Comparaison des réponses du bilan hydrique de bassins situés en Belgique et en Suisse à un changement de climat

Les impacts possibles d'un changement de climat induit par l'augmentation de la concentration des gaz à effet de serre sur le bilan hydrique ont été simulés sur un ensemble de bassins hydrographiques situés en Belgique et en Suisse. Le modèle hydrologique conceptuel IRMB à pas de temps journalier a été utilisé à cette fin et les paramètres du modèle ont été optimisés sur chaque bassin. Les bassins ont une taille comprise entre 100 km2 et 1200 km2 et couvrent des régions de plaine aussi bien que de moyenne montagne. Un même scénario climatique a été adopté pour tous les bassins. Il est principalement caractérisé par une augmentation de la température de près de 3·C et par une légère augmentation des précipitations annuelles. Cette méthodologie a été adoptée afin de montrer les sensibilités respectives des différents termes du bilan hydrique et de les mettre en rapport avec les caractéristiques des bassins étudiés. L'étude s'est focalisée sur l'évolution de l'évapotranspiration et de l'humidité du sol, de l'enneigement, des débits à l'exutoire et des réserves en eau souterraine. Les impacts sont également abordés en termes d'événements extrêmes. Outre des évolutions qui sont prévisibles pour l'ensemble des bassins étudiés, telles une augmentation de l'évapotranspiration, une diminution légère de l'humidité du sol et une réduction de l'enneigement, les réponses de certains termes du bilan hydrique régis par les caractéristiques du sous-sol des bassins peuvent être sensiblement différentes d'une région à une autre. Ainsi, les bassins caractérisés par une infiltration importante subiraient une évolution favorable de leurs réserves en eau souterraine et des débits de base, alors que les bassins où le ruissellement de surface prédomine verraient une diminution se produire. L'altitude des bassins semble aussi jouer un rôle non négligeable. Tous les bassins de plaine présenteraient une augmentation des débits de crues extrêmes, alors que les bassins de moyenne montagne ne subiraient pour ainsi dire pas ces conséquences négatives.By strengthening the so called greenhouse effect, the rise of the atmospheric concentrations of anthropogenic gases, such as CO2, chlorofluorocarbons (CFCs) and methane, will progressively modify the energy budget of the Earth atmosphere and disturb the climate. Temperature at the soil level will rise. Precipitation and air humidity will be modified, inducing a large perturbation of the water cycle and thus of water availability and hydrological extremes. The last International Panel on Climate Change report (IPCC 1994) states that a rise of 0.3 degrees Celsius per decade could be felt in the mean global temperature in the next century. The conclusions of the Second World Climate Conference (1992) pointed out that among the most likely impacts of climate change will be its effects on the hydrological cycle and water management systems. An increase of the incidence of extreme events, such as floods and drought, would cause increased frequency and severity of disasters.The present paper is a synthesis of several separate published and some unpublished climate change impact studies (Bultot et al., 1988 a and b, 1992, 1994; Gellens, 1991; Schädler et al., 1992; Gellens and Demarée, 1993; Gellens and Roulin, 1996) carried out in Belgium and in Switzerland. All these studies have been done with the same hydrological model and the same climate change scenario. This procedure allows a strict comparison of the sensitivity studies and enables us to identify the common responses and the specific behaviour of the catchments. In this latter case, an attempt to identify the geomorphological origin of the particular responses is possible. A set of eight catchments in Belgium and belonging to the Scheldt and Meuse river basins has been studied. These individual catchments cover areas from 100 km2 to 1200 km2 and are spread over the country in order to represent the main catchment types. Precipitation ranges from 730 to 1160 mm per year. In addition, three tributaries of the Rhine river in Switzerland have been selected in the low alpine altitude (lower than 1500 m a.s.l.). Precipitation rates are higher for these three catchments and range from 1080 to 1300 mm. The adopted IRMB (Integrated Runoff Model - Bultot) hydrological model (Bultot et al., 1976 and 1985) is a daily time step conceptual model. It has been designed at the Royal Meteorological Institute of Belgium to simulate the components of the water cycle in medium- sized catchments, i.e. catchments for which the input data, and in particular the precipitation, can be considered as uniform. The main data needed to run the IRMB model are the precipitation and the potential evapotranspiration. This latter variable is assessed by following the procedure described by Bultot et al. (1983) and requires several climatological data, i.e. the net radiation, the air temperature and humidity, the soil temperature at 10, 20 and 50 cm depth and the wind speed at 2 m above the soil. These data are also taken into account in the snow melting- accumulation simulation.The adopted climate scenario has been constructed from the literature in order to combine the results of various simulations produced by different climate models (Bultot et al., 1988b) in a single set of climate increments. The main characteristics of the climate change scenario is a temperature rise reaching some 3 ¡C, with a higher increase in winter than in summer. Precipitation stress consists of a 50 mm yearly rise distributed as a winter rise (about 10 mm) and a slight summer decrease. Although these scenario increments are small in comparison with the year-to-year variability, they are however large enough to reveal the sensitivity of the water balance to climate perturbations. The detailed description of the algorithms used to apply the monthly increments on the daily time step are presented in Bultot et al. (1988b). After a calibration phase for the present climate conditions, a sensitivity analysis of the water balance of the catchments has been carried out by modifying the input data according to the scenario. This well known if - then - what? method gives the sensitivity of the various terms of the water cycle by comparing their values in the present runs and in the disturbed 2xCO2 runs. For practical reasons, the reference periods of the simulation runs are not the same for all the catchments.The study focuses on the evolution of evapotranspiration and soil moisture, of snow cover, of streamflow at the outlet and of groundwater storage. The impacts are also studied in terms of extreme events.For all the catchments, the analysis shows a rise of the evapotranspiration equivalent to some 7 to 10 percent. A small decrease in soil moisture has also been simulated associated with an increase in dry soil days. Due to the temperature rise a strong depletion of the snow cover might be an economically dominant effect in the low alpine regions where winter sport activities represent a large part of the inhabitants' resources. According to the winter precipitation rise, the monthly streamflows in the cold period are also increased under the 2xCO2 conditions.Besides predictable trends common to all the catchments, the study also shows that some components of the water balance governed by the underground characteristics can present uneven responses. Catchments characterized by strong infiltration could be subject to positive evolution of the groundwater storage and of the baseflow, whereas catchments with predominant surface runoff could exhibit the reverse effect. These effects could be important mainly in summer during the low flow period. The altitude of the catchments also seems to be significant. All the lowland catchments present higher extreme streamflows, whereas catchments in low Alpine regions are spared this negative consequence. While a large degree of uncertainty remains in the assessment of the climate in the next century, this study gives a first insight into the direction of the expected climate change impacts. It also points out the need to analyse the sensitivity of catchments with a particular attention to their characteristics

Climate change and mountain water resources: overview and recommendations for research, management and policy

Mountains are essential sources of freshwater for our world, but their role in global water resources could well be significantly altered by climate change. How well do we understand these potential changes today, and what are implications for water resources management, climate change adaptation, and evolving water policy? To answer above questions, we have examined 11 case study regions with the goal of providing a global overview, identifying research gaps and formulating recommendations for research, management and policy. <br><br> After setting the scene regarding water stress, water management capacity and scientific capacity in our case study regions, we examine the state of knowledge in water resources from a highland-lowland viewpoint, focusing on mountain areas on the one hand and the adjacent lowland areas on the other hand. Based on this review, research priorities are identified, including precipitation, snow water equivalent, soil parameters, evapotranspiration and sublimation, groundwater as well as enhanced warming and feedback mechanisms. In addition, the importance of environmental monitoring at high altitudes is highlighted. We then make recommendations how advancements in the management of mountain water resources under climate change could be achieved in the fields of research, water resources management and policy as well as through better interaction between these fields. <br><br> We conclude that effective management of mountain water resources urgently requires more detailed regional studies and more reliable scenario projections, and that research on mountain water resources must become more integrative by linking relevant disciplines. In addition, the knowledge exchange between managers and researchers must be improved and oriented towards long-term continuous interaction

Comparison of embedded and added motor imagery training in patients after stroke: Study protocol of a randomised controlled pilot trial using a mixed methods approach

Copyright @ 2009 Schuster et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Background: Two different approaches have been adopted when applying motor imagery (MI) to stroke patients. MI can be conducted either added to conventional physiotherapy or integrated within therapy sessions. The proposed study aims to compare the efficacy of embedded MI to an added MI intervention. Evidence from pilot studies reported in the literature suggests that both approaches can improve performance of a complex motor skill involving whole body movements, however, it remains to be demonstrated, which is the more effective one.Methods/Design: A single blinded, randomised controlled trial (RCT) with a pre-post intervention design will be carried out. The study design includes two experimental groups and a control group (CG). Both experimental groups (EG1, EG2) will receive physical practice of a clinical relevant motor task ('Going down, laying on the floor, and getting up again') over a two week intervention period: EG1 with embedded MI training, EG2 with MI training added after physiotherapy. The CG will receive standard physiotherapy intervention and an additional control intervention not related to MI.The primary study outcome is the time difference to perform the task from pre to post-intervention. Secondary outcomes include level of help needed, stages of motor task completion, degree of motor impairment, balance ability, fear of falling measure, motivation score, and motor imagery ability score. Four data collection points are proposed: twice during baseline phase, once following the intervention period, and once after a two week follow up. A nested qualitative part should add an important insight into patients' experience and attitudes towards MI. Semi-structured interviews of six to ten patients, who participate in the RCT, will be conducted to investigate patients' previous experience with MI and their expectations towards the MI intervention in the study. Patients will be interviewed prior and after the intervention period.Discussion: Results will determine whether embedded MI is superior to added MI. Findings of the semi-structured interviews will help to integrate patient's expectations of MI interventions in the design of research studies to improve practical applicability using MI as an adjunct therapy technique

Impact of climate change on hydrological regimes and water resource management in the Rhine basin”,

Abstract. The International Commission for the Hydrology of the Rhine basin (CHR) has carried out a research project to assess the impact of climate change on the river flow conditions in the Rhine basin. Along a bottom-up line, different detailed hydrological models with hourly and daily time steps have been developed for representative sub-catchments of the Rhine basin. Along a topdown line, a water balance model for the entire Rhine basin has been developed, which calculates monthly discharges and which was tested on the scale of the major tributaries of the Rhine. Using this set of models, the effects of climate change on the discharge regime in different parts of the Rhine basin were calculated using the results of UKHI and XCCC GCM-experiments. All models indicate the same trends in the changes: higher winter discharge as a result of intensified snow-melt and increased winter precipitation, and lower summer discharge due to the reduced winter snow storage and an increase of evapotranspiration. When the results are considered in more detail, however, several differences show up. These can firstly be attributed to different physical characteristics of the studied areas, but different spatial and temporal scales used in the modelling and different representations of several hydrological processes (e.g., evapotranspiration, snow melt) are responsible for the differences found as well. Climate change can affect various socio-economic sectors. Higher temperatures may threaten winter tourism in the lower winter sport areas. The hydrological changes will increase flood risk during winter, whilst low flows during summer will adversely affect inland navigation, and reduce water availability for agriculture and industry. Balancing the required actions against economic cost and the existing uncertainties in the climate change scenarios, a policy of 'noregret and flexibility' in water management planning and design is recommended, where anticipatory adaptive measures in response to climate change impacts are undertaken in combination with ongoing activities. Present address

Inconsistent impacts of decomposer diversity on the stability of aboveground and belowground ecosystem functions

The intensive discussion on the importance of biodiversity for the stability of essential processes in ecosystems has prompted a multitude of studies since the middle of the last century. Nevertheless, research has been extremely biased by focusing on the producer level, while studies on the impacts of decomposer diversity on the stability of ecosystem functions are lacking. Here, we investigate the impacts of decomposer diversity on the stability (reliability) of three important aboveground and belowground ecosystem functions: primary productivity (shoot and root biomass), litter decomposition, and herbivore infestation. For this, we analyzed the results of three laboratory experiments manipulating decomposer diversity (1–3 species) in comparison to decomposer-free treatments in terms of variability of the measured variables. Decomposer diversity often significantly but inconsistently affected the stability of all aboveground and belowground ecosystem functions investigated in the present study. While primary productivity was mainly destabilized, litter decomposition and aphid infestation were essentially stabilized by increasing decomposer diversity. However, impacts of decomposer diversity varied between plant community and fertility treatments. There was no general effect of the presence of decomposers on stability and no trend toward weaker effects in fertilized communities and legume communities. This indicates that impacts of decomposers are based on more than effects on nutrient availability. Although inconsistent impacts complicate the estimation of consequences of belowground diversity loss, underpinning mechanisms of the observed patterns are discussed. Impacts of decomposer diversity on the stability of essential ecosystem functions differed between plant communities of varying composition and fertility, implicating that human-induced changes of biodiversity and land-use management might have unpredictable effects on the processes mankind relies on. This study therefore points to the necessity of also considering soil feedback mechanisms in order to gain a comprehensive and holistic understanding of the impacts of current global change phenomena on the stability of essential ecosystem functions

No Adverse Effect of Genetically Modified Antifungal Wheat on Decomposition Dynamics and the Soil Fauna Community – A Field Study

The cultivation of genetically modified (GM) plants has raised several environmental concerns. One of these concerns regards non-target soil fauna organisms, which play an important role in the decomposition of organic matter and hence are largely exposed to GM plant residues. Soil fauna may be directly affected by transgene products or indirectly by pleiotropic effects such as a modified plant metabolism. Thus, ecosystem services and functioning might be affected negatively. In a litterbag experiment in the field we analysed the decomposition process and the soil fauna community involved. Therefore, we used four experimental GM wheat varieties, two with a race-specific antifungal resistance against powdery mildew (Pm3b) and two with an unspecific antifungal resistance based on the expression of chitinase and glucanase. We compared them with two non-GM isolines and six conventional cereal varieties. To elucidate the mechanisms that cause differences in plant decomposition, structural plant components (i.e. C∶N ratio, lignin, cellulose, hemicellulose) were examined and soil properties, temperature and precipitation were monitored. The most frequent taxa extracted from decaying plant material were mites (Cryptostigmata, Gamasina and Uropodina), springtails (Isotomidae), annelids (Enchytraeidae) and Diptera (Cecidomyiidae larvae). Despite a single significant transgenic/month interaction for Cecidomyiidae larvae, which is probably random, we detected no impact of the GM wheat on the soil fauna community. However, soil fauna differences among conventional cereal varieties were more pronounced than between GM and non-GM wheat. While leaf residue decomposition in GM and non-GM wheat was similar, differences among conventional cereals were evident. Furthermore, sampling date and location were found to greatly influence soil fauna community and decomposition processes. The results give no indication of ecologically relevant adverse effects of antifungal GM wheat on the composition and the activity of the soil fauna community