Análisis morfológico del Río Pilcomayo en la zona de la embocadura

La zona de la Embocadura en el Río Pilcomayo, se corresponde con una bifurcación del mismo que reparte las aguas hacia Argentina y Paraguay. Se localiza en el extremo noroeste de la provincia de Formosa, Argentina. Este sector del Río Pilcomayo presenta una marcada inestabilidad desde el punto de vista morfológico. A pesar de ello, la necesidad de captar agua del río por parte de Argentina y Paraguay, ha motivado la realización de una serie de intervenciones en esta zona durante los últimos 25 años. En la actualidad existen convenios entre ambos países de los que surge el compromiso de realizar acciones coordinadas tendientes a lograr un reparto equitativo de las aguas y los sedimentos.La finalidad de este estudio es hacer una evaluación de los cambios que la planta del cauce experimentó en los últimos tiempos, y ubicar sectores que eventualmente puedan tener una mayor estabilidad. En principio, las obras de repartición debieran localizarse en estos sitios para que puedan cumplir con los compromisos de ambos países de manera estable en el tiempo.Fil: Irigoyen, M. Instituto Nacional del Agua; Argentina.Fil: Irigoyen, M. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentina.Fil: Spalletti, P. Instituto Nacional del Agua; Argentina.Fil: Spalletti, P. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentina.Fil: Brea, D. Instituto Nacional del Agua; Argentina.Fil: Brea, D. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentina.Fil: Hillman, G. Universidad Nacional de Córdoba. Facultad de Ingeniería. Laboratorio de Hidráulica; Argentina.Fil: Gyssels, P. Universidad Nacional de Córdoba. Facultad de Ingeniería. Laboratorio de Hidráulica; Argentina.Fil: Baldissone, C. Instituto Nacional del Agua; Argentina.Fil: Rodríguez, A. Universidad Nacional de Córdoba. Facultad de Ingeniería. Laboratorio de Hidráulica; Argentina.Ingeniería Civi

Impact of plant roots on the resistance of soils to erosion by water: A review

29 páginas, 14 figuras, 4 tablas.Vegetation controls soil erosion rates significantly. The decrease of water erosion rates with increasing vegetation cover is exponential. This review reveals that the decrease in water erosion rates with increasing root mass is also exponential, according to the equation SEP =e(-bRP) where SEP is a soil erosion parameter (e.g., interrill or rill erosion rates relative to erosion rates of bare topsoils without roots), RP is a root parameter (e.g., root density or root length density) and b is a constant that indicates the effectiveness of the plant roots in reducing soil erosion rates. Whatever rooting parameter is used, for splash erosion b equals zero. For interrill erosion the average b-value is 0.1195 when root density (kg m(-3)) is used as root parameter, and 0.0022 when root length density (km m(-3)) is used. For rill erosion these average b-values are 0.5930 and 0.0460, respectively. The similarity of this equation for root effects with the equation for vegetation cover effects is striking, but it is yet impossible to determine which plant element has the highest impact in reducing soil losses, due to incomparable units. Moreover, all the studies on vegetation cover effects attribute soil loss reduction to the above-ground biomass only, whereas in reality this reduction results from the combined effects of roots and canopy cover. Based on an analysis of available data it can be concluded that for splash and interrill erosion vegetation cover is the most important vegetation parameter, whereas for rill and ephemeral gully erosion plant roots are at least as important as vegetation cover.This research is funded by the Institute for the Promotion of Innovation by Science and Technology in Flanders (Belgium) and by the European Commission, Directorate-General of Research, Global Change and Desertification Programme, RECONDES project (Conditions for Restoration and Mitigation of Desertified Areas using Vegetation) no. GOCE-CT-2003- 505361. Maurice De Proft, Mark Nearing and Aleksei Sidorchuk are thanked for providing valuable background information.Peer reviewe

Effects of double drilling of small grains on soil erosion by concentrated flow and crop yield

International audienceSoil erosion on agricultural land and its detrimental environmental and economical effects has aroused increased interest among both the research and policy-making communities. The call for erosion control measures adapted to local farming practices is high, especially in Europe where farmers are reluctant to adopt soil conservation techniques. This study investigates a new technique for controlling concentrated flow erosion rates in the loess belt of central Belgium: i.e. double drilling of cereals in zones of concentrated flow. Cross-sectional areas of erosion channels as well as crop yield parameters in single- and double-drilled zones were compared. The technique is based on the combined effect of the increased density of plant shoots and roots for reducing soil loss. Results indicate that double drilling can reduce soil loss through concentrated flow by 25% on average and by up to 40% under optimal conditions. No net change in wheat grain yield was observed, and farmers who participated in the experiments were satisfied with the results and the easy application of the technique. Globally, benefits were larger than costs. However, the effectiveness of the technique in reducing soil loss by concentrated flow erosion seems to be topographically restricted. For positions in the landscape with a contributing drainage area larger than ca. 0.75 ha, the effectiveness of double drilling can be doubted. Double drilling should therefore be regarded as one possibility amongst others to reduce concentrated flow erosion rates in farmers' fields

Effects of cereal roots on detachment rates of single- and double-drilled topsoils during concentrated flow

Farmers in Europe want to control soil erosion in ways that are easily incorporated in their normal practices. We have investigated the possibility of reducing soil erosion by concentrated flow (i.e. rill and gully erosion) through increasing the root density of cereal crops. In situ root density measurements on cereal fields were combined with laboratory flume experiments on samples, taken in single- and double-drilled fields, of which the above-ground biomass was clipped. During the laboratory experiments no significant effect of root densities on critical shear stress or channel erodibility was observed because of interactions with other changing parameters (e.g. ageing effects). Therefore, the expected relative detachment rates as a function of plant root density were calculated using an empirical equation. During the first 75 days of the crop growth season relative soil detachment rates for single-drilled field parcels can be reduced up to 50% compared with a rootless field, whereas relative soil detachment rates in double-drilled field parcels can be reduced up to 60% in this period. Thereafter, plant roots in double-drilled field parcels reduce relative soil detachment rates on average by 9% compared with single-drilled field parcels (up to an absolute maximum of 90% compared with rootless soils). During the growing season, not only root density increases but also the vegetation cover changes, which enhances soil protection from erosion. Therefore, cereal roots will help to conserve the soil when seed is drilled at double rates, especially during the early growth stages and in fields with medium risk of concentrated flow.status: publishe

Modelación hidrodinámica de las intervenciones sobre el Río Pilcomayo en la zona de la embocadura

Fil: Baldissone, C. M. Instituto Nacional del Agua; Argentina.Fil: Gyssels, P. Universidad Nacional de Córdoba. Centro de Estudios y Tecnología del Agua; Argentina.Fil: Spalletti, P. Universidad Nacional de La Plata. Facultad Ingeniería; Argentina.Fil: Hillman, G. Universidad Nacional de Córdoba. Centro de Estudios y Tecnología del Agua; Argentina.Fil: Brea, D. Universidad Nacional de La Plata. Facultad Ingeniería; Argentina.Fil: Irigoyen, M. Universidad Nacional de La Plata. Facultad Ingeniería; Argentina.Fil: Testa Tacchino, E. Universidad Nacional de Córdoba. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Rodriguez, A.Universidad Nacional de Córdoba. Centro de Estudios y Tecnología del Agua; Argentina.El Río Pilcomayo, que discurre en el límite entre Paraguay y Argentina, está afectado a convenios en los cuales ambos países se comprometen a llevar acciones coordinadas para lograr el reparto equitativo de las aguas y sedimentos. La zona donde actualmente se materializa la bifurcación está a unos 25 km aguas abajo de la entrada del río a la provincia argentina de Formosa, allí un canal sobre la margen izquierda deriva las aguas hacia territorio paraguayo recibiendo la denominación de "Embocadura". La alta inestabilidad fluvial propia de éste sistema particular y diferencias de mantenimiento en ambos cauces (Canal paraguayo y río Pilcomayo aguas abajo de éste último), han motivado que desde mayo de 2012, en temporada de caudales bajos, las aguas del río discurran íntegramente por el canal paraguayo, impidiendo el cumplimiento de los acuerdos firmados.Fil: Baldissone, C. M. Instituto Nacional del Agua; Argentina.Fil: Gyssels, P. Universidad Nacional de Córdoba. Centro de Estudios y Tecnología del Agua; Argentina.Fil: Spalletti, P. Universidad Nacional de La Plata. Facultad Ingeniería; Argentina.Fil: Hillman, G. Universidad Nacional de Córdoba. Centro de Estudios y Tecnología del Agua; Argentina.Fil: Brea, D. Universidad Nacional de La Plata. Facultad Ingeniería; Argentina.Fil: Irigoyen, M. Universidad Nacional de La Plata. Facultad Ingeniería; Argentina.Fil: Testa Tacchino, E. Universidad Nacional de Córdoba. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Rodriguez, A.Universidad Nacional de Córdoba. Centro de Estudios y Tecnología del Agua; Argentina.Ingeniería Civi