Spillway Opening Research Articles

Numerical Modeling of Transport of Condensed Moisture Generated by No. 1 Spillway Operation at the Boguchanskaya Reservoir During Winter of 2012

The primary purpose the investigations described in this paper was acquisition of preliminary predictions of undesirable phenomena caused by the effect of the water-air cloud generated by the No. 1 spillway on the most threatened areas in the lower pool of the Boguchanskaya HPP. The roofs of the building housing the hydraulic drives and machine gallery, the front wall of the hydraulic-drive building, which faces in the direction of the lower pool, and the abutments bounding the toe basin of the No. 1 spillway are referred to as such areas.

Forebay hydraulics and fish entrainment risk assessment upstream of a high dam in China

Hydropower operations can induce significant variation of velocity field upstream of intakes and may lead to fish entrainment into turbines. In this study, the flow fields upstream of a high dam in China under different intake and spillway operation patterns were investigated theoretically using potential flow solution and computational fluid dynamic modeling, and experimentally in a 1:50-scale physical model. Flow fields induced by multiple intakes and by a line sink tends to be the same at about two times of the distance of adjacent operating intake upstream of the intakes. Different operation scenarios were analyzed to improve the general understanding of characteristics of upstream flow and to reduce the risk of fish entrainment. The extent of the risk zone for fish entrainment defined by specified thresholds of velocity and acceleration indicate that smaller water depth over submerged intake means a higher risk of fish entrainment.

A Paddlefish Entrained by the 2011 Mississippi River Flood: Rescue, Recapture, and Inferred Swim Speed

Abstract We observed a large adult Paddlefish entrained from the Mississippi River through the Bonnet Carre spillway, south Louisiana, which was injured and underweight. We captured, measured (23 metrics), and tagged the fish. After it had spent a week at large on the floodway, we recaptured and released it back into the Mississippi River. The specimen was re-captured eight months later in northern Mississippi, 627 km upriver from where it was released. Distance traveled and water velocities in the river indicate that the fish was traveling at least 90–197 cm/s for prolonged periods, equivalent to gross speeds of 77–170 km/d. This incident suggests that a large entrained fish, trapped for several days in a hyperthermic and hypoxic habitat, can be viable when returned to the river. It also demonstrated that rescue efforts could reduce impacts of spillway operations to fish populations, and that comprehensive field assessment of fish morphology can be benign t o fish.

Wild Turkey Movements During Flooding After Opening of the Morganza Spillway, Louisiana

Abstract The opening of the Morganza Spillway in Louisiana on 18 May 2011 to relieve historic flooding along the lower Mississippi river subsequently inundated thousands of acres of bottomland forest in the Atchafalaya basin. Since 2001, we have conducted Meleagris gallopavo silvestris (Eastern Wild Turkey) population ecology research on the Sherburne Wildlife Management Area, located approximately 30 km south of the Morganza spillway. In expectation of the Morganza spillway opening, between 11 and 14 May, we captured and fitted 5 (1 M, 4 F) adult Eastern Wild Turkeys with µGPS transmitters to monitor turkey response to basin flooding. By 19 May 2011, our study area was inundated with >3 m of flood waters, and remained completely inundated until 11 June 2011. Via radio-telemetry, we confirmed one female was depredated immediately before flood waters inundated our study site, and one female survived and reached dry ground created by receding water on 16 June. A second female lived 21 days and made circuito...

Mississippi River channel response to the Bonnet Carré Spillway opening in the 2011 flood and its implications for the design and operation of river diversions

► We examine impacts of the record Mississippi River flood of 2011. ► We examine the effects of removing 20% of the river flow through a river diversion on channel hydrodynamics. ► We provide data and analysis that will improve design and operation of river diversions. The large Mississippi River flood in 2011 was notable in the lowermost Louisiana, USA reach for requiring operation of several flood control structures to reduce stress on artificial levees: the largest diversion went through the gated Bonnet Carré Spillway, which was opened for 42 days in May and June. The removal of approximately 20% of the total flood discharge from the river provided an opportunity to examine the impact of large water diversion on the sediment transport capacity of large rivers. Boat-based, acoustic and water and bed sampling surveys were conducted in the Mississippi River channel adjacent to the Spillway immediately prior to the opening of the structure, at full capacity, and immediately following (June 2011) and 1 year after (June 2012) closure. The surveys were designed to examine (1) elevation change of the channel bed due to scour or aggradation of sediment, and (2) suspended and bedload transport variability upriver and downriver of the Spillway. The results indicate that approximately 9.1 million tons of sand were deposited on the channel bed immediately downriver of the water exit pathway and extending at least 13 km downriver at a rapidly and progressively reducing magnitude per river kilometer. The surficial deposit was of finer grain size than the lateral sand bars in the channel upriver of the structure. We argue the deposit was largely delivered from suspension derived from the observed deflation of lateral bars upstream of the diversion point, rather than from sand arriving from the drainage basin. Approximately 69% of the 2011 flood deposit was removed from the 13 km downstream reach between June 2011 and June 2012. We conclude that the source of the channel deposit was the reduction in stream power, and, thus, in the sediment transport capacity of the Mississippi, associated with the water withdrawal. The re-entrainment of this material in the following flood year indicates the system rapidly re-establishes an equilibrium to pre-opening conditions. Future diversions in the river for coastal restoration will have to address this issue to maintain a deep draft navigation channel in the Mississippi River.

Nitrate Flux into the Sediments of a Shallow Oligohaline Estuary during Large Flood Pulses of Mississippi River Water

Lake Pontchartrain is a large, oligohaline estuary located in coastal Louisiana that receives episodic diversions of nitrogen-rich Mississippi River water via the Bonnet Carré Spillway to alleviate flood threats to the city of New Orleans. These events may be linked to expressions of eutrophication, and it is therefore important to investigate pathways of nitrate (NO) loss. Nitrate flux into the sediments of Lake Pontchartrain was investigated using two independent methods: (i) simulating high NO flood events under aerobic and anaerobic incubations in intact sediment cores collected during 2010 and (ii) in situ field measurements of the vertical profiles of dissolved inorganic nitrogen species at the sediment-water interface during the 2011 Bonnet Carré Spillway opening. Mean rates of NO flux into sediments based on mass transfer in intact cores collected in 2010 and in situ porewater measurements in 2011 were -17.4 and -1.4 mg NO-N m d, respectively, for water column NO concentrations observed in situ in 2011. During the laboratory incubations, there was no significant difference in NO flux between oxygen treatments. We estimate that NO flux into sediments accounted for up to 3.1% (309 Mg NO-N) of water column NO loss during the 2008 Bonnet Carré Spillway event. Sediment characteristics, field measurements, and results from the laboratory experiment suggest that denitrification is the primary pathway for NO reduction. Even though there is significant NO reduction occurring in Lake Pontchartrain sediments during Mississippi River diversion events, this pathway of NO loss from the water column plays a relatively minor role in the transformation of the very large amount of NO received during these times.

ANALYSIS OF PLUNGE POOL SCOUR HOLE FORMATION BELOW A CHUTE SPILLWAY WITH FLIP BUCKET USING A PHYSICAL MODEL

Plunge pool scouring due to water jet impingement from flip bucket spillways is a major concern for stabilization of hydraulic structures and their downstream channel. The objectives of this study are to select an appropriate movable riverbed material for reproducing scour hole in the physical model and to analyze the characteristics of its formation using the selected material. The whole tasks were carried out using Nam Ngum 3 Spillway Physical Model constructed with an undistorted scale of 1:75. Different types of movable riverbed material were tested and the most appropriate one was then selected in order to conduct the scour study. Based on a set of criteria, cohesive movable riverbed material of Sand (40): Cement (1): Water (5) was found to reproduce more reliable scour hole than non-cohesive material of 25 mm graded gravel. Utilizing the selected material, the overall model test demonstrated that spillway operation, river morphology and natural topography of the plunge pool are the main factors governing irregular trend of scour development. Scour hole tends to develop toward the left bank and the maximum scour depth, about 74 m deep below the original riverbed, is located approximately 252 m downstream of the spillway’s bucket lip.

Modelling Spillway Flow Conditions at Złotniki Storage Reservoir on the Kwisa River

Abstract An important part of the work connected with planning modernization of outlet devices of Złotniki storage reservoir on the Kwisa river was numerical modelling of flow conditions in the flume of the side-channel spillway. The modelling was preceded by the analysis of operating principles of such a device and performing analytical calculations that defined the spillway capacity ability as a function of the required water levels in the reservoir and the conditions of water flow through the flume that are significant to spillway operation. The results of the numerical modelling performed pointed to the evident need to reconstruct this device, guaranteeing exploitation safety of the reservoir, mainly in view of the computational discharges, exceeding considerably the nominal capacity ability of the reservoir’s outlet installation in the existing constructional state.

Hydraulic operating conditions of the gravity-flow discharge run of the deep construction spillways at the bureya hydroproject and their damage

This paper is devoted to a critical problem — analysis of the operation of deep construction spillways (DCS) with a gravity-flow discharge run. As results of operation of this type of structure both abroad and in our country (Krasnoyarsk and Zeya hydroprojects) indicate, cavitation failures have occurred in a number of these structures. In this paper, it is noted that the publication of inspection data has not always been sufficiently analyzed in depth, and does not consider results of experimental investigations; this has led to superfluously categorical conclusions concerning structural deficiencies of DCS. Experience acquired with the design and operation of tubular spillways within the body of concrete dams is examined above all in this paper. Causes of damages sustained by DCS at the Krasnoyarsk hydroproject are revealed, and it is emphasized that water had been passed entirely successfully after repair work. Abrief description of the DCS at the Bureya hydroproject is given. It is noted that the difficult financial and climatic conditions of its construction have influenced the quality of the concrete surfaces of the spillway, and the rate of the dam’s installation. Results of laboratory investigations of the DSC at the Bureya hydroproject and monitoring of the hydraulic operating conditions of their run are examined. Conclusions concerning causes of abrasive and cavitation damages sustained during passage of high-water in 2004 – 2006 are drawn on the basis of analysis of these data.

Ground stability assessment using geophysics and field observation techniques

Inspection of ground stability is necessary to ensure the suitability of an area for engineering and environmental applications. In a certain area, a combination of measurement of cracks and seismic refraction method can provide a better knowledge of the future behavior of the area in terms of its stability. In this reconnaissance study, seismic refraction method and continuous measurements of crack displacement were conducted to detect the stability of an area that lies on the downstream side of the Mosul dam, and to establish its possible mechanisms of failure. The study shows two types of instability, namely, fall and sliding, and these were due to heavy rainfall, springs, and spillway operation.

Effects of freshwater input on nutrient loading, phytoplankton biomass, and cyanotoxin production in an oligohaline estuarine lake

Pulsed river water events can increase nutrient levels potentially translating into enhanced primary production, phytoplankton community shifts, and bloom formation. The Bonnet Carre Spillway is a managed river diversion which can be used to redirect a significant amount of Mississippi River water into Lake Pontchartrain, reducing the risks of flood in the downstream communities during runoff seasons. We investigated nutrient enrichment and consequent changes in phytoplankton biomass, including toxic species in Lake Pontchartrain during and after a 1-month Bonne Carre Spillway opening in 2008. Water samples were collected along a 30 km transect. A freshwater plume was found to have formed by the strong river input that had limited mixing with the lake during the opening. The plume and lake water gradually mixed together after the Spillway was closed, indicated by the reduction of the horizontal salinity gradient. The river pulse increased the lake nitrate and dissolved reactive phosphorus concentrations to more than five times the lake background in the plume stations. Nutrient concentrations decreased rapidly after the Spillway closure as the plume dissipated. Diatoms and chlorophytes dominated the system during the opening. After the Spillway closure, there was a shift over time from diatom dominance to toxic cyanobacteria dominance that corresponded to more stable, warmer, and nutrient-limited water conditions. Associated toxins were present and varied over time and space. Further research on the phytoplankton assemblages on the lake is needed in subsequent, non-Spillway opening years to evaluate the impact of river water pulses on the development of these toxic cyanobacterial blooms.

Winter operation of spillway structures at hydroelectric power plants

Basic problems of reliability assurance at hydroelectric power plants under the winter conditions prevalent in Siberia, the Far East, and mountainous region are touched upon. Data presented in the paper are based on results of scientific observations of spillway operation at various hydroprojects during the winter. Major attention is focused on analysis of the winter operation of the spillway at the Sayano-Shushenskaya HPP. Basic positions with regard to evaluation of the possibility and assurance of the operation of spillway structures during winter should be considered for hydroprojects already built, and those under design.

Plume and bloom: effect of the Mississippi River diversion on the water quality of Lake Pontchartrain

The opening of the Bonnet Carré spillway to prevent flood threat to New Orleans in April 2008 created a sediment plume in the Lake Pontchartrain. The nutrient rich plume triggered a massive algal bloom in the lake. In this article, we have quantified the spatio-temporal distribution of the plume (suspended solids) and the bloom (chlorophyll-a (chl-a)) in the lake using remotely-sensed data. We processed the Moderate-resolution Imaging Spectroradiometer satellite data for mapping the total suspended solids (TSS) and chl-a concentrations. An existing algorithm was used for estimating TSS whereas a novel slope model was developed to predict the per-pixel chl-a concentration. Both algorithms were successful in capturing the spatio-temporal trend of TSS and chl-a concentrations, respectively. Algal growth was found to be inversely related to TSS concentrations and a time lag of ∼45 days existed between the spillway opening and the appearance of the first algal bloom at an observation location.

Injury and Mortality of Juvenile Salmon Entrained in a Submerged Jet Entering Still Water

AbstractDevelopment of more eco‐friendly hydroelectric facilities requires better understanding of the biological response of juvenile fish when they migrate through the turbines and other downstream passage facilities. Juvenile fall Chinook salmon Oncorhynchus tshawytscha were exposed to turbulent shear flows in a laboratory by using a fast‐fish‐to‐slow‐water mechanism in which test fish were carried by the fast‐moving water of a submerged turbulent jet into the slow‐moving water of a flume. Fish were released at six nozzle velocities: 6.1 (reference control), 12.2, 15.2, 18.3, 21.3, and 22.9 m/s. The onset of minor and major injuries occurred at 15.2 and 21.3 m/s, respectively. The acceleration magnitude threshold (m/s2) of major injury for the fast‐fish‐to‐slow‐water mechanism in this study was found to be significantly higher than that for a slow‐fish‐to‐fast‐water mechanism used in a previous study in which test fish were introduced into a turbulent jet from slow‐moving water through an introduction tube placed just outside the edge of the jet. Fish responded differently and sustained different injuries when they were subjected to turbulent shear flows under the two exposure mechanisms. This information is applicable to the design and operation of turbines and spillways because these two tested mechanisms simulate the severe hydraulic events fish usually experience during passage at hydropower dams.

Lessons Learned from a Decade of Assessment and Restoration Studies of Benthic Invertebrates and Submersed Aquatic Vegetation in Lake Pontchartrain

Abstract Studies of Lake Pontchartrain benthic invertebrates and submersed aquatic vegetation (SAV) from 1996 through 2005 provided the opportunity to determine community responses to severe disturbances including: recovery from shell dredging; effects of anoxia and hypoxia from saltwater intrusion; the 1997 Bonnet Carre Spillway opening; a prolonged drought resulting from an El Nino Southern Oscillation; and effects of Hurricane Katrina. We included reviews and updates of our recently published work, an integrated analysis of findings, and restoration recommendations. During this decadal study there were no prolonged periods of “normal” conditions. Instead, benthos and SAV were experiencing or recovering from significant temporal disturbances. This made it difficult to use the abundance of a particular set of organisms at a point in time to evaluate habitat quality or restoration success without considering past disturbance effects. Benthos species diversity and the relative abundance of stress tolerant ...

Water quality and phytoplankton communities in Lake Pontchartrain during and after the Bonnet Carré Spillway opening, April to October 2008, in Louisiana, USA

The Bonnet Carre Spillway, located 28 miles northwest of New Orleans, was constructed in the early 1930s as part of an integrated flood-control system for the lower Mississippi River system. From 11 April to 8 May 2008, Mississippi River water was diverted through the spillway into the 629-square-mile Lake Pontchartrain, which is hydraulically connected to the Gulf of Mexico. On 8 April, prior to the opening of the spillway, water-quality instruments were deployed and recorded hourly measurements of water temperature, dissolved oxygen, specific conductance, pH, and nitrate. Discrete water-quality and phytoplankton (algae) samples were collected in Lake Pontchartrain from 8 April to 3 October 2008 to assess the water-quality nutrient enrichment effects of the diversion on the lake. The maximum influence of river water in the southern portion of the lake was captured with continuous (hourly) monitoring of nitrate concentrations, and field measurements such as of specific conductance during the critical period in late April to early May. By late May, the deployed instruments had recorded the arrival, peak, and decline of selected constituents associated with the freshwater influx from the Mississippi River/Bonnet Carre Spillway diversion. The continuous monitoring data showed the short-term interactions of high-nitrate, low-specific conductance river water and low-nitrate, high-specific conductance lake water. The phytoplankton community composition, as an indicator of water quality, illustrated an extended response from the river water evident even after the continuous and discrete samples indicated that the lake had returned to pre-diversion conditions. The initial phytoplankton community response to nutrient increases was related to accumulations of diatoms. During periods of low nutrient concentrations, accumulations of blue-greens occurred by July and August. As blue-green algae cell densities and biovolumes increased in the summer, so did the species richness of blue-green algae, particularly the harmful algae bloom taxa. Cell densities and biovolume of the phytoplankton lake indicator taxa Skeletonema costatum, Anabaena sp., and Cylindrospermopsis raciborskii were highest and dominated the diatom and blue-green algae communities during the period of most river water influence on the lake and immediately following the freshwater inflows. The dominance and recession of these indictor taxa reflect the dramatic changes that occurred in the phytoplankton community in response to an increase in nutrient-rich freshwater from the diversion into the lake, and not normal seasonal phytoplankton compositional differences. Water-quality data indicated a gradual reversion to pre-diversion lake conditions by June to July, but shifts in the phytoplankton composition were still evident through August 2008. Observations from this study were similar to results from previous studies of Mississippi River/Bonnet Carre Spillway diversion opening in 1997.

Effects of the 1997 Bonnet Carré Spillway Opening on Infaunal Macroinvertebrates in Lake Pontchartrain, Louisiana

Abstract The Bonnet Carre Spillway was constructed in 1931 to divert floodwater from the Mississippi River into Lake Pontchartrain, an oligohaline estuary near New Orleans, Louisiana. The spillway was opened from March 17 through April 18, 1997. Infaunal macroinvertebrate population, surface and bottom salinity, and dissolved oxygen data were examined to determine the effects of this diversion. These data were obtained from November 1996 through November 1998 from five sites on an east-to-west transect across Lake Pontchartrain. A community composed of oligohaline taxa persisted during the freshwater period, but changes in dominance, and to a lesser extent composition, occurred over time and among sites. There was a pronounced spatial effect related to the distance of the sites from the spillway and from tidal passes. Based on decreases in species diversity (H′), abundance, and the number of taxa, it appears that the opening had a deleterious impact on the benthos. The cause of these changes cannot be att...

Numerical modeling of the formation and transport of condensed moisture in the lower pool of a hydroproject during the operation of spring-board spillways

A model of three-dimensional forced convection and transport of condensed moisture in the lower pools of hydroprojects is developed.

Numerical modelling of turbulent flow through spillway with gated operation

AbstractNumerical simulation of rapidly varied, free surface turbulent flow over spillway with the existence of both sub‐critical and super‐critical flow regimes is a challenging task. Vertical acceleration plays a dominant role in the spillway flows. This paper describes the formulation and development of a numerical model for flow over the spillway. The computer model is developed using the finite volume method based on weakly compressible flow equations and large Eddy simulation (LES)‐based turbulence model. The model is applied to a real world case study of partial gate operation of sluice spillway to investigate the hydraulic characteristics by simulating the velocity distribution, pressure distribution and discharge characteristics. Numerical modelling of sluice spillway is complicated because both moving free surface region and fixed conduit pressure flow in the sluice barrel are present. The numerical model results are compared with the physical model study. The simulated results are in close agreement with the measured values. Copyright © 2007 John Wiley & Sons, Ltd.

Is fish passage technology saving fish resources in the lower La Plata River basin?

Over 450 dams have been constructed in the upper Paraná River basin in Brazil during the past 40 years. River regulation by these dams is considered a primary factor in the reduction of fish diversity and depletion of migratory species. In contrast to the upper Paraná Basin, only two large dams (both with upstream fish passage) have been constructed in the lower La Plata River basin. Fishery managers in the lower basin are concerned that existing and planned dams will further deplete populations of migratory fish species that constitute important recreational and commercial fisheries as has occurred in the upper basin. We assessed the sustainability of fisheries in the lower basin in the face of increased river regulation by using literature information to describe the efficiency of the fish passage systems used to mitigate river regulation impacts on fisheries. Our analysis shows that fish passage systems at both lower basin dams, Yacyreta and Salto Grande, fail to transfer sufficient numbers of upstream migrants to sustain populations of migratory species. Fish passage efficiency of target species in the fish elevators at Yacyreta is less than 2%. Fish diversity in the fish elevators is low because about 85% of the fish belong to only three non-migratory species (Pimelodus maculatus, Oxydoras kneri and Rhinodoras dorbignyi). Large migratory species targeted for passage rarely comprise even 5 % of the fish number in the passage system. The two Borland locks at Salto Grande Dam cannot dependably pass large numbers of migratory species because passage efficiency is dependent upon interactions of powerhouse and spillway operation with tailrace elevations. Most species in the Borland system were either a small catfish (Parapimelodus valenciennis) or a engraulid (Lycengraulis grossidens). Again, the targeted migratory species were not abundant in the passage system. We conclude that existing fish passage technology in the lower basin is inadequate and that improved fish passage designs are required to conserve migratory species. These designs must be based on integrated information from geomorphology (habitat), natural fish behavior, fish swimming capabilities, and detailed population studies.