Abstract. The Meuse is an important rain-fed river in NorthWestern Europe. Nine million people live in its catchment, split over five countries. Projected changes in precipitation and temperature characteristics due to climate change would have a significant impact on the Meuse River and its tributaries. In this study, we focused on the impacts of climate change on the hydrology of two sub-catchments of the Meuse in Belgium, the Lesse and the Vesdre, placing the emphasis on the water-soil-plant continuum in order to highlight the effects of climate change on plant growth, and water uptake on the hydrology of two sub-catchments. These effects were studied using two climate scenarios and a physically based distributed model, which reflects the water-soil-plant continuum. Our results show that the vegetation will evapotranspirate between 10 and 17 % less at the end of the century because of water scarcity in summer, even if the root development is better under climate change conditions. In the low scenario, the mean minimal 7 days discharge value could decrease between 19 and 24 % for a two year return period, and between 20 and 35 % for a fifty year return period. It will lead to rare but severe drought in rivers, with potentially huge consequences on water quality.

There is a wide recognition of the watershed scale as the right scale for global water management, notably in the context of the water framework directive. Hence, it often refers to international management and therefore to various pre-existing regional management tools, models or even objectives. In this study, we aim at describing the collaborative assessment of climate change's effect on low-flow regime and the consequences on three water-related sectors: drinking water production, agriculture and electricity production. The paper highlights the choices that were made during the study that involved scientific teams, managers and stakeholders from the four main countries of the Meuse Basin. It shows that the methodological choices were operational and aimed at preserving existing methods and knowledge within each country. They led to hydrological scenarios comparable to the main available ensemble approaches and to methodologies well accepted within the concerned countries. The results of the project highlight and quantify the water scarcity that the three sectors will have to face by the end of the century mainly regarding the electricity production. They also show that common allocation rules are necessary to manage water demand during future low-flow periods.

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Soil -Water Systems is a division of the department of Environmental Sciences and Technologies of Gembloux Agro-Bio Tech (GxABT), the agronomy faculty of the University of Liège (B). Environmental management is, in fact, one of the two main research topics of the faculty, the other one being the valorisation of bioproducts, both linked with the production of bioresources. Management plans of arable, forested and natural lands proposed by GxABT will take into account global change (climate change, land use changes and urbanisation). Therefore, within the Soil -Water Systems division, projects focus on the link between hydrology and agriculture, taking account of climate change. Indeed, climate change disturbs most natural phenomena and it is important to quantify and mitigate these impacts.As a partner of the AMICE project, we have contributed to the study of the hydrological effects of climate change on the Meuse catchment and developed a methodology to evaluate its impacts on the Mosan agriculture. Results have shown that both winter high flows and summer low flows could be exacerbated. Studying these extreme conditions is thus essential. Consequences on the agricultural sector can be both positive and negative, depending on the range of predicted changes and the adaptation capacity of agricultural systems. We have found that, in the Meuse catchment, yields would increase for wheat, barley and grasslands but decrease for corn. However, the variability in yields would rise in the future. The study has also revealed that the different crops would start growing and reach maturity earlier. Agricultural systems will therefore need to be adapted (e.g. adaptation of the cultural calendar by moving forward the seeding and harvesting dates) (Drogue et al. 2010, Bauwens et al 2011.The simulations for this study were performed with a physically-based model able to simulate the water-soil-plant continuum (derived from the EPIC model). The EPIC model has actually been adapted to the Walloon Region (EPICgrid) and has also been used to model nitrate concentration in the recharge water. EPICgrid has allowed us to evaluate diffuse nitrate pollution and the efficiency of present and further mitigation measures. Simulations results have shown that current measures to reduce the effect of diffuse pollution on water quality are not sufficient in some areas and that new actions are necessary. Scenarios including modifications of agricultural practices, such as a change in crop rotations or a decrease in the use of mineral fertilisers, have shown significant effects on water quality. Nevertheless, due to transfer time through the vadose zone (more than 20 years in some subregions), it was shown that an increase in groundwater nitrate concentrations will occur until at least 2030 for some regions before new agricultural pracUsing agro-hydrology to adapt to climate evolutions A. Degré, C. Sohier, A. Bauwens & M. Grandry Univ. Liège -Gembloux Agro-Bio Tech, Soil-Water Systems, Gembloux, Belgium ABSTRACT: Natural phenomena such as f...

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