Bank‐derived material dominates fluvial sediment in a suburban Chesapeake Bay watershed

Excess fine sediment is a leading cause of ecological degradation within the Chesapeake Bay watershed. To effectively target sediment mitigation measures, it is necessary to identify and quantify the delivery of sediment sources to local waterbodies. This study examines the contributions of sediment sources within Upper Difficult Run, a suburbanized watershed in Fairfax County, Virginia. A source sediment library was constructed from stream banks, forest soils, and road dust. Target sediments were collected from fine channel deposits and suspended sediment during 16 storm events from 2008 to 2012. Apportionment of targets to sources was performed using Sed_SAT, a publicly available toolkit for sediment fingerprinting. Bed sediment was dominated by stream bank material (mean: 98%), with minor contributions from forests (2%). Suspended fine sediments were also dominated by stream banks (suspended sediment concentration‐weighted mean: 91%), with minor contributions from roads (8%) and forests (<1%). Stream banks dominated at all discharges, and on the rising limb and at peak flow, sediment concentrations increased due to bank material rather than surface erosion. Sediment budget data indicated that direct bank erosion was insufficient to account for the suspended load derived from stream banks. However, bank‐derived sediment re‐mobilized from in‐channel storage could account for this difference and, combined, resulted in a sediment delivery ratio of 0.847 for all bank‐derived sediments. Results demonstrate that stream bank erosion is responsible for the majority of fine sediment in this suburban watershed of the Chesapeake Bay drainage area. Thus, management actions to control upland sources of sediment may have limited effect on the sediment conditions of Upper Difficult Run, whereas efforts focusing on bank stabilization, channel restoration, and/or stormwater management to reduce bank erosion may improve the ecological condition of these waterbodies.     

水库排沙对下游河流鱼类影响研究进展

水库排沙对减轻水库淤积、延长水库寿命和恢复河流泥沙连续性等方面有着重要意义,但是水库进行水力排沙时水库下游河流水体的物理和化学性质的变化可能对鱼类等水生生物产生不利影响,严重时出现死鱼现象.国内外水库排沙时期下游河道含沙量及其颗粒级配、溶解氧浓度、污染物等水质变化对鱼类影响研究表明,微颗粒泥沙淤堵鱼鳃影响其摄入氧气功能和水体溶解氧下降是影响鱼类的两个主要因素,且含沙量及其持续时间、颗粒级配等对鱼类影响机理不同.最后展望了我国今后水库排沙对下游河流鱼类研究内容.     

Spatio‐temporal variability of suspended sediments in rivers and ecological implications of reservoir flushing operations

High suspended sediment concentrations during reservoir flushing are known to be harmful to biota in downstream river stretches. Therefore, it is common practice to set legal concentration limits for upstream reservoir management operations such as flushings or controlled drawdowns. However, as shown by measurements, there is a considerable spatio‐temporal variability of suspended sediment concentrations both in the longitudinal profile of rivers and in river cross‐sections. To consider this variability in management operations, SED‐FISH—a three‐dimensional modelling approach—was developed to study this variability in a wider context by upscaling cross‐sectional measurements of suspended sediments to high‐resolution three‐dimensional information on the reach scale in an alpine river. The resulting patterns of suspended sediment concentrations were integrated over their respective time of occurrence for various scenarios in order to calculate severity of harmful impacts for target fish species. The modelling results identified refugial habitats with reduced negative impacts in near‐bank zones even for relatively high suspended sediment concentrations in the centre of the river. Moreover, a substantially larger variability of both suspended sediment concentrations and associated harmful impacts was found for a winding riverbed morphology as compared with a straight reach. Both these findings and the developed modelling tool could assist in establishing individual case‐based concentration limits for reservoir management operations in the future and should also be taken into account when planning river regulation or restoration measures.     

Assessing macroinvertebrate community response to restoration of Big Spring Run: Expanded analysis of before‐after‐control‐impact sampling designs

Stream restoration projects utilize a variety of approaches to improve conditions for aquatic organisms or enhance ecosystem function. Alterations to abiotic conditions to enhance certain ecosystems services may not lead to concurrent changes in the benthic macroinvertebrate community indicative of improved stream health. Big Spring Run was the location of a novel restoration project to recreate an anabranching “wet meadow” habitat typical of precolonization conditions without the primary goal of restoring a macroinvertebrate community characteristic of single‐channel lotic systems. We examined the effect of the restoration on the macroinvertebrate community using a multivariate analysis of assemblage composition, a before‐after‐control‐impact (BACI) approach, and an assessment of potential aerial migrants. We also examined subsets of the data using a BACI approach that represented restricted sampling designs often employed in stream restoration projects. Benthic macroinvertebrates were collected in the Spring twice prior to restoration (2010 and 2011) and 3 years after restoration (2012–2014). Adult stream insects were collected in 2014. Analyses of benthic macroinvertebrates and adult insects using the full dataset suggested that restoration had no effect on the macroinvertebrate community due to poor in‐stream conditions likely from sediment deposition following restoration. Dispersal barriers are likely acting as a secondary constraint on recolonization. Analyses using subsets of the data demonstrated that reference site quality and sampling extent can alter conclusions from a BACI approach. We found that a holistic approach using multiple lines of evidence required a nuanced approach to interpreting the data but was also informative for assessing project success. Robust monitoring protocols are likely the best approach for producing convincing results through a single line of evidence. The additional BACI analyses performed for this study, however, allowed the modest sampling regime employed to generate a broad narrative demonstrating that the macroinvertebrate assemblage did not respond to this type of restoration. Thus, we believe the holistic approach we employed can strengthen assessments of stream restoration projects when resources for monitoring are limited.     

Nature‐like fishways as compensatory lotic habitats

Damming of rivers disrupts migration of fish and results in lotic habitats being both scarcer and spaced further apart, ultimately affecting riverine fish communities. Nature‐like fishways are often designed as bypass channels, constructed with natural materials that reroute part of the water around weirs and dams, restoring longitudinal connectivity as well as forming nature‐mimicking habitats. We evaluated the potential of such bypasses to function as compensatory lotic habitats by comparing fish fauna in 23 bypasses to adjacent lotic stream habitats in a same‐river pairwise design. Bypasses were narrower, shallower, and less shaded than adjacent stream habitats, but very few significant differences could be detected in the fish communities, indicating the potential of such nature‐like fishways to constitute compensatory lotic habitats for fish. Analyses also indicated how bypass design may be altered to favour or disfavour certain target species. Generally, narrower and shallower bypasses with high gradient favoured brown trout (Salmo trutta), whereas European eel (Anguilla anguilla) were more abundant at sites with lower gradient. Finally, to increase the impact of these compensatory habitats on running water ecosystems, we suggest that the size of bypasses should be maximized in areas where natural stream habitats have been lost.     

Effects of projected climate on the hydrodynamic and sediment transport regime of the lower Athabasca River in Alberta,Canada

The potential effects of climate change on the hydrodynamic and sediment transport regime of the lower Athabasca River (LAR) in Alberta, Canada, is investigated. Future climate projections for the region suggest a potential increase in mean air temperature and precipitation by about 2.8–7.1 °C and 8–25%, respectively, by the end of this century. Implications of these climatic changes on the hydrologic regime of the LAR are found to be significant with spring flows expected to increase by about 11–62% and 26–71% by the end of the century for a moderate and high emissions scenarios respectively with corresponding decreases in summer flows. The effects of such changes are examined using the MIKE‐11 hydrodynamic and sediment transport modelling system with inflow boundary conditions corresponding to the changing hydro‐climatic regime. The results suggest that there will be an overall increase in flow velocity, water level, and suspended sediment concentration and transport for most seasons except in the summer months when there may be some decreases. The projected changes in suspended sediment concentration will result in an overall increase in mean annual sediment load in the LAR and to the Peace Athabasca Delta by over 50% towards the latter part of this century (2080s) compared with the 1980s base‐line period. Implications of such potential changes in the transport characteristics of the river system to the mobilization and transport of various chemical constituents and their effects on the region's aquatic ecosystems are subjects of other ongoing investigations.     

Geomorphic applications of stream‐gage information

In the United States, several thousand stream gages provide what typically is the only source of continuous, long‐term streamflow and channel‐geometry information for the locations being monitored. In this paper, the geomorphic content of stream‐gage information, previous and potential applications of stream‐gage information in fluvial geomorphic research and various possible limitations are described. Documented applications include studies of hydraulic geometry, channel bankfull characteristics, sediment transport and channel geomorphic response to various types of disturbance. Potential applications include studies to determine the geomorphic effectiveness of large floods and in‐stream habitat change in response to disturbance. For certain applications, various spatial, temporal and data limitations may render the stream‐gage information of limited use; however, such information often is of considerable value to enable or enhance geomorphic investigations. Published in 2008 by John Wiley & Sons, Ltd.     

Suspended sediment load estimation in an ungauged river in south‐eastern Australia

Soil erosion poses a significant threat to river health as well as the sustainability of soil resources. Management of this issue requires catchment‐specific data to be developed; however, many large catchments are poor in terms of hydrological and sediment transport data. Regional scale (thousands of square kilometres), computer‐based modelling methods are a way to generate such data. This study aims to apply the SedNet model to estimate a sediment budget for a 575 km², ungauged, agricultural catchment of south‐eastern Australia. The model results are then compared with field measured erosion rates for the catchment, in order to assess the sustainability of soil loss and redistribution across the catchment. SedNet estimated average suspended sediment concentrations between 70 and 120 mg/L, under conditions deemed most representative of the river. These model estimates were comparable with monitoring data, showing suspended sediment concentrations between 30 and 350 mg/L. It was found that soil loss and redistribution across the catchment is low; however, the estimated base sediment loads indicate that river health may be negatively impacted by this. SedNet accurately represented current catchment and river conditions and provided a reliable estimation of sediment yield, demonstrating the ability to estimate sediment loss and redistribution across data‐poor catchments using a multifaceted modelling approach. Methodologies, such as the one presented here, offer the ability to better assess the impacts of erosion on sediment loads to develop strategies to effectively manage excess suspended sediment.     

Trait‐based responses of Ephemeroptera,Plecoptera, and Trichoptera to sediment stress in the Tsitsa River and its tributaries,Eastern Cape,South Africa

Elevated instream fine sediment is one of the most important water quality stressors affecting both the structure and function of aquatic ecosystems. This study evaluates whether a predictable pattern of trait distribution of Ephemeroptera, Plecoptera, and Trichoptera (EPT) can be observed along a gradient of sediment stress in eight selected sites in the Tsitsa River and its tributaries. The sites were classified into four site groups according to their fine sediment loads. One‐way analysis of variance was used to test differences in the relative abundance of traits across the site groups. A predictable pattern was observed in 13 of the 27 trait attributes tested, with most traits displaying low abundances in highly disturbed site groups. The relationship between EPT traits and fine sediment stress was analysed using the multivariate RLQ analysis, and the result showed that traits such as swimming, shredding, operculate gill, small body size, and sclerotized body were the dominant traits in the sediment influenced site groups. In the less disturbed site groups, filter feeding, crawling, filamentous gill, soft and exposed body, and large body size were the dominant trait attributes. These observed relationships between EPT traits and sediment stress provide support for the potential usefulness of EPT traits as indicators of fine sediment stress in riverine ecosystems.     

ADJUSTMENT OF PRAIRIE POTHOLE STREAMS TO LAND‐USE,DRAINAGE AND CLIMATE CHANGES AND CONSEQUENCES FOR TURBIDITY IMPAIRMENT

Changes in land use and drainage have contributed to channel adjustment in small‐order to medium‐order streams in the prairie pothole region of south‐west Minnesota. Although conversion from prairie to agriculture occurred a century ago, recent decades have seen increased subsurface tile drainage, annual row crop coverage and channel modifications, particularly at road crossings such that channel adjustment is ongoing. Channel evolution in Elm and Center Creeks, two fourth‐order streams in the Blue Earth River basin, was studied to understand relationships between changes in channel morphology and suspended sediment concentrations. The construction of drainage ditches and expanded subsurface tiling has connected isolated basins to stream channels, effectively increasing drainage areas of Elm and Center Creeks by 15–20%. Sinuosity has been reduced by grading and drainage of first‐order sloughs, channel straightening at road crossings and natural cut‐offs and agricultural ditching that have shortened Elm Creek by 15% between 1938 and 2003. Stream cross‐sectional area was enlarged in response to the land‐use and drainage changes. In the headwaters, public ditches are wider than historic channels and entrenched by berms. Unchannelized headwater and upper mainstem portions of Elm Creek are also highly entrenched (up to 1.07 meters below the pre‐channelization bed elevation with a bank height ratio > 1.5) but have not widened substantially. In contrast, the lower main channel has widened by an average of 68%. These channel adjustments contribute to the suspended sediment load and violations of Minnesota's turbidity and Index of Biotic Integrity standards. The watershed has a low sediment delivery ratio because it is a flat, poorly connected landscape and likely delivers less sediment to the Minnesota River than steeper rivers downstream, such as the Blue Earth River. Entrenchment and increased sediment transport capacity in the lower reaches of the river have lead to increased sediment delivery to the downstream Blue Earth and Minnesota rivers. Understanding geomorphic changes will be important for addressing water‐quality impairments in the region. Copyright © 2011 John Wiley & Sons, Ltd.     

Multi‐annual contemporary flood event overbank sedimentation within the vegetated lower Orinoco floodplain,Venezuela

Multi‐annual contemporary flood event overbank sedimentation rates were quantified on the World's third largest river in terms of discharge, the tropical lower Orinoco. We discuss the role of variables at the basin and reach scales that contributed to the complexity of spatio‐temporal overbank sediment deposition patterns. Monitored in situ plots were characterized by distance to the main channel, hydroperiod, different geomorphological units, and vegetation cover. Flood event sedimentation rates showed a high spatial variability ranging from the absence of sediment deposition up to 225.46 kg m^‐2 yr^‐1. Banks and levees received relatively high amounts of sediment (39.6 kg m^‐2 yr^‐1), whereas observed mean sedimentation rates on the more distant floodplain and backswamps tended to be lower (17.7 kg m^‐2 yr^‐1). Significant differences in sedimentation rates were observed in two major vegetation types: dense herbaceous and shrubby vegetation (42.2 kg m^‐2 yr^‐1) and floodplain forest (12.7 kg m^‐2 yr^‐1). However, overbank sedimentation patterns also reflected imbricated hydrosedimentary and biogeomorphological vegetation feedbacks that co‐construct fluvial landforms. The incidence of an El Niño–Southern Oscillation–La Niña episode during the study period on sediment availability and floodplain sedimentation suggests that within whitewater rivers, where suspended sediment concentrations are naturally high, hydrological connectivity seems to be more important for floodplain sedimentation than variations in suspended sediment concentrations. These results may provide a good basis for future biogeomorphological investigation projects using complementary methodologies, in order to better anticipate global change and fluctuations in the occurrence, strength or duration of El Niño–La Niña episodes in the tropical zone and their consequences for flood discharge and sediment dynamics during channel–floodplain exchanges.     

FINE SEDIMENT INFILTRATION DYNAMICS IN A GRAVEL‐BED RIVER FOLLOWING A SEDIMENT PULSE

Pulses of fine sediment in gravel‐bedded rivers can cause extensive fine sediment infiltration (FSI) into void spaces in coarse bed material, potentially altering river morphodynamics and aquatic ecosystems. Previous work suggests a conceptual model of FSI whereby FSI occurs to a limited depth as a function of the relative grain size of bed sediment compared with infiltrating sediment and is influenced by fine sediment supply and local flow dynamics. Our study applies this conceptual model to a complex reach of a wandering, medium‐sized, gravel‐bed river to investigate the spatial and temporal controls on FSI. To constrain the timing of FSI, we use the release of contaminated sediment from an upstream dam removal and complementary field methods (bulk sampling, freeze cores and infiltration bags) to capture sediment across varied depositional settings. Our results indicate that, even in a morphologically complex reach, fine‐sediment content in the bed does not vary significantly among deposition settings or vertically below the bed surface. We also found that the most contaminated fine sediments released into our study river by a dam removal are not present within the bed material and that substrate has likely been reworked over the period between the release of contaminated sediment and sampling. Our observations also suggest that seals of fine sediment causing void pore space at depth, which have previously been associated with FSI, are not evident in our field area. This suggests that in natural systems, high sediment supply and mobile beds may limit seal formation and persistence. Copyright © 2013 John Wiley & Sons, Ltd.     

黄河悬移质非均匀不平衡输沙挟沙力计算

基于非均匀非平衡状态下挟沙力级配的研究成果,利用系统的黄河干支流资料,进行了混合沙挟沙力与实测含沙量符合性的对比分析。表明在非均匀沙不平衡输沙条件下挟沙力级配不同于悬沙级配,用挟沙力级配计算挟沙力更确切反映黄河干支流泥沙多来多排的输沙特点,说明该项研究成果在理论上是必要的,在实际中是可行的。     

Effect of Timber Harvest on Physical Water Quality Characteristics

The effect of 11% thinning on selected stream water properties in an oak-beech forest ecosystem in the Belgrad Forest of Istanbul, Turkey was studied with a paired catchment experiment. Regression equations for some physical properties of the stream water were developed between control (W-I) and treatment (W-II) watersheds for calibration (with their 95% confidence limits) and treatment periods. The study discovered significant linear regressions between control and treatment watersheds for color, turbidity, air and water temperatures, suspended sediment concentration, pH and electrical conductivity in the calibration period but not turbidity and suspended sediment concentration in the treatment period. The impact of the timber removal was calculated as the difference between measured and predicted values derived from calibration equations. Results showed that timber harvest caused significant decreases in the color, turbidity, temperature, pH, and electrical conductivity values of the stream water and air temperature under the canopy but did not affect the suspended sediment concentration in the stream water.     

EVALUATING SHALLOW‐WATER BATHYMETRY FROM THROUGH‐WATER TERRESTRIAL LASER SCANNING UNDER A RANGE OF HYDRAULIC AND PHYSICAL WATER QUALITY CONDITIONS

The fine‐scale structure of the water–sediment boundary in fluvial environments is dynamic and complex, influencing near‐bed flows, sediment transport and instream ecology. However, accurate high‐resolution surveying of marginally or partially inundated areas of river channels is problematic. Previous work has shown that terrestrial laser scanning (TLS) through relatively shallow‐water columns using standard green‐wavelength equipment introduces errors of <5 mm in a static, clear water column. This paper presents seven laboratory and field tests of through‐water TLS under variable flow velocities, depths, suspended sediment concentrations, water colour levels and scan ranges. Flow velocity decreased point accuracy only for supercritical flows, whereas point density decreased as a function of both water depth and suspended sediment concentration. A similar point return threshold was observed for water colour variations with no grains in suspension. Conversely, point precision and accuracy were a function of suspended sediment concentration alone (a threshold of 0.11 g L^?1 was observed). Field tests showed larger errors (<10 mm) and lower point precisions. A clear‐water depth‐penetration limit of 0.68 m was identified. Fluvial bathymetry acquired from through‐water TLS is presented for a gravel/boulder bed reach. Despite observed limits, these experiments demonstrate that our approach provides centimetre‐resolution bathymetry and sub‐aerial survey in an integrated dataset without the need for the following: (i) additional financial resources; (ii) concurrent depth measurements; or (iii) extra field effort for bathymetry acquisition, thereby enabling regular surveys to characterize the fine‐scale structure of channel beds and to constrain the geomorphic effect of individual flood events. Copyright © 2013 John Wiley & Sons, Ltd.     

Suspended sediment concentration in relation to forestry operations in Catamaran Brook and its tributaries (Canada)

The Catamaran Brook Habitat Research Project is a 15‐year investigation of river processes and potential impacts of forestry activities on Atlantic salmon (Salmo salar) and its freshwater lotic habitats. Suspended sediments have been sampled in Catamaran Brook and its tributaries from 1990 to 1997. Data on total event precipitation and hourly peak discharge were related to suspended sediment concentration (SSC) under different catchment conditions (dry vs. wet) and treatment (absence or occurrence of timber harvesting). Although SSC generally showed a good correlation to total event precipitation and hourly peak discharge, there was no clear evidence that forestry operations were an important factor within the main Catamaran Brook during the timber harvesting year and the year that followed. Such was not the case for SSC in small tributaries draining directly from cut blocks during logging. In fact, the highest concentrations of suspended sediment were measured in small tributaries draining cut blocks during timber harvesting (with a maximum SSC of 404 mg L⁻¹ in Tributary 1). Within the main Catamaran Brook, a dilution effect rapidly decreased these values downstream of affected tributaries. Processes related to the transfer of sediment to the streams are discussed. Potential improvements in river management and operational timing with respect to the timing of harvesting activities as it relates to precipitation, discharge, catchment conditions (dry vs. wet), freezing/thawing, and salmon migration are also discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Assessment of sediment quality of a tropical lake using sediment quality standards

Sediments are often reservoirs of contaminants in aquatic waterbodies, and their quality can be an indicator of the health of their ecosystems. Heavy metal pollution in sediments is highly significant because of their persistent and bioaccumulative nature. In this regard, sediment quality guidelines (SQG) are useful for categorizing sediment quality with respect to the contaminant level in them. An attempt was made in this study to assess the sediment quality of the Akkulam‐Veli (AV) Lake system on the basis of guidelines that incorporate assessment scales that differ in their approaches. Some link threshold levels of heavy metal concentrations on the basis of their likelihood to cause adverse effects, while others classify the sediment concentration ranges that correspond to the degrees of toxicity caused by them. The sediment quality of the study area was assessed by combining the available guidelines to formulate two new approaches in this study. Based on this approach, AV Lake is highly polluted with respect to chromium (Cr), nickel (Ni) and lead (Pb), while arsenic (As) and cadmium (Cd) are non‐polluting with a negligible potential for adverse effects.     

水库下游悬移质泥沙沿程恢复研究进展

水库下游悬移质泥沙沿程恢复是河流泥沙动力学研究的难点问题之一。对该问题的研究有助于推动学科发展,解决工程实践中的有关问题。针对此现状,归纳总结了平衡及不平衡输沙条件下悬移质浓度垂线分布、悬移质沿程恢复的天然河道实测资料分析和恢复饱和系数等方面的研究成果,认为在不平衡输沙条件下悬移质泥沙垂线分布研究及实测数据的获取、分析等方面还存在一定的不足。在此基础上,提出有必要进一步开展水库下游悬移质泥沙沿程恢复研究,特别是利用精准的测量仪器,开展科学合理、系统全面的水槽试验是丰富该研究成果的必要手段。     

Large wood addition for aquatic habitat rehabilitation in an incised,sand‐bed stream,Little Topashaw Creek,Mississippi

Large wood (LW) is a key component of stream habitats, and degraded streams often contain little wood relative to less‐impacted ones. Habitat rehabilitation and erosion control techniques that emphasize addition of natural wood in the form of individual elements or structures are increasingly popular. However, the efficacy of wood addition, especially in physically unstable, warmwater systems is not well established. The effects of habitat rehabilitation of Little Topashaw Creek, a sinuous, sand‐bed stream draining 37 km² in northwest Mississippi are described herein. The rehabilitation project consisted of placing 72 LW structures along eroding concave banks of a 2‐km reach and planting 4000 willow cuttings in sandbars opposite or adjacent to the LW structures. Response was measured by monitoring flow, channel geometry, physical aquatic habitat and fish populations in treated and untreated reaches for 2 years before and 4 years after rehabilitation. Initially, LW structures reduced high flow velocities at concave bank toes. Progressive failure of the LW structures and renewed erosion began during the second year after rehabilitation, with only 64% of the structures and about 10% of the willow plantings surviving for 3 years. Accordingly, long‐term changes in physical habitat attributable to rehabilitation were limited to an increase in LW density. Fish biomass increased in the treated reach, and species richness approximately doubled in all reaches after rehabilitation, suggesting the occurrence of some sort of stressful event prior to our study. Fish community composition shifted toward one typical of a lightly degraded reference site, but similar shifts occurred in the untreated reaches downstream, which had relatively high levels of naturally occurring LW. Large wood is a key component of sand‐bed stream ecosystems, but LW addition for rehabilitation should be limited to sites with more stable beds and conditions that foster rapid woody plant colonization of sediment deposits. Published in 2006 by John Wiley & Sons, Ltd.     

The assessment of suspended sediment inputs to Volta Lake

Information on a river basin's sediment yield is an important requirement for water resources development and management. In the Volta River basin of Ghana, data on suspended sediment yield are limited due to the lack of logistic support for systematic sediment sampling activities. This paper presents the results of a study using the available measurements of suspended sediment transport for eight monitoring stations in order to develop a simple predictive tool for estimating the suspended sediment yields for catchments for which no sediment measurements had been undertaken. Regression analysis was used to establish a relationship between specific suspended sediment yield and both the mean annual run‐off and the drainage basin area. The prediction model was used to estimate the sediment loads of the Volta River and its main tributaries (Black Volta, White Volta and Oti Rivers) in order to estimate the total suspended sediment input to the reservoir and the equivalent specific suspended sediment yield from the catchment surface. Although these sediment yield values are relatively low by world standards, the results obtained provide a basis for assessing future sedimentation problems in Lake Volta and for underpinning the development of sediment control and management strategies for the reservoir.