River-lake System Research Articles

Downstream changes in phytoplankton composition and biomass in a lowland river–lake system (Warnow River, Germany)

To determine longitudinal changes in phytoplankton composition and biomass in the Warnow River (Germany), single water parcels were followed during their downstream transport in August and October 1996 and April 1997. In summer, the phytoplankton assemblage was dominated by centric diatom and cyanobacteria species. Stephanodiscus hantzschii, Pseudanabaena limnetica, Planktothrix agardhii and Aulacoseira granulata var. angustissima were the most frequent species. In autumn, small centric diatoms dominated the whole river course. Irrespective of the season, in the fluvial lakes of the upper river, a substantial increase of phytoplankton biomass was observed. Shallow upstream river stretches were associated with large biomass losses. In the deep, slow flowing lower regions, total biomass remained constant. Longitudinal changes in biomass reflected downstream variations in flow velocity and river morphology. Cyanobacteria, cryptophytes and diatom species were subjected to large biomass losses along fast flowing, shallow river sections, whereas chlorophytes were favoured. Diatoms and cryptophytes benefited from low flow velocity and increased water depth in the downstream river. Changes in water depth and flow velocity have been found as key factors that cause the longitudinal differences in phytoplankton composition and biomass in small rivers.

Planning Objectives and Thinking for Taihu Lake Water Pollution Prevention

According to the social and natural conditions of Taihu Lake Basin, the planning objectives and some ideas for water pollution prevention in Taihu Lake and its surrounding river-lake system are proposed.;According to the social and natural conditions of Taihu Lake Basin, the planning objectives and some ideas for water pollution prevention in Taihu Lake and its surrounding river-lake system are proposed.

Organic Matter Budgets for Streams: A Synthesis

Organic Matter Budgets for Streams: A Synthesis

Distribution of phytoplankton in a river-lake system with strong seasonal discharge variations in Central India

Distribution of phytoplankton in a river-lake system with strong seasonal discharge variations in Central India

Origin and succession of phytoplankton in a river-lake system (Spree, Germany)

Origin and succession of phytoplankton in a river-lake system (Spree, Germany)

Modeling oil spills in a river—lake system

A general model shell, ROSS3, is developed for simulating oil spills in complex river systems using techniques which have not been previously exploited in oil spill models. ROSS3's new approach has several advantages over the approach to model oil spills in the past: (a) The use of a time-varying boundary-fitted coordinate system that allows accurate accounting for complex river/lake boundary as well as the river boundary changes as its water levels fluctuate; (b) The ability to confine two-dimensional hydrodynamic computations to a limited river reach; (c) The ability to interactively layout the channel networks for setting up the model, define extra cross sections to increase the accuracy if needed, in addition to the traditional data entry and visualization interfaces. ROSS3 is a two-layer two-dimensional oip spill model that can simulate the mechanism of advection, horizontal diffusion, mechanical spreading, shoreline deposition, evaporation, dissolution, vertical mixing, resurfacing and sinking. In ROSS3 spilled oil may be a surface slick or suspended oil droplets, or a combination of both. Both free surface and ice cover conditions can be simulated. The flow of conditions can be varied and the unsteady flow model can be run within ROSS3 to simulate the flow conditions in both the river and the lake. The ice conditions can be added or removed from the model input using easy interactive procedures.

The dynamics and retention of phosphorus in lentic and lotic patches of two river-lake systems

The dynamics and retention of phosphorus in lentic and lotic patches of two river-lake systems

Continuous and discontinuous processes of transport and transformation of matter along the river-lake system

Continuous and discontinuous processes of transport and transformation of matter along the river-lake system

Water Column Methylmercury in the Wabigoon/English River–Lake System: Factors Controlling Concentrations, Speciation, and Net Production

Ten years after major releases of inorganic mercury from a chloralkalai plant were sharply reduced, methylmercury (MeHg) levels remain markedly elevated in waters in most of the Wabigoon River system downstream of Dryden, Ontario, Canada. The water column appears to be a very important site for methylation and demethylation. In water, MeHg and inorganic Hg appear to be in quasi equilibrium, as the MeHg: total mercury ratio is independent of contact time with sediments, the atmosphere, and the theoretical residence time of waters. The MeHg: total Hg ratio increased with distance downstream of Dryden, but MeHg always averaged less than 10% of the total Hg concentration. MeHg was mostly soluble, as defined by field centrifugation. Net production of MeHg appeared to be directly related to the amount of MeHg required to establish and maintain equilibrium conditions with inorganic Hg. A model is developed which adequately describes water column MeHg concentrations. Considerations of the model suggests different restoration strategies for different parts of the Wabigoon/English River–Lake system.

Distribution of PCB congeners in sediments of the Otonabee River-Rice Lake system, Peterborough, Canada

Samples of sediment from a river-lake system near Peterborough, Canada were analyzed for PCB congeners. The results show that sediment in Little Lake, within the city of Peterborough, is acting as a source of contamination for downstream regions. The consistency of congener patterns throughout the system suggests that PCBs are transported downstream primarily in association with suspended sediment.

Methyl Mercury Levels in a Polluted Prairie River–Lake System: Seasonal and Site-Specific Variations, and the Dominant Influence of Trophic Conditions

The Moose Jaw River – Qu'Appelle River system of southern Saskatchewan (Canada) and its chain of hypertrophic lakes are polluted with mercury (Hg) and sewage from urban point-sources. Analysis of water, suspended particles, and bottom sediments sampled at different localities at different times of year (from April to November) revealed that methyl mercury (CH3Hg+) levels are not controlled by the total abundance of inorganic Hg but are highly dependent on the abundance of organic matter and planktonic algae. CH3Hg+ levels were anomalously high in the presence of sewage effluents and associated algal blooms and at times of reduced river discharge, when the flushing and dilution of nutrients were minimal. At elevated organic carbon, nitrogen, and chlorophyll concentrations, CH3Hg+ levels were high even if inorganic Hg levels were low; but at low organic carbon, nitrogen, and chlorophyll concentrations, CH3Hg+ levels were low even if inorganic Hg levels were high. The results are ascribed principally to stimulation of the activities of Hg-methylating microorganisms by organic nutrients from algae and sewage. The possibility of amerliorating the Hg problem by reducing nutrient pollution is discussed.

The English–Wabigoon River System: I. A Synthesis of Recent Research with a View towards Mercury Amelioration

Over a 3-yr period, teams from the federal Department of Fisheries and Oceans, the federal Department of the Environment, and the Ontario Ministry of the Environment researched the mercury pollution problem of the English–Wabigoon River system, north-western Ontario, Canada. Mercury methylation and bioaccumulation were occurring mainly in the water column and surface layers of the sediments. Most mercury in the system was buried below the surficial sediments and probably does not contribute substantially to present mercury bioaccumulation. Movement of mercury between geochemical and biological compartments was rapid within the water column and surface sediments. Also, substantial amounts of inorganic and methyl mercury were transported down the river–lake system, having been released from stretches of river upstream of Clay Lake and deposited onto the surfaces of downstream lake sediments. Because of the constant movement of mercury into the water and onto downstream surface sediments, mercury amelioration procedures should concentrate on reducing bioaccumulation rates from both the water column and surface sediments. Treatments such as a single addition of clean clay to the surface sediments of lakes would probably be unsuccessful as long as significant downstream movement of mercury continues. Semicontinuous resuspension of bottom sediments followed by downstream deposition and/or elevation of the selenium concentration in biota by low-level additions of selenite were found to be the two most promising amelioration strategies. Both of these approaches would treat the problem in the water column and surface sediments. We consider advantages and disadvantages of these ideas and some needs for further research.

Real Time Simulation of Conductivity in River-Lake Systems

Conductivity is modeled in real time in a natural water system using the finite section method. Dispersion coefficients are estimated using methods available in the literature. Calibration is performed together with sensitivity analyses. Small scale effects are defined by a dye study. The resultant model is eventually used in the construction of system models describing the transport and fate of various pollutants in the Ford Lake - Melleville Lake (Mich.) System.

Methyl mercury formation and distribution in a polluted river—lake system: the effect of environmental variables, and implications for biological uptake and lake restoration

(1981). Methyl mercury formation and distribution in a polluted river—lake system: the effect of environmental variables, and implications for biological uptake and lake restoration. SIL Proceedings, 1922-2010: Vol. 21, No. 2, pp. 1114-1115.

Sources of heavy metal contamination in a river-lake system

Sediments of the Wabigoon River, Ontario, are polluted with Hg from an industrial source at Dryden. Downstream from Dryden the river flows first through Clay Lake and then through Ball Lake. Hg, Cu, Zn, Cd and Fe concentrations in sediments of both lakes are correlated with organic C, but Hg content per unit concentration of organic C is higher, and increases more steeply with Organic C, in Clay Lake than in Ball Lake; in contrast, the Cu, Zn, Cd, and Fe concentrations per unit concentration of organic C are nearly the same in both lakes. These results substantiate the conclusion that the Hg originated at a point upstream from the lakes and tended to accumulate in Clay Lake on its way downstream, whereas the other metals were leached into the two lakes from diffuse sources in the surrounding terrain. Accumulation of river-borne organic pollutants in Clay Lake was also demonstrated. Application of the methods employed to the general problem of recognising and locating element anomalies is discussed.

Heavy metal pollution in the sediments of the Coeur d'Alene River, Idaho

Analysis of sediment samples collected from the Coeur d'Alene River in northern Idaho, USA, indicates that the main stem and the south fork of the river are contaminated with heavy metals (Cd, Pb, Mn, and Zn) from the local mining operations. Laboratory experiments indicate that these metals in the sediments can be leached and reach saturation concentrations in water in a relatively short period of time. The rate of leaching of heavy metals with distilled water appeared to follow first-order kinetics. The saturation concentrations of Mn and Zn in water reached ppm levels from the leaching process. Cadmium and Pb are much less soluble relative to Zn in the sediments. The high concentrations of heavy metals in the sediments are a source of contamination that should be considered for the water quality management planning of the Coeur d'Alene River-Lake system.

Interpretation of Polymodal Sediments

Commonly used statistical treatments of grain size distributions are inappropriate if the sediment in question is polymodal. 190 sediment samples from a river-lake system were analyzed by one or more sizing methods. Cumulative probability plots revealed most samples to be polymodal with inflection points at approximately 2 ø, 5 ø, and 8.5 ø. Partitioning of representative curves into overlapping lognormal populations was accomplished by utilizing a standard graphical technique. Samples from the river consisted of two populations: medium sand (population A) with a mean of 1.25 ø and fine sand (population B) with a mean of 3.8 ø. Shear velocities calculated from velocity-depth data suggest that the coarse population would be transported as bedload and the finer one as suspension. Samples from the lake lack the medium sand population, but could be partitioned into 3 overlapping populations: fine sand (population B) with a mean of 3.8 ø, silt (population C) with a mean of 5.8 ø, and clay (population D) with a mean of 10.3 ø. Population B apparently moves as suspension in the river but represents traction transport in the lower energy lake environment. Population C and D are interpreted as suspension populations. This technique of partitioning polymodal grain size curves should prove an important tool in the understanding of sedimentary processes and interpreting environments of deposition.

Ancestral Niagara River drainage: Stratigraphic and paleontologic setting

The modern Niagara River was initiated as a multi-outlet river-lake system following the last ice retreat from the area about 12,300 yr B.P. This system extended from Early Lake Erie to the contemporaneously formed Glacial Lake Iroquois in the Ontario basin. The last major ice advance and one subsequent glacial oscillation associated with the ice retreat are recorded in sequences of glaciolacustrine deposits and till along the present Gorge wall and within older bedrock spillways. Dated wood overlying Iroquois silts and till within the Lockport spillway, east of Niagara, suggest that the multi-outlet (Lake Tonawanda) phase of the drainage ceased about 10,900 yr B.P. with concentration of the outflow, and hence major gorge recession, at Lewiston. Radiocarbon analysis of mollusks from river gravels at the top of the Niagara Gorge at Whirlpool Park indicate that cataract recession from Lewiston to this site of intersection with the much older buried St. Davids Gorge occurred after 9800 yr B.P. Lake Tonawanda persisted near the present site of Niagara Falls until about 1,000 yr ago; however, dated mollusks imply that deposition here was interrupted by intense scouring shortly before 3800 yr B.P., which may have been a response to the closing of the North Bay outlet of the upper Great Lakes and consequent large increase in discharge through Lake Erie. Mollusks which occur in the ancient Niagara River gravels are well preserved and distinctly zoned. The Lake Tonawanda fauna, heretofore undescribed, includes about 15 species, all of which are extant in the region.