Displays

The study analyzed long-term changes of runoff variability of headwater montane basins in Central Europe as a response to the effects of climate change and modifications to the environment.

The aim was to compare the patterns of variability of the indicators of hydrologic alteration, derived from long-term time series of daily discharge observations in montane basins with the recent premises of climate change effects on surface runoff dynamics in the Central Europe region. In particular, there were tested the following assumptions: (i) recent climate warming will result in the shifts of the runoff seasonality and distribution and in (ii) higher variability of runoff, displayed by a higher frequency of floods and droughts, while (iii) the indicators of runoff balance will remain without significant changes.

These hypotheses were tested in a set of 8 unregulated montane catchments, spreading over the border mountain ranges of the Czech Republic - the Šumava Mountains (Bohemian Forest), Krušné hory (Ore Mountains), Jizera Mountains, Krkonoše (Giant Mountains), Orlické Mountains and Beskydy Mountains. All basins are of comparable size (30-90 km2), and without significant hydrological regulations. Their west-east geographical distribution allows for tracking the potential effects of the gradient of climate continentality in the Central European region. The uninterrupted time series of daily discharge observations from 1953 to 2018 were used for the analyses at the gauging stations. 

We focused on indicators that reflect the aspects of the runoff regime, that are likely to be affected by the assumed effects of the changing climate. Variety of time series analysis and statistical techniques was applied, including the set of 33 Indicators of hydrologic alteration (IHA), 34 Indicators of Environmental flow components, frequency and distribution of the peak an low flows, statistical testing of significance of changes using Mann-Kendall test, breakpoint analysis, analysis of deficit and surplus volumes and homogeneity testing using Buishand, Petitt and SNHT tests.

The study has identified the significant shifts in the hydrological response of montane basins that are apparent in seasonality, balance, and variability of discharge. The analyses proved (i) changes in runoff response reflecting the timing of the observed changes in air temperatures, (ii) the shift of spring snowmelts towards earlier spring and a corresponding decline of may flows, occurring in all of the investigated regions, (iii) diverging trends of high flows across the basins, (iv) changing dynamics of rainfall-runoff response (v) better sensitivity of indicators, reflecting low magnitude events and (vi) decline of low flow indicators across the basins.

How to cite: Langhammer, J. and Bernsteinová, J.: Effects of climate change on runoff variability in mid-latitude montane basins, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13273, https://doi.org/10.5194/egusphere-egu2020-13273, 2020.

The Pyrenees are the "Water Towers" of several key river basins in France, Andorra and Spain, being the Adour-Garonne and the Ebro the largest ones. The water of these basins is used by agricultural and industrial economic sectors which have a significant socioeconomic impact. Furthermore, the water of these rivers also sustains ecosystems which have an intrinsic value and provide ecosystem services to society. For this reason, an assessment of the past and future evolution of the water resources of the Pyrenees is necessary. Until now, these assessments have often been done at the basin or at the national level, but never the water resources of the Pyrenees were assessed as a whole. This is the main aim of the PIRAGUA project, within which we develop our research.

In order to simulate the continental water cycle of the Pyrenees we have used the SASER (SAFRAN-SURFEX-Eaudyssée-RAPID) modeling chain. SAFRAN is a meteorological analysis system, that allows us to create a gridded dataset of all the variables needed by the SURFEX land-surface model. SURFEX’s outflows (runoff and drainage) are used by Eaudyssée and RAPID to calculate streamflow.

Until now there were two separate implementation of SAFRAN in France (8 km resolution) and Spain (5 km resolution). For this project we have taken the climatic zone level SAFRAN data of both countries and interpolated it to a new common grid at a resolution of 2.5 km. The dataset covers a domain that includes the Adour-Garonne, the Ebro and all other Pyrenean river basins, its time period is 1979/80-2014/15 (which will be extended to 2016/17). The RAPID river routing scheme has been implemented in the simulation domain using HydroSheds to describe the river network.

In order to simulate the future evolution of the continental water cycle we use the Pyrenean climate scenarios developed within the CLIMPY project. These include precipitation and maximum and minimum temperature. SURFEX needs other variables too, such as wind speed, relative humidity and radiation. We solve this problem using an analog based approach similar to Clemins et al (2019).

The simulated streamflow is compared to observed streamflow of natural basins. The results show that 18 (out of 38) non influenced stations present a KGE of daily streamflow larger than 0.5. For monthly streamflow, KGE is larger than 0.5 on 22 stations (out of 38).

The next steps of our research are to quantify the improvement due to the increased resolution (comparing to a lower resolution simulation), calculate trends of relevant variables at the sub-bassin scale and compared them to the observed ones in the past, and analyze future trends of these variables. Finally, we will assess the impacts of these changes on water resources.

This research is funded by the EFA210/16-PIRAGUA project, within the INTERREG V-A España-Francia-Andorra POCTEFA2014-2020 program.

How to cite: Quintana-Seguí, P., Barella-Ortiz, A., Cenobio-Cruz, O., Vidal, J.-P., and Zabaleta, A.: Analysis of the past and future water resources of the Pyrenees by means of a land-surface simulation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10400, https://doi.org/10.5194/egusphere-egu2020-10400, 2020.

The Pyrenees range is a transboundary region shared by Spain, France and Andorre whose water resources are diverse (snowmelt and rainfall runoff in a topographically variable context, groundwater in complex and heterogeneous aquifers) and poorly known. As many other mountain regions, this territory is particularly vulnerable to the impacts of climate change. In the framework of the PIRAGUA project, funded by FEDER through the EU POCTEFA Program, the potential groundwater recharge from precipitation was estimated over the last 30 years at the scale of the Pyrenean range.

Using the meteorological forcing data provided at high spatial resolution in the framework of the PIRAGUA Project, the effective rainfall was computed at the daily time step using three different simple water balance methods, including land use effect on evapotranspiration (crop coefficients method) over the 1981-2010 period. Resulting effective precipitation ranges from 50 to more than 2000 mm/year on average and shows strong differences between the east and west sides of the Pyrenean chain.

Potential groundwater recharge from precipitation was then estimated using an effective precipitation infiltration ratio derived from the comparison of the IDPR geomorphological index to the baseflow index extracted from selected river discharge time series over the Pyrenees. The resulting potential recharge was finally averaged at the groundwater bodies’ scale of the Pyrenean chain.

Corresponding potential groundwater resources were finally compared to groundwater uses estimated at the Pyrenean scale in order to 1) assess their respective importance in relation to water uses and 2) identify the sectors of the territory for which situations of tension on groundwater resources could already be observed, tensions which are likely to increase in the context of climate change.

How to cite: Caballero, Y., Lanini, S., Hevin, G., Le Cointe, P., Pinson, S., Desprats, J.-F., Le Coent, P., and Dewandel, B.: Assessing the potential groundwater recharge from precipitation in the Pyrenees in the global change context, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11287, https://doi.org/10.5194/egusphere-egu2020-11287, 2020.

We present preliminary results in fulfilment of the IT-CH Interreg project “GE.RI.KO Mera”. The main aim of the project is to create a common strategy for the management of common water resources, in the transboundary Mera catchment, laid for ¼ in Switzerland, and for ¾ in Italy. Mera river sources in the Maloja mountains of Switzerland, crosses the Bregaglia valley, and reaches Valchiavenna of Italy, then receiving Liro river’s water, and then flows into the Novate-Mezzola lake, and in Como lake soon after.

This area is particularly important, for hydropower production, and large exploitation of water resources for fishing, and leisure in general.

Bregaglia valley carries large sediment load in the river, which affect aquatic species during floods, and lead to progressive filling of hydropower basins, and sediment accumulation along the river, with potential for increased flood risk, and often need for removal. GE.RI.KO project aims to jointly manage the transboundary waters of the Mera river to i) limit alteration of riverbed morphology and erosion, ii) avoid biodiversity loss, and iii) reduce flood risk along the river.

Here we report modelling of hydrology of this high altitude basin with Poli-Hydro model, and an analysis of future climatic conditions in the area of Valchiavenna for different Representative Concentration Pathways (RCP). We use several RCPs from IPCC’s AR5/6, and several GCMs, for a grand total of 21 climate scenarios (plus local downscaling) to force the Poli-Hydro model to depict future hydrological scenarios in the area.

We report main potential hydrological variations, and depict main challenges for water management in the Mera catchment under future scenarios, to be explored by the GE.RI.KO project.

How to cite: Bocchiola, D., Casale, F., Stucchi, L., and Bombelli, G.: Future hydrology of Alpine rivers of Italy: the Interreg project GE.RI.KO Mera, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20231, https://doi.org/10.5194/egusphere-egu2020-20231, 2020.

Catchments of European mountains are essential because of their role to provide water to human society. Mountainous area regulate water flux through a complex system of storage and release, playing the role of water tower. Better understand the dynamic functioning of this system at the scale of each compartment and the relationships between the storage and releasing processes are important to understand the impact induced by climate change. In particular, the disappearance of snow during the winter will potentially modify the low flow water level and ecological flow in late spring and early summer, impacting the ecological services provided by e.g. ponds, peat or wetland. The presented study aims to identify the keys factors and their current role in this hydrological system of the Pyrenean Mountains, and identify critical hydrological conditions that will potentially impact the socio-ecological services related to water resources. This goal has been achieved by a development of a high resolution hydrological modeling framework at the scale of the entire Pyrenean massif, together with the study of lower scale representative systems (peatland) and the development of specific future climate scenarios, in order to suggest mitigation actions and adaptability action through water management.

How to cite: Grusson, Y., Dalibard, M., Raimonet, M., Sauvage, S., Leroux, G., Begueria, S., Palazon, L., and Sánchez Pérez, J. M.: Better understand mountain hydrology to enhance climate change impact assessment, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18759, https://doi.org/10.5194/egusphere-egu2020-18759, 2020.

The Pyrenees are a fundamental source of water resources for the territories surrounding this mountain range and beyond, and like other mountainous areas they are very vulnerable under global change. The CLIMPY project (Interreg-POCTEFA) calculated an increase of 1.5 ℃ on average temperature for this region in the last 60 years.

One of the aims of the PIRAGUA project (Interreg-POCTEFA) is to make a regional and temporal characterisation of the water resources of the Pyrenees. To achieve that objective, a common standardized and homogenized database was created for the first time in this transboundary region with streamflow data measured by the different water agencies operating in the area (1956-2015).

To avoid human impacted gauging stations (e.g. upstream reservoirs and large irrigation withdrawals), and to analyse only those with a reasonable quality, only a number of the initially obtained streamflow series were considered. A set of indicators was calculated from the selected daily streamflow series concerning mean, high and low flows at annual and monthly scales for different time periods ending in 2015. 

Results show that median discharge decreased an average of 30% in all gauging stations between 1956 through to 2015. High and low streamflow also decreased during the same period. On average, the number of days below the first quartile increased 10 days per decade, and the number of days above the third quartile decreased 6 days per decade. The interquartile range decreased 4% per decade on average showing that streamflow suffered a generalised reduction between 1956 and 2015. Regarding monthly streamflow, trends for median streamflow and the first quartile are similar to the annual scale. The most significant decrease is observed during spring (12-15% on average), and the lowest decrease occurs in the autumn (6-9% on average). Since 1986, trends change and streamflow increases are observed at some gauging stations with results that are spatially very heterogeneous. This inflection may be an effect of a more spatially heterogeneous climate in the recent past or of land use changes that are not regionally homogeneous, or a combination of both.

How to cite: Zabaleta, A., Haro-Monteagudo, D., Antiguedad, I., and Beguería, S.: Past hydrological trends on the Pyrenees: towards a higher spatial heterogeneity, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10370, https://doi.org/10.5194/egusphere-egu2020-10370, 2020.

The mountains are known as the water towers of the World and they are also climate hot spots. Therefore, water availability studies are extremely useful. To this purpose, Evapotranspiration analyses are important because it plays an essential role in water balance. Its estimation is an important challenge in complex terrains because of few measurement sites and of models’ resolution. Research on both meteorological and hydrological models is still ongoing and there are multiple aims: better catch the physical processes in the atmosphere and in the soil and simulate the reaction of ecosystems to temperature changes, droughts and vegetation shifts towards higher altitudes.

It is therefore important to elaborate new tools for the monitoring of mountain environments and ecosystems from a meteo-hydrological and also climatological point of view.

We elaborated and used a high-resolution model to compute the evapotranspiration field of an Alpine domain located in Italy. The model includes a meteorological module and a hydrological module, which is based on a soil bucket approach. The model allowed us to estimate the local water balance and was validated using three eddy covariance quality-controlled data sets. Furthermore, it was also compared to satellite products. The first results indicate a rather good agreement between simulations of our model, observations, and satellite evapotranspiration estimates.

These are first, encouraging results and the model will be hopefully used in a climate change perspective by means of climate models' outputs, to simulate future scenarios in the Alps.

How to cite: Gisolo, D., Bevilacqua, I., Previati, M., Canone, D., Gentile, A., N'Sassila, M., and Ferraris, S.: Mapping evapotranspiration of a mountain area using a model without calibration, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-860, https://doi.org/10.5194/egusphere-egu2020-860, 2020.

The Mediterranean mountains have been subject to significant land abandonment processes during the second half of the 20th century.  The subsequent natural revegetation following abandonment in rural areas has been widely documented to have significant implications on the hydrological cycle and the vegetation dynamics. The Spanish Pyrenees, are one of the most affected areas by these land transformations which could threaten their importance for water supply and agricultural activities in the downstream lowland areas.

Management strategies of these abandoned areas have been debatable during the last decades between scientists, policy-makers and stakeholders. Active Management strategy through shrub clearing is one of the proposed practices that have shown advantages to deal with land abandonment in some regions of Spain. Nevertheless, little is known on the effects of this practice on the hydrological cycle and water resources in abandoned areas. In this study we used the Regional Eco-Hydrological Simulation System RHESSys to estimate shrub clearing effects on water resources in the Aisa valley in the Central Spanish Pyrenees, subject to land abandonment and natural revegetation processes during the past decades. Our results show an increase of annual streamflow and a decrease of annual evapotranspiration following shrub clearing. Nevertheless, the magnitude of these changes may decrease with the age of abandonment and climate change.

How to cite: Khorchani, M., Nadal-Romero, E., and Lasanta, T.: Shrub clearing as Active Management strategy to control land abandonment in the Central Spanish Pyrenees: The effects and the limits, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1123, https://doi.org/10.5194/egusphere-egu2020-1123, 2020.

As a link between the atmosphere and the earth’s surface, the hydrological cycle is impacted by both climate change and land use/cover change (LUCC). For most basins around the world, the co-variation of climate change and LUCC will continue in the future, which highlights the significance to explore the temporal-spatial distribution and variation mechanism of runoff and to improve our ability in water resources planning and management. Therefore, the purpose of this study is to propose a framework to examine the response of runoff to climate change and LUCC under different future scenarios. Firstly, the future climate scenarios under BCC-CSM1.1 and BNU-ESM are both downscaled and bias-corrected by the Daily bias correction (DBC) method, meanwhile, the future LUCC scenarios are predicted by the Cellular Automaton-Markov (CA-Markov) model according to the integrated basin plans of future land use. Then, based on the baseline scenario S0 (meteorological data from 1966 to 2005 and current situation LUCC2010), the following three scenarios are set with different combinations of future climate land-use situations, i.e., S1: only climate change scenario; S2: only the LUCC scenario; S3: climate and LUCC co-variation scenario. Lastly, the Soil and Water Assessment Tool (SWAT) model is used to simulate the hydrological process and quantify the impacts of climate change and LUCC on the runoff yield. The proposed framework is applied to the Han River basin in China. Results show that: (1) compared with the base period (1966-2005), the annual rainfall, daily maximum, and minimum air temperature during 2021-2060 will have an increase of 4.0%, 1.8℃, 1.6℃ in RCP4.5 while 3.7%, 2.5℃, 2.3℃ in RCP8.5, respectively; (2) from 2010 to 2050, the forest land and construction land in the Han River basin will have an increase of 2.8% and 1.2%, respectively, while that of farmland and grassland will have a decrease of 1.5% and 2.5%, respectively; (3) comparing with the single climate change or LUCC scenario, the co-variation scenario possesses the largest uncertainty in runoff projection. Under the two concentration paths, there is a consistent upward change in future runoff (2021-2060) of the studied basin compared with that in the base period, furthermore, the increase rate in RCP4.5 (+5.10%) is higher than that in RCP8.5 (+2.67%). The results of this study provide a useful reference and help for water resources and land use management in the Han River basin.

How to cite: Tian, J., Guo, S., and Xu, C.-Y.: A framework for quantifying the impacts of future climate and land use/cover changes on runoff in the Han River basin, China , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1979, https://doi.org/10.5194/egusphere-egu2020-1979, 2020.

Knowledge of recharge processes in groundwater resource areas is of great importance for developing sustainable water management plans. In an effort to enhance the understanding of recharge in a basalt aquifer, a national water balance soil moisture model was compared with the response in water tables in multiple private pumping bores across the Tamborine Mountain plateau located in South East Queensland, Australia. The water levels in the pumping bores were influenced by the everyday use of the bores, which are utilised for household supply, stock watering, garden watering and irrigation. In each bore, the pumping response was identified and filtered out before being compared to the soil moisture model results. The soil moisture model (AWRA-L Australian Water Resource Assessment Landscape) includes results of surface runoff, soil moisture, evapotranspiration and deep drainage, to a depth of 6 m. The simulated soil moisture levels in the rootzone (rootzone defined as depth between 0 - 1 m), showed a similar hydrographic response following rain events to that observed in water levels in the aquifer. The response in the aquifer compared to the soil moisture showed some of the deeper bores had a lag effect and furthermore, the response also showed dependency on the soil moisture level (%) and on the size/duration of the rain event. It was observed that the simulated deep drainage (recharge) did not correlate to the observed changes in water tables. The soil moisture model simulated a nearly constant deep drainage (recharge) of 0.05±0.01mm a day, whereas the bores showed large increases in water table in response to rainfall events. Previous studies in the area based on the chloride mass balance approach have estimated that the annual deep drainage volume was an average of 30% of annual rainfall, while the soil moisture model approach has simulated an annual deep drainage volume of 1.2 – 1.7% of the total annual rainfall. While these results show that there are shortcomings related to applying the soil moisture model to estimate aquifer recharge, these results are an important initial finding regarding the estimation of recharge in the study area and can be used in water balance calculations for water management purposes. With further research into the observed relationships and parameterisation of these relationships, the soil moisture model could be updated to better represent recharge within this, and similar, study areas.

How to cite: Gurieff, L. B. and Reading, L.: Improving the understanding of recharge in a basalt aquifer based on a soil moisture model, water levels and climatic data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2814, https://doi.org/10.5194/egusphere-egu2020-2814, 2020.

Vilcanota river watershed is located in Cusco region in Peruvian Southeast mountain, on the Atlantic slope. This watershed is important for  cities located within the Cusco region, since it supplies water for human consumption and for agricultural and livestock production. Therefore, it is important to understand the hydrological behavior of the watershed, in order to determine water availability for the past, present and future periods, and to be able to make better decisions.

We analyze  evolution of hydrology in the Vilcanota river watershed, with changing climates and ground cover. To achieve the goal, we propose the use of a flexible modeling platform, such as the unified approach to process-based hydrological modeling called Structure for Unifuing Multiple Modeling Alternatives (SUMMA), which contains a general set of conservation equations, providing flexibility to experiment with different spatial representations, different flux parameterizations, different model parameter values ​​and different time stepping schemes. This modeling platform will allow us to reduce the uncertainty in the structure of hydrological models and thus obtain correct results for the right reasons. The historical data, meteorological forcing, and the streamflow measurement data, taken from the Peruvian National Meteorological and Hydrological Service (SENAMHI) database, is  used to run  the model at a subdaily  level. The performance of the model, is evaluated through objective functions  selected to adequately represent the behavior of the hydrology of the watershed, both at high and low flows. allowing us to obtain good results in hydrology projections during wet and dry periods.

Preliminary results show that in the historical data of the watershed there is a slight trend in the increase in runoff, attributed to the change in ground cover.

How to cite: Saavedra, D., Mendoza, P., and Vargas, X.: Vilcanota river watershed Hydrology - Peru: Evolution in a changing climate and soil cover., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3114, https://doi.org/10.5194/egusphere-egu2020-3114, 2020.

The present contribution shows a spatial and temporal analysis of the flood events in the Pyrenees area for the period 1981-2015. Seven regions from Spain, Andorra and France conform the mountain range: Basque Country, Navarra, Aragon and Catalonia, in Spain; Nouvelle-Aquitaine and Occitanie, in France; and Andorra country. Although some flood databases exist for these countries, usually they only include catastrophic flood events for some regions (i.e. FLOODHYMEX – Llasat et al, 2013- include Catalonia and Languedoc-Roussillon). This contribution shows a new flood geodatabase for the whole Pyrenees mountain chain, developed into the framework of the PIRAGUA project (Interreg POCTEFA EFA210/16). In order to have homogeneous information for all the regions, several data sources have been analysed for this period. The methodology used in the database development, the type of information and the structure of the database, are presented. In order to show the localities affected by floods, different maps of the municipal distribution of flood events have been developed. A flood event is defined as an episode along which one or more surface water floods have been recorded in one or more regions. They are usually produced because of heavy rainfall events. Some statistics on temporal distribution, and an identification of the most important events have been carried out. 182 flood events have been identified for the whole region, classified in catastrophic, extraordinary and ordinary flood events. 41 flood events affected more than one region and 9 of them were catastrophic in at least one. 11% of the events caused a total of 140 casualties in the study period, showing the importance of orography and land-use on the exposure of mountainous areas to flood events, especially in flash flood events. Besides punctual information on maximum rainfall provided by meteorological stations, the rainfall field has been analysed from the SAFRAN reanalysis. Finally, the weather types associated to the flood events have been obtained using the Jenkinson and Collison classification (Jenkinson and Collison, 1977).

Jenkinson AF, Collison FP. 1977. An initial climatology of gales over the North Sea. Technical Report, Synoptic climatology Branch Memorandum No. 62, Meteorological Office, Bracknell, UK, 18 pp.

Llasat MC, Llasat-Botija M, Petrucci O, Pasqua AA, Rosselló J, Vinet F, Boissier L. 2013. Towards a database on societal impact of Mediterranean floods within the framework of the HYMEX project. Nat. Hazards Earth Syst. Sci. 13(5): 1337–1350.

How to cite: Aznárez-Balta, M., Llasat, M. C., Llasat-Botija, M., Cortès, M., Gilabert, J., and Quintana-Seguí, P.: Floods in the Pyrenees region: the PIRAGUA-FLOOD geodatabase, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5462, https://doi.org/10.5194/egusphere-egu2020-5462, 2020.

Precipitation in mountainous areas provides abundant water resources for downstream regions, and reliable precipitation data in these areas is of crucial importance for the management of water resources and water-related disasters. Because in-situ precipitation data are usually scarce in mountainous areas, satellite-based precipitation products are expected to play an important role; however, they should be carefully validated before application. This study evaluated the performance of three high-resolution precipitation products in the mountainous Qingyi River basin, by comparison with both rain gauge-based and water budget-based methods. The basin is located at the eastern margin of the Tibetan Plateau, and has high precipitation leading to high runoff (~1100 mm/year). The three precipitation products are CMPA (the China Merged Precipitation Analysis), IMERG (the Integrated Multi-satellitE Retrievals for GPM) and GSMaP (the Global Satellite Mapping of Precipitation). In general, both rain gauge-based and water budget-based methods showed that CMPA has the highest accuracy and IMERG has the poorest accuracy in this region. In two sub-basins with steep terrain and high precipitation, the rain gauge-based evaluation indicated negative or even positive basin-averaged biases of about 1 mm/day or less, but the water budget analysis indicated that all the products had much larger negative biases, of 2.4 ~ 3.8 mm/day. This difference likely arises because the evaluation based on rain gauge data cannot reflect errors in products at the basin-scale, due to the sparse spatial distribution of rain gauges. Finally, observed altitudinal gradients of precipitation were used to correct the precipitation products. Under this approach the water budget can be better closed but is not always satisfactory. Therefore, developing a high-quality precipitation data set for mountainous regions based only on satellite products and sparse ground observations remains challenging and other data sources (e.g. high-resolution meteorological modeling) should be taken into consideration in future.

How to cite: Jiang, Y., Yang, K., Li, X., Zhang, W., Shen, Y., Chen, Y., and Li, X.: Evaluation of precipitation products based on rain gauge data and water budget in a mountainous river basin, Eastern Tibetan Plateau, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6642, https://doi.org/10.5194/egusphere-egu2020-6642, 2020.

Water resources in high mountain karst aquifers are usually characterized by high precipitation than in the surrounding lowlands, with significant recharge and discharge that assure the sustainability of the downstream ecosystems. Consequently, these hydrogeological systems are highly vulnerable to the climate change. The mean transit time (MTT) is a key parameter to describe the behaviour of these hydrologic systems and also to assess their vulnerability.

In high mountain zones, precipitation can be as rainfall and as snowfall. The latter generates snow accumulation that in many cases partially or totally melts in spring and summer, producing small runoffs. In this framework, the karst aquifer recharge show mainly two different mechanisms: (1) diffuse recharge, in which runoff from rainfall and snowmelt enters the epikarst through the whole outcropping area and percolates through low permeability fissured blocks in the way down to the saturated zone, (2) locally concentrated recharge through highly conductive hydrologic features, including different solutional forms (e.g. sinkholes, dolines, etc.), which are generally well-connected to vertical fractures and the drainage network of the aquifer. These recharge mechanisms condition the aquifer response observed at the outlet of the systems at different temporal scales.

This study is conducted in the Paleocene-Eocene karst aquifer of the Ordesa and Monte Perdido National Park (PNOMP) Spain, particularly focussing on the Garcés karst system, whose discharge forms the emblematic Horsetail fall of the National Park. Different karstic forms appear throughout the study zone, including sinkholes, dry and ice caves, dolines and karren fields, thus generating a heterogeneous karstified hydrogeological system.

In this work, the difference on the hydrological response of the fine fissures and the main drainage aquifer network is investigated in terms of the corresponding MTT. To this end, both environmental (d¹⁸O and d¹⁸H in water) and fluorescent dye (uranine, eosine, amino G acid and naphtionate) tracers are used. The former characterize the MTT associated to the diffuse recharge process by means of the seasonal variation of the isotopic content in both precipitation (d_P) and the Garcés spring discharge (d_GW). The dye tracers are used to study the hydrogeological organization of the highly conductive drains and to estimate the corresponding MTTs.

The obtained MTT are 1.3 years and 9 days for the environmental and the fluorescent dye tracers, respectively. These values are not very long and point out the difficulties of the aquifer to bear large interannual recharge fluctuations. Additionally, the difference between the estimated MTT values underlines how the heterogeneities of the unsaturated zone may condition both the hydrogeological system response to recharge and the aquifer vulnerability.

How to cite: Jódar, J., Lambán, L. J., González, A., Martos, S., and Custodio, E.: High mountain karst aquifer vulnerability to climate change and groundwater transit times, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7634, https://doi.org/10.5194/egusphere-egu2020-7634, 2020.

Water resources have a fundamental value for both ecosystems and society. However, changes in climate, population, consumption patterns, land use and urbanization are affecting its quality and future availability. In Andorra, a country located in the middle of the Pyrenees, the confluence of climate change and a socioeconomic model with an important weight of tourism industry based on an intensive use of water could threaten the future sustainability of water resources. 

This paper analyses the water resources of Andorra and its future sustainability using the Water Evaluation And Planning system (WEAP) modelling tool. 

The WEAP-Andorra model presents an initial estimate of the national water demand segregated into the main water consumers of the country (tourism, residential, primary sector and power generation). It explores the future evolution of water resources combining climatic and socioeconomic scenarios such as evolution of the population, tourism, power generation plans and land use patterns.

Results of scenarios show that in general terms and at country scale the impact of climate change will not compromise the future water demand. However, in some locations and in specific periods or seasons it could be some challenges to give response to all the demands and rise tensions about what water uses should be prioritized, especially between tourism and ski resort and resident uses.   

The WEAP model presented in this paper is demonstrated a useful tool to support management, decision-making and the design of policies for sustainable water management and adaptation to climate change.

How to cite: Pesado-Pons, C., Travesset-Baro, O., Zabalza, J., López-Moreno, J. I., and Pons, M.: Sustainability of water resources in Andorra under global change: The effects of climate and socio-economic changes in the future of water resources, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10205, https://doi.org/10.5194/egusphere-egu2020-10205, 2020.

The Pyrenees mountain range is the main source of water resources for a large surrounding region, extending from the Atlantic to the Mediterranean. This area is particularly vulnerable to the consequences of climate change. The PIRAGUA project (Interreg-POCTEFA) evaluates the components of the hydrological cycle in the Pyrenees, with the central objective of improving the adaptation of territories to climate change. One of its tasks focuses on the analysis of the effect that land cover and associated soil properties have on different hydrological services. Indeed, land use and its management directly affect soil hydrology, which is a key factor in streamflow temporal distribution. A better understanding of the water-soil-vegetation system is essential for a reliable hydrological modelling which results should be considered in adaptation strategies to climate change.

To this aim, chemical and physical characterization of soil properties is being conducted at the 681 km² humid Bidasoa catchment (Pyrenees). In order to understand the soil-moisture dynamics, a monitoring network was established in July 2019 in a 0.4 km² experimental site within the catchment. Four soil-moisture stations and a meteorological one were installed within the same geological setting, same rainfall conditions and similar soil texture characteristics (silt-loamy texture and about one meter deep), but different land covers (pine forest, oak forest, grassland and fernery). Continuous soil-moisture data obtained to date show that upper soil layers (0-20 cm) are deeply influenced by top vegetation cover. Grassland has the highest soil-moisture variations, ranging from 16.2 to 36.6 %, as they closely mirror precipitation patterns. Pine and oak forests present similar variation trend, varying from 33.9 to 42.8 % and from 35.3 to 41.9 %, respectively. Soil-moisture at fernery goes from 30.5 to 36 %. Minimum soil-moisture values coincide in all plots with the end of the dry period (end of September). Maximum values, occurring during very heavy and continuous precipitation in November (647 mm registered from 1 to 24 November), are considered as a proxy for saturated soil conditions. In all the plots, fluctuations in soil-moisture diminish significantly with increasing soil depth. However, considerable differences are found in the vertical soil-moisture profile across land covers. In both forest plots, a decreasing trend of soil-moisture within the profile is observed, while grassland and fernery show an increasing trend. Preliminary results show that soil water infiltration is different among different land covers, which give some insight into the hydrological functionality of soil under different vegetation types. Longer records of soil-moisture dynamics in the area would contribute to better assess the linkages between water, soil and vegetation and, in turn, to improve hydrological modelling in humid mountainous areas. This knowledge is necessary for a better consideration of the adaptation measures that should be taken from the territory.

How to cite: Valiente, M., Zabaleta, A., Meaurio, M., Uriarte, J. A., and Antigüedad, I.: Evaluation of land cover effects on soil-moisture dynamics: adaptation measures from the territory (Bidasoa catchment, Western Pyrenees)., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15114, https://doi.org/10.5194/egusphere-egu2020-15114, 2020.

Glaciers in the tropical Andes play an important role for both water supply, economic activities and cultural beliefs. Their importance is particularly high during the dry season (May – September) when glaciers can contribute more than 50% to total streamflow. People are used to take advantage of the important buffering function of the glaciers, but in a climate change context with rapid glacier retreat, this dependence could poses a considerable risk.

Several studies have focused on understanding and simulating the glacio-hydrological patterns for historical and future periods by using different hydrological models with different levels of complexity. However, most existing studies focus on regions with high availability of data, while data scarce regions are studied poorly.

The Vilcanota basin is located in such a data scarce region and encompasses the second largest glaciated mountain range in Peru and the tropics worldwide. As in many other mountainous regions, high-mountain conditions with complex topography and related variations of climatic variables are contrasted with poor availability of data. In view of this challenge, a key question is what level of model complexity would be most appropriate to achieve robust simulations of the hydrological cycle for historical and future climate conditions?

To answer this question, we simulated the hydrological conditions in the Sibinacocha catchment (area: 132 km2; glacier extent: 15 km2) that is part of the upper Vilcanota basin. The simulation was performed with three different hydrological models of different complexity on a monthly time scale from 1981 to 1996. Input data like precipitation and temperature were obtained from the Peruvian gridded precipitation and temperature data set PISCO2.1 (SENAMHI). Streamflow records for calibration were obtained from a hydropower company in the area. Finally, glacier outlines were obtained for three different periods from satellite images in order to incorporate glacier change.

The selected models include a lumped hydrological model based on equations by Temez (6-parameters), and two implementations of the HBV model (HBV Light and RS Minverve with 15 and 14 parameters respectively). Each model is capable of simulating groundwater and glacier contribution. For the simulations with HBV, the catchment was divided into 10 elevation bands. For the simulation with RS Minerve an additional Glacier and Snow model was performed with its own pool of parameters (10-parameters) and own elevation bands. Calibration was performed in two ways: 1) comparing observed and simulated flows, and 2) comparing the simulated and expected glacier and snow contribution to streamflow.

Results show that each of the models examined can reach high efficiencies when using only streamflow records for calibration. By contrast, multicriteria calibration provides more robust results than using one single indicator, even when efficiency indicators are in the same range of values.

In the context of the study region, we found that increasing complexity for hydrological simulation is only feasible if adequate input data are available. In cases with scarce data, lumped or simple semi-distributed models provide robust results. These simulations can be used later to implement more complex models and tools.

How to cite: Munoz, R., Huggel, C., and Viviroli, D.: Comparing simple and complex hydrological models in regions with scarce data: a case study in the upper Vilcanota basin, Peru, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19829, https://doi.org/10.5194/egusphere-egu2020-19829, 2020.

Predictions in ungauged basins still present one of the major challenges in hydrology. In many cases, the absence of a stream gauge also implies a low density of the meteorological monitoring network in these catchments and surroundings as well as little available data on water management infrastructure and agricultural consumptions. This combination creates a circle of uncertainties and thus individual influences of relevant water balance components are difficult to disentangle and quantify. 

The original Budyko curve presents a very general model that yields, to first order, an estimate of the steady-state water balance of a catchment at the climatological scale, assuming its landscape and functioning has evolved naturally and free of anthropogenic interferences. Even at smaller time scales, the Budyko relationship allows approximating the water partitioning in the catchment, and thus helps correct erroneous assumptions[JW1]  or missing information about for instance unknown human-induced alterations. On the other hand, an increasing variety of global remote-sensing data products is becoming available providing spatial estimates of land surface properties such as for instance vegetation indexes or soil moisture. Even if the predictive power of such products in terms of absolute values remains questionable, it is possible to derive coarse spatial patterns or temporal dynamics to narrow down zones and orders of magnitude of interferences with the natural hydrological cycle such as reservoirs or irrigated lands. This study combines these two general approaches in order to improve hydrological modelling and system understanding of the semi-arid Lurín catchment in the Western Andes of Peru.

How to cite: Bondy, J., Zehe, E., and Wienhöfer, J.: Can the Budyko framework and satellite data help improve hydrological modeling in ungauged and poorly monitored catchments? The case study of the Lurín catchment in Peru, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20284, https://doi.org/10.5194/egusphere-egu2020-20284, 2020.

The Xinjiang Uyghur Autonomous Region is the area on Earth which is most remote from any ocean and the annual precipitation is only 50 mm. Water availability for e.g. agriculture, water supply, and hydropower production is limited in this area. The area has ~20 000 glaciers and they are the main source for water resources. However, since the 1950s, the glaciers are continuously retreating by 20-30%, and result reductions runoff in the lower reaches of some rivers. In this study, we use a widely used hydrological model (HBV) with a glacier retreat module to study the impacts of climate change and glacier retreat on water resources. An ensemble of climate projections up to the end of the century will be explored and the WEAP (Water Evaluation And Planning) model system will be used to analyze impacts on the society.

How to cite: Li, H.: Impacts of climate change and glacier retreat on water resources and society in the Xinjiang Uyghur Autonomous Region, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21862, https://doi.org/10.5194/egusphere-egu2020-21862, 2020.

Runoff decrease as was triggered or exacerbated by human activities over the past decades on the Loess Plateau has grown to be a hot spot increasingly drawing nationwide concerns; distinguishing human-induced runoff-altering factors from one another is of great significance to decision-making on maintaining regional water, ecological and economic security. Sediment-trapping dams (STDs) construction and revegetation are the two major soil conservation practices regarded to have also caused runoff reduction, whose hydrologic effects on the basin scale have not been separated quantitatively. Our study, choosing the Huangfuchuan River Basin as the study area and based on analyses of its hydrologic, climatic and underlying condition changes, proposed a physically-based attribution framework which is able to account for the hydrological effects of STDs, revegetation, land use change and climate change simultaneously, and attributed runoff decrease of the basin among factors including climate change, STDs construction, revegetation and land use cover change. The model-based attribution results indicate that STDs construction caused a 45% (48%) runoff reduction from 1976-1988 to 1989-2000 (2001-2014) and revegetation was responsible for a 30% runoff decrease from 1976-1988 to 2001-2014, with daily simulation implying that the hydrologic effect of revegetation to affect flow magnitudes more consistently than that of STDs. Our study demonstrates that STDs construction is the prime contributor to runoff decrease in the study area and suggests that STDs should be taken into account in similar studies on the Loess Plateau in the future.

How to cite: Lu, B., Lei, H., Yang, D., and Fu, X.: Separating the effects of revegetation and sediment-trapping dams construction on runoff decrease in a semi-arid watershed of the Loess Plateau, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21130, https://doi.org/10.5194/egusphere-egu2020-21130, 2020.

Despite their small size, headwater catchments of European mountains are essential because they provide many ecosystem services (water quality, energy, tourism, ecological niches).

Based on the hydrological monitoring of a mountain catchment in the central Pyrenees and the extreme conditions encountered in the past and expected in the future, we present scenarios for the evolution of hydrological regimes that will potentially impact the socio-ecological services by high mountain mires, ponds and lakes. In particular, in view of the exacerbated climate change in the high mountains, the shortening of snow season will potentially impact the ecosystem services by the ponds, modifying the minimum water level and/or ecological flow in late spring and early summer. For example, these ponds play an essential role as ecological refuges compared to larger lakes, which are subject to invasions by non-native organisms. Peat pools also play an essential role in the cycling of chemical elements, including carbon. Their modification, their increased intermittency due to more frequent and intense climatic variability will deeply modify, for example, the export of dissolved organic carbon from peatlands.

While it is difficult to accurately predict the future of mountain watersheds, our study aims to identify the key factors for their current roles in biodiversity, water sustainability and in ecological services as well as to determine their future adaptability to other human pressures such as mini-hydroelectric power plants.

How to cite: Le Roux, G., Haver, M., Rosset, T., Schmeller, D., Gandois, L., Allen, D., Binet, S., Simonneau, A., Grusson, Y., Camboulives, T., Sauvage, S., Galop, D., Gascoin, S., and Sánchez Pérez, J. M.: Small but essential in hydrogeochemical cycles: headwater mountain catchments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20379, https://doi.org/10.5194/egusphere-egu2020-20379, 2020.

Evaluating seasonal and long-term variations in water balance at catchment scale can be useful for assessing the current status and trends in water resources availability. Components of water balance reflect meteorological and climate variability, and vegetation cover development.

The experimental catchment Uhlířská is a small forested headwater catchment in the Jizera Mountains, Czech Republic. The catchment was extensively deforested in the 80´s. Damaged trees long exposed to the effects of air pollutants were poorly resistant to wind and pests. In the 90´s, new spruce forest was planted. The catchment has been subject to long-term monitoring. The 19-year series of data including air temperature, rain and snow precipitation, discharge, groundwater levels, wind velocity, and air humidity, is examined.

Our study provides basic analysis of directly measured components of water balance (precipitation and discharge, annual and seasonal runoff coefficients). The study further deals with the evaluation of the unmeasured components of the water balance (evapotranspiration and water storage). An interception model was employed to calculate the interception loss. Potential evaporation and transpiration during vegetation seasons were estimated by Penman and Penman-Monteith methods. Snow sublimation was estimated in the winter seasons. Effect of the forest development during the period of interest was considered.

The catchment water balance equation suggests significant changes of the water storage over the observation period, implying its decrease in recent years. However, baseflow and deep water storage seem to be unchanged. This discrepancy could be partly attributed to the decrease in shallow water storage and/or more pronounced transpiration reduction in recent vegetation seasons.

The research is supported by the Czech Science Foundation Project No. 20-00788S.

How to cite: Mikesova, V., Dohnal, M., Votrubova, J., and Vogel, T.: Evaluating water balance components for forested headwater catchment undergoing environmental changes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11623, https://doi.org/10.5194/egusphere-egu2020-11623, 2020.