Showing papers on "Spillway published in 1997"

Downstream passage for salmon at hydroelectric projects in the Columbia river basin: Development, installation, and evaluation

Abstract: —A retrospective analysis of data on the relationship between turbine operating efficiency of Kaplan turbines and passage survival of salmonid smolts was performed. A review of a key report instrumental in establishing + 1% turbine efficiency rule for operating SnakeColumbia River hydroelectric stations found a weak association ( ) 2 0.112 r = but also misspecification of the turbine efficiency data. At four Snake-Columbia River dams, manipulative studies were performed to investigate the relationship between turbine performance and smolt passage survival using balloon-tag release-recovery method. At all four sites, peak observed survival did not coincide with peak turbine efficiency. The difference between peak survival and survival at peak turbine efficiency was as much as 3.4%. However, at three of the four sites, peak survival was within the + 1% peak efficiency operating rule. A meta-analysis using balloon-tag survival results from 11 different hydroprojects also found no association

Prediction of Effective Saturation Concentration at Spillway Plunge Pools

Abstract: Bubbles entrained in spillway plunge pools are subject to the hydrostatic force of the water column, increasing the pressure within the entrained bubbles. This phenomenon is important for the exchange of atmospheric gases such as nitrogen and oxygen, often causing dissolved gas supersaturation downstream of the plunge pool. A weighted average or effective bubble depth is introduced to predict more accurately gas transfer at spillways. A theory is developed for estimating the effective bubble depth given the spillway angle of inclination, velocity, and depth of flow at jet impact and tailwater depth. The relationship is fitted to dissolved oxygen and methane data previously reported by the authors and is successfully applied to four Bureau of Reclamation spillways for which both oxygen and nitrogen measurements were available.

Headcut advance prediction for earth spillways

Abstract: New technology for predicting the performance of earth (soil and rock) spillways has been developed through the joint efforts of the Agricultural Research Service (ARS) and the Natural Resources Conservation Service (NRCS). This technology has been computer coded, and the resulting computational model incorporated into NRCS software. As a part of evaluating the potential for spillway breach, one component of this model predicts headcut advance within the spillway. This component utilizes an energy-based parameter to describe the erosive attack and a headcut erodibility index to describe the resistance of the geologic materials to that attack. Headcut advance threshold and rate parameters were calibrated using data from field spillways that had experienced extreme flow events. The model was validated using data from additional field spillways. Results of the validation suggest that the model should provide a useful tool for current use, but that additional data and model refinement are needed.

Gas Bubble Reabsorption in Chinook Salmon: Pressurization Effects

Abstract: Gas bubble disease (GBD) can cause substantial morbidity and mortality of salmonids and other fishes residing in gas supersaturated water. The monitoring program for examining the prevalence of GBD in the Columbia and Snake rivers is only based on fish collected in the smolt bypass systems; fish that pass through the turbines, nagivation locks, adult fish ladders, or spillways are not sampled. The current monitoring program may underestimate the prevalence and severity of GBD because the high hydrostatic pressures experienced by the smolts as they pass through the smolt bypass system may cause rapid reabsorption of any gas bubbles that had formed upstream of the dam. A pressurization of 5 min to 30.5 m of head resulted in a substantial reduction in clinical signs of GBD in the fins, lateral lines, and gills of yearling spring chinook salmon Oncorhynchus tshawytscha. Clinical signs of GBD were lost most rapidly in gills, followed by the lateral line. The rate of bubble loss was much less for the p...

Comparison of Hydraulic and Hydrologic Routing on Three Long Reservoirs

Abstract: Outflow hydrographs for three dams with long lakes in narrow valleys were computed by both hydrologic routing (level-pool routing) and hydraulic routing. They were compared with three inflow hydrographs of different peaks with three unregulated ogee spillways of different capacities. In all these cases, the difference between outflow hydrographs was greatest at the peak value, growing larger as the spillway capacity became smaller, relative to the magnitude of the inflow hydrograph. The peak outflow by hydraulic routing was smaller than that by hydrologic routing for all the routing combinations, the difference varying between 2 and 11%.

Flow aeration at stepped cascades

Abstract: In storm waterways, at dam outlets and in water treatment plants, it is common to design stepped waterways and cascades nowadays. Stepped channel flows are characterised by a substantial flow aeration (i.e. 'white water') and there is presently little information on the air-water flow characteristics. The report presents experimental data for two flow regimes : nappe flow and skimming flow. New experimental data were obtained using a 25-m long stepped channel with a 3.4-degree slope. Flow was nappe flow without hydraulic jump : i.e., supercritical all along the cascade. The stepped cascade flow exhibited three-dimensional patterns : shock waves and sidewall standing waves. The experimental results suggest an analogy between supercritical flows at an abrupt drop (i.e. stepped channel) and at an abrupt expansion. Air concentration measurements were performed at various locations along the cascade. The results indicate that, in the same facility and for the same flow rate, the stepped cascade entrains two to three times more (undissolved) air than a smooth-chute flow. The laboratory findings are consistent with prototype observations at the Gold Creek dam spillway (Brisbane). Investigations by the authors into the air-water flow characteristics of skimming flow on stepped chutes have included the re-analysis of both model and prototype data. This has shown that the air-water flow properties exhibit similar features as high-velocity flows down smooth chutes. The effects of free-surface aeration on the flow properties are significant, as suggested first by CHANSON (1993). Altogether the rate of aeration is larger on stepped chutes than on smooth chutes. Stepped cascades are an excellent technique for re-oxygenating depleted waters and removing volatile organic compounds.

Filter and pump assembly for swimming pool with spillway

Abstract: The self-contained receiver (1) is connected to a panel (2) in one wall of the swimming pool which acts as a spillway. The receiver is more or less the same length as the panel and has a section to collect and store water from the pool. It is linked to a casing (4) containing a pump and filter which returns the water to the pool after treatment. The receiver is in two separate sections, an upper section (1a) connected to the spillway panel, and a lower (1b) which acts as a buffer tank, with a filter (3) between the two sections.

Risk Management at Wahleach Dam

Abstract: In a first-of-its-kind application, engineers used risk analysis to make event-driven design decisions to evaluate dam safety improvements at Canada's Wahleach Dam in British Columbia. In 1989, safety investigations revealed that the Wahleach Dam could not pass floods in excess of 25% of the probable maximum flood. The spillway could not safely discharge the pmf without the reservoir overtopping the dam. Also, erosion starting in the channel downstream of the spillway could undermine the spillway and breach the dam.

The influence of the Mosul dam on the bed sediments and morphology of the River Tigris

Abstract: The Mosul dam and its flow regulating scheme have been constructed 60 km north of Mosul city. A minimum discharge of 330 m3s"' is usually released from the dam. The reach of the River Tigris below the dam (about 8.3 km long) investigated in this study serves as a small reservoir for the regulating scheme. The effects of high velocity discharges from the bottom outlet and spillway structures on channel morphology were monitored for two periods using fixed cross-sections. The characteristics of the bed sediments were studied using 32 samples. The results showed that large amounts of sediment (average 0.5 m) were eroded from the bed of the river during a 10 month period. The bed sediments were characterized by a sand:silt:clay ratio of 42.4:50.2:7.4 respectively and it is believed that lining of the bed of the river downstream of the bottom outlet and spillway would reduce the scour downstream.

Soft-base low-weir spillway dam energy dissipation structure

Abstract: An energy-sinking structure of overflow dam for soft-foundation weir features that an energy-sinking plate with holes whose hole area ratio is 20-30% is built at a downstream position a certain distance apart from the planar dam and the water stream passed throug the plate can form a mixed flow state of bottom flow and bailed flow, which are mixed and generate friction between them to consume energy. Its advantages include reducing wave height by more than one time and flushed depth by 60% and saving investment by 10%.

Orifice flow in a gated spillway

Abstract: Theoretical value of discharge for orifice flow in a gated Ogee spillway was computed using U.S.B.R. and Sinniger equations. Experimental values were found to be substantially different from the theoretical values. Pressure correction factor found to be a function of both head and gate openings, was calculated by least square curve fitting. Discrepancy between theoretical and experimental values of discharge were reduced substantially with the introduction of the pressure coefficient Cp.

Hydraulic performances of skimming flow over stepped spillway

Abstract: Hydraulic performances of skimming flow over stepped spillway was studied by means of hydraulic model experiment. The stepped spillway is a modification of the WES (Waterways Experiment Station) standard spillway. The main objective of the experiment was to study the performances of skimming flow over stepped spillway, which include the skimming flow regime, the flow depth on the spillway , the effect of air en-trainment and the energy dissipation. Presented in this paper, the experimental results indicated that the stepped spillway is more effective at dissipating energy, the dissipation ratio decreases with increasing discharge, and the free surface air entrainment on stepped spillway occurs much more upstream than on smooth spillway.

Red River Waterway, Lock and Dam 3, Report 2: Navigation Alignment Conditions, Hydraulic Model Investigation.

Abstract: : Lock and Dam 3 is located on the Red River, in a cutoff channel between 1967 river miles 140 and 142, and about 53 channel miles above John H. Overton Lock and Dam. The lock and dam will be the third lock in a series of five locks and dams designed to furnish the required maximum lift of 141 ft to provide year-round navigation on the Old and Red River Waterway from the Mississippi River to Shreveport, LA, a distance of 236 miles. The principal structures are an 84-ft-wide by 685-ft-long lock, a spillway containing six 60-ft-wide by 42-ft-high tainter gates, and a 315-ft-long fixed-crest weir adjacent to the gated spillway. The dam provides a navigation pool that extends upstream to Lock and Dam 4. The dam is operated to maintain a navigation pool of el 95.0 at the dam (all elevations (el) cited herein are in feet referred to the National Geodetic Vertical Datum). A fixed-bed model reproduced about 3.5 miles of the Red River and adjacent overbank from about 13,500 ft upstream to about 4,800 ft downstream of the dam to an undistorted scale of 1:100. Since Lock and Dam 3 was to be constructed in an excavated channel bypassing the natural river channel, it was important that the alignment of the channel and the arrangement of the lock and dam be satisfactory for navigation. The model investigation was concerned with evaluation of navigation conditions for proposed lock designs and development of modifications required to ensure satisfactory navigation conditions. The study identified any needed modifications to the navigation channel alignment, guard wall lengths, or remedial structures. Results of the investigation revealed that a system of structures was required to eliminate adverse current patterns and establish satisfactory navigation conditions for tows entering and leaving the upper lock approach.

Physical model study of the proposed spillway for cedar run site 6, fauquier county, virginia

Abstract: A two-dimensional physical model study was conducted of the Cedar Run Site 6, Fauquier County, Virginia, proposed roller-compacted concrete stepped spillway and stilling basin. The study was conducted to evaluate the hydraulic performance of the stepped surfaces, effect of entrance abutments, adequacy of the stilling basin, and performance of a flip bucket. The proposed spillway is 106.7 m (350 ft) wide; the PMF peak discharge is 27.34 m3/s/m (294 ft3/s/ft); and the stilling basin design discharge is 18.31 m3/s/m (197 ft3/s/ft). A smooth chute was tested to permit comparison of the energy dissipation for the stepped surface with a conventional concrete surface. The steps were effective in dissipating energy. At the stilling basin design discharge, the energy dissipation with the steps was 33% compared to 7.2% with the smooth surface. The stilling basin was very effective in dissipating energy at 18.31 m3/s/m (197 ft3/s/ft) and smaller discharges and results showed it can be reduced 20 to 25% in length without negatively affecting performance. The flip bucket appears to be a viable alternative for use instead of the stilling basin. Square abutments are recommended as the better performance with the rounded abutments does not offset the greater difficulty of construction and the increased cost for rounded abutments.

Repair, Evaluation, Maintenance, and Rehabilitation Research Program: Applications of Roller-Compacted Concrete in Rehabilitation and Replacement of Hydraulic Structures.

Abstract: : Although roller compacted concrete (RCC) was primarily developed for rapid, economical construction of new dams, the case histories reported herein show that it has been used extensively in remediation projects at existing hydraulic structures. These case histories were compiled to illustrate the versatility of RCC in repair, rehabilitation, and replacement of hydraulic structures. RCC applications include increasing existing spillway capacities; construction of new service, emergency, and combination spillways; repair of spillways, outlet tunnel, and lock floor; overtopping and scour protection for rock fill timber crib and embankment dams; seismic strengthening; increasing sliding stability; breach repair; and replacement of rock fill timber crib, earthfill embarkment, and concrete dams. The basic properties of RCC (high strength, low permeability, and high erosion resistance compared to nonstabilized materials) together with low cost, rapid and relatively simple construction methods, and proven performance make it particularly attractive for remediation of hydraulically deficient embankment dams. Depending on the complexity of placement and total quantity of material required, the cost or RCC typically ranges from 25 to 50 percent less than conventionally placed concrete. These savings are primarily the result of reduced costs for forming, placing, and compacting RCC. Also, the reduced construction time typical of RCC contributes significantly to its lower cost. Rapid construction is a major advantage in repair of hydraulic structures where delays and shutdowns can cause significant losses to the user. Also, rapid construction minimizes the impact of bad weather and reduces the potential for adverse environment impact in the vicinity of project sites.

An adjustable air-regulated siphon spillway.

Abstract: The Pergau hydroelectic project was built as a design and construct contract in Northern Peninsular Malaysia by an Anglo-Malaysian joint venture with funding assistance provided by the British Government. A regulating pond providing 1.5 x 10 6 m 3 of live storage was constructed at the tailrace outfall to accept peak generation flows and release them back into the river in a controlled manner. Discharge from the pond is normally regulated by two hydraulicallt activated radial gates acting on signals from the project's automatic control system. An air-regulated siphon with a design capacity of 140 m 3 /s was provided to protect the embankment crest from overtopping in the event of gate malfunction or station generation flow continuing for longer than programmed. The spillway was developed with novel features in an extensive series of laboratory trials. Provision was made in the prototype to adjust the air intake area to compensate for scale effects in the model study and to ensure that the required head discharge relationship is obtained.

Risk Model for the Safety Evaluation of Dam and Levee: II. Application

Abstract: The risk assessment model for dam and levee is applied to a river where two adjacent dams are located in the upstream of the watershed. "A" dam is proven to be safe with 200-year precipitation and unsafe with PMP condition, whereas "B" dam to be safe with 200-year precipitation and PMP condition. The computed risk considering the uncertainties of the runoff coefficient. initial water depth and relevant data of the dam and spillway turn out to be equivalent results in Monte-Carlo and AFOSM method. In levee risk model, this study addresses the uncertainty of water surface elevation by Manning's equation. Monte-Carlo simulation with the variations of Manning's roughness coefficient is calculated by assuming that it follows atriangular distribution. The model can be used for preparing flood risk maps, flood warning systems, and establishing nation's flood disaster protection plan.

Special Concrete for Ankang Dam

Abstract: Modern construction of concrete dams requires numerous innovative solutions both in design and construction techniques. Research and development and application of new materials are necessary to meet the special requirements of dam design and construction, and to reduce project costs. Novel solutions demand new types of materials. Development and application of new materials for dam structures in turn promote further research into innovative designs and construction. This complimentary process of research and application is the power which pushes dam construction techniques forward. In light of this process, this article describes low-heat, small-expanding cement concrete (LHSECC) and its application to the spillway of China's Ankang Dam in order to meet the special construction requirements.

Questioning the need for spillways

Abstract: In many dam projects, particularly those with large surface reservoirs or those suffering rare flash flood conditions with high peaks, it is often difficult to identify straightforward criteria with which to determine spillway dimensions and dam height. Indeed, two projects pose the question whether spillways are always entirely necessary for all types ofdam construction.

Flood spillway device in porous water intake equipment

Abstract: PROBLEM TO BE SOLVED: To obtain a flood spillway device with low turbidity by a porous water intake equipment of a dam. SOLUTION: A slant gutter pipe 2 is provided to a porous water intake equipment along the surface of a dam body of a dam, a large number of water intakes 6A with gates are provided to the slant gutter pipe 2, at the same time, it is connected to a bottom gutter pipe 4 passing through horizontally the lower part of the dam body, and the lowest stage of water intake 6N among the water intakes is used for a flood spillway device. The highest stage of water intake 6A is larger than twice as large as opening area of the lowest stage of water intake 6N to use it as a second flood spillway device. By the constitution, water discharged by the second flood spillway device can be reduced to low turbidity, and a water purification burden in the case of flooding is not imposed on water utilization side such as public water supplies, etc.

Red River Waterway, Lock and Dam No. 4. Report 2: Navigation Alignment Conditions, Hydraulic Model Investigation.

Abstract: : Lock and Dam No. 4 is the fourth lock in a series of five to be constructed on the Red River Waterway from the vicinity of Old River to Shreveport, LA. Lock 4 is located in a cutoff canal on the left descending bank about 169 post project river miles above the mouth of the Red River. The principal structures include an 84- by 785-ft lock, a gated spillway containing five tainter gates, and a hinged crest gate 100 ft wide. The fixed bed model reproduced about 3.5 miles of realigned river channel and adjacent overbank area at an undistorted model scale of 1:100. The model investigation was concerned with determining the effects on navigation through the study reach for the proposed design and developing modifications required to the design that would provide satisfactory navigation conditions.