ABSTRACT:Land cover and spatial variation of seasonal temperature may contribute to different evapotranspiration rates between the European regions. In order to assess the integral effect of land cover and climate on water resources, we implemented a procedure which allows defining favorability areas to high rate of evapotranspiration. Seasonal mean air temperature for the present (2011-2040) and future (2041-2070) combined with the seasonal crop coefficients of current future projections of land cover for the 2040s have been used to evaluate the various degrees of evapotranspiration at European scale. Extremely high and very high degree of evapotranspiration tendency were verified for Southern, Eastern, Western and Central of Europe during the mid-season period. The low and very low evapotranspiration favorability were found in the Scandinavian Peninsula and in the Alps, Dinarics, and Carpathian during the present period in all the seasons. In the cold season, the land cover favorability to evapotranspiration (LCFE) is low and very low in almost the whole Europe. These findings indicate that the southern and western regions of Europe are facing low water availability, decrease in surface water flow, and possible long periods of drought in the summers.
Abstract. Measurement of soil suction is important as soil suction is one of the two stress-state variables that control both the hydro and mechanical behaviour of unsaturated soils. One of the soil suction measurement techniques is the filter paper method. Even though the filter paper technique has been standardized, the experimental procedure can still be improved in order to reduce the inconsistencies that are often reported with the filter paper technique. This paper explores usage of both initially dry and initially moist Whatman No. 42 filter paper for matric and total suction measurements. Residual soils from the Bukit Timah Granite in Singapore were compacted at various water contents from dry to wet of optimum using standard Proctor energies and their suctions were measured using both contact and non-contact filter papers. Results of the suction measurements showed hysteresis between the initially dry and the initially moist filter papers for both the contact and non-contact methods. Suction measurement by the contact filter paper method is more consistent than suction measurement by the non-contact filter paper method. Condensation causes the non-contact filter papers to have higher water contents. The results showed that the non-contact initially dry filter paper follows the total suction curve but the non-contact initially moist filter paper may follow the matric suction curve instead.
Soils at the ground surface experience multiple cycles of drying and wetting. On drying, the soils experience shrinkage and cracks may appear. The development of cracks depends on the tensile strength of the soil. Such cracks increases the permeability of the soil and can cause slopes and earth structures to fail due to rainfall. Several tensile strength models have been proposed for unsaturated soils considering the effect of matric suction. However, the tensile strength models proposed are for either cohesionless (coarse-grained) or clayey (fine-grained) soils. The tensile strength models were shown to be different in their definition of suction stress and the presence or absence of a cohesion term. As tensile strength data of fine-grained soils with the same soil structure and soil-water characteristic curve data are lacking in the literature, Brazilian tensile tests and SWCC tests were conducted on compacted fine-grained soils from two residual soil formations. The test data highlighted the problem in the friction angle used in existing tensile strength models. Using a general form of the suction stress and the extended Mohr-Coulomb criterion with the Brazilian test Mohr circle, a new tensile strength model applicable to both coarse-grained and fine-grained soils was proposed. The proposed model was shown to perform better than existing models using independent data.
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