Spillway Height Research Articles

Optimizing geometric dimensions and vortex breaker of morning glory spillway using genetic algorithm

This research aims at optimizing geometric dimensions and vortex breaker of morning glory spillway using a genetic algorithm (a case study of a physical model of San Louis Forebay Dam in California, USA). In this research, two types of morning glory spillway, one with a smooth and the other with a stepped body, with different vortex breakers and different arrangements, are experimentally tested and modeled. In addition, a physical model, similar to the model of San Louis Forebay Dam located in California in the USA, was selected. This research optimized discharge coefficient and morning glory spillway height parameters using a genetic algorithm. The results show that tunnel radius parameters and inner and outer radii of the spillway crest, radius 90-degree bend, the length of the tunnel, and the height of the spillway crest can be optimized based on the total volume of the spillway using a genetic algorithm. In addition, the new values obtained for these parameters, if used, lead to a decrease equal to 39% of the volumes of concreting, which, in turn, reduces the building costs of the physical model.

Discharge coefficients for ogee spillways

Abstract Discharge over an ogee weir is related to the length of the weir, upstream total head above the weir crest and the discharge coefficient. The discharge coefficient is influenced by several factors; in this study, some parameters that influence discharge coefficients of ogee weirs are investigated. These factors include: the weir upstream slope, apron elevation, and downstream submergence. In this regard, ogee weir physical models were fabricated. These models comprise: an ogee weir with a vertical upstream face, ogee weirs with inclined upstream faces (18, 33, and 45 degrees), ogee weirs with downstream apron thicknesses of 3, 5, 7, and 10 cm in free flow and an ogee weir with a vertical upstream slope under submerged-flow conditions. Results show that for all ogee weirs, the discharge coefficient (C) increases with increasing P/He, and then remains constant (P is the spillway height and He is the head above the weir crest). The value of the discharge coefficient decreases from 2.25 in free-flow conditions to 2.15 with submerged-flow conditions. For a constant head over the ogee weirs (He), the discharge coefficient decreases with increasing downstream apron elevation and submergence. The relative discharge coefficient shows a constant trend initially, with increasing hd/He, then later shows a decreasing tendency (hd is the difference between the downstream head and the ogee spillway crest). The threshold value for submergence ratio (hd/He) is 0.75 in the ogee weir in this study. With increasing submergence ratio from 0.75 to 1, the relative discharge coefficient (Cs/C0) decreases from 0.88 to 0.24.

Water Storage in Dry Riverbeds of Arid and Semi-Arid Regions: Overview, Challenges, and Prospects of Sand Dam Technology

Augmenting water availability using water-harvesting structures is of importance in arid and semi-arid regions (ASARs). This paper provides an overview and examines challenges and prospects of the sand dam application in dry riverbeds of ASARs. The technology filters and protects water from contamination and evaporation with low to no maintenance cost. Sand dams improve the socio-economy of the community and help to cope with drought and climate change. However, success depends on the site selection, design, and construction. The ideal site for a sand dam is at a transition between mountains and plains, with no bend, intermediate slope, and impermeable riverbed in a catchment with a slope greater than 2°. The spillway dimensioning considers the flow velocity, sediment properties, and storage target, and the construction is in multi-stages. Recently, the failure of several sand dams because of incorrect siting, evaporation loss, and one-stage construction were reported. Revision of practitioners’ manuals by considering catchment scale hydrological and hydrogeological characteristics, spillway height, and sediment transport are recommended. Research shows that protected wells have better water quality than open wells and scoop holes. Therefore, the community should avoid open defecation, pit latrines, tethering of animals, and applying pesticides near the sand dam.

Designing conduit sabo dam series as a debris flow protection structure

A high potential area for landslides was identified upstream of the Air Beras River on Bukit Beriti Besar which was feared to generate debris flow through the Air Beras River. One of the preventive efforts that can be conducted for debris flow is the sabo dam. This study aims to design a series of conduit sabo dams and evaluate the structure stability according to SNI 2851:2015 and Technical Standards and Guidelines for Planning and Design of Sabo Structures (JICA, 2010). By using the design discharge of debris flow of 120 m3/s, the velocity of 5.06 m/s, and the inclination of the riverbed of around 6.16°, the spillway height of the Sabo Dam 1 was determined to be 3 m, while the spillway height of Sabo Dam 1 was 2 m. The Sabo Dam 1 has a height of 10 m and a width of 30 m with a total manageable volume of 49,600 m3 while the Sabo Dam 2 has a height of 10 m and a width of 45 m with a total manageable volume of 91,500 m3. The safety factors of the sabo dam in the debris flow condition were 2.14 for overturning, 1.50 for sliding, and 5.74 for bearing capacity. Based on the result, the conduit sabo dam series effectively controls the destructive power of debris flow.

Assessing the impact of climate change on rainwater harvesting in the Oum Zessar watershed in Southeastern Tunisia

Climate change is believed to have a large impact on water resources system both globally and regionally. It has become a major global issue, especially in developing countries because these are most affected by its impacts. Rainwater harvesting techniques offer an alternative source of water and represent specific adaptive strategies to cope with water scarcity within future climate change. Studying the impact of climate change on rainwater harvesting techniques, however, is difficult, because the general circulation models (GCMs) which are widely used to simulate scenarios of future climate change operate on a coarse scale. We estimated the impact of climate change on water availability at the watershed level by downscaling precipitation and temperature from the GCMs using a statistical downscaling model. A water harvesting model then assessed the performance of the rainwater harvesting techniques for the Oum Zessar watershed in southeastern Tunisia under current climatic conditions and scenarios of future climate change. Annual temperature tended to increase and precipitation tended to decrease. These changes of climatic variables were used in the water harvesting model to simulate future water availability. Changing the directions of water flow between sub-catchments in combination with changing the spillway heights strongly affected the performance of rainwater harvesting under the scenarios of future climate, resulting in a sufficient water supply for 92% of all sub-catchments, compared to 72% without these changes.

Effect of downstream apron elevation and downstream submergence in discharge coefficient of ogee weir

ABSTRACT Discharge coefficient in ogee spillways is essential factor for producing discharge–head relationship. Discharge coefficient is relevant to the downstream water level submergence and downstream apron elevation. In this study, both submergence and apron effect are investigated using experimental data. To mathematical expression for discharge coefficient, the gene expression programming (GEP) and multiple regression technique were applied using dimensionless parameters. Results showed that GEP is superior to the regression analysis in predicting of discharge coefficient (C s). Performance criteria of GEP are R 2 = 0.967, RMSE = 0.041 and MAE = 0.035. For facility, some design examples are presented that show application of the proposed GEP equation and eliminates linear interpolation using existing graphs. The threshold value for submergence (S = h d/h) is 0.8 in this study. That is for S < 0.8, the discharge coefficient is approximately independent from the tail water elevation. But for S > 0.8, the discharge coefficient is dependent to tail water elevation and reduces rapidly with increasing of submergence. With increasing of submergence from 0.32 to 1, relative discharge coefficient (C s/C0) decreases from 1 to 0.47. Moreover, C s is dependent on P d (vertical distance between spillway crest and downstream apron invert) and P (ogee spillway height).

EVALUATION OF DYKES AS WATER HARVESTING SYSTEM IN WADI SHEBITY WEST MERSA MATROUH, NORTHWESTERN COASTAL ZONE – EGYPT.

The main objective of this research is evaluating dykes as rain water harvesting activities to maximize rainwater utilizing in drainage basins in the northwestern coast of Egypt which receive amount of water and have a population growth and agricultural activities. Wadi bed cultivation is the water harvesting system in the chosen wadi. It is usually done through construction of stone dykes to store surface runoff coming from tableland in the south, the main problems associated with this type of water harvesting are unequal water distribution through the wadi, where less runoff water reaches the wadi beds in downstream, with the result that downstream crops become increasingly water-stressed, moreover storing volume of water higher than fig water requirement the results in delaying agricultural development. To maximize rainwater use, 50 stone dykes of 50 cm spillway height were evaluated in term of water distribution efficiency and the percentage of stored water volume to plant water volume requirement/season. And depending on the storage capacity of dykes, fig water requirement and the runoff volume of the average season of rainfall data for 17 years from October to march (one season) estimated by Soil Conservation Service (SCS) method and Geographical information system (GIS) The results of the present study show that wadi Shebity watershed receives average annual rainfall volume of 435217 m3, 121922 m3 from it by percentage of 28 % run on ground while the residue percentage of 72 % distribute among evaporation and infiltration in soil, 118590 m3 of surface run off by percentage of 97 % stored by dykes by water distribution efficiency of 3, 12, 100 % for rainfall of 12, 20 and 53 mm respectively, and 3332 m3 by percentage of 3 % is lost in the sea. The percentage of the stored water volume to the cultivated areas water volume requirements is 118 % with difference of 18168m3. The study reveals that the end of wadi shibty is in safe from flood hazard, where the runoff coming from the table land at the south is stored completely by dykes even with the maximum rainfall of 53 mm. The spillway height of 50 cm is not suitable to distribute surface runoff through the wadi for low and medium rainfall which is more frequency, moreover stores water volume higher than the fig water requirement with 18168 m3. Further the methodology followed in this study can be applied in all other wadis watersheds but designing new or modification of the existing water harvesting system of dykes will depend on its watershed area and its physical Characteristics, rainfall, the cultivated land area and crop/fruit type. The present study reaches out for some recommendations to maximize rainwater utilizing

Performance of Retarding Basin in Flood Disaster Risk Mitigation in Welang River, East Java Province, Indonesia

Flood phenomenon caused by high rainfall and sea tides on a watershed seat the tidal area, including the Welang River, commonly occur and the number of events is increasing. Construction of retarding basin is one of flood risk mitigation efforts by reducing the flood peak discharge. Assessment of flood management in Welang River was conducted with hydrology and hydraulic approaches, by using the Hydrologic Engineering Centre-Hydrologic Modelling System (HEC-HMS) 4.0 and Hydrologic Engineering Center–River Analysis System (HEC-RAS) 5.0.3 software. The hydraulic simulation consists of 4 scenarios. Scenario 1 was the current condition, while scenario 2, 3, and 4 were the retarding basin construction with one side spillway, one on the upstream (River Station (RS) 7400), on the middle (RS 6970), and on the downstream (RS 6590), respectively. The height variation of side spillways are 3 m and 4 m. Flood routing simulation result showed that the existing river channel condition could not accommodate of 2-year flood and 10-year flood, which caused peak discharge of 497.7 m3/s and 794.9 m3/s. At the RS 6590, the maximum runoff height of 2-year and 10-year flood were 0.66 and 1.02 m, respectively. Under the 2-year return period of flood, the discharge reduction caused by the retarding basin at control point RS 5341.4 (Karangketug Village), were 39.63 m3/s, 31.83 m3/s, and 41.93 m3/s, respectively for scenario 2, 3 and 4 with the 3 m side spillway height and 14.71 m3/s, 16.76 m3/s, and 13.74 m3/s, respectively for scenario 2, 3 and 4 with the 4 m side spillway height.

Computational Fluid Dynamics Modeling of Flow over Stepped Spillway

In present paper, the computational fluid dynamics (CFD - program Flow-3D) was used to analyze and study the characteristics of flow energy dissipation over stepped spillways. Three different spillway heights () (15, 20 and 25cm) were used. For each one of these models, three numbers of steps (N) (5, 10 and 25) and three spillway slopes (S) (0.5, 1 and 1.25) were used. Eight different discharges ranging (600-8500cm³/s) were passed over each one of these models, therefore the total runs of this study are 216. The energy dissipation over these models and the pressure distribution on the horizontal and vertical step faces over some models were studied. For verification purpose of the (CFD) program, the experimental work was conducted on four models of stepped spillway and five different discharges were passed over each model. The magnitude of dissipated energy on models was compared with results of numerical program under same conditions. The comparison showed good agreement between them with standard percentage error ranging between (-2.01 - 11.13%). Thus, the program Flow-3D is a reasonable numerical program which can be used in this study.Results showed that the energy dissipation increases with increased spillway height and decreased number of steps and spillway slope. Also, the energy dissipation decreases with increasing the flow rate. An empirical equation for measuring the energy dissipation was derived using the dimensional analysis. The coefficient of determination of this equation (R2) equals 0.766.

A water harvesting model for optimizing rainwater harvesting in the wadi Oum Zessar watershed, Tunisia

Rainwater harvesting (RWH) techniques have been adapted in arid and semi-arid regions to minimise the risk from droughts. The demand for water has increased but water resources have become scarcer, so the assessment and modelling of surface water related to RWH in catchments has become a necessity. An understanding of the hydrological processes at the sub-catchment level is generally lacking, and little attention has been given to the assessment of RWH after implementation. The objective of this study was to develop a simple but generally applicable water-harvesting model and test it at sub-catchment level to evaluate and optimize the performance of RWH under different design and management scenarios. The model was applied to rainfall data for 1980–2004 in 25 sub-catchments of the watershed of Wadi Oum Zessar (south-eastern Tunisia). The performance and analysis of RWH in three types of years (dry, normal, and wet) are presented and discussed. This study emphasises the advantages of simulating long-term water balances at the sub-catchment level for improving our understanding of hydrological processes in the RWH system and provides several solutions for optimizing RWH performance in various scenarios. Changing the spillway heights together with the flow directions had a significant impact on the performance of RWH by making 92% of all sub-catchments supply sufficient water for crop requirements, compared to 44% of the sub-catchments in case of no changes.

Evaluation of reservoir operation strategies for irrigation in the Macul Basin, Ecuador

Abstract Study focus An irrigation project is planned in the study basin for developing the agriculture as the main income in the region. The proposed water system comprises three large reservoirs damming the rivers Macul and Maculillo. The river basin planning and operation were investigated by modelling alternative reservoir operation strategies aiming at a sustainable balance between irrigation and river ecology by integrated reservoir/river management. New hydrological insights for the region After simulation of long-term meteorological series in a model of the integrated water system, covering several historical extreme events, results indicate that the planned irrigation volumes are higher than the available water for a sustainable irrigation strategy. Two lines of action are suggested for reaching the target irrigation demands: design of a deficit irrigation system, and modifications to the reservoir's spillway height.

AERATION AT OVERFLOW DAMS WITH CURVED SURFACES BY DIFFERENT FLASHBOARD SPILLWAYS

Aeration using overflow dams is an eco-friendly and economical method of improving dissolved oxygen levels in polluted urban streams. Laboratory investigations of aeration performance in smooth spillways, as well as in parallel flashboard and interlaced flashboard spillways with different flashboard intervals, for overflow dams with curved surfaces have been conducted separately. Aeration efficiencies of the different types of spillways, in particular the effects of varying discharge rate, total spillway height, and flashboard interval, have been discussed in detail. The test data illustrate that aeration efficiency in all spillways increases with spillway height and decreases with increasing discharge. Flashboard spillways appear to provide significantly higher aeration efficiency than smooth ones, and aeration efficiency increases with the number of flashboards, but with a continuously declining growth rate. By combining Fds with hd*, a new dimensionless parameter Ψ is created to characterize the comprehensive effects of hydraulic conditions on aeration. Empirical formulas for oxygen-transfer efficiency in smooth, parallel flashboard, and interlaced flashboard spillways have been developed with Ψ and the dimensionless number of flashboards per unit area of spillway N* as independent variables, and the properties of these formulas are discussed.

Stage–discharge relationship for a triangular labyrinth spillway

The labyrinth spillway is characterised by a broken axis in plan, generally triangular or trapezoidal, repeated periodically. Therefore, a labyrinth spillway will have longer crest length than a straight spillway and, for the same head the discharge per unit width, is substantially increased. The discharge over a labyrinth spillway is a function of the total head, the effective crest length and the discharge coefficient. The discharge coefficient depends on the total head, height of spillway, shape of crest and apex configuration of spillway. In this paper, results of experiments on a triangular labyrinth spillway are reported. The stage–discharge relationship for a triangular labyrinth spillway with different crest shapes is obtained. The discharge coefficient was related to the ratio of length of spillway to width of spillway, ratio of total head to spillway height and crest shape.

Simulation model use for analyzing decision variables in multipump rice irrigation system operation

A simulation model for multipump rice irrigation systems called PUMPMOD was used to study the following effects in the Libmanan Cabusao Pump Irrigation System (LCPIS) in the Philippines:(1) the effects of varying the number of pumps operating simultaneously, the maximum rate of land preparation, and farm-plot spillway heights on the size of the potential crop area; (2) the effects of increasing daily pumping duration on potential crop area; and (3) the effects of shortening the pump operation season on potential crop area and the number of pumps in simultaneous operation on the degree of water stress on the rice crop. We found that the size of potential crop area can be increased by over 550 ha for every additional pump operating for 18 hours each day during maximum water demand periods. The maximum rate of land preparation that can be supported by the irrigation system limits the size of the potential crop area, but when the per day rate exceeds 7.5% of the system's command area water supply becomes the limiting factor. The simulation indicates that if the pumps can be operated longer than 18 hours a day, a significantly larger area than the current average of about 1500 hectares can be satisfactorily irrigated. A regression model indicates that there is potential for major saving in LCPIS operating costs by reducing the allowable period of pump operation during the wet season without significant reduction in rice yields.