WATER EROSION

Author: VILA GARCÍA ROBERTO.
Year: 2004.
University: SANTIAGO DE COMPOSTELA [www.usc.es].
Place of defense: FACULTAD DE XEOGRAFÍA E HISTORIA.
Place of preparation: FACULTADE DE XEOGRAFÍA E HISTORIA.

Summary: Assuming that the overall erosion is a serious and emerging environmental process degradativo is to quantify the magnitude of erosion processes in Galicia under traditional tillage. By revising bibliografica are marked 4 goals: first corroborate the effects erosicos in different cultivos.Segundo investigate hydrological processes and the physics of precipitaciones.Tercero know the threshold of generating runoff and fourthly verify the various factors influencing the losses Soil. Empirical research takes place in the Experimental Station Mount Pedroso (EEMP) through the design and construction of sample plots. Rainfall is analyzed according to its frequency peak in 24 hours and each 10min.A through the calculation of rates aggressiveness (Hudson KE lower 25: Morgan KE lowest 10: Wischmeier EI30; USLE R; Lal (AI7, 5); Arnaldus Q2 / P Oliver (ICP) is calculated aggressiveness and intensity of rainfall and put under the hydrography year. Calculation of the ETP by him Penman method; Penman Monteith and FAOModifed Penman daring the conclusion that the former is which got the lowest values in mm but not the best settings. development of water balance on the model proposed by Thorthwaite and Mather showed the presence of effective precipitation during the study period and shows the ability of field soil registered securities negative always during the summer season. surface runoff are conditioned by the presence of moisture entecedente (70% of the days of the calendar year), which determines the increase in the runoff of maner slight paulatina.Si but there is a lack of moisture background direct decreasing runoff and increasing runoff suterráneas, whatever land use and development phase of the crop. losses were influenced by the soil soil management to the point where antecedent moisture over a larger volume of runoff although during the stage of crop rotation, without cobertuara plant happens expecionalmente that escorretías respond to the precipitation before the antecedent moisture is representative and on the other side with plant coverage exceeding 70% peaks very important runoff due to moisture antecedente.La rotation cultivation supposed l aeliminación of vegetation cover implies a period of continuous erosion risk until it is not again reach the 30% extension. losses of soil are affected by a variety of processes and factors, but the higher rates erosion occurs under cultivation turnip, as it is a long-cycle crops and accounts for between 50 and 75% of the annual precipitation. A value of soil loss for the puedad regarded as tolerable should be tailored to each ground particularly for Galicia and Western T-factor acceptable to be placed around 2 Mt. a year (which implies a lower maximum of 0.1 mm. year).

Author: FARGUELL PÉREZ JOAQUIM.
Year: 2004.
University: BARCELONA [www.ub.es].
Place of defense: FACULTAD DE GEOGRAFÍA I HISTÒRIA.
Place of preparation: UNIVERSITAT DE BARCELONA.

Summary: SUMMARY: Laproducciónde sediment suspension is the most importanteque cause rivers to the oceans and seas of the world. The study was conducted in the river basin Anoia, a tributary delllobregat, in Catalonia. The surface drainage basin is 926 km2de surface and have chosen two points for the dinámíca sediment compare and their characteristics throughout the cuneca. Estimates have been made on the field sampling weekly sampling during low flow rates and also during floods so much more prevalent. The amount of suspended sediment is related to the amount of flow and also with the land uses and activities in the watershed. One of the elements that are used in the calculation and estimation of sediment are suspended sediment concentrations. These són subjected to extreme variability depends on the flow of the season, and the variacienos histeréticas within their own episodes of flooding. At the river basin Anoia these concentrations are higher in the bottom of the basin in its upper part, and are subject to wide variation gives according to the various types of flood. Episodes of multiple peaks generate large hysteresis that produce a wide dispersion in the data. The average concentrations are 300 mgll in the headwaters of the river and 1200 mgll in the bottom. The maximum values ranging from 4000 mg / l and the 15000 mg / l. Particle size is also a basic feature to be considered in the sediment in suspensón. In the basin of the river Anoia it has been determined that it is located in the area of silt and clay. The dynamics of particle size, but not well-established its relations with the flow, indicates that this increases with the flow in the headwaters of the river and reduces the flow at its bottom due to the entry of sources of sediment gauge finest . Finally, the total amount of production of sediment in the river Anoia is 2200 tonnes during the study period in the upper river and 100000 t at the bottom. Different amounts and the fact that the peak will occur in different years indicates that the sections header and bottom do not keep any type of relationship.