Structural Connectivity of Sediment Affected by Check Dams in Loess Hilly-Gully Region, China

Check dams play an irreplaceable role in soil and water conservation in the Chinese Loess Plateau region. However, there are few analyses on the connection between check dams and the downstream channel and the impact on structural connectivity and sediment interception efficiency. Based on a field survey, this study classified the connection mode between check dams and the downstream channel, and the actual control area percentage by discharge canal in dam land was used to quantitatively evaluate the degree of the structural connectivity of sediment between the check dam and the downstream channel. The analysis results show that the connection mode can be divided into eleven categories with different structural connectivity. The different connection modes and its combination mode of check dams and downstream channels in dam systems have a large difference, and the structural connectivity of the dam system is less than or equal to that of the sum of single check dams in a watershed. The degree of structural connectivity of a dam system will be greatly reduced if there is a main control check dam with no discharge canal in the lower reaches of the watershed. Compared with a single check dam, the structural connectivity of a dam system is reduced by 0–42.38%, with an average of 11.18%. According to the difference in connection mode and structural connectivity of check dams and dam systems in the four typical small watersheds, the optimization methods for connection mode in series, parallel and hybrid dam systems were proposed. The research results can provide a reference for the impact of a check dam on the sediment connectivity and the sediment interception efficiency in a watershed and can also guide the layout of a dam system and the arrangement of drainage facilities.

Impact of the conjugation construction of the apron section structure with the tailrace on water flow kinematics

Purpose: to determine the impact of the conjugation construction of the apron section structure with the downstream on the water flow kinematics with the use of the performed field and laboratory studies data and their processing. The relevance of this issue lies in the fact that in case of unsatisfactory conjugation of the apron with the discharge canal slopes, negative phenomena are formed in it in the form of faulty currents, whirlpools at the canal slopes, etc., affecting the stability of the apron conjugation, creating a threat to the stability of the structure itself. Materials and Methods: the materials were the data of field studies carried out on a number of hydraulic structures of irrigation systems in Stavropol Territory, as well as on models in laboratory conditions with the identification of the impact of conjugation structures of the apron with the discharge canal slopes on the water flow distribution in tailrace. The measurement of velocities in natural conditions was carried out by observing the integrating floats movement in the discharge canals. On the model, the velocities were measured using a miniflowmeter, and the trajectories were traced using luminous floats. Results: graphs of the dependence of the sought factors on the known parameters were built on the basis of the information obtained, and using the methods of mathematical statistics, the coefficient of the conjugation of the apron structure with the canal slopes in tailrace was obtained. The result of the research was an empirical dependence for determining the flow velocity along its dynamic axis, which is the scientific novelty of the research performed. Conclusions: the type of conjugation of the apron of the structure with the distribution canal slopes has a great influence on the hydraulic flow regime on the apron and in the discharge canal. Each type of conjugation creates a sudden expansion of the flow on the apron, which affects the value of the average flow velocity along the dynamic axis, on which the deformation of the discharge canal depends.

Use of CFD Modeling for Designing Intake and Discharge Structures in a Discharge Canal

This paper presents a computational fluid dynamics (CFD) modeling approach for designing intake and discharge structures in a discharge canal for nuclear and fossil power plants. It discusses how the CFD models are developed, what types of results can be obtained from the CFD modeling study and how the results are used for developing designs of the intake and discharge structures. The pros and cons of the CFD modeling method for this type of application are also discussed. Intake and discharge structures for a “Helper Cooling Tower South” will be added to the discharge canal of the Crystal River Energy Complex (CREC). The CFD modeling was used to confirm suitable locations for the new intake and discharge structures to minimize potential recirculation and potential loss of cooling tower efficiency, and to evaluate the erosion of the banks on the north and south side of the canal due to the flow from the discharge structure. The CFD model was developed using FLUENT for the existing and future configurations of the discharge canal that consists of the existing intake, discharges, and the new intake and discharge structures. The CFD modeling runs were performed to investigate three-dimensional flow patterns, velocities and temperatures in the discharge canal under current and future operating conditions. Current and future conditions refer to those before and after installation of the Helper Cooling Tower South Intake and Discharge structures, respectively. Comparing the CFD results (streamlines, temperature and velocity distributions, etc.) for the future conditions to those for the existing conditions, the locations and designs of the new intake and discharge structures were assessed and developed. This study demonstrates that the new intake is not impacted by the new and existing discharge structures, and the existing intake will perform similarly as it performs before the construction of the new intake and discharges. The study also identifies some sections of the canal banks and bottom that may need to be protected from erosion due to the impacts of the high velocity water from the discharge structures.

Effects of a freshwater canal discharge on an ovoviviparous isopod inhabiting an exposed sandy beach

The present study evaluates the effects of an artificial freshwater discharge (Canal Andreoni) on the ecology of the ovoviviparous isopod Excirolana armata. Bimonthly, 17 environmental variables plus isopod abundance, biomass, fecundity, growth and mortality were compared between three sites: ‘Barra del Chuy’ (undisturbed), at 13 km from the canal, ‘Coronilla’ (moderately disturbed), at 1 km, and ‘Andreoni’ (grossly disturbed), at the canal mouth. Environmental (salinity, slope, beach width, and swash width) and some biological (isopod abundance, biomass and growth rates) variables significantly decreased towards Canal Andreoni. Salinity was the most important explanatory variable of spatial trends in isopod biomass. However, the reproductive output, fecundity, survival and individual weight were not affected, suggesting that E. armata is regulated by density-dependent and abiotic factors operating together: the former were more intense on undisturbed conditions, whereas the latter prevailed in impacted ones. Internal brooding counteracts the effect of fresh water, which explains the lack of effect of environmental harshness on reproductive traits.

EAST RIVER BATTLE FOR SHEEN: SKIMMING AN OIL SHEEN IN A 3- TO 5-KNOT CURRENT

ABSTRACT This paper explores the challenges involved with the recovery of oil from a discharge canal with limited access and high relative currents. In March 1999, a sheen was observed in the cooling water discharge canal of Consolidated Edison's 2.5-million kilowatt generating station in Queens (New York City), New York At the time the sheen was discovered, the entire station had been shut down for several months for a maintenance outage. As the tide rose and fell in the East River, into which the discharge canal emptied, the oil sheen moved in and out of a 1,000-foot long tunnel connecting the generating station to the canal. The major challenges to the recovery and removal of the oil sheen were: (1) the low over head of the discharge tunnel and canal support girders, which prevented getting a skimmer into the tunnel and canal; (2) the high discharge rate of the station's cooling water pump; and (3) skimming the sheen in a 3-to 5-knot current. Consolidated Edison is a member of Clean Harbors Cooperative, L.L.C, which was brought in to remove the sheen. This was accomplished utilizing two JBF Scientific DIP Belt Skimmers, which were set up parallel to the current flow, and deflection booming.