over the whole domain that could be more severe in the northern and southern part of the Pyrenees than in the Central part. The GIS-Balan models report a clear decrease in total discharge flow of the basins, which is most pronounced in the RCP8.5 scenario.

We hope that these results, although uncertain, will serve to plan for the certainty that changes in the annual means and seasonality of the water cycle are coming, even if we do not know clearly what these changes will look like. 

This work has been funded by the EFA210/16 PIRAGUA project.

How to cite: Quintana-Seguí, P., Caballero, Y., Cakir, R., Clavera, R., Dewandel, B., Grousson, Y., Hevin, G., Jódar, J., Lambán, L. J., Lanini, S., Le Cointe, P., Llasat, M. C., Sauvage, S., Sánchez-Pérez, J. M., Palazón, L., Vidal, J.-P., Zabaleta, A., and Beguería, S.: Estimation of the future water balance and water resources of the Pyrenees, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7621, https://doi.org/10.5194/egusphere-egu22-7621, 2022.

11:14–11:20
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EGU22-7825
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ECS
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Virtual presentation
Leticia Palazón and Santiago Beguería and the PIRAGUA Team

The Pyrenees range is a transboundary mountain region shared by Spain, France and Andorra. As many other mountain regions, the Pyrenees host the upper catchments and recharge zones of the region's main river basins and aquifers. Therefore, it is the main source of water resources that are used in a much larger area that includes important urban concentrations and highly productive rural areas. This territory and its water resources are particularly vulnerable to the consequences of climate change. The PIRAGUA project (2018-2021, https://www.opcc-ctp.org/piragua), funded by FEDER through the POCTEFA Program of the EU, addressed the characterization of the hydrological cycle of the Pyrenees in a climate change context, in order to improve the territories’ adaptation capacity. The goals of the project were to unify and homogenize the existing information, prospect future scenarios, develop indicators of change, and propose adaptation strategies with impact on the territory. The project results were compiled in a series of regional datasets, and are available through the geo-portal of the Pyrenees Climate Change Observatory (https://opcc-ctp.org/geoportal). These include the following resources: PIRAGUA_resources stores information related to water resources use, exploitation and management; PIRAGUA_indicators contains daily streamflow and aquifer level indicators from observed series during the historical period (1950-2019); PIRAGUA_flood includes the number and classification of flood events, at the municipal level; PIRAGUA_atmos_analysis contains observation-based meteorological data suited for hydrological simulation, for the historical period (1981-2010); PIRAGUA_atmos_climate is a  statistical downscaling of six global climatic models, for the historical and future periods (1981-2100); finally, two datasets include the hydrological water cycle components derived from simulations with different hydrological models (SWAT, SASER, GIS-BALAN and RECHARGE) and climate forcings: PIRAGUA_hydro_analysis (1981-2010) and PIRAGUA_hydro_climate (1981-2100). This contribution is devoted to describing these datasets and the tools to explore them and acquire the data, and to provide examples of the main results regarding the climate change effects on the Pyrenees’ water resources.

How to cite: Palazón, L. and Beguería, S. and the PIRAGUA Team: Water cycle and water resources of the Pyrenees under climate change: the PIRAGUA datasets., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7825, https://doi.org/10.5194/egusphere-egu22-7825, 2022.

11:20–11:26
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EGU22-8002
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ECS
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Virtual presentation
María Herminia Pesci et al.

Mountainous regions are viewed as “water towers”, where lower temperatures and higher precipitations affect the annual water balance with snow accumulation in winter and maximum runoff driven by snowmelt during spring or summer. Moreover, the need for effective water resources management has turned into a major challenge, especially in the face of climate change. The current development of computer models allows representing the response of catchments even under the impact of changing climate conditions. For this reason, the Devoll catchment in Albania, which is characterized by a Mediterranean climate and varying topography, is studied as part of a modelling chain up to the Banja reservoir, where sedimentation processes are of great importance.
Three different models are used to predict the response of the catchment within the modeling chain: i) a hydrological model (WaSiM), ii) a soil erosion and transport model (RUSLE and SEDD), and iii) a three-dimensional numerical model (SSIIM 2) to simulate flow and suspended sediment transport in the reservoir. Since numerous parameters are involved in the chain and those can introduce uncertainties in the subsequent models, an approximate method is applied to estimate the uncertainties arising from the model parameters, whereby each parameter is subject to a ±1% variation. In addition, climate change impacts are considered while running the modeling chain with different climate scenarios. In all cases, we focus not only on discharge as a target variable but also on the suspended sediment load and bed elevation along the reservoir transect. Finally, a comparison between the results obtained from the variation in parameters and climate change impacts is performed.

How to cite: Pesci, M. H., Mouris, K., Bosshard, T., and Förster, K.: How do changes in model parameters compare to climate change impacts signals? A case study of a modeling chain to predict reservoir inflow and sedimentation processes in the Devoll Catchment (Albania), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8002, https://doi.org/10.5194/egusphere-egu22-8002, 2022.

11:26–11:32
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EGU22-10454
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ECS
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Virtual presentation
Joachim Meyer et al.

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.

11:32–11:38
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EGU22-11899
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ECS
Naomie Kayitesi Manishimwe and gregoire mariethoz

Tropical regions have experienced rapid Land Use Land Cover Change (LULCC) in the last decades. Furthermore, climate change will likely intensify these changes due to global warming and increased frequency of extreme events. These changes have diverse effects on watershed and river hydro-morphological processes through alterations of the rainfall and runoff patterns, which translate into changes in the water balance components. The magnitude of these effects depends on the watershed characteristics, including the size, extent of change, topography, soil characteristics, and climate. Understanding the watershed hydro-morphological responses to changes in both climate and LULC –especially in tropical regions where rainy seasons are followed by dry seasons— is vital for effective land and water resources management in the face of future changes.

Sebeya catchment in the western part of Rwanda is prone to flooding, associated with erosive processes, and mass movements. Hence, destroying infrastructures and houses, damaging crops, and taking people’s lives yearly during long rainy season (February to May). This is partly attributed to the combination of steep topography and the loss of forest cover on fragile soils, coupled with the increased prevalence of extreme rainfall events. The hypothesis is that the hydro-morphological characteristics of Sebeya river have changed in the last few decades as a result of LULCC, including forest clearing from agriculture and built-up development. In light of it, this study intends to quantify changes in LULC of the Sebeya catchment over the last three decades, and predict future changes in the next three decades, using remote sensing data and LULC model. Furthermore, a hydrologic model will be used to simulate and forecast the associated changes in hydro-morphological and flood frequency.

How to cite: Kayitesi Manishimwe, N. and mariethoz, G.: Modeling River hydro-morphological responses to Land Use Land Cover Change in Tropical Regions, case of Sebeya catchment, Rwanda., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11899, https://doi.org/10.5194/egusphere-egu22-11899, 2022.

11:38–11:43
Wrap-up and farewell