Estimate Soil Loss Research Articles

Methodological Contribution to the Assessment of Generation and Sediment Transport in Tropical Hydrographic Systems

The efficiency and useful life of reservoirs are directly related to the production and input rates of sediments resulting from erosive processes at the edges and those resulting from the action of surface runoff in contribution areas and transported via tributary channels. Knowledge of the intensity, as well as the relationship between generation and input, allows more precise identification of critical environments, helping in the decision-making process and allowing the definition of mitigating measures. This work aims to relate the spatial variability of soil loss with the respective sediment transfer potential in two sub-basins tributary to the HPP Batalha reservoir in the Midwest region of Brazil. The methodology comprised the bivariate analysis between estimates of soil loss in areas of contribution and the Declivity-Extent Relationship along the channels. The results point to the configuration of four spatial patterns, indicating different levels of criticality in terms of sediment generation potential and transport capacity. In addition, they highlight basins with high potential and greater proximity to the reservoir, which constitute priority areas for monitoring, especially the conditions of soil cover and management, to contribute to the reduction of sediment inputs and prolong the efficiency of these structures.

Estimativa da perda de solo por erosão laminar usando ferramentas computacionais na agricultura de precisão

ABSTRACT The study aimed to identify and evaluate the spatial variability in laminar erosion in areas using precision agriculture tools. Soil data from three properties in the western region of Paraná state, Brazil, were used: one in the municipality of Céu Azul (area A) and two in Serranópolis do Iguaçu (areas B and C). To identify discrepant data (outliers), analysis of the dispersion of quartiles was performed using a box-plot graph. Data normality was verified using the Kolmogorov-Smirnov test. A spatial analysis was performed using AgDataBox-Map software. The parameters of the universal soil loss equation were estimated and used with map algebra to produce a model to identify areas susceptible to erosion. Area A (soil loss estimate = 0-200 t ha-1 per year) presented greater susceptibility to erosion than areas B and C (soil loss estimate = 0-150 t ha-1 per year); however, all areas had a low susceptibility to erosion.

Integrating GIS and remote sensing in mapping soil erosion risk using SLEMSA model: A case study of Dinogeng Agricultural Extension Area of Kgatleng District, Botswana

A study was conducted in Dinogeng Agricultural Extension Area (DAEA) of Kgatleng District, Botswana, with the objective of assessing current soil erosion risk (using 2020 Landsat imagery) resulting from the Integrated Support Programme for Arable Agricultural Development (ISPAAD) that was launched in 2009. The Soil Loss Estimation Model for Southern Africa (SLEMSA) tool integrated with Geographical Information System (GIS) and Remote Sensing assessed the soil erosion risk in the study area. The results indicated that 88% of DAEA has low to moderate soil erosion risk (0 – 2 tha-1yr-1). Only 12% of the study area experience very high to extreme high erosion risk (5 - ≥10 tha-1yr-1) along the streams, at steep slopes and areas of bare land. Common practice calls for conservation measures to be applied on areas with high soil loss. This study has underscored the role of topography and soil erodibility, as natural factors, in driving soil erosion.

Soil Loss Estimation Using Remote Sensing and RUSLE Model in Koromi-Federe Catchment Area of Jos-East LGA, Plateau State, Nigeria

Soil loss caused by erosion has destroyed landscapes, as well as depositing sterile material on fertile lands and rivers, clogged waterways and accelerated flash floods, declined the populations of fish and other species, and diminish soil fertility. In some places, erosion has also destroyed buildings, caused mudflow, create new landforms, displaced people, and slowed down the economy of the affected community by destroying roads and homes. Erosion is aggravated by climate change and anthropogenic factors such as deforestation, overgrazing, inappropriate methods of tillage, and unsustainable agricultural practices. In this study, remote sensing (RS) and geographic information (GIS) data and tools were used to model erosion and estimate soil loss in the catchment area of Koromi-Federe in Jos East, Plateau State Nigeria which is our study area. Soil loss estimation was performed using the revised universal soil loss equation (RUSLE) model and was computed by substituting the corresponding values of each factor inherent in the equation (rainfall erosivity, soil erodibility, slope steepness and slope length, cover management, and conservation practices) using RS and GIS tools. Soil data was obtained from the study area and analyzed in the laboratory, rainfall data, land cover, digital elevation model (DEM), as well as the management practice of the study area were the parameters computed in spatial analyst tool using map algebra based on RUSLE. The soil loss generated was classified into four classes and the results revealed 95.27% of the catchment with a tolerable loss of less than 10 t/h−1/y−1. At 3.6%, a low or minimal loss of 10–20 t/h−1/y−1, at 1.03% there exists a moderate loss of 20–50 t/h−1/y−1, while there was and critical or high loss of >50 t/h−1/y−1 at 0.12% of the catchment. The result showed that critical soil loss in the catchment area is exacerbated by the influence of the slope length and steepness, and the amount of rainfall received. This poses great concern with annual rainfall projected to increase up to 12% in West Africa. However, our sensitivity analysis revealed that it can be reduced with the effect of vegetated cover and management practices. This is an important finding as it can guide sustainability practices to control erosion and the loss of valuable lands in the region, especially now under climate change.

Spatial Estimation of Soil Loss and Planning of Suitable Soil and Water Conservation Interventions for Environmental Sustainability in Northern Karnataka in India Using Geospatial Techniques

The selected study area lies in Karnataka State of Southern India and is frequently subjected to prolonged dry spells, high soil erosion, declining groundwater levels, and reductions in crop yield. In order to make this region sustainable, estimation of soil loss, selection and prioritization of suitable interventions, and its adoption are very important. In this study, spatial soil loss estimation models were developed sub-district-wise using the Revised universal soil loss equation (RUSLE) and GIS for a period of 70 years (1951 to 2020). The observed soil loss data for the period of 2011 to 2015 were used for validation of the model (R2 = 0.89) and were found satisfactory. The average annual rainfall ranged spatially from 420 to 3700 mm, erosivity (R) ranged from 2606 to >15,000 MJ mm ha−1 h−1 year−1, and average annual soil loss varied from <2.0 to >15.0 t ha−1 y−1 in the northern dry zone of Karnataka. Most of the study area had an average annual rainfall of 550 to 800 mm and the soil loss was <10.0 t ha−1 y−1. A higher erosivity and soil loss occurred in the western part of the selected area where high rainfall is predominant. A considerable variability in rainfall, erosivity, and soil loss was found in high, medium, and low-rainfall regions from 1951 to 2020. The spatial soil loss was estimated catchment-wise and prioritized to determine the vulnerable areas. It was found that 7.69% of the area with soil loss ≥ 15.0 t ha−1 y−1 needs top priority for planning interventions (Priority 1) followed by 10.49% of the area with soil loss ranging from 10.0 to 15.0 t ha−1 y−1 (Priority 2) and 42.7% of the area under 5.0 to 10.0 t ha−1 y−1 (Priority 3), and the remaining area has lower priority. In order to make Northern Karnataka more sustainable, suitable site-specific moisture conservation practices and water-harvesting/groundwater recharge structures were planned using geospatial techniques. Among the selected moisture conservation interventions, conservation furrow and contour cultivation are very suitable for all the nine districts followed by compartmental bunding and semi-circular bunds. Out of the total area, conservation furrow was found suitable for 45.3% of the area, contour cultivation for 24.3% of the area, and compartmental bunding and semi-circular bunds for 16.8 and 16.9% of the areas, respectively. The study indicated that a considerable amount of topsoil is lost as erosion and, hence, planning and adoption of suitable in situ soil and water conservation practices and water-harvesting/groundwater recharge structures are the need of the hour for the sustainable management of this region. The identified locations were validated using visual interpretations, ground truth, and recorded data.

Evaluating Soil Loss for Identification of Land Risk Area in the Kabe Watershed of Ethiopia

Soil erosion is the main cause of topsoil loss in farming land, which results in reduction in cropland productivity. Soil loss estimation is crucial for developing soil and water conservation strategies for Ethiopia. The investigation aimed to estimate the soil loss in various intensifications of land use patterns, including slope categories, using the soil estimation model associated with the ArcGIS process. It is analyzed in Ethiopian conditions based on erosivity, soil erodibility, vegetative cover (C) remote sensing data, slop-length factor (LS), and management practices (P). The mean soil loss was relatively high (20.01 t ha−1yr−1) in the cultivated land, whereas it was lowest (0.17 t ha−1yr−1) under forest land. Soil loss in the watershed shows a significant variation under slope classification. Moreover, the land having a greater slope angle, or the upper slope of the watershed, contains maximum soil erosion, while the lower slope position has a minimum soil erosion rate. The validation shows that there is an insignificant variation between the predicted model and the experimental data. Therefore, this confirms that the model can be applied in the study watershed or elsewhere with similar agroecology to the study area. This research is also used to prepare an erosion management strategy for the conservation of soil and water in the watersheds.

Effect of topographic variations and tillage methods on gully erosion in the black soil region: A case‐study from Northeast China

AbstractGully erosion is considered to be a severe land degradation process around the world. The combined effects of tillage methods and topographic variation on gully erosion are poorly understood. This study investigated permanent gullies in three farmland, geomorphic areas in the black soil region of Northeastern China: low mountains and hills, tableland, and rolling hill areas. Cross‐sectional measurements were used to obtain estimates of volumetric soil loss from the gullies. Digital contour maps and remote sensing images were used to obtain the topography and row direction data. The results showed that tableland area had the greatest volumetric soil loss and was the most prone to develop gully erosion, followed by the low mountains and hills, and finally the rolling hill areas. Topography was the dominant control on gully erosion and volumetric soil loss and length density increased first and then decreased as a function of increase of slope gradient. Farmland with slope gradient between 15° and 20° had the most serious gully erosion. Hillslope gullies were classified into three types by morphological indicators. Compared to other geomorphic areas, low mountains and hills had the most gully types and the greatest variability of morphology. Surface areas and volumes were related to gully type. Different tillage methods have affected the frequency of gully occurrence. Cross‐slope tillage areas were more prone to develop gully erosion than contoured tillage and up and down slope tillage areas, especially for farmlands with slope of 5 to 10°. The results suggest that gully erosion could be reduced if up and down slope tillage was used for slope gradients less than 15° and contoured tillage was used for slope gradient greater than 15°. This study demonstrates the combined effect of topographic variations and tillage methods on gully erosion, and highlights the importance of considering different tillage methods under different geographical conditions to control gully erosion.

Soil Loss Potential Assessment for Natural and Post-Fire Conditions in Evia Island, Greece

A devastating forest fire in August 2021 burned about 517 km2 of the northern part of Evia Island, affecting vegetation, soil properties, sediment delivery and the hydrological response of the catchments. This study focuses on the estimation of the annual soil loss in the study area under natural (pre-fire) and post-fire conditions. The assessment of the soil loss potential was conducted with the application of the Universal Soil Loss Equation (USLE), which is an empirical equation and an efficient way to predict soil loss. The USLE factors include rainfall erosivity (R), soil erodibility (K), the slope and slope length factor (LS), the cover management factor (C) and the erosion control practice factor (P). The USLE quantified the annual soil erosion (in t/ha/year) for both pre- and post-wildfire conditions, and the study area has been classified into various soil loss categories and soil erosion intensity types. The results showed that the annual soil loss before the forest fires ranged from 0 to 1747 t/ha, with a mean value of 253 t/ha, while after the fire the soil loss significantly increased (the highest annual soil loss was estimated at 3255 t/ha and the mean value was 543 t/ha). These values demonstrate a significant post-fire change in mean annual soil loss that corresponds to an increase of 114% compared to the pre-fire natural condition. The area that is undergoing high erosion rates after the extreme wildfire event increased by approximately 7%, while the area of moderate rates increased by 2%. The calculated maximum potential of soil erosion, before and after the 2021 extreme wildfire event, has been visualized on spatial distribution maps of the average annual soil loss for the study area. The present study underlines the significant post-fire increase in soil loss as part of the identification of the more vulnerable to erosion areas that demand higher priority regarding the protective/control measures.

Soil loss and erosion potential estimation of Jhimruk watershed, Nepal

Soil erosion will have impact in the land productivity, water resource and watershed as a whole. The loss of top soil leads to land degradation and for an agrarian area like Jhimruk which also known as “The rice bowl of Nepal”, it would be a huge consequence on the land productivity. Therefore, it is essential to know the spatial distribution of the areas susceptible to the degradation and assess the erosion potential to plan effective mitigation measures. The Revised Universal Soil Loss Equation (RUSLE) model was used in a Geographic Information System (GIS) to estimate the soil loss of the Jhimruk watershed, Lumbini Province, Nepal. This research aimed to calculate the erosional soil loss status of the local governments lying inside the watershed. For this, remote sensing data obtained from various sources were used to generate the factor maps to calculate the soil loss through RUSLE. A 13-year mean annual precipitation data from the 8 meteorological stations in and around the watershed were used. The mean annual soil loss of the watershed was found to be 13.4 tons per hectare per year (t/ha/yr). However, the soil loss was calculated to be as high as 182 t/ha/yr. 68.82% of the total area of the watershed lie under very low erosion class and thus, have low conservation priority. On the other hand 7.73% of the total area of the watershed lie under extremely high erosion class and, thus, have a high conservation priority class. The mean erosion rate from the barren land was found to be highest (23.179 t/ha/yr) followed by agricultural (21.40 t/ha/yr) and forest area had the lowest erosion rate, i.e., 7.90 t/ha/yr.

The Significance of Digital Elevation Models in the Calculation of LS Factor and Soil Erosion

This study focuses on the role of topography in soil erosion modelling by examining the impact of topographic data from various sources on the calculation of the slope length and slope steepness factor (LS). For this purpose, the Pinios dam drainage basin in the Ilia Regional Unit, Western Greece, was selected as a pilot area of this study. Specifically, six Digital Elevation Models (DEM) from four different sources with various resolutions (5, 30, and 90 m) were compared with ground control point (GCP) values to assess their relative vertical accuracy. These DEM were acquired for the calculation of the LS factor by using two different equations. Then the calculated LS factors were implemented in the RUSLE model for the estimation of soil loss. The current study includes a comparative analysis of the elevation, the slopes, the LS factor, and the soil loss. The results showed that the 5 m resolution DEM had the best vertical accuracy, and thus it is considered to be the most suitable DEM for soil erosion modelling. Moreover, the comparison of the DEM elevation values showed high similarity, in contrast to the slope values. In addition, the comparative assessment of the LS and soil loss values calculated from each DEM with the two LS equations revealed a great divergence. It is noticeable that both LS and soil loss results presented higher values for slopes greater than 20°. It is concluded that the comparison of the LS values calculated with the two examined approaches and the use of different DEM with various resolutions and different sources does not change consistently with the increase of DEM grid size and accuracy. Thus, it is very significant in soil erosion modelling to use an LS equation that imports thresholds in its formula to avoid overestimation in soil loss calculations.

Soil losses related to land use and rainfall seasonality in a watershed in the Brazilian Cerrado

Water erosion is one of the main environmental issues nowadays, which results in the decline of soil quality, reducing the productive potential of crops and also causing water pollution, decreasing water availability for human supply. Thus, this study aimed to estimate soil losses related to the rainfall seasonality in the Verdinho River basin, located in the Brazilian Cerrado. Here, we gathered remote sensing products, cartographic and rainfall databases to provide the parameters of the Universal Soil Loss Equation (USLE) and to build watershed-scale estimations of the factors that contributing to erosion using the Geographic Information System (GIS) software. The greatest potential for erosion coincided with the rainy season (November–March). In terms of real erosion, the results ranged from 0 to 56,713.57 t ha−1 year−1, with the highest soil losses rates observed between the months of November and March. The land use and land cover categories with the highest soil losses are bare soil (48,369,623.73 t year−1), cultivated land (35,617,228.52 t year−1) and pasture (20,509,860.52 t year−1). It was also possible to observe critical points of higher occurrence of soil loss located mainly in the middle and lower part of the watershed. These high rates of soil losses are justified by the intensification of natural factors and the contribution of anthropic actions, which are evidenced mainly in the period of the rainy season. Thus, we emphasized the importance of planning the land use and management in the watershed, with the adoption of support practices in order to reduce the effects of the erosive process on the soil and especially on the watercourse.

THE USE OF REMOTE SENSING IN GHANA TO SUSTAINABLY MANAGE THE ENVIRONMENT

A prerequisite for achieving the objectives of sustainable development is knowledge of the nature, extent, geographical distribution, along with the potentials and limits of natural resources. The mapping, monitoring, measuring, and management of many elements of the built, natural, and biophysical environments are all made possible through satellite remote sensing. Remote sensing is a crucial tool for advancing solutions and offers useful insights into urgent environmental concerns. Thus, data collection for efficient resource management in Ghana has shown to be greatly aided by remote sensing, which may also be used for environmental monitoring and management. Because of this, it is crucial for remote sensing technology to progress in order to acquire data more effectively and efficiently, which helps with rapid change detection, sustainable environmental management, and sustainability. This review's goal was to provide a thorough analysis of the literature on Ghana's use of remote sensing for environmental management and sustainability. Wiley, Taylor & Francis, Science Direct (Elsevier), and Scopus (Elsevier) were a few of the databases used for the review. The findings indicate that there are numerous remote sensing applications for sustainable environmental management in Ghana, including environmental impact assessments of various projects, analyses of changes in land use and land cover, mapping of watersheds and hydrologic features, estimation of soil loss, management of water resources, management of forestry resources, and management of natural disasters. The outcomes also demonstrate that natural, biophysical, and constructed ecosystems might be appropriately monitored and sustainably managed for the benefit of both the present and future generations with the use of remote sensing technology. Governments, municipal managers, environmentalists, and planners may develop useful plans and strategies for sustainable development and effective environmental management with the aid of the information supplied by remote sensing. Keywords: Ghana, Sustainable Management, Environment, Remote Sensing.

Assessment of soil erosion risks in response to land-use and land-cover changes in Coka watershed, Southern Ethiopia

ABSTRACT Soil erosion is a serious problem arising from agricultural intensification and other anthropogenic activities which can cause deterioration of soil fertility and productivity. This study aims to estimate total amounts of soil loss using the RUSLE and NDVI models and identify major areas of concern for management interventions through site specific in the Coka watershed, Southern Ethiopia. The RUSLE model required the integration of thematic factors such as rainfall, length and steepness of the slope, land-use and land-cover, soil erodibility, and control practices. These factors were calculated using remote sensing data and GIS. The results indicated that total area coverage from study of watershed under the degree of severity of erosion and priority was <5(very low), 5 − 10 (low), 10 − 18 (moderate), 18 − 50 (high), 50 − 100 (very high) and >100 t ha–1yr–1 (severe). Soil loss rates ranged between 2.33 in bare land and 237.16 t ha–1yr–1 in forest. Based on the findings, erosion risk having estimated soil loss (≥ 18 t ha–1yr–1) which is above tolerable range for the country containing 73% (2723 ha) from the total area coverage of watershed. Thus, appropriate soil and water conservation practices should be adopted to restore degraded lands and environment by giving attention for erosion hotspot areas.

Vegetation Drastically Reduces Wind Erosion: An Implementation of the RWEQ in the Mongolian Gobi Steppe

Soil loss prevention is an important ecosystem service for protecting human and environmental health. Using spatiotemporal climate and environmental data of the Eastern Gobi Steppe, a region missing from previous studies of Mongolian wind-based soil erosion, we implemented the Revised Wind Erosion Equation (RWEQ) model to estimate soil loss. A replicable pipeline was developed to perform these computations, and made available openly. Soil loss was estimated on a monthly basis to analyze seasonal variations. The results show that the annual total soil loss was 61 × 1010 kg over an area of 69.3 × 103 km2, which is about 90 tonnes per hectare. Increasing fractional vegetation coverage to a uniform 50% coverage (doubling current vegetation coverage in every 1 km2) could reduce soil loss by 60%, highlighting the importance of protecting and increasing vegetation coverage in ecosystem service preservation.

Increasing the accuracy of monthly and annual estimates of soil loss in Iran by considering the effect of snow cover in reducing rainfall erosivity

Increasing the accuracy of monthly and annual estimates of soil loss in Iran by considering the effect of snow cover in reducing rainfall erosivity

Adapting the WEPP Hillslope Model and the TLS Technology to Predict Unpaved Road Soil Erosion.

Unpaved road erosion have been recognized as important sediment sources in a watershed. To evaluate where and when road erosion occurs, the soil loss along road segments should be precisely predicted with process-based erosion models. Methods: The hillslope version of the Water Erosion Prediction Project (WEPP) was used to estimate soil loss from 20 typical road segments in the red soil region of South China. Terrestrial laser scanning (TLS)-measured soil losses were used to validate the model simulations. The results showed that the WEPP model could reasonably predict the total soil loss in relatively short (less than 100 m) and gentle (slope gradient lower than 10%) road segments. In contrast, soil loss would be underestimated for long or steep road segments. Detailed outputs along roads revealed that most of the peak soil loss rates were underestimated. It might due to the linear critical shear stress theory in the WEPP model. Additionally, the lack of upstream flow was found to be connected to the relatively low model efficiency. Nevertheless, the WEPP simulation could accurately fit erosion trend and predict the peak soil loss positions along road segments. Conclusions: The WEPP model could be adopted to evaluate the erosion risk of unpaved roads in the red soil region of South China.

Gully erosion vulnerability modelling, estimation of soil loss and assessment of gully morphology: a study from cratonic part of eastern India.

A highly visible form of soil erosion is gully, a significant geomorphological feature, resulting from water erosion and causing land degradation and deterioration. In arid and semi-arid environment, gully erosion is conceived as an important source of sediment supply washing out the top fertile soil and exposing lower soil layers. The present study is conducted on the lateritic terrain of Rupai watershed of eastern plateau fringe of India, where water erosion is a serious concern. In order to prepare a gully erosion vulnerability mapping, the analytical hierarchy process (AHP) model coupled with geospatial technology is adopted taking into account thirteen bio-physical factors. It is revealed that around 49% area of the watershed belongs to high to very high gully erosion vulnerability zone (GEVZ) followed by moderate risk zone of 31.64%. This model is validated performing an accuracy assessment, which is calculated to be 90.91%, and the value of Kappa co-efficient is 0.86. It is imperative to estimate the average annual soil loss alongside of delineating GEVZ; thus, the revised universal soil loss equation (RUSLE) model is used with geospatial technology. It unveils that the average estimated soil loss of the watershed varies from < 15 to 431 t ha-1 y-1. Around 29% of the study area experiences high to very high (57 to > 147 t ha-1 y-1) soil erosion risk, where 68% area endures low level of soil erosion risk (< 15 t ha-1 y-1). The study of gully morphology depicts gully depth ranging from < 1 to 5m (small to medium gully) with V and U shapes. Results obtained from this study may help in planning and management of land use and soil erosion conservation.

Assessment of soil loss rate using GIS–RUSLE interface in Tashat Watershed, Northwestern Ethiopia

The erosion of soil is one of the most difficult and ongoing problems caused by deforestation, improper cultivation, uncontrolled grazing, and other anthropogenic activities. As a result, assessing the level and quantity of soil erosion is essential for agricultural productivity and natural resource management. Thus, the goal of this study was to quantify soil loss rates and identify hotspot locations in the Tashat watershed, Abay basin, Ethiopia. Thematic factor maps, comprising rainfall erosivity factor (R), soil erodibility factor (K), topography factor (LS), cover and management factor (C), and conservation practices factor (P), were integrated using remote sensing data and the GIS 10.3.1 environment to estimate soil loss using RUSLE. The findings indicated that the watershed annual soil loss varies from none in the lower part to 3970.6 t ha−1 year−1 in the middle, with a mean annual soil loss of 64.2 t ha−1 year−1. The total estimated annual soil loss was 61,885,742.9 tons from the total watershed area of 48,348.4 ha. The majority of these soil erosion-affected places are geographically located in the watershed middle steepest slope portion, where Cambic Arenosols with higher soil erodibility character than other soil types in the research area predominate. Thus, sustainable soil and water conservation techniques should be implemented in the steepest middle section of the study area by respecting and acknowledging watershed logic, people, and watershed potentials.

Millennial scale erosion and sedimentation investigation in karst watersheds using dating and palynology

The sedimentary sequence deposited in a depression provides good opportunity for karst watershed soil loss reconstruction. Extensive sediment dating and soil loss estimation in karst areas of Southwest China have been carried out in the past few decades. Unfortunately, most studies only revealed soil loss over the last 50–100 years by using 137Cs and/or 210Pb. This study attempts to reconstruct soil erosion in a watershed over the past millennium using sediment dating combined with palynological techniques. In this study, two karst watersheds with different degrees of rocky desertification were selected, and soil profile samples were collected from the depressions to determine pollen taxa, 137Cs and soil organic carbon, and then, the optically stimulated luminescence (OSL) and radiocarbon were used to date the sediments in the two profiles. The results showed that erosion rate characteristics in the Liaojiawodang (LJWD, severe rocky desertification) and Dajutang (DJT, mild rocky desertification) watersheds were markedly different over the last 1000 years. On average, the erosion rates of the LJWD and DJT watersheds were 0.13 Mg ha−1 yr−1 and 1.28 Mg ha−1 yr−1, respectively. Overall, the erosion rate in the areas with severe rocky desertification was obviously small in the past millennium, and there was no serious soil loss. This result indicated that rocky desertification developed at least 1000 years ago. Pollen analysis indicated that soil erosion changes in both watersheds over the past 1000 years were well correlated with the change in crop pollen indicating human farming activities. Based on changes in the content of different types of pollen in sediments, the change in soil erosion can be linked to the change in land use and vegetation landscape. Overall, this work improves our understanding of the relationship between soil erosion and agricultural activities and vegetation landscape change in karst watersheds.

Estimation of sediment production and soil loss in a water supply basin for the metropolitan region of São Paulo - Brazil

The Jaguarí river basin has outstanding importance in the national scenario for being located between the largest industrial and population centers in the country and for the process that involves the management of its water resources. The main purpose of the basin's reservoirs is to supply water to the population of the metropolitan region of São Paulo, and before that, there are pressures and conflicts between the different actors interested in water resources, as well as creating protection policies, establishing the need for sustainable use conservation units, support environmental protection policies, resulting in proposals for nature conservation measures and promotion of the population's quality of life. Hydrological models represent an alternative to verify the impacts resulting from anthropic actions in water availability and production of sediments in large hydrographic basins. The models can simulate/indicate how changes in the environment are reflected in the hydro sedimentological balance of a basin. This study aims to assess soil loss in the Jaguari River basin using the Soil and Water Assessment Tool (SWAT) to determine quantity and quality of the sediment production, the loss of soil, and resulting impacts to the Jaguarí River basin. Calibration and validation were performed to verify the suitability of the model and the spatialization of the factors that make up the Modified Universal Soil Loss Equation (MUSLE). The SWAT model proved to be suitable for the simulation of sediments; although the basin does not present a large area with potential for erosion risk, conservation measures can be taken to effectively control soil loss in susceptible areas. The average soil loss in the basin was 1.71 Mg ha−1 year−1 and the simulated and observed Sediment Delivery Rate (SDR) was 5.5% and 4.7%, respectively.