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The present work aims to quantify the impact of climate change (CC) on the grain yields of irrigated cereals and their water requirements in the Tensift region of Morocco. The Med-CORDEX (MEDiterranean COordinated Regional Climate Downscaling EXperiment) ensemble runs under scenarios RCP4.5 (Representative Concentration Pathway) 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 analyzed. The results show that the rise in air temperature causes a shortening of the development cycle of up to 50 days. The impacts of rising temperature and changes in precipitation on wheat yields are next evaluated, based on the AquaCrop model, both with and without taking into account the fertilizing effect of CO 2 . As expected, optimal wheat yields will decrease on the order of 7 to 30% if CO 2 concentration rise is not considered. The fertilizing effect of CO 2 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%, 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.

Assessing water supply sustainability is crucial to meet stakeholders' needs, notably in the Mediterranean. This region has been identified as a climate change hot spot, and as a region where water demand is continuously increasing due to population growth and the expansion of irrigated areas. The Hérault River catchment (2500 km2, France) is a typical example and a negative trend in discharge has been observed since the 1960s. In this context, local stakeholders need to evaluate possible future changes in water allocation capacity in the catchment, using climate change, dam management and water use scenarios. A modelling framework that was already calibrated and validated on this catchment over the last 50 years was used to assess whether water resources could meet water demands at the 2030 horizon for the domestic, agricultural and environmental sectors. Water supply sustainability was evaluated at the sub-basin scale according to priority allocations using a water supply capacity index, frequency of unsatisfactory years as well as the reliability, resilience and sustainability metrics. Water use projections were based on the evolution of population, per-unit water demand, irrigated areas, water supply network efficiency, as well as on the evaluation of a biological flow. Climate projections were based on an increase in temperature up to 2°C and a decrease in daily precipitation by 20%. Adaptation strategies considered reducing per-unit water demand for the domestic sector and the importation of water volume for the agricultural sector. The dissociated effects of water use and climatic constraints on water supply sustainability were evaluated. Results showed that the downstream portions would be the more impacted as they are the most exploited ones. In the domestic sector, sustainability indicators would be more degraded by climate change scenarios than water use constraints. In the agricultural sector the negative impact of water use scenarios would be stronger. The environmental sector would be hardly satisfied especially in summer with low resilience levels. The adaptation strategies considered in this study would not be sufficient to cope with both anthropogenic and climate changes. Other strategies were discussed based on known examples in the Mediterranean context., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Assessing water supply capacity is crucial to meet stakeholders' needs, notably in the Mediterranean region. This region has been identified as a climate change hot spot, and as a region where water demand is continuously increasing due to population growth and the expansion of irrigated areas. The Hérault River catchment (2500 km(2), France) is a typical example and a negative trend in discharge has been observed since the 1960s. In this context, local stakeholders need first to understand the processes controlling the evolution of water resources and demands in the past to latter evaluate future water supply capacity and anticipate the tensions users could be confronted to in the future. A modelling framework is proposed at a 10-day time step to assess whether water resources have been able to meet water demands over the last 50 years. Water supply was evaluated using hydrological modelling and a dam management model. Water demand dynamics were estimated for the domestic and agricultural sectors. A water supply capacity index is computed to assess the extent and the frequency to which water demand has been satisfied at the sub-basin scale. Simulated runoff dynamics were in good agreement with observations over the calibration and validation periods. Domestic water demand has increased considerably since the 1980s and is characterized by a seasonal peak in summer. Agricultural demand has increased in the downstream sub-basins and decreased upstream where irrigated areas have decreased. As a result, although most water demands were satisfied between 1961 and 1980, irrigation requirements in summer have sometimes not been satisfied since the 1980s. This work is the first step toward evaluating possible future changes in water allocation capacity in the catchment, using future climate change, dam management and water use scenarios., (Copyright © 2013 Elsevier B.V. All rights reserved.)