三峡库区万州区段长江水中泥沙量对其水质的影响分析

长江三峡库区的生态环境及水质情况。随着三峡工程建设的不断深入而备受社会各界的瞩目。重庆市万州区地处三峡水库腹心地带。长江自西南向东北横穿万州区全境。过境流程83公里。万州区溪流纵横。水网密布，多数河流直接排入长江。而且在三峡库区大移民进程中有大量的移民集中在万州。在三峡大坝即将合龙之际，研究长江万州流域的水质情况无疑对指导库区的清理工作、生态环境建设等具有重大意义。本文对该地区的水污染源进行了初步考察。同时对万州区段长江流域的水质进行了探索性研究。发现该区水土流失情况较为严重，而且水中的泥沙含量与其COD水平有相关关系。江水中大部分的COD是由泥沙携带的有机物的贡献。     

Upstream Sediment‐Control Dams: Five Decades of Experience in the Rapidly Eroding Dahan River Basin,Taiwan

Sedimentation is emerging as a key issue in sustainable reservoir management. One approach to controlling reservoir sedimentation is to trap sediment in hydraulic structures upstream of the reservoir. In the 1,163‐km² catchment of the Dahan River (Taiwan) over 120 “sabo” dams were built to reduce sediment yield to Shihmen Reservoir. Built in 1963 for water supply, Shihmen has lost over 40% of its 290‐Mm³ storage capacity to sedimentation. Most of these upstream structures were small, but three had capacities >9 Mm³. Field measurements and historical data from the Water Resources Agency show most smaller dams had filled with sediment by 1976. The three largest were full or nearly so by 2007, when one (Barlin Dam) failed, releasing a pulse of 7.5 Mm³, most of its 10.4 Mm³ stored sediment downstream. The Central Range of Taiwan is rapidly eroding (denudation rates 3‐6 mm/yr), so geologically high loads make sediment problems manifest sooner. Even in other environments, however, eventually small dams built upstream of large reservoirs are likely to fill themselves, creating multiple small sediment‐filled reservoirs, some located in sites inaccessible to mechanical removal. Our analysis suggests sabo dams do not offer a long‐term basis for controlling reservoir sedimentation in such a high‐sediment yield environment. Sustainable solutions must somehow pass sediment downstream, as would be accomplished by a sediment bypass around Shihmen Reservoir, as now being studied.     

Sourcing sediment using multiple tracers in the catchment of Lake Argyle,Northwestern Australia

Control of sedimentation in large reservoirs requires soil conservation at the catchment scale. In large, heterogeneous catchments, soil conservation planning needs to be based on sound information, and set within the framework of a sediment budget to ensure that all of the potentially significant sources and sinks are considered. The major sources of sediment reaching the reservoir, Lake Argyle, in tropical northwestern Australia, have been determined by combining measured sediment fluxes in rivers with spatial tracer-based estimates of proportional contributions from tributaries of the main stream entering the lake, the Ord River. The spatial tracers used are mineral particle magnetics, the strontium isotopic ratio, and the neodymium isotopic ratio. Fallout of ¹³⁷Cs has been used to estimate the proportion of the sediment in Lake Argyle eroded from surface soils by sheet and rill erosion, and, by difference, the proportion eroded from subsurface soils by gully and channel erosion. About 96% of the sediment in the reservoir has come from less than 10% of the catchment, in the area of highly erodible soils formed on Cambrian-age sedimentary rocks. About 80% of the sediment in the reservoir has come from gully and channel erosion. A major catchment revegetation program, designed to slow sedimentation in the reservoir, appears to have had little effect because it did not target gullies, the major source of sediment. Had knowledge of the sediment budget been available before the revegetation program was designed, an entirely different approach would have been taken.     

三峡库区消落带土壤中重金属铬调查与分析

报道了三峡库区长江干流及小江支流消落带土壤重金属铬含量背景值调查结果。结果表明目前土壤未被重金属铬污染。     

MULTISCALE INFLUENCES ON PHYSICAL AND CHEMICAL STREAM CONDITIONS ACROSS BLUE RIDGE LANDSCAPES1

ABSTRACT: Streams integrate biogeochemical processes operating at broad to local spatial scales and long term to short term time scales. Humans have extensively altered those processes in North America, with serious consequences for aquatic ecosystems. We collected data on Upper Tennessee River tributaries in North Carolina to: (1) compare landuse and landscape geomorphology with respect to their ability to explain variation in water quality, sedimentation measures, and large woody debris; (2) determine if landscape change over time contributed significantly to explaining present stream conditions; and (3) assess the importance of spatial scale in examining landuse influences on streams. Stream variables were related to both landuse and landscape geomorphology. Forest cover accounted for the most variation in nearly all models, supporting predictions of nutrient enrichment, thermal pollution, and sedimentation caused by landscape disturbance. Legacy effects from past catchment disturbance were apparent in sedimentation measures. Nitrogen and phosphorus concentrations, as well as stream temperature, were lower where riparian buffers had reforested. Models of stream physicochemistry fit better when predictors were catchment wide rather than more localized (i.e., within 2 km of a site). Cumulative impacts to streams due to changes in landuse must be managed from a watershed perspective with quantitative models that integrate across scales.     

Environmentally sensitive plot-scale timber harvesting: impacts on suspended sediment, bedload and bank erosion dynamics

The impact on sediment pollution of environmentally sensitive harvesting of a 15 ha plot (20% of the catchment area) of mature coniferous plantation forest in the 0.89 km2 Afon Tanllwyth catchment, Plynlimon, was investigated for 12 months before harvesting began and a further 18 months after. The results revealed: (a) a steepening of the suspended sediment concentration vs. discharge rating curve resulting in a 39% increase in suspended sediment yield (as compared to the adjacent forested Hafren catchment) during the year in which the harvesting operations took place; (b) a statistically significant increase in main channel bank erosion rates, as compared with the nearby Afon Cyff; main channel banks are estimated to have contributed around 80% of the total catchment suspended sediment yield during the two year period (1995-1996), and (c) no significant change in bedload yields over the duration of the study, though a longer post-harvesting time series of bedload data will be required to properly assess the impact of the harvesting operation upon bedload yields. Forest management implications of these findings are discussed in detail with respect to the existing Forest and Water guidelines.     

INTEGRATED ECHO SOUNDER,GPS, AND GIS FOR RESERVOIR SEDIMENTATION STUDIES: EXAMPLES FROM TWO ARKANSAS LAKES1

ABSTRACT: Bathymetric and sedimentation surveys were conducted using a dual frequency (28/200 kHz) echo sounder system in two reservoirs (Lee Creek Reservoir and Lake Shepherd Springs) in the Ozark Plateau of northwestern Arkansas. Echo sounder survey data were merged within geographic information system (GIS) software to provide detailed visualization and analyses of current depths, pre‐impoundment topography, distribution, thickness, and volume estimates of lacustrine sediment, time averaged sediment accumulation rates, long term average annual sediment flux, and water storage capacity. Calculated long term average sediment accumulation rates were used to model sediment infilling and projected lifetimes of each reservoir. Results from echo sounder surveys and GIS analyses suggest that the Lee Creek Reservoir has a projected lifetime of approximately 500 years compared to a projected lifetime for Lake Shepherd Springs of approximately 3,000 years. Estimated differences in projected lifetimes of these reservoirs reflected differences in initial reservoir volume and long term average annual sediment flux from the respective watersheds related to watershed area, physiography, land cover, and land use. The universal soil loss equation (USLE) model generated sediment fluxes an order of magnitude larger from the watersheds of both reservoirs compared to the geophysical data estimates. This study demonstrated the utility of merging geophysical survey (echo sounder) data within a GIS as an aid to understanding patterns of reservoir sedimentation. These data and analyses also provide a baseline relevant to understanding sedimentation processes and are necessary for development of long term management plans for these reservoirs and their watersheds.     

重庆三峡库区饮用水安全存在的问题与对策研究

饮用水源的污染以及常规的水处理工艺去除污染的局限性等原因，使库区人民健康正面临日益严重的威胁。结合三峡库区特殊的自然条件和社会经济发展水平，本文分析了库区饮用水安全存在的问题，并提出供水水质安全保障对策，即加强水污染控制，保护水源安全；采用先进、适用的净水技术；控制生活饮用水的二次污染，为库区构建新型的安全饮用水保障体系。     

2001-2010年三峡库区（重庆段）相对资源承载力时空格局动态演变研究

运用相对资源承载力理论,并结合库区实际扩展了传统指标体系,改进了权重算法,研究了2001-2010年三峡库区（重庆段）自然资源、经济资源、生活水平的相对承载力与综合承载力的时空动态演变过程.研究表明：①近10年,三峡库区（重庆段）综合承载力偏低,人口严重超载.②随着库区经济社会的快速发展,自然资源承载力严重不足.③库区相对资源承载力空间差异显著.研究结果对把握库区资源承载力变化规律和空间分异特征具有重要意义,同时为三峡库区控制人口数量、调整人口分布,合理有效配置资源提供科学依据.     

The effect of Oja-titun market effluent on the chemical quality of receiving OPA reservoir in Ile-Ife, Nigeria

The effect of market effluent from the Oja-titun market in Ile-Ife, Nigeria on the chemical quality of the Opa Reservoir located 3.5 km downstream was investigated between February and November 2000. Water samples were collected in February, May, August and November from 16 sites, four along each of the market drainage channels (MDC), market stream, tributary stream and the Opa River and Reservoir. The peak level of each variable-biochemical oxygen demand, temperature, total alkalinity, Na(+), K(+), Ca(2+), Mg(2+), PO(4)(3+), SO(4)(2+), Cl(-), NO(3)(-), Pb and Zn-occurred at the MDC, and decreased significantly downstream, except pH, conductivity and dissolved oxygen, which increased. Seasonal fluctuation in most variables was pronounced. Generally, there were high values in the early dry and dry seasons and low values in the rainy and early rainy seasons. Comparison of the reservoir water with international limitation standards for drinking water supply showed that the quality of the reservoir water was very low and that treatment required to achieve minimum limitation standards for drinking water would be both intensive and expensive. The study concluded that the stream borne effluent from the market impacts significantly on the chemical quality of the reservoir water although other tributaries within the Reservoir's catchment are other possible sources of pollutants in the reservoir.     

A NEW METHOD FOR ESTIMATING FUTURE RESERVOIR STORAGE CAPACITIES1

ABSTRACT: A new method has been developed for estimating future reservoir storage capacities, allowing for sediment deposition and compaction. Reservoir sedimentation surveys for 117 reservoirs, conducted by the Illinois State Water Survey over the past 60 years, were used to determine regional constants K to represent the severity of sediment deposition in the reservoirs. More than half of the 82 water supply reservoirs investigated had records of reservoir sedimentation surveys, and their K values were calculated by using data from those sediment surveys. The average K values of the remaining non-surveyed water supply reservoirs were estimated from the regional distribution of the K values. Other important factors considered in the estimation of future reservoir storage capacities are the trap efficiency of the reservoirs and the variation of density of sediment deposits due to compaction. The model can also be used for analyzing the economics of alternative sites and of design features that can be incorporated in dams for reducing reservoir sedimentation.     

Cost/Benefit Considerations for Recent Saltcedar Control,Middle Pecos River,New Mexico

Major benefits were weighed against major costs associated with recent saltcedar control efforts along the Middle Pecos River, New Mexico. The area of study was restricted to both sides of the channel and excluded tributaries along the 370 km between Sumner and Brantley dams. Direct costs (helicopter spraying, dead tree removal, and revegetation) within the study area were estimated to be $2.2 million but possibly rising to $6.4 million with the adoption of an aggressive revegetation program. Indirect costs associated with increased potential for erosion and reservoir sedimentation would raise the costs due to increased evaporation from more extensive shallows in the Pecos River as it enters Brantley Reservoir. Actions such as dredging are unlikely given the conservative amount of sediment calculated (about 1% of the reservoir pool). The potential for water salvage was identified as the only tangible benefit likely to be realized under the current control strategy. Estimates of evapotranspiration (ET) using Landsat TM data allowed estimation of potential water salvage as the difference in ET before and after treatment, an amount totaling 7.41 million m³ (6010 acre-ft) per year. Previous saltcedar control efforts of roughly the same magnitude found that salvaged ET recharged groundwater and no additional flows were realized within the river. Thus, the value of this recharge is probably less than the lowest value quoted for actual in-channel flow, and estimated to be < $63,000 per year. Though couched in terms of costs and benefits, this paper is focused on what can be considered the key trade-off under a complete eradication strategy: water salvage vs. erosion and sedimentation. It differs from previous efforts by focusing on evaluating the impacts of actual control efforts within a specific system. Total costs (direct plus potential indirect) far outweighed benefits in this simple comparison and are expected to be ongoing. Problems induced by saltcedar control may permanently reduce reservoir capacity and increase reservoir evaporation rates, which could further deplete supplies on this water short system. These potential negative consequences highlight that such costs and benefits need to be considered before initiating extensive saltcedar control programs on river systems of the western United States.     

HYDRODYNAMIC MODELING OF THE CARSON RIVER AND LAHONTAN RESERVOIR,NEVADA1

ABSTRACT: The RIVMOD hydrodynamic model was used to route upstream flows through a 115 km section of the Carson River and Lahontan Reservoir, Nevada. RIVMOD results will later be used to predict sediment movement and ultimately to determine mercury transport within the river/reservoir system. Significant modifications to the model computer code were necessary to represent the narrow, steeply sloping rectangular channel and relatively shallow sloping floodplain of the Carson River and its confluence with the Lahontan Reservoir. These changes include expansion of the continuity and momentum equations to account for rapidly changing channel widths along with the characterization of a complex cross-sectional shape. This modified version of the RIVMOD model can handle shallower side slopes and much more severe flood flow simulations than the original version. A 0.25 km spatial increment was required in the zone of confluence between the river and reservoir. Model predictions show excellent agreement with observed downstream flow and reservoir stage for the entire 1986 water year, which includes one of the most severe flood events of recent record. (KEY TERMS: hydraulics; modeling; simulation; surface water hydrology.)     

金沙江流域水土流失与人类活动影响分析

长江三峡水利枢纽工程能否正常发挥效益，泥沙是重要的制约因素之一，而水库的泥沙主要来自上游金沙江，其多年平均输沙量占入库寸滩站的５２７％。因此，本文对金沙江泥沙的地区组成、水土流失及人类活动影响等问题进行了深入的分析，并提出了防治对策。     

三峡库区典型次级支流表层沉积物中PAHs的分布特征及来源分析

本文表征了三峡库区典型次级支流(梁滩河)表层沉积物中18种多环芳烃(PAHs)的浓度,并对其分布特征和污染来源进行了探讨。18种PAHs的总浓度(∑18 PAHs)范围为198.5～4349 ng/g-dw(干重),平均浓度为1441ng/g,中值为1160 ng/g。与其他地区沉积物污染情况相比,梁滩河沉积物中PAHs浓度处于中等偏低的污染程度,支流污染程显著高于干流,流经城镇的右支污染程度显著高于流经农村或人口较少的左支和主干流。大部分采样点以高环(4～6环)PAHs污染为主。PAHs源解析结果表明,梁滩河表层沉积物中PAHs污染以燃烧源为主,主要源于化石燃料和生物质的不完全燃烧。沉积物中苯并[a]芘的毒性当量因子(TEF)值为39.38～384.37 ngTEQ/g,平均值110.94 ngTEQ/g。生态风险评价的结果表明,右支流的两个采样点R3和R4点沉积物中PAHs可能存在生物负效应影响,R4点的高风险可能与附近白市驿机场污染有关。     

Modeling Monthly Fluctuations in Submersion Area of a Dammed River Reservoir: A Case Study1

Lu, Haorong, S. Samuel Li, and Jinsong Guo, 2012. Modeling Monthly Fluctuations in Submersion Area of a Dammed River Reservoir: A Case Study. Journal of the American Water Resources Association (JAWRA) 1‐13. DOI: 10.1111/jawr.12003 Abstract: Fluctuations in water submersion of the Three Gorges Reservoir in China have not been explored in spite of their important implications for shoreline erosion and other undesirable consequences. This article aims to quantify the monthly fluctuations in response to changing hydraulic parameters and regional climatic factors. Flow velocity and water levels distributed along the 609‐km long dammed river reservoir are calculated with a one‐dimensional hydrodynamics model. Evaporation of water from the surface of the reservoir is determined using mass transfer‐based methods. Calculated flow velocities and water levels compare well with field data. We show that the water surface slope decreases with rising water level at the dam, and decreases to almost zero during the winter months of water storage when the downstream water level reaches the normal pool level. The submersion area varies between 830 and 1,070 km² over the year or over 20% of the reservoir zone will experience the annual cycle of dry land and partial or complete submersion. These fluctuations are of relevance to shoreline management and to the prevention and restoration of shoreline erosion. Evaporation is estimated to fluctuate between 1,240 and 26,110 tons of water per month per kilometer length of reservoir channel; this can possibly affect the hydrological budget of the reservoir region. The simple methodologies discussed in this article can easily be applied to other dammed river reservoirs for submersion estimates.     

ASSESSMENT USING GIS AND SEDIMENT ROUTING OF THE PROPOSED REMOVAL OF BALLVILLE DAM,SANDUSKY RIVER,OHIO1

ABSTRACT: The proposed removal of Ballville Dam was assessed by (1) using a new Geographic Information Systems (GIS) based method for calculating reservoir sediment storage, (2) evaluating sediment properties and contamination from core data, and (3) assessing downstream impacts from sediment routing calculations. A 1903 (pre‐dam) map was manipulated using GIS to recreate the reservoir bathymetry at time of dam construction and used in combination with a detailed 1993 bathymetric survey to calculate sediment volumes and thickness. Reservoir sediment properties and geochemistry were determined from 14 sediment vibracores. Annual sedimentation rates varied from 1.7 to 4.3 g/cm²/yr based on Cesium‐137 (¹³⁷Cs) and Lead‐210 (²¹⁰Pb) geochronology and dated flood layers. The pore fluid geochemistry (Ba, Co, Cu, Mn) of four cores showed surficial enrichments in Cu, while Co and Mn show secondary peaks within the sediments. GIS calculations showed that a designed channel through the former reservoir able to accommodate the 10 percent Probable Maximum Flood (PMF) would require removing approximately 0.35 million m³ of sediment (27 percent of the reservoir fill), either by dredging at a cost of up to $6.3 million or by releasing fine grained sediment downstream. A sediment routing model was applied for the critical 6 km downstream using four cross sections. The sediment routing model predicts that, for flows exceeding minimum Mean Daily Flow (1924 to 1998 data), greater than 90 percent of this sediment would be transported through downstream reaches into Lake Erie (Sandusky Bay).     

RESERVOIR SEDIMENTATION RATES LINKED TO LONG-TERM CHANGES IN AGRICULTURAL LANI) USE1

ABSTRACT: Long-term land use and reservoir sedimentation were quantified and linked in a small agricultural reservoir-watershed system without having historical data. Land use was determined from a time sequence of aerial photographs, and reservoir sedimentation was determined from cores with ¹³⁷Cs dating techniques. They were linked by relating sediment deposition to potential sediment production which was determined by the Universal Soil Loss Equation and by SCS estimates for gullied land. Sediment cores were collected from Tecumseh Lake, a 55-ha reservoir with a 1,189-ha agricultural watershed, constructed in 1934 in central Oklahoma. Reservoir sediment deposition decreased from an average of 5,933 Mg/yr from 1934 to 1954, to 3,179 Mg/yr from 1954 to 1962, and finally to 1,017 Mg/yr from 1962 to 1987. Potential sediment production decreased from an average of 29,892 to 11,122 and then to 3,589 Mg/yr for the same time periods as above, respectively. Reductions in deposition and sediment production corresponded to reductions in cultivated and abandoned cropland which became perennial pasture. Together, cultivated and abandoned cropland accounted for 59 percent of the watershed in 1937, 24 percent in 1954, and 10 percent in 1962. Roadway erosion, stream bank erosion, stored stream channel sediment, and long-term precipitation were considered, but none seemed to play a significant role in changing sediment deposition rates. Instead, the dominant factor was the conversion of fields to perennial pastures. The effect of conservation measures on reservoir sedimentation can now be quantified for many reservoirs where historical data is not available.     

四川省出川断面主要污染物通量及来源研究

以2001～2007年实测水文、水质数据为基础,计算了四川省主要出川断面高锰酸盐指数(CODMn)和氨氮(NH3-N)污染负荷通量;利用断面水质目标约束,通过污染负荷历时曲线,分析了区域水环境承载力;在基流分割的基础上,利用水文分割法,识别了区域污染物的主要来源,为从源头上开展三峡水库水环境保护提供数据支撑。分析结果表明,各出川断面干流主要污染物(CODMn、NH3-N)大致在可接受的范围内,2001年以来,出川断面CODMn通量呈降低的趋势,有效的减缓了输入三峡库区的污染物总量,氨氮通量整体稳定。嘉陵江、涪江、渠江流域污染物来源主要为非点源,应重点加强面源的污染防控;长江干流为点面源混合型,简单的削减点源已不能保证高功能水体要求,应加强点源和面源污染的综合防控。     

RESERVOIR SEDIMENTATION AS A FUNCTION OF PRECIPITATION VARIABILITY1

ABSTRACT: This research examines what is hypothesized as a critical factor in reservoir sedimentation - precipitation variability. The coefficient of variation for annual precipitation, computed for the period relating to sedimentation, is regressed against sediment yields for several reservoirs over a wide range of environmental settings. A significant linear relationship results, and when precipitation variability is combined with several additional variables available from reservoir summary sheets, almost 83% of the total variation in sediment yield is accounted for. It is suggested that the coefficient of variation for annual precipitation fulfills a direct process role when modeling reservoir sedimentation much more effectively than annual precipitation or runoff.