Updated phosphorus loads from Lake Huron and the Detroit River: Implications

The binational Great Lakes Water Quality Agreement (GLWQA) revised Lake Erie’s phosphorus (P) loading targets, including a 40% western and central basin total P (TP) load reduction from 2008 levels. Because the Detroit and Maumee River loads are roughly equal and contribute almost 90% of the TP load to the western basin and 54% to the whole lake, they have drawn significant policy attention. The Maumee is the primary driver of western basin harmful algal blooms, and the Detroit and Maumee rivers are key drivers of central basin hypoxia and overall western and central basin eutrophication. So, accurate estimates of those loads are particularly important. While daily measurements constrain Maumee load estimates, complex flows near the Detroit River mouth, along with varying Lake Erie water levels and corresponding back flows, make measurements there a questionable representation of loading conditions. Because of this, the Detroit River load is generally estimated by adding loads from Lake Huron to those from the watersheds of the St. Clair and Detroit rivers and Lake St. Clair. However, recent research showed the load from Lake Huron has been significantly underestimated. Herein, I compare different load estimates from Lake Huron and the Detroit River, justify revised higher loads from Lake Huron with a historical reconstruction, and discuss the implications for Lake Erie models and loading targets.     

尼亚加拉河流及瀑布演化浅析

较全面地介绍了尼亚加拉河和尼亚加拉瀑布,并从其成因、演化、溯源侵蚀及其岩性、气候、流量、科氏力、含砂量、瀑布形态、人类活动等方面进行了探析。展望了今后的发展与演化。     

黄河下游悬河温县段河水位变化对侧渗的影响研究

黄河水资源是沿黄地区经济和社会发展的重要限制因子。由于黄河在下游河段形成地上悬河,黄河的侧渗成为该地区地下水的重要补给源。通过分析温县的含水层结构,建立了地下水的二维模型,应用feflow软件对温县的浅层地下水进行了模拟,并对不同黄河水位变化情况下的黄河侧渗量进行了模拟计算,认为随着黄河水位的变化,将会引起两岸地下水位的相应变化,这为该县的水资源管理提供了依据。     

Identifying important micro-habitat characteristics of muskellunge spawning locations in the upper Niagara River

Conserving and restoring muskellunge (Esox masquinongy) spawning habitat are essential for maintaining self-sustaining populations. A Maxent model was developed based on presence and background data to investigate the relationship between the occurrence of spawning muskellunge and habitat features in the upper Niagara River. Muskellunge spawning points (n = 15) were determined by direct observation of spawning pairs. Model inputs were based on micro-habitat features collected at each spawning point and a sample of 250 background habitat points. The full model was reduced to a four variable model to remove uninformative variables and reduce overfitting and redundancy. Model performance was evaluated based on the mean test gain of cross-validated models (n = 15). Model outputs identified aquatic macrophyte/algae coverage as the most important habitat feature at spawning locations. The relative probability of muskellunge spawning increased with the percent rank of total aquatic macrophyte/algae coverage, water velocity, and water depth and it was highest at points with muddy-sand to sand substrates. Mean test gain (0.68; SE = 0.52) of the cross-validated models indicated that the likelihood of an average muskellunge spawning point was nearly two times greater than an average background point. Results from this research advance our knowledge of muskellunge reproductive ecology, while providing scientists and managers with quantitative measures to guide habitat conservation and restoration.     

滹沱河大型入渗试验地下水补给量计算

通过采用水均衡法计算了滹沱河入渗试验期间的河道入渗补给量,并求取了滹沱河水源地一带获得的河道入渗补给量。研究表明:试验期间河道入渗水量为1 482.75万m3,河道入渗补给地下水量为1 382.89万m3,河道渗漏补给系数为93%;滹沱河水源地接受的补给量为742.53万m3,水源地范围内的观测井最大水位上升幅度6.823m,地下水补给效果明显。     

Volatile Contaminants in the Welland River Watershed

Surveys of selected volatile contaminants in water of the Welland River, a tributary to the Niagara River, in 1980 and 1981 show high levels of carbon disulfide, methylene chloride, and chloroform immediately below two industrial outfalls. Downstream from these point sources, a rapid decline in the contaminant concentrations is noted due to dilution, degradation, and/ or volatilization of the compounds. Although toxic effects of other components of these effluents have been observed, the concentrations of the volatile contaminants are several orders of magnitude lower than those at which acute toxic effects on biota are observed.     

Influence of water temperature on rainbow smelt spawning and early life history dynamics in St. Martin Bay,Lake Huron

Rainbow smelt are an important prey species for native and introduced salmonines in the Great Lakes. In Lake Huron, rainbow smelt populations are characterized by variable recruitment and year-class strength. To understand the influence of water temperature on reproduction, growth, and survival during larval-fish stages, we sampled spawning tributaries and larval-fish habitats during 2008 and 2009 in St. Martin Bay, Lake Huron. Spawning by rainbow smelt occurred primarily when stream temperatures were between 3 and 10 °C, which resulted in a 7–10-day spawning period during 2008, and a 15–20-day spawning period during 2009. Regardless of these differences in spawning temperatures and duration, peak larval-fish densities during 2008 were double those observed during 2009. Length–frequency analysis of larval-fish populations during both years revealed stream-hatched fish during May and a later emergence of larval rainbow smelt during summer, presumably originating from lake spawning. Warmer bay water temperatures led to earlier emergence of lake-spawned rainbow smelt larvae during 2009. Stream-hatched fish larvae experienced large-scale mortality during May 2008 resulting in a bay population consisting primarily of lake-spawned rainbow smelt larvae, but during 2009 both stream- and lake-hatched cohorts experienced higher survival concomitant with significantly higher mean population growth rates. Higher larval-fish growth rates during 2009 appeared to be density-dependent and facilitated by warmer water temperatures during late June and cooler water temperatures during July. Temperature-mediated differences in annual growth rates and irregular contributions from stream- and lake-hatched fish larvae are important factors affecting survival and abundance of young-of-the-year rainbow smelt in Lake Huron.     

Monitoring metal and persistent organic contaminant trends through time using quagga mussels (Dreissena bugensis) collected from the Niagara River

Historically, the Niagara River received the discharge of persistent bioaccumulative and toxic chemicals from municipal and industrial outfalls and hazardous waste landfills. American and Canadian governments have coordinated investigations of chemicals entering the river and initiated remedial measures and monitoring programs with a goal to reduce loadings of toxic chemicals to the river. This study, a component of the Ontario Ministry of Environment Mussel Biomonitoring Program, compares contaminant concentrations in quagga mussels (Dreissena bugensis) collected from nine locations in the Niagara River in 1995 and 2003 to assess anticipated changes in tissue concentrations of contaminants in response to ongoing remedial efforts by government agencies and local industries. The concentrations of persistent organic compounds (e.g., PCBs, hexachlorobenzene, hexachlorobutadiene, octachlorostyrene) in quagga mussels in 2003 were lower than concentrations measured in 1995, consistent with a decrease in reported mean annual concentrations of these compounds in water. Significant differences in total PCB concentrations in mussels between stations (F = 4.6; P < 0.001) suggested sources of PCBs on the American side of the upper Niagara River. In general, highest concentrations of persistent organic compounds were found downstream of the Occidental Chemical Corporation Buffalo Avenue facility suggesting local sources of these contaminants notwithstanding remedial efforts. In contrast, metal concentrations in quagga mussels in 2003 were similar to concentrations found in 1995 and to values reported in the literature for mussels collected from industrialized areas in the Great Lakes. Overall, our results suggest that remedial efforts to improve water quality in the Niagara River have been successful.     

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.     

The contribution of cold winter temperatures to the 2003 alewife population collapse in Lake Huron

The Lake Huron ecosystem has recently undergone dramatic changes. As part of those changes, the once highly abundant non-native alewife Alosa pseudoharengus population crashed in 2003 and has yet to recover. The purpose of this study was to evaluate whether temperature played a role in the population crash, because historically alewife have been subject to die-off events in response to cold temperatures in other lakes. Long-term climate data (1973–2009) showed that the winter of 2002–2003 exhibited the largest drop in degree days relative to the previous year, had the most extensive average March ice coverage, and was among the coldest years on record. However, since 2003, winter temperatures have not been overly cold, and air temperature has shown an increasing trend. Also, the relationship between temperature and alewife abundance between 1975 and 2006 was non-significant. Therefore, although we found evidence that cold winter temperatures contributed to the abrupt decline of alewife in 2003, they could not explain why the population failed to recover as it had after previous cold winters. Historically, Chinook salmon abundance contributed to long-term trends in alewife abundance, however, we found predation by Chinook to play a lesser role on the 2003 alewife collapse. In the absence of direct estimates of food availability, analyses of alewife length data suggest that a declining prey base altered the ecosystem conditions for alewife, possibly contributing to their collapse and lack of recovery.     

River regulation by seasonal groundwater abstraction: The case of the River Itchen

This paper describes the development of groundwater to regulate the flows of the River Itchen in Southern England. The permeable chalk geology of the river catchment makes the use of natural groundwater storage more cost effective than conventional surface reservoirs. The principles of groundwater regulation and the construction and testing of the first two schemes are described. Flow extension and mathematical modelling have been used to assess yields and assist with operational decisions. The paper concludes that groundwater regulation is a viable alternative to reservoirs in permeable catchments and further schemes are planned.     

A modeling study to determine the contribution of interbasin versus intrabasin phosphorus loads on the southwestern nearshore of Lake Ontario

Elevated phosphorus and nuisance algae such as Cladophora have been persistent environmental concerns in the coastal areas of Lake Ontario. Phosphorus is regarded as one of the drivers of nearshore Cladophora and the most likely mitigation that can be used to control levels of this nuisance algae in the lakes. The Niagara River, carrying the Lake Erie interbasin load, is the major contributor of the overall phosphorus load to Lake Ontario. Due to circulation patterns in the lake, this contribution is especially significant in the southwestern nearshore areas. Here we apply a mathematical model to provide insight into the relative contribution of the Niagara River versus loadings from local rivers (intrabasin loads) on the nearshore phosphorus concentrations in this region. We performed numerical experiments to determine to what extent the Niagara, Genesee and smaller local rivers impact the nearshore (<20 m depth) phosphorus concentrations. Our model results show that the Niagara River dominates the nearshore region between its discharge location and the Genesee River’s mouth, but the Genesee River strongly impacts the nearby Ontario Beach region in the very nearshore (<5 m depth). Smaller rivers have some impact close to their discharge locations. However, uncertainty with the Niagara River phosphorus load is the limiting factor in making any credible nearshore phosphorus predictions. Model accuracy is also impacted by insufficient short time scale phosphorus loads for all of the rivers, the dynamic nature of the lake circulation in shallow nearshore areas, and the simplified assumptions of the model.     

海河流域地下水系统脆弱性评价的探讨

海河流域地下水目前面临着严峻的生态与环境问题。结合海河流域具体情况,选择山前平原的石家庄和唐山、中部平原的沧州和衡水、东部滨海平原的天津等地作为5个典型区域进行具体研究。在采用DRASTIC方法对典型区域进行地下水脆弱性评价时,选取了地下水埋深、土壤有机质含量、含水层的渗透系数、含水层累计（沙层）厚、降雨灌溉等入渗补给率、地下水开采系数这6个参数作为评价指标,并以此指标体系为基础进行了脆弱性研究。结果表明,海河流域地下水各典型区的脆弱性指数均较高,海河流域地下水的脆弱性问题较为严重。要恢复和提高地下水系统的生态与环境功能,需采取6项对策措施。     

Influence of the St. Marys River Plume on Northern Lake Huron Phytoplankton Assemblages

Analysis of phytoplankton samples from the Straits of Mackinac region yielded high species diversity and species richness values at the outfall of the St. Marys River due to entrained benthic diatoms. Epilithic, psammonic, epipelic, and epiphytic diatoms originating in the St. Marys River and Detour Passage area were removed from their primary habitats and transported into northern Lake Huron. Southward movement of the St. Marys River plume, as determined from suspended benthic diatom distribution and abundance, was strongly indicated for 3 km. Moderate influence of the plume was noted at 6 km and weaker association with the plume was detected for as far as 32 km. Apparently, loss of suspended riverine species from the upper water column in this area was primarily due to sinking. Sinking, calculated from residence times based on river discharge data, was estimated to range between 0.76 and 5.99 m/day. Total phytoplankton abundance and chlorophyll a values were lower near the rivermouth. Conversely, ¹⁴C uptake was significantly greater near the river. Benthic populations comprised as much as 40% of the assemblage and an additional amount of dead and fragmentary diatoms was also observed. Viable benthic diatoms may contribute as much as 25% of the algal assemblage on a cell volume basis. Upon death and decomposition, they may constitute an important source of carbon and nutrients in the immediate vicinity.     

南水北调中线沙河至黄河段沿线地下水位变化规律研究

地下水问题是南水北调中线工程建设遇到的三大关键技术难题之一,研究揭示沿线地下水动态变化规律对保证工程安全具有重要意义。2010年-2012连续3年在丰、枯水期,利用22眼监测井对中线沙河至黄河段沿线分别开展了地下水位监测,并收集整理了沿线40km范围内的11眼国家级地下水位长期监测资料。通过对这些监测数据分析,初步认为中线沙河至黄河段沿线地下水位变化趋势虽然总体上比较平稳,但由于沿线水文地质、工程地质条件复杂(膨胀土渠段、上层滞水分布广泛等),存在较多风险渠段,如遭遇强降雨等外界不利因素,地下水仍可能会对工程安全造成威胁。     

Telemetry reveals limited exchange of walleye between Lake Erie and Lake Huron: Movement of two populations through the Huron-Erie corridor

Immigration and emigration of individuals among populations influence population dynamics and are important considerations for managing exploited populations. Lake Huron and Lake Erie walleye (Sander vitreus) populations are managed separately although the interconnecting Huron-Erie Corridor provides an unimpeded passageway. Acoustic telemetry was used to estimate inter-lake exchange and movement within St. Clair River and Detroit River. Of 492 adult walleyes tagged and released during 2011 and 2012, one fish from Tittabawassee River (Lake Huron; 1 of 259, 0.39%) and one individual from Maumee River (Lake Erie; 1 of 233, 0.43%) exchanged lakes during 2011–2014. However, both fish returned to the lake where tagged prior to the next spawning season. The one walleye from Maumee River that moved to Lake Huron made repeated round-trips between Lake Erie and Lake Huron during three consecutive years. Of twelve fish tagged in the Tittabawassee River detected in the Huron-Erie Corridor, few (n = 3) moved south of Lake St. Clair to the Detroit River. Ten walleye tagged in the Maumee River entered the Huron-Erie Corridor, and five were detected in the St. Clair River. Our hypothesis that walleye spawning in Maumee River, Lake Erie, served as a source population to Lake Huron (“sink population”) was not supported by our results. Emigration of walleye to Lake Huron from other populations than the Maumee River, such as those that spawn on in-lake reefs, or from Lake St. Clair may contribute to Lake Huron walleye populations.     

Morphometric differentiation and gene flow in emerald shiners (Notropis atherinoides) from the lower Great Lakes and the Niagara River

Differences in habitat (e.g., water velocity, prey, and predator regimes) are a driving force causing adaptive divergence among fish populations. This study used geometric shape analysis to assess morphological differences among emerald shiner (Notropis atherinoides) populations inhabiting the Niagara River, Lake Erie, and Lake Ontario. It was expected that emerald shiners inhabiting the two lakes would have more robust bodies and smaller heads, while river emerald shiners were expected to display more fusiform bodies with larger heads. The results of this study indicate that emerald shiners from Lake Erie and the Niagara River had a more robust form on average than individuals from Lake Ontario. Specifically, emerald shiners collected from Lake Ontario displayed more streamlined bodies and larger heads than emerald shiners collected from Lake Erie and the Niagara River. In addition, this divergence in body shape has apparently occurred despite the lack of distinct genetic differentiation as measured with microsatellite variation. Our results suggest that differences in water velocity alone may not be responsible for phenotypic variation in body shape among these emerald shiner populations, and other factors such as differences in prey or predator regimes are likely involved.     

峡江水利枢纽同江河防护区 地下水中铁离子运移规律分析

地下水铁离子浓度超标,将严重影响居民饮用水安全.认识地下水铁离子的运移规律,可为保护地下水饮用水源提供依据.本文基于溶质运移理论,建立同江河防护区内地下水铁离子运移概化模型,分析在同江河防护区与水库库区之间设置防护层与不设置防护层二种情况下铁离子的运移规律.分析表明,不设置防护层工况,铁离子浓度的变化呈现"钩状"形态发展,且运移速度快,扩散范围广;设置防护层工况,浓度的变化呈现"舌状"发展,运移速度、扩散范围远小于不设置防护层的情况;防护层会有效延缓铁的运移速度,限制运移范围,但不会从根本上解决铁的运移.     

水坝建设对滹沱河流域平原区地下水系统干扰结果分析

在分析大量地下水实测数据的基础上,研究了黄壁庄水库修建及坝基防渗处理后滹沱河流域平原区浅层地下水的响应变化,结果表明:水库修建后,滹沱河经历了由常年有水到间歇性过水直至常年干涸的过程;在地表水补给不断减少的条件下,滹沱河流域平原区的浅层地下水则随之经历了由浅到深的变化过程;河水流量相同条件下,同一位置处的浅层地下水升幅减小;河水位与浅层地下水位的吻合关系不复存在.     

Chinook salmon and rainbow trout catch and temperature distributions in Lake Ontario

We determined the distributions of Chinook salmon and rainbow trout by describing seasonal mean vertical and bathymetric catch depths from 1997 to 2005 using angler creel surveys. We developed and applied a cross-validated model of Lake Ontario temperatures to determine the water temperatures associated with these distributions. During April, Chinook salmon and rainbow trout were found nearshore at a bathymetric depth of 20 m. However, rainbow trout were caught at shallower vertical depths (4 to 6 m) than Chinook salmon (8 to 10 m). Both species moved deeper and farther offshore during May, June, and July. Vertical catch depths were similar, but rainbow trout were found further offshore (40 to 65 m bathymetric depth) than Chinook salmon (35 to 50 m bathymetric depth) during June, July and August. During September, Chinook salmon moved closer to shore (25 to 35 m bathymetric depth) and to shallower depths (9 to 12 m), consistent with river mouth staging associated with spawning. Rainbow trout remained offshore (45 to 60 m bathymetric depth) in deeper water (11 to 16 m). The species occupied significantly different spatial habitats during April, August, and September. Mean catch temperatures of both species were similar and increased seasonally to 13 to 14 °C during August and September. Rainbow trout were caught at cooler temperatures than Chinook salmon during June and July. The estimated temperature distributions agree with independent field studies but are different then previously assumed in bioenergetic models.