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Globally, water and energy demands are increasing continuously, while the storage capacity of structures like dams and reservoirs is reducing due to sediment-induced problems. Study of the reservoir sedimentation is essential for restoring the storage capacities to ensure the increasing water and energy demands. This study suggested the methodology for preparing the revised elevation–area–capacity curve for a reservoir for its efficient use. Also, it focused on two important issues through an example—estimation of the loss of the live storage capacity of the reservoir due to sedimentation and remedial measures to regain the lost capacity. In the present study, reservoir sedimentation is estimated using satellite remote sensing technique (SRS) considering a case of the Ujjani reservoir located in Maharashtra State, India. The modified normalized difference water index (MNDWI) is employed to determine the water surface area using ERDAS Imagine software. The loss in live capacity because of deposition of sedimentation over 41 years is determined and estimated to be 174.592 Mm3 showing the rate of capacity loss as 4.26 Mm3/year, which is 11.23% loss of the original capacity under study zone. To regain the storage capacity of the reservoir, it is proposed to adopt manual and or mechanical dredging with flushing for desilting the deposited sediment in the reservoir.

Reservoir sedimentation can be overcome by reducing the amount of sediment that enters the reservoir, by building check dam. The check dam has more deposited coarse sediment load than fine sediment load. Fine sediment that escapes the check dam will flow further and eventually enter the reservoir pond. Therefore it is necessary to build a building that can capture fine sediments. Construction is planned as a system of sediment trap in irrigation channels. The purpose of this study is to analyze the possibility of applying the sediment trap in the river to deposit sediments that escape the check dam. The analysis begins with the selection of the location of the sediment trap, then calculate the dimensions of the sediment trap and the amount of sediment that has settled. Based on the analysis of the selected dimensions with several combinations of gradation of sediment grains, sediment deposition that occurs ranges from 42 - 68%. So it can be concluded making the sediment trap in the river can be done. However, for the application of these sediment traps further research is needed regarding the dimensions of sediment traps that are most optimal for sediment deposition.

Reservoirs are an important source of water supply, provide hydropower, reduce the deficiency influences, and provide flood protection. Due to the dam structure and reservoir founding, the releases from the dam has become more restrained and the hanging sediment concentricity summits have been decreased considerably and accumulated upstream the dam. Sediment siltation has increasingly reduced the efficiency of reservoir functionality throughout the years by declining the storage capability. Determining the reservoir sedimentation influence on the dam operation is important to holding current operation and preparing for future polices. The existing paper deals with the review and assessment of the reservoir sedimentation effect on operation of Aswan High Dam (AHD) in Egypt. A new simulation model was developed and calibrated for Aswan High Dam Reservoir (AHDR) to evaluate the reservoir sedimentation effects on the factors affecting the operation of the dam. These factors are Toshka spillway outflows, upstream water levels of AHD, dam safety, withdraw from the reservoir, the losses due to the evaporation and the hydropower generation from AHD. The results of the study displayed that the factors affecting the operation of AHD were affected due to presence of these deposits in AHDR. Therefore, the reservoir sedimentation effect should be considered to implement or develop of simulation models for AHDR.

This specific study was conducted on the Abrajit reservoir in east Gojjam, Amhara region, Ethiopia. The general objective of the study was to investigate reservoir siltation and determination of the remaining valuable life span of the reservoir using ArcGIS 10.5 version and Golden surfer 16 latest version. A bathymetric survey using echo-sounding equipment (Garmin GPSMAP421s) was conducted and a topo map of reservoir data was used for assessment of the sediment volume. The accumulated sediment volume was estimated by subtracting the triangular interconnected network (TIN) map of the initial bed level from the currently measured bed level. The result of the research revealed that to date, 343,700.1 m3 bulk of sediment was accumulated in the reservoir that reduces 20% of the total reservoir capacity. In the results from the bathymetric investigation and software analysis, annually 28,641.675 m3 year−1 amount of sediment is coming from the catchments to the reservoir that contributed 1.66% of annual reservoir volume reduction. The measured recent storing capacity for the Abrajit Dam was 1,388,870 m3. From a comparison of remaining reservoir storage and annual sediment load, the reservoir will not serve more than 12 years. The estimated specific sediment yield (SSy) was found to be 4733.387 ton km−2 year−1. Therefore, to improve the estimated life span of the reservoir, watershed management is very important and further study is required to identify the area where watershed conservation will focus in the future. Upon the findings, the reservoir volume is running to reduce and it cannot serve all the demand what it designed for during the dry season. As a result, operation curves should be mandatory to give water service for the critical water needs, and regular monitoring of sediment accumulation in the reservoir is recommended.

Soil erosion is exacerbated by unsustainable land-use activities and poor management practices, undermining reservoir storage capacity. To this effect, appropriate estimation of sediment would help to adopt sustainable land-use activities and best management practices that lead to efficient reservoir operations. This paper aims to investigate the spatial variability of sediment yield, amount of sediment delivery into the reservoir, and reservoir sedimentation in the Koga Reservoir using the Soil and Water Assessment Tool (SWAT). Sediment yield and the amount entered into the reservoir were also estimated using a rating curve, providing an alternative approach to spatially referenced SWAT generated suspended sediment load. SWAT was calibrated from 1991 to 2000 and validated from 2002 to 2007 using monthly observations. Model performance indicators showed acceptable values using Nash-Sutcliffe efficiency (NSE) correlation coefficient (R2), and percent bias (PBIAS) for flow (NSE = 0.75, R2 = 0.78, and PBIAS = 11.83%). There was also good agreement between measured and simulated sediment yields, with NSE, R2, and PBIAS validation values of 0.80, 0.79, and 6.4%, respectively. The measured rating curve and SWAT predictions showed comparable mean annual sediment values of 62,610.08 ton/yr and 58,012.87 ton/yr, respectively. This study provides an implication for the extent of management interventions required to meet sediment load targets to a receiving reservoir, providing a better understanding of catchment processes and responses to anthropogenic and natural stressors in mixed land use temperate climate catchments. Findings would benefit policymakers towards land and water management decisions and serve as a prototype for other catchments where management interventions may be implemented. Specifically, validating SWAT for the Koga Reservoir is a first step to support policymakers, who are faced with implementing land and water management decisions.

This paper is a concise report of International Research Project (Project Reference Number: 29W-01) entitled of Development of an Integrated Sediment Disaster Simulator and Application to Sediment Disaster Mitigation and Reservoir Sedimentation Management in the Brantas River Basin, Indonesia. The main objectives of the project are to establish an appropriate and adequate mechanism to support the sediment disaster mitigation and the sustainable reservoir sediment management through utilization of most collaborative-based technology on the development of integrated sediment disaster simulator and an establishment of monitoring system for sediment disaster management. We assessed the sediment transport processes in the upstream of Brantas river basin, analyze its potential sediment disaster, and then formulate adaptation strategies to reduce the loss of reservoir capacity. The selected site of this research project is Wlingi reservoir that is located on the southern skirts of Mt. Kelut. This basin is suffering from watershed erosion and heavily loads of volcanic ash ejected from the eruption of Mt. Kelut, the most active volcanoes in Indonesia. The methodology and approaches adopted in this project are then discussed with collaborators via project events for prescribing better accuracies of the improving model. The application of the integrated sediment disaster model to this mountainous watershed has been successfully providing detailed information on sediment transport processes in Wlingi sub-basin. The results show Wlingi reservoir to receive higher volcanic material as bed load and suspended load during high-intensity rainfall from the northern slopes of catchment and sheet erosion material as suspended load from the southern part of remaining basin. Overall, the results are useful to contribute in establishment of variety options to counter sediment disaster in the Wlingi reservoir.

Reservoir sedimentation is a process by which the sediment load carried by river settles at the bottom of reservoir. Conventionally, sedimentation rates are measured either directly by hydrographic surveys or indirectly by using the inflow-outflow records of a reservoir. These conventional techniques are expensive, time-consuming and require huge manpower, whereas, remote sensing is a cost-effective and time-efficient method. In the present study, the revised capacity of the Rihand reservoir built on Rihand river was assessed using remote sensing data. In the present study, assessment of sedimentation has been done for the Rihand reservoir using multi-date remote sensing data acquired from Landsat 8 OLI sensor for the year 2018–2019. The water spread area of the reservoir was mapped using the thresholding technique which is based on NDWI and unsupervised classification of multi-spectral datasets. Using a modified trapezoidal formula, the revised cumulative capacity of the reservoir was calculated. According to the results of the hydrographic survey provided by the dam authorities, the live storage capacity of Rihand reservoir in the year (2000–2001) was 2932.87 Mm3 at 263.17 m water storage level. Revised live storage capacity estimated in the present study using optical data (2018–2019) was assessed to be 2618.26 Mm3 at 263.17 m. Therefore, loss in reservoir capacity in the past 19 years is estimated to be about 314.61 Mm3, which gives an average sedimentation rate of 16.52 Mm3/year. This study highlights the potential of remote sensing data in the assessment of reservoir sedimentation.

Lakes and dams located in sediment-laden rivers infill with time which reduces the storage capacity and consequently the quality of aquatic life. Anthropogenic activities in Kenya’s Murera watershed have had significant impacts on storage capacity and water quality of Murera reservoir which inturn affects aquatic ecosystems. This study focused on the reservoir sedimentation assessment and examination of the sediment impacts on the storage loss in Murera reservoir dam. This was achieved by establishing the engineering concepts using the Bathymetric Survey System (BSS) comprising of navigation twin boat system (Dual Jon-boats) with an in-built Global Positioning System (GPS) for collecting spatial data. A multi-frequency acoustic system with frequencies of 200,50 and 12 kHz was used to determine the reservoir bed level, part of sediment layers, and deposited sediments, respectively, to pre-impoundment levels of the reservoir. Data processing and analysis were performed using Depthpic 5.0.2 Surfer 15.5, and ArcGIS 10.3 software. The results show that the reservoir depth increased from the North part to the South part of the reservoir with a maximum depth of 7.78 m and the reservoir water storage of 707,862.03 m3. Sediment deposition is concentrated in the southern part compared to the north part of the reservoir. The sediment layer thickness varied from 0 m up to 0.8 m (maximum) and the total sediment storage capacity of 117,683.39 m3, this implies that the reservoir lost 14% of its actual storage capacity. Results from this study provide pertinent information to policymakers in Kenya regarding the development, prioritization and assessment of mitigation and remediation strategies to address sedimentation problems in Kenya’s water resources.

In present study, a detailed analysis on the rate of sedimentation of Katery lake (Tamil Nadu, India) was performed by using Differential Global Positioning System-based single-beam dual-frequency echo sounder bathymetry technique to find out the amount of sediment deposited over the years and reasons behind the water scarcity to local population. The collected bathymetry data during survey were processed with MATLAB and Surfer software for lake bed surface profile generation to find out the depth of water and deposited sediments, while the volume estimation was carried out by Extended Simpson 3/8 method. Sedimentation analysis was performed over the time interval of 10 years during 2003 and 2013. Herein, it was observed that rate of sedimentation was 3224.8 m3/year and the estimated quantity of deposited silt was 156,327 m3 which are 69% of total water storage capacity of the lake. Therefore, in order to curtail the after-effects of fast sedimentation, the rejuvenation program was executed in the years 2014–2015, to maintain long-term sustainability and performance of the lake. Sediment estimation was validated using numerical analysis and practical dredged volume, which helped in regaining 239% water storage capacity of lake. Thus, the lake rejuvenation program was successfully executed using bathymetry survey analysis for all three phases.

Reservoir sedimentation is a crucial challenge in planning and managing sustainable surface water resources in arid and semi-arid regions and must be assessed with accuracy. Both data-based models and conceptual models can be valuable tools for predicting reservoir sedimentation. In this study, we used an artificial neural network (ANN) approach and a modified Universal Soil Loss Equation coupled with multiple linear regression (MUSLE-MLR) model to predict yearly sedimentation in the Sidi Mohammed Ben Abdellah reservoir, located in a semi-arid region of Morocco. To construct the MUSLE-MLR model, we first calibrated and validated the MUSLE on 32 storms at four gauging stations upstream of the dam to estimate the sediment yield at these four gauging stations; we then developed the MLR model for combining sediment yield and reservoir sedimentation. The results of this model were then compared with the performance of the ANN model that was trained and validated over the periods 1975–2008 and 2009–2015, respectively. The comparison revealed that the calibrated MUSLE model is fairly useful to predict sediment yield at the watershed level. However, comparison of the two models during the validation process showed that the ANN (R2 0.91, Nash–Sutcliffe Efficiency [NSE] 0.820) is more accurate and more suitable than the MUSLE-MLR model (R2 0.819, NSE − 1.592) to predict reservoir sediment in the Sidi Mohammed Ben Abdellah reservoir. The findings of this study contribute to the armamentarium of potential tools that can be used to predict and manage reservoir sedimentation at the watershed and reservoir levels in a semi-arid context.

Reservoir is frequently vulnerable through damage of capacity owing towards sedimentation. Sedimentation is an inherent procedure in the reservoir. A continuous sediment deposition, which is being transported by the alluvial rivers in the reservoir cannot be fully eradicated rather it can be controlled. Nowadays, reservoir sedimentation is a burning problem, especially in India. For the sustainability of this massive structure (reservoirs) various measures are taken into account. If the sediment inflow is larger than that of the sediment outflow, the effective life of the reservoir is shortened. Turbidity currents generated in the reservoirs play a significant role in the reservoir sedimentation. The term turbidity current is a natural phenomenon which is frequently undecided besides the sediment support appliance (e.g. settling, turbulence, etc.) may be operated simultaneously within a sediment-gravity flow. The turbidity current is the utmost stereotypically a submerged current of typically quickly moving, downhill flow of water produced through the increased density for the high quantities of sediment. It is also responsible for disturbing the vast amounts of sediments in the deepwater. If the turbidity current increases in water, the aforementioned converts thicker besides a smaller amount of flawless for the higher concentration. Because of sedimentation, the yearly loss rate of the storage capacity of reservoir is estimated as 1–2% of the total storage capacity of the reservoir. This paper focuses on an extensive study of the literature and analysed and compared the results of the previous studies on turbidity current of the reservoir sedimentation. It is found that venting of the turbidity current that reaches in the dam is economical as well as beneficial as per the present scenario of the various reservoirs which are facing the sedimentation in it.

The Balog-Balog Reservoir was conceptualized in 1986 as a single, high dam that would supply irrigation water supply to the Balog-Balog River irrigation system of Tarlac. However, the proposal remained on the drawing board until an unsolicited proposal to construct a multiple dam system composed of nine reservoirs with small dams was submitted to the government in 2012. This chapter presents the Balog-Balog Reservoir study with single, high dam versus this multiple dam system. In the context of reservoir sedimentation, it is expected that the single, high dam would have a longer life compared to the low dams. The San Roque Reservoir study is also presented in this chapter to assess the reservoir life with reservoir sedimentation. This study was a requisite of a loan package agreement that after its completion in 2002, every 5 years a reservoir operations and sediment management study would be conducted. Finally, the sediment flushing operations study in Pulangi Reservoir is discussed in this chapter. Pulangi Reservoir is the only major reservoir in the Philippines with a sediment flushing facility but was never activated since its completion in 1985 until after the study on sediment flushing was conducted in 2005. For both San Roque and Pulangi Reservoir sedimentation management studies, a two-dimensional hydraulic model of flow and sediment transport was employed to conduct the study.

Reservoir sedimentation is the gradual accumulation of incoming sediments from upstream catchment leading to the reduction in useful storage capacity of the reservoir. Quantifying the reservoir sedimentation rate is essential for better water resources management. Conventional techniques such as hydrographic survey have limitations including time-consuming, cumbersome and costly. On the contrary, the availability of high resolution (both spatial and temporal) in public domain overcomes all these constraints. This study assessed Jayakwadi reservoir sedimentation using Landsat 8 OLI satellite data combined with ancillary data. Multi-date remotely sensed data were used to produce the water spread area of the reservoir, which was applied to compute the sedimentation rate. The revised live storage capacity of the reservoir between maximum and minimum levels observed under the period of analysis (2015–2017) was assessed utilizing the trapezoidal formula. The revised live storage capacity is assessed as 1942.258 against the designed capacity of 2170.935 Mm3 at full reservoir level. The total loss of reservoir capacity due to the sediment deposition during the period of 41 years (1975–2017) was estimated as 228.677 Mm3 (10.53%) which provided the average sedimentation rate of 5.58 Mm3 year1. As this technique also provides the capacity of the reservoir at the different elevation on the date of the satellite pass, the revised elevation–capacity curve was also developed. The sedimentation analysis usually provides the volume of sediment deposited and rate of the deposition. However, the interest of the reservoir authorities and water resources planner’s lies in sub-watershed-wise sediment yield, and the critical sub-watersheds upstream reservoir requires conservation, etc. Therefore, in the present study, Soil and Water Assessment Tool (SWAT) was used for the estimation of sediment yield of the reservoir. The average annual sediment yield obtained from the SWAT model using 36 years of data (1979–2014) was 13.144 Mm3 year−1 with the density of the soil (loamy and clay) of 1.44 ton m−3. The findings revealed that the rate of sedimentation obtained from the remote sensing-based methods is in agreement with the results of the hydrographic survey.

The present study attempts to predict the reservoir sedimentation in 32 km region of the Tenryu River between the Hiraoka and Sakuma Dams in Japan. For numerical simulations of the reservoir sedimentation, the one-dimensional model of the Hydrologic Engineering Centre-River Analysis System (HEC-RAS) is used together with the inclusion of channel geometry, bed gradation curve, Exner-5 bed sorting mechanisms, fall velocity of the particle, and flow and sediment boundary conditions pertaining to modeling region. The modeling region of the Tenryu River is divided into 48 river stations with 47 reaches in the numerical simulations. The numerical model is calibrated using the available data for 48 years from 1957 to 2004. The formulae of sediment transport function, Manning’s roughness coefficient, computational increment and fall velocity have been identified for getting the best estimation of the Sakuma Dam reservoir sedimentation. Combination of obtained sensitive parameters and erodible limits of 2 m gave the best comparison with the measured bed profile. The computed results follow the trend of measured data with a small underestimation. Although Manning’s roughness coefficient has an effect on the sedimentation, no direct relation is found between the Manning’s roughness coefficient and reservoir sedimentation. It is found that the temperature of water has no effect on the reservoir sedimentation.

Reservoir sedimentation usually occurs in rivers that carry heavy amounts of silt. Setting reasonable schedules for drainage hole operations can balance the reservoir sediment levels and downstream...

The sedimentation in reservoirs is mainly caused by sediment inflow from land erosion, riverbank erosion and volcanic eruption. The objectives of this research are to study reservoir sedimentation using the average end-area method for reservoir volume calculation, and to study sediment management in reservoirs and their catchments. This research was conducted in Wlingi and Lodoyo reservoirs, located near Mt. Kelud, one of the most active volcanoes in Indonesia. The assessment reveals that both reservoirs are severely affected by eruptions of Mt. Kelud. The total remaining capacity of Wlingi reservoir in 2015 was 2·20 million m3, which corresponds to 9·2% of the initial capacity. The total remaining capacity of Lodoyo reservoir in 2015 was 1·33 million m3, which corresponds to 25·8% of the initial capacity. Sediment management strategies of both reservoirs consist of methods to reduce sediment inflow from upstream, methods to minimise sediment trapping, and methods to recover the reservoirs’ storage.

The sedimentation is a pervasive complex hydrological process subjected to each and every reservoir in world at different extent. Hydrographic surveys are considered as most accurate method to determine the total volume occupied by sediment and its distribution pattern in a reservoir. But, these surveys are very cumbersome, time consuming and expensive. This complex sedimentation process can also be simulated through the well calibrated numerical models. However, these models generally are data extensive and require large computational time. Generally, the availability of such data is very scarce. Due to large constraints of these methods and models, in the present study, data driven approaches such as artificial neural networks (ANN), model trees (MT) and genetic programming (GP) have been investigated for the estimation of volume of sediment deposition incorporating the parameters influenced it along with conventional multiple linear regression data driven model. The aforementioned data driven models for the estimation of reservoir sediment deposition were initially developed and applied on Gobindsagar Reservoir. In order to generalise the developed methodology, the developed data driven models were also validated for unseen data of Pong Reservoir. The study depicted that the highly nonlinear models ANN and GP captured the trend of sediment deposition better than piecewise linear MT model, even for smaller length datasets. (C) 2013 Elsevier B. V. All rights reserved.

Reservoir sedimentation reduces the benefits from the storage of fresh water. The volume and distribution of sediment deposition must be predicted for a long term reservoir operation plan. Either or both experimental and numerical modeling can be applicable for an evaluation of reservoir sedimentation. Because sedimentation occurs along entire reservoirs and throughout the reservoir life span, a one-dimensional numerical sediment transport model, GSTARS, was considered in this study. Even though the model is not a truly two or three dimensional one, the model has capability of simulating channel geometric change in a semi-two dimensional manner using the stream tube concept. In this study, the effect of the number of stream tubes on the performance of the numerical simulation was analyzed using 14 years of real reservoir sedimentation data, and reasonable results were produced with three stream tubes. The densities of the deposited sediment depend on the reservoir operation scheme, especially for clay and silt. It was found that the predicted results vary with the density, and the prediction with various density with respect to location is required for a study reach where reservoir and river regions exit together.

Extreme events, such as large storms and floods, have a major effect on the transport of sediment and contaminants and, hence, on water quality. To be realistic, models designed to predict the short-term transport and fate of sediment and contaminants must include large floods and storms, an idea not incorporated into existing models based on uniform sediment flux. Sediment transport in and to river channels in mountainous terrain is strongly influenced by precipitation, particularly when heavy precipitation triggers a surface landslide in the catchment area. This study provides a quantitative measure of such sediment transport. The Yahagi Dam watershed was modeled using a 50-m grid-based digital elevation model (DEM), and flow directions were determined for each of the slopes present. The study objective was to develop a general algorithm for simulating water flow and sediment movement in a dammed mountain basin using water and sediment dynamics modeling. The nonuniform flow model used for stream channels can incorporate energy loss around dam reservoirs, and the resulting algorithm can estimate all phenomena related to sediment movement. The new method was verified by applying it to the Tokai rainfall disaster and the Yahagi Dam basin, Japan. In this basin, the volume of bedload sediment deposited is 993 × 103 m3/y, suspended-load sediment is 669 × 103 m3/y, and wash load sediment is 900 × 103 m3/y, as determined from sediment production in each tributary of the Yahagi River. Most sediment is probably introduced during extreme flood events owing to lithological factors, and thus extreme rain events that now accompany climate change are very important in sediment supply. During extreme flood events, the river's effective tractive force (τ*e, d90) exceeds the critical tractive force (τ*c), especially upstream of the Yahagi Dam. Rainfall-related sediment disasters can be accurately predicted using water- and sediment-dynamics models that are founded on realistic geomorphological characteristics and sediment flux of rivers.

Mrica Reservoir is one of many reservoirs located in Central Java that experienced a considerably high sedimentation during the last ten years. This condition has caused a rapid decrease in reservoir capacity. Various countermeasures have been introduced to reduce the rate of the reservoir sedimentation through catchment management and reservoir operation by means of flushing and/or dredging. However, the sedimentation remains intensive so that the fulfillment of water demand for electrical power generation was seriously affected. This paper presents the results of evaluation on the dynamics of the purpose of this research is to evaluate the sediment balance of the Mrica Reservoir based on two different scenarios, i.e. the existing condition and another certain type of reservoir management. The study on sediment balance was carried out by estimating the sediment inflow applying sheet erosion method in combination with the analysis of sediment rating curve. The measurement of the deposited sediment rate in the reservoir was conducted through the periodic echo sounding, whereas identification of the number of sediment that has been released from the reservoir was carried out through the observation on both flushing and dredging activities. The results show that during the last decade, the rate of the sediment inflow was approximately 5.869 MCM/year, whereas the released sediment from the reservoir was 4.097 MCM/year. In order to maintain the reservoir capacity, therefore, at least 1.772 MCM/year should be released from the reservoir by means of either flushing or dredging. Sedimentation management may prolong the reservoir’s service life to exceed the design life. Without sediment management, the lifetime of the reservoir would have finished by 2016, whereas with the proper management the lifetime may be extended to 2025.

This paper presents the development of a turbid density current module (TDCM) for a one-dimensional quasi-steady reservoir sedimentation model suitable for long-term simulations and an example of its application. The module determines the plunging point of a density current based on the criterion of the densimetric Froude number. Following plunging, simulation continues in a supercritical regime as long as the energy of density flow and bed slope are sufficient to support transport in this mode, or until the dam is reached. A muddy pond is then formed. An adapted version of the theory of Toniolo et al. (2007) is used to compute water and sediment balance in a muddy pond. If the level of muddy pond exceeds the lowest level outlet, sediment is vented from the reservoir. The model was applied to one of the largest reservoirs in the world, the Nurek reservoir in Tajikistan. Historical data on bed levels and sediment inflow as well as a recent survey from 2015 were used to calibrate and validate the model. The model showed good results both in terms of modelled bed levels and composition of deposited sediment. For comparison purpose, the model was also calibrated without the TDCM module. However, the discrepancy between the observed and modelled data was significantly higher, confirming that the good match in the case of the TDCM module was not achieved solely by calibration, but rather by a more appropriate approach to modelling. These results support the choice of using the model with TDCM for modelling a general pattern of long-term deposition in the Nurek reservoir, in which turbid density currents play an important role.

The future reliance on water supply and flood control reservoirs across the globe will continue to expand, especially under a variable climate. As the inventory of new potential dam sites is shrinking, construction of additional reservoirs is less likely compared to simultaneous flow and sediment management in existing reservoirs. One aspect of this sediment management is related to the control of upstream sediment sources. However, key research questions remain regarding upstream sediment loading rates. Highlighted in this article are research needs relative to measuring and predicting sediment transport rates and loading due to streambank and gully erosion within a watershed. For example, additional instream sediment transport and reservoir sedimentation rate measurements are needed across a range of watershed conditions, reservoir sizes, and geographical locations. More research is needed to understand the intricate linkage between upland practices and instream response. A need still exists to clarify the benefit of restoration or stabilization of a small reach within a channel system or maturing gully on total watershed sediment load. We need to better understand the intricate interactions between hydrological and erosion processes to improve prediction, location, and timing of streambank erosion and failure and gully formation. Also, improved process-based measurement and prediction techniques are needed that balance data requirements regarding cohesive soil erodibility and stability as compared to simpler topographic indices for gullies or stream classification systems. Such techniques will allow the research community to address the benefit of various conservation and/or stabilization practices at targeted locations within watersheds.

This study describes the assessment of reservoir sedimentation of the Patratu Reservoir using Satellite Remote Sensing (SRS). The sedimentation assessment was carried out using satellite data and reservoir water level data from 2006 to 2012. Water spread area was analysed from satellite data. The Normalized Difference Water Index (NDWI) has been used to delineate open water features and to enhance the presence of water surface in satellite imagery of the Patratu Reservoir. Water spread area of the reservoir at a particular elevation on the date of the passing of the satellite was used to develop an elevation-area curve. For the present case, fluctuation of water level was found to vary from 387.096 to 406.152 m. The linear interpolation/extrapolation technique has been employed to assess the water spread area of Patratu Reservoir at different elevations. Further, these areas were used to compute the live storage capacity of the reservoir between two elevations by the Prismoidal formula. From the s...

Trap efficiency method of estimating reservoir sedimentation found by Brune (1953) has been widely used all over the world. This method developed the curve with the relation between trap efficiency and reservoir capacity-inflow (C/I) ratio. Many researchers used this method and developed Brune‘s methods to predict the amount of sediment trapped in reservoirs, because these methods are more versatile, accurate and quantifiable with a simple knowledge. Even though these are more accurate methods, they have constraints to use these method especially in most developing countries which do not have inflow measuring stations at upstream of reservoirs because of high cost for installing inflow measuring gauges at upstream part of every reservoir. Assuming inflow equalled to outflow for calculating capacity-inflow (C/I) ratio without taking regression analysis of their relation gave high values of C/I ratio because of evaporation and seepage losses which makes the difference. Sampling sediment inflow to the reservoir every time is also costly and time consuming for estimating sediments trapped in reservoirs by using trap efficiency verses reservoir capacity–inflow (C/I) ratio curve. Therefore, modifying these methods with easily available and reliable data makes estimation of sediments in reservoir easier and more accurate. The main objective of this review is to identify the mechanism how to modify Brune and developed Brune‘s curve for estimating reservoir sedimentation using trap efficiency verses reservoir capacity–outflow (C/Q) ratio curve. To do this 44 reservoirs which have inflow gauging stations at upstream of the reservoir and outflow gauging stations at downstream of reservoir have been selected and related the inflow (I) with outflow (Q). Finally, the relationship between inflow and outflow by regression analysis method has been developed, and then Q substituted in terms of I after regression analysis was derived.

Reservoir sedimentation is a serious problem that normally reduces the capacity of a dam (reservoir) for water storage over a given period of time. This can lead to insufficient availability of water for domestic uses, irrigation and hydropower. This study was conducted to determine the rate of sedimentation, sediment yield and the capacity of the University of Ilorin dam (Ilorin, Nigeria) between June 2007 and June 2014. Geographic Information System (GIS), Global Positioning System (GPS), canoe and lead-line techniques were used for the measurement of depth of the reservoir of the dam. Soil and Water Assessment Tool (SWAT) model was used to simulate the sediment yield. The initial capacity of the dam after construction in 2007 was 1.800 x 106 m3 but this capacity was reduced to 1.411 x 106 m3 in 2014 due to sedimentation. The sediment was found to be clay soil which covered 389,170 m3 of the reservoir and the mean bulk density of the clay soil sediment was 1139 kg/m3. The mean values of clay, silt and sand contents of the sediment yield were 46.5, 35.6 and 17.9 %, respectively. The annual sediment yield was high in the reservoir due to farming activities at the upstream end of the dam, annual rate of sedimentation was 12.78 m3/ha/yr and sediment yield was 14,557.14 kg/ha/yr. Farming activities should be prevented at the upstream of the dam and dredging should be done every 10 years when 30.87% of the storage capacity would be occupied by sediment.

The Conowingo Reservoir is situated on the Susquehanna River, immediately upstream of Chesapeake Bay, the largest estuary in the United States. Sedimentation in the reservoir provides an unintended benefit to the bay by preventing sediments, organic matter, and nutrients from entering the bay. The sediment storage capacity of the reservoir is nearly exhausted, however, and the resulting increase in loading of sediments and associated materials is a potential threat to Chesapeake Bay water quality. In response to this threat, the Lower Susquehanna River Watershed Assessment was conducted. The assessment indicates the reservoir is in a state of "dynamic equilibrium" in which sediment loads from the upstream watershed to the reservoir are balanced by sediments leaving the reservoir. Increased sediment loads are not a threat to bay water quality. Increased loads of associated organic matter and nutrients are, however, detrimental. Bottom-water dissolved oxygen declines of 0.1 to 0.2 g m are projected as a result of organic matter oxidation and enhanced eutrophication. The decline is small relative to normal variations but results in violations of standards enforced in a recently enacted total maximum daily load. Enhanced reductions in nutrient loads from the watershed are recommended to offset the decline in water quality caused by diminished retention in the reservoir. The assessment exposed several knowledge gaps that require additional investigation, including the potential for increased loading at flows below the threshold for reservoir scour and the nature and reactivity of organic matter and nutrients scoured from the reservoir bottom.

Reduction of suspended sediment (SS), total phosphorus (TP), and total nitrogen is an important focus for Chesapeake Bay watershed management. The Susquehanna River, the bay's largest tributary, has drawn attention because SS loads from behind Conowingo Dam (near the river's mouth) have been rising dramatically. To better understand these changes, we evaluated histories of concentration and loading (1986-2013) using data from sites above and below Conowingo Reservoir. First, observed concentration-discharge relationships show that SS and TP concentrations at the reservoir inlet have declined under most discharges in recent decades, but without corresponding declines at the outlet, implying recently diminished reservoir trapping. Second, best estimates of mass balance suggest decreasing net deposition of SS and TP in recent decades over a wide range of discharges, with cumulative mass generally dominated by the 75∼99.5th percentile of daily Conowingo discharges. Finally, stationary models that better accommodate effects of riverflow variability also support the conclusion of diminished trapping of SS and TP under a range of discharges that includes those well below the literature-reported scour threshold. Overall, these findings suggest that decreased net deposition of SS and TP has occurred at subscour levels of discharge, which has significant implications for the Chesapeake Bay ecosystem.

Sedimentation is a serious problem in the operations of reservoirs. In Taiwan, the situation became worse after the Chi-Chi Earthquake recorded on 21 September 1999. The sediment trap efficiency in several regional reservoirs has been sharply increased, adversely affecting the operations on water supplies. According to the field record, the average annual sediment deposition observed in several regional reservoirs in Taiwan has been increased. For instance, the typhoon event recorded in 2008 at the Wushe Reservoir, Taiwan, produced a 3 m sediment deposit upstream of the dam. The remaining storage capacity in the Wushe Reservoir was reduced to 35.9% or a volume of 53.79 million m3 for flood water detention in 2010. It is urgent that research should be conducted to understand the sediment movement in the Wushe Reservoir. In this study, a scale physical model was built to reproduce the flood flow through the reservoir, investigate the long-term depositional pattern, and evaluate sediment trap efficiency. This allows us to estimate the residual life of the reservoir by proposing a modification of Brune’s method. It can be presented to predict the lifespan of Taiwan reservoirs due to higher applicability in both the physical model and the observed data.

This work analyzes the loss of storage, in a medium-term basis, of Beninar reservoir (Almería, Spain) built in a semiarid watershed and its consequences downstream. The reservoir, in the Adra river basin (Southern Spain), was designed to supply water for the irrigation of more than 28.000 hectares of greenhouses. Its storage volume, that was initially of 68 hm3 in 1984, has been reduced approximately to half. The total sediment volume arrived to the reservoir during the last 32 years is 6,8 hm3, of which 1,68 hm3 are estimated to come from fluvial contributions. The results remark the torrential nature of rainfall events for generating large sediment contributions and highlights the importance of taking into account these types of events. The total loss of storage is especially relevant from two points of view 1) reduction of flood abatement due to sedimentation and structural problems of dam, which has left only 2 hm3 of regulation capacity and 2) loss of water volume which is essential to improve the water quality of the overexploited and salinized aquifers which supply the greenhouses downstream. Beninar reservoir is a key infrastructure to preserve a competitive price of water for greenhouse cultivation.

Prediction of sediment distribution in reservoirs is an important issue for dam designers to determine the reservoir active storage capacity. Methods proposed to calculate sediment distribution are varied, and mainly empirical. Among all the methods currently available, only area-reduction and area-increment methods are considered as the principal methods for prediction of sediment distribution. In this paper, data of 16 reservoirs in the United States are used to propose a new empirical method for prediction of sediment distribution in reservoirs. In the proposed method, reservoir sediment distribution is related to sediment volume and original reservoir characteristics. To validate the accuracy of the new proposed method, obtained results are compared with survey data for two reservoirs. The results of this investigation showed that the proposed method has an acceptable accuracy.

A model to compute reservoir sedimentation rates at daily timescales is presented. The model uses streamflow and sediment load data from nearby stream gauges to obtain an initial estimate o...

Riverine ecosystem protection requires the maintenance of natural flow and sediment regimes downstream from dams. In reservoir management schedules this requirement should be integrated with sedimentation control and human water supply. However, traditional eco-friendly reservoir operating methods have usually only considered the natural flow regime. This paper seeks to develop a reservoir operating method that accounts for both the natural flow and sediment regimes as well as optimizing the water supply allocations. Herein, reservoir water level (RWL), sediment-occupied ratio of reservoir volume (SOR) and rate of change of SOR (RCSOR) are adopted as three triggers of a drawdown-flushing-based sediment management policy. Two different groups of reservoir operating rule curves (RORCs) are designed for sediment-flushing and non-sediment-flushing years, and the three triggers, RWL, SOR and RCSOR, are used to change the “static” RORCs to “dynamic” ones. The approach is applied to the Wangkuai Reservoir, China to test its effectiveness. This shows that the approach can improve the flexibility of reservoir operators to balance the reservoir management, water supply management and the flow and sediment needs of the downstream riverine ecosystem.

Reservoir sediment problem on sediment-laden river is the main puzzle problem in reservoir operation. Reservoir sedimentation, reservoir operation, reservoir sediment treatment and utilization and simulation of reservoir are analyzed in the paper. Difficulty is also provided during the research process. And reservoir sediment research on Yellow River is prospected. The paper can be helpful to provide the basis for reservoir sediment problem on sediment-laden river, and also point out the direction of reservoir sediment research on Yellow River.

A measurement campaign was carried out in the Upper Tana basin (Kenya) to quantify soil erosion and reservoir sedimentation rates, including a bathymetric reservoir survey and sediment load sampling during one year. Then, distributed soil erosion modelling was performed to study sediment budgets throughout the basin and to evaluate the potential of upstream erosion control through vegetated contour strips and check dams. Finally, the areas where these measures would be most effective were identified and local stakeholder associations to implement them were prioritized. The influence of the scale of implementation was evaluated by using the model to consider three adoption scenarios. This study illustrates the relevance of distributed erosion models to target erosion control measures when sufficient information on the eroding areas is available from field surveys. Bathymetric surveys were fundamental to validate the long-term model response, while point measurements were valuable to verify the spa...

Nestos is one of the most important transboundary rivers flowing through Bulgaria and Greece. In the Greek part of the river, two reservoirs, the Thisavros Reservoir and the Platanovrysi Reservoir, have already been constructed and started operating in 1997 and 1999, respectively. In the first part of the chapter, the reservoir sedimentation effect on the coastal erosion is investigated, for the case of the Nestos River delta and the adjacent shorelines, through a combination of mathematical modeling, modern remote sensing techniques, and field surveying, while in the second part, the mechanical removal as well as the flushing of sediment from the reservoir of Platanovrysi and its disposal in the subbasin downstream of the Platanovrysi Dam up to the Nestos River delta are investigated as potential treatment methods of reducing coastal erosion, using a modification of the same mathematical model that is utilized in the first part of the chapter. The overall findings and conclusions arising from the work presented and discussed in the present chapter contribute to the overall need to thoroughly understand the direct effect of dam construction on coastal erosion, as well as to examine the effectiveness of potential sediment management treatments.

The bed change model of HEC-RAS was used to predict the formation of a delta upon an influx of high-density sediment while taking the particle-size distributions of the suspended sediment and bed materials into account. The model was able to reasonably predict both the spatial-temporal distribution of the delta and the amount of deposited sediment according to the grain size. In addition, it was able to estimate the main type of grains that sediment at particular locations at particular times moderately well. It is expected that the simulation and the analysis considering these particle-size distributions of sediment will provide important information on planning and maintenance of the water resource related facilities.

Study of soil erosion in the reservoir watershed, the main source of reservoir sedimentation that affects the reservoir's lifespan and capacity, is of vital importance for watershed management. Due mainly to the lack of data, empirical formulas are commonly used to estimate reservoir sedimentation. However, these estimations are far from accurate. Field measurements data of discharge and suspended sediment were collected during three typhoon events in Shihmen Reservoir watershed, Taiwan. Temporal variations of water surface elevation, discharge, and concentration of suspended sediment were measured. A numerical model, Hydrological Simulation Program Fortran HSPF, developed by the USEPA was adopted to simulate the sediment yield. However, as calibration and verification data are not always available and the parameter-calibration process is complicated and tedious for novice users of the model, an artificial neural network ANN model was proposed. Significant amount of the synthetic data from the calibrated HSPF model were first generated to train the ANN model, which in turn was used to estimate the sediment yield. Comparisons of the sediment yield using both the HSPF and ANN model give correlation coefficients of 0.96 for training and 0.93 for validation. Without the complicated parameter calibration process, the ANN model was faster and easier to use than the HSPF model.

The Xiaolangdi Hydro-Project is one of the large projects on the main stem of the Middle Yellow River. It has been operated for more than 10 years, since its impoundment in October, 1999. The reservoir has trapped 2.833×109 m3 of sediment, and caused the total erosion of 1.891×109 t in the Lower Yellow River from October, 1999 through October, 2010. Not only the serious atrophied situation of the Lower Yellow River (LYR) has been resuscitating, but also many new phenomena of sediment transport and behaviors of channel re-establishing are coming into being. They are illustrated and discussed in detail in this paper.

Sediment deposition in reservoirs has caused the loss of 66% of the reservoir capacity in China. The main sedimentation control strategies are: 1) storing the clear water and releasing the turbid water; 2) releasing turbidity currents; 3) Draw-down flushing and empty flushing; and 4) dredging. The paper summarizes these strategies with examples. Sediment transport in many Chinese rivers occurs mostly during the 2–4 month flood season, that is, 80–90% of the annual sediment load is transported with 50–60% of the annual runoff. By storing the clear water after the flood season and releasing the turbid water during the flood season, less sediment deposits in the reservoir while the reservoir is still able to store enough water for power generation in the low flow season. The Three Gorges and Sanmenxia reservoirs apply this strategy and control sedimentation effectively. Turbidity currents have become the main sedimentation control strategy for the Xiaolangdi Reservoir. Empty flushing involves reservoir draw-down to temporarily establish riverine flow along the impound reach, flushing the eroded sediment through the outlets. Case studies with the Hengshan Reservoir and Zhuwo Reservoir are presented. Jet dredgers have been used to agitate the reservoir deposit so that the deposit is released from the reservoir with currents. The sediment releasing efficiency is 30–100% for storing the clear and releasing the turbid; 6–40 % for turbidity current; and 2,400–5,500% for empty flushing. Empty flushing causes high ecological stress on the ecosystem to the downstream reaches. Storing the clear and releasing the turbid is the best strategy to control reservoir sedimentation while achieving hydro-power benefit and maintain ecological stability.