Soil Conservation Projects Research Articles

Rapid Increase in the Lateral Transport of Trace Elements Induced by Soil Erosion in Major Karst Regions in China.

Soil erosion, which has been recently shown to significantly perturb carbon cycling, occurs naturally but can be either enhanced or reduced by human activities. However, the impacts of soil erosion on terrestrial contaminant cycles remain unclear. Here, we select eight trace elements, i.e., arsenic, cadmium, chromium, copper, nickel, lead, zinc, and mercury, to examine the erosional impacts of the elements' fate and transport across China. By synthesizing the detailed distribution of soil erosion fluxes, soil element inventories, and diverse modeling methods, we reveal that while human activities have reduced the lateral transport of these elements in the Loess Plateau (Central North China, a 56% decline in the past two decades with a range of 46% to 110%) due to soil conservation projects, they have increased these transport fluxes in China's major karst regions (Southwest China, a 84% increase with a range of 55% to 150%) because of severe rocky desertification. These fluxes have completely overwhelmed the soil conservation efforts in the Loess Plateau. Fluxes of these elements into aquatic environments from Southwest China reached 46% of the total input in China in 2010. These fluxes were higher than the inputs from point sources in the region by a factor of 50 because of impacts of excessive agricultural cultivation and geographical and climatic factors. These findings indicate the enormous perturbation of terrestrial contaminant cycles caused by soil erosion in karst regions and demonstrate the need for long-term sustainable management of soil erosion and contaminant discharge to protect fragile terrestrial ecosystems.

Effect of VOCs pollutants on strength of cemented soil

Based on the soil conservation project of a chemical plant in Zhenjiang, the effects of volatile organic compounds (VOCS) pollutants on the strength of cement soil were studied experimentally. Xylene was utilized for indoor experiment. The specimen was made of water, xylene solvent, gray yellow clay and 42.5 ordinary Portland cement in a certain proportion. Firstly, the influence of the content of xylene on the unconfined compressive strength of cemented soil with time was analyzed, and then the effect of cement blending ratio on the unconfined compressive strength of samples containing xylene was studied with the increase of time. The results showed that the unconfined compressive strength of cement-soil samples increase with the increase of time and decreased with the increase of xylene content in similar curing time; the same xylene incorporation and the unconfined compressive strength of cement soil samples increased with the increase of cement incorporation ratio. In addition, the author also verified the impact of VOCs pollutants on cement-soil retaining walls by simulating actual engineering, and proposed two solutions which were expected to advise the engineering.

Spatio-temporal Evolution and Factors Influencing the Control Efficiency for Soil and Water Loss in the Wei River Catchment, China

With regard to important scientific and policy issues in the Wei River Catchment, much emphasis has been put on the objective assessment of the effectiveness of ecological restoration measures and the analysis of effective ways to promote the efficiency of ecological management. Based on an interdisciplinary approach, the present study investigates the measurement of the control efficiency for soil and water loss induced by the Sloping Land Conversion Program and terrace fields, a part of the Water and Soil Conservation Project, in an attempt to detect and quantify indicators of different fields to do so. The applied methods included a Bootstrap Data Envelopment Analysis model which covers 39 counties over the period of 2000–2015. Then, an exploratory spatial data analysis was conducted to capture the spatial characteristics for the control efficiency of each county. Finally, the geographically weighted regression model was employed to identify the spatial heterogeneity and evolutionary characteristics in the relationship between control efficiency and natural conditions and socioeconomic development in each sample county. Results show that the control efficiency increased from 0.263 to 0.365 during the study period. In addition, the Moran’I indicates that efficiency presented a stable spatial agglomeration but still at a low level, from 0.192 to 0.151. The difference in control efficiency is the result of a combination of multiple factors, of which the most relevant factors often vary among different counties, indicating that regional governments should consider full-scale initiatives. This analytical perspective helps to provide experience and reference for countries facing the same environmental challenges in the world.

Migration and Land-Use and Land-Cover Change in Burkina Faso: a comparative case study

<p>In the Sahelian country of Burkina Faso, West Africa, population pressure, poor resource management, and reduced rainfall have exacerbated land degradation. A rapidly growing population coupled with high rates of internal rural migration and thirty years of desiccation have resulted in profound land-use/land-cover change (LULCC) throughout the country. In the Central Plateau and northern regions of Burkina Faso, land degradation has historically stimulated large-scale out-migration toward more fertile areas in the south. While some northern provinces are being rehabilitated by Soil and Water Conservation (SWC) projects, southern provinces, considered more "pristine", have been neglected. In recent decades, researchers have attributed the initiation of land degradation processes in southern regions to this influx of migrants from the north. This study presents an empirical controlled case study between two provinces to better understand the dynamics of migration and LULC. One province, Bam Province in the north, has long been a zone of departure while Sissili Province in the south has long been a destination zone. Using a regional political ecology framework, we integrate a time series of LULCC data with demographic census data and local narratives to compare migration and LULCC trends in Bam and Sissili from 1975 to 2013. We find that in-migration correlates with substantial and dramatic LULCC while out-migration is associated with only moderate LULCC. This controlled comparison also suggests that local land-use/land-cover change and migration dynamically interact. As environmental conditions in Bam improve and Sissili deteriorate, long-term trends of either out- or in-migration for either province stabilize, and can even become reversed.</p><p><strong>Key Words</strong>: Burkina Faso, LULCC, migration, regional political ecology</p>

Effects of restoration practices on controlling soil and water losses in the Wei River Catchment, China: An estimation based on longitudinal field observations

Understanding the soil and water processes and their interactions over time and space has attracted research and policy attention worldwide. But past studies have rarely adopted an interdisciplinary approach to integrating the primary natural and social forces in assessing the causes of soil and water loss or conservation. The purpose of this study is to evaluate the effects of restoring degraded cropland by means of reestablishing forest/vegetation covers and terracing on water and sediment control in the Wei River Catchment, which was notorious for its high erosion rates but has witnessed tremendous improvement since the beginning of the new century. Based on a unique panel dataset covering 44 counties over a period of 16 consecutive years (2000–2015), our simultaneous equations model was able to capture the structural linkages between water runoff, sediment concentration, and sediment transport. To highlight the crucial role of human interventions, a stepwise regression approach was undertaken. Our empirical results show that the reduction of sediment concentration has been driven largely by improved land cover, induced by implementing the Sloping Land Conversion Program, whereas terracing, as part of the Water and Soil Conservation Project, has played a positive role in mitigating runoff and sediment discharge.

Assessment of potential changes in soil erosion using remote sensing and GIS: a case study of Dacaozi Watershed, China.

Soil erosion is a major global environmental problem. Therefore, a method of calculating potential soil erosion is necessary for soil and water resource management, as well as for assessing the risk of soil erosion. This study aimed to develop a simple method for calculating potential soil erosion change (PSEC) by combining the Universal Soil Loss Equation (USLE) and a Geographic Information System (GIS). The USLE model includes a rainfall erosivity factor (R), soil erodibility factor (K), cover management factor (C), slope gradient factor (S), length factor (L), and the supporting practice factor (P). Using a measured patch of soil and water conservation as the experimental unit, weather and soil data were combined to calculate R and K. Remote sensing images were used to extract vegetation cover (VC) and calculate C, while digital elevation models were used to extract and calculate S and L; land use maps were used to determine the P of each patch. The PSEC of each patch was then calculated according to the results of the above mentioned six factors. Finally, the PSEC of the entire study area was calculated on the basis of a patch area weighting method, which was validated in the Dacaozi Watershed in China, where a 1-year soil and water conservation project was implemented, beginning in November of 2013. In this study, the PSEC of the Dacaozi Watershed in May of 2017 was calculated, accounting for approximately 3years of project implementation. The results showed that the average VC increased by 21.6% after 3years of project implementation, whereas C decreased by 46.4%. The value of P did not change significantly from before to after project implementation. The average S decreased from 22.6 ± 12.1° to 21.3 ± 10.6°, and S decreased by 6.8%. In contrast, L increased by 33.3%. On the whole, the PSEC in the Dacaozi Watershed was 0.3925 and the potential soil erosion decreased by 60.75% after 3years of conservation.

Experimental and numerical simulation of flow over stepped spillways

Stepped spillways are used in the construction of dams, river engineering and soil conservation projects. Energy dissipation in this structure due to the presence of several steps is high, so the construction costs for stilling basin are reduced. The numerical models are new method for flow analysis. This study investigates the flow on the stepped spillway and calculates energy loss caused by it. Also in this study, fluctuation of velocity vectors, shear stress and pressure during the flow on each step is compared. For this purpose, a physical model of the stepped spillway was built with slope at a ratio of 2:1 (horizontal to vertical) and experiments were performed with ten different flow rates. The numerical simulations also were performed under the same conditions using FLUENT software and RNG k–ε turbulence model. Finally, the results of the numerical model were compared with experimental data. The results indicate that numerical model is in reasonable consistency with the physical model and it can be used in anticipation complex rotational flows in the stepped spillway.

Persistent impact of human activities on trace metals in the Yangtze River Estuary and the East China Sea: Evidence from sedimentary records of the last 60 years

Three sediment cores taken from the Yangtze River Estuary (YRE) and the East China Sea (ECS) in 2016 were analyzed for trace metals (Pb, Zn, Cu, Cr and As), major elements (Al, Fe and Mn), sediment composition, chemical properties (Eh and pH), and natural/artificial radionuclides (210Pb/137Cs) to decipher the high-resolution historical variation in anthropogenic metals over the past 60 years. The results showed that anthropogenic Pb was primarily derived from atmospheric deposition, while anthropogenic Zn, Cu and As were carried out by fluvial discharge. In the YRE, the recent decrease in sedimentary metals could be largely a result of intensified erosion, which was triggered by the construction of dams in particular the Three Gorges Dam (TGD) in 2003 and soil-conservation projects. In comparison, sedimentary records in the deposition-dominated environment of the ECS showed that anthropogenic Pb and Cr began to gradually increase following 1970, but a remarkable increase in anthropogenic Zn and Cu occurred in 1990, probably reflect the different origins and dispersion pathways of these elements. Anthropogenic Pb and Cr exhibited a sharp decrease near early 2000s due to increasing investment in treating pollution. Being sensitive to the substantial reduction in riverine particulate flux of Zn and Cu from the Yangtze River, the concentrations of anthropogenic Zn and Cu in the cores decreased by 5–27% in 2005–2016. Furthermore, a prominent increase trend of As record after 1990, probably due to the excessive pesticides used in agricultural activity.

Influence of freeze-only and freezing-thawing cycles on splash erosion

Soil erosion is recognized as one of the most important types of land degradation in the world particularly in many developing countries like Iran. Water erosion is initiated by splash erosion triggered by raindrop impact. Understanding the process of splash erosion under freezing and thawing conditions is essential to unravel soil erosion mechanisms under temperate conditions leading to appropriate planning of soil and water conservation projects. The present study aimed to study the individual effects of freeze-only as well as freezing-thawing cycle on splash erosion in a loess soil from an erosion prone area in mountainous northern regions of Iran. The study was conducted under laboratory conditions using erosion plots. The erosion plots were subjected to freeze only and freeze-thawing treatments by simulating cold conditions using a large cooling compartment system specifically manufactured for this purpose. The splash erosion under a designed simulated rainfall (1.2 mm min−1 for 30 min) was then measured as upward, downward and net splash erosion in splash cups. The results showed that freeze only decreased the upward, downward and net splash erosion by 0.81 ± 0.43, 0.82 ± 0.29 and 0.85 ± 0.23% while freezing-thawing cycle decreased splash erosion to 0.93 ± 0.83, 0.61 ± 0.43 and 0.57 ± 0.36%. This may be attributed to temporary increase in soil strength and stability or surface sealing during freezing process leading to reduced splash erosion.

Economic assessment of the investment in soil and water conservation projects of watershed management

In order to ensure investments in soil and water conservation projects, impact assessment and economic analysis of these projects are necessary. The purpose of this study was economic evaluation of watershed management practices in Parrud catchment of Qazvin Province, Iran. For this purpose, the changes caused by the implemented projects (including various biological, biomechanical, mechanical, and managerial practices) are measured quantitatively. Then, the total costs of the implemented measures along with the revenues from the changes were calculated. Lastly, the economic evaluation of the project is carried out using net present value (NPV) method. The results show that 115,000 m3 more runoff storage has been carried out annually. Also, there has been an increase of 163.9 t/h/year in the total rangeland production and 57.6 increase in hectares of the area of orchards, and the erosion rate has dropped from 13.98 to 10.23 t/h/year. Economic appraisal of the projects indicates that during the first 5 years, the costs have risen, but since the sixth year, the NPV has increased so it has been positive since the eighth year onwards and will increase continually. These results demonstrate cost-effectiveness of the watershed management projects, and therefore, there is enough confidence to invest in these projects.

Estimating Sediment Moving into the Yellow River Based on Moving Process Analysis

Zhang, J., 2018. Estimating sediment moving into the Yellow River based on moving process analysis. In: Wang, D. and Guido-Aldana, P.A. (eds.), Select Proceedings from the 3rd International Conference on Water Resource and Environment (WRE2017). Journal of Coastal Research, Special Issue No. 84, pp. 163–168. Coconut Creek (Florida), ISSN 0749-0208.The sediment moving into the Yellow River has decreased in recent years. For instance, the measured annual mean sediment amount at Tongguan station showed a sharp decreasing trend from 15.9 × 108 t/a during 1919–1960 to only 2.5 × 108 t/a during 2000–2015, a change of 84%. This led to an increased interest in the movement of sediments into the Yellow River. However, the results and conclusions were quite different due to different data and methods used in different studies. Consequently, no widely acceptable understanding existed regarding the sediment movement into the Yellow River. In this study, firstly the main process of sediment moving into the Yellow River was analyzed in the area where the sediments mainly yielded due to hydraulic erosion, gravitational erosion, and sediment transport by water flow in the riverbed. Then, referring to soil erosion as the “three lines of defense”, the effects of water and soil conservation projects were discussed to estimate the amount of sediment moving into the Yellow River. Considering the effects of water and soil conservation projects, climate change, and human activities, the sediment in the Yellow River used in engineering design should be between 8 × 108 and 12 × 108 t/a for safety purpose, and at least 10 × 108 t/a for suggestion.

Rate and Distribution of Sedimentation in the Three Gorges Reservoir, Upper Yangtze River

AbstractSedimentation in the Three Gorges Reservoir (TGR) has been studied with a primary focus on the amount due to the decrease in sediment inflow caused by water and soil conservation projects a...

Research progress and harnessing method of soil and water loss in Pisha Sandstone region

Pisha Sandstone region is the most vulnerable and the most dramatic area of soil erosion, severe soil erosion on the ecological bases of China’s energy security constitutes a serious challenge. Research progress of soil erosion in pisha Sandstone region was reviewed based on the need of soil and water ecological construction in Pisha Sandstone region and harnessing the yellow river including soil erosion mechanism, soil erosion dynamic monitoring and soil erosion simulation assessments. Meanwhile, the latest progress of soil and water conservation measures was analyzed, and the existing problems and future harnessing measures of soil and water loss were discussed. This study is to explore the comprehensive management method and provide scientific theory for constructing soil and water conservation project in Pisha Sandstone region.

Assessment of groundwater potential zonation of Mahesh River basin Akola and Buldhana districts, Maharashtra, India using remote sensing and GIS techniques

The identification of suitable groundwater potential zonation was prepared using remote sensing and GIS techniques. Drainage pattern map were generated from satellite images using Arc GIS software. This study area was demarcated the groundwater exploration sites and artificial recharges structure with help of groundwater potential zonation map. The assessment of groundwater potential zonation was generated by integrated data like Slope, Hydro-geomorphic, land use/land cover, digital elevation maps with the help of remote sensing, GIS techniques and field verification. The Geomorphology, Land use and Land cover maps were prepared from Linear Self Imagine Scanning Sensor (LISS-III) satellite images with 23.5 m resolution using Arc GIS 10.3 software. The different kinds of thematic maps were integrated for assessment of groundwater potential zonation in basaltic hard rock terrain. These thematic maps of classes assigned weight ages using overlay analysis method. The groundwater potential zonation map was prepared using thematic maps for groundwater development. These thematic maps were assign numerical values like 1–10 using Arc GIS software 10.3. The groundwater potential zone classes has been shown like poor, moderate, good and excellent, which can be utilized for new sites of groundwater exploration and artificial recharges structures. The artificial recharge map generated from groundwater potential zonation using remote sensing and GIS technology. The groundwater potential zonation and artificial recharge maps may be useful for soil and water conservation project, watershed development programs and groundwater resources management in basaltic rock area.

Multiscale Correlation Analysis between Runoff and Sediment and Possible Underlying Causes in Jinsha River in a Changing Environment

Great changes have taken place in the sediment processes in Jinsha River because of human activities. The wavelet analysis and the cross wavelet transform was applied to analyze the variation of streamflow and sediment in Shigu, Panzhihua, and Pinshan hydrometric station. The multiscale correlation between Jinsha River sediment and runoff data was discussed. The result showed that the power spectrum of streamflow had the same variation in Shigu, Panzhihua, and Pinshan stations. The trends exhibited a great difference for sediment changes. For Shigu and Panzhihua stations, visible regions of six-month and below six-month bands in the entire time coordinate, which is a great significance period for sediment observation, were found. The significant variation was especially powerful from 1987 to 2009. These findings indicated that soil erosion in the upper and middle streams of Jinsha River became more serious starting in the 1980s. The sediment load in Pinshan station exhibited another trend over the significant periods. The six-month fluctuations disappeared from 2000 to 2009. This result showed that sediment content decreased from the Panzhihua to the Pinshan range. The sediment content of Jinsha River will continue to decrease in the future with ongoing water and soil conservation projects and hydropower development.

Methods for automatic identification and extraction of terraces from high spatial resolution satellite data (China-GF-1)

Terraces are effective measures to control soil and water loss on hillslopes and play significant roles in water storage, soil conservation and increasing of crop yield. With the launch of comprehensive management engineering of transforming slopes into terraces in China, the area of terraces is continuously expanding. To plan for soil and water conservation in a scientific way and ensure rational soil and water conservation measures, it is important to determine a timely and accurate inventory of the spatial distribution of the existing terraces. High-resolution satellite data (China GF-1) was used in this study to automatically identify and extract terraces. The edge characteristics statistics algorithm, template-matching algorithm and the Fourier transformation algorithm were used. The results suggest that the template-matching algorithm, based on high gray features of terraces, has higher identification accuracy and lower extraction miss rate, and is able to determines the complete map spots, which works well for identification and extraction of typical terraces. The Fourier transformation algorithm, based on the texture of the terraces, is easily affected by gray changes on the terrace field surfaces and field ridges and is hardly reliable as a stand-alone technique for terrace identification. In this study, we focused on an area near Hengshan County, Yulin of Shanxi Province, and performed field validation of the terrace automatic identification and extraction algorithms. The results suggest that the accuracy of automatic identification and extraction of the terraces is greater than 80%. The method proposed is helpful to meet the requirements for planning and monitoring soil and water conservation projects.

Impact of soil and water conservation measures on soil erosion rate and sediment yields in a tropical watershed in the Central Highlands of Sri Lanka

The Upper Mahaweli Catchment (UMC) is a very important watershed in the Central Highlands of Sri Lanka since it contains a series of multipurpose reservoirs. Hence, conservation of soil in the UMC should be given the highest priority to reduce sediment yields in streams and to maintain the storage capacities of hydropower reservoirs. The sediment yields measured in the sub-catchments of the UMC before 1995 have revealed that soil erosion is intense in the contributing catchments and siltation in some reservoirs is at an alarming level. The situation in the Upper Uma Oya, a sub-catchment of the UMC, is the worst, reporting the highest sediment yield measured for any catchment in Sri Lanka. Mahaweli Authority of Sri Lanka had embarked on two soil and water conservation projects in the Upper Uma Oya catchment from 1995 to 2005 together with monitoring of sediment yields in the stream. Sediment yield measurements in this catchment revealed that the wash load in the stream had been reduced by a factor of five after the implementation of conservation programmes in 1995. Our temporal analyses showed that the role of the other key factors that control soil erosion on a hillslope such as erodibility, slope, erosivity and land use cover is minimal to generate a five-fold reduction in the wash load of the stream. Hence, we report that the conservation measures adopted in the critical areas of the Upper Uma Oya have been very successful and had greatly contributed to the reduction of soil erosion. However, even after conservation, soil erosion rates estimated by stream loads are about 10 times higher than the natural background rate. Hence, as shown in other catchments elsewhere in the world, the ongoing rate of soil erosion can be further lowered by strengthening the existing soil and water management practices together with restoration of vegetation on bare lands.

Did streamflow or suspended sediment concentration changes reduce sediment load in the middle reaches of the Yellow River?

The continuous ecological restoration of the Loess Plateau, which aims to reduce the sediment entering into the Yellow River, is known throughout the world for two strategies: the integrated soil conservation project that began in the 1970s, and the “Grain for Green” project that began in the 1990s. However, the topic of whether the muddy water in the middle Yellow River run clearer remains debatable, and, in fact, response to the topic is reasonably well documented in regard to hydrological changes in the sediment source area. Six sub-catchments nested in the Beiluo River basin – one of the major sediment sources for the Yellow River – were selected, with data series ranging from 1957 to 2009. The Mann-Kendall and Pettitt tests were used for trend detection. A simple method was developed based on the distribution of suspended sediment concentration (SSC) versus water discharge. Using this method, we evaluated the quantities of sediment yield reduction attributed to streamflow and SSC changes due to the two strategies.The results showed that annual sediment yield in 5 out of 6 stations significantly decreased, with rates varying from −4 to −217t·km−2·yr−1. Significant decreases in daily and event streamflow and suspended sediment concentration were identified, especially at a high SSC (top 1–5%). During the integrated soil conservation period, the sediment yield was reduced mainly by decreases in high flow and high SSC conditions. In contrast, during the “Grain for Green” period, sediment yield was reduced due to decreases in streamflow and SSC at all magnitudes. It was concluded that rainfall-sediment load dynamics have changed in the context of ecological restoration. Changes in both streamflow and the SSC–water discharge relationship induced the sediment yield reduction over time; in other words, the streamflow in the middle reaches of Yellow River became clearer during periods of ecological restoration. Moreover, the increased annual sediment yield at the Zhangcunyi station exposed a risk of increased erosion in areas where forests had been well preserved.

Ground-truthing Sahelian Greening: Ethnographic and Spatial Evidence from Burkina Faso.

Historically, the Sahel of West Africa has been considered synonymous with desertification. In recent decades, however, satellite images reveal patterns of enhanced vegetation termed the "greening of the Sahel." This greening is well-documented but its mechanisms remain poorly understood. The Sahel is also a region emerging from a thirty-year period of reduced rainfall in which several severe droughts occurred. As a response to droughts and land degradation, farmers have rehabilitated thousands of hectares of degraded soils by constructing low barriers of rock through widespread soil and water conservation (SWC) development projects. Remote sensing analyses suggest that these extensive soil conservation projects may explain greening in northern Burkina Faso. This study combines ethnographic fieldwork with the analysis of Geographic Information System (GIS) and remote sensing (RS) data to test whether SWC investments contribute to greening. Ethnographic data reveals a tension between the perceptions of rural producers who feel that their SWC efforts contribute to greening and those of state officials who contend that SWC has only local impacts and that the regional landscape continues to degrade. Our analysis of GIS and RS data suggest that both perspectives are valid but contingent on particular spatial and temporal scale used for analysis.

Evaluation of soil and water conservation projects through estimation of erosion intensity by geomorphological modelling (case study of Safaroud watershed, Mazandaran Province, Iran)

Evaluation of soil and water conservation projects through estimation of erosion intensity by geomorphological modelling (case study of Safaroud watershed, Mazandaran Province, Iran)