25 research outputs found

    A method to assess annual average renewable groundwater reserves for large regions in Spain

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    This paper proposes a method for assessing the groundwater renewable reserves of large regions for an average year, based on the integration of the recession curves for their basins springs or the natural base flow of their rivers. In this method, the hydrodynamic volume (or renewable reserves), were estimated from the baseflow equation. It was assumed that the flow was the same as the natural recharge, and that the recession coefficients were derived by the hydrogeological parameters and geometrical characteristics of aquifers, and adjusted to fit the recession curves at gauging stations. The method was applied to all the aquifers of Spain, which have a total groundwater renewable reserve of 86,895 hm3 four times the mean annual recharge. However, the distribution of these reserves is very variable; 18.6% of the country aquifers contain 94.7% of the entire reserve

    Automatic extraction of shorelines from Landsat TM and ETM+ multi-temporal images with subpixel precision

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    A high precision geometric method for automated shoreline detection from Landsat TM and ETM+ imagery is presented. The methodology is based on the application of an algorithm that ensures accurate image geometric registration and the use of a new algorithm for sub-pixel shoreline extraction, both at the sub-pixel level. The analysis of the initial errors shows the influence that differences in reflectance of land cover types have over shoreline detection, allowing us to create a model to substantially reduce these errors. Three correction models were defined according to the type of gain used in the acquisition of the original Landsat images. Error assessment tests were applied on three artificially stabilised coastal segments that have a constant and well-defined land-water boundary. A testing set of 45 images (28 TM, 10 ETM high-gain and 7 ETM low-gain) was used. The mean error obtained in shoreline location ranges from 1.22 to 1.63. m, and the RMSE from 4.69 to 5.47. m. Since the errors follow a normal distribution, then the maximum error at a given probability can be estimated. The results confirm that the use of Landsat imagery for detection of instantaneous coastlines yields accuracy comparable to high-resolution techniques, showing the potential of Landsat TM and ETM images in those applications where the instantaneous lines are a good geomorphological descriptor. © 2012 Elsevier Inc.The authors appreciate the financial support provided by the Spanish Ministerio de Ciencia e Innovacion and the Spanish Plan E in the framework of the Projects CGL2009-14220-C02-01 and CGL2010-19591.Pardo Pascual, JE.; Almonacid Caballer, J.; Ruiz Fernández, LÁ.; Palomar-Vázquez, J. (2012). Automatic extraction of shorelines from Landsat TM and ETM+ multi-temporal images with subpixel precision. Remote Sensing of Environment. 123:1-11. doi:10.1016/j.rse.2012.02.024S11112

    El medio ambiente en las organizaciones internacionales

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    Directory of international agencies for environment, with their composition, objectives, structure, programs, activities, publications, members, etcCentro de Informacion y Documentacion Cientifica (CINDOC). C/Joaquin Costa, 22. 28002 Madrid. SPAIN / CINDOC - Centro de Informaciòn y Documentaciòn CientìficaSIGLEESSpai

    Medida de contaminantes quimicos ambientales. Tecnicas cromatograficas y afines

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    Centro de Informacion y Documentacion Cientifica (CINDOC). C/Joaquin Costa, 22. 28002 Madrid. SPAIN / CINDOC - Centro de Informaciòn y Documentaciòn CientìficaSIGLEESSpai

    Medida de la contaminacion atmosferica procedente de centrales termicas. Medida de emisiones

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    Centro de Informacion y Documentacion Cientifica (CINDOC). C/Joaquin Costa, 22. 28002 Madrid. SPAIN / CINDOC - Centro de Informaciòn y Documentaciòn CientìficaSIGLEESSpai

    Skid resistance prediction for new two-lane roads

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    Skid resistance is a vital issue in pavement management, mainly in relation to road safety; hence, road agencies must assure a minimum friction level of their road networks. The regional government of Biscay (Spain) uses a sideways force coefficient routine investigation machine to assess the present pavement surface condition and to allocate the available funding better. The aim of this paper is to develop a deterioration model to predict the minimum skid resistance in the rural two-lane bituminous roads of Biscay by means of the factors that affect it. In an attempt to include all possible variables that could influence the friction, 23 sections of new roads in Biscay, constructed over the last 25 years, were selected, with different pavement structures (flexible and semi-rigid pavements), ages, surface layers and traffic volumes; a multiple linear regression was then performed. It was concluded that only the average annual daily traffic of heavy vehicles and the required minimum polished stone value of aggregates reflect their importance and, consequently, they are the only variables introduced in the model. The age of pavement, total thickness of bituminous layers and average annual daily traffic of all vehicles showed no influence and were discarded. The proposed model can forecast future skid resistance
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