Reservoir Sedimentation

Many techniques are available to actively manage reservoir sedimentation, and an equally important suite of adaptive strategies are available for managing the impacts of sedimentation without manipulating the sediment. Successful reservoir management to combat the effects of sedimentation may employ a combination of active plus adaptive strategies. This paper describes both active and adaptive strategies to manage reservoir sedimentation, and may be useful as a checklist of options to consider in addressing a sedimentation problem. Widespread application of both active and adaptive strategies will be required to successfully address the growing sedimentation problem worldwide.

Pengelolaan sedimentasi di waduk akhir-akhir telah menggunakan beberapa pendekatan baru (Morris, 2003) di luar usaha penanganan sedimen yang lazim seperti pengerukan. Pendekatan itu antara lain berupa penggelontoran (flushing) melalui sarana pelepasan air waduk (water outlet). Selain itu, ada usaha menerapkan keseimbangan sedimen dengan mengendalikan daur sedimentasi (sedimentation cycle) mulai dari pengendalian erosi di pegunungan hingga berakhir dengan penataan keseimbangan angkutan di sungai. Dikembangkan pula alternatif lain, dengan membangun saluran pintas (bypass) untuk menghindarkan waduk dari pengendapan sedimen. Bagaimana pun juga, pengelolaan waduk dengan menggunakan pendekatan di atas terbatas penerapannya dan dapat digunakan beberapa waduk di dunia. Demikian pula di Pulau Jawa. Tak kalah pentingnya adalah keterkaitan dari penanganan sedimen dengan aspek lain, seperti peran serta masyarakat, pembiayaan dan penyiapan perangkat kelembagaan dan peraturan- perundangan yang mendukung.

En este trabajo se presenta el análisis de los procesos de sedimentación en un embalse situado en una cuenca afectada por un régimen hidrológico tropical, en la que la ocurrencia de eventos hidrológicos extremos, fundamentalmente huracanes, produce efectos de gran magnitud en lo que respecta a la producción de sedimentos y en consecuencia su incidencia en la sedimentación en embalses resulta significativa. El embalse de Valdesia, situado en la cuenca del Río Nizao en la República Dominicana, ilustra esta situación de manera dramática. El análisis de la problemática se vé fuertemente influenciado por la falta de información detallada relativa a la producción de sedimentos, ya que con los datos de batimetrías es posible calibrar modelos de producción de sedimentos, y también resulta aconsejable recurrir a la aplicación de técnicas sencillas para la predicción del comportamiento de embalses en esas circunstancias.

Reservoir silting is one of the principal problems affecting the performance of dams in Algeria from the standpoint of reservoir capacity for storage. Foum El Kherza Reservoir (also known as Foum El Gherza), near Biskra Town, Algeria, is subject to dredging operations with the intent of recovering 70% of its initial storage capacity of 47 hm3 (million cubic metres). The forecasting of sediment volume trapped in the reservoir is essential to plan the future use of this resource and to sustain irrigation for the palm groves characteristic of the region. However, there are currently no sediment data, nor a sediment rating curve, for predicting sediment inflow based on hydrological data. This paper describes the optimization of a cumulative trapped sediment curve for Foum El Kherza Reservoir based on 44 years of daily inflows, by using a spreadsheet optimization tool, Microsoft Excel® Solver to calibrate the cumulative sediment load against the cumulative sediment inflow as documented by eight bathymetric surveys since the dam construction. Editor D. Koutsoyiannis; Associate editor A. Montanari Citation Tebbi, F.Z., Dridi, H., and Morris, G.L., 2012. Optimization of cumulative trapped sediment curve for an arid zone reservoir: Foum El Kherza (Biskra, Algeria). Hydrological Sciences Journal, 57 (7), 1368–1377.La sédimentation dans les réservoirs est l'un des principaux problèmes qui affectent la performance des barrages en Algérie, du point de vue de la sécurité des structures, de la capacité des retenues pour le stockage ainsi que de la qualité des eaux. Le réservoir de Foum El Kherza (aussi connu sous le nom d'El Gherza) à Biskra en Algérie, est l'objet d'une opération de dévasement visant à récupérer 70% de sa capacité initiale de 47 hm3. La nécessité de prévoir le volume des sédiments retenus dans le réservoir est essentielle pour planifier l'utilisation future de cette ressource et maintenir l'irrigation des palmeraies de la région. Il n'existe cependant pas actuellement de données sur les sédiments, ni de courbe de tarage des sédiments, pour prévoir les apports solides à partir des données hydrologiques. Le présent article décrit l'optimisation d'une courbe cumulative de sédiments piégés pour le réservoir de Foum El Kherza basée sur 44 années d'apports journaliers et sur le calage du cumul de l'apport solide tenant compte de huit levés bathymétriques réalisés depuis sa construction.

As international attention continues to focus on large dam projects across Asia, it is worth noting that conflicts over the politics of and environmental changes caused by dams in India are not new. Population dislocation, siltation, disease, floods caused by catastrophic dam failure, raised water tables, high costs and low returns-all of these concerns, and others, can be discussed in the context of reservoir projects ten, one hundred, or even one thousand years old. In this paper, I identify some of the major issues in the political ecology of contemporary dam projects and show how these same issues have played out in southern India over the last thousand years, suggesting that historical attention to the cultural and political context of reservoir construction might help us to understand some aspects of contemporary conflicts.

Reservoirs were mainly designed and constructed in the upstream of each watershed to change the hydrologic characteristics of the basin and decrease the maximum flood discharge. Brantas is an important river basin in the Island of Java, Indonesia, that has used this approach in its water resources management. However, the issues of flood risk and flood recovery have moved up the po- litical and scientific agendas in recent years following increased frequency and severity in flood incidents and the increased likelihood that this trend will contin- ue as a consequence of climate change (Pryce, Chen and Mackay, 2009). Due to the global climate change, hydrological adversities are drivers to further risk in managing these reservoirs (Arnell, 2004). Four reservoirs were considered in this paper, namely Karangkates, Selore- jo, Bening and Wonorejo. Based on historical floods, a flood-routing routine was conducted for all four reservoirs. This paper assesses the probability of the flood to exceed the reservoir’s capacity. Using the definition of Wang et al (2005) it will discuss the occurrence probability that the system external load is greater than its carrying capacity. It was proven that risk increases along the decrease of the reservoir’s capacity due to sedimentation; the risk also ameliorate whenever the calculated flood designs are used in the routing process. New flood risk strategies are required, based on extending floodplains and designating certain downstream areas as flood prone areas upon dam breaks, implementation of new critical water levels in the reservoir impounding, and construction of increasing the crest height to maintain the flood control volume within the reservoir.

Many techniques are available to actively manage reservoir sedimentation, and an equally important suite of adaptive strategies are available for managing the impacts of sedimentation without manipulating the sediment. Successful reservoir management to combat the effects of sedimentation may employ a combination of active plus adaptive strategies. This paper describes both active and adaptive strategies to manage reservoir sedimentation, and may be useful as a checklist of options to consider in addressing a sedimentation problem. Widespread application of both active and adaptive strategies will be required to successfully address the growing sedimentation problem worldwide.

Sediment deposition in a reservoir decreases storage capacity and effects many other parameters of the reservoir adversely. It reduces benefits and useful life of a hydro power project that have huge socioeconomic impacts. Flushing is one of the techniques to remove sediments from reservoirs. This study investigates sediment accumulation, transportation and flushing using both the physical and numerical modeling. Gulpur Hydro Power Project (HPP) on Poonch River in Pakistan was chosen for this purpose. The geometry, cross-sections and other physical attributes of the Poonch River were prepared and hydraulic structures were placed on the basis of topographic survey using AutoCAD. Physical model of scale 1:40 was developed at Nandipur Research Station in Pakistan. After base test the model was used to get data for various scenarios of sediment flows. HEC-RAS was used for numerical simulations. Delta profile and flushing were simulated. Delta modeling was made for hourly time step for 20 years of sediment deposition with average discharge conditions, whereas, suitable flushing durations were predicted for various flushing discharges to de-silt yearly deposited sediments. Simulation showed that life of the un-sluiced Gulpur HPP is about 14-15 years. To enhance the life of project, annually 4-5 days are required for flushing with 250 m 3 /s discharge.

This article presents investigation of the inflow of sediments depending upon the stream flow, density and kinematic viscosity of water. The process involves Multiple Linear Regression (MLR) technique for estimation of sediment load and volume, by using UNISTAT software (Version 5.6). A general equation is developed for a specific flow rate while considering density and kinematic viscosity of water as other parameters. The developed equation can be applied in future for determining the sediment concentration when the flow rate is known. The daily stream flow and suspended sediment data belonging to the station Nausehri operated by the Water and Power Development Authority, Pakistan is used as case study. The results indicate that the dam site experiences a mean annual sediment load of 3.74 mst. With this much incoming sediment load the reservoir life comes out to be 45 years when no flushing is done. The impacts of this sediment deposition on the reservoir life and hydro-electric energy generation are also determined, which show a decrease of 113MW (12%) in the production capacity of the power plant and an adverse effect on the reservoir life.

Over the last fifty years human interference in the natural ecosystem of upper Damodar River Basin reduces the forest cover. These phenomena intensify the soil erosion of the Basin and subsequently increase the sedimentation rate of the Panchet reservoir. The sediments are trapped within the reservoir and the water holding capacity of the reservoir is decreased gradually. Hence the useful life of a reservoir gets reduced due to sediment deposition and it is considered as an emerging problem in the developing countries, like India. The present investigation aims to estimate the sedimentation of Panchet Reservoir which is situated on Damodar River. The study includes the temporal scale of thirty five years from 1971 to 2006. Using different quantitative hydro-geomorphic techniques, indices of image analysis and GIS, we have tried to assess the rate of reservoir sedimentation and its areal expansion.

Sustainable reservoir management seeks to retard sedimentation and reduce its adverse impacts, ultimately achieving an equilibrium between sediment inflow and outflow while sustaining storage capacity to maximize project benefits. Sedimentation data has traditionally been collected with the objective of simply documenting the timewise decline in reservoir capacity and computation of reservoir " useful life. " However, if the decision is made to manage the reservoir in a sustainable manner the available data needs to be analyzed differently, and additional data will be required to better understand sedimentation processes and develop management alternatives. This paper outlines some of the shortcomings of existing datasets and identifies data interpretation strategies and additional data types that can support sustainable reservoir management.

Sediment particles originating from erosion processes in the catchment are propagated along with the river flow. When the flow of a river is stored in a reservoir, the sediment settles in the reservoir and reduces its capacity. Reduction in the storage capacity of a reservoir beyond a limit hampers the purpose for which it was designed. Thus assessment of sediment deposition becomes very important for the management and operation of such reservoirs. Some conventional methods, such as hydrographie survey and inflow-outflow approaches, are used for estimation of sediment deposition in a reservoir, but these methods are cumbersome, time consuming and expensive. There is a need for developing simple methods, which require less time and are cost effective. In this study, a remote-sensing approach has been attempted for assessment of sedimentation in Bhakra Reservoir, located on the Satluj River in the foothills of the Himalayas. Multi date remote sensing data (1RS-1B, L1SS II) provided the information on the water-spread area of the reservoir, which was used for computing the sedimentation rate. The revised capacity of the reservoir between maximum and minimum levels was computed using the trapezoidal formula. The loss in reservoir capacity due to deposition of sediments for a period of 32 years was determined to be 807.35 Mm', which gives an average sedimentation rate of 25.23 Mm' year" 1 . The average rat£ of sedimentation using hydrographie survey data for the same period was 20.84 Mm' year" 1 . A comparison of the results shows that the rate of sedimentation assessed using the remote sensing based approach was close to the results obtained from the hydrographie survey.

Flow field in shallow waters, which is characterized by its complex mixing process and inherent dynamic nature, is interesting mainly due to its practical importance (e. g. in free flushing operation and sedimentation in large reservoirs). 3D numerical models make it possible to track two-dimensional large turbulence coherent structures, which are the dominant phenomenon in shallow reservoirs flow field. In the present study a fully three-dimensional numerical model SSIIM that employs the Finite Volume Approach (FVM) was utilized to reproduce the 3D flow field. Various shallow reservoir geometries with fixed and deformed equilibrium bed were considered. The measurements by Large-Scale Particle Image Velocimetry techniques (LSPIV) and Ultrasonic Doppler Velocity Profiler (UVP) over the flow depth were used for model validation. Outcomes revealed reasonable agreement between the simulated and measured flow velocity field even when an asymmetric flow pattern exists in the reservoir.

Flushing of fine sediments from reservoirs is one of the most effective techniques to reduce reservoir sedimentation, but the sudden release of high suspended sediment concentration can have adverse effects on the receiving water body. Field observations of sediment flushing operations have shown that the released volume of water and sediments propagate downstream through different types of waves. In particular the hydrodynamic signal travels faster than the sediment signal resulting in the splitting of the two waves. Since the sediment wave lags behind, deposition is enhanced in the tail of the hydrodynamic wave, where velocity decreases and cannot sustain the sediment in suspension: the separation phase of the two waves controls the deposition process of the released suspended sediments. The separation and the interaction between the two waves, especially in the transport of suspended sediments, is controlled by the sediment wave celerity. Neverthless in many sediment transport models the sediment wave celerity is assumed to be the mean flow velocity. We developed a simplified one-dimenional numerical model to study the interaction between the two waves. In the model we introduced a celerity factor that corrects the depth-averaged sediment transport velocity as a function of the shape of the vertical velocity profile and suspended sediment concentration. We observed that the use of the celerity factor in one-dimensional sediment concentration transport enhances the deposition because of the reduced celerity of the sediment wave, which separates sooner from the hydrodynamic wave.

Dam construction is one of the methods for storing surface water. Estimating the service life and economic efficiency of dam is one of the most important cases in estimating the design of it. The most important problem that threatens the useful life of the dam is input sediment to reservoir. Life expectancy of a dam reservoir is measured with respect to the incoming sediments. Estimation of suspended sediment in rivers plays an important role in estimating the useful life of dams. Many methods such as statistical methods USBR (United States Bureau of Reclamation) and FAO (Food and Agriculture Organization) and moderate categories method are used to measure suspended. In this research the mentioned statistical and some other methods are used in Mahabad dam. By using sediment volume and the estimated flow rate Sediment loads is measured at different times in this method and its accuracy is estimated by correlation coefficient. The gained results show that the sedimentation estimates by using USBR and FAO with two correlation curves methods are useful and have more correlation coefficient.

Mosul Dam, located on the Tigris River north of Iraq, is experiencing sedimentation problems, especially near the Al-Jazeera pumping station that supplies the irrigation water for the Al-Jazeera project. The sources of the sediment accumulated within the reservoir are from the Tigris River, as well as ten side valleys on both sides of the reservoir. The sediment inflow rate into the reservoir and the released values are considered on the basis of the operation schedule of the dam for the considered period from 1986 to 2011. The sediment loads were estimated on the basis of available measurements and estimated literature values. The HEC-RAS 4.1 model was used for flows and sediments in the main river and reservoir. The model was calibrated for flow simulations (coefficient of determination r 2 = 0.87) and sediment routing based on bed level, (with resultant r 2 = 0.98 and Mean Absolute Deviation of 0.95). The Ackers-White equation was used in the HEC-RAS model for sediment routing because of the wide range of sediment sizes in the study case. The resultant total accumulated sediment load volume was 1.13 km 3 , a value that is very close to the measured values (1.143 km 3) obtained from a previous bathymetric survey. Furthermore, the model indicated most of the sediment (80.7%) was deposited during the first five of the dam operation.

Dokan is a multipurpose dam located on the Lesser Zab River in the Iraq/Kurdistan region. The dam has operated since 1959, and it drains an area of 11,690 km 2. All reservoirs in the world suffer from sediment deposition. It is one of the main problems for reservoir life sustainability. Sustainable reservoir sediment-management practices enable the reservoir to function for a longer period of time by reducing reservoir sedimentation. This study aims to assess the annual runoff and sediment loads of the Dokan Dam watershed using the soil and water assessment tool (SWAT) model to evaluate the relative contributions in comparison with the total values delivered from both watershed and Lesser Zab River and to identify the basins with a high sediment load per unit area. These help in the process of developing a plan and strategy to manage sediment inflow and deposition. The SUFI-2 program was applied for a model calibrated based on the available field measurements of the adjacent Derbendekhan Dam watershed, which has similar geological formations, characteristics and weather. For the calibration period (1961-1968), the considered statistical criteria of determination coefficients and Nash-Sutcliffe model efficiency were 0.75 and 0.64 for runoff while the coefficients were 0.65 and 0.63 for sediment load, respectively. The regionalization technique for parameter transformation from Derbendekhan to Dokan watershed was applied. Furthermore, the model was validated based on transformed parameters and the available observed flow at the Dokan watershed for the period (1961-1964); they gave reasonable results for the determination coefficients and Nash-Sutcliffe model efficiency, which were 0.68 and 0.64, respectively. The results of SWAT project simulation for Dokan watershed for the period (1959-2014) indicated that the average annual runoff volume which entered the reservoir was about 2100 million cubic meters (MCM). The total sediment delivered to the reservoir was about 72 MCM over the 56 years of dam life, which is equivalent to 10% of the reservoir dead storage. Two regression formulas were presented to correlate the annual runoff volume and sediment load with annual rain depth for the studied area. In addition, a spatial distribution of average annual sediment load was constructed to identify the sub basin of the high contribution of sediment load.

This paper presents two different terrain modeling techniques to assess sedimentation employing single-beam bathymetric data, using as a case of study a Peruvian reservoir located in the Andes Mountains. Both methods used the same input data. The first method employed was the traditional method and the second was Insertion of Mesh Points (IMP). In agreement with previous findings, the IMP method produced lower sedimentation values but proved to be satisfactory for the case.

Even though lake sediments constitute a significant long-term carbon sink, studies on the regulation of carbon burial in lakes sediments have, to date, been surprisingly few. We investigated to what degree the organic carbon (OC) being deposited onto the bottom of Lake Kinneret (Israel) is buried in the sediment at four different sites with varying degrees of oxygenation and varying supply of allochthonous particles from the River Jordan. For estimation of the OC burial efficiency (OC BE), i.e., the ratio between buried and deposited OC, we calculated OC burial from dated sediment cores, and calculated OC deposition using three different approaches. Calculation of OC deposition from sediment trap-derived mass deposition rates multiplied with the OC content of surface sediment yielded OC BE values that were at odds with published values for sediments dominated by autochthonous OC sources. Calculation via sediment trap data on organic matter flux collected within the Lake Kinneret monitoring program, as well as calculation of OC deposition as the sum of OC burial plus OC mineralization, returned fairly congruent estimates of OC BE (range 10-41%), but only if the sediment trap data were corrected for the proportion of resuspended particles in the traps. Differences in OC BE between sites were small, indicating that OC source (common to all sites) was a more important regulator of OC BE in Lake Kinneret than oxygen exposure or mineral particles characteristics.

Dam construction is one of the methods for storing surface water. Estimating the service life and economic efficiency of dam is one of the most important cases in estimating the design of it. The most important problem that threatens the useful life of the dam is input sediment to reservoir. Life expectancy of a dam reservoir is measured with respect to the incoming sediments. Estimation of suspended sediment in rivers plays an important role in estimating the useful life of dams. Many methods such as statistical methods USBR (United States Bureau of Reclamation) and FAO (Food and Agriculture Organization) and moderate categories method are used to measure suspended. In this research the mentioned statistical and some other methods are used in Mahabad dam. By using sediment volume and the estimated flow rate Sediment loads is measured at different times in this method and its accuracy is estimated by correlation coefficient. The gained results show that the sedimentation estimates by using USBR and FAO with two correlation curves methods are useful and have more correlation coefficient.

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.

Reservoir silting is one of the principal problems affecting the performance of dams in Algeria from the standpoint of reservoir capacity for storage. Foum El Kherza Reservoir (also known as Foum El Gherza), near Biskra Town, Algeria, is subject to dredging operations with the intent of recovering 70% of its initial storage capacity of 47 hm3 (million cubic metres). The forecasting of sediment volume trapped in the reservoir is essential to plan the future use of this resource and to sustain irrigation for the palm groves characteristic of the region. However, there are currently no sediment data, nor a sediment rating curve, for predicting sediment inflow based on hydrological data. This paper describes the optimization of a cumulative trapped sediment curve for Foum El Kherza Reservoir based on 44 years of daily inflows, by using a spreadsheet optimization tool, Microsoft Excel® Solver to calibrate the cumulative sediment load against the cumulative sediment inflow as documented b...

Understanding the characteristics of a reservoir ecosystem is crucial in water
resources management. The aims of this study are to investigate the limnological
characteristics and spatial physicochemical properties of water quality in the
Sembrong Reservoir. This study includes investigation of spatial variability of
sediment properties and the quality of bottom sediment and long term sedimentation
rate in relation to land use change and major hydrology events. The data collection
was carried out from November 2011 to January 2013. Vertical sampling of reservoir
water was conducted and its physical properties were measured in situ. Water samples
were also analysed in laboratory for Al, Fe, K, Na, Mg, Ca, Fe, Mn, Zn, Cu, As, Pb
and Total Phosphorous. Stable isotopes (18O and 2H) were measured using SERCON
GEO 20–20 Continuous Flow Isotope Ratio Mass Spectrometer (CF–IRMS). A total
of nine sediment cores were analysed for fallout 210Pb and 137Cs radioisotopes activities
by Gamma Spectrometer. Sediment samples were also analysed for Total Carbon and
Total Nitrogen and grain size distribution. Polymictic pattern was observed in this
reservoir, especially during wet months. Thermal stratification occurred at depths
between 3m and 4 m. The occurrence of photosynthesis at depth less than 3m increased
phytoplankton productions. Manganese (Mn) and iron (Fe) concentrations were
subjected to geochemical processes, particularly redox reaction. The mean
concentrations of heavy metals in the water column decreased in the following order:
Fe > Mn > Zn > Cu > As > Pb. Based on Carlson’s Trophic State the Sembrong
Reservoir is classified as hypereutrophic. On the other hand, the heavy metal
concentrations as determined by the Heavy Metal Evaluation Index (HEI) fall under
slightly polluted to polluted. Factor analysis suggested that the heavy metals are
originated from modern agricultural plots. Higher heavy metal contents were observed
in the west wing. This could be associated with micronutrient fertilizer from oil palm
plantation with remarkable increases in the Enrichment Factor and Geoaccumulation
Index for Zn, Cu, and Mn. Sediment mixing and digenesis processes influenced the
deposition of bottom sediment. Given the irregularities of 210Pb, long-term
sedimentation rates were calculated by dividing the sediment thickness over a period.
Higher sedimentation rates were observed at cores S1 and S6A with sedimentation
rates of 1.10 and 1.17 cm/year, respectively. Forest clearing for oil palm plantation,
dam development, and modern agricultural activities play important roles in the spatial
and temporal distributions of sediment and water quality. This study highlighted the
importance of limnology in controlling the physical and chemical processes in a
reservoir ecosystem. The physicochemical properties of sediment also significantly
influence the quality of reservoir ecosystem. Therefore, a comprehensive management
plan to preserve the reservoir ecosystems is needed to ensure the sustainability of water
resources.

Accumulation and deposition of sediments in waterbody affect the seepage capacity that could lead to improper water balance and results in the water level rise. is study analysed the influence of sedimentation on seepage capacity in Lake Nakuru and the impact of sediment characteristics to the water seepage and the flow rate formation at the lake bed level. e study was performed by sampling and analysing the sediment cores from two locations in the lake. e sediment hydraulic properties, i.e., moisture and porosity, particle sizes, and hydraulic conductivity, were determined using the oven-drying method, sieve analysis, hydrometer analysis, and falling head tests, respectively. e results showed that the lake sediment sample from location P1 had an average ratio of 39.38% for silty soil, 34.00% for clayey sediment, and 26.63% for fine-sand sediment particles with the maximum permeability coefficient of 3.37 * 10 − 5 cm/s, while the one from location P2 had an average ratio of 63.17% for sand, 20.17% for fine particles, and 16.67% for gravels with the maximum permeability coefficient of 0.010793 cm/s. e hydraulic conductivity of sediment sample from location P1 and P2 increased along the core depth. is could lead to the rise of water level due to the decreases of water movement induced from the sediment cementation in the top layers under the waterbody. Sedimentation affects Lake Nakuru water volume and water balance; hence, there is a need to control the inflow of sediment resulting from anthropogenic activities in the watershed.

Optic remote sensing provides information on elevation contours, in the form of water spread area of reservoirs, which is the only thematic information required to assess the sedimentation in a reservoir. However, due to the presence of cloud in the optic satellite data during monsoon and other extreme weather conditions it cannot be used. To overcome this situation microwave satellite data (Sentinel 1-SAR) is used on Hirakud reservoir wherein, most of the year it is covered by clouds. For the year 2018-19, eleven SAR pass were available between the water level 181.23 m (near MDDL) and 190.19m (near FRL). The pre-processing techniques were applied to all the eleven SAR, dual polarized data. From the VV+VH data thresholiding methodology was utilized to identify the water pixels. It was found that the water pixels contain values ranging from-40.56db to-20db, these pixels were extracted and the water spread area occupied by all the eleven SAR data were estimated. These water spread areas were used in simple volume estimation trapezoidal formula and the volume between different water levels were calculated. These volumes were added up to assess the revised capacity between the water level 181.23 m and 190.19m for the period 2018-19. The assessment revealed that the capacity between these water levels is 32.29 M.cum/year. This study shows that reservoir water spread and in turn the amount of sediment deposited in a reservoir are can be effectively estimated using Sentinel1-SAR, which is a replacement to the cloud covered optic data.

The Dukan Dam Reservoir (DDR) in the Kurdistan Region of Iraq has been studied to determine the characteristics and nature of the reservoir and the deposited sediments on its bottom surface. This study was achieved by doing a field survey and grain size analyses of the collected sediment samples at 32 locations representing the whole reservoir area that had been created when the Lesser Zab River was dammed in 1959. The Dukan Dam, which is a multipurpose concrete arch dam, was built on the Lesser Zab River for controlling its flood during high rainfall seasons, irrigation and power generation. The catchment area is 11,690 km 2. The surface area of the reservoir is 270 square kilometers and the volume is 6.870 × 106 m 3 at normal operation level (El. 511.00 m. a.s.l.). The minimum drawdown level is at elevation 469 m above sea level (a.s.l.). The live storage is 6.14 × 106 m 3 while the remainder is dead storage. The reservoir has a surface area that reaches 270 square kilometers and is composed of two sub-reservoirs connected by a narrow channel that has a length of 5 kilometers. The relatively bigger reservoir is located in the north and has a triangular shape with a surface area approximately 250 square kilometers. The smaller sub-reservoir is located down south where the dam exists and it has irregular rectangular shape. Thirty-two sediment samples were collected from the bottom of Dukan reservoir. The bed of the reservoir is mainly composed of 15% gravel, 14% sand, 48% silt and 23% clay respectively. Most of the sediments are very fine grained, very poorly sorted, strongly coarse skewed and mesokurtic.

The sediment accumulation in rivers and the sediment deposition in the reservoirs is currently influencing a remarkable impact on the land and water resources in Kenya. Inappropriate land use and wastes disposal in the watershed are anthropogenic activities resulting in the contamination of the water body in Lake Nakuru. This research study focusses in the lake sedimentation assessment and examination of sediments impacts on the storage loss in Lake Nakuru. This was achieved by establishing the engineering concepts using Bathymetric Surveying System (BSS) comprises navigation twin boats system (Dual-Jon-Boats), builtin Global Positioning System (GPS) for collecting spatial data, acoustic multi-frequency system with higher frequency of 200 kHz for determination of surface of the sediments and the lower frequency of 12 kHz for determination of deposited sediments layer to pre-impoundment levels of the Lake. The software like Depthpic 5.0.2, Surfer 15.5 and ArcGIS 10.3 were used for mapping, gridding and morphometric analysis. The study results show that the lake depth increasing from the shoreline to the middle patch of the lake with the maximal depth of 6.2 meters and the water storage volume of 264,699,344.54 m 3. The sediment deposition with the layer thickness varies from 0 m up to 0.7 m (maximum) and the total sediment storage capacity of 24,191,688.67 m 3 , this implies that the sediment storage in the lake occupies 8.37 % of its actual storage capacity. The water and sediment storage status cater to accurate information to the water resources managers in making decisions to the resources' management in or around the lake.

En este trabajo se describen algunas experiencias sobre la sedimentación en embalses en zonas tropicales, en los que por el importante aporte de sedimentos han requerido medidas particulares para asegurar su desempeño y lograr una vida útil aceptable. El embalse de Cachí en Costa Rica, utilizado para generación eléctrica, en su puesta en marcha en 1966 contaba con un embalse de 54 hm3. La cuenca tributaria de 783 km2 tiene una cobertura boscosa del 50%, y aun así, dadas las altas precipitaciones y pendientes, y adversas condiciones geotectónicas, tiene una producción de sedimentos de alrededor de 1200 ton/km2/año. La acumulación de sedimentos ha requerido que desde 1973 anualmente se realicen vaciados de limpieza, operación que ha permitido descargar una gran parte de los sedimentos acumulados y mantener el 80% de volumen original luego de 38 años de funcionamiento. Por su parte, el embalse de Angostura, situado aguas abajo, y que inició su operación en el 2001, tiene un embalse de ...

The Dukan Dam Reservoir (DDR) in the Kurdistan Region of Iraq has been studied to determine the characteristics and nature of the reservoir and the deposited sediments on its bottom surface. This study was achieved by doing a field survey and grain size analyses of the collected sediment samples at 32 locations representing the whole reservoir area that had been created when the Lesser Zab River was dammed in 1959. The Dukan Dam, which is a multipurpose concrete arch dam, was built on the Lesser Zab River for controlling its flood during high rainfall seasons, irrigation and power generation. The catchment area is 11,690 km 2. The surface area of the reservoir is 270 square kilometers and the volume is 6.870 × 106 m 3 at normal operation level (El. 511.00 m. a.s.l.). The minimum drawdown level is at elevation 469 m above sea level (a.s.l.). The live storage is 6.14 × 106 m 3 while the remainder is dead storage. The reservoir has a surface area that reaches 270 square kilometers and is composed of two sub-reservoirs connected by a narrow channel that has a length of 5 kilometers. The relatively bigger reservoir is located in the north and has a triangular shape with a surface area approximately 250 square kilometers. The smaller sub-reservoir is located down south where the dam exists and it has irregular rectangular shape. Thirty-two sediment samples were collected from the bottom of Dukan reservoir. The bed of the reservoir is mainly composed of 15% gravel, 14% sand, 48% silt and 23% clay respectively. Most of the sediments are very fine grained, very poorly sorted, strongly coarse skewed and mesokurtic.

In order to study the sediment dynamics of Ribarroja Reservoir, a bathymetric campaign was carried out in 2007 using a precision multi-beam probe. One year later, another campaign was performed. This second bathymetric campaign focused only in the tail of Ribarroja Reservoir (confluence Ebro-Segre Rivers), it was designed to study suspended sediment entering the reservoir and its bed evolution in one year. Between 2007 and 2008 campaigns, only one major flood episode took place (from late May to early June 2008). Two different digital elevation models of Ribarroja Reservoir were generated. The analysis and comparison of 2007 and 2008 digital elevation models showed that 170.000 m 3 of sediment (initially located immediately after the Segre-Ebro confluence) were resuspended and displaced about 4 km downstream. This study was complemented with a numerical simulation using the suspended sediment transport module implemented in a two-dimensional depth averaged model.

Sediment particles originating from erosion processes in the catchment are propagated along with the river flow. When the flow of a river is stored in a reservoir, the sediment settles in the reservoir and reduces its capacity. Reduction in the storage capacity of a reservoir beyond a limit hampers the purpose for which it was designed. Thus assessment of sediment deposition becomes very important for the management and operation of such reservoirs. Some conventional methods, such as hydrographie survey and inflow-outflow approaches, are used for estimation of sediment deposition in a reservoir, but these methods are cumbersome, time consuming and expensive. There is a need for developing simple methods, which require less time and are cost effective. In this study, a remote-sensing approach has been attempted for assessment of sedimentation in Bhakra Reservoir, located on the Satluj River in the foothills of the Himalayas. Multi date remote sensing data (1RS-1B, L1SS II) provided the information on the water-spread area of the reservoir, which was used for computing the sedimentation rate. The revised capacity of the reservoir between maximum and minimum levels was computed using the trapezoidal formula. The loss in reservoir capacity due to deposition of sediments for a period of 32 years was determined to be 807.35 Mm', which gives an average sedimentation rate of 25.23 Mm' year" 1 . The average rat£ of sedimentation using hydrographie survey data for the same period was 20.84 Mm' year" 1 . A comparison of the results shows that the rate of sedimentation assessed using the remote sensing based approach was close to the results obtained from the hydrographie survey.

One of the fundamental issues with the operation of surface water resources is erosion, and
sediment transport. Reducing the reservoir’s useful life and declining the reservoir storage are subsequences
of erosion and sediment transport. These natural events occur in different geographical circumstances. Since
the major part of the watershed sedimentation consists of suspended sediments, the amount of suspended
loads, has a special priority. (Kişi 2007) Determining the amount of erosion or sediment transportation is
practically very difficult. So far different methods have been proposed and among are methods for estimating
the suspended load of rivers, hydrometer station sediment survey, sediment rating curve approach, depth
evaluation and extrapolation are common. In order to determine the density of sediments, rating curve
methods are the most popular. The rating curve method uses power relations fitted curve water discharge and
sediment discharge. Hydrologists use rating curve methods in the case that there is no real suspended load, or
if the sedimentation data is not accurate enough and remarkable differences in results are observed between
measurement data and outcome, or when there are no long term measurements. It should be noted that
measuring and monitoring the amount of suspended load by using depth evaluation method is costly. In this
study, the FAO and USBR approaches are used to estimate the performance of sediment rating curve
methods, and the results are compared with the results of the depth evaluation of Sefidroud watershed. The
results of this study indicate that USBR method can be introduced as an optimization method in the
Sefidroud watershed by using classified statistics.

In Lake Kinneret, the majority of photosyntetically produced organic carbon (OC) is cycled through the microbial loop. Taken together, bacterial production (BP) and bacterial respiration (BR), i.e., bacterial carbon demand (BCD), accounted for about 65 % of gross primary production (GPP), measured biweekly and averaging 2.3 g C m–2 day–1 during the last decade (2001–2011). Community respiration (CR) was 2.1 g C m–2 day–1. The major contributors to total CR were bacterial and phytoplankton respiration (~80%) while zooplankton respiration accounted for the reminder. Most (~ 83 %) of the OC input were eventually respired, ~3 % lost to outflows, while ~15 % of the total OC input were transferred annually to the sediments. Here oxic mineralization is gradually replaced by anoxic processes as a function of the availability of suitable electron acceptors. After the depletion of oxygen in the hypolimnion, sulfate (500 μM) becomes the dominant oxidant. Depending on the settling flux of OC sedimentary sulfate reduction (SR) rates were measured from 0.01 to 1.67 µmol cm–3 day–1 in December and July, respectively. SR is the dominant anaerobic terminal decomposition process in Lake Kinneret and is responsible for the accumulation of sulfide in the hypolimnion to concentrations up to 400 μM. Methanogenesis is restricted to those sediment layers that are depleted of sulfate (below 3–5 cm). Seasonal profiles and 13C signatures of dissolved methane in the sediment pore water of Lake Kinneret have indicated anaerobic methane oxidation in the deeper sediments (below 20 cm), with Fe(III) as electron acceptor. Lake Kinneret resembles the first aquatic ecosystem where the existence of this process could be verified. Changes in the watershed and lake environment are suggested as possible causes for the apparently significant declines in bacterial numbers, BP, and BCD that have taken place over the last decade in Lake Kinneret.
Within this Chapter:
    Heterotrophic Bacterial Production, Respiration, and Growth Efficiency
    Community Respiration
    Sulfate Reduction
    Methanogenesis
    Fluxes of Organic Carbon in the Epilimnion