Weir Operation Research Articles

A Study on the Effect of Dredging and Operation of Weirs on Hydraulic Characteristics in Nakdong River

수리구조물의 효과적 운영과 홍수기 피해저감을 위해서는 하천수리특성에 대한 적절한 이해가 필수적이기 때문에 본 연구에서는 낙동강 수계 금호강 유입지점 하류를 대상으로 준설 및 수리시설물 운영에 따른 수리특성 영향을 분석하였다. 수리특성 분석을 위해 HEC-RAS 모형을 이용하였으며, 부정류 흐름 해석을 통해 흐름의 천이를 반영하고 수리시설물 운영을 위한 다기능보 제원을 적용하였다. 조도계수와 조고값의 관계, 정류와 부정류 흐름해석, 사업 전과 후 하천 단면 그리고 다기능보 운영에 따른 하천 흐름에 대해 다각도로 연구를 하였다. 낙동강 수계 주요 관심구간을 중심으로 급격한 지형변화 및 수리구조물 운영에 의한 홍수에 대비하고 주요지점별 유량 전달에 의한 홍수파에 대해 분석된 자료는 합리적인 하천관리를 위한 기초자료로 활용될 수 있을 것이다. It is essential to understand the hydraulic characteristics in accordance with the changes in the river environment and operating hydraulic structures for increasing flood-control capacity. The objective of this study is to analysis the effect of dredging and operation of weirs on hydraulic characteristics in Nakdong River(Seongju~Imhaejin). HEC-RAS model has been used to examine the hydraulic characteristics with considering the flow transition through the unsteady flow analysis and the information about the specifications of multi-functional weirs. The relationship between Manning n and roughness height k, the effect of weir installation and operation on the flow and stage, and the bed change resulted from the river treatment project have been examined by steady and unsteady flow analysis. It is expected that the result from this study can be the basic data for the river treatment and management.

Analysis of Hydraulic Passage Efficiency of Ice-Harbor Type Fishway for Flowrate Change

4대강에 설치된 16개의 다기능보에는 횡단구조물의 건설로 인한 생태계의 악영향을 최소화하기 위해 다양한 형태의 어도가 설치되어 있다. 달성보에 설치된 아이스 하버식 인공형 어도는 상류측에 가동보를 설치하여 하천유량에 상관없이 어도 내로 일정한 양을 통수시킬 수 있다. 어도의 유입유량은 내부의 수리적 특성과 밀접한 관계가 있으며, 이는 어류의 이동효율에 영향을 준다. 그러므로 어도의 이동효율을 효율적으로 관리하기 위하여 최적 유입유량 등의 다기능보 운영조건을 산정하는 것이 매우 중요하다. 본 연구에서는 낙동강 달성보의 아이스하버식 인공형 어도를 대상으로 FLOW-3D 모형을 이용하여 유량에 따른 수리특성과 이동효율을 분석하였고, 이동효율을 고려한 최적의 어도 가동보 유량 조건을 제시하였다. The various types of fishways are installed at the multi-functional weirs in the four major rivers to minimize the negative effect due to the construction of the transverse structures. The movable weir was installed at the upstream of the ice-harbor type artificial fishway of the Dalseong weir in the Nakdong river, which can control the fishway flowrate regardless of the river flowrate. The incoming flowrate to the artificial fishway is closely related with the hydraulic characteristics that dominate the fish passage efficiency. Thus, it is crucial to find out the weir operation rule for properly sustaining efficient fish-passage, such as the optimized flowrate. In this study, the FLOW-3D was used to analyze and compare the various hydraulic characteristics associated with the passage efficiency, based upon the given different flowrate, and subsequently provide the optimized flowrate for the fishway movable weir to maintain the best efficient flow condition for the fish-passage.

An easy to use calculation method for weir operations in controlled drainage systems

If operated appropriately, drainage systems may serve as vast reservoirs to retain or release water and solutes. This paper describes the hydraulic principles ruling the unsteady reaction of groundwater levels as related to drainage control operations. A set of governing equations suited to be implemented in computer codes was deduced focusing on non steady-state drainage, weir hydraulics, and effects of ditch maintenance. Based upon a simplified layout, two easy to handle computer codes were developed (MATLAB/Octave and Excel versions) enabling local engineers to assess system performance. Controlled drainage systems may be used to reduce leaching of agrochemicals from agricultural land and are valuable tools for preventive flood control. Controlled drainage may further support effective field operations necessary for crop production.

금강수계 댐과 보의 운영에 의한 하류 유황특성 연구

This study presents effects of downstream control point by coupled operation of dams and multi function weirs in the Geum River. Geum river basin that study area did authoritativeness high quality data to acquisition possibility. We applied the flow duration curve, flow regime coefficient, impounded flow index analysis to investigate the quantitative changes in natural flow regimes. In sphere that water supply is possible, this study applied believability that satisfy 95% at estimation year. Impounded flow index was calculated 0.292 by dam coupled operation and 0.297 by dam-weir coupled operation. The results indicate that the storage amount is increased by 29.7% as being added. Duration flow of downstream control point was improved because became coupled operation by regulation of dam and weir in the geum river.

Debottlenecking and Computational-Fluid-Dynamics Studies of High-and Low-Pressure Production Separators

Summary Efficient and effective oil/water/gas separation is required for success of many production operations. A major oil producer was experiencing difficulties with the oil/water/gas separation equipment on an offshore platform and improvements were required to meet both present and future production rates. Both high-pressure (HP) and low-pressure (LP) separators on a major oil production platform were studied to determine the design limitations for foamy service and basic sediment and water (BS&W) levels. Computational-fluid-dynamics (CFD) studies were completed to show the volumetric utilization and flow-pattern improvements made with the design changes. Both HP and LP separators showed substantial foam and poor efficiency because of poor inlet-device design, plugging, and other general vessel-design limitations. Debottlenecking efforts determined that, while the inlet device was somewhat ineffective, major improvements could be made from changes to perforated plate baffles, fluid-level adjustments, and weir placement and operations. CFD calculations performed on both vessels indicated similar problems. The perforated plate baffles with improper design lead to countercurrent flow through the baffles, making them less effective in flow control and distribution. Fluid-level settings for the weir height affected the velocity differences between fluid layers and contributed to promotion of recirculation within the vessel, which lead to low volumetric utilization. With adjustments to vessel internal equipment and changes to fluid-phase levels, CFD calculations showed that overall vessel volumetric utilization was improved by 22% for the HP vessel and by 38% for the LP vessel. CFD results also showed the changes to the flow patterns accompanying these improvements. Vessels with the proposed changes were operating effectively with substantially higher throughputs and meeting the expected BS&W levels for operations of the downstream oil-processing equipment. Details about the vessel internals, flow properties, and other changes required to accomplish these improvements will be discussed.

Regionalization of natural flow regime: application to environmental flow optimization at ungauged sites

AbstractIn this work we use the regionalization approach (RA) to derive the natural flow regime at an ungauged site. The derived natural flow regime, expressed by the regional cdf models of 32 indicators of hydrologic alteration (IHA) is used in the histogram matching approach (HMA) to seek the optimal environmental flows for a proposed multiobjective diversion weir in Taiwan. The results reveal that the outcomes associated with the planning constant scheme are significantly improved by the optimal time‐varying scheme. The histogram dissimilarities of 32 IHA associated with the planning scheme are consistently greater than those associated with the optimal scheme, especially for low‐flow IHA. Despite the inherent discrepancy between different approaches to generating flow data at the ungauged site, the optimal outcomes resulting from the RA‐based natural flow regime appear to be plausible and consistent with those reported in the previous work, thus validating the RA used in this work. We also explore the effect of weighting factors on the optimal outcomes. The results reveal that the weighting factor of the ecosystem needs objective dominates all optimal outcomes, while those of the agricultural demands and interbasin transfers objectives have minor effects on the optimal outcomes. The global optimal solution is obtained with a full or null weighting assigned to the ecosystem needs objective, while the least optimal solution is obtained as the interbasin transfers objective is given a null weighting and the agricultural demands objective is weighted more than the ecosystem needs objective. River managers and decision makers may select more balanced weir operation strategies based on the results presented in this work. Copyright © 2008 John Wiley & Sons, Ltd.

Pareto‐optimal solutions for environmental flow schemes incorporating the intra‐annual and interannual variability of the natural flow regime

The temporal variations of natural flows are essential elements for preserving the ecological health of a river which are addressed in this paper by the environmental flow schemes that incorporate the intra‐annual and interannual variability of the natural flow regime. We present an optimization framework to find the Pareto‐optimal solutions for various flow schemes. The proposed framework integrates (1) the range of variability approach for evaluating the hydrologic alterations; (2) the standardized precipitation index approach for establishing the variation criteria for the wet, normal, and dry years; (3) a weir operation model for simulating the system of flows; and (4) a multiobjective optimization genetic algorithm for search of the Pareto‐optimal solutions. The proposed framework is applied to the Kaoping diversion weir in Taiwan. The results reveal that the time‐varying schemes incorporating the intra‐annual variability in the environmental flow prescriptions promote the ecosystem and human needs fitness. Incorporation of the interannual flow variability using different criteria established for three types of water year further promotes both fitnesses. The merit of incorporating the interannual variability may be superimposed on that of incorporating only the intra‐annual flow variability. The Pareto‐optimal solutions searched with a limited range of flows replicate satisfactorily those obtained with a full search range. The limited‐range Pareto front may be used as a surrogate of the full‐range one if feasible prescriptions are to be found among the regular flows.

Steady flow regime for free overfall spillways. Influence of the ascending

This paper presents a study on the influence of the upstream quadrant of the spillway crest section, designed with equal geometry as that of the lower surface profile of a free flow over a sharp crested weir, on the discharge characteristics of a free overfall spillway. Geometrical deviations of the upstream quadrant from the standard design criteria as proposed by the U.S. Bureau of Reclamation, lead to variations in the flow discharge efficiency and on the upstream free surface elevations, i.e. on the reservoir free surface level. Starting with an analytical description of the weir problem, governing equations are derived, yielding the identification of three weir operation regimes, say, deep, intermediate or shallow weir; the first of them is the condition standing for many dam spillways. Experiments on the spillway crest profile under deep-weir operation conditions have been conducted, testing an evolution sequence of upstream quadrants ranging among simple geometrical shapes, with the standard design profile as one of them. As a result, a new upstream quadrant consisting of a 1:1 slope chamfer is proposed, since the hydraulic performance is found to be equal to or slightly better than the standard crest profile. An experimental program has also been carried out in order to determine safety limits regarding negative pressures on the spillway surface. From the standpoint of design, the suggested upstream geometry is easier to define, and cost-effective in terms of construction. A wider range of experimental set-ups, referred to model scales and flow conditions, should be conducted with the presented results as a starting point, in order to verify the adequate performance of the proposed design.

A dynamic corridor‐searching algorithm to seek time‐varying instream flow releases for optimal weir operation: comparing three indices of overall hydrologic alteration

AbstractA full range of natural flow regime has been widely recognized as a primary driving force for sustaining the integrity of a riverine ecosystem. Existing instream flow methods strive to assure a constant minimum flow but not the natural flow variability. We present in this paper a dynamic corridor‐searching algorithm to seek the optimal time‐varying scheme for instream flow releases. A compromise programming (CP) is employed to search the optimal solution of an objective function aggregating the ecosystem and human needs objectives. The ecosystem need objective is represented by an overall index of hydrologic alteration, which integrates 32 indicators of hydrologic alteration (IHA) derived from the range of variability approach (RVA). The human need objectives are expressed by shortage ratios for the agricultural and municipal water supplies. The proposed method is applied to a weir operation in Taiwan. Three approaches to evaluating the overall degree of hydrologic alteration (i.e., the three‐class, fuzzy‐based, and overall‐mean approaches) are compared here. The results show that the time‐varying schemes improve the human need objective, but only slightly deteriorate the ecosystem need objective. Such advantages increase with the time‐varying frequency. For the wet periods, smaller flow releases may be prescribed; for the dry periods, however, greater releases must be specified to secure a lower degree of overall hydrologic alteration. It is also revealed that use of the three‐class approach to evaluate the overall hydrologic alteration facilitates to eliminate highly altered IHA and maintain those low‐flow characteristics subtle to flow diversions. However, such outcomes are achieved at the cost of greater deficits for human water demands. Copyright © 2007 John Wiley & Sons, Ltd.

Tolerance of riverine plants to flooding and exposure indicated by water regime

Selected water regime indices are used to describe the tolerances to flooding and exposure of littoral and floodplain plants of the River Murray, South Australia. The cover and abundance of 26 perennial species were surveyed at 12 sites along a reach where water levels were influenced by weir operations. Six indices were measured: days when water depths were ≥0, 0–20, 20–60 and ≥200 cm; days when plants were exposed to ≥100 cm of water; and days of longest exposure to water. Ordinations of plant abundances were correlated with the frequency of flooding to 0–20 and 20–60 cm, and exposure to ≥100 cm. Five species clusters were apparent, these being common floodplain species (e.g. Muehlenbeckia florulenta), uncommon floodplain species (e.g. Eleocharis acuta), species from the infrequently flooded littoral (e.g. Bolboschoenus caldwellii), species from the permanently flooded littoral (e.g. Vallisneria americana) and widespread, common species tolerant to flooding and exposure (11 species, including Phragmites australis, Cyperus gymnocaulos and Bolboschoenus medianus). Half of the 26 species occurred in at least four of seven regimes suggested by cluster analysis of water regime indices, thus indicating a broad tolerance to flooding and exposure. Preferred water regimes are summarised using minimum and maximum values and quartiles for the six indices, and similarities between preferences are illustrated by a model based on minimum spanning tree techniques. Copyright © 1999 John Wiley & Sons, Ltd.

WATER SAMPLER AND FLOW MEASUREMENT FOR RUNOFF CONTAINING LARGE SEDIMENT PARTICLES

A flow-measuring and composite water-sampler system was needed for sampling sediment-laden flowscontaining large rock particles from strip-mine spoil erosion plots. The median percentage of soil particle sizes greaterthan 16 mm of the greater-than 2 mm fraction was 25%. A modified drop-box weir was used for measuring flows, and forproviding a well-mixed water and sediment flow that could be sampled. A diverter composite sampler was designed todivert the entire flow from a waste position to a sample position, and precluded the need to subsample (split) the sampledflows. Indoor testing of the sampler showed the sampler worked well with the modified drop-box weir. Field evaluationshowed the sampler and drop-box weir worked well under natural rainfall conditions. Recommendations for improvementin sampler and weir operation are given. Use of the sampler for other applications is also discussed.

On the improvement of chimney weirs

This paper is devoted to the improvement in the range of operation (linearity range) of chimney weir (consisting of a rectangular weir or vertical slot over an inward trapezium), A new and more elegant optimization procedure is developed to analyse the discharge-head relationship in the weir. It is shown that a rectangular weir placed over an inverted V-notch of depth 0.90d gives the maximum operating range, where d is the overall depth of the inward trapezoidal weir (from the crest to the vertex). For all flows in the rectangular portion, the discharge is proportional to the linear power of the head, h, measured above a reference plane located at 0.292d below the weir crest, in the range 0.90d less than or equal to h less than or equal to 7.474: within a maximum error of +/-1.5% from the theoretical discharge. The optimum range of operation of the newly designed weir is 200% greater than that in the chimney weir designed by Keshava Murthy and Giridhar, and is nearly 950% greater than that in the inverted V-notch. Experiments with two weirs having half crest widths of 0.10 and 0.12 m yield a constant average coefficient of discharge of 0.634 and confirm the theory. The application of the weir in the design of rectangular grit chamber outlet is emphasized, in that the datum for the linear discharge-head relationship is below the crest level of the weir.

Effects of water-level changes induced by weirs on the distribution of littoral plants along the River Murray, South Australia

In 1988 a survey was made of the River Murray between Locks 2 and 4 (153 river-km) to determine whether the distributions and relative abundances of littoral plants are influenced by water-level variations associated with weir operations. Of 20 recorded plant species, some, including Cyperus sp, and Myriophyllum verrucosue, occurred in regions downstream of each weir and hence were exposed to maximal variation in river levels. Others, notably Typha spp., favoured the regions above each weir, where levels are comparatively stable. The influences of physical channel characteristics such as bank slope, bank erosion and sediment composition and of other environmental factors were not clear. These effects may have been obscured by differences in the natures of the two pools and by a tendency for factors correlated with the water-level gradients to be 'reset' at each weir. Changes in the flow behaviour of the river since 1990 suggest that these survey data may later prove useful in evaluating the effects of high turbidities associated with regulated flows from the Darling River.

Environmental effects of flow regulation on the lower river Murray, Australia

AbstractBefore regulation flows in the lower Murray were highly variable, as for most rivers in semi‐arid regions. Major floods promoted large‐scale recruitment of flora and fauna in riverine and floodplain communities, and seasonal floods maintained lower levels of recruitment. The regime changed with the construction of 10 low‐level weirs in 1922–35, supplemented by the effects of dams in upstream areas. Flows remain variable but are much reduced in volume (about 44%). Low flows (100–300 Gl per month) have decreased five‐fold and moderate flows (500–1500 Gl per month) have increased two‐fold. Although the magnitude of peak seasonal flows has been diminished, the timing of flows is unaffected. The effects differ in the Valley and Gorge sections of the river, depending on local development of the floodplain and associated wetlands. The weirs have flooded once‐temporary wetlands and contributed to problems of salinization. Weir operations cause daily stage fluctuations that diminish downstream, and the channel is developing a stepped gradient as a consequence of active deposition and erosion. Regulation has limited exchanges between the river and its floodplain, changed the nature of the littoral zone and generally created an environment inimical to many native species, notably fish. The key to rehabilitation may be to restore a more natural balance of low and medium flows, but this may be unrealistic given the needs of irrigators and other water users. Despite its evolutionary history of wide spatial and temporal variation, the Murray river‐floodplain ecosystem evidently cannot accommodate these forms of disturbance.

An Investigation of Spinal Deformity of Trout ( Salmo sp.) in the Brule River, Wisconsin

An unusually high incidence of spinal deformity in migratory trout from the Brule River, Wisconsin, was investigated to determine its probable cause and extent. Incidence in rainbow trout ( Salmo gairdneri) and brown trout ( Salmo trutta) was determined by external examination and x-ray. The total incidence of deformity in x-rayed and externally examined lake-run rainbow trout was 50 and 26 percent, respectively. No vertebral anomalies were found by x-ray in 75 Brule River juvenile rainbow trout which had not yet emigrated to Lake Superior, nor in 25 lake-run rainbow trout from the French River, Minnesota. Examination of 25 lake-run brown trout from the Brule River showed external deformity (8 percent) and internal vertebral abnormalities (16 percent). The absence of spinal deformity in juvenile rainbow trout from the Brule River and in lake-run trout from the French River suggest that the electric lamprey control weir on the Brule was affecting fish which migrated downstream. The lower incidence of injury in brown trout reflects the difference in the time of their migration which was not coincident with weir operation. It is apparent that the electric lamprey weir has had a greater total impact on recruitment of trout to Lake Superior than previously thought.

Calibrated Weir operation.

The introduction of the Weir operation, which is simply a procedure calculated to reduce the width of the nostrils, has been a great boon in many cases toward the enhancement of the final nasal aesthetic result in nasal plastic surgery. However, since this technique is performed without any mechanical measurements and the surgeon relies exclusively on visual or empirical calculations, it has often produced nostril asymmetries. As a result of these nostril asymmetries, it is easily understandable why many skilled surgeons have abandoned the technique of the simple Weir operation. And, as a consequence, some patients consult other surgeons regarding the correction of their wide nostrils, since they are quite unhappy with the flairiness. They state that they had been informed that the reduction of the width of the nares was unnecessary and sometimes dangerous due to the possibility of a final result presenting nostrils of unequal size. In the