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.
vPICO presentations: Fri, 30 Apr
In semi-arid areas, plant water use and plant water stress can be derived over large
areas from remotely sensed evapotranspiration estimates. Those can help us to monitor the
impact of drought on the agro- and ecosystems. Both variables can be simulated by a dual
source energy balance model that relies on meteorological variables (air temperature, relative
humidity, wind speed and global radiation) and remote sensing data (surface temperature,
NDVI, albedo and LAI). Surface temperature acquired in the Thermal InfraRed (TIR) domain
is particularly informative for monitoring agrosystem health and adjusting irrigation
requirements. However, available meteorological observations period may often be
insufficient to account for the variability present in the study area. Statistical downscaling
methods applied to reanalysis data can serve to generate surrogate series of meteorological
variables that either fill the gaps in the observation period or extend the observation period in
the past. For this aim, a stochastic weather generator (SWG) is adapted in order to compute
temporal extension of multiple meteorological variables. This surrogate series is then used to
constrain the dual-source model Soil Plant Atmosphere and Remote Evapotranspiration
(SPARSE). Stress index anomalies retrieved from SPARSE are then compared to anomalies in
other wave lengths in order to assess their capacity to detect incipient water stress and early
droughts at the kilometer resolution. Those are the root zone soil moisture at low resolution
derived from the microwave domain, and active vegetation fraction cover deduced from
NDVI time series.
How to cite: Farhani, N., Boulet, G., Carreau, J., Kassouk, Z., Le Page, M., Lili Chabaane, Z., and Zitouna, R.: Contribution of remote sensing and auxiliary variables in the study of the evolution of periods of droughts, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2306, https://doi.org/10.5194/egusphere-egu21-2306, 2021.
This paper aims to analyze the agronomic drought in a highly anthropogenic semi-arid region, North Africa. In the context of the Mediterranean climate, characterized by frequent droughts, North Africa is particularly affected. Indeed, in addition to this climatic aspect, it is one of the areas most affected by water scarcity in the world. Thus, understanding and describing agronomic drought is essential. The proposed study is based on remote sensing data from TERRA-MODIS and ASCAT satellite, describing the dynamics of vegetation cover and soil water content through NDVI and SWI indices. Two indices are analyzed, the Vegetation Anomaly Index (VAI) and the Moisture Anomaly Index (MAI). The dynamics of the VAI is analyzed for different types of regions (agircultural, forest areas). The contribution of vegetation cover is combined with the effect of soil water content through a new drought index combining the VAI and MAI. A discussion of this combination is proposed on different study areas in the study region. It illustrates the complementarity of these two informations in analysis of agronomic drought.
How to cite: Zribi, M., Nativel, S., and Le Page, M.: Analysis of agronomic drought over North Africa using remote sensing satellite data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14780, https://doi.org/10.5194/egusphere-egu21-14780, 2021.
Cereals are the main crop in Morocco. Its production exhibits a high inter-annual due to uncertain rainfall and recurrent drought periods. Considering the importance of this resource to the country's economy, it is thus important for decision makers to have reliable forecasts of the annual cereal production in order to pre-empt importation needs. In this study, we assessed the joint use of satellite-based drought indices, weather (precipitation and temperature) and climate data (pseudo-oscillation indices including NAO and the leading modes of sea surface temperature -SST- in the mid-latitude and in the tropical area) to predict cereal yields at the level of the agricultural province using machine learning algorithms (Support Vector Machine -SVM-, Random forest -FR- and eXtreme Gradient Boost -XGBoost-) in addition to Multiple Linear Regression (MLR). Also, we evaluate the models for different lead times along the growing season from January (about 5 months before harvest) to March (2 months before harvest). The results show the combination of data from the different sources outperformed the use of a single dataset; the highest accuracy being obtained when the three data sources were all considered in the model development. In addition, the results show that the models can accurately predict yields in January (5 months before harvesting) with an R² = 0.90 and RMSE about 3.4 Qt.ha-1. When comparing the model’s performance, XGBoost represents the best one for predicting yields. Also, considering specific models for each province separately improves the statistical metrics by approximately 10-50% depending on the province with regards to one global model applied to all the provinces. The results of this study pointed out that machine learning is a promising tool for cereal yield forecasting. Also, the proposed methodology can be extended to different crops and different regions for crop yield forecasting.
How to cite: Bouras, E. H., Jarlan, L., Er-Raki, S., Balaghi, R., Amazirh, A., Richard, B., and Khabba, S.: Cereal yield forecasting combining satellite drought-based indices, regional climate and weather data using machine learning approaches in Morocco, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14590, https://doi.org/10.5194/egusphere-egu21-14590, 2021.
An optimal operation criteria in Mediterranean dams is specially required to prevent damages associated with flood and drought events, which are common and directly connected with the intrinsic seasonal and annual climate variability over these regions. That need is clear in multipurpose dams, that usually include hydropower systems in these catchments. These systems must guarantee an equilibrium between an optimum storage for production and the capacity needed for flood abatement. Specially relevant are torrential flooding events, in which quick decisions need to be taken to prevent not only the associated damages, but also the energy production losses connected to a conservative approach. Those facts are translated into a huge range of possibilities that difficulties the optimization of decision making processes. On the one hand, several meteorological forecasting systems at different spatiotemporal scales are currently available. However, the greater uncertainty linked to the rapid response time of these catchments limits their use. On the other hand, the insufficient number of control points with available real time measurements (i.e., precipitation gauges and water level controls) challenges the creation of early warning systems with an appropriate uncertainty quantification.
This study proposes the basis for the definition of an early warning system based on a limited number of real time in situ measurements in a characteristic Mediterranean catchment. The Cala dam (59 hm3), located in the Rivera de Cala river, was chosen as an example. Cala dam is mainly used for hydroelectric production, but also for irrigation and leisure activities. Their upstream catchment (535 km2) is characterized by agroforestry uses and a quick response to intense precipitation due to steep slopes, shallow soils and groundwater redistribution, which does not favour the lamination of water. In situ historical information from, stations with available real time data in the watershed is used to: (a) define driver indicators of key streamflow states (i.e., a threshold in the cumulative precipitation since the beginning of the hydrological year or precipitation intensity over certain months); and, (b) caracterize and cluster precipitation-runoff events over the catchment. The three resulting most significant three types of events were validated during the last period of the observed data. This information was translated into a decision tree using a conditional structure, constituting the basis of the designed early warning system This scheme allows to identify the potential occurrence of a warning situation, which is fixed by the normal operational rules of the reservoir. Once the flood event is underway, the use of real time information about the water volume stored in the reservoir and the estimated probability of occurrence of an discharge event in the next hour based on antecedents precipitation, are the hydrological indicators to base the decision on together with the generation thresholds and requirements of the hydropower system. The approach is also validated based on historical information within a hindcast process during the validation period.
How to cite: Contreras, E., Vela, S., Pimentel, R., and Polo, M. J.: Basis for a flood early-warning system approach in fast-flow Mediterranean catchments: The case study of Cala reservoir (Spain), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15613, https://doi.org/10.5194/egusphere-egu21-15613, 2021.
Morocco experiences a semi-arid climate with both Mediterranean and Atlantic influences, causing a strong variability of rainfall. It has also high mountain ranges from North to South, separating vast regions with contrasted climatic and hydrologic conditions. In this context, Morocco is highly vulnerable to extreme hydrological events, such as floods and extended drought periods, impacting the population and the economic activities. In a global change context, there is a need to investigate whether these hydrological extremes are becoming stronger since an increased vulnerability has been observed in the last decades. Here, we analyzed long-term time series of daily flows from 17 basins located in the North (Mediterranean: Loukkos), in the center (Atlantic: Bourgreg, Oum Errabia) and in the South Western (Tensift, Souss, Massa, Draa) of Morocco. The objective is to evaluate the evolution of floods and low-flows in a regional perspective. For that purpose, statistical models for extreme values allowing non-stationarity are used in combination with trend-detection tests. The results showed increasing trends in maximum annual flows only at two stations in central Morocco, while decreasing trends in the north and south prevail. On the contrary, changes in low-flows and river intermittency are more widespread across the basins with contrasted climatic conditions.
How to cite: Boughdadi, S., Saidi, M. E. M., and Tramblay, Y.: Changing patterns of extreme hydrological events in Morocco, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4722, https://doi.org/10.5194/egusphere-egu21-4722, 2021.
Accurate measurement of precipitation is very important for flood forecasting, hydrological modeling, and estimation of the water balance of any basin. The lack of a weather monitoring network is an obstacle to the accurate measurement of precipitation.
In most of the Moroccan High Atlas Mountains regions, ground observation stations are still unreliable and difficult to access due to several parameters, such as a large spatial and temporal variation of rainfall and ruggedness of topography, which lead to irregularity and scarcity of measuring stations. This area is characterized by arid and semi-arid climates where generally occurred a few rainy days but have experienced significant flash floods.
Consequently, floods are causing extended damages to the population and infrastructures every year. However, research on hydrological processes is limited due to the irregularity of the gauge station network and the large number of gaps frequently observed in the rainfall and runoff data acquired from the gauge stations. Remote sensing precipitation data with high spatial and temporal resolution are a potential alternative to gauged precipitation data.
This study evaluates the performance of the two satellite products: the Tropical Rainfall Measuring Mission (TRMM 3B43V7) Multi-satellite Precipitation Analysis (TMPA) and the Integrated Multi-satellite Retrievals for GPM (IMERG V06) (SPPs) to observed rainfall, at different time scales (daily, monthly, and annual) from 1 September 2000 to 31 August 2017 over the Ghdat watershed, with different statistical indices and hydrological assessment, to evaluate the reliability of these (SPPs) data to reproduce rainfall events by implementing them in a hydrological model, to determine their ability to detect all types of rainfall events.
Daily, monthly, and annual rainfall measurements were validated using widely used statistical measures (CC, RMSE, MAE, Bias, Nash, POD, FAR, FBI and ETS).
The results showed that: (1) The correlation between satellite precipitation data and rainfall precipitation demonstrated a high correlation on all daily, monthly, and annual scales. (2) The product (TRMM 3B42V7) exhibits better quality in terms of correlation on the monthly and annual scale, while the (GPM IMERG V06) product shows a high correlation on the daily scale compared to the measurements of the gauges. (3) The (GPM IMERG V06) product has better performance regarding the precipitation detection capability, compared to the (TRMM 3B42V7) product which could detect only tiny precipitation events, but not able to capture moderate or strong precipitation events. (4) Flood events can be simulated with the hydrological model using both observed precipitation data and satellite data with the Nash – Sutcliffe model efficiency coefficient (NSE) ranging from 0.65 to 0.90.
According to the results of this study, we concluded that (TRMM 3B42V7) and (GPM IMERG V06) satellite precipitation products can be used for flood modeling and water resource management, particularly in the semi-arid and Mediterranean region.
How to cite: Benkirane, M., Laftouhi, N.-E., Khabba, S., and El Mansouri, B.: Assessment of GPM and TRMM Satellite Precipitation Products, and their application for Flood Simulations at Daily Scale in a sparsely gauged watershed;Case of Ghdat basin (High Atlas, Morocco)., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4917, https://doi.org/10.5194/egusphere-egu21-4917, 2021.
Extreme precipitation events are atmospheric phenomena causing floods that generate great economic and social losses. The Mediterranean region is characterized by a strong variability in time and space that favors the appearance of this type of phenomena. Therefore, determining the origin of humidity must be done.
The UTrack-atmospheric-moisture model  is a Lagrangian tool to track atmospheric moisture flows forward in time using ERA-5 reanalysis weather data. The labeled moisture is released into the atmosphere in the form of evaporation. After determine the allocated moisture precipitated at each time, this model allows us to know the percentage of relative humidity that has precipitated for each of the labeled sources. Here we present a comparison of these results with previous results obtained by other Lagrangian methods.
 Tuinenburg, Obbe A., and Arie Staal. Tracking the global flows of atmospheric moisture and associated uncertainties." Hydrology and Earth System Sciences 24.5 (2020): 2419-2435.
How to cite: Cloux, S., Insua-Costa, D., Miguez-Macho, G., and Perez-Muñuzuri, V.: Lagrangian review of the origin of the humidity for the case of two extreme precipitation events in the Mediterranean region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7540, https://doi.org/10.5194/egusphere-egu21-7540, 2021.
Piedmont areas are globally important hydrological systems as transitional zones between mountains (headwater basins) where water is produced and adjacent plains (basins floor) where water is consumed. In arid and semiarid areas, the water availability in piedmonts have made them adequate places for rural communities’ settlement and irrigation activities. The hydrochemical processes controlling groundwater chemistry in the piedmont areas might be influenced by the interaction with the mountain streamflow, the geology, the climate and the human activities. In this study we investigated the hydrochemistry of the groundwater in the piedmont of Ourika wadi that is coming from the High-Atlas of Marrakech Mountains (central Morocco). The HCO3-Ca-Na groundwater type, inherited form the streamflow, is the primary water facies in the area. It has its origin from carbonates dissolution and silicates withering in the High-Atlas mountains. In the irrigated area, the ion exchange processes are responsible of Ca and Mg enrichment. Currently, the groundwater salinity is low and the chemical quality is excellent thanks to the seasonal groundwater recharge from the mountain streamflow and to the practiced traditional agriculture that generally uses high amounts of irrigation and low amounts chemical fertilizers. However, major concerns about groundwater sustainability arise from two parameters. Firstly, the snowmelt-driven runoff supplying the groundwater recharge in piedmonts is in continuous decrease because of the snow cover reduction observed in the last decades and forecasted in the future under climate change, likely putting more pressure on groundwater resources. Secondly, due to the growing anthropogenic activities the traditional agriculture might change to intensive agriculture using more chemicals and inducing pollution.
How to cite: Bouimouass, H., Fakir, Y., Tweed, S., and Leblanc, M.: Groundwater sustainability in a semiarid traditional irrigation piedmont supplied by high mountain streamflow, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9925, https://doi.org/10.5194/egusphere-egu21-9925, 2021.
The study analyzes the changes in the rainfall-runoff process as a result of land cover changes occurred between 1990-2018 in the Guadalest Reservoir basin with an area of 122.5 km2, using the model of the HEC-HMS model at daily scale and to capture the complex hydrological dynamics based on GIS information . The purpose is to analyze the spatial-temporal evolution of the hydrological response in 12 sub-basins and the dynamics of land use/land cover changes for the years 1990, 2000, 2006, 2012 and 2018.
The findings reveal a change in the type of sclerophyll vegetation (forests of Quercus (calliprinos, ilex, rotundifolia, suber, etc.)from 81.56% in the 1990 initial stage, to natural grasslands by 81.55% in the 2018 stage; a decrease in agricultural areas and their conversion into coniferous forests and natural grasslands by approximately 60% in the same period; if exists an increase of coniferous forest to the detriment of the agriculture, implies that the evapotranspiration will increase and the run-off will decrease with an increase in runoff in principle but as time goes by it decreases bringing as a consequence a deficit in water supply. The results of land use change detection between the years 1990-2018 were corroborated with the values of the curve numbers obtained.
The cyclical and trend analysis of the historical series of precipitation allows evidencing a five-year cycle and a decreasing trend from 1984 to 2018.
The HEC-HMS model implementation at a daily scale and GIS-based tools have proven to be useful in achieving the study objectives. Within the HEC-HMS, the SCS Curve Number model and the Muskingum method were suitable for solving the rainfall-runoff conversion and flood propagation equations, respectively.
The researching work debeloped is intended to identify the impact derived by the anthropic action in the change of land use and Its vegetable coverage, and how this may impact on the evotranspiration, surface run-off, and the post hydropical drainage of The Guadalest Reservoir which will use for the Integral Management of the Basin. These findings provide to the water management planners very useful information about the effects of flash floods, which have human lives cost in the ravine basin studied in recent years.
Land use change, evapotranspiration, runoff, HEC-HMS hydrological model, basin, Mediterranean
How to cite: Palacios Cabrera, T. A., Valdés Abellán, J., Jódar Abellán, A., and Alulema, R.: Hydrodynamic behaviour of a semiarid Mediterranean watershed, under changing hydrological conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9023, https://doi.org/10.5194/egusphere-egu21-9023, 2021.
In Mediterranean mountain regions, traditional irrigation systems still persist in areas where the modernization approaches do not succeed in being operational. It is common that these systems alter the soil uses, vegetation distribution and hydrological natural regime.
This is the case of the extensive network of irrigation ditches in the Sierra Nevada Mountain Range in southeastern Spain (an UNESCO Reserve of the Biosphere, with areas as Natural and National Park), which originated in Muslim times, and is still operational in some areas. These ditches have contributed to maintaining local agricultural systems and populations in basins dominated by snow conditions, and they constitute a traditional regulation of water resources in the area. The network is made up of two types of irrigation ditches: “careo” and irrigation ditches. The first, the "careo", collects the meltwater and infiltrates it along its course, maintaining a high level of soil moisture and favouring deep percolation volumes that can be later consumed by the population through springs and natural fountains. The second, the irrigation ones, are used to transport water from the natural sources to the agricultural plots downstream the mountain area. In 2014, several irrigation ditches were restored in the Natural Park. This is a chance to further explore and quantify the role of this network in the hydrological budget on a local basis.
The aim of this work is to evaluate to what extent the existence of these intermittent water networks affects the evolution of the surrounding vegetation. For this, one of the restored systems, the Barjas Ditch in the village of Cañar, with a successful water circulation along its way, was selected from the increase of the soil water content in the ditch influence area and, indirectly a differential development of vegetation. Two analyses are performed using remote sensing information. The Normalized Difference Vegetation Index, NDVI, which is a spectral index used to estimate the quantity, quality and development of vegetation that can therefore be used indirectly as an indicator of the state of soil moisture, was used as the indicator of evolution. For this purpose, a historical set of LandSat satellite images (TM, ETM+ and OLI) has been used. On the one hand, a global analysis on the whole mountainous range was carried out, comparing NDVI patterns in areas affected and non-affected by the ditches. On the other hand, the restored Barjas ditch is used to assess vegetation changes before and after the restoration.
How to cite: Aparicio, J., Pimentel, R., and Polo, M. J.: Environmental benefits of traditional irrigation ditches in the Sierra Nevada (Spain) ecosystem by analysing the spatial-temporal evolution of NDVI on different time scales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15870, https://doi.org/10.5194/egusphere-egu21-15870, 2021.
Nowadays, the assessment of agricultural management is based mainly on the good management of water resources (i.e., to estimate the crops water consumption and provide their irrigation requirements). In this context, several agro-environmental models, (i.e., STICS, AQUACROP, TSEB, …) have been developed to assess the agricultural needs such as grain yield and/or irrigation demand prediction. These models are mainly based on the remote sensing data which contribute highly to the knowledge of some key-variables of crop models, in particular their time and space variations. The study area is the Haouz plain located in central Morocco. The climate of the plain is semi-arid continental type characterized by strong spatiotemporal irregular rains (mean annual precipitation up to 250 mm).The region relies mainly on the agricultural activities. Therefore, about 85% of available water is used for irrigated crops within the plain. The irrigated area is covered by 25% tree plantations and 75% annual crops. However, the annual crops extent depends strongly on the water availability during the season. Hence, for sustainable monitoring and optimal use of water resources (using physical modeling, satellite images and ground data), SAMIR software is developed in order to spatialize the irrigation water budget over Haouz plain. SAMIR (Simonneaux et al., 2009; Saadi et al., 2015; Tazekrit et al., 2018) is a tool for irrigation management based mainly on the use of remote sensing data. It estimates the crop evapotranspiration (ET) based on the FAO-56 model. This model requires three types of data: climatic variables for calculation of reference Evapotranspiration (ET0), land cover for computing crop coefficient Kc, and periodical phonological information for adjusting the Kc. SAMIR offers the possibility to calculate the ET of a large agricultural areas, with different land use/ land cover types, and subsequently deduce the necessary water irrigation for these areas. This model has been calibrated and validated over R3 perimeter (Diarra et al., 2017). In the present work, we studied the sensitivity (local sensibility analysis) of SAMIR software to the variations of each input parameter (i.e., ET0, precipitations, soil parameters, and irrigation configuration “real or automatic”). The simulations were made using the ground truth observations and irrigation dataset of the agricultural season of 2011/2012 over an irrigated area of Haouz plain. For the climatic variables, the obtained results showed that the effect of the ET0 is more significant compared to the effect of precipitations. It led to large shifts of the actual ET simulated by SAMIR compared to all tested parameters. For soil parameters, the sensitivity analysis illustrates that the effect is almost linear for all parameters. But the proportion of total available water, P, is the high sensitive parameter (Lenhart, et al., 2002). Finally, the comparison between the simulation of real evapotranspiration using automatic irrigation or real irrigation configuration offers an interesting result. The obtained ET values are similar for both configurations. Thus, this result offers the possibility of using only automatic irrigation configuration, in case of non-availability of the real irrigation.
How to cite: Moumni, A., Diarra, A., and Lahrouni, A.: Local sensitivity analysis of Satellite Monitoring of Irrigation software (SAMIR) over Semi-Arid climate of Morocco, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5383, https://doi.org/10.5194/egusphere-egu21-5383, 2021.
The quality of effluents from wastewater treatment plants still challenging especially in underprivileged rural areas where water resources are mostly affected by pollution, depletion and excessive exploitation. Thus, the prediction of phosphorus removal is one of the most important tasks in the management of wastewater effluent. Predictive model accuracy is crucial for safe reuse of treated water for public health and the environment. However, linear models that use a high dimensional dataset may be unable to build accurate and interpretable models. To address this complexity, the current study evaluates the effect of hydraulic retention time (HRT) on the removal of orthophosphates (PO4–P) and total phosphorus (TP) by the multi-soil-layering (MSL) eco-friendly technology. In addition, it attempts to predict this removal from domestic wastewater using a combined approach based on feature selection technique and gradient boosting machine algorithm (GBM). Sixteen physicochemical and bacterial indicators were monitored for a one-year period. The results show that the HRT impact significantly (p < 0.01) the removal of phosphorus content by the MSL system. The HRT, pH, PO4–P and TP were suggested relevant for predicting the removal of TP, while HRT and PO4–P were sufficient for predicting the removal rate of PO4–P. The analysis of accuracy using the validation dataset demonstrates that GBM models have high credibility as they achieve an R² > 0.92, while the analysis of sensitivity reveals that the HRT was the most important factor affecting phosphorus removal in the MSL system. In addition, the modeling results show that the GBM model has proven to be useful for predicting pollutant removal in the MSL technology and investigating its behavior.
How to cite: Sbahi, S., Ouazzani, N., Lahrouni, A., Hejjaj, A., and Mandi, L.: Gradient Boosting Machine for Phosphorus Removal Prediction in Multi-Soil-Layering (MSL) system operated in a rural area, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5269, https://doi.org/10.5194/egusphere-egu21-5269, 2021.
The presentation will summarize the main findings of the chapter “Water” of the report “Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future”. This report was published in November 2020 and prepared by 190 scientists from 25 countries, who belong to the scientific network “Mediterranean Experts on Climate and Environmental Change”.
Water resources in the Mediterranean are scarce, unevenly distributed and often mismatching human and environmental needs. Approx. 180 million people in the southern and eastern Mediterranean countries suffer from water scarcity (<1000 m3 capita-1 yr-1). The main water use is for agriculture, and more specifically on the southern and eastern rim. Water demand for both tourism and agriculture peak in summer, potentially enhancing conflicts in the future. Municipal water use is particularly constrained in the south and will likely be exacerbated in the future by demographic and migration phenomena. Northern countries face additional risks in flood prone areas where urban settlements are rapidly increasing.
Climate change, in combination with demographic and socio-economic developments, has mainly negative consequences for the water cycle in the Mediterranean Basin, including reduced runoff and groundwater recharge, increased crop water requirements, increased conflicts among users, and increased risk of overexploitation and degradation. These impacts will be particularly severe for global warming higher than 2°C.
Adequate water supply and demand management offers some options to cope with risks. Technical solutions are available for improving water use efficiency and productivity, and increasing reuse. Seawater desalination is increasingly used as adaptation measure to reduce (potable) water scarcity in dry Mediterranean countries, despite known drawbacks in terms of environmental impacts and energy requirements. Promising solar technologies are under development, potentially reducing emissions and costs. Reuse of wastewater is a solution for agriculture and industrial activities but also recharge of aquifers. Inter-basin transfers may lead to controversies and conflicts. Construction of dams contributes to the reduction of water and energy scarcities, but with trade-offs in terms of social and environmental impacts.
Overall, water demand management, which increases water use efficiency and reduces water losses, is crucial for water governance for a sustainable development. Maintaining Mediterranean diet or coming back to it on the basis of locally produced foods and reducing food wastes may save water but also carbon emissions while having nutritional and health benefits.
 Fader M., Giupponi C., Burak S., Dakhlaoui H., Koutroulis A., Lange M.A., Llasat M.C., Pulido-Velazquez D., Sanz-Cobeña A. (2020): Water. In: Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future. First Mediterranean Assessment Report [Cramer W, Guiot J, Marini K (eds.)] Union for the Mediterranean, Plan Bleu, UNEP/MAP, Marseille, France, 57pp, in press. Download
How to cite: Fader, M., Giupponi, C., Burak, S., Dakhlaoui, H., Koutroulis, A., Lange, M. A., Llasat, M. C., Pulido-Velazquez, D., Sanz-Cobeña, A., Grillakis, M., Mrabet, R., Saurí, D., Savé, R., Todorovic, M., Tramblay, Y., and Zwirglmaier, V.: Future water-related risks and management options in the Mediterranean basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10570, https://doi.org/10.5194/egusphere-egu21-10570, 2021.
Surface runoff rates in torrents are driven by land use and climate changes. Moreover, the effects of control works, such as the check dams, can modify these rates. In the Mediterranean semi-arid watersheds (e.g., in Southern Italy and Spain), this forcing may sum to local factors, such as steep slopes, small drainage areas and heavy and short-duration rainstorms. Therefore, it is important to evaluate the hydrological effects of each action (presence of check dam, land use changes and future climate forcing), in order to control flash floods, soil erosion and landslides at the watershed scale. To this aim, this study evaluates the annual runoff rates in two headwaters of Southern Italy, mainly forested and agricultural, using a modeling approach. More specifically, the well-known Soil and Water Assessment Tool (SWAT) model is applied to Vacale (12.5 sq. km) torrent, regulated by check dams built in ‘1950-1960, and Serra torrent (13.7 sq. km), not regulated. Both sub-watersheds experienced an increase in forest cover up to 70%, while the agricultural land decreased by about 30% of the total area in the period after the construction of the control works until now. Previously, the model was calibrated in a third torrent (Duverso, 12.5 sq. km, gauged for runoff measurements), with the same climatic and geomorphological characteristics, using the automatic calibration by the SWATCUP program. After calibration, SWAT simulated the hydrological response under different land uses (forest, pasture and bare soil, the latter simulating total deforestation) and climate change scenarios (applying a Global Circulation Model, under 2.6 and 8.5 Representative Concentration Pathways) throughout the next 80 years. The results of this modeling experience showed that: (i) the presence of check dams noticeably reduced the hydrological response of the regulated headwater compared to the torrent without check dams; (ii) the vegetal cover of the forestland has been the most important factor in mitigating the surface runoff rate in comparison to the other land uses; (iii) under the future climate change scenarios, the surface runoff will increase with increasing mean temperatures and precipitation intensity. The model outputs help supporting a better understanding on the impacts of control works as well as land use and climate changes on the runoff generation capacity in Mediterranean torrents. These indications are useful to watershed managers in the adoption of the most effective strategy to mitigate flash flood hazards and heavy erosion risks in similar environmental contexts.
Acknowledgement: This research was funded by ERDF/Spanish Ministry of Science, Innovation and Universities-State Research Agency (AEI) /Project CGL2017-84625-C2-1-R; State Program for Research, Development and Innovation Focused on the Challenges of Society.
How to cite: Zema, D. A., Bombino, G., Carrà, B. G., D'agostino, D., Denisi, P., Labate, A., Martinez Salvador, A. A., Perez Cutillas, P., Zimbone, S. M., and Conesa Garcia, C.: Hydrological effects of climate and land use changes in regulated vs. unregulated headwaters of Southern Calabria , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2223, https://doi.org/10.5194/egusphere-egu21-2223, 2021.
Land use/ Land cover (LULC) and climate change are two main factors affecting watershed hydrology. In this study, combined effects of changes in climate and LULC on hydrological processes are investigated by comparing baseline period (2000-2013) to future conditions (2030-2070) using the Soil and Water Assessment Tool (SWAT) hydrological model in the Siliana catchment in Tunisia.
The LULC future scenarios are modelled using the Cellular Automata (CA)-Markov chain while climate change scenarios were derived from the regional climate models (RCMs) in the coordinated regional climate downscaling experiment (CORDEX-Europe). The (CDF) matching approach with observed precipitation and temperature records is used for bias correction. Subsequently, bias corrected climate projections and LULC future scenarios are fed in the SWAT model to assess changes in catchment hydrology based on a set of hydrological indicators (e.g. monthly discharge and total water availability). Prediction uncertainty related to changes in LULC, climate conditions and SWAT model parameter are also assessed.
A significant decrease in pasture and an increase in irrigated lands will likely shape the future LULC in comparison to the baseline conditions. However, these changes will be combined by a warmer and drier climate and hydrological conditions in the future in the Siliana catchment. By considering only changes in LULC in the reference period, there was a slight reduction in the surface runoff and total available water in the catchment.
KEYWORDS: hydrologic response; land use change; climate change; uncertainty; Mediterranean catchment; SWAT model; CA-Markov
How to cite: EL Ghoul, I., Sellami, H., Mounir, K., Khlifi, S., and Vanclooster, M.: Hydrological response of LULC and climate change in Mediterranean basin: application to the Siliana catchment in Tunisia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6043, https://doi.org/10.5194/egusphere-egu21-6043, 2021.
In the south Mediterranean catchments, most of the available water resources are used to produce hydro-electric energy, for drinking water as well as for irrigated agriculture located downstream in the surrounding plains. This water Tower role is today threatened by the increase in water needs relative to the growth of the population and its standard of living, by the intensification of irrigated agriculture and by climate change. The south Mediterranean region is now well known as a “hot-spot” for the latter and there is reasonable evidence showing that mountainous region should face enhanced warming compared to the surrounding plains in the future. In this context, the development of a high-resolution futuristic climate forcing on the Tensift catchments. Based on the high-resolution SAFRAN reanalysis developed in the study presented above. is very important for the study of the climate, with a trend for the 2041-2060 horizon. For this purpose, we used future climate scenarios provided by the Euro-CORDEX program evaluated over the region. To achieve this objective, two RCP runs at 12 km resolution are downscaled using the quantile-quantile approach based on temperature and precipitation acquired at the Marrakech station in the plain and at the Oukaimeden station located at an altitude of 2687m in the High Atlas. It is shown that higher warming is expected on the mountainous region than in the plain station (2.8°C versus 2.3°C for the maximum temperature and 2.8° versus 2° for the minimum temperature; scenario RCP8.5 for 2041-2060). The higher warming on the minimum temperature may drastically impact the snow/rain partition in the high Atlas. Based on these disaggregated climate scenarios, future spatialized forcing are built from the correction functions obtained at the two above-mentioned plain and mountain stations and the SAFRAN re-analysis. The mountainous area is expected to face a higher increase of air temperature than in the plain, reaching +2.5°C for RCP8.5 and +1.71°C for RCP4.5 over 2041-2060. This warming will be accompanied by a marked decrease in precipitation (-16% for RCP8.5). this future spatialized data set is to be used within impact studies, in particular concerning water resources.
How to cite: Moucha, A., Hanich, L., Tramblay, Y., Saadi, A., Gascoin, S., Martin, E., Lepage, M., Szczypta, C., and Jarlan, L.: High-resolution futuristic climate forcing over semi-arid catchments. Case of the Tensift (Morocco), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6536, https://doi.org/10.5194/egusphere-egu21-6536, 2021.
In the Mediterranean, climate change and human pressures are expected to significantly impact surface water resources. We studied these impacts on the water discharge of six coastal drainage basins of the Gulf of Lions in southern France over the sixty-years period 1959-2018. Our approach was based on statistical analyses of hydrological, climate, land use and water management data. Results suggested that the annual water discharge of the six rivers studied can be predicted with high confidence by only two climatic indices, exclusively calculated from monthly temperature and precipitation data. This is a strong argument that climate is clearly the dominant driver of water discharge trends in the study region. These models also easily allow individual testing of the role of temperatures and precipitations on the evolution of annual water discharge. The latter decreased with about 30-45% in the study catchments over the 1959-2018 period and 25% can be attributed solely to the annual temperatures increase. Considering future projections of different climate models under a RCP 8.5 scenario, which depicts the strongest climatic changes, the annual water discharge could still decrease about 49-87% during the 2006-2100 period. For all models, we furthermore examined the relationships between the observed and simulated climatologies, our climatic indices and the large scale teleconnection patterns in order to better understand the spatial and temporal variabilities in the predicted water discharge series.
How to cite: Labrousse, C., Pinel, S., Sadaoui, M., Ludwig, W., and Lacquement, G.: Impact of climate change on superficial water resources in the South of France: statistical modelling over historical and future scenario periods, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7132, https://doi.org/10.5194/egusphere-egu21-7132, 2021.
Climate change scenarios predict water scarcity in Mediterranean region, particularly in areas that are exposed to weather related disasters (drought, flood...) (IPCC, 2014). These changes will most likely impact food security by altering the hydrological cycle and water availability. Considering that water is the economic engine of the Mediterranean countries that rely especially on agricultural production, several studies have been focused on understanding and quantifying the climate change effects on hydrological regime. In addition, the complexity of these impacts can be due also to a bad resources management that can hinder the countries’ development (Marin M., 2020). To study the hydrological function of the Ouergha watershed, the SWAT model was used to simulate daily runoff response for the period 1997-2017, including three years (1993-1997) for the warming-up of the model. Calibration and validation of the model were applied for the period 1997-2017 using the SUFI-2 algorithm, and the simulation estimates the water flows of the Ouergha basin in a monthly time step. The water balance indicates a predominance of evaporation losses accounting for 41% of total rainfall. Runoff represents 8% of precipitation while lateral flow is 7%. The remainder is distributed between the 5% deep aquifer recharge and percolation, in addition to the flow to the river which represents about 39%. The Swat model is considered as suitable tool for the management of water resources even though under changing climatic conditions, it’s prone to errors and uncertainties that needs to be assessed to make full benefits from this model challenging (Sellami H., 2014).To analyze these uncertainties a modelling approach based on the combination of hydrological model and a set of high resolution CORDEX climate models has been developed. The results are considered as a decision-making tool for local and regional actors.
IPCC. (2014). Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp.
Marin M., C. L. (2020). Assessing the vulnerability of water resources in the context of climate changes in a small forested watershed using SWAT: A review. Environmental Research,. doi:https://doi.org/10.1016/j.envres.2020.109330.
Sellami H., L. J. (2014). France), Uncertainty analysis in model parameters regionalization: a case study involving the SWAT model in Mediterranean catchments (Southern. Hydrology and Earth System Sciences, 18, 2393–2413. doi:doi:10.5194/hess-18-2393-201.
How to cite: Mounir, K., Sellami, H., El Ghoul, I., El Khanchoufi, A., and La Jeunesse, I.: Assessing the water resources vulnerability of Ouergha catchment under climate change projection, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6545, https://doi.org/10.5194/egusphere-egu21-6545, 2021.
Soil moisture is a key component for water resources management especially for irrigation needs estimation. We analyze in the present study, the potential of L-band data, acquired by (Advanced Land Observing Satellite-2) ALOS-2, to retrieve soil moisture over bare soils and cereal fields located in semi-arid area in the Kairouan plain.
In this context, we evaluate radar signal sensitivity to roughness, soil moisture and vegetation biophysical parameters. Based on multi-incidence radar data (28°, 32.5° and 36°), high correlations characterize relationships between backscattering coefficients in dual-polarization (HH and HV) and root mean square of heights (Hrms) and Zs, parameters, Sensitivity of radar data to soil moisture was discussed for three classes of NDVI (less than 0.25 for bare soils and dispersed vegetation, between 0.25 and 0.5 for medium vegetation and greater than 0.5 for dense cereals). With vegetation development, where NDVI values are higher than 0.25, SAR signal remains sensitive to soil moisture in HH pol. This sensitivity to moisture disappears, in HV pol for dense vegetation. For covered fields, L-band signal is very sensitive to Vegetation Water Content (VWC), with R² values ranging between 0.76 and 0.61 in HH and HV polarization respectively.
Simulating signal behavior is carried out through various models over bare soils and covered cereal fields. Over bare soils, proposed empirical expressions, modified versions of Integral Equation Model (IEM-B) and Dubois models (Dubois-B) are evaluated, generally for HH and HV polarizations. Best consistency is observed between real data and IEM-B backscattering simulations in HH polarization. More discrepancies between real and modelled data are observed in HV polarization.
Furthermore, to simulate L-band signal behavior over covered fields, the inversion of Water Cloud Model (WCM) coupled to different bare soil models is realized through direct equations and Look-up tables. Two options of WCM, are tested (with and without soil-vegetation interaction scattering term). For the first option, results highlight the good performance of IEM-B coupled to WCM in HH polarization with RMSE value between estimated and in situ moisture measurements equal to 4.87 vol.%. By adding soil – cereal interaction term in the second option of WCM, results reveal a stable accuracy in HH polarization and an important improvement of soil moisture estimations in HV polarization, with RMSE values are ranging between 6 and 7 vol.%.
How to cite: Ayari, E., Kassouk, Z., Lili Chabaane, Z., Bousbih, S., and Zribi, M.: Soil moisture estimation over cereals fields using l-band alos2 data (merguellil case – KAIROUAN), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-422, https://doi.org/10.5194/egusphere-egu21-422, 2021.
Mediterranean mountain areas are especially vulnerable to changes. Climatic trends observed in the last decades point out to an increasing number of extreme events (i.e., number of heat waves and droughts) and consequently, a direct alteration of the hydrological states of their associated ecosystems. The savanna type ecosystem called dehesa is one of them. This system is the result of a long-term co-evolution of indigenous ecosystems and human settlement in a sustainable balance, with high relevance from both the environmental (biodiversity) and socioeconomic (livestock farming, including Iberian pork food industry) point of view. Dehesa systems have a complex vegetation cover structure, where isolated trees, mainly holm oak, cork oak and oak, Mediterranean shrubs, and pastures coexist. Different problems have arisen in dehesa during last years, an example of them are seca episodes, a disease of oak trees that results in drying and final death. This condition is caused by a fungus, but very likely triggered by external hydrological related conditions like air temperature and soil water content. Remote sensing techniques have been widely used as the best alternative to monitor vegetation patterns over these areas. However, the presence of clouds and the fixed spatiotemporal resolution of these sensors constitute a limitation in more local studies.
This work proposes the combined use of remote sensing by both terrestrial photography and satelital sensors, and hydrometeorological information as data sources for improving the hydrological characterization of vegetation in dehesa areas. The study was carried out in the Santa Clotilde experimental area, within the Cardeña-Montoro Natural Park (southern Spain). Three years of local sub-daily terrestrial photography and hydrometeorological information allowed us to define different hydrometeorological/ecohydrological indicators that are representative of key vegetation states. This local information is linked with vegetation indexes derived from high spatial resolution satellite information (i.e., Landsat TM, ETM+ and OLI (30 m x 30 m) and Sentinel-2 (10 m x 10 m) and distributed meteorological variables to extend the results from the local to the watershed scale. The promising results will be used in a short future as the basis of an advanced monitoring service where meteorological seasonal forecast information could be used to derive key indicators and help in a priori diagnosis of the system facilitating decisions making.
This work has been funded by project SIERRA Seguimiento hIdrológico de la vEgetación en montaña mediteRránea mediante fusión de sensores Remotos en Andalucía), with the economic collaboration of the European Funding for Rural Development (FEDER) and the Office for Economy, Knowledge, Enterprises and University of the Andalusian Regional Government.
How to cite: Pimentel, R., Torralbo, P., Aparicio, J., Pérez-Palazón, M. J., Andreu, A., González-Dugo, M. P., and Polo, M. J.: Combining remote sensing and hydrological information for improving hydrological characterization of dehesas in Mediterranean mountain areas: a study case in Cardeña-Montoro Natural Park (Spain), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10898, https://doi.org/10.5194/egusphere-egu21-10898, 2021.
Irrigation is the largest consumer of water in the world, with more than 70% of the world's fresh water dedicated to agriculture. In this context, we developed and evaluated a new method to predict daily to seasonal irrigation timing and amounts at the field scale using surface soil moisture (SSM) data assimilated into a simple land surface model through a particle filter technique. The method is first tested using in situ SSM before using SSM products retrieved from Sentinel-1. Data collected on different wheat fields grown in Morocco, for both flood and drip irrigation techniques, are used to assess the performance of the proposed method. With in situ data, the results are good. Seasonal amounts are retrieved with R > 0.98, RMSE <42 mm and bias<2 mm. Likewise, a good agreement is observed at the daily scale for flood irrigation where more than 70% of the irrigation events are detected with a time difference from actual irrigation events shorter than 4 days, when assimilating SSM observation every 6 days to mimics Sentinel-1 revisit time. Over the drip irrigated fields, the statistical metrics are R = 0.70, RMSE =28.5 mm and bias= -0.24 mm for irrigation amounts cumulated over 15 days. The approach is then evaluated using SSM products derived from Sentinel-1 data; statistical metrics are R= 0.64, RMSE= 28.78 mm and bias = 1.99 mm for irrigation amounts cumulated over 15 days. In addition to irrigated fields, the applicationof the developed methodover rainfed fieldsdid not detect any irrigation. This study opens perspectives for the regional retrieval of irrigation amounts and timing at the field scale and for mapping irrigated/non irrigated areas.
How to cite: Ouaadi, N., Jarlan, L., Khabba, S., Ezzahar, J., and Merlin, O.: Surface soil moisture data assimilation for irrigation amounts and timing estimation in semi-arid regions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14594, https://doi.org/10.5194/egusphere-egu21-14594, 2021.
In the south Mediterranean region already facing water scarcity, up to 80% of available water is used by irrigated agriculture. This work focuses on the analysis of the C-band response of a tree crop with in situ data acquired with a time step of 15 mns in the final objective of developing water stress detection approaches based on radar data. Focus is put on the daily cycle of the radar-backscattering coefficient and of the interferometric coherence. The site is located in the Chichaoua region (Morocco) was equipped in May 2019 with 6 C-band radar antennas installed on a 20 m tower. In parallel, automatic acquisitions at a half hourly time step of latent and sensible heat fluxes, sapflow, soil moisture and temperature profile together with manual measurements of LAI, soil roughness and above ground biomass every 15 days were carried out. The preliminary results show a strong daily cycle of the interferometric coherence with a significant drop of the coherence during daytime. The coherence loss at dawn occurred concurrently with the start of the sapflow while minimum values were observed in the afternoon when wind speed is maximum. A significant daily cycle of the backscattering coefficient is also prominent. The amplitude of the daily cycle decreased from the dormancy period in winter from up to 2dB to less than 1dB in summer when physiologic activity of the trees is at its maximum. These first results open perspectives for the monitoring of the hydric status of crops within the frame of future radar missions in geostationary orbit.
How to cite: Chakir, A., frison, P., khabba, S., ezzahar, J., villard, L., ouaadi, N., ledantec, V., fanise, P., and jarlan, L.: Monitoring of an irrigated olive orchard using C-band backscattering coefficient and interferometric coherence at high temporal frequency: preliminary results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12780, https://doi.org/10.5194/egusphere-egu21-12780, 2021.
C-band radar observations have shown a high sensitivity to the water status of vegetation, including forests and crops. Several studies conducted mainly on forests have observed daily changes of the backscattering coefficients between ascending and descending orbits and have suggested that these differences are related to the diurnal cycle of vegetation water content. Likewise, the water movement within annual crops could be associated to change of the phase centre locations leading to a daily cycle of the interferometric coherence as well that has already been observed on tropical forest using C-band in situ acquisitions. In this context, an experimental setup composed of 4C-band antennas targeting an irrigated wheat field was installed at the top of a 20 m tower near Chichaoua (Morocco) from January to June 2020. The collected data includes measurements of the backscattering coefficient at both cross- and parallel polarizations and the interferometric coherence with a 15 mns time step. The field is also equipped with an eddy-correlation station for half hourly measurements of convective fluxes, soil moisture and temperature profiles. Simultaneously, measurement of above-ground biomass, leaf area index, canopy height and surface roughness are also carried out every 15-daysduring the agricultural season. The preliminary results of the experiment reveal the existence of strong correlation between the daily evolution of interferometric coherence and the physiological activity of wheat at dawn while the changes observed in the afternoon are ratherrelated to the wind peaks. For the backscattering coefficient, a good agreement is observed between the evolution of its daily average and the evolution of evapotranspiration. These open insights for the monitoring of the crops water status using radar dataacquired at sub-daily timescale.
How to cite: Ouaadi, N., Villard, L., Ezzahar, J., Frison, P., Khabba, S., Chakir, A., Er-raki, S., and Jarlan, L.: Analysis of diurnal cycles of interferometric coherence and backscattering coefficient measured on an irrigated wheat field in Morocco, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14849, https://doi.org/10.5194/egusphere-egu21-14849, 2021.
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