Irrigation
F. Hayatgheibi; N. Shahnoushi; B. Ghahreman; H. Samadi; M. Ghorbani; Mahmood Sabouhi
Abstract
Introduction: The development of water resources in many cases has led to increased economic welfare, improved living and health standards, food production, etc. However, in some cases due to the insufficient attention to all aspects of these projects, the irreparable environmental effects and subsequent ...
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Introduction: The development of water resources in many cases has led to increased economic welfare, improved living and health standards, food production, etc. However, in some cases due to the insufficient attention to all aspects of these projects, the irreparable environmental effects and subsequent social and economic effects have been imposed on society. Paying attention to environmental water requirements is one of the most important issues in decision making in water resources development plans. The objective of this study is to assess river environmental water requirements in upstream and downstream of Beheshtabad Dam. Beheshtabad Dam has designed to build on the Karun River for water transfer from Karun to Zayanderood basin. But it has not been implemented due to the various problems and challenges. Materials and Methods: Protecting and restoring river flow regimes and hence, the ecosystems they support by providing environmental flows has become a major aspect of river basin management. Environmental flows describe the quantity, timing, and quality of water flows required to sustain freshwater,estuarine ecosystems,the human livelihoods, and well-being that depend on these ecosystems. Over 200 approaches for determining environmental flows now exist and used or proposed for use in more than 50 countries worldwide. In the present study, hydrological methods have been used. These methodes include Tennant and modified Tennant, Flow Duration Curve (FDC) and FDC shifting (for different environmental management classes). For this purpose, four hydrometric stations (three stations upstream and one station downstream of the dam) have been selected. Results and Discussion: The results of the study showed that the river water flow had not been sufficient to meet environmental water requirements in several cases, especially in years when the region was experiencing mild to moderate drought conditions. According to the Tennant method, the minimum environmental flow requirement averages based on Beheshtabad, DezakAbad, Kaj, and Armand stations data were 3.80, 5.06, 6.99, 22.01 m3/s, respectively. Using the mentioned stations data, , the minimum environmental flow requirement averages were 3.62, 6.07, 7.91, 23.67 m3/s based on the modified Tennant method. According to the flow duration curve method, minimum environmental flow requirements (Q95) were 1.96, 5.1, 8.32, 30.62 m3/s, using data collected from Beheshtabad, DezakAbad, Kaj, and Armand stations, respectively. The results of the flow duration curve shifting method indicated that the river water flow did not meet the river environmental water requirements in different environmental management classes in some months and years. Comparative results of different methods revealed that the minimum environmental flow requirement of Beheshtabad River upstream of Beheshtabad Dam was 1.22-16.75 m3/s from September to April (based on FDC shifting method, class C). The estimated minimum environmental flow for Koohrang River was 3.69-16.81 m3/s from September to April. The downstream of the dam, Karun River requires a minimum flow rate of 20.8-73.29 m3/s from September and October to April (based on FDC shifting method, class E). Conclusion: According to the results of various methods used in this study, the Karun River flow is not enough to meet the minimum river environmental water requirements in some years and months. Therefore, decision-makers must pay attention to the environmental water requirements in decisions related to the development plans and water transfer from this river. It should be noted that the river environmental water requirements have not been met completely when the region has experienced moderate or mild drought, which would be more acute in cases of more severe drought conditions. Therefore, the current surplus water of this basin may not be a sustainable source to transfer to another basin.
P. Maleki; M.J. Ketabdari; hossein samadi; D. Maleki
Abstract
Introduction: Interactionbetweenwater flow characteristics andthe bed erodibilityplays an important role in sediment transport process. In order to reach stability, rivers with deposition or bottom erosion make a different bed form in the riverbed. One way to identify thebehavior of therivers is to study ...
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Introduction: Interactionbetweenwater flow characteristics andthe bed erodibilityplays an important role in sediment transport process. In order to reach stability, rivers with deposition or bottom erosion make a different bed form in the riverbed. One way to identify thebehavior of therivers is to study the structure and formation of bed forms within them. Ripples are the smallest of the bed forms. The longitudinal cross section of ripples are usually not symmetrical. The upstream face is long and has a gentle slope, and the downstream face is short and steep. The height of ripples is usually between 0.5 cm and 2 cm; the height ripple is not more than 5 cm. The wave lengths normally do not exceed 30cm, and they are usually within the range of 1 cm to 15 cm. Their occurrence is the result of the unstable viscous layer near the boundary. They can form in both shallow and deep water.With an increase of the flow velocity, the plan form of the ripples gradually develops form straight line to curves and then to a pattern like fish scales, symmetrical or unsymmetrical, as shown in Fig 1.
Figure1-The patterndevelopment oftheripple
Raudkivi (1966) was the first person that, the flow structure over ripples was investigated experimentally.Hethenestablishseveraldifferent conditionsonthemovingsandbedinanlaboratorychannelconsisted of a rectangular cross-section with base width of 70cm, wasable toform arow ofripples , he wassucceed toform arow ofripples.JafariMianaei and Keshavarzi(2008),studied the turbulentflow betweentwoartificialripples for investigate the change of kinetic energyandshearstress on overripples. The stage- discharge rating curve is one of the most important tools in the hydraulic studies. In alluvial rivers,bed rippled are formed and significantly affect the stage- discharge rating curve. In this research, the effects of two different type of ripples (parallel and flakeshape) onthe hydraulic characteristicsof flow were experimentally studied in a flume located at the hydraulic laboratory ofShahrekordUniversity, Iran.
Bass (1993) [reported in Joep (1999)], determined an empirical relation between median grain size, D50, and equilibrium ripple length, l:
L=75.4 (logD50)+197 Eq.(1)
Where l and D50 are both given in millimeters.
Raudkivi (1997) [reported in Joep (1999)], proposed another empirical relation to estimate the ripple length that D50 is given in millimeters:
L=245(D500.35) Eq. (2)
Flemming (1988) [reported in Joep (1999)], derived an empirical relation between mean ripple length and ripple height based on a large dataset:
hm= 0.0677l 0.8098 Eq.(3)
Where hm is the mean ripple height (m) and l is the mean ripple length (m).
Ikeda S. and Asaeda (1983) investigated the characteristics of flow over ripples. They found that there are separation areas and vortices at lee of ripples and maximum turbulent diffusion occurs in these areas.
Materials and Methods: In this research, the effects of two different type of ripples onthe hydraulic characteristics of flow were experimentally studied in a flume located at the hydraulic laboratory of ShahrekordUniversity, Iran. The flume has the dimensions of 0.4 m wide and depth and 12 m long. Generally 48 tests variety slopes of 0.0005 to 0.003 and discharges of 10 to 40 lit/s, were conducted. Velocity and the shear stress were measured by using an Acoustic Doppler Velocimeter (ADV). Two different types of ripples (parallel and flake ripples) were used. The stage- discharge rating curve was then estimated in different ways, such as Einstein - Barbarvsa, shen and White et al.
Results and Discussion: In order to investigateresult of the tests, were usedst atistical methods.White method as amaximum valueofα, RMSE, and average absolute error than other methods. Einstein method offitting the discharge under estimated. Evaluation of stage- discharge rating curve methods based on the obtained results from this research showed that Shen method had the highest accuracy for developing the stage- discharge rating curve than other methods. It also showed that theShenmethod was much accuracy by the parallel shape of ripplebed form compared with the flake shape.
Conclusion: Evaluation of stage- discharge rating curve methods based on the obtained results from this research showed that Shen method had the highest accuracy for developing the stage- discharge rating curve than other methods. It also showed that theShenmethod was much accuracy by the parallel shape of ripplebedform compared with theflakeshape. The results of the estimation of statistical parameters such as root mean square error (RMSE) and mean percent error for these cases indicated that the Shen method is associated with the lowest RMSE and error percentage. Therefore it estimates the stage- discharge rating curve more accurately than other methods. Furthermore in the case of parallel and flake ripple bed forms correlation coefficient was obtained as 0.87 and 0.43 respectively. This indicates that the Shen method is more accurate for the parallel shape of rippled bed forms than the flake shape ones.
N. Najafpour; M. Shayannejad; hossein samadi
Abstract
Pore pressure, seepage and drainage discharge through in earthen dams are the most important characteristics that have to be defined in order to analysis an earth dam. These parameters have been measured since beginning of building dam. In this investigation, a physical model of homogenous earth dam ...
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Pore pressure, seepage and drainage discharge through in earthen dams are the most important characteristics that have to be defined in order to analysis an earth dam. These parameters have been measured since beginning of building dam. In this investigation, a physical model of homogenous earth dam created in the flume with three different angles of toe drain, then pore pressure of earth dam was measured by piezometers that put on the wall of the flume. Discharge of drainage was measured too. The seepage analysis was conducted by PLAXIS software then Result of the PLAXIS compare with physical model by SAS (Statistic software) and finally the best angle and without dimension index ,p/h, propose for toe drain according to results & observations.