Future Scenarios of Surface Water Resources Availability in North African Dams

Climate change may have strong impacts on water resources in developing countries. In North Africa, many dams and reservoirs have been built to secure water availability in the context of a strong inter-annual variability of precipitation. The goal of this study is to evaluate climate change impacts on surface water resources for the largest dams in Algeria, Morocco and Tunisia using high-resolution (12 km) regional climate models (RCM) simulations. To evaluate the atmospheric demand (evapotranspiration), two approaches are compared: The direct use of actual evaporation simulated by the RCMs, or estimation of reference evapotranspiration computed with the Hargreaves-Samani (HAR) equation, relying on air temperature only, and the FAO-Penman Monteith (PM) equation, computed with temperature, wind, radiation and relative humidity. Results showed a strong convergence of the RCM simulations towards increased temperature and a decrease in precipitation, in particular during spring and the western part of North Africa. A decrease in actual evapotranspiration, highly correlated to the decrease in precipitations, is observed throughout the study area. On the opposite, an increase in reference evapotranspiration is observed, with similar changes between HAR and PM equations, indicating that the main driver of change is the temperature increase. Since the catchments are rather water-limited than energy-limited, despite opposite projections for actual and reference evapotranspiration a decrease of water availability is projected for all basins under all scenarios, with a strong east-to-west gradient. The projected decrease is stronger when considering reference evapotranspiration rather than actual evaporation. These pessimistic future projections are an incentive to adapt the current management of surface water resources to future climatic conditions.     

Intrinsic flame resistance of polyurethane flexible foams: Unexpectedly low flammability without any flame retardant

Virgin polyurethane flexible foams are widely assumed to be highly flammable materials. The flammability of three model polyurethane flexible foams suggests that this may not be universally true. Two of them show unexpectedly low flammability in the limiting oxygen index test and pass flammability tests such as FMVSS 302 and FAR 25.853. Cone calorimetric measurements at 25 kW/m² and 50 kW/m² furthermore show a high resistance against ignition and demonstrate the self‐extinguishing properties of these two virgin, flame‐retardant‐free, polyurethane flexible foams.     

A combined high and low spatial resolution approach for mapping snow covered areas in the Atlas mountains

Dynamics of snow in semi‐arid mountains are poorly investigated despite the fact that snow may represent an important source of water for downstream populations especially in the spring and early summer. Data acquired by space‐borne optical sensors (i.e. reflectance and derived snow indices) may be suitable for spatial and temporal monitoring of snow cover. However, due to prevailing terrain and climatic conditions, the use of satellite sensor data to monitor snow dynamics is not trivial over such regions. Snowfall as well as precipitation are characterized by strong space–time variability. Indeed snow can fall and melt within one week. Under such conditions, appropriate monitoring of snow dynamics requires space instruments that provide data with high spatial and high temporal resolutions. In this context we developed a new approach based on the combination of two types of instruments: low spatial and high temporal resolution (Système Pour l'Observation de la Terre (SPOT)‐VEGETATION) and high spatial and low temporal resolution (Landsat Thematic Mapper). This new approach improves the relationship between snow index and snow area. The method is validated against snow maps derived from classification of high spatial resolution data on the Atlas range, in Morocco. It is then applied to a one‐year series of SPOT‐4 VEGETATION images allowing to derive a temporal snow cover profile at 1?km spatial resolution over the entire Atlas. The yearly snow profile obtained is of great interest for hydrological modelling.     

Validation of a novel algorithm for the adaptive calculation of transient stratified flow of gas,oil and water in pipelines

In this paper, a mathematical model for three‐phase flow in pipelines is developed and a novel algorithm for solving the resulting system of partial differential equations is presented. The numerical solution is based on an adaptive mesh refinement technique. Significant gains in the numerical performance have been achieved by using this technique combined with high‐resolution schemes like FCT. This approach is highly beneficial in terms of speed while preserving accuracy. An explicit adaptive numerical solver adaptive conservation law solver (ACLS) has been developed in fortran90 using object‐oriented methods, which give a modular and flexible code. Some numerical tests are performed to show the good behaviour of this solver and to compare the numerical results against the experimental data. Copyright © 2001 John Wiley & Sons, Ltd.     

Impact de la décharge publique de Marrakech (Maroc) sur les ressources en eau

Résumé. Les lixiviats de la décharge publique de Marrakech, qui ne sont ni collectés ni traités, pourraient constituer une source potentielle de pollution des eaux de la nappe phréatique et de celles de l'oued Tensift situé près de la décharge. Le but de cette étude est de caractériser ces lixiviats et de déterminer le degré de pollution des eaux à proximité de la décharge. Les analyses physico-chimiques des lixiviats ont montré qu'ils présentent des concentrations élevées en Cl^–, HCO₃ ^–, Na⁺, K⁺, SO₄ ^2–, Ca²⁺, Mg²⁺, NH₄ ⁺, Cu et Pb. La pollution organique est également importante; la DCO peut atteindre 138.000 mg/l O₂. Les concentrations en certains polluants sont nettement supérieures à celles généralement rencontrées dans d'autres décharges d'ordures ménagères. Le suivi de la qualité des eaux durant l'année 1999, a montré que les eaux souterraines et celles de l'oued Tensift sont de mauvaise qualité pour les besoins domestiques et pour l'irrigation. L'Analyse en Composantes Principales a montré que la pollution des eaux, par les lixiviats, est essentiellement due à la matière organique, HCO₃ ^–, NH₄ ⁺, Na⁺, Ca²⁺, Mg²⁺, Cl^– et SO₄ ^2–. Electronic Publication     

Performance across different areas of mathematical cognition in children with learning difficulties.

The performance of 210 2nd graders in different areas of mathematical cognition was examined. Children were divided into 4 achievement groups: children with difficulties in mathematics but not in reading (MD-only), children with difficulties in both mathematics and reading (MD/RD), children with difficulties in reading but not in mathematics, and children with normal achievement. Although both MD groups performed worse than normally achieving groups in most areas of mathematical cognition, the MD-only group showed an advantage over the MD/RD group in exact calculation of arithmetic combinations and in problem solving. The 2 groups did not differ in approximate arithmetic and understanding of place value and written computation. Children with MD-only seem to be superior to children with MD/RD in areas that may be mediated by language but not in ones that rely on numerical magnitudes, visuospatial processing, and automaticity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Achievement growth in children with learning difficulties in mathematics: Findings of a two-year longitudinal study.

The reading and mathematics growth of 180 children was examined over 4 points, spanning 2nd and 3rd grades. Initially, 4 achievement groups were identified: difficulties in mathematics but not in reading (MD only), difficulties in mathematics as well as in reading (MD-RD), difficulties in reading hut not in mathematics (RD only), and normal achievement in mathematics and in reading. When IQ, income, ethnicity, and gender were held constant, the MD-only group grew at a faster rate in mathematics than did the MD-RD group. In reading, the RD-only and MD-RD groups grew at about the same rate. Reading abilities influence children's growth in mathematics, but mathematics abilities do not influence children's growth in reading. (PsycINFO Database Record (c) 2010 APA, all rights reserved)