Land degradation assessment: tools and techniques for measuring sediment load

The assessment of land degradation through the use of tools and techniques is discussed for the measurement of sediment load in regions of great agricultural potential, such as the Paraná river basin. Land degradation for these prominent agricultural regions is defined as being the actions in land that decreases potential crop production over time. Assessment of land degradation by erosion (soil loss by water, e.g. topsoil removal, rilling and gullying), chemical (carbon and nutrient depletion) and physical degradation (soil compaction and disaggegation, emergence of subsoil with poor physical properties) and the causes of degradation (deforestation, overexploitation, overgrazing and agricultural activities) in these regions are addressed. The effects of land degradation through water erosion and its subsequent impact on rivers and reservoirs downstream are presented through the use of modeling tools and techniques. A methodology for the utilization of models such as the Revised Universal Soil Loss Equation (RUSLE) or the Water Erosion Prediction Project Model (WEPP) to assess the risk of land degradation in large scale agricultural lands is presented as well as the techniques used for continuous monitoring. Issues and problems with the adaptation of a small scale erosion models to function as a large scale risk assessment tools are also addressed. The integration of these models with tools such as geographic information system (GIS) and the use of various thematic maps derived from satellite imagery and land surveys to feed the models is an essential part of this methodology. The identification of high degradation risk areas will allow for better soil conservation planning where programs can be implemented to maintain a sustainable non-degrading agricultural system and thus, reduce the sediment load into rivers and lakes in the region of interest

Monitoring the sediment loading of Itaipu Lake and modeling of sheet and rill erosion hazards in the watershed of the Parana River: an outline of the Project

The Itaipu hydroelectric project, the worlds largest, did not have a problem with sediment loading initially and was expected to have a life of +300 yr. Since, landuse change from forest to crops increased sediment to the lake. This change caused a reduction in quality of aquatic habitat, reduced capacity, and shortened the project life. To determine the extent of sedimentation and target areas producing sediment, a study began to monitor sediment flux, and model the watershed to determine those areas to concentrate conservation efforts. A methodology was developed which includes: 1) Monitoring major tributaries with a network of gauging stations and turbidity meters. 2). Measuring stage height and developing calibration curves relating height to discharge. 3). Measuring turbidity and calibrating to sediment load. These measurements will be digitally recorded and allow computation of water and sediment flux hourly to the lake. Modeling will use the Revised Universal Soil Loss Equation (RUSLE) in a Geographic Information System (GIS). RUSLE erosivity (R) will be collected from a network of climatic stations, erodibility maps (K) from existing data, topographic (LS) data from digital elevation models (DEM) and cropping and management (C and P) from remote sensing and field plots. These parameters will allow predicting erosion spatially in a GIS. Monitoring will be compared to predictions on smaller watersheds to calibrate the RUSLEIGIS model. The calibrated model will be used to develop erosion potential maps for the watershed. The impact of this project is a prediction of the effect that land-use change has had on the project life and areas can be targeted for conservation efforts to protect the project life