Siltation

About: Siltation is a research topic. Over the lifetime, 1420 publications have been published within this topic receiving 20983 citations.

An Estimation of Soil Erosion Rate Hot Spots by Integrated USLE and GIS Methods: a Case Study of the Ghiss Dam and Basin in Northeastern Morocco

Abstract: Soil erosion is a major factor leading to dams’ siltation and reducing their storage capacity. This study mapped the hot spots of soil erosion areas to predict the soil erosion/siltation in the Ghiss basin/dam (northeastern Morocco). In this context, various data has been prepared in the geographical information system for the estimation of soil erosion by integrating the universal soil loss equation (USLE). The result of this study revealed that soil loss rate ranges between0 and 19 t∙ha−1∙yr−1. Therefore, the hot spots in the soil erosion area are to be found upstream, potentially leading to dam siltation over time. To avoid Ghiss dam siltation, we suggest terrace farming and reforestation in the soil erosion area hot spots.

Impact Assessment of Alternate Land Cover and Management Practices on Soil Erosion: A Case Study

Abstract: Climate, soil, vegetation, topography, and man are the factors that affect soil erosion, and out of these vegetation and soil to some extent are the only factors which man can control. Fertile soil by carrying erosion fills dam reservoir and reduces dam’s economical life, hence economy of country get debilitated big amount. To specify hazard and damage of soil erosion is very important for this reason. Among many environmental hazards, checking land degradation is of utmost importance as it has direct bearing on decline in productivity on arable and non-arable lands. To prevent the erosion and rapid siltation, management of water, soil cover, and vegetation resources on watershed is must. In the present study, expected soil loss from Bina river watershed of Betwa river basin has been estimated using USLE model in GIS platform. The total soil about 4% of the total geographical area of the Bina watershed was found under very severe erosion category having erosion rate more than 120 t/ha/year, whereas the average soil erosion for the Bina basin was found to be 8.7 t/ha/year. Impact of alternate land cover management practices have been analyzed by hypothetically assigning the alternate land use practices and changing the values of controlling factors of USLE model accordingly. The best management practices which increase the food production and also control the soil erosion have been suggested.

Modelling soil erosion risk and its impacts in the mediterranean area for the 21st century

Abstract: Soil degradation and erosion will be influenced during the 21st century both by climate and related or anthropogenic land use changes. Many current negative impacts of soil erosion may thus be amplified, and as certain soil thresholds are exceeded, potentially new and different problems could arise. Soils in the Mediterranean environment may be particularly vulnerable to such global changes because of contrasted climate, low vegetation cover and specific poor soil characteristics. It is therefore crucial to understand the potential impacts of global change on soils erosion and its consequences on soil functions such as support of vegetation, local water balance, loss of organic matter (on-site impacts) as well as on sediment transfer in surface water reservoirs (off-site impact). The objective of the work presented here was to improve our understanding of the impact of global change, as it can be predicted by currently used global change scenarios for the period until 2100, on soil resources and to develop indicators and models for soil vulnerability assessment within the Mediterranean basin. Specific drivers of soil erosion affected by the global change were identified and their impacts on erosion processes were quantified using erosion models at small and medium catchments scales. Soil vulnerability indicators were developed from the use of these models for the assessment of soil depth reduction and the siltation of reservoirs. The project also developed uncertainty analysis and validation of erosion prediction using results of field investigations in three test areas in France, Tunisia and Morocco

Siltation and Desilting Practices in A Runoff Reservoir on Heavy Sediment-Laden River

Abstract: Sediment deposition in the reservoir of run-of-the-river power station is severe, in this paper we take upper Marsyangdi reservoir as an example to analyze sedimentation and desilting process according field data measured from September 2016 when the reservoir had just been impounded in order to find strategy for managing reservoir sedimentation. The ratio of Upper Marsyangdi reservoir capacity and volume of sediment into the reservoir is about 0.2. The reservoir arrived silt-stable in a year after impoundment with a depth of 12m deposition at the dam site. Most of sediment deposit in the periods that at the initial and the end of flood reason and it is found the flow rate is the key factor influencing trap efficiency because that due to damming velocity of medium flow decreased significantly compared to natural condition which caused numerous deposition. Based on result of analysis of deposition the desilting condition is determined. Empty flushing is proposed to release deposition after flood season when flow rate is greater than 100m3/s and the new capacity will last to next flood season. In order to reduce sediment concentration into diversion channel a desilting should be done in flood season when flow rate is larger than 200m3/s and flow rate for impound should not be more than 1/10 of that into reservoir which can avoid deposition during impoundment near dam site. 1 Research background It is usually necessary to build reservoirs in order to generate electricity in hydropower stations. However, during the process of reserving river water, reservoirs also intercept large amounts of sediment. According to the statistical data of 2001, the annual average amount of silt in the world’s larger reservoirs accounted for 0.5% to 1% of the reservoirs’ remaining storage capacities[1]. These sediment accumulations not only occupy large amounts of the storage capacities, but also cause abrasions to the turbine blades of the hydropower stations[2, 3]. Therefore, the reservoirs which have been constructed on sandy rivers generally have larger capacities, in order to include sufficient space for containing silt and siltation, and to reduce deposition by reservoir regulation for the purpose of maintaining the long-term operations of both the reservoirs and the power stations[4]. However, due to limited development conditions, some runoff power plants have been gradually constructed on sandy rivers in recent years. For these power plant reservoirs, silt and sediment can be easily deposited, which have negative effects on the normal operations of the power stations. The existing research findings have mainly focused on the siltation processes and treatment measures of large reservoirs[5-10]. At the current time, studies regarding the siltation processes and causes of silt accumulations in the runoff power station reservoirs are lacking. The Upper Marsyangdi Power Plant in Nepal is a typical runoff power plant located on a sandy river. Since its completion, sediment and silt deposits have rapidly accumulated in the reservoir area. In this research study, the actual measured water and sediment data from the Marsyangdi Power Plant were used for analyzing the processes and causes of the siltation in the reservoir. The key factors affecting the siltation processes were determined, and desilting suggestions for this particular reservoir were proposed according to the analysis results. The Upper Marsyangdi Reservoir is located in the upper reaches of the Marsyangdi River of Nepal. The normal water level is 902.25. The back-water height at the front of the dam is approximately 14 m. The total storage capacity under normal water level conditions is approximately 500,000 m3. The reservoir barrage is located on the Marsyangdi River. The Nardi River flows as a tributary to the Marsyangdi River at an upstream position 150 m from the dam. In September of 2016, the Marsyangdi Power Station had begun to officially store water and started to generating power. Also, a systematic observation of the sediment transport in the reservoir was carried out from March 27, 2017 to November 20, 2017, in order to obtain comparatively complete data of the landforms; water; silt and sediment; reservoir inflow process; sediment concentration process; sediment grading; and water levels in front of the dam. The measured section position is shown in Fig. 1. , 0 (2018) MATEC Web of Conferences https://doi.org/10.1051/matecconf/201824601062 246 10 ISWSO 2018 62 © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/).

Prospects for fish culture in char areas of Bangladesh

Abstract: Fish production is considered in the barren chars or sandy land masses created through siltation along river banks and deltas in Bangladesh. The prospects for fish culture in ponds and cages or pen culture in rivers and canals are examined. The socioeconomic implications of fish culture as a livelihood source for communities living in char areas are also discussed.