Temporal Effects of St. Clair River Dredging on Lakes St. Clair and Erie Water Levels and Connecting Channel Flow

A Great Lakes hydrologic response model was used to study the temporal effects of St. Clair River dredging on Lakes St. Clair and Erie water levels and connecting channel flows. The dredging has had a significant effect on Great Lakes water levels since the mid-1980s. Uncompensated dredging permanently lowers the water levels of Lakes Michigan and Huron and causes a transitory rise in the water levels of Lakes St. Clair and Erie. Two hypothetical dredging projects, each equivalent to a 10 cm lowering of Lakes Michigan and Huron, were investigated. This lowering is approximately half the effect of the 7.6 and 8.2 meter dredging projects. In the first case the dredging was assumed to occur over a single year while in the second it was spread over a 2-year period. The dredging resulted in a maximum rise of 6 cm in the downstream levels of Lakes St. Clair and Erie. The corresponding increase in connecting channel flows was about 150 m³s^?1. The effects were found to decrease over a 10-year period with a half-life of approximately 3 years. The maximum effects on Lake Erie lagged Lake St. Clair by about 1 year.     

Relationships between wind-driven and hydraulic flow in Lake St. Clair and the St. Clair River Delta

A three-dimensional hydrodynamic forecasting model of the Great Lakes Huron-Erie Corridor is used to investigate mixing and the relationship between hydraulic and wind-induced currents in a shallow lake system in which lake inflows come through several channels of a river delta. The hydrodynamics in Lake St. Clair and the channels of the St. Clair River Delta are evaluated for (1) a one-year simulation from 1985 including water age calculation, (2) 8 different wind direction scenarios, and (3) a storm event. Observations and model simulations show distinct regions in the lake in which currents are forced by either hydraulic flow from the river system or from wind stress over the lake. However, during severe storm events, these regions are found to shift or even disappear due to changes in the delta channel inputs into the lake. These changes underscore the need for realistic, unsteady river flow boundary conditions at interfaces between a shallow lake and river delta. Steady inflow conditions will not allow for potential shifting of these current zones, and will also fail to resolve flow retardation or reversals during storm events.     

水力学方法估算大桥对河道防洪的影响

 提出了估算大桥对河道防洪影响的水力学方法，采用这一方法，可以在河道地形和水文资料缺乏的情况下，估算出中、小型河道建桥后桥址上游水位壅高值和壅水范围。具体水力学方法包括：断面流量模数法、宽顶堰淹没出流法、局部水头损失法和恒定渐变流法。应用这些方法，成功地进行了洪湖市汉洪公路新滩东荆河大桥对桥址上游河道防洪影响的计算分析。     

Temporal and spatial trends of organochlorines and mercury in fishes from the St. Clair River/Lake St. Clair corridor,Canada

The temporal and spatial relationships of a suite of organochlorine contaminants and mercury were examined in various fish species of the St. Clair River/Lake St. Clair corridor, Canada, in order to evaluate the effectiveness of remediation efforts and to assess the risk to human and wildlife fish consumers. In Lake St. Clair, fish tissue concentrations of mercury, polychlorinated biphenyls (PCBs), octachlorostyrene (OCS), hexachlorobenzene (HCB), and dichlorodiphenyltrichloroethane (DDT) decreased consistently from the 1970s until the 1980s and 1990s, after which the rate of contaminant decline slowed or concentrations stabilized. This trend was consistent in up to 13 species (both young-of-the-year and adult fishes) comprising different trophic positions and dietary habits, suggesting that the changes were reflective of ambient conditions rather than food web processes. Elevated concentrations of mercury, PCBs, OCS, HCB, and DDT were detected in St. Clair River young-of-the-year spottail shiner compared with fish from Lake Huron, indicating that non-atmospheric inputs of these chemicals, likely originating from sediment, remain in the St. Clair River. Current concentrations of mercury and PCBs, and mercury, PCBs, and DDT remain of concern to human and wildlife fish consumers, respectively. Given that contaminant decreases have generally stabilized in fish, we suggest that further natural recovery of contaminants in St. Clair corridor fishes will be slow since contaminants will likely continue to be influenced by sediment levels.     

Formation of the St. Clair River Delta in the Laurentian Great Lakes System

The St. Clair River delta, the largest in the Laurentian Great Lakes system, is located in Lake St. Clair at the mouth of the St. Clair River. It straddles the border between the state of Michigan in the USA and the province of Ontario in Canada. The current study aims at characterizing and explaining the formation and evolution of the distributary channels in the St. Clair River delta and the delta itself. The delta is classified as a river dominated feature with classic “bird's foot” structure similar to the Mississippi delta model. The delta is composed of two surfaces. The older surface at the delta apex was deposited at a higher lake level some 3,500 to 5,000 years B.P. The current delta started to form following a drop in lake level some 3,500 years B.P. and continues to build to the present day. The delta consists of seven active deep channels averaging 11 m in depth entering a lake with a mean depth of 3 m with much shallower water in the delta front region. The channels are stable and are actively eroding into the sediments of the lake creating both sub-aqueous and sub-aerial levee deposits with crevasses. The interdistributary bays are being filled with sandy deposits created by wave energy and by crevasse deposits. At the erosional front of each distributary a narrow erosional notch “leading channel” is being formed which appears to control the direction of lakeward erosion of each deep distributary channel. The emplacement of the delta body in the shallow receiving water body has been termed “burrowing” delta formation and is the mechanism controlling the formation of this sedimentary feature.     

Assessment of larval fish assemblages and nursery habitat in the St. Clair River delta

The St. Clair River delta, part of the St. Clair-Detroit River System (SCDRS), is the most fished coastal wetland area in the Laurentian Great Lakes and provides nursery habitat for a variety of fish species; however, few large-scale surveys of larval fish have been performed within the delta since the 1980s. Larval fish, zooplankton, and aquatic plants were sampled at 20 sites from May through July in 2010 and 2011 to characterize shallow channel and backwater delta habitats used by fish. The larval fish assemblage was sampled using active and passive gears (conical nets and light traps) and was dominated by Cyprinidae, Catostomidae, and Gobiidae. The microzooplankton assemblage was composed of rotifers, copepod nauplii, and Dreissena spp. veligers, while the macrozooplankton assemblage was composed of mostly cyclopoids and harpacticoids in May and cladocerans later in the season. Scirpus spp. dominated the plant assemblage in June and was replaced by Chara spp. in July. Seasonal compositional shifts were evident for larval fish, zooplankton, and plant assemblages, and greater densities of microzooplankton and cladocerans were typically found in backwater areas. Assemblage compositions were comparable to those in historical surveys but invasive Gobiidae and Dreissena spp. veligers now represent substantial proportions of the larval fish and zooplankton assemblages, respectively. Due to the high connectivity and advective nature of the SCDRS, understanding the larval fish assemblage dynamics of the delta can help inform estimates of system productivity.     

Erosion of glacial till from the St. Clair River (Great Lakes basin)

Variations in water level observed in Lakes Michigan and Huron during the last few decades have motivated a comprehensive study involving climatic, hydrologic and hydraulic factors organized by International Joint Commission of the Great Lakes. It has been submitted, among other possible causes, that changes in conveyance in the St. Clair River could be contributing to the lowering of the upper Great Lakes water level. Sediment transport processes, in particular bed scour and erosion, can affect significantly a river's conveyance, thus creating the need to assess the erodibility properties of the river bed. To this end, laboratory tests were performed in order to obtain the value of the critical shear stress needed to erode the cohesive fraction of the bed sediment material, known as glacial till, from the St. Clair River. Different flows with increasing velocities were run up to the point where initial sediment erosion could be observed. Through detailed near-bed velocity measurements using a laser Doppler velocimetry (LDV) system, a value of 4.2 N/m² was obtained as the critical shear stress for the erosion of glacial till. A threshold for the critical shear stress for erosion of similar cohesive sediments was also found and expressed in dimensionless form. These results could be used in combination with mathematical models to estimate the risk of scour and erosion at locations where the glacial till is exposed to both strong currents and flow forces induced by the large navigation vessels commonly observed along the course of the St. Clair River.     

Bed morphology, flow structure, and sediment transport at the outlet of Lake Huron and in the upper St. Clair River

An integrated multibeam echo sounder and acoustic Doppler current profiler field survey was conducted in July 2008 to investigate the morphodynamics of the St. Clair River at the outlet of Lake Huron. The principal morphological features of the upper St. Clair River included flow-transverse bedforms that appear weakly mobile, erosive bedforms in cohesive muds, thin non-cohesive veneers of weakly mobile sediment that cover an underlying cohesive (till or glacio-lacustrine) surface, and vegetation that covers the bed. The flow was characterized by acceleration as the banks constrict from Lake Huron into the St. Clair River, an approximately 1500-m long region of flow separation downstream from the Blue Water Bridge, and secondary flow connected to: i) channel curvature; ii) forcing of the flow by local bed topography, and iii) flow wakes in the lee side of ship wrecks. Nearshore, sand-sized, sediment from Lake Huron was capable of being transported into, and principally along, the banks of the upper St. Clair River by the measured flow. A comparison of bathymetric surveys conducted in 2007 and 2008 identifies that the gravel bed does undergo slow downstream movement, but that this movement does not appear to be generated by the mean flow, and could possibly be caused by ship-propeller-induced turbulence. The study results suggest that the measured mean flow and dredging within the channel have not produced major scour of the upper St. Clair River and that the recent fall in the level of Lake Huron is unlikely to have been caused by these mechanisms.     

Surface Deposition of Lead and Cadmium from the Atmosphere in the Detroit River—Lake St. Clair Region

The research reported here forms part of a large multidisciplinary study of four toxic contaminants — lead, cadmium, PCBs, and octachlorostyrene in the Essex region of southwestern Ontario. The purpose of this part of the project is to quantify the atmospheric loading of the metallic contaminants. A bulk precipitation sampler, wet-only precipitation sampler, and recording rain gauge were installed at an urban and rural site. Results from 2 years of data indicate that atmospheric loading of lead is 40–50 times that of cadmium in the city and 16–40 times that of cadmium in the rural areas. Lead loadings in the city were found to be 2–4 times higher than in the rural areas, while cadmium loadings appeared to be similar in both areas. Concentrations of the metals are higher in winter than in summer, but because of higher summer precipitation surface loadings are similar in both seasons. Preliminary statistical analysis indicates that concentrations of the metals are related to intensity and amount of precipitation but not usually to wind direction.     

Occurrence of Alkyllead Compounds in the Detroit and St. Clair Rivers

Environmental occurrence of alkyllead compounds, both of molecular species, e.g., tetraalkyllead, and ionic species, e.g., dialkyllead and trialkyllead, is believed to be derived mainly from anthropogenic sources such as effluents of alkyllead production plants and from slow degradation of tetraalkyllead in the environment. The present study describes a survey for the occurrence of tetraalkyllead, trialkyllead, dialkyllead, and Pb(II) (R = Me, Et) in water, surface microlayer, fish, and sediments from 29 stations in the St. Clair and Detroit rivers, including the western basin of Lake Erie. Results indicated that triethyllead and diethlylead compounds have been found for the first time in fish and surface microlayer in St. Clair River near Corunna where a production plant is located. About 48% of the surface microlayer samples contained various alkyllead compounds whereas only one water sample taken from the St. Clair River was found to contain alkyllead. Alkyllead compounds were found in several species of fish caught in the St. Clair River, with northern pike containing the highest concentration of alkyllead (0.173 μg/g) followed by white sucker, carp, and walleye. The concentrations of alkyllead in some individual fish reached the p.p.m. level which is considered highly hazardous for consumption although health criteria for alkyllead are not yet available. The ratios of alkyllead to total lead ranged from 0% for yellow perch and brown trout to 56% for carp.     

Effect of the Niagara River Chippawa Grass Island Pool on Water Levels of Lakes Erie,St. Clair,and Michigan-Huron

Because of renewed riparian interest stemming from the high Lake Erie water levels of the mid-1980s and mid-1990s, and the need for a concise summary of previous studies, a review and a new assessment of the impact of the Niagara River's Chippawa Grass Island Pool on Lake Erie water levels was undertaken. Numerous field and modeling studies dating from 1953 through 1988 provide different assessments of the impacts. The impacts reported by the studies range from “no measureable effect” to a 2 to 5 cm Lake Erie water level decrease. The different results are due to different methods and data, and the fact that the impacts are not directly measureable. A new Great Lakes routing model that more accurately reflects the upper Niagara River hydraulics by explicitly considering the management directive of the Chippawa Grass Island Pool is used to estimate the impacts of deviating from the present directive. The long-term impact of a 0.30 m increase or decrease from the current directive's long-term mean pool level on Lakes Erie, St. Clair, and Michigan-Huron levels is 5 cm, 4 cm, and 2 cm and −4 cm, −3 cm, and −2 cm, respectively. The lakes are minimally responsive to short-term changes in pool levels, with 50% of the Lake Erie impact achieved at about 6 months, and full impact achieved at about 2 years. The minimal lake response, the time lag to full impact, and the local problems resulting from directive deviations, make this a less favorable emergency response measure during periods of extreme lake levels than other alternatives.     

Chlorinated Contaminants in Surficial Sediments of Lakes Huron,St. Clair,and Erie: Implications Regarding Sources Along the St. Clair and Detroit Rivers

Surficial sediments from southern Lake Huron, Lake St. Clair, and Lake Erie have been analyzed for a broad spectrum of chlorinated organics including PCBs, chlorobenzenes, and several pesticides. The differences between sediment contaminant concentrations in Lake Huron and Lake St. Clair indicated sources of hexachlorobenzene, hexachlorobutadiene, octachlorostyrene, and several other chlorinated benzenes along the St. Clair River. Similar differences between sediment PCB concentrations in Lakes Huron/St. Clair and Lake Erie indicated major PCB sources along the Detroit River. Specific PCB congener analysis revealed that PCBs discharged to the Detroit River contained especially high concentrations of highly chlorinated hexa-, hepta-, and octachloro-biphenyls which are major constituents of the industrial mixture Aroclor 1260. The analysis of individual PCB congeners made it possible to trace PCBs of Detroit River origin to the central and eastern basins of Lake Erie, and to estimate the contribution of the Detroit River to the PCB burden in sediments of these basins.     

Changes in the Freshwater Mussel Community of Lake St. Clair: from Unionidae to Dreissena polymorpha in Eight Years

To determine density changes in both the zebra mussel, Dreissena polymorpha, and native mussels, Unionidae, in Lake St. Clair, surveys were conducted in 1990, 1992, and 1994 and compared to a similar survey in 1986 when no D. polymorpha was found. Collection methods were the same each year; divers used the quadrat method to collect 10 replicate samples at 29 sites located throughout the lake. The total number of unionids collected declined from 281 in 1986, to 248 in 1990, 99 in 1992, and 6 in 1994, while the number of species collected in each of the four respective years was 18, 17, 12, and 5. The decline in the unionid community occurred gradually over this time period as the D. polymorpha population expanded from the southeast region of the lake to the northwest region. Mean density and biomass of D. polymorpha throughout the lake was 1,700 m⁻² and 4.7 gDW m⁻² in 1990, 1,500 m⁻² and 3.5 gDW m⁻²in 1992, and 3,200 m⁻² and 3.1 gDW m⁻² in 1994. The density increase can be attributed to the expansion of the population into the northwest region, while the decrease in biomass was mostly a result of a decline in the weight per unit length. Mean biomass of the D. polymorpha population in 1994 was actually lower than the mean biomass of unionids in 1986; however, based on literature-derived filtering rates, the filtering capacity of the D. polymorpha population in 1994 was 12 times greater than the filtering capacity of the unionid community in 1986. This increase has likely led to reported changes in the Lake St. Clair ecosystem (increased water clarity, increased plant growth, and shifts in fish communities).     

三峡工程蓄水运用以来荆江水位流量关系变化分析

根据三峡工程蓄水前后的实测资料,分析了荆江河段沿程水位流量关系变化。研究成果表明：除枝城站在枯水流量下水位略有下降外,上荆江在中、枯流量下水位也均有一定程度的下降,其中沙市站枯水位下降最大,下荆江河段水位在同流量下略有下降。除枝城站枯水位变化受卢家河浅滩形成的沙坎石泓影响外,三峡工程蓄水后影响荆江河段水位流量关系变化的...     

江湖流量分配变化导致长江中游新的洪水形势

本文全面论述了江湖流量分配变化导致长江中游出现的新防洪形势。文中首先举出江湖流量分配的巨大变化。     

1980—2015年资水尾闾水文条件变化分析

通过桃江、益阳水文站1980—2015年逐日水位和流量资料,分析资水尾闾水位、流量变化趋势及突变情况,初步探求引起这一变化的原因及其影响。结果表明:近36 a来,资水尾闾径流量年际间呈周期性波动,丰、枯水期交替出现,自2000年以后进入少水期,径流量整体上呈下降趋势,但这一趋势并不显著;受无序采砂导致河床大幅下切及湘水洪道水位降低等因素影响,资水尾闾水位下降,发生均值突变,桃江站降幅达1.72 m,益阳站达0.80 m;因水位突变导致流域水位-流量关系发生明显改变,原有河湖双向互补的关系也发生变化,湖水单一补给入河,一定程度上缓解了资水水位的进一步下降。研究成果可为资水综合开发利用及灾害防治提供科学依据。     

Temporal trends in near-shore sediment contaminant concentrations in the St. Clair River and potential long-term implications for fish tissue concentrations

Near-shore surface sediment of the St. Clair River (Ontario) extending along 9 km of waterfront downstream of local industries were contaminated with mercury (Hg), hexachlorobenzene, hexachlorobutadiene and octachlorostyrene based on data collected in 2006 and 2008. However, unlike Hg, concentrations of organic compounds were low at most stations suggesting improvements in sediment quality since 2001 (post sediment remediation projects). Concentrations of Hg were greater than Provincial Sediment Quality Guidelines and ranged as high as 41 μg/g in the surficial 0–5 cm sediment. Measured (2001–2004 data) and estimated (2006 data) concentrations of methyl Hg in invertebrates were greater than concentrations in invertebrates collected from upstream reference stations. Predicted methyl Hg concentrations in walleye using food chain multipliers, benthic invertebrate Hg tissue concentrations and current sediment concentrations exceeded human health consumption guidelines and were consistent with measured sport fish data supporting assumptions about Hg biomagnification. Historical data showed that for fish collected from the lower St. Clair River and Lake St. Clair, Hg concentrations have declined since 1978, but have remained stable since the mid 1980s, consistent with the sediment Hg data. The consistency in the sediment and fish datasets and the absence of a known significant local point source of Hg suggests that the sediment may be an important source of Hg to the St. Clair River food-chain.     

城市人工湖动态换水水位对流速分布影响

水位和流速是人工湖维持生态的关键因子,为探究人工湖水位对流速分布的影响,基于二维水动力模型对雁鸣湖流场进行数值模拟,研究单因素水位对流速影响和实测换水水位对流速时空分布的影响。结果显示:水位是水动力影响因素之一,低水位时的湖泊流速大于高水位时期,水位变化时的平均流速介于高低水位流速之间,水位对环流影响较小。在实测换水期间,高水位时水位分布无明显差异,水深自上游至下游逐级递增;低水位时水位分布出现差异,河滩裸露,水深分布差异较大;水位变化时,湖泊上游至下游水位呈梯度变化,水深随水位变化;流速时空分布验证了单因素水位对流速的影响,并表明不同水位对流速大小及分布影响有所差异。雁鸣湖水位和流速的模拟结果表明,人工湖水位变化能改善湖泊水动力,可为人工湖水情管理提供科学参考。     

长江中游沙卵石-沙质河床过渡带冲刷趋势研究

通过30余年特别是三峡水库蓄水以来水文、地形、地质等实测资料的系统收集，对长江中游枝城-陈家湾沙卵石-沙质河床过渡带冲刷特性和发展趋势开展分析，其结果表明：虽然河段内自上而下呈现出卵石逐渐减少而沙质比例逐渐增多的渐变特点，但以昌门溪~马家店一带为界，上下游的洲滩组成、深泓形态、河床冲淤、水位下降等方面存在突变现象。在三峡水库蓄水后的冲刷过程中，虽然全河段内均出现了汊道冲刷、枯期河槽扩大的现象，但可以预计的是，河段内河势不会发生大的变化，而昌门溪以下河段难以抵御水位下降的溯源传递，马家店以上在枯水期将出现比现状更为严重的坡陡、流急、水浅现象。     

Organochlorine and Mercury Residues in Young-of-the-Year Spottail Shiners from the Detroit River,Lake St. Clair,and Lake Erie

Young-of-the-year spottail shiners (Notropis hudsonius) were used as biomonitors to determine the spatial distribution (1982/83) and assess trend data for organochlorine and mercury residues. Significantly (p < 0.01) higher PCB residues were found in Detroit River spottail shiners than in collections from southwestern Lake St. Clair and northwestern Lake Erie. The highest PCB residues were found in the west bank collections from Michigan waters (912–2,997ng/g) compared to the mid-stream (96–290 ng/g) and east bank collections (153–316 ng/g). Chlordane residues were found to be elevated in all spottail shiner samples from urbanized areas. Octachlorostyrene and ∑ DDT residues were distributed uniformly within the study area, whereas mercury concentrations were found to be lower in spottail shiners from northwestern Lake Erie than in comparable samples from the Detroit River and southwestern Lake St. Clair. Residues for BHC, heptachlor, aldrin, and chlorinated benzenes were near their detection limits; mirex and chlorinated phenols were not detectable. Recent (1982/83) PCB residue levels in spottail shiners exceeded the IJC aquatic life objective (Great Lakes Water Quality Agreement of 1978) at all the sites sampled, except at Pike Creek in Lake St. Clair. PCB residues in spottail shiners from Pike Creek, Big Creek, and Leamington have declined significantly (p < 0.01) since the mid-seventies. Mercury and chlordane residues have decreased in spottail shiner samples from Leamington, but have remained virtually unchanged at Big Creek and Pike Creek.