27 research outputs found
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 ParanĂĄ 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