Total Erosion Research Articles

‘The people want …: ’ the populist specter in the Tunisian President’s inaugural speech

ABSTRACT This paper combines insights from Deictic Space Theory and Conceptual Metaphor Theory to analyze the Tunisian President’s inaugural speech following his victory in the October 2019 elections. Detailed critical discourse analysis of the deictic exponents and the metaphorical image schemas employed in the text showed a Manichean opposition between the pure/good people (Us) versus the corrupt/evil ‘elites’ (Them), nostalgia to a pristine revolutionary moment, a pan-Arab discourse which anchors the Israeli-Palestinian conflict close to the local geography and a radical form of populism, which grounds sovereignty within a transcendent theocratic cosmology. It is suggested that the upsurge of populism in Tunisian politics could be explained by the disenchantment with the deficient and rather ‘fake’ Islamo-nationalist consensus politics, the inappropriate neoliberal policies imposed by fund-raising bodies like the International Monetary Fund (IMF) and the World Bank (WB) as well as the fragmentation, if not total erosion, of viable public spaces for rational deliberation and decision-making processes as a result of the ‘digital era.’

Effect of denosumab switched from bisphosphonates in preventing joint destruction in postmenopausal rheumatoid arthritis patients with anti-cyclic citrullinated peptide antibodies

IntroductionThis study aimed to determine the effects of denosumab treatment on the joint destruction of Japanese females with rheumatoid arthritis (RA) and anti-cyclic citrullinated peptide (CCP) antibodies.Materials and methodsThis retrospective longitudinal study included 56 patients treated with denosumab and 50 patients treated with bisphosphonate. All participants were positive for anti-CCP antibodies. All patients also had a history of osteoporosis treatment with bisphosphonate, which was either continued or switched to 60 mg of subcutaneous denosumab injection every 6 months. To assess the progression of joint destruction, hand and foot radiographs were taken, and changes in modified total Sharp score (mTSS), erosion score (ERO), and joint space narrowing score (JSN) were evaluated at 12 months and 24 months. The changes in BMD of the lumbar spine and hip were also assessed at 12 months.ResultsAt 12 months, there were significant differences in the change of ERO (p = 0.015) and mTSS (p = 0.01). Similarly, there were significant differences in the change of ERO (p = 0.013) and mTSS (p = 0.003) at 24 months. In contrast, no significant difference was observed in the changes of JSN and clinical parameters. There were significant differences in the changes in BMD in the femoral neck (p = 0.011) and total hip (p = 0.012).ConclusionDenosumab treatment might be effective for the inhibition of bone erosion progression in the patients with RA, and it potentially contributes to the treatment of osteoporosis and prevention of destructive arthritis in patients with switching treatment from bisphosphonate.

Ridge‐furrow rainfall harvesting planting and its effect on soil erosion and soil quality in sloping farmland

AbstractRidge‐furrow rainfall harvesting (RFRH) planting can improve crop productivity through enhancing water use efficiency. However, effects of long‐term use of RFRH on soil erosion and soil quality in sloping farmland are not well understood. This experiment was conducted with a two‐factor split plot design, with the main plot having a slope of 5° and 10°. The sub‐plots followed three planting patterns: contour ridge‐furrow planting without mulching (CK), contour ridge film mulching and furrow straw mulching (T1), and contour ridge film mulching and furrow no mulching (T2). The results showed that no significant effect on soil erosion was found under T1 and T2 on 5° slope. The total runoff and total erosion of T1 on 10° slope decreased by 82.8 and 92.0%, and that of T2 on 10° slope decreased by 34.5 and 83.1%, respectively, compared with CK. Soil water content in T1 and T2 significantly increased by 11.0 and 10.6%, respectively, compared with CK (p < .05). Soil quality index in T1 was the highest, followed by T2 under the same slope. Yield was increased in T1 and T2 significantly by 30.7 and 20.2%, respectively, compared with CK (p < .05). Our results show that contour ridge film mulching and furrow straw mulching can alleviate drought, water shortages, and soil erosion.

Effect of surface rills on soil redistribution by tillage erosion on a steep hillslope

Water and tillage erosion processes are important contributors to the total soil erosion in steeply sloping farmland. Although these erosion processes and mechanisms are well understood separately, little is known about the impact of water erosion on the soil redistributed by tillage erosion on sloping fields. In this study, the magnetic tracing (MT) and terrestrial laser scanning (TLS) techniques were applied to perform tillage simulation experiments to ascertain the effect of surface rills on tillage erosion in the dry-hot valley region of southwestern China. The results of simulation experiments indicate that the mean soil flux (Qs) due to tillage on the single-rilled (double-rilled) hillslopes was 85.6 (109.9) kg/m for the mean soil loss rates (Rs) of 21.0 (53.7) Mg/ha in simulated-rill areas, and that tillage erosion rates (Rt) tended to increase with increasing Rs. Rt of the single-rilled (double-rilled) hillslopes increased by 1.7 (2.2) times averagely, compared with those of the non-rilled hillslopes. The greater the number and volume of rills, the more easily soil translocation occurred on steep slopes. Rt were highly significantly and positively correlated with Rs on the rilled hillslopes (P < 0.01). As slope gradient increased, the tillage displacement and Qs appeared to increase on the single-rilled hillslopes. A comparison of measurement results showed that the TLS technique was not only able to measure tillage-induced soil translocation with an accuracy similar to that of the MT technique, but also captured the change in the slope microtopography due to tillage operation. Our results indicated that surface rills remarkably influence tillage erosion and that Qs and Rt enhance with increasing Rs on the slopes.

Spatial-temporal variations of soil erosion in Southern Yunnan Mountainous Area using GIS and RUSLE: A case study in Yuanyang County, Yunnan Province, China.

It is of great significance to understand the spatial-temporal change of soil erosion in the Southern Yunnan Mountainous Area, especially for soil and water conservation planning and ecolo-gical protection in the world cultural heritage area. Based on the RUSLE model and GIS/RS space information technology, we examined the spatial-temporal variation of soil erosion and its relationship with environmental factors in Yuanyang County from 2005 to 2015. The results showed that, during the study period, the spatial differentiation of soil erosion in Yuanyang County was substantial. The soil erosion area was concentrated on the southeast and southwest region. Erosion widely distributed among both sides of Tengtiao River. Extreme and severe erosion presented a point distribution pattern. The average soil erosion modulus was 11.06 t·hm-2·a-1 from 2005 to 2015. The erosion level was basically slight and mild, accounting 80% of the total. Mild and moderate erosion contributed nearly 50% of total annual soil erosion, which was the key level of soil erosion control. During the study period, soil erosion had been slowed down with the improvement of forest cover. The terrain was complicated and changeable in Yuanyang County, and soil erosion distribution had a prominent correlation with altitude and slope. The formation of this distribution pattern was driven by numerous natural and human factors. The key area of soil and water protective governance were below 500 m, above 1500 m and slope located at 25°-45°.

Soil erosion estimation using Geographic Information System (GIS) and Revised Universal Soil Loss Equation (RUSLE) in the Siwalik Hills of Nawalparasi, Nepal

AbstractSoil erosion is one of the gravest environmental threats to the mountainous ecosystems of Nepal. Here, we combined a Geographic Information System (GIS) with the Revised Universal Soil Loss Equation (RUSLE) to estimate average annual soil loss, map erosion factors, compare soil erosion risks among different land use types, and identify erosion hotspots and recommend land use management in the Girwari river watershed of the Siwalik Hills. The annual soil loss was estimated using RUSLE factors: rainfall erosivity (R), soil erodibility (K), slope length and steepness (LS), cover crops (C), and conservation practices (P), and erosion factors maps were generated using GIS. Results indicate highest total erosion occurring in hill forests (13,374.3 t yr–1) and lowest total erosion occurring in grasslands (2.9 t yr–1). Hill forests showed high to very severe erosion due to steepness of hills, open forest types, and minimal use of conservation practices. Also, erosion hotspots (&amp;gt;15 t ha–1 yr–1) occurred in only 4.2% of the watershed, primarily in steep slopes. Overall, these results provide important guidelines to formulate management plans and informed decisions on soil conservation at local to regional levels. While the study is the first effort to assess soil erosion dynamics in the Girwari river watershed, potential for application in other basins largely exists.

Experimental and Numerical Evaluation of the Effect of Particle Size on Slurry Erosion Prediction

AbstractDuring petroleum production, sand particles can be entrained with the transported carrier fluid despite of any sand exclusion process and erode the inner walls of the pipelines. This erosion process may even cause pipe leakage and oil spill. Therefore, investigating the regularities of erosion damage changing with particle size and predicting erosion behavior for different particle sizes are important to pipeline safety. In this study, slurry erosion experiments are conducted using quartz particles with similar shapes and different sizes ranging from 25 μm to 600 μm to investigate the effect of particle size on erosion profiles and provide the database for evaluating available erosion models. Computational fluid dynamics (CFD) is used to simulate the fluid flow and track particles to obtain impact information. Erosion equations then connect the particles’ impact information with erosion rate. Finally, the available mechanistic and empirical equations erosion models are evaluated by comparing predicted erosion profile with experimental data. It was found that the local maximum erosion damage increases with particle size, although the total erosion ratio is not changing significantly. These changes of erosion profiles can be predicted with acceptable accuracy by available empirical erosion models when particle sizes are no less than 75 μm.

GIS and remote sensing-based assessment of soil erosion risk using RUSLE model in South-Kivu province, eastern, Democratic Republic of Congo

Soil erosion risk assessment in South-Kivu longs for the colonial epoch, while the province faces the problem of extreme degradation of land in the form of soil erosion. Thus, the study attempts to assess the soil erosion at the province level using the Revised Universal Soil Loss Equation (RUSLE) in conjunction with the Geographical Information System (GIS), and remote sensing data. The estimated total soil erosion was 2.084 million tons; with an annual average of 138.2 t ha−1 yr−1. Moreover, the soil loss greater than 100 t ha−1 yr−1 accounts for 45.2% of the total erosive land. The soil erosion worsening nearly the entire territories range between 87 t ha−1 yr−1 in Shabunda to 248 t ha−1 yr−1 in Uvira. Under high aggressiveness of rainfall with mean of 1857.19 mm/y, the highest rate found in Perennial crop, Trees, and Cropland in contrast to Shrub and closed Forest was mainly due to the mean slope of 22% found in the former Land cover categories compared to 17% of Shrubland and closed forest. The adoption of terracing could reduce by 76% the current rate of cropland i.e., from (162.12 t ha−1 yr−1 to 38 t ha−1 yr−1). Therefore it is strongly recommended.

ОЦЕНКА БАЛАНСА НАНОСОВ РЕК ОБЬ И ЕНИСЕЙ

This paper presents results of comparative analysis of the sediment budgets of the Ob’ and the Yenisei, base on universal erosion equations, RUSLE using 250 m resolution DEM GMTED 2010. Cumulative volumes of sediments accumulated in the stream catchments were estimated calculating the difference between erosion and sediments runoff of the studied basins. Thus, the difference between total erosion (watershed erosion + bank erosion) is (1250 MT/year + 35 MT/year) for the Ob and (315 MT/year + 21.9 MT/year) for the Yenisei. Sediment runoff in the mouths of both rivers estimated based on MSU data is 63.5 MT/year for the Ob and 32.5 MT/year for the Yenisei; Sediment runoff in the mouths estimated based on Roshydromet data is 16 MT/year for the Ob and 2.4 MT/year for the Yenisei. Sediment runoff was used to calculate the total deposition of matter in the catchment area during the transport of sediments from sources to sinks, for the Ob total deposition is 1270 MT/year, for the Yenisei is 335 MT/year. For the unregulated part of the Ob’ catchment, the accumulation was 56.5 MT/year, and for the unregulated part of the Yenisei catchment was 43 MT/year. The coefficient of reduction of sediment runoff (1/SDR) downstream, based on new samplings of sediment runoff in 2018–2019 in the mouths of both, Ob and Yenisei, was 2.3, and for the entire catchment area 20 and 30 respectively. Volume of sediments moved by denudation processes in the basin ends up being redeposited within the same fluvial systems. Thus, under the current hydro-meteorological regime, the large drainage basins in Russia and elsewhere are major depositional systems.

Establishment and application of soil hydraulic erosion model based on GIS and USLE model

Soil erosion is the most common form of soil degradation, which is the main problem of soil environmental destruction worldwide. Based on the USLE and GIS remote sensing inversion and superposition analysis technology, this study simulated and calculated soil hydraulic erosion in Fangshan World Geological Park, China in 2011, 2012 and 2013, analyzed its spatial-temporal dynamic changes, and explored the key points of soil erosion control in the study area. The results show that (1) The main erosion occurred at 25°-35° steep slope and 400-800m height, which accounted for more than 30% of the total soil erosion in all the three years. (2) The average erosion modulus and erosion amount in 2012 were significant higher than that in 2011 and 2013 at each slope grade, shown that the soil erosion of 2012 is influenced by natural disaster.With the increase of slope grade, the average modulus also increased.

Modeling linkages between erosion and connectivity in an urbanizing landscape

Erosion and connectivity are spatially varied processes key to determining sediment transport and delivery to downstream waterbodies. However, we find few studies that explicitly model the linkages of where erosion and connectivity coincide and where they contradict, particularly in urbanizing settings. In this study, we couple in-stream aquatic sensing, the Revised Universal Soil Loss Equation (RUSLE), the Index of Connectivity (IC), and the Sediment Delivery Ratio (SDR), together with Monte Carlo uncertainty analysis, to generate a new Erosion-Connectivity Mapping (ECM) framework. We evaluate ECM accuracy with field assessment of thirty-five sites spread across five lowland watersheds (mean slope <5°) in Johnson County, Kansas, USA, which differ primarily in their land use, ranging from 21% to 89% urban. RUSLE modeling results indicate erosion is controlled by topography with high risk areas near streambanks roadway systems. SDR and IC were positively related at the five sites (R2 = 0.78, p < 0.05) with the highest values in the most urbanized watershed, indicating that anthropogenic change augments connectivity. The ECM results indicate that while only 5±1% of the study area is both highly erodible and highly connected, these areas represent 37±4% of total watershed-scale erosion. Our modeling results indicate that erosion is more likely to be the limiting factor in sediment transport, as opposed to connectivity, as there are generally more locations that are well-connected to hydrologic transport but resistant to erosion. Our field assessment provided broad support for the ECMs; however, field assessment indicated that geospatial modeling underpredicts how closely related erosion and connectivity are in the field and we suggest that future models consider this coupling more explicitly. This study provides a method for combining RUSLE and IC in a new tool (ECM) to identify spatial patterns in sediment erosion-connectivity to aid in the understanding and management of watershed sedimentation.

Real time monitoring of material erosion and deposition for the first wall using quartz crystal microbalance in EAST

Abstract Two new quartz crystal microbalance (QMB) systems have been installed at different locations in the mid-plane of EAST to measure erosion and deposition of the first wall materials. The two QMBs with different distances from the plasma show complex and distinct erosion and deposition behavior. The QMB in the mid-plane H port closer to the plasma shows a relatively higher net erosion result with an average erosion rate of 1.34 ng/(cm2s). The normal discharges mainly contribute to the total net erosion and the maximum erosion amount reaches up to 110 ng/cm2. Contrarily, a slight net deposition of 0.11 ng/(cm2s) is obtained for the QMB in the mid-plane G port further away from the plasma and the erosion and deposition amount of most discharges are much lower due to lower particle flux. The disruptive discharges lead to a total net deposition rate of 0.48 ng/(cm2s). Measurement results by the QMBs are demonstrated by a good agreement with the post-mortem analysis by Rutherford Backscattering Spectrometry (RBS).

Effect of watershed geomorphological characteristics on sediment redistribution

Sediment budget is a valuable tool for describing the sediment production, transfer and storage in a watershed and its components depend on different watershed physical properties. The present study aimed to evaluate the relationship between 22 geomorphological factors and sediment budget components in a small mountainous watershed in the west of Iran, using ordinary least square, geographically weighted regression and bivariate regression. The distribution map of erosion and deposition was prepared using 137Cs in 15 sub-watersheds and the internal area. According to the results, the maximum net erosion rates were related with the sub-watersheds with medium slope (<20%) which strongly reveals the role of landuse and its interaction with the slope steepness. In addition, the mean sediment delivery ratio for 15 sub-watersheds was 28.43%, which decreased to 12.63% by increasing the area to the whole watershed due to trapping and redepositing mainly because of low slope agricultural lands close to the outlet. This finding reflects the interaction effects of the area and slope on the reduction of sediment delivery ratio by increasing the probability of trapping and redistribution of sediment. The Gravelius's shape index, equivalent rectangular width, and order of the main river were the most related geomorphological factors with total erosion and deposition. It is possible to estimate net erosion and sediment delivery ratio using equivalent rectangular width and topographic wetness index, respectively. The most important factor on sediment budget in the study area was topographic wetness index, probably because it depends on the slope as well as hydrological properties of the sub-watersheds.

Application of microbially induced calcium carbonate precipitation (MICP) in sand embankments for scouring/erosion control

Embankment is vulnerable to scouring and erosion during heavy rainfall events in most coastal areas in China. In this study, microbially induced calcium carbonate precipitation (MICP) technique was applied for sand embankments for scouring/erosion control. Three small-scale MICP treated sand embankments and one untreated embankment were first prepared using the injection method. Then, a series of laboratory scouring/erosion experiments were performed to investigate the slope failure process. The total erosion mass, the soil detachment rate and the content of MICP induced calcium carbonate (CaCO3) were also measured to evaluate the effectiveness of MICP treatment in sand embankments. Experimental results revealed that the average CaCO3 content was increased by 2% with each increment of MICP treatment cycle. The anti-scouring/erosion performance of MICP treated sand embankments was significantly improved as compared to the untreated one. Scanning electron microscopy (SEM) technique was also used to further study the micro-mechanism of the MICP treatment. The results revealed that the MICP induced CaCO3 was formed at the contact points among sand grains that increased the bonding strength, resulting in an improvement of scouring/erosion resistance of the treated embankment. This study preliminarily investigates the feasibility of using the MICP technique to mitigate scouring/erosion of sand embankment in coastal areas. More complicated environmental factors need to be considered for field implementation in the future.

Quantification of mudcracks-driven erosion using terrestrial laser scanning in laboratory runoff experiment

Understanding rill development and erosion rates is crucial for understanding changes in hillslope morphology and soil erosion. Mudcracks, a widely distributed feature on the land surface, play an important role in erosion, but the quantitative relationship between mudcracks and erosion has seldom been reported. Thanks to advances in terrestrial laser scanning (TLS, also known as terrestrial LiDAR), topographic changes can be observed at high resolution. This study is designed to quantify the effects of mudcracks on erosion. Mudstone specimens with and without mudcracks were analyzed. Using TLS, we quantified the millimeter-scale effects of mudcracks on slope erosion and rill development in laboratory experiments with well-controlled samples and water discharge. The point cloud data collected by TLS were then converted to digital elevation models (DEMs) for DEM of difference (DoD) analysis. The results show that mudcracks facilitate rill development. In the early stage of the experiment, the erosion depth of the cracked mudstone is twice that of the surface without cracks, and the total erosion amount is more than twice. During the experiments, the dominant erosion pattern changes from sheet erosion to rill erosion and then lateral erosion. Moreover, our study highlights the potential of TLS and DoD for high-resolution spatio-temporal topographic surveys to identify and characterize micro-relief-induced erosion.

ANALYSIS OF THE EVOLUTION OF GULLY EROSION IN OLIVE GROVES USING PHOTOGRAMMETRY TECHNIQUES. RELATIONSHIPS WITH RAINFALL REGIME

Abstract. Gully erosion is one of the main processes of soil degradation, reaching 50%–90% of total erosion in basins. As erosion processes are related to rainfall regime, the depletion and deposition rates can be increasing in a climate change scenario. This paper deals with the quantification of erosion processes in an active gully affecting olive groves of the province of Jaén (southern Spain), using geomatics techniques (photogrammetry and LiDAR). Eight historical aerial flights from 1980 to 2016, a LiDAR dataset (2014) and 2 recent UAS surveys (2019–2020) were used and processed in a common reference system with the support of field GNSS ground control points. Then, DSMs and orthophotographs were obtained and DSMs of differences (DoDs) calculated, from which we can identify gullies, calculate the depletion and deposition areas, and estimate height differences and volumes involved. These analyses result in an average depletion of about −1.6 m (incision) and a waste volume up to 30000 m3 (soil losses), which lead to a rates of −0.05 m/year and −44 t/ha*year, respectively. These rates are very different along the considered periods, reaching the maximum values (near −300–450 t/ha*year) in 2009–2011 and 2011–2013, coinciding with the periods of higher rainfall in the last fifty years, that probably have underwent an increase of 10–30% in the last decades. Thus, the evolution of the gully area for 40 years has been analysed in relation to the rainfall regime that has been established from the daily rainfall data.

Experimental and computational analysis of the erosion behaviour of unidirectional glass fiber epoxy composites

A 3D finite element model to understand the erosion behaviour of unidirectional glass fiber/epoxy (GF/EP) composites by the impact of Al2O3 erodent particle is presented. The erodent particles are impacting at a constant velocity of 100 m/s. A multi-scale modelling technique is presented and the results are compared with experiments. The multiscale approach involves a heterogeneous microscale model containing the information of fibers and matrix and is centrally embedded in an equivalent homogeneous macroscale surrounding part. The multiscale model captures the plastic deformation and localized bending deformation in the fibers and elucidates the role of both matrix and fiber in governing the total erosion behaviour of the composite. The results from the multiscale model are in good agreement with the experimental results in terms of the mechanisms involved and the erosion behaviour of the composite. The erodent particle shape effect was also studied. The point of contact of the particle depends on the shape of the particle. The erodent particle shape was found to play an important role in the erosion process. The peak value of erosion depends on the point of contact of the erodent particle and shifts to a shallow angle as the point of contact decreases.

Assessment of radiographic progression in patients with rheumatoid arthritis treated with tofacitinib in long-term studies.

ObjectivesTofacitinib is an oral Janus kinase inhibitor for the treatment of RA. We evaluated radiographic progression in tofacitinib-treated patients with RA for up to 3 years in two pooled long-term extension (LTE) studies (ORAL Sequel; A3921041) (primary analysis), and for up to 5 years using data integrated from one phase (P)2 (A3921068), two P3 (ORAL Start; ORAL Scan) and two LTE studies (exploratory analysis).MethodsIn LTE studies, patients received tofacitinib 5 mg twice daily (BID) or 10 mg BID as monotherapy or with conventional synthetic (cs)DMARDs. Radiographic outcomes up to 3 years: least squares mean (LSM) change from baseline in van der Heijde modified Total Sharp Score (ΔmTSS), erosion score (ΔES) and joint space narrowing (ΔJSN) score; proportion of patients with no radiographic progression (ΔmTSS ≤0.5); proportion of patients with no new erosions (ΔES ≤0.5). ΔmTSS was evaluated for up to 5 years in an exploratory analysis.ResultsFor all tofacitinib-treated patients with radiographic data available at LTE month 36 (n = 414), LSM ΔmTSS was 1.14, LSM ΔES was 0.66, LSM ΔJSN was 0.74, and 74.3% and 86.2% of patients showed no radiographic progression and no new erosions, respectively. Similar values were observed regardless of tofacitinib dose, or whether patients received tofacitinib as monotherapy or with csDMARDs. In an exploratory analysis of integrated P2/P3/LTE studies, LSM ΔmTSS was 3.34 at month 60 (n = 269).ConclusionLimited progression of structural damage was observed in tofacitinib-treated patients up to 5 years, with similar results for tofacitinib used as monotherapy or combination therapy up to 3 years.Trial registrationClinicalTrials.gov (http://clinicaltrials.gov): NCT01164579; NCT01039688; NCT00847613; NCT00413699; NCT00661661.

Forest land prone to more soil erosion than cultivated land in the Chure hill of eastern Chitwan, Nepal

This study was done at Lothar-Pampha Watershed, located in the Chure hill of eastern Chitwan, inside the boundary of Rapti Municipality covering 121.83 km2 (12183.12 ha). The main objective of the study was to estimate the spatial distribution and the extent of soil erosion in the watershed using Geographic Information System (GIS) and Remote Sensing (RS) tool. Annual average soil loss was estimated by using the Revised Universal Loss Equation (RUSLE), RSdata using GIS platform, taking spatial variation of each factors. Data on Rainfall erosivity (R), Soil erodibility (K), slope length and steepness (LS), cover crops (C) and soil conservation practices (P) were calculated from laboratory analysis and also retrieved from Landsat image. Soil sample were taken to determine the K factor from the 71 different areas inside the research boundary of Rapti Municipality. Rainfall data of 21 years from 21 different nearby stations were taken from the Department of Hydrology and Meteorology, Nepal (DHM). The soil erosion was categorized into seven classes as, extremely severe (&gt;190 t ha-1 year-1), very severe (100-190 t ha-1 year-1), severe (50-100 t ha-1 year-1), high (10-50 t ha-1 year-1), moderate (5-10 t ha-1 year-1), slightly (2-5 t ha-1 year-1), and very slightly (0-2 t ha-1 year-1) that occurred in 0.0043 %, 0.0862 %, 0.98 %, 29.71 %,18.34 %, 13.54 %, and 37.31 % of total area of Lothar-Pampha watershed, respectively. The total soil erosion estimated from the forest area (70.11 %) was 89537.29 t year-1 whereas from grasslands area (0.25 %) it was estimated as 81.03 t year-1, and from the agricultural land (18.10 %) it was 1529.52 t year-1. The maximum erosion rate (275.36 t ha-1 year-1) was estimated in the forest area followed by grasslands (22.19 t ha-1 year-1). Average soil erosion rate in settlement area was estimated as 0.27 t ha-1 year. Likewise, 8.87 % of total erosion was estimated from the agricultural land. Forested land is seemingly contributing to more soil erosion than agricultural land due to steep land topography, poor conservation program, deforestation, and unscientific forest management practices which seek for scientific forest management plan including soil conservation measures such as grass waterways, terracing, contouring, strip-cropping in Lothar-Pampha watershed of the Chure range.

Modeling soil erosion between 1985 and 2014 in three watersheds on the carbonate-rock dominated Guizhou Plateau, SW China, using WaTEM/SEDEM

The Guizhou Plateau, SW China is largely underlain by carbonate rocks. Because soils are thin, soil loss remains a serious problem despite low erosion rates. Further understanding the impacts of changes in rainfall, land use and differences in topography on sediment yield and delivery may assist in the development of suitable policies to reduce soil erosion on the plateau. A spatially distributed soil erosion and sediment delivery model (WaTEM/SEDEM) was applied to investigate temporal–spatial changes in soil erosion between 1985 and 2014 in three watersheds (Dadukou (DDK), Caopingtou (CPT) and Gaoche (GC)) located in the southwest Guizhou Plateau. The WaTEM/SEDEM model was calibrated and validated using data on sediment yields measured at the watershed scale. The total sediment yield (SY) and soil erosion modulus (SEM) firstly decreased followed by an increase, whereas the sediment delivery ratio (SDR) remained almost unchanged over the 30-year period. The major sediment source was dry farmlands. SY was the highest in the largest DDK watershed. The highest SEM occurred in the CPT watershed due to steep terrain and high ratio of dry farmland areas on steeper slopes. SEM was the lowest in the GC watershed where slope gradient and ratio of dry farmland on steeper slopes are low. SDR was the highest in the GC watershed because of its topographic characteristics. SEM was sensitive to precipitation fluctuations in the GC, DDK and particularly in the steep and intensively eroded CPT watershed, while changes in dry farmland ratio influenced the SEM in the CPT and DDK watersheds but not in the gentle and mildly eroded GC watershed. Changes in forest ratio had significant impacts on SEM only in the GC watershed. Since responses of soil erosion to variations or differences in the main impact factors differ in the different watersheds, soil conservation strategies should be watershed specific.