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Soil degradation is one of the greatest challenges faced by arid and semiarid zones, as it causes a progressive loss of the capacity of soils to sustain life and human activities. In the present study, five spectral indices, individually associated with erosion, desertification, salinity, and soil sealing, were evaluated in a semi-arid region of the Ecuadorian Andes to study of soil degradation. The results were validated through field observations and samples processed in the laboratory. The spectral indices presented correlation coefficients between 0.5278 and 0.8809 with field observations. These indices provided useful information to understand the current state of the soils and their potential deterioration. The study area showed greater vulnerability to erosion caused by the combination of scarce vegetation, irregular topography, and significant seasonal rainfall. The advance of urbanization, mechanized agriculture, and overgrazing had a high impact by impermeabilizing considerable surfaces, while the advance of desertification and soil salinization showed little incidence in the study area. The systematic application of these indices would become a valuable means for monitoring soil degradation in Andean watersheds. [ABSTRACT FROM AUTHOR]

Copyright of Revista Avances: Investigación en Ingeniería is the property of Universidad Libre, Facultad de Ingenieria and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Tecnología y Ciencias del Agua is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In South America the density of meteorological and hydrological stations is low with a minimum number of monitored variables; this limits the application of complex hydrological models for the study of water resources. An alternative may be to use simplified models that need a small number of variables. The study performance of simplified models in scarce information conditions is important in order to know water resources availability in areas with these conditions. The performance of the Temez lumped model and the SWAT model (semi-distributed model) were evaluated with data from six basins at the border region between Ecuador and Peru, with areas that vary between 200 and 2642 km2. Precipitation and temperature recorded in 43 climatological stations in the study area were considered. The model calibration and validation was performed with different portions of the observed data and these were chronologically selected (70 % for modeling 30 % for validation). The Temez model was able to reproduce flows with a Nash-Sutcliffe efficiency of 0.63. The limitations may be attributed to the low station density, to the poor quality of the information, and to the difficulty of representing with a single lumped parameter, characteristics that have a wide spatial variation. The SWAT model showed better simulation capabilities with a Nash-Sutcliffe efficiency of 0.87. The Temez model presemted simulation capabilities lower to those of SWAT; however, in small catchments the ability of both models could be comparable. [ABSTRACT FROM AUTHOR]