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1.
Weathering fluxes of arsenic from a small catchment in Slovak Republic   总被引：1，自引：1，他引：0  
Inputs of As to a small catchment due to chemical weathering of bedrock, mechanical weathering of bedrock, and atmospheric precipitation were 71.53, 23.98 and 0.02 g ha−1 year−1, respectively. The output fluxes of As due to mechanical erosion of soil, biological uptake, stream discharge, and groundwater flow were 6.32, 4.77, 0.37 and 0.02 g ha−1 year−1, respectively. The results indicate that arsenic accumulates in soil and regolith with a very high rate. This is attributed to the selective weathering and erosion with respect to arsenic and fixation of arsenic in the secondary solids produced by weathering. The output fluxes of As in stream and groundwater in Vydrica catchment in Slovak Republic (0.39 g ha−1 year−1) based on muscovite–biotite granites and granodiorites were much lower compared to catchments in a gold district in the Czech Republic. These results may be ascribed to the low levels of arsenic pollution measured in Vydrica catchment. The arsenic fluxes were estimated by calculation of mechanical and chemical weathering rates of the bedrocks in Vydrica catchment from mass balance data on sodium and silica. The justification of the steady state of Na and Si is that neither of the elements is appreciably accumulated in plants and in exchangeable pool of ions in soil.  相似文献   

2.
Gediz Basin is one of the regions where intense agricultural activities take place in Western Turkey. Erosion and soil degradation have long been causing serious problems to cultivated fields in the basin. This work describes the application of two different 137Cs models for estimating soil erosion rates in cultivated sites of the region. Soil samples were collected from five distinct cultivated regions subject to soil erosion. The variations of 137Cs concentrations with depth in soil profiles were investigated. Soil loss rates were calculated from 137Cs inventories of the samples using both proportional model (PM) and simplified mass balance model (SMBM). When PM was used, erosion and deposition rates varied from −15 to −28 t ha−1 year−1 and from +5 to +41 t ha−1 year−1, respectively; they varied from −16 to −33 t ha−1 year−1 and from +5 to +55 t ha−1 year−1 with SMBM. A good agreement was observed between the results of two models up to 30 t ha−1 year−1 soil loss and gain in the study area. Ulukent, a small representative agricultural field, was selected to compare the present data of 137Cs techniques with the results obtained by universal soil loss equation (USLE) applied in the area before.  相似文献   

3.
Soil erosion modeling of a Himalayan watershed using RS and GIS   总被引：5，自引：1，他引：4  
Employing the remote sensing (RS) and geographical information system (GIS), an assessment of sediment yield from Dikrong river basin of Arunachal Pradesh (India) has been presented in this paper. For prediction of soil erosion, the Morgan-Morgan and Finney (MMF) model and the universal soil loss equation (USLE) have been utilized at a spatial grid scale of 100 m × 100 m, an operational unit. The average annual soil loss from the Dikrong river basin is estimated as 75.66 and 57.06 t ha−1 year−1 using MMF and USLE models, respectively. The watershed area falling under the identified very high, severe, and very severe zones of soil erosion need immediate attention for soil conservation.  相似文献   

4.
Studying spatial and temporal variation of soil loss is of great importance because of global environmental concerns. Understanding the spatial distribution of soil erosion and deposition in the high-cold steppe is important for designing soil and water conservation measures. Measured 137Cs losses (Bq m−2) from long-term high altitude (4,000 m above sea level) watershed plots on the Qinghai–Tibet plateau and derived soil erosion estimates (Mg ha−1 year−1) were significantly correlated to directly measured soil losses from the same plots, over the same period (1963–2005). The local reference inventory was estimated to be 2,468 Bq m−2. The result of analyzing 137Cs distribution and its intensity in the soil profiles in this area shows similarities to 137Cs distribution in other areas. 137Cs is basically distributed in the topsoil layer of 0–0.3 m. Soil erosions vary greatly in the entire sampled area, ranging from 5.5 to 23 Mg ha−1 year−1, with an average of 16.5 Mg ha−1 year−1 which is a moderate rate of erosion.  相似文献   

5.
Karst depressions comprise geomorphologically important sources and sinks for sediments and associated pollutants; yet the sedimentology of many depressions is not well understood in the world. In this paper, the 137Cs technique was employed to estimate recent sedimentation rates in a Chinese polygonal karst depression. The results indicate that the sediment deposition rates ranged from 0.91 to 1.97 mm year−1 from 1963 to 2007, and the average sediment deposition rate and specific deposit yield were estimated to be 1.47 mm year−1 and 20 t km−2 year−1, respectively. These results are consistent with the local monitoring data of runoff fields, which confirms the validity of the overall approach. This shows that the soil loss rate is very low in some karst areas of Southwest China. Above all, the approach appears to offer valuable potential to study surface erosion by estimating sediment deposition rates of karst depressions, rather than the assessment of complicated soil erosion in stony soils of carbonate rock slopes. In addition, the space distribution of surface soil and 137Cs inventories are affected remarkably by the inhomogeneous dissolution of limestone under the soil. It may be an important phenomenon, which exists widely in karst areas, and it is significantly different from other places.  相似文献   

6.
The universal soil loss equation (USLE) is an erosion model to estimate average soil loss that would generally result from splash, sheet, and rill erosion from agricultural plots. Recently, use of USLE has been extended as a useful tool predicting soil losses and planning control practices by the effective integration of the GIS-based procedures to estimate the factor values on a grid cell basis. This study was performed for five different lands uses of Indağı Mountain Pass, Cankırı to predict the soil erosion risk by the USLE/GIS methodology for planning conservation measures in the site. Of the USLE factors, rainfall-runoff erosivity factor (USLE-R) and topographic factor (USLE-LS) were greatly involved in GIS. These were surfaced by correcting USLE-R site-specifically using DEM and climatic data and by evaluating USLE-LS by the flow accumulation tool using DEM and watershed delineation tool to consider the topographical and hydrological effects on the soil loss. The study assessed the soil erodibility factor (USLE-K) by randomly sampled field properties by geostatistical analysis. Crop management factor for different land-use/land cover type and land use (USLE-C) was assigned to the numerical values from crop and flora type, canopy and density of five different land uses, which are plantation, recreational land, cropland, forest and grassland, by means of reclassifying digital land use map available for the site. Support practice factor (USLE-P) was taken as a unit assuming no erosion control practices. USLE/GIS technology together with the geostatistics combined these major erosion factors to predict average soil loss per unit area per unit time. Resulting soil loss map revealed that spatial average soil loss in terms of the land uses were 1.99, 1.29, 1.21, 1.20, 0.89 t ha−1 year−1 for the cropland, grassland, recreation, plantation and forest, respectively. Since the rate of soil formation was expected to be so slow in Central Anatolia of Turkey and any soil loss of more than 1 ton ha−1 year−1 over 50–100 years was considered as irreversible for this region, soil erosion in the Indağı Mountain Pass, to the great extent, attained the irreversible state, and these findings should be very useful to take mitigation measures in the site.  相似文献   

7.
Assessment of soil erosion risk using SWAT model   总被引：3，自引：2，他引：1  
Soil erosion is one of the most serious land degradation problems and the primary environmental issue in Mediterranean regions. Estimation of soil erosion loss in these regions is often difficult due to the complex interplay of many factors such as climate, land uses, topography, and human activities. The purpose of this study is to apply the Soil and Water Assessment Tool (SWAT) model to predict surface runoff generation patterns and soil erosion hazard and to prioritize most degraded sub-catchment in order to adopt the appropriate management intervention. The study area is the Sarrath river catchment (1,491 km2), north of Tunisia. Based on the estimated soil loss rates, the catchment was divided into four priority categories for conservation intervention. Results showed that a larger part of the watershed (90 %) fell under low and moderate soil erosion risk and only 10 % of the watershed was vulnerable to soil erosion with an estimated sediment loss exceeding 10 t?ha?1?year?1. Results indicated that spatial differences in erosion rates within the Sarrath catchment are mainly caused by differences in land cover type and gradient slope. Application of the SWAT model demonstrated that the model provides a useful tool to predict surface runoff and soil erosion hazard and can successfully be used for prioritization of vulnerable areas over semi-arid catchments.  相似文献   

8.
Siruvani watershed with a surface area of 205.54 km2 (20,554 hectare), forming a part of the Western Ghats in Attapady valley, Kerala, was chosen for testing RUSLE methodology in conjunction with remote sensing and GIS for soil loss prediction and identifying areas with high erosion potential. The RUSLE factors (R, K, LS, C and P) were computed from local rainfall, topographic, soil classification and remote sensing data. This study proved that the integration of soil erosion models with GIS and remote sensing is a simple and effective tool for mapping and quantifying areas and rates of soil erosion for the development of better soil conservation plans. The resultant map of annual soil erosion shows a maximum soil loss of 14.917 t h−1 year−1 and the computations suggest that about only 5.76% (1,184 hectares) of the area comes under the severe soil erosion zone followed by the high-erosion zone (11.50% of the total area). The dominant high soil erosion areas are located in the central and southern portion of the watershed and it is attributed to the shifting cultivation, and forest degradation along with the combined effect of K, LS and C factor. The RUSLE model in combination with GIS and remote sensing techniques also enables the assessment of pixel based soil erosion rate.  相似文献   

9.
A simplified regression model is here calibrated on the basis of rainfall data records of Sicily (southern Italy), in order to show the model reliability in assessing the R-factor of the Universal Soil Loss Equation and its revised version (RUSLE) and to provide an estimate of long-term rainfall erosivity at medium-regional scale. The proposed model is a rearrangement of a former simplified model, formulated for the Italian environment, grouping three easily available rainfall variables on various time scales, which has been shown to be more successful than others in reproducing the rainfall erosive power over different locations of Italy. A geostatistical interpolation procedure is then applied for generating the regional long-term erosivity map with associated standard error. Areas with severe erosive rainfalls (from 2,000 up to more than 6,000 MJ mm ha−1 h−1) are pointed out which will correspond to areas suffering from severe soil erosion. Solving the problem of calculating the R-factor value in the RUSLE equation by means of such a simplified model here formulated will allow to predict the related soil loss. Moreover, given the availability of long time-series of concerned rainfall data, it will be possible to analyse the variability of rainfall erosivity within the last 50 years, and to investigate the application of RUSLE or similar soil erosion models with forecasting purposes of soil erosion risk.  相似文献   

10.
A field study was conducted to determine the effect of landscape spatial pattern and micro-topography on nutrient transfer via runoff from two catchments into Yuqiao Reservoir in north China. The surface runoff discharge was measured during rainfall events and water samples were analyzed in 2004 and 2005. The mean annual total nitrogen (TN) and total phosphorus (TP) exports per unit area from Caogezhuang catchment (C catchment) were 1.048 and 0.561 kg ha−1 year−1, respectively, while the TN and TP exports from Taohuasi catchment (T catchment) were 0.158 and 0.027 kg ha−1 year−1. In both catchments, village and vineyard shared the highest nutrient export ability due to the accumulated animal waste and heavy application of fertilizer and manure. In T catchment, the distance of village and vineyard was about 1,500 m away from the receiving water and in between were woodland and cropland. In the hydrological pathway, there were sink landscape structures of small stone dams, roadside swale, vegetated filter strip and dry ponds, which could detain water and nutrients. In C catchment, the distance between the village and the receiving water was about 200 m, and the hydrological pathway was compacted roads and ditches with no sink structures. It is suggested that the distance between the pollution source area and the receiving water and the micro-topographical features were the main factors to control the great difference in nutrient export rates.  相似文献   

11.
The Narmada River flows through the Deccan volcanics and transports water and sediments to the adjacent Arabian Sea. In a first-ever attempt, spatial and temporal (annual, seasonal, monthly and daily) variations in water discharge and sediment loads of Narmada River and its tributaries and the probable causes for these variations are discussed. The study has been carried out with data from twenty-two years of daily water discharge at nineteen locations and sediment concentrations data at fourteen locations in the entire Narmada River Basin. Water flow in the river is a major factor influencing sediment loads in the river. The monsoon season, which accounts for 85 to 95% of total annual rainfall in the basin, is the main source of water flow in the river. Almost 85 to 98% of annual sediment loads in the river are transported during the monsoon season (June to November). The average annual sediment flux to the Arabian Sea at Garudeshwar (farthest downstream location) is 34.29×106 t year−1 with a water discharge of 23.57 km3 year−1. These numbers are the latest and revised estimates for Narmada River. Water flow in the river is influenced by rainfall, catchment area and groundwater inputs, whereas rainfall intensity, geology/soil characteristics of the catchment area and presence of reservoirs/dams play a major role in sediment discharge. The largest dam in the basin, namely Sardar Sarovar Dam, traps almost 60–80% of sediments carried by the river before it reaches the Arabian Sea.  相似文献   

12.
Nitrogen addition to soil can play a vital role in influencing the losses of soil carbon by respiration in N-deficient terrestrial ecosystems. The aim of this study was to clarify the effects of different levels of nitrogen fertilization (HN, 200 kg N ha−1 year−1; MN, 100 kg N ha−1 year−1; LN, 50 kg N ha−1 year−1) on soil respiration compared with non-fertilization (CK, 0 kg N ha−1 year−1), from July 2007 to September 2008, in temperate grassland in Inner Mongolia, China. Results showed that N fertilization did not change the seasonal patterns of soil respiration, which were mainly controlled by soil heat-water conditions. However, N fertilization could change the relationships between soil respiration and soil temperature, and water regimes. Soil respiration dependence on soil moisture was increased by N fertilization, and the soil temperature sensitivity was similar in the treatments of HN, LN, and CK treatments (Q 10 varied within 1.70–1.74) but was slightly reduced in MN treatment (Q 10 = 1.63). N fertilization increased soil CO2 emission in the order MN > HN > LN compared with the CK treatment. The positive effects reached a significant level for HN and MN (P < 0.05) and reached a marginally significant level for LN (P = 0.059 < 0.1) based on the cumulative soil respiration during the 2007 growing season after fertilization (July–September 2007). Furthermore, the differences between the three fertilization treatments and CK reached the very significant level of 0.01 on the basis of the data during the first entire year after fertilization (July 2007–June 2008). The annual total soil respiration was 53, 57, and 24% higher than in the CK plots (465 g m−2 year−1). However, the positive effects did not reach the significant level for any treatment in the 2008 growing season after the second year fertilization (July–September 2008, P > 0.05). The pairwise differences between the three N-level treatments were not significant in either year (P > 0.05).  相似文献   

13.
Remote sensing data and GIS techniques have been used to compute runoff and soil erosion in the catchment area along the NH-1A between Udhampur and Kud covering an area of approximately 181 km2. Different thematic layers, for example lithology, a landuse and landcover map, geomorphology, a slope map, and a soil-texture map, were generated from these input data. By use of the US Soil Conservation Service curve number method, estimated runoff potential was classified into five levels—very low, low, moderate, high, and very high. Data integration was performed by use of the weighting rating technique, a conventional qualitative method, to give a runoff potential index value. The runoff potential index values were used to delineate the runoff potential zones, namely low, moderate, high, and very high. Annual spatial soil loss estimation was computed using the Morgan–Morgan–Finney mathematical model in conjunction with remote sensing data and GIS techniques. Greater soil erosion was found to occur in the northwestern part of the catchment area. When average soil loss from the catchment area was calculated it was found that a maximum average soil loss of more than 20 t ha−1 occurred in 31 km2 of the catchment area.  相似文献   

14.
Erosion and sediment redistribution are important processes in landscape changes in the short and long term. In this study, the RMMF model of soil erosion and the SEDD model of sediment delivery were used to estimate annual soil loss and sediment yield in an ungauged catchment of the Spanish Pre-Pyrenees and results were interpreted in the context of the geomorphic features. The Estaña Catchment is divided into 15 endorheic sub-catchments and there are 17 dolines. Gullies and slopes were the main erosive geomorphic elements, whereas the colluvial, alluvial, valley floor, and doline deposits were depositional elements. Spatially distributed maps of gross soil erosion, sediment delivery ratio (SDR), and sediment yield (SY) were generated in a GIS. Severe erosion rates (>100 Mg ha?1 year?1) were found in gullies, whereas mean and maximum erosion rates were very high on slopes developed on Keüper Facies and high in soils on Muschelkalk Facies. Where crops are grown, the depositional-type geoforms were predicted by the models to have an erosive dynamic. Those results were consistent with the rates of erosion quantified by 137Cs which reflects the significant role of human activities in triggering soil erosion. Catchment area was positively correlated with erosion rate, but negatively correlated with SDR and SY. The latter were negatively correlated with the proportion of the surface catchment covered with forests and scrublands. The topography of the area influenced the high SDR and SY in the dolines and valley floors near the sinks. Intra-basin stored sediment was 59.2% of the total annual eroded soil in the catchment. The combination of the RMMF and SEDD models was an appropriate means of assessing the effects of land uses on soil erosion and obtaining a better understanding of the processes that underlie the geomorphic changes occurring in mountainous environments of the Mediterranean region.  相似文献   

15.
Mapping of erosion risk areas is an important tool for the planning of natural resources management, allowing researchers to propose the modification of land use properly and implement more sustainable long-term management strategies. The objective of this study was to assess and identify critical sub-catchments for soil conservation management using the USLE, GIS, and remote sensing techniques. The Tapacurá catchment is one of the planning units for water resource management of the Recife Metropolitan Region. Maps of the erosivity (R), erodibility (K), slope (LS), cover-management (C), and support practice (P) factors were derived from the climate database, digital elevation model, and soil and land-use maps. In order to validate the simulation process, total sediment delivery ratio was estimated. The results showed a mean sediment delivery ratio (SDR) of around 11.5?% and a calculated mean sediment yield of 0.108?t?ha?1?year?1, which is close to the observed one, 0.169?t?ha?1?year?1. The obtained soil loss map could be considered as a useful tool for environmental monitoring and water resources management. The methodology applied showed acceptable precision and allowed the identification of the most susceptible areas to soil erosion by water, constituting an important predictive tool for soil and environmental management in this region, which is highly relevant for the prediction of varying development scenarios for Tapacurá catchment. This approach can be applied to other areas for simple and reliable identification of critical areas of soil erosion in catchments.  相似文献   

16.
Environmental geochemistry plays an important role in understanding the distribution of major cations (Ca2+, Mg2+, Na+, K+) in Helwan catchment, south Cairo, Egypt. Evaluation of soil mechanical erosion rate, depletion rate, exchangeable rates of base cations and sodium adsorption ratios are essential for understanding soil degradation problems in the representative Helwan catchment. Soil erosion is a natural process. It often becomes a problem when human activity causes it to occur much faster than under natural conditions. The results of the mechanical erosion rate of soil and the exchangeable rates of base cations are 1845 and 80.3 kg ha−1 yr−1, respectively. The high intensity of the mechanical erosion rate is probably attributed to the high specific surface area of the studied type of Vertisol, intensive application of fertilizer and industrial activities. Mechanical erosion of soil, exchangeable rate of base cations and the depletion rate of base cations are almost inexhaustible sources of sodium, and all these increase the problem of sodic soils and may affect plant productivity in Helwan catchment.  相似文献   

17.
In recent times, soil erosion interlocked with land use and land cover (LULC) changes has become one of the most important environmental issues in developing countries. Evaluation of this complex interaction between LULC change and soil erosion is indispensable in land use planning and conservation works. This paper analysed the impact of LULC change on soil erosion in the north-western highland Ethiopia over the period 1986–2016. Rib watershed, the area with dynamic LULC change and severe soil erosion problem, was selected as a case study site. Integrated approach that combined geospatial technologies with revised universal soil loss equation model was utilized to evaluate the spatio-temporal dynamics of soil loss over the study period. Pixel-based overlay of soil erosion intensity maps with LULC maps was carried out to understand the change in soil loss due to LULC change. Results showed that the annual soil loss in the study area varied from 0 to 236.5 t ha?1 year?1 (tons per hectare per year) in 1986 and 0–807 t ha?1 year?1 in 2016. The average annual soil loss for the entire watershed was estimated about 40 t ha?1 year?1 in 1986 comparing with 68 t ha?1 year?1 in 2016, a formidable increase. Soil erosion potential that was estimated to exceed the average soil loss tolerance level increased from 34.5% in 1986 to 66.8% in 2016. Expansion of agricultural land at the expense of grassland and shrubland was the most detrimental factor for severe soil erosion in the watershed. The most noticeable change in soil erosion intensity was observed from cropland with mean annual soil loss amount increased to 41.38 t ha?1 year?1 in 2016 from 26.60 in 1986. Moreover, the most successive erosion problems were detected in eastern, south-eastern and northern parts of the watershed. Therefore, the results of this study can help identify the soil erosion hot spots and conservation priority areas at local and regional levels.  相似文献   

18.
Expansion of agricultural at the cost of forested land is a common cause of watershed degradation in the mountain zones of developing countries. Many studies have been conducted to demonstrate land use changes in such regions. However, current knowledge regarding the changes, driving forces and implications of such change within the context of watershed development is limited. This study analyses changes in spatial patterns of agricultural land use and their consequences for watershed degradation during the 1976–2000 period along an altitude gradient in a watershed in Nepal, by means of remote sensing, GIS and the universal soil loss equation. Estimated soil loss ranged from 589 to 620 t ha−1 y−1, while areas of extreme hazard severity (>100 t ha−1) increased from 9 to 14.5% from 1990 to 2000. Spatial distribution of soil loss in 2000 was characterized by 88% of total soil losses being from upland agricultural areas. The study determined that without considering other forms of land degradation, only water erosion was responsible for erosion of a substantial area in a short timeframe. Areas under upland cultivation are in an extremely vulnerable state, with these areas potentially no longer cultivable within a period of 6 years. As sustainability of the watershed is dependent on forests, continued depletion of forest resources will result in poor economic returns from agriculture for local people, together with loss of ecosystem services. Thus, in order to achieve the goal of watershed development, remaining forest lands must be kept under strict protection.  相似文献   

19.
Estimation of spatial extent of soil erosion, one of the most serious forms of land degradation, is critical because soil erosion has serious implications on soil fertility, water ecosystem, crop productivity and landscape beauty. The primary objective of the current study was to assess and map the soil erosion intensity and sedimentation yield of Potohar region of Pakistan. Potohar is the rainfed region with truncated and complex topography lying at the top of the Indus Basin, the world’s largest irrigation networks of canals and barrages. Spatially explicit Revised Universal Soil Loss Equation (RUSLE) Model integrated with Remote Sensing-GIS techniques was used for detecting/mapping of erosion prone areas and quantification of soil losses. The results show that the Potohar region is highly susceptible to soil erosion with an average annual soil loss of 19 tons ha?1 year?1 of which the maximum erosion (70–208 tons ha?1 year?1) was near the river channels and hilly areas. The sediment yield due to the erosion is as high as 148 tons ha?1 year?1 with an average of 4.3 tons ha?1 year?1. It was found that 2.06% of the total area falls under severe soil erosion, 13.34% under high erosion, 15.35% under moderate soil erosion while 69.25% of the area lies in the low (tolerable) soil erosion. Chakwal and Jhelum districts of the region are seriously affected by erosion owing to their topography and soil properties. The information generated in this study is a step forward towards proper planning and implementation of strategies to control the erosion and for protection of natural resources. It is, hence, necessary that suitable water harvesting structures be made to control water to prevent soil erosion and provision of water in the lean season in this region. Tree plantation and other erosion control practices such as strip cropping can also minimize soil erosion in this region.  相似文献   

20.
The existing traditional methods of assessing the rates of soil loss have many limitations and are difficult to apply in the karst areas of Southwest China. Karst depressions comprise geomorphologically important sources and sinks for sediments and associated pollutants, yet the sedimentology of many depressions is not well understood. In this paper, the 137Cs technique was employed to investigate recent sedimentation rates in a Chinese polygonal karst depression. The results indicated that the sediment deposition rates ranged from 0.91 to 1.97 mm?a?1 in the period from 1963 to 2007, and the average sediment deposition rate and specific deposit yield of the catchment were estimated to be 1.47 mm?a?1 and 20 t?km?2?a?1, respectively. The results obtained were consistent with the local monitoring data of runoff plots, confirming the validity of the overall approach. It was shown that soil loss rates were very low in some karst areas of Southwest China. Above all, the approach appears to offer valuable potential to study surface erosion by estimating sediment deposition rates of karst depressions, rather than the assessment of complicated soil erosion in stony soils of carbonate rock slopes. In addition, the spacial distribution of surface soil and 137Cs inventories was affected remarkably by the inhomogeneous dissolution of limestone under the soil. It may be an important phenomenon which exists widely in the karst areas and is significantly different from other places.  相似文献   

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