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Water is a strategic issue in the Mediterranean region, mainly because of the scarcity of the available resources, in quantity and/or quality. The Mediterranean climate and the surface hydrology are characterized by a strong variability in time and space and the importance of extreme events, droughts and floods. This irregularity is also met at a lower level in aquifers dynamics. During the last century, modifications of all kinds and intensities have affected surface conditions and water uses. The Mediterranean hydrology is then continuously evolving.

This session intends to identify and analyse the changes in the Mediterranean hydrology, in terms of processes, fluxes, location. It will gather specialists in observation and modeling of the various water fluxes and redistribution processes within the catchments.
Contributions addressing the following topics are welcome:

• Spectacular case studies of rapid changes in water resources;
• Using various sources of information for comparing past and present conditions;
• Differentiating climatic and anthropogenic drivers (including GCM reanalysis);
• Modelling hydrological changes (in surface and/or ground water);
• Impacts of extreme events on water systems.

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Convener: Lionel Jarlan | Co-conveners: Said Khabba, María José Polo, Mehrez Zribi
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| Attendance Mon, 04 May, 08:30–10:15 (CEST)

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Chat time: Monday, 4 May 2020, 08:30–10:15

D94 |
EGU2020-7162
| solicited
| Highlight
Yves Tramblay, Denis Ruelland, Lahoucine Hanich, Zoubeida Bargaoui, and Hammouda Dakhlaoui

Countries in North Africa are facing water scarcity and a high inter-annual variability of precipitation. In this context, many dams have been built to collect surface water and improve the management of existing water resources. We present the main results of a recent MISTRALS-ENVIMED research project about the potential climate change impacts on water resources at the regional and basin scales. The project notably focuses on the uncertainties linked to the different components of the modelling chain required to produce hydrological scenarios. Climate change impacts on surface water resources are investigated using an ensemble of regional climate model simulations from the CORDEX experiment under different emission scenarios and different hydrological models, adapted to the context of data scarcity. Climate scenarios under RCP4.5 and RCP8.5 over North Africa indicate a future decrease in precipitation together with an increase in temperature that could have significant impacts on water resources. Indeed, a future decrease of surface water availability is expected in all major dam catchments, with a stronger decline over Morocco.

How to cite: Tramblay, Y., Ruelland, D., Hanich, L., Bargaoui, Z., and Dakhlaoui, H.: Climate change impacts on water resources in North African basins , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7162, https://doi.org/10.5194/egusphere-egu2020-7162, 2020

D95 |
EGU2020-13806
| Highlight
Lila Collet, Thibault Lemaitre-Basset, Guillaume Thirel, Juraj Parajka, Guillaume Evin, and Benoît Hingray

The Mediterranean region is a hot spot for climate change impact on the water cycle where water resources are anticipated to decrease and hydrological extremes to intensify while population and water use conflicts growth would keep rising. However, the analysis of the uncertainty related to hydrological projections is generally poorly quantified and difficult to translate to decision-makers. In this study, an in-depth analysis of projections and uncertainties for extreme high- and low-flows was performed. Climatic projections derived from a recent downscaling method over France (Adamont, Verfaillie et al., 2017) were used, and hydrological projections were produced on the Hérault River catchment based on two different Radiative Concentration Pathways (RCPs), five global and regional climate model (GCM/RCM) couples, three hydrological models (HMs), and twenty-nine calibration schemes (Lemaitre-Basset et al., sub). This ensemble was analysed with the QUALYPSO approach (Evin et al., 2019) that allows transient uncertainty analysis of ensembles derived from incomplete GCM/RCM matrix. The quasi-ergodic analysis of variance (QE-ANOVA) used in QUALYPSO evaluates the contribution of each impact modelling step to the total uncertainty. For high-flows, GCMs and RCPs contribute the most to the total uncertainty at the short and long lead-time, respectively. For low-flows, HMs structure and calibration period are the most important sources of uncertainty across 2006-2100. While high-flow projections show a significant mean increase of 30% by 2085 compared to the historical period (confidence intervals: [-1%; +64%]), low-flows would slightly decrease (-7%) by 2085, but with a higher uncertainty (confidence interval: [-24%; +13%]). The time horizons for which a change (e.g. -50, -20, -10, …, +10, +20, +50%) in high- and low-flows intensity becomes robust (i.e. when more than 66% of the ensemble is above/below a given threshold) were also assessed. This provides strong messages to water managers of the Hérault River catchment who can then anticipate the time needed to prepare and adapt to climate change impacts for extreme hydrological hazards.

References:

Evin, G., Hingray, B., Blanchet, J., Eckert, N., Morin, S., & Verfaillie, D. (2019). Partitioning Uncertainty Components of an Incomplete Ensemble of Climate Projections Using Data Augmentation. JOURNAL OF CLIMATE, 32, 18. https://doi.org/10.1175/JCLI-D-18-0606.1

Lemaitre-Basset, T., Collet, L., Thirel, G., Parajka, J., Evin, G., Hingray, B. (submitted) Climate change impact and uncertainty analysis on hydrological extremes in a Mediterranean catchment. Hydrological Sciences Journal

Verfaillie, D., Déqué, M., Morin, S., & Lafaysse, M. (2017). The method ADAMONT v1.0 for statistical adjustment of climate projections applicable to energy balance land surface models. Geoscientific Model Development, 10(11), 4257–4283. https://doi.org/10.5194/gmd-10-4257-2017

How to cite: Collet, L., Lemaitre-Basset, T., Thirel, G., Parajka, J., Evin, G., and Hingray, B.: Future changes in hydrological extremes of a Mediterranean catchment: what can we say in an uncertainty context?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13806, https://doi.org/10.5194/egusphere-egu2020-13806, 2020

D96 |
EGU2020-9267
Houssne Bouimouass, Younes Fakir, Sarah Tweed, and Marc Leblanc

Mountain-fronts constitute important groundwater recharge areas in arid and semiarid regions. Mountain-front recharge processes are generally identified, in natural systems, as streamflow losses and subsurface inflow from the mountain block. However, another key recharge process is from irrigation practices; where mountain streamflow is distributed across the irrigated piedmont. In this study, coupled groundwater fluctuation measurements and stable isotopes (18O and 2H) were used to identify and compare the natural mountain-front recharge to the anthropogenically-induced irrigation recharge. Within the High-Atlas mountain front of the Ourika basin, Tensift, Central Morocco, the groundwater fluctuation mapping from the dry to wet season showed that recharge from irrigation waters was higher than the recharge along the streambed. Irrigation practices in the region divert more than 65% of the stream water, thereby reducing the potential for stream recharge. Due to the traditional irrigation practices, upstream crops are preferentially irrigated with stream water over downstream areas. In downstream areas irrigation is only via stream water during large flood events and is otherwise supplemented by groundwater resources. These changes in water resources used for irrigation practices between upstream and downstream areas are reflected in the spatio-temporal evolution of the stable isotopes of groundwater. In the upstream irrigation area, the groundwater stable isotope values (d18O: -8.4 ‰ to -7.4 ‰) reflect recharge by the diverted stream water. In the downstream irrigation area, the groundwater isotope values are lower (d18O: -8.1 ‰ to -8.4 ‰) due to recharge with floods.

The results from this study particularly highlight that irrigation can deeply modify both the recharge processes and the water balance in the mountain front areas. Groundwater resources in such areas become reliant on the irrigation practices as an important source of recharge, and this anthropogenic modification of the hydrological cycle should be assessed and taken into consideration within climate change impacts and integrated water management strategies.

How to cite: Bouimouass, H., Fakir, Y., Tweed, S., and Leblanc, M.: Anthropogenically-induced recharge in a semiarid mountain front context, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9267, https://doi.org/10.5194/egusphere-egu2020-9267, 2020

D97 |
EGU2020-6957
| Highlight
Serena Sirigu, Roberto Corona, Nicola Montaldo, Ram Oren, and Dora Soru

Over the past century, climate change has been reflected in altered precipitation regimes worldwide.  Recently, Montaldo and Sarigu (2017) showed that Sardinia runoff decreased over the 1975-2010 period, with mean annual values 40% lower than the 1922-1974 period.

These trends will have dramatic consequences on basin water resources, therefore forests are frequently exposed to periods characterized by a reduced water availability that influences the evapotranspiration process (ET), the water use efficiency and could be also the main cause of tree mortality or change of tree spatial distribution and density.

The Marganai forest, located in South West Sardinia (Italy), is a Long-Term Ecosystem Research (LTER) Italian site and a European Site of Community Importance (Natura 2000) managed by FORESTAS. The vegetation is mainly composed by Quercus Ilex trees and the soil depth varies between 10 cm and 50 cm. Historical data are from 16 rain stations (1922-2018 period) over the entire area and data of runoff of the Fluminimaggiore basin (area of 83 km2) are available. From 1922 a persistent decrease trend of winter precipitation in that area (Mann-Kendall t of -0.26) impacted runoff, which decreased of 2.52 mm/y.

Future climate scenarios are selected from IPCC climate change scenarios. From the 12 Atmosphere-Ocean General Circulation Models (AOGCMs) of Flato et al. (2013), we selected theHadGEM2-AO that simulates reasonable approximation of observed past seasonal precipitation and air temperature changes (1976-2004 compared with 1951-1975) in Sardinia.Using a distributed ecohydrologic model and the HADGEM2-AO future climate (rainfall and air temperature ) scenarios we predict both hydrologic (soil moisture, runoff, ET) and vegetation dynamic (CO2, biomass, leaf area index and vegetation fraction) outputs.

The model has been successfully calibrated for runoff and ET estimation for the 1922 – 2018 period. Then, the eco-hydrological model, forced with the generated future scenarios, predict a significant change on tree leaf area index, with the reduction of tree density, spatial distribution, forest productivity and runoff. Future scenario predicting further decline is particularly alarming for the Marganai forest, requiring new strategies in both forestal and water resources planning and management.

How to cite: Sirigu, S., Corona, R., Montaldo, N., Oren, R., and Soru, D.: The impact of climate change decrease of winter precipitation on the water use efficiency and sustainability of a Mediterranean forest., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6957, https://doi.org/10.5194/egusphere-egu2020-6957, 2020

D98 |
EGU2020-13665
Jérôme Molénat, Damien Raclot, Rim Zitouna, Jean Albergel, and Marc Voltz and the OMERE Team

The hydrology of the Mediterranean region is affected by global changes such as climate and land use changes. In rural areas, changes in farming practices and landscape management can be the main drivers of changes in water cycles and in matter transport associated with hydrological fluxes, such as contaminants and sediments. The process underlying these changes can be slow, such as in land use or contaminant dynamics, or infrequent over time, such as erosion. Understanding these processes and their relationship requires long-term observations to capture slow dynamics or infrequent events. In this context, we present the Mediterranean agro-hydrological observatory OMERE (Mediterranean observatory of the rural environment and water) by explaining the observation strategy and by emphasizing how this strategy and associated research have contributed to a better understanding of the impact of agricultural and land management on mass flows in Mediterranean farmed headwater catchments.

The OMERE observatory is made up of two agricultural catchments, one in the north of Tunisia and the other in the south of France, accounting for for the diversity of agricultural and ecosystem situations in hilly Mediterranean areas. The OMERE observatory belongs to the French national network OZCAR, dedicated to the observation of the critical zone. The observation strategy is motivated by monitoring the flow of water, sediments and contaminants and hydrological and climatic variables at different spatial scales from cultivated plots and landscape elements to the catchment scale. These measurements were made with fine temporal resolution on a long-term scale and examining land use, agricultural practices and soil surface characteristics. The long-term observation strategy aims to support multidisciplinary integrative research to elucidate the conditions that improve soil and water management and the provision of ecosystem services in the Mediterranean context of rain-fed agriculture. The observatory addressed three scientific questions: (i) better understand water flows, erosion and contaminants, in particular pesticides, and their natural and anthropogenic factors in the short and long term; (ii) analyze the overall effects of agriculture and land management on mass flows at different scales, from the plot to the watershed or the landscape; and (iii) develop new scenarios for sustainable agricultural management and better delivery of ecosystem services. Some of the scientific progresses driven by the questions drawn from the OMERE observatory are presented.

Voltz, M., and A. Albergel. 2002. OMERE: Observatoire Méditerranéen de l’Environnement Rural et de l’Eau- Impact des actions anthropiques sur les transferts de masse dans les hydrosystèmes méditerranéens ruraux. Proposition d’Observatoire de Recherche en Environnement. Minist. Français Rech., Paris

Molénat, J., Raclot, D., Zitouna R., ...., Albergel, J., and Voltz M., 2018, OMERE: A Long-Term Observatory of Soil and Water Resources, in Interaction with Agricultural and Land Management in Mediterranean Hilly Catchments, Vadose Zone J., 17:180086. doi:10.2136/vzj2018.04.0086

How to cite: Molénat, J., Raclot, D., Zitouna, R., Albergel, J., and Voltz, M. and the OMERE Team: OMERE: A Long-Term Observatory of Soil and Water Resources, in Interaction with Agricultural and Land Management in Mediterranean Hilly Catchments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13665, https://doi.org/10.5194/egusphere-egu2020-13665, 2020

D99 |
EGU2020-3100
Simonetta Paloscia, Giacomo Fontanelli, Simone Pettinato, Emanuele Santi, Giuliano Ramat, Emmanuel Da Ponte, Magdy Abdel-Wahab, Yassmina Hesham, Mohamed Ouessar, Hanen Dhaou, Zeineb Kassouk, and Zohra Lili Chabane

This project deals with the implementation of an innovative water management system in Mediterranean countries (i.e. Tunisia and Egypt), which suffer from chronic water scarcity, together with two European countries (Germany and Italy). The consortium is developing and applying synergic methods and algorithms for investigating the water cycle, using remote sensing techniques.

The focus is on the use of satellite data (both optical and microwave) for monitoring vegetation cover and water status along with soil moisture temporal evolutions in order to improve the knowledge of the water cycle in arid areas. Both local and regional monitoring are carried out in order to investigate different spatial scales.

Environmental models and algorithms for the retrieval of hydrological parameters have been developed in the frame of this project in order to match the main goal of the project, i.e. to propose practical and cost-effective solutions for driving and updating a method for the sustainable use of water in agriculture. 

An optimized management of water resources for cultivated lands on Egyptian Delta (Northern part) and Tunisian territory will be realized by analyzing the available spatial and temporal data for the areas of interest appropriately selected for this purpose. As such, an efficient water use, equitable distribution of water resources, community participation in decisions, and sustainable system operation over time can be supported.

First of all, we aim to localize different crop and irrigation techniques for the study regions. This information is required as a basis for further investigations and assessments. Secondly, the water efficiency for different lands, crop types and irrigation systems will be assessed.

Afterwards, possible improvements in agricultural practice with respect to climate change scenarios and information on water efficiency will be determined by rating the outcome from the assessment.

How to cite: Paloscia, S., Fontanelli, G., Pettinato, S., Santi, E., Ramat, G., Da Ponte, E., Abdel-Wahab, M., Hesham, Y., Ouessar, M., Dhaou, H., Kassouk, Z., and Chabane, Z. L.: Water management and climate change monitoring in Tunisia and Egypt using remote sensing techniques, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3100, https://doi.org/10.5194/egusphere-egu2020-3100, 2020

D100 |
EGU2020-7408
Nadia Ouaadi, Lionel Jarlan, Jamal Ezzahar, Saïd Khabba, Mehrez Zribi, Elhoussaine Bouras, Safa Bousbih, and Pierre-Louis Frison

High spatial and temporal resolution products of Sentinel-1 are used for surface soil moisture (SSM) mapping over wheat fields in semi-arid areas. Within these regions, monitoring the water-use is a critical aspect for optimizing the management of the limited water resources via irrigation monitoring. SSM is one of the principal quantities affecting microwave remote sensing. This sensitivity has been exploited to estimate SSM from radar data, which has the advantages of providing data independent of illumination and weather conditions. In addition, with the use of Sentinel-1 products, the spatial and temporal resolution is greatly improved. Within this context, the main objective of this work is estimate SSM over wheat fields using an approach based on the use of C-band Sentinel-1 radar data only. Over the study site, field measurement are collected during 2016-2017 and 2017-2018 growing seasons over two fields of winter wheat with drip irrigation located in the Haouz plain in the center of Morocco. Data of other sites in Morocco and Tunisia are taken for validation purposes. The validation database contains a total number of 20 plots divided between irrigated and rainfed wheat plots. Two different information extracted from Sentinel-1 products are used: the backscattering coefficient and the interferometric coherence. A total number of 408 GRD and 419 SLC images were processed for computing the backscattering coefficient and the interferometric coherence, respectively. The analysis of Sentinel-1 time series over the study site show that coherence is sensitive to the development of wheat, while the backscatter coefficient is widely linked to changes in surface soil moisture. Later on, the Water Cloud Model coupled with the Oh et al, 1992 model were used for better understand the backscattering mechanism of wheat canopies. The coupled model is calibrated and validated over the study site and it proved to goodly enough reproduce the Sentinel-1 backscatter with RMSE ranging from 1.5 to 2.52 dB for VV and VH using biomass as a descriptor of wheat. On the other side, the analysis show that coherence is well correlated to biomass. Thus, the calibrated model is used in an inversion algorithm to retrieve SSM using the Sentinel-1 backscatter and coherence as inputs. The results of inversion show that the proposed new approach is able to retrieve the surface soil moisture at 35.2° for VV, with R=0.82, RMSE=0.05m3/m3 and no bias. Using the validation database of Morocco and Tunisia, R is always greater than 0.7 and RMSE and bias are less than 0.008 m3/m3 and 0.03 m3/m3, respectively even that the incidence angle is higher (40°). In order to assess its quality, the approach is compared to four SSM retrieval methods that use radar and optical data in empirical and semi-empirical approaches. Results indicate that the proposed approach shows an improvement of SSM retrieval between 17% and 42% compared to other methods. Finally, the validated new approach is used for SSM mapping, with a spatial resolution of 10*10 m, over irrigated perimeters of wheat in Morocco.

How to cite: Ouaadi, N., Jarlan, L., Ezzahar, J., Khabba, S., Zribi, M., Bouras, E., Bousbih, S., and Frison, P.-L.: Mapping surface soil moisture over wheat crops in southern Mediterranean regions using the backscattering coefficient and the interferometric coherence derived from Sentinel-1, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7408, https://doi.org/10.5194/egusphere-egu2020-7408, 2020

D101 |
EGU2020-6876
Said Khabba, Jihad Toumi, Salah Er-Raki, Jamal Ezzahar, Michel Le Page, Abdelghani Chehbouni, and Lionel Jarlan

In this study, we developed a simple and spatialized wheat yield method based on the Monteith's three efficiency model. The originality of the method consists in: (1) the expression of the conversion coefficient (εconv) by considering an appropriate stress threshold (ksconv) for triggering irrigation, (2) the substitution of the product of the two maximum coefficients of interception (εimax) and conversion (εconv_max) by a single parameter εmax, (3) the modeling of εmax as a function of the Cumulative Growing Degree Days (CGDD) since sowing date, and (4) the dynamic expression of the harvest index HI as a function of the CGDD and the final harvest index HI0 depending of the maximum values of the Normalized Difference Vegetation Index (NDVI).

The calibration and validation of the proposed model were performed by using observed dry matter (DM) and grain yield (GY) on wheat conducted on the irrigated zone R3 of the Haouz plain (center of Morocco), during three agricultural seasons 2002/2003, 2008/2009 and 2012/2013. The model calibration allowed the parameterization of εmax in four periods according to the wheat phenological stages. By contrast, a linear evolution was sufficient to represent the relationship between HI and CGDD. The model validation was performed at the field and regional scales. For the field scale, the obtained results showed a good agreement between the estimated and observed values of DM and GY with Root Mean Square Error (RMSE) of about 1.07 t/ha and 0.57 t/ha for DM and GY, respectively. Likewise, at the regional scale, the proposed approach was tested over the irrigated district (R3) by using Landsat/spot images for mapping GY and DM. The RMSE values were 1.21 t/ha and 0.34 t/ha between measured and simulated DM and GY, respectively.

How to cite: Khabba, S., Toumi, J., Er-Raki, S., Ezzahar, J., Le Page, M., Chehbouni, A., and Jarlan, L.: Simple and spatialize approach to optimize irrigation water and wheat yield in the semi-arid areas, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6876, https://doi.org/10.5194/egusphere-egu2020-6876, 2020

D102 |
EGU2020-2405
María Herminia Pesci, Fenja Voges, Nils Rüther, and Kristian Förster

The need for effective water resources management has turned into a major challenge, especially in the face of climate change. Meteorological data is not always readily available and thus the task of predicting the response of hydrological systems becomes complicated. For this reason, climate reanalysis datasets are used as a viable alternative. They combine models with data from satellites and ground sensors and provide consistent long-term meteorological conditions with high temporal resolution. The ERA5 reanalysis dataset was produced and is continuously updated by the European Centre for Medium-Range Weather Forecasts (ECMWF). Within this framework, the ERA5 reanalysis dataset has been applied to predict the hydrological response of the Devoll River catchment in Albania. Due to its location, Albania belongs to the Mediterranean climatic belt, which is characterized by hot dry summers and mild rainy winters. The Devoll River catchment is situated south from the capital city Tirana and covers a surface of around 3140 km2. The flow regime of this catchment consists mainly of snowmelt in the upstream mountainous part, whereas precipitation dominates the lower regions. The simulation of the different flow components was carried out with the latest version of the Water Balance and Simulation Model (WaSiM) on a daily time step. The performance of the simulation was evaluated with the Nash-Sutcliffe (NSE) and the Kling-Gupta (KGE) efficiencies, yielding values of 0.66 and 0.80, respectively. Although the model performance suggests some deficiencies, it is considered satisfactory given that ERA5 is a reanalysis dataset with modelled precipitation fields. From the resulting hydrographs, it is possible to infer that observed and simulated runoff follow the same dynamics and a close correspondence between flow peaks can be achieved. These results finally reinforce the idea of applying ERA5 datasets in cases where meteorological input data availability is low or even absent.

How to cite: Pesci, M. H., Voges, F., Rüther, N., and Förster, K.: A first look at ERA5 for physically based water balance modelling of the Devoll Catchment, Albania, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2405, https://doi.org/10.5194/egusphere-egu2020-2405, 2020

D103 |
EGU2020-10631
| Highlight
Vincent Simonneaux, Paul Baby, and Mohamed Hakim Kharrou

Land Cover is a major variable required for agricultural management and biophysical modelling. Remote sensing is the more efficient manner to map this information although robust method are still hardly available especially in semi-arid areas where the development of crops is very heterogeneous, where crops often have low vegetation coverage (e.g. tree plantations) and where several crops are sometimes associated on the same plot (e.g. trees with understory of annuals). Besides, the major problem of classical land cover classification approaches is that they require ground data every year for calibration.

To solve both land cover complexity and ground data availability problems, we propose decision tree approaches based on phenological criteria assumed to remain true for any year. The present work was achieved in the Haouz plain (Marrakech, Morocco) where land cover belongs to six main classes, namely: bare soil, evergreen trees (olive and citrus), deciduous trees (apricot, apple, pomegranate…), winter crops (wheat), summer crops (melon and watermelons), fall crops (peas and broadbean). A decision tree is build based on phonological criteria supposed to be independent of the year, related either to the dynamic of NDVI (min, max and range of NDVI as compared to thresholds) and the period in which the peak or the minimum of NDVI happen (linked respectively to the max of vegetation of annual crops and to the leave fall for trees). This decision tree was applied to map the irrigated areas in the Haouz plain between 1984 and 2018 at yearly time scale using the Landsat archive downloaded from USGS. Only five years with not enough clear images were discarded. The time series obtained are consistent with the known changes that took place in the Haouz plain since 1984, namely a strong development of tree plantations, and of summer crops in some areas. The advantage of processing each year instead of only some key dates (e.g. 3 or 4 images as often encountered in studies when Landsat archive was not so easily available as now) is that it gives a better idea of uncertainties and provides a more robust trend. This work will be continued with estimates of the irrigation water consumption linked with these land cover changes.

How to cite: Simonneaux, V., Baby, P., and Kharrou, M. H.: Yearly land cover mapping between 1984 and 2018 in the Haouz plain (Marrakech, Morocco) using robust decision trees approaches., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10631, https://doi.org/10.5194/egusphere-egu2020-10631, 2020

D104 |
EGU2020-8635
Nafia El-alaouy, Aicha Moumni, Badr-eddine Sebbar, Abdeljalil Gouzrou, and Aberrahman Lahrouni

Due to its arid to semi-arid climate, Morocco often faces significant intense rainfall periods that can generate flash floods and raging torrents causing serious damage in a very short period of time. In this context, these recent years, the watershed corresponding to the SAKIA EL HAMRA wadi has known devastating downpours and excessive heavy rains that caused severe floods in Laayoune city and its regions.

The watershed of Sakia El Hamra covers an area of 82000 km2, that drains to Sakia El Hamra wadi, a stream of about 447 km long, crosses the basin in its northern part in the East-to-West direction, to discharge into the Atlantic Ocean at the outlet called Foum El Oued. This zone often experiences dangerous torrents of water and violent flash floods, specifically in the northern part of Laayoune city. For example, a flash flood has occurred at the end of October 2016. The peak flow was far in excess of the average (3000 m3/s against 410m3/s). This river flood, lasted for about 10 h, caused damage to the infrastructure and destruction of agricultural lands near Foum El Oued.

The objective of this study is to investigate, through modelling, the hydrological regime of SAKIA EL HAMRA watershed to prevent the floods in the future and improve warning systems. The hydrological parameters of the watershed were determined by WMS software, namely: zone extent, perimeter, slope, basin’s average elevation, Gravelius compactness index, Horton shape index, average altitude, drainage density and concentration time.

Flood flow return was simulated using the Log-normal distribution, using a long time-series of flow and maximum daily and annual precipitation data, recorded between 1985 and 2016, at the Airport station in Laayoune city. The results showed that during flash floods with known flows, water level can reach up to 13 meters, with high flow velocities flooding hundreds of hectares of surrounding plains at the northern part of the city of Laayoune and agricultural lands near Foum El Oued.

How to cite: El-alaouy, N., Moumni, A., Sebbar, B., Gouzrou, A., and Lahrouni, A.: Surface Water Management and Modelling in the Sakia El Hamra Hydraulic Basin (Southern Morocco), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8635, https://doi.org/10.5194/egusphere-egu2020-8635, 2020

D105 |
EGU2020-7458
| Highlight
Bouras EL houssaine, Jarlan Lionel, Khabba Said, Er-Raki Salah, Dezetter Alain, Sghir Fathallah, and Yves Tramblay

The southern Mediterranean regions are likely to face drastic climate changes (CC). Agricultural yields, particularly of cereals, could be severely affected, especially if significant changes occur at the key phenological stages. In addition, while agriculture is expected to meet around 83% of North African food demand by 2050, the increase in agricultural water requirements due to the intensification of practices, the extension of arable land and the expected warming could jeopardize the water supply of other key economic sectors. In this context, the present work aims to quantify the impact of CC on the grain yields of irrigated cereals and their water requirements in the Tensift-Haouz region of Morocco. The Med-CORDEX ensemble runs under scenarios RCP4.5 and RCP8.5 are first evaluated and disaggregated using the quantile-quantile approach. The impact of CC on the duration of the main wheat phenological stages based on the degree-day approach is then analysed by considering three typical sowing dates (early, around November 15th; intermediate, around December 15th; and late, around January, 15th). The results show that the rise in air temperature causes a shortening of the development cycle of up to 50 days (around 30%). The impacts of rising temperature, increasing atmospheric CO2 concentration and changes in precipitation on wheat yields are next evaluated, based on the AquaCrop model (previously calibrated on several plots of winter wheat in the region of study), both with and without taking into account the fertilizing effect of CO2. As expected, optimal wheat yields for all climate scenarios and time horizons will decrease on the order of 7 to 30% depending on the sowing date, if CO2 concentration rise is not considered. The results also show that the fertilizing effect of CO2 can counterbalance yield losses, since optimal yields could increase by 7% and 13% respectively at mid-century for the RCP4.5 and RCP8.5 scenarios. Finally, water requirements are expected to decrease by 13 to 42% depending on sowing date, scenario and horizon, mainly in response to the shortening of the cycle. This decrease is associated with a change in temporal patterns, with the requirement peak coming two months earlier than under current conditions. This study provides some quantitative elements for agricultural practices adaptation, in particular concerning the sowing date and also for water management in the south mediterranean region related to the temporal patterns of the crop water needs

How to cite: EL houssaine, B., Lionel, J., Said, K., Salah, E.-R., Alain, D., Fathallah, S., and Tramblay, Y.: Agriculture in Southern Mediterranean areas under climate change: Impacts on irrigated wheat grain yield and irrigation requirements , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7458, https://doi.org/10.5194/egusphere-egu2020-7458, 2020

D106 |
EGU2020-21910
Ahmed Moucha, Lahoucine Hanich, Simon Gascoin, and Lionel Jarlan

The spatialization of meteorological variables when the ground network is scattered and the relief is disturbed is a major issue for watershed hydrology or for the characterization of agricultural water consumption. The aim of this study is to set up the SAFRAN re-analysis system on the Tensift catchment area in Morocco. To this end, all the meteorological measurements acquired on the site between 2004 and 2014 by several organisations were gathered in a single database and quality control was carried out.  SAFRAN was then assessed according to a leave-one-out approach, which consists of removing a station from the database and comparing the re-analysis with the data from this station. It was also compared to another technic for meteorological variables spatialization named MICROMET (Liston et al., 2006). Particular attention was paid on the mountainous areas. In order to reproduce the high climate variability in this area, SAFRAN is also set up with an irregular grid up to 1 km resolution and compared to the regular version (8 km grid point). The results show that the re-analysis on the irregular grid is much better than on the regular grid, especially in the mountains. For example, the validation at the Aremd mountain station (2058 m) shows that the bias and RMSE on the surface temperature decreased from -4.8°C and 6.2°C for the regular grid to 0.6°C and 3.6°C for the irregular grid. Likewise, for precipitation, the correlation coefficient is improved by more than 23% for the regular grid. Concerning the visible radiation, MICROMET is strongly biased compared to the measurements carried out at the Aremd station (86 W/m²) whereas for SAFRAN, the bias is only 48W/m². Our current work concerns the mapping of vertical soil-vegetation-atmosphere exchanges over the catchment area using SAFRAN forcing on the irregular grid. The challenge is notably to represent irrigation, which strongly modifies the surface water states.

How to cite: Moucha, A., Hanich, L., Gascoin, S., and Jarlan, L.: Spatialization of meteorological variables over south mediterranean catchments. Case of the Tensift (Morocco)., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21910, https://doi.org/10.5194/egusphere-egu2020-21910, 2020

D107 |
EGU2020-17787
Isabel Knerr, Katja Trachte, Emilie Garel, Frédéric Huneau, Sébastien Santoni, and Jörg Bendix

The precipitation formation on Corsica in the western Mediterranean is highly affected by the interplay between large-scale weather patterns and the local-scale induced sea-slope breezes. Due to its geographical position the island experiences a strong seasonal cycle in the climatic conditions. From September to May, most of the precipitation is generated by large-scale weather systems, which cause frontal precipitation and in mountainous regions an orographically-induced enhancement. In contrast during the summer month the local combined sea slope breeze systems lead to rather convective precipitation events in the afternoon. The planetary boundary layer (PBL) is the surface affected atmosphere and follows in its structure and height the diurnal cycle. Its height gives information on the strength of turbulent mixing and thus, on the vertical moisture distribution.

In this study we investigate the moisture transport within and above the PBL along a west-east transect on Corsica in the period May 2017 to October 2019. PBL height was derived from wind field measurements with a 3D ultrasound anemometer at the western (Ajaccio) and eastern (Ghisonaccia) coastal sites and from sounding profiles at Ajaccio airport. In addition, the ERA5 reanalysis data along the west-east transect were used to derive the influence of the terrain on the depth of the mixed layer. In order to get further insight into the underlying processes and local mechanisms related to the PBL height development and moisture transport towards the mountains of Corsica the Weather Research and Forecasting (WRF) model is applied. Case studies of summertime convective precipitation formation related to large-scale weather types and local breezes also driven by the sea surface temperatures are presented. Finally, back-trajectory modeling is used to reflect atmospheric pathways and sources of precipitable water.

How to cite: Knerr, I., Trachte, K., Garel, E., Huneau, F., Santoni, S., and Bendix, J.: The influence of large-scale circulation patterns and boundary layer conditions on precipitation formation in Corsica, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17787, https://doi.org/10.5194/egusphere-egu2020-17787, 2020

D108 |
EGU2020-21054
Patricio Yeste, Juan José Rosa-Cánovas, Emilio Romero-Jiménez, Matilde García-Valdecasas-Ojeda, Sonia Raquel Gámiz-Fortis, Yolanda Castro-Díez, and María Jesús Esteban-Parra

Climate change has lead to a generalized decrease of precipitation and an increase of temperature in the Iberian Peninsula during the last decades. These changes will be more intense over the course of the 21th century according to global climate projections. As a consequence, water resources are expected to decrease, particularly in the Duero River Basin.

This study is focused on the hydrological response of the Duero River Basin to the climate change. For this end, firstly, the implementation of the Variable Infiltration Capacity (VIC) model in this Basin has been carried out. The VIC model has been calibrated for the period 2000-2009 with a dataset of daily precipitation, temperature and streamflow. Precipitation and temperature data are extracted from SPREAD/STEAD, a dataset that covers the Peninsular Spain at 0.05º of spatial resolution. Streamflow data are provided by the Spanish Center for Public Work Experimentation and Study (CEDEX, Centro de Estudios y Experimentación de ObrasPúblicas). Subsequently, the VIC model has been validated for the period 2009-2011in order to verify that the model outputs fit well with the observational data.

After the validation of the VIC model for present climate, secondly, the impacts of climate change in the Duero River Basin have been analyzed by developing several future simulations using an ensemble of 18 members from the Euro-CORDEX database and three study periods: 1975-2005 as the historical period; 2020-2050 as the short-term future period, and 2070-2100 as the long-term future period. The Euro-CORDEX simulations for the two future periods are driven under two different Representative Concentration Pathway (RCP) scenarios, RCP 4.5 and RCP 8.5.

The first results of this work show that the VIC model outputs are in good agreement with the observed streamflow, for both the calibration and validation periods. In the context of climate change, a generalized decrease of the streamflow is expected in the Duero River Basin. The results from this study could be of interest for water policy makers and practitioners in the next decades.

Keywords: Duero River Basin, VIC model, climate change, streamflow, projections.

ACKNOWLEDGEMENTS: All the simulations were conducted in the ALHAMBRA cluster (http://alhambra.ugr.es/) of the University of Granada. This work was partially funded by the Spanish Ministry of Economy and Competitiveness projects CGL2013-48539-R and CGL2017-89836-390-R, with additional support from the European Community Funds (FEDER). The first author was supported by the Ministry of Education, Culture and Sport of Spain (FPU grant FPU17/02098).

How to cite: Yeste, P., Rosa-Cánovas, J. J., Romero-Jiménez, E., García-Valdecasas-Ojeda, M., Gámiz-Fortis, S. R., Castro-Díez, Y., and Esteban-Parra, M. J.: Streamflow Changes in the Duero River Basin using an Ensemble of Euro-CORDEX Projections, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21054, https://doi.org/10.5194/egusphere-egu2020-21054, 2020

D109 |
EGU2020-9332
Safa Bousbih, Mehrez Zribi, Zohra Lili-Chabaane, Nicolas Baghdadi, Azza Gorrab, and Nadhira Ben Aissa

Soil texture is a key parameter in agricultural processes and an important measure for agricultural prediction, water cycle, filtering of pollutants and carbon storage. Besides, its estimation is essential for agronomists, hydrologists, geologists and environmentalists and for modeling in these application areas. Several studies have been based on understanding and modeling the biological, physical and chemical processes in the soil. Regarding the texture of the soil, few researches propose soil texture spatialization, and are generally based on ground measurements. Among other things, field observations or laboratory analyzes are very expensive and are not very representative. Indeed, the soil texture presents a strong heterogeneity even at the scale of a field. It is then necessary to use precise and spatialized information on soils.

These methods are generally based on remote sensing data and particularly optical data to restore soil component. However, these techniques are strongly affected by atmospheric conditions. This constraint is not valid for Radar sensors (Radio Detection And Ranging). Radar data are mainly sensitive to soil moisture and soil roughness, and has also been evaluated for its ability to perform texture measurements.

The aim of this study is evaluate the potential of these techniques based on optical and radar data for soil texture estimation. By its composition, its structure, its texture and its porosity, soil moisture is strongly influenced by the soil nature. With the arrival of Sentinel-1 (S-1) and Sentinel-2 (S-2) ESA spatial missions, data are acquired with high spatial and temporal resolution between July and early December 2017, on a semi-arid area in central Tunisia. This study is therefore conducted using S-2 SWIR (Short-Wave Infrared) bands (B11 and B12, most sensitive to clay) and soil moisture products derived from radar data. And algorithms based on the support vector machine (SVM) and random forest (RF) methods are proposed for the classification and mapping of clay content.

In order to evaluate the approach and determine the adequate data (between optical and radar data) allowing to precisely characterize the clay content, a cross-validation was used. The SWIR bands lead to less satisfactory outcomes compared to soil moisture. With an overall accuracy of approximately 65%, soil moisture achieved the best performance for estimating soil texture. The results also showed that RF and SVM are robust classifiers for texture estimation despite the small number of training data. However, RF displays greater accuracy and speed of simulation compared to SVM.

How to cite: Bousbih, S., Zribi, M., Lili-Chabaane, Z., Baghdadi, N., Gorrab, A., and Ben Aissa, N.: Evaluation of the potential of Sentinel-1 and Sentinel-1 data for clay content mapping, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9332, https://doi.org/10.5194/egusphere-egu2020-9332, 2020

D110 |
EGU2020-9914
Flavia Fuso, Chiara Righetti, Maurizio Gorla, Oliva Desdemona, and Daniele Bocchiola

We present preliminary results in fulfilment of a Gruppo CAP funded project aiming to evaluate the contribution of the Ticino-Adda TA catchment surface runoff to aquifer recharge of the Lombardia region of Italy. The area of interest is nested within the Po river valley, largely snow/ice fed, and rich in both surface and underground waters, and management of groundwater resources requires thereby assessment of water exchanges between surface and subsurface bodies. Final purpose of this 3-year effort is the production of weather based (IPCC AR5/6) hydrological scenarios in the TA catchment, as boundary conditions for aquifer modeling during 21st century. Here, we report results from Project’s Phase 1, i.e. data based set up of a weather driven, semi distributed hydrological model Poli-Hydro, usable to mimic hydrology of high-altitude catchments watering the Po Valley. The adopted model simulates water budget, including dynamics of glaciers, snow melt, evapotranspiration, and subsequently provides routing time of overland and underground flow at any river section of the river network. In regulated catchments proper operation rules are developed to account for modified flows downstream. We demonstrate model accuracy against historical hydrological information. Modeled daily flows, underground flows, and the contribution of the irrigation systems within the TA can be used as inputs for aquifer dynamics models, to assess control of surface water budget upon aquifer dynamics. Projected hydrological scenarios will be also usable to mimic future hydrogeological dynamics of the area.

How to cite: Fuso, F., Righetti, C., Gorla, M., Desdemona, O., and Bocchiola, D.: Assessment of hydrological flows in the Po river basin in connection with the underground aquifer, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9914, https://doi.org/10.5194/egusphere-egu2020-9914, 2020

D111 |
EGU2020-11333
Youness Hrour, Zahra Thomas, Ophélie Fovet, Pauline Rousseau-Gueutin, Pascal Pichelin, and Karima Sebari

Water resources depletion under climate change is a major concern over the world. Mediterranean countries are deeply affected by changes in precipitation intensity, duration and frequency. Such changes lead to decrease in the averaged stream discharge and groundwater recharge consequently decreasing water resources availability. Our research focused on a case study performed in the Loukkos catchment, draining an area of 3730 km², located in the north of Morocco. Trend analysis of 8 to 62 years of precipitations was conducted based on statistical tests at about ten stations over the catchment. 20 to 70 years of temperature and discharge data were also analyzed. The time series were investigated using several non-parametric tests in order to characterize trends, to track down changes and their effect on agricultural land changes at the catchment scale. The present study highlights the impact of climate and catchment hydrology on agricultural practices and water resources used for irrigation. Analysis of precipitation indices showed that the temporal distribution of precipitation in the study area has changed since the 1970s. This change results from a reduction in precipitation, a shift in the hydrological year and a reduction in the number of wet days per year. Severe drought periods appear after the climatic rupture, which occurred around 1971. An increase in the intensity and frequency of droughts, in addition to an increase in the annual and seasonal average temperature (more than 1°C) were observed. Such changes contributed to agricultural practice modifications, with development of irrigated agriculture and later sowing period to adapt to the delay in the onset of the rains. For the future, the use of IPCC/CMIP5 climate projections for the Mediterranean region will help to evaluate how the precipitation indices will evolve. The impact of irrigation on stream discharge and groundwater recharge needs to be considered through agro-hydrological modeling including agricultural trajectory. Such tools will help to strengthen agricultural adaptation strategies and promote resilient farming practices.

Keywords: Precipitation trends, agricultural land use, water use for irrigation, agricultural adaptation strategies.

 

How to cite: Hrour, Y., Thomas, Z., Fovet, O., Rousseau-Gueutin, P., Pichelin, P., and Sebari, K.: Precipitation trends and ruptures effect on catchment hydrology and water resources availability for agricultural lands under climate change, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11333, https://doi.org/10.5194/egusphere-egu2020-11333, 2020

D112 |
EGU2020-11521
Pierre-Louis Frison, Adnane Chakir, Jamal Ezzahar, Pascal Fanise, Ludovic Villard, Nadia Ouaadi, Khaba Said, Mehrez Zribi, Valerie Le Dantec, Mohamed Kasbani, Salah Erraki, and Lionel Jarlan

This work deals with crops monitoring in a semi-arid environment, the Mediterranean region, where up to 90% of available water is used for irrigation. In addition to help for yield predictions, temporal monitoring at a regular time basis can help for the optimization of water use. We focused on the daily cycle of the backscattering radar coefficient over two different crop Mediterranean types: olive trees and wheat. With a six-day period between two consecutive acquisitions, the Sentinel-1 mission improves significantly the potential of SAR data for seasonal monitoring of earth surfaces. The available temporal frequency allows for the first time the temporal monitoring of natural surfaces in relation with seasonal changes. However, they are still many issues for better understanding Sentinel-1 temporal signatures and the full potential of these data over crop fields. Indeed, crop fields are characterized by contrasted surface states between bare soils and densely vegetated, with sudden changes due to field works (changing dramatically soil roughness or moisture) or harvests.  The MOCTAR experiment consists in the acquisitions of radar fully polarimetric interferometric C-band data acquired continuously at 10 min time step from the top of a tower. The study site is located in the Haouz plain, near the city of Marrakech, in the Chichaoua region, in Morocco. The region is characterized by a semi-arid Mediterranean climate, with an average of 250 mm of yearly precipitation. The region is characterized by two main seasons: wet and dry, extended from October to April and from May to September respectively. Maximum temperatures occur in July-August (average of 27.2 °C) and minimum in January (10.8° C). The study site is composed of two plots of 2.50 ha each, one consisting in olive trees, the other in wheat (Fig. 1). Both are irrigated with drip technique. The study site is documented for more than 10 years, and in situ measurements such as soil moisture, biomass, sapflow sensors (thermal dissipation method) and a micrometric dendrometer are regularly collected.

The radar antennas are fixed on a 20 m height tower, in a similar way than the TropiScat experiment They have been installed in May 2019. Four L-band antennas, two emitting and two receiving, one in H and the other in V polarizations, are visible on the bottom row. Above, six antennas operating at C band are mounted on two rows: four on the bottom one (two emitting and two receiving in H and V pol.) and above two receiving antennas in H and V pol. This configuration allows for interferometric fully polarimetric acquisitions also called PolInSAR. The acquisitions are made continuously with a 10 min time step.

First results show pronounced daily cycles, with amplitude of about 2 dB. These cycles are likely correlated to diurnal variations of tree water content and sap flow, but need to be further investigated sap flows and dielectric constant measurements made on the trunks. These results will be analyzed by comparison with Sentinel-1 temporal profiles.

How to cite: Frison, P.-L., Chakir, A., Ezzahar, J., Fanise, P., Villard, L., Ouaadi, N., Said, K., Zribi, M., Le Dantec, V., Kasbani, M., Erraki, S., and Jarlan, L.: C band radar crops monitoring at high temporal frequency: first results of the MOCTAR campaign, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11521, https://doi.org/10.5194/egusphere-egu2020-11521, 2020

D113 |
EGU2020-14106
Zoubair Rafi, Valérie Le Dantec, Olivier Merlin, Said Khabba, Patrick Mordelet, and Salah Er Raki

Agriculture is considered to be the human activity that consumes the most mobilized water on a global scale. However, crops planted in semi-arid areas regularly face periods of moderate to extreme water stress. Such water stress periods have a considerable impact on the seasonal yield of these crops. In order to participate in a more rational irrigation water management, monitoring of the rapid changes in plant water status is necessary. For this purpose, the combination of two different wavelength ranges will be explored : an index based on Xanthophyll cycle (Photochemical Reflectance Index, PRI) and a commonly-used index from thermal infrared spectral range (LST). An experiment on winter wheat was carried out over two agricultural campaigns (2016 to 2018) in the Haouz basin, which is located in the Marrakech region, to better assimilate the temporal dynamics of PRI and surface temperature. In this study, four different approaches are proposed to study the functioning of wheat : 1- an approach based on solar angle to remove the structure effect (PRI0) from the PRI signal and to derive a water stress index PRIj, 2- an approach based on global radiation (Rg) to extrapolate a theoretical PRI (PRIth) for Rg equal to zero and to calculate a water stress index PRIlin, 3- an approach that determines an optimal PRI (PRIpot) on the basis of the available water content (AWC) criterion in order to derive a stress index I-PRI and 4- an energy balance approach to extract dry and wet surface temperatures in order to establish a normalized surface temperature index (Tnorm). The results of this work show a strong correlation between the PRI0 and the Leaf Area Index with a coefficient of determination equal to 0.92, indicating that it is possible to isolate the structural effects of wheat on the PRI signal. In addition, over the range of variation in AWC, a significant correlation with PRIj, PRIjlin and I-PRI was observed with coefficients of determination of 0.71, 0.42 and 0.24, respectively. In contrast to the Tnorm, which varies only for values of AWC below 30%, a coefficient of determination of 0.22 is obtained. Finally, the PRI allows us to acquire early and complete information on the response of wheat to change in AWC as opposed to the surface temperature index, revealing the potential of the PRI to monitor the water status of plants and their responses to changing environmental conditions.

How to cite: Rafi, Z., Le Dantec, V., Merlin, O., Khabba, S., Mordelet, P., and Er Raki, S.: On the use of different approaches based on photochemical reflectance index and surface temperature to monitor the water status of winter wheat in semi-arid regions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14106, https://doi.org/10.5194/egusphere-egu2020-14106, 2020

D114 |
EGU2020-8588
Michel Le Page, Lionel Jarlan, Aaron Boone, Mohammad El Hajj, Nicolas Baghdadi, and Mehrez Zribi

An accurate knowledge of irrigation timing and rate is essential to compute the water balance of irrigated plots. However, at the plot scale irrigation is a data essentially known by the irrigator. These data do not go up to higher management scales, thus limiting both the management of water resources on a regional scale and the development of irrigation decision support tools at the farm scale. The study focuses on 6 experimental plots in the south-west of France. The new method consists in assessing surface soil moisture (SSM) change between observations and a water balance model. The approach was tested using both in situ measurements and surface soil moisture (SSM) maps derived from Sentinel-1 radar data. The score is obtained by assessing if the irrigation event is detected within +/- three days. The use of in situ SSM showed that: (1) the best revisit time between two SSM observations is 3 days; short gaps is subject to uncertainties while longer gap miss possible SSM variations; (2) in general, higher rates (>20mm) of irrigation are well identified while it is very difficult to identify irrigation event when it is raining or when irrigation rates are small (<10mm). When using the SSM microwave product, the performances are degraded but are still acceptable given the discontinuity of irrigation events: 34% of absolute error and a bias of 5% for the whole season. Although high vegetation cover degrades the SSM absolute estimates, the dynamic appeared to be in accordance with in-situ measurements.

How to cite: Le Page, M., Jarlan, L., Boone, A., El Hajj, M., Baghdadi, N., and Zribi, M.: Detection of irrigation events on maize plots using sentinel-1 soil moisture products, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8588, https://doi.org/10.5194/egusphere-egu2020-8588, 2020

D115 |
EGU2020-8614
Jamal Elfarkh, Salah Er-Raki, Jamal Ezzahar, Abdelghani Chehbouni, Bouchra Aithssaine, Abdelhakim Amazirh, Said Khabba, and Lionel Jarlan

The main goal of this work was to evaluate the potential of the Shuttleworth-Wallace (SW) model for mapping actual crop evapotranspiration (ET) over complex terrain located within the foothill of the Atlas Mountain (Morocco). This model needs many input variables to compute soil (rss) and vegetation (rsv) resistances, which are often difficult to estimate at large scale particularly soil moisture. In this study, a new approach to spatialize rss and rsv based on two thermal-based proxy variables is proposed. Land Surface Temperature (LST) and Normalized Difference Vegetation Index (NDVI) derived from LANDSAT data were combined with the endmember temperatures  for soil (Tsmin and Tsmax) and vegetation (Tvmin and Tvmax), which are simulated by a surface energy balance model, to compute the temperature of the two components, namely the soil (Ts) and the vegetation (Tv). Based on these temperatures, two thermal proxies (SIss for soil and SIsv for vegetation) were calculated and related to rss and rsv, with an empirical exponential relationship (with a correlation coefficient (R) of about 0,6 and 0,5 for soil and vegetation, respectively). The proposed approach was firstly evaluated at a local scale, by comparing the results to observations by an eddy covariance system installed over an area planted with olive trees intercropped with wheat. In a second step, the new approach was applied over a large area which contains a mixed vegetation (tall and short vegetation) crossed by a river to derive rss and rsv, and thereafter to estimate ET. A Large aperture scintillometer (LAS) installed over a transect of 1.4 km and spanning the total area is used to validate the obtained ET. The comparison confirms the ability of the proposed approach to provide satisfactory ET maps with an RMSE and R2 equal to 52.51 W/m2 and 0.80, respectively.

How to cite: Elfarkh, J., Er-Raki, S., Ezzahar, J., Chehbouni, A., Aithssaine, B., Amazirh, A., Khabba, S., and Jarlan, L.: Modified Shuttleworth-Wallace model for monitoring evapotranspiration over complex surface: Relationship between the surface resistances and remotely sensed stress indexes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8614, https://doi.org/10.5194/egusphere-egu2020-8614, 2020

D116 |
EGU2020-15757
Carla Taricco, Sara Rubinetti, Enrico Arnone, Davide Zanchettin, Angelo Rubino, and Ilaria Bizzarri

River discharge series provide large-scale hydrological information over a broad range of timescales. Despite discharge records consist of punctual measurements, they integrate variations in snowmelting, precipitation and runoff processes over the catchment till the discharge measurement site.

Discharges of the Rhone River, one of the largest rivers in Europe, have been monitored accurately during the last century at different sites. Long discharge records from seven stations along the course reveal the spatial and temporal behaviour of discharges from the source of the river to its mouth.  An accurate spectral analysis of the records, performed using advanced spectral analysis methods, allow us to extract significant periodic variations in the records at different temporal scales. Then, we analyse the sensitivity of such periodic variations to evolving hydroclimate conditions, in particular focusing on the relationship between discharge and temperature and precipitation.

The strong annual oscillation recorded at stations close to the source is almost entirely due to snow melting on alpine glaciers, closely resembling the temperature annual cycle. This remarkable agreement allows to consider the upstream discharges as a thermometer on the glacier region during the melting season. On the contrary, the decrease of the annual cycle going towards the mouth of the river and the contemporary growth of interannual components demonstrates the transition from a temperature to a precipitation controlled discharge regime.

We will finally discuss the impact of large-scale variability patterns on the detected discharge variations and associated implications for their near-term predictability.

How to cite: Taricco, C., Rubinetti, S., Arnone, E., Zanchettin, D., Rubino, A., and Bizzarri, I.: Gradual transition from temperature to precipitation controlled regime in Rhone River discharges, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15757, https://doi.org/10.5194/egusphere-egu2020-15757, 2020

D117 |
EGU2020-1108
Anastasiia Zemlianskova, Olga Makarieva, Nataliia Nesterova, and Danil Arkhipov

Crimean water resources are unevenly distributed and mainly generated at the slopes of the Crimean Mountains affecting water supply of population and industry of the peninsula. The study of water resources has been limited for the last 30 years due to political situation and little quantitative information is available about climate change impact on hydrological regime of Crimean rivers. The aim of the study was the assessment of current flow characteristics for three rivers originating from the Crimean Mountains (the Derekoyka River at Yalta; 49.7 km2, the Demerdjy River at Alyshta, 53 km2; the Kokkozka River at Golybinka, 83.6 km2) and their comparison to the historical period (1960-1990) data. The study area is characterized by a Mediterranean climate and has a pronounced high-altitude zoning. Main vegetation type is the oak forests and shrubs. The highest elevation of the slopes reaches 1500 m.

Due to the lack of hydrological data for the last 30 years, the assessment of current flow characteristics was conducted based on hydrological modelling and observed meteorological data. The hydrological model Hydrograph was used in the study. The model was successfully used for the simulations of streamflow in similar climate for the basins of the Black Sea coast of Russia (Makarieva et al., 2018; 2019). The model was parametrized based on the data on typical landscapes of the studied area. The verification of streamflow and water balance simulation results was conducted for the historical period (1960-1990). The model was used to produce streamflow hydrographs for the period of 1991-2018 based on meteorological data. The changes of hydrological regime of Crimean rivers was assessed in comparison with historical period. The results of the study will be presented.

How to cite: Zemlianskova, A., Makarieva, O., Nesterova, N., and Arkhipov, D.: Changes of hydrological regime in the mountain catchments of the Crimean Peninsula, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1108, https://doi.org/10.5194/egusphere-egu2020-1108, 2019

D118 |
EGU2020-3127
Josep Fortesa, Jérôme Latron, Julián García-Comendador, Miquel Tomàs-Burguera, Jaume Company, Aleix Calsamiglia, and Joan Estrany

The complexity of Mediterranean fluvial systems is caused by the multiple temporal and spatial heterogeneity in the relationships between the natural and human-induced abiotic and biotic variables. Accordingly, Mediterranean rivers are characterized by a large heterogeneity in hydrological regimes promoting significant temporal and spatial differences in the hydrological response.

This research investigates the non-linearity in the rainfall-runoff relationship at multiple temporal scales to achieve a better understanding of the hydrological response in representative small Mediterranean-climate catchments (i.e., < 10 km2). Rainfall-runoff was evaluated at annual and event scales. At annual scale, data from 43 catchments were collected to assess the influence of lithology on runoff response. At event scale, 203 events from 12 catchments were classified according to (a) seasonal occurrence (autumn, winter, spring or summer), (b) pervious or impervious lithology and (c) main land use (agricultural, agroforestry, forest or shrub). Besides, the inter- and intra-annual variability of the rainfall-runoff and the temporal downscaling (i.e., annual to event scale) was studied in Es Fangar Creek catchment (3.35 km2; Mallorca, Spain) during five hydrological years (2012-2017).

The assessment of rainfall-runoff relationships at annual scale in small Mediterranean-climate catchments showed a strong linearity in the hydrological response due to the importance of the annual rainfall amount. However, lithology effects on runoff generation explained an increase of the scattering in these relationships because pervious and impervious materials triggered larger and lower runoff contribution respectively. Although the significant correlation between rainfall and runoff, Es Fangar Creek dataset illustrated a huge intra-annual variability of the rainfall-runoff relationship as seasonal rainfall and evapotranspiration dynamics controlled the runoff response. These dynamics were observed in the average seasonal runoff coefficients, decreasing from winter to summer. These differences should be considered as a starting point of the non-linearity generation in the rainfall-runoff relationships at event scale.

At event scale, lineal and non-lineal performances were observed in the rainfall-runoff relationships in small Mediterranean-climate catchments suggesting that different factors conditioned the runoff response. Total rainfall was the most significant driver factor although the interaction between seasonality and the spatial diversity of lithology and land uses at catchment scale also played an important role on runoff generation. Thus, the highest correlations at seasonal scale were observed in those events occurred in winter and spring when the highest water reserves favoured the runoff response. Lithology caused higher dispersion in rainfall-runoff relationships at event scale in the set of small Mediterranean-climate catchments because pervious materials required higher antecedent wetness conditions. Agricultural land uses promoted the highest runoff generation. 

These findings will improve the comprehension of hydrological processes as the temporal downscaling of rainfall-runoff linked to the driven factors with the linearity and non-linearity knowledge is needed for accuracy and precision into hydrological modelling at event scale.

This work was supported by the research project CGL2017-88200-R “Functional hydrological and sediment connectivity at Mediterranean catchments: global change scenarios –MEDhyCON2” funded by the Spanish Ministry of Science, Innovation and Universities, the Spanish Agency of Research (AEI) and the European Regional Development Funds (ERDF). 

How to cite: Fortesa, J., Latron, J., García-Comendador, J., Tomàs-Burguera, M., Company, J., Calsamiglia, A., and Estrany, J.: Driving factors of non-linearity rainfall-runoff relationships at different time scales in small Mediterranean-climate catchments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3127, https://doi.org/10.5194/egusphere-egu2020-3127, 2020

D119 |
EGU2020-14815
Daniele Penna, Marco Borga, Elena Bresci, Giulio Castelli, Pietro Castellucci, Claudia Cocozza, Alessandro Errico, Ginevra Fabiani, Laurent Gourdol, Julian Klaus, Francesca Sofia Manca di Villahermosa, Laurent Pfister, Federico Preti, Cyrille Tailliez, Paolo Trucchi, Matteo Verdone, and Giulia Zuecco

The bi-directional ecohydrological interactions between forest dynamics and catchment hydrological response in Mediterranean forest ecosystems remain poorly conceptualized. Understanding the effect of tree water uptake and transpiration patterns on how catchments store and release water and, vice versa, on how catchment water availability affects tree physiological response is of paramount importance for forest and water resource management. This is crucial in the light of the predicted prolonged drought periods that will exacerbate the dry summer spells that characterize Mediterranean areas. In order to address these pressing issues, a new experimental mountain forested catchment for interdisciplinary ecohydrological research has been recently implemented in the Tuscan Apennines (Italy).

 

The catchment size is 2 km2 and elevation ranges from 650 to 1280 m a.s.l.. Forest covers more than 95% of the area, and the main tree species are beech and oak trees, with a much smaller proportion of conifers. Mean annual precipitation is around 1180 mm. Instrument installation is currently in progress and supported by two research projects (run in parallel in Italy and Luxembourg). By spring 2020, the catchment is expected to host the following equipment: one weather station plus one additional rain gauge, including a rainfall collector for isotope analysis; four stream gauges at different spatial scales (from a 2-ha headwater subcatchment to the catchment outlet) including continuous electrical conductivity measurements; three groundwater wells (ranging from 2 to 5 m depth) equipped with water level and electrical conductivity loggers; a network of soil moisture sensors at different depths; stemflow collectors; rain totalizers for manual throughfall measurements; a network of innovative multi-parametric sensors mounted on individual beech trees for continuous measurement (logging to cloud) of physiological and micro-meteorological parameters (sap flow, stem radial growth, canopy light transmission, stem wood temperature and humidity, 3D position over time, and air temperature and relative humidity).

 

Preliminary data collected in 2019 show a marked seasonality of stream runoff, with low runoff coefficients in summer (<0.1), consistent with the high drainage of forested soils and large evapotranspiration fluxes. Stream electrical conductivity values increase from upstream to downstream sections, showing a consistent spatial variability among seasons and suggesting an increasingly relevance of subsurface flow for sustaining baseflow. Marked diel fluctuations in stream water levels during sunny summer days suggest a dominant control of tree transpiration on streamflow. Near-surface soil moisture spatial patterns at the hillslope scale show strong temporal stability. Future experimental activities will assess water pools used by beech trees along a hillslope. Planned tools and research include water stable isotopes, seasonal variations in canopy interception, stemflow, and throughfall as well as the spatio-temporal variability of soil moisture patterns at the plot, hillslope, and catchment scale.

How to cite: Penna, D., Borga, M., Bresci, E., Castelli, G., Castellucci, P., Cocozza, C., Errico, A., Fabiani, G., Gourdol, L., Klaus, J., Manca di Villahermosa, F. S., Pfister, L., Preti, F., Tailliez, C., Trucchi, P., Verdone, M., and Zuecco, G.: Linking hydrological response to forest dynamics in Mediterranean areas: a new experimental catchment in the Apennine Mountains, Tuscany, Italy, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14815, https://doi.org/10.5194/egusphere-egu2020-14815, 2020

D120 |
EGU2020-10212
Camille Labrousse, Wolfgang Ludwig, Guillaume Lacquement, and Mahrez Sadaoui

Abstract:

The Languedoc-Roussillon region is a Mediterranean area located Southern France and composed of 6 main coastal river catchments about 1000 to 4800 km2 each and discharging to the Gulf of Lion. A first study investigating evidences of climatic changes in the river basins showed a significant reduction of the waterdischarge of 20 % in average in the whole area during the period 1965-2004 (40 years).By including the most recent years (up to 2018), the time series demonstrate that the decline in water discharge still continues and could consequently have been reduced by more than 40% since the years 1960. Thus, understanding the relation and effect of climatic changes on hydrology is essential for the development of water resource strategies.

In this study, we examine and analyse the long-term dynamics of the drought indices as climatic parameters and the impact of their changes on the 6 coastal river waterdischarge at the annual and seasonal scales. ­­­We investigate the meteorological, and agricultural droughts as well as the vegetation density’s evolution through time and compute statistical analysis to understand the linkage with the reduction of waterdischarge. First results show a trend toward dryer years as well as a strong correlation between mean annual hydrological variations and drought indices.

How to cite: Labrousse, C., Ludwig, W., Lacquement, G., and Sadaoui, M.: Impact of climate change in Mediterranean river basins: relation between droughts, vegetation and reduction of waterdischarge, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10212, https://doi.org/10.5194/egusphere-egu2020-10212, 2020

D121 |
EGU2020-21993
| Highlight
Fakir Younes, Le Page Michel, Jarlan Lionel, Boone Aaron, Berjamy Brahim, and Molle François

In a context of major changes (climate, demography, economy, etc.), the Southern Mediterranean area faces serious challenges with intrinsically low, irregular and continuously decreasing water resources. A method for translating a narrative scenario of irrigation water requirements into a quantitative scenario is presented. At first, we propose to describe the Irrigation Water Requirements (IWR) of any area by a single equation. IWR depends on climate (ET0, Rainfall), crop development estimated from remote sensing time series (crop coefficient/NDVI relationships), and four efficiencies parameters. In a second part, a reference model of the crop coefficient monthly cycle ( ) is proposed by empirically relating to rainfall and NDVI. Three variations of the model are compared in order to make a projection until 2050 based on downscaled climate change scenarios. The reliability of the model depends on the representativeness of the calibration period: It is considered to be high at the beginning of the simulation (RMSE below 0.1), but it deteriorates as the calibrating period gets shorter compared to the objective period: r2= 0.5, RMSE = [0.1-0.14], stderr = [0.02-0.03] by 2050. An alternative scenario is built upon the reference by interpreting the narrative as bending points. Finally, the examination of irrigation water demand until 2050 suggests that the difference between the two climate scenarios is very small (<2%), while the two proposed agricultural scenarios are strongly contrasted both spatially and in their impact on water resources.

How to cite: Younes, F., Michel, L. P., Lionel, J., Aaron, B., Brahim, B., and François, M.: Building quantitative scenarios of irrigation under climatic and anthropogenic changes in the mediterranean area: application to Morocco, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21993, https://doi.org/10.5194/egusphere-egu2020-21993, 2020

D122 |
EGU2020-8751
Bouchra Ait Hssaine, Olivier Merlin, Jamal Ezzahar, Salah Er-raki, Saïd Khabba, and Abdelghani Chehbouni

Over semi-arid agricultural regions, detecting the crop water need at the onset of water stress is of paramount importance for optimizing the use of irrigation water. Evapotranspiration (ET) is a crucial component of the water cycle, it strongly impacts the water resource management, drought monitoring, and climate. Remote sensing observations provide very relevant information to feed ET models. In particular, the microwave-derived surface (0-5 cm) soil moisture (SM), which is the main controlling factor of soil evaporation, the visible/near-infratred-derived vegetation cover fraction (fc), which provides an essential structural constraint on the fractioning between vegetation transpiration and soil evaporation, and - thermal-derived land surface temperature (LST), which is a signature of both available energy and evapotranspiration (ET) rate. The aim of this work is to integrate those independent and complementary information on total ET within an energy balance model. As a state-of-the-art and commonly used model, we chose the TSEB modelling as a basis for developments. An innovative calibration procedure is proposed to retrieve the main parameters of soil evaporation (soil resistance, rss) and plant transpiration (Priestly Taylor coefficient, αPT) based on a threshold on fc. The procedure is applied over an irrigated wheat field in the Tensift basin, central Morocco. Overall, the coupling of the soil resistance formulation with the TSEB formalism improves the estimation of soil evaporation, and consequently, improves the partitioning of ET. Analysis of the retrieved time series indicates that the daily αPT mainly follows the phenology of winter wheat crop with a maximum value coincident with the full development of green biomass and a minimum value reached at harvest. The temporal variations of αPT before senescence are attributed to the dynamics of both the root zone soil moisture and the amount of green biomass.

How to cite: Ait Hssaine, B., Merlin, O., Ezzahar, J., Er-raki, S., Khabba, S., and Chehbouni, A.: Assessing soil moisture constraint on soil evaporation and plant transpiration fractioning, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8751, https://doi.org/10.5194/egusphere-egu2020-8751, 2020