Review of: "Assessment of soil erosion in the Cesar watershed, an initial step toward the restoration of the Cesar River (original) (raw)

PREDICTING RISK OF SOIL EROSION AT THE ALQUEVA DAM WATERSHED

Accelerated soil erosion is among the most pressing of environmental problems, which leads to decline in soil quality and productivity, resulting in degradation of ecosystem function. The Mediterranean regions are particularly exposed to erosion, because are subject to extensive dry periods followed by heavy erosive rains falling on steep slopes characterized by fragile soils. Alqueva is Portugal and Western Europe’s largest dam, but the capacity cannot be maintained due to a yearly deposition of sediment in the reservoir. Mapping erosion risk in the Alqueva dam watershed is increasingly needed to safeguard water resources and prevent the accelerated dam siltation, taking into account the possible land-use changes, due to tourism development, intensification of irrigated farming and biomass production, as well as climate change. The main objective of the present work is to use the Revised Universal Soil Loss Equation (RUSLE) in combination with Geographic Information System (GIS) and geostatistical techniques, to model the actual potential soil erosion in this watershed. Soil data, land use inventory, digital elevation data, and climate data are used as resource data sets to generate RUSLE factor values. Graphical interpretation of each factor is performed using ordinary kriging. After that, we use spatial modeling to develop a final overlay map for potential soil erosion using RUSLE. The average rainfall erosivity factor was found to be 1227 MJ mm ha-1 h-1 year in the study area and the soil erodibility between 0.007-0.041 t ha h ha-1 MJ-1 mm-1. The elevation in this area ranges between 145-215 meters and the slope average is 5.4%. Currently, there are three types of soil cover in the study area: 77% of agro-forestry areas, 20% of broad-leaved forest and 3% of wetlands. The overlay results show a soil loss with an annual average of 22.9 t/ha, ranging from 0 to 274.2 t/ha, with the highest values occurring in the southwest part of the experimental area. The highest values are associated mainly to high slopes, high soil erodibility and land-use. The terrain with serious erosion (higher than 50t/ha) cover about 7.5% of area. These areas require especially attention because are suspect to have more susceptibility to erosion. The final prediction maps for soil erosion will be important for estimation of the optimal area for different future land-use alternatives, and will be used as a solid base to create a Decision Support System so as to provide site specific methods and measures for decision-makers. These methods and measures could decrease the risk of soil erosion, helping spend less money, increasing the dam’s life span, promoting for sustainability of the ecosystems.

Temporal dynamics of soil susceptibility to erosion in semiarid watersheds

Acta Scientiarum. Agronomy, 2021

The intensification of anthropogenic activities on soils contributes to soil loss through erosion. Moreover, the pattern of soil loss in the Cobra River watershed, located in the semiarid region of Rio Grande do Norte, is related to the history of land use and occupation, mainly from agriculture and the red ceramic industry, as well as the climatic seasonality of the region. Thus, the objective of this work was to identify the pattern of soil loss from the Cobra River microbasin in the state of Rio Grande do Norte. For this, the following analyses were performed: a survey of land use class areas for the years 1987, 1997, 2007 and 2017 as part of the Mapbiomas project; estimation of basin soil loss for these years; and quantification of areas of erosion vulnerability classes for this period. QGIS software was used to treat georeferenced data. According to the results, the land cover classes in the rich Cobra River microbasin fluctuated over time. Potential soil loss from the watershe...

The Effect of Land Use on Soil Erosion in the Guadiana Watershed in Puerto Rico

1998

A BSTRACT .-The Revised Universal Soil Loss Equation (RUSLE) was used in conjunction with a Geographic Information System to determine the influence of land use and other environmental factors on soil erosion in the Guadiana watershed in Puerto Rico. Mean annual erosion, suspended sediment discharge, and the rainfall-erosion factor of the RUSLE increased with annual rainfall. Median soil erosion rates varied among the seven land uses: bare soil (534 Mg ha -1 yr -1 ), open canopy forest (26 Mg ha -1 yr -1 ), agriculture (22 Mg ha -1 yr -1 ), pasture (17 Mg ha -1 yr -1 ), less dense urban (15 Mg ha -1 yr -1 ), closed canopy forest (7 Mg ha -1 yr -1 ), and dense urban (1 Mg ha -1 yr -1 ). The differences between open canopy forest, agriculture, pasture, and less dense urban were not significantly different but median values for open canopy forests were slightly greater because they occurred on steep slopes. The five-year average sediment delivery ratio for the basin was 0.17, which is comparable to delivery ratios estimated for watersheds of similar size. Simulations of different land use configurations indicate that reforestation of 5% of the watershed with the highest erosion rates would decrease basin wide erosion by 20%. If the entire watershed was reforested, soil erosion would be reduced by 37%. R ESUMEN .-Se utilizó la versión revisada de la Ecuación Universal de Pérdida de Suelo (RUSLE, según sus siglas en ingles), en conjunto con Sistemas de Información Geográfica, para determinar la influencia del uso del terreno y otros factores ambientales sobre la erosión del suelo en la cuenca hidrográfica del Río Guadiana en Puerto Rico. La erosión promedio anual, la descarga de sedimento suspendido y el factor lluvia-erosión de RUSLE aumentaron según aumentó la precipitación anual. Se encontró una variación entre las medianas de las tasas de pérdida de suelo respecto a las siete clases de uso de terreno: suelo expuesto (534 Mg ha -1 año -1 ), bosque de dosel abierto (26 Mg ha -1 año -1 ), agricultura (22 Mg ha -1 año -1 ), pastizal (17 Mg ha -1 año -1 ), urbano menos denso (15 Mg ha -1 año -1 ), bosque de dosel cerrado (7 Mg ha -1 año -1 ) y urbano denso (1 Mg ha -1 año -1 ). No se encontró diferencia significativa entre el bosque de dosel abierto, agricultura, pastizales y urbano menos denso, pero los valores de las medianas del bosque de dosel abierto fueron mayores porque este uso de terreno ocurre en pendientes más escarpadas. El promedio para los cinco años de estudio de la razón de sedimento que llega al río fue 0.17, el cual es comparable con la razón estimada para cuencas hidrográficas de igual tamaño. Simulaciones diferentes de uso de terreno indican que reforestar el 5% de las áreas de la cuenca donde la erosión es mayor disminuiría la erosión en la cuenca en un 20%. Si se reforestara la cuenca por completo, la erosión del suelo disminuiría en un 37%.

Predicting soil erosion risk at the Alqueva dam watershed

Spatial and Organizational Dynamics …, 2012

Soil erosion is serious economic and environmental concern. Assessing soil erosion risk in the Alqueva dam watershed is urgently needed to conserve soil and water resources and prevent the accelerated dam siltation, taking into account the possible land-use changes, due to tourism development, intensification of irrigated farming and biomass production, as well as climate change. A comprehensive methodology that integrates Revised Universal Soil Loss Equation (RUSLE) model and Geographic Information Systems (GIS) with geostatistical techniques was adopted to study different land-use and management scenarios. The main objective of this study stage is to determine the soil erosion vulnerability of an agro-silvo pastoral system. The resultant soil erosion map shows an average of 14.1 t/ha/ year, with serious erosion risk (higher than 50 t/ha/year) in 4.3% of area. The highest values are associated mainly to high slopes and low vegetation. The final prediction maps for soil erosion and for each factor considered, can be used as a solid base to create a Decision Support System so as to provide specific procedures for decision-makers, promoting for sustainability of the ecosystems, reducing the risk of erosion and consequently increase lifetime of dam, under various land use and management scenarios.