Studying the effect of changing some factors influencing the stability of the bituminous concrete facing used in tightening dams under Syrian circumstances

Asphalt concrete was used for the first time in Syria as a tightening material for dam Sourani. It was used in this dam as a surface facing on the front slope. Use of asphaltic concrete under climatic conditions prevailing in Syria, particularly high temperatures, is discussed in the paper. To achieve this goal, a number of bituminous concrete mixes, designed using the same constituent components in Sourani dam, were experimentally tested and analyzed. To determine the effect of the expected maximum temperatures for Sourani dam, a program depending on Energy balance was developed. Possible methods of reducing the effect of the high temperature in order to increase the stability of the asphalt surface facing are analyzed. In this context, the facing was plastered by a light-color, which led to a decrease in the temperature of the asphalt surface facing by about 20 degrees Celsius. The facing was also plastered by placing a concrete layer above it, which led to a decrease in the temperature of the asphalt surface facing by about 25 degrees Celsius.

Estimation of Evapotranspiration of Palmyra Oasis by Energy Balance method «Analaitical and Experemental Study»

Continuous calculations of evapotranspiration (LE) using eddy covariance method and energy budget were performed over more than one year above the heterogeneous canopy of an arid oasis ecosystem in the central Syrian desert. Irrigation practice was traditional flooding with a 28 days turn of water delivery. The work focuses on seasonal variations of energy budget over a 2 years period with emphasis on effects of rainfall, wind speed and radiative budget on evapotranspiration. Maximum evapotranspiration was only 5mm/day. Even under irrigation practices, winter rainfall seems to have an important impact on LE: comparisons of two situations in June 2002 and June 2003 showed an increase of 13% in values of LE/Rn-G. Maximum averaged hourly values of evapotranspiration were found for wind speed values closed to 3m/s. This suggests that when the evaporative demand from the air (or vapour pressure deficit (vpd) ) is increasing above a certain limit, the vegetation closes its stomata and reduces transpiration. Results from the energy balance closure showed significant differences in the slope of H+LE against Rn-G relationships between cold and hot month which was explained by specific radiative budget of desert areas.