Distribution of functional microorganisms and its significance for iron, sulphur, and nitrogen cycles in reservoir sediments

The biogeochemical cycles of sulphur(S),iron(Fe)and nitrogen(N)elements play a key role in the reservoir ecosystem.However,the spatial positioning and interrelationship of S,Fe and N cycles in the reservoir sediment profile have not been explored to a greater extent.Here,we measure the gradients of Fe^(2+),SO_(4)^(2-),NO_(3)^(-),NH_(4)^(+),DOC,TC and TN in the pore water of the sediment,and combining the vertical distribution of the functional microorganisms involved in S,Fe and N cyclings in the sediments to determine the redox stratification in the sediment.It is found that the geochemical gradient of S,Fe and N of the reservoir sedimentary column is mainly defined by the redox process involved in the related functional microorganisms.According to the type of electron acceptor,the sediment profile is divided into 3 redox intervals,namely aerobic respiration(0–10 cm),denitrification/iron reduction(10–28 cm)and sulfate reduction(28–32 cm).In the aerobic respiration zone,NH_(4)^(+)is oxidized by aerobic AOB to NO_(3)^(-)(0–5 cm),and Fe^(2+)is oxidized by microaerobic FeRB to Fe^(3+)(3–10 cm).In the denitrification/iron reduction zone,Acinetobacter and Pseudomonas,as the dominant NRB genera,may use nitrate as an electron acceptor to oxidize Fe^(2+)(11–16 cm).The dominant genera in SOB,such as Sulfururvum,Thiobacillus and Thioalkalispira,may use nitrate as an electron acceptor to oxidize sulfide,leading to SO_(4)^(2-)accumulation(14–24 cm).In the sulfate reduction zone,SO_(4)^(2-)is reduced by SRB.This study found that functional microorganisms forming comprehensive local ecological structures to adapt to changing geochemical conditions,and which would be potentially important for the degradation and preservation of C and the fate of many nutrients and contaminants in reservoirs.

The analysis on reservoir sediment deposition and downstream river channel scouring after impoundment and operation of TGP

According to the measured data after impoundment and operation of the Three Gorges Reservoir,the reservoir sediment deposition and downstream river channel scouring are described briefly and compared with the research results achieved in the demonstration stage.It is indicated through analysis that the reservoir sediment deposition and downstream river channel scouring during 8-year impoundment and operation are still within the original forecast,so the original forecasting results are feasible.The further observation and comparison should be conducted because the comparison between the observed data and the original forecast is not so sufficient in time and the prototype observation and related research work should be strengthened in the future.

Distribution, sources and potential toxicological significance of polycyclic aromatic hydrocarbons(PAHs) in Guanting Reservoir sediments, China

The Guanting Reservoir lost its function as the second biggest drinking water source for Beijing due to the pollutions from the upstream flow of Yongding River in 1997 From 1998, lots of studies were carryied out to renew the function of Guanting Reservoir as domestic drinking water source before 2008 Olympic Games. This is the first time that polycyclic aromatic hydrocarbon concentrations in the surface sediment of Guanting Reservoir have been analyzed. A distinctive spatial distribution of PAHs was observed. Sediments from four sites along Inlet of Yongding River to reservoir bam had PAHs concentrations of 1377—2855 μg/g dw in descending order. The composition of PAHs is investigated and used to assess petrogenic, combustion and naturally derived of the sediments samples of Guanting Reservoir. Special PAHs ratios, such as phenanthrene/anthracene(P/A) and fluoranthene/pyrene(Fl/Pyr) were calculated to assess the relative importance of different origins. The data confirmed a relatively high level of petrogenic contamination in four sites. These high PAHs levels were associated with the input of untreated and partially treated industrial sewage. In addition, the concentrations of PAHs compounds of samples indicated that sediments of reservoir were most likely to pose potential biological impairment.

Channel Evolution of Sandy Reservoir Sediments Following Low-Head Dam Removal, Ottawa River, Northwestern Ohio, U.S.A.

Dozens of low-head dams are removed annually for reasons of obsolescence, financial liability, public safety, or as part of aquatic ecosystem restoration. Prior to removing a dam, hydrologic and sedimentologic studies are used to predict channel changes that would occur after the proposed dam removal. One commonly used predictive approach is a channel evolution model (CEM). However, most CEMs assume that the reservoir has trapped cohesive silts and muds. This study looks at the effects of low-head dam removal on a reservoir in filled with sand-rich sediment. The Secor Dam (2.5 m tall, 17 m wide) was constructed on the Ottawa River in northwestern Ohio (USA) during 1928 and was removed in 2007. High resolution channel cross-sections were measured at 17 locations prior to dam removal and re-measured every approximately 30 days for 6 months following the removal. Sediment sampling, sediment traps, substrate sampling, differential GPS tracking of channel bed forms and sediment coring were also used to characterize the channel sediment response to dam removal. Breaching of the dam produced a diffuse nickzone which was the width of the channel and about 10 m in length. One initial response was downstream migration of a sediment wave at rates up to 0.5 m/hr. The overall effect was erosion of the former reservoir to a distance of 150 m upstream of the former dam. Portions of the former reservoir were incised >1 m. Within the first 6 months after removal, approximately 800 m3 of sand had been mobilized from the former reservoir, transported downstream past the former dam, and had primarily in-filled pre-existing pools within a reach approximately 150 m downstream of the former dam. This behavior significantly differs from the predicted results of current CEMs which anticipate a first flush of suspended sediment and minor deposition of bed load materials in the channel downstream of the former dam.

Estimation of Small Reservoir Sedimentation in Semi-Arid Southern Zimbabwe

Small surface reservoirs play an important role of providing ready and convenient source of water for various uses in semi-arid areas which are characterized by erratic and low rainfall. Lack of current data on reservoir capacity loss due to sedimentation is one of the challenges to the sustainable management of surface reservoirs. The study investigated the capacity loss due to sedimentation from 2000-2012, and estimated the trap efficiency of the Mutangi reservoir which is located in semi-arid Chivi, Southern of Zimbabwe. Hydrographic surveys, grab sampling and water depth-capacity methods were used to determine the capacity of the dam as of 2012. To compute capacity loss from 2000 to 2012, the 2000 and 2012 dam capacities were compared whilst the trap efficiency of the reservoir was determined using a set of empirical models that relates trap efficiency to the capacity-watershed area ratio and capacity-inflow ratio. The results show that Mutangi reservoir has a trap efficiency of 95% - 98% (av = 96.4%) and has lost 37% of its capacity due to sedimentation in 12 years (2000 and 2012). Rates of sedimentation were 8539 t·yr-1, 9110?t·yr-1 and 8265 t·yr-1 for the hydrographic survey, grab sampling and water depth-capacity method respectively, and the little difference in these figures demonstrates that any method can be used to determine sedimentation rates. The area specific sediment yield (ASY) ranged from 14 - 15.5 t·ha-1·yr-1 (av = 14.956 t·ha-1·yr-1). At the current rate of sedimentation the projected dead level of the reservoir will be lost to sedimentation in 8 years while the useful life of the reservoir is estimated to be 30 years. Capacity loss due to sedimentation is further complicating the already strained water scarcity situation in semi-arid areas and management decisions should be made based on the current sedimentation rates estimated by different methods. These results imply that management practices that reduce erosion, hence sedimentation in these small reservoirs should be practiced in order to prolong their lifespan.

RESERVOIR SEDIMENTATION AND TRANSFORMATION OF MORPHO-LOGY IN THE LOWER YELLOW RIVER DURING 10 YEAR'S INITIAL OPERATION OF THE XIAOLANGDI RESERVOIR

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 × 10^9 m3 of sediment, and caused the total erosion of 1.891 × 10^9t 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.

Quantification of TOC and TN in reservoir sediments using Fourier transform infrared spectroscopy

This study aims to quantitatively assess the total organic carbon(TOC)and total nitrogen(TN)content of reservoir sediments in southwest China using Fourier transform infrared spectroscopy(FTIRS).FTIRS measurements were performed on 187 sediment samples from four reservoirs to develop calibration models that relate FTIR spectral information with conventional property concentrations using partial least squares regression(PLSR).Robust calibration models were established for TOC and TN content.The external validation of these models yielded a significant correlation between FTIR-inferred and conventionally measured concentrations of R^(2)=0.88 for TOC,R^(2)=0.90 for TN.This method can be performed with a small sample size and is non-destructive throughout the simple measurement process.The TOC and TN content in the sediment can be determined with high effectiveness without being overly expensive,making it an advantageous method when measuring a large number of samples.

Sedimentation Processes and Useful Life of Mosul Dam Reservoir, Iraq

The sedimentation process is the most important problems that affects directly the performance of reservoirs due to the reduction of the storage capacity and possible problems effecting the operation. Thus periodic assessment of the storage capacity and determining sediment deposition patterns is an important issue for operation and management of the reservoirs. In this study, bathymetric survey results and an analytical approach had been used to assess the characteristics of sedimentation and estimate the useful life of Mosul Reservoir. It is located on the Tigris River in the north of Iraq. The water surface area of its reservoir is 380 km2 with a designed storage capacity of 11.11 km3 at a maximum operating level (330 m a.s.l). The dam started operating in 1986. No detailed study was yet carried out to assess its reservoir. The present study indicated that the annual reduction rate in the dead and live storage capacities of the reservoir is 0.786% and 0.276% respectively. The observed results (bathymetric survey) and algebraic formula show approximately that the useful life of Mosul dam reservoir is about 125 years. Furthermore, the stage-storage capacity curves for the future periods (prediction curves) were established using bathymetric survey data.

Experimental Analysis of Sediment Deposition Due to the Effect of an Upstream Reservoir Backwater

The phenomenon of aggradation due to sediment accumulation upstream reservoirs had been studied in this research. For this purpose, groups of experiments were conducted in a laboratory with 25 m long, 0.80 m wide and 0.70 m deep channel. A block was built at the end of the channel to work as a dam to impound water. The channel was supplied with drainage pipes on both sides to release water out in a manner similar to what happens in reservoirs. The bed of the channel was filled with sand of 0.80 mm median sieve diameter and 0.72 geometric standard deviation. The slope was 0.0093 for all experiments. Two sizes of sand were used representing the sediment. The median diameter and geometric standard deviation of the first were 0.365 mm and 0.46 mm, respectively. The second sample had 0.65 mm median diameter and 0.67 standard deviation. A total of 70 experiments were conducted in two groups to examine effects of sediment transport rate, particle size of sediment and flow velocity on aggradation characteristics. The results showed that there was a strong linear direct relationship between aggradation elements （length and depth） with the rate of sediment transport. Groups of dimensionless parameters affecting the aggradation characteristics were used to develop empirical equations to predict the length, maximum depth of aggradation and predict transient bed profile. The results of empirical approach were compared with the measurement data and previous numerical method. The results indicated that the percentage error was 19% to 31% for length of aggradation and -21% to 26% for maximum depth of aggradation. The results also showed that the sediment materials were deposited closer to the body of the dam when the released water from the dam is higher than the inflow.

Features and genesis of Paleogene high-quality reservoirs in lacustrine mixed siliciclastic–carbonate sediments, central Bohai Sea, China

The characteristics and formation mechanisms of the mixed siliciclastic-carbonate reservoirs of the Paleogene Shahejie Formation in the central Bohai Sea were examined based on polarized light microscopy and scanning electron microscopy observations, X-ray diffrac- tometry, carbon and oxygen stable isotope geochemistry, and integrated fluid inclusion analysis. High-quality reservoirs are mainly distributed in Type I and Type II mixed siliciclastic-carbonate sediments, and the dominant pore types include residual primary intergranular pores and intrafossil pores, feldspar dissolution pores mainly devel- oped in Type II sediments. Type I mixed sediments are characterized by precipitation of early pore-lining dolo- mite, relatively weak mechanical compaction during deep burial, and the occurrence of abundant oil inclusions in high-quality reservoirs. Microfacies played a critical role in the formation of the mixed reservoirs, and high-quality reservoirs are commonly found in high-energy environ- ments, such as fan delta underwater distributary channels, mouth bars, and submarine uplift beach bars. Abundant intrafossil pores were formed by bioclastic decay, and secondary pores due to feldspar dissolution further enhance reservoir porosity. Mechanical compaction was inhibited by the precipitation of pore-lining dolomite formed during early stage, and oil emplacement has further led to the preservation of good reservoir quality.

Changjiang River sediment delivering into the sea in response to water storage of Sanxia Reservoir in 2003

The Sanxia Reservoir on the Changjiang River stored water from 1 to 10 June and from 25 October to 5 November in 2003, elevating the water level to 135 and 139 m above mean sea level at the dam, respectively. A monthly dataset of water discharge, suspended sediment concentration （SSC） and sediment load of the Changjiang River from 1953 to 2003 measured at the Datong Hydrological Gauging Station of the downstreammost Changjiang River was mainly used to examine the Changjiang River sediment delivering into the sea in 2003 in response to the Sanxia Reservoir water storages in the same year. The results show that （1） compared with those in 2002, 2001, and the multi-yearly （1953-2000） average, both annual SSC and sediment load at Datong in 2003 were markedly reduced, and they were even smaller than the multi-yearly （1953-2000） minimum, although the annual runoff in 2003 did not change largely; and （2） compared with those in the corresponding months in 2002, 2001 and the multi-monthly average from 1953 to 2000, monthly SSC and sediment load at Datong both in June and November of 2003 were also markedly reduced, and those in June 2003 were even smaller than the multi-monthly minimum from 1953 to 2000. These may indicate that sediment sedimentation in the Sanxia Reservoir resulting from the Sanxia Reservoir water storage should be the main cause of the decreased annual and monthly SSC and sediment load of the Changjiang River into the sea in 2003. Besides, it seems that the Sanxia Reservoir water storage in the early June （flood season） of 2003 had more impacts on the decreased monthly SSC into the sea than that in the late October and early November （approximately non-flood season） of 2003.

Using seismic surveys to investigate sediment distribution and to estimate burial fluxes of OC, N, and P in a canyon reservoir

As a high-precision survey method,seismic surveying has been increasingly applied to inland water research,although its application to artificial reservoirs has remained limited.As a special artificial water body,reservoirs have important effects on the fluvial transport of material from land to ocean,and inevitably have complex terrain which can complicate and distort the results of seismic surveys.Therefore,there are still some problems need to be resolved in the application of seismic surveys in reservoirs with complex terrain.For this study,the Dongfeng Reservoir located in the upper reaches of the Wujiang River was chosen as an example to test the seismic survey method.Our testing showed that(1)because of the complex underwater terrain,the signal-to-noise ratio of the echo signal in canyon reservoir is low,making it difficult to determine sediment layers thicknesses in some areas;and(2)due to the large spatial heterogeneity of sediment distribution,insufficient density of cross-sections can lead to inaccurate interpolation results.To improve the accuracy of calculations,a mathematical method was used.Ultimately,the total burial mass of sediment was estimated at 2.85 x 107 tons,and the average burial rates of total organic carbon,total phosphorus,and total nitrogen were estimated at 0.194,0.011,and 0.014 g cm-2 year-1,respectively.These values were close to the results of previous studies and hydrographic station data,indicating that seismic survey can be a reliable and efficient method for the mapping of reservoirs.

Equilibrium sediment transport in lower Yellow River during later sediment-retaining period of Xiaolangdi Reservoir

The Xiaolangdi Reservoir has entered the later sediment-retaining period, and new sediment transport phenomena and channel re-estab- lishing behaviors are appearing. A physical model test was used to forecast the scouring and silting trends of the lower Yellow River. Based on water and sediment data from the lower Yellow River during the period from 1960 to 2012, and using a statistical method, this paper analyzed the sediment transport in sediment-laden flows with different discharges and sediment concentrations in the lower Yellow River. The results show that rational water-sediment regulation is necessary to avoid silting in the later sediment-retaining period. The combination of 3 000 m^3/s 〈 Q 〈 4 000 m^3/s and 20 kg/m^3 〈 S 〈 60 kg/m^3 （where Q is the discharge and S is the sediment concentration） at the Huayuankou section is considered an optimal combination for equilibrium sediment transport in the lower Yellow River over a long period of time.

PROBLEMS OF RESERVOIR SEDIMENTATION IN CHINA

As there are many heavily sedimentladen rivers in China, with high sediment concentration and a large quantity of sediment load, the sedimentation problems of the reservoirs built on those rivers are so serious that the amount of sediment deposited in the reservoirs is great and the rate of sedimentation is accelerated. According to the statistics, up to the end of 1981, a total amount of 11.5×109m3 of sediment were accumulated in those reservoirs, i.e. 14.2% of the total designed capacity were lost. The average annual loss in storage capacity reached 2.3 percent, being the highest in the world. Silting of impounding lakes not only has an effect on the benefits of the reservoirs and seriously threatens the life of reservoirs, but also results in many environmental problems which were not fully estimated in the planning of the reservoirs. In this paper, the situation of reservoir deposition in China are described from the following aspects: 1) the characteristics of hydrology and sediment of the rivers; 2) the seriousness of reservoir sedimentation in China; 3) problems caused by reservoir deposition; 4) the methods of minimizing sediment deposition, etc.

Monitoring and Evaluating the Sedimentation Process in Mosul Dam Reservoir Using Trap Efficiency Approaches

Reservoirs are usually exposed to sediment accumulation problems that will lead to reduction in their storage capacity. This problem directly affects the performance of the dams and causes shortage of their useful life. The simplest technique to estimate sediment deposition rate is using sediment rating curve with sediment trapping efficiency (TE) of the reservoir. Many empirical and semi-empirical approaches have been suggested for to determine this term depending on the annual inflow rate, reservoir characteristics and features of the catchments area. In this study six different empirical methods depending on the residence time principle (water retention time) were used. These approaches were reviewed and applied to determine TE of Mosul dam reservoir (MDR) for period 1986 to 2011. The monthly operating data for inflow, outflow and water elevations for MDR were used to determine monthly TE and long-term TE for whole period of MDR using the mentioned methods. Furthermore, the monthly inflow rate for River Tigris upstream MDR, its sediment rating curve and sediment feeding from valleys around MDR were used to estimate the amount sediment coming to the reservoir. The results provided by these methods for TE with sediment coming to MDR were used to compute the amount of sediment deposited in MDR on monthly bases during this period. The results obtained were evaluated using observed bathymetric survey data that had been collected in 2011 after 25 years of the operation of the dam. The results showed all the mentioned methods gave convergent results and they were very close to bathymetric survey results for estimating the volume of sediment deposited especially that proposed by Ward which gave 0.368% percentage error. Furthermore, the result computed using monthly TE gave good agreement if compared with that long-term TE where the percentage error was ranging between –3.229% to 1.674% for monthly adopted data and –4.862% to?–2.477% for whole period data. It is believed that this work will help others to use this procedure on other reservoirs.

基于正交试验和超声波波速的水库底泥透水混凝土性能研究

水库中的黏土、砂、有机物和无机矿物等结合并沉淀形成了水库底泥,水库底泥通常以不规则非均质体的黏土胶状物存在,呈流塑状态,具有良好的可塑性,颗粒之间较为松散。水库底泥的堆积会使水库的蓄水和防洪能力减弱,进而缩小水库容量,缩短水库寿命,影响航运交通等。另外水库底泥的长久堆积,其所含有的有机物还可能会对周边环境造成污染,水环境安全指数降低,进而对人类生存构成潜在的威胁,因此迫切需要对水库底泥进行资源化利用。为提高水库底泥在建筑材料领域的附加值利用率,将水库底泥作辅助胶凝材料制备透水混凝土。通过正交试验对水库底泥透水混凝土进行配合比设计优化研究,分析矿渣粉、水库底泥和增强剂对水库底泥透水混凝土干密度、总孔隙率、有效孔隙率、透水系数、超声波波速和28 d抗压强度等性能指标的影响,研究超声波波速与孔隙率、透水系数和28 d抗压强度之间的关系,探究试件的质量和超声波波速随冻融循环次数的演化规律。结果表明,随着水库底泥的掺入,水库底泥透水混凝土的干密度、抗压强度和超声波波速不断下降,孔隙率和透水系数不断增大;矿渣粉掺入使得试件的干密度、抗压强度和超声波波速先增大后减小,孔隙率和透水系数先减小后增大;增强剂对试件的性能指标影响不明显。3种因素对水库底泥透水混凝土的干密度、总孔隙率、有效空隙率、透水系数、超声波波速和28 d抗压强度影响排序为水库底泥掺量>矿渣粉掺量>增强剂掺量;超声波波速与孔隙率、透水系数和28 d抗压强度的曲线拟合相关性良好;随着冻融循环次数增加,试件质量损失率逐渐增大、超声波波速逐渐下降,矿渣粉和增强剂可以改善试件的冻融耐久性。研究成果将推进水库底泥在制备建筑材料中的开发与应用,有望为水库底泥透水混凝土的进一步应用提供参考。

Rainbow Trout (<i>Oncorhynchus mykiss</i>) Cage Culture: Preliminary Observations of Surface Sediment’s Chemical Parameters and Phosphorus Release in Gokcekaya Reservoir, Turkey

This research was conducted in Gokcekaya Reservoir, which is located on the Sakarya River (Ankara, Turkey). Sediment samples were obtained before and after culture periods at a rainbow trout (Oncorhynchus mykiss) farm with a capacity of 950 t·y-1. Total phosphorus (TP: 8.80 ± 0.50 and 9.10% ± 0.20%), total nitrogen (TN: 17.0 ± 0.20 and 17.05% ± 0.10%), organic matter (OM: 14.40 ± 0.40 and 14.60% ± 0.20%), redox potential (327.00 ± 0.08 and 170.00 ± 4.08 mV), water content (97.68 ± 0.28 and 96.38% ± 0.41%) and total organic carbon (TOC: 11.30 ± 0.10 and 13.40% ± 0.10%) were measured before and after the culture period, respectively. The mean rank order of sediment heavy metal was evaluated as Fe > Mn > Ni > Zn > Cr > Cu. The soluble reactive phosphorus (SRP) concentrations in the sediment pore water were 2.52 ± 0.14 and 7.75 ± 1.18 μg·L-1;ammonium (NH3) was measured as 1.13 ± 0.09 and 1.18 ± 0.06 μg·L-1;nitrite (NO2) was 8.83 ± 0.23, 12.75 ± 0.22 μg·L-1;nitrate (NO3) was elevated at 0.14 ± 0.07 and 0.24 ± 0.02 μg·L-1, and positive phosphorus release remained at low levels: 3.35 μg&#183m-2d-1 (before the culture period, September 2011) and 11.04 μg·m-2d-1 (after the culture period, April 2012). The data on the sediment and the sediment pore water of the rainbow trout culture in Gokcekaya Reservoir shows that the cage culture in its present condition has no negative effect on sediment quality.

Dukan Dam Reservoir Bed Sediment, Kurdistan Region, Iraq

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 multi-purpose 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 km2. The surface area of the reservoir is 270 square kilometers and the volume is 6.870 × 106 m3 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 m3 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.