Showing 49 results for Discharge
Seyyed S. M. A. Maddahzadeh., K, Esmaili, B. Ghahraman,
Volume 21, Issue 1 (6-2017)
Abstract
Bi-level drainage system is a type of underground drainage systems, in which adjacent drainage lines are installed at different depths. In the Hydraulics Laboratory, Ferdowsi University of Mashhad, a model was built, that include a cube tank 2 meters in length, width and height of 1 meters was made of galvanized. In this model, two rows 20 cm apart from each other drains were installed. As drainage, a pipe of three layers to the outer diameter of 16 mm was made of PVC. Within this model of stratified soil was used as a soil layer of low permeability with a hydraulic conductivity of 1.15 cm per hour, thickness of 20 cm soil layer between two light soil layer with 30-cm thickness for bottom layer and 20 cm for the top layer with a hydraulic conductivity of 1.55 cm per hour. For accurate measurement of the water table Behavior in the soil at each point of the model, some piezometer distance of 10 cm from each other on the floor model was installed. After Outfit of model with blow-off valve, Experiments with a heavy irrigation for different intervals between depths of 30 and 50 cm were used in drainage and water table elevation values as observed values were extracted from the model. The results show that the values obtained from Upadhyaya and Chauhan Equation only in small area of water table profiles, which include an area of between the two drainage, are consistent with observed and with a wider distance between deep and shallow drainage, time of drop in water table increased.
A. R. Vaezi, M. Ahmadi,
Volume 21, Issue 3 (11-2017)
Abstract
Modified Universal Soil Loss Equation (MUSLE) is one of soil loss estimation models which has been developed based on the runoff characteristics in the event scale. However, it needs to be evaluated in the plot scale for the semi-arid rainfall events. With this aim, a field study was designed using twenty one plots. Runoff and soil loss were measured using 5-min samples under seven rainfall intensities consisted of 10, 20, 30, 40, 50 60, and 70 mm h-1 for 60 min. Soil loss was estimated using the MUSLE based on the runoff volume (Q) and runoff peak discharge (qp) and the values were compared with the observed values. The estimated soil loss was about 3.89 times bigger than the observed value on average. In order to improve model estimations, the power of rainfall erosivity index was modified from 0.56 to 0.62, (Q qp)0.62. The modification of the MUSLE model improved model efficiency (ME) from -5.5 to 0.47 and decreased the root mean square error from 0.000137 to 0.000031. This study revealed that the MUSLE overestimates soil loss from the small plots in the semi -arid regions. Therefore it is essential to calibrate runoff erosivity index using the data observed in the area. The modified MUSLE can be reliably used to predict soil loss in the small plot scale in semi-arid regions.
M. Noshadi, A. Babolhakami,
Volume 21, Issue 3 (11-2017)
Abstract
The uniformity parameters in drip irrigation system are influenced by the slope of manifold and therefore, the evaluation of drip irrigation systems is important in slopping lands. In this research, different slopes of 0.2, 6, 11, 16, 20 and 25% were applied on the ground surface and manifold of drip irrigation system with diameters of 50, 63 and 75 mm and length of 70 m were installed on these uniform slopes. The lateral pipes with 16 mm diameter and 40 m length were placed on the contour lines and connected to manifold bilaterally. The results showed that in the normal emitters in above slopes, the qv(avg) values were 289, 6740, 46, 135, 38 and 27 percent, respectively, qv(max) values were 222, 48, 53, 90, 27 and 9 percent, respectively, and the CV values were 300, 114, 33, 140, 63 and 25 percent, respectively, higher than compensating emitters. However, in the normal emitters in above slopes, the EU values were 33, 34, 12, 25, 17 and 9 percent, respectively, EUa values were 26, 23, 6, 21, 15 and 13%, respectively, UC values were 17, 16, 4, 13, 14 and 9%, respectively, and US values were 10, 8, 2, 8, 5 and 4 percent, respectively, less than compensating emitters. Therefore, even in high slopes (20 and 25%), the irrigation efficiency in compensating emitters were better than normal emitters. The relationship between slope and discharge of emitters represented small changes in discharge of compensating emitters in sloping lands.
H. Dabbaghi, M. Khoshravesh, M. A. Gholami Sefidkouhi,
Volume 22, Issue 2 (9-2018)
Abstract
Emitter clogging for using agricultural wastewater increases the operating costs and reduces the motivation of farmers. The new method to reduce the emitters clogging is the use of a Merus ring that does not have the problems of chlorination and pickling methods, such as pollution and high cost. Due to the importance of agricultural wastewater use, this study investigated the emitters clogging and the effect of Merus ring on the emitter's efficiency in a trickle irrigation system. The treatments including irrigation water (well water and wastewater) and modified water (irrigation with Merus ring and irrigation without Merus ring), as the main factor and the emitters type treatment including Irritec (D1), Corona (D2), Axios (D3), Netafim (D4), Polirood (D5), and Paya (D6) as the sub treatments were performed in three replications. The results showed that the agricultural wastewater caused the emitters clogging in irrigation water and modified water treatments, but over time, the Merus ring had a positive effect on the evaluation parameters of the emitters. For agricultural wastewater, in the first and last irrigation periods, the average discharge of emitters with the Merus ring was 0.05 and 0.33 Liter per hours, respectively, more than the treatment without the Merus ring. The uniformity coefficient of emitters in the first and last irrigation periods, in well water with the Merus ring, was 0.31%and 6.67%, respectively, more than that in the well water without the Merus ring. Also, the uniformity coefficient of emitters in the first and last irrigation periods in agricultural wastewater with the Merus ring was 0.85% and 12.10%, respectively, more than that in agricultural wastewater without the Merus ring. At the end of irrigation period, the results showed that Netafim and Axios had the best and weakest efficiency, respectively. In general, the emitters used in the treatment of well water with the Merus ring had the highest discharge and the emitters used in the treatment of wastewater without the Merus ring had the lowest discharge.
H. Azarpeyvand, A. R. Emadi, M. Sedghi Asl,
Volume 23, Issue 1 (6-2019)
Abstract
Labyrinth weirs are the economic structures to increase the weir output efficiency in limited widths, which can be seen in the plane f trapezoidal and triangular forms. These weirs with a hydraulic load and fixed width pass the more discharge in comparison to other type of weirs. In this study, labyrinth weirs trapezoidal in plane form were investigated. The experiments were performed on 27 laboratory models with 9 different discharge rates and a total of 243 tests. The results showed that, in all of the composite trapezoidal labyrinth weirs, the ratio of discharge coefficient to Ht/p (Ht: Total hydraulic load and p: weir length) weir length was increased at first; after reaching the maximum rate, it started to decrease. According to the suggested general relation, the utmost impact on discharge coefficient resulted from the cycle number and Ht/p relation. Creating new labyrinth on the wing of the weir led to the increase of the effective length; as a result of it, the discharge rate increased in a specific amount of Ht/p. Also, the discharge through a trapezoidal labyrinth weir with the semicircular planform was better than the square; the square, in turn, was better than the simple trapezoidal weirs.
R. Monjezi, M. Heidarnejad, A. R. Masjedi, M. H. Pourmohammadi, A. Kamanbedast,
Volume 23, Issue 2 (9-2019)
Abstract
Nonlinear weirs are regarded as important hydraulic structures for water level adjustment and flow control in channels, rivers and dam reservoirs. One example of non-linear weirs is shaped as curved-zigzag. The crest axis of these weirs is non-linear. At a given width, the crest length is greater than that of the conventional linear weirs. Thus, they achieve a higher flow rate for an identical hydraulic load. This research experimentally focused on the discharge coefficient and flow rate of curved weirs with three different curve radii in two triangular linear and zigzag shapes. The discharge coefficients of these weirs were comparatively explored in terms of the hydraulic performance as a function of the total hydraulic load to weir crest height ratio (hd/P) and curvature angle (θ) (or curve radius). The results indicated that for the same hydraulic load, the increase of θ (the decrease in curve radius) led to a lower discharge coefficient; this was first because of the increased topical rise of water level, and then the more indirect path with a greater curvature through which the flow had to transport. Both factors could negatively affect the water discharge coefficient. In practice, the runoff coefficient at a weir with a curve radius of R/w=1.25 was approximately 8.5% greater than that of a weir with a curve radius of R/w=0.75 under a hydraulic load of 0.2.
B. Navidi Nassaj, N. Zohrabi, A. Shahbazi,
Volume 23, Issue 2 (9-2019)
Abstract
Integrated simulation of water resources systems is an efficient tool to evaluate and adopt various options in macro-policies and decision-making procedures that are in line with the sustainable development of drainage basins. One of the drainage basin management policies is to enhance the efficiency of agricultural land use. Considering the complicated function of the drainage basin elements and their interaction with each other due to water discharge fluctuations caused by various factors such as climate change, the evaluation of these policies is of great importance. Given the low irrigation efficiency in Iran, the present study was aimed to evaluate the effects of management scenarios (including long-term irrigation efficiency increased up to 20% with 5% intervals) and discharge fluctuation scenarios (including 5% and 10% decrease in the average basin inflows) on the reliability and vulnerability of water resources system in Dez Basin. The integrated scenarios were simulated in the WEAP model. The scenarios were separately simulated for the Dez irrigation network and all farmlands across Dez Basin. According to the results, reliability was decreased by 5.69 and 18.89% in the scenarios with 5% and 10% decrease in the average basin inflows, respectively. Furthermore, the irrigation efficiency of 20% in the scenario considering the current inflows ended up with the reliability of 73.58%. Moreover, in the scenario involving 5% decrease in the average basin inflows, the reliability was increased by 3.8% with an increasing efficiency of 20%; with 3.8% and 5.7%, there was an increasing efficiency of 15% and 20% in all farmlands, respectively. In the scenario consisting of 10% decrease in average basin inflows, the reliability was increased by 1.91%, 3.8%, and 5.7% with the increasing efficiency of 10%, 15%, and 20%; on the other hand, with, these were 3.8% 9.46%, and 13.2% with increasing efficiency in all farmlands, respectively. In all scenarios, the vulnerability was found to fluctuate between 25% and 31%, which was systematically analyzed.
J. Rouzegar, A. A. Kamanbedast, A. Masjedi, M. Heidarnejad, A. Bordbar,
Volume 23, Issue 3 (12-2019)
Abstract
Morning glory spillway is one of the spillways that used to passing of flood from high to low level. This spillway is used in the reservoir dams that are placed in narrow valleys and in many locations with high slope in reservoir walls. In the Morning glory spillways, the vortex flow can reduce discharge, discharge coefficient and the performance of spillway. The zigzag spillway, as another type, is introduced as a proper option for compensating the problem of passing maximum possible flow rate, usually encountered by spillways. In the present study, the experimental results of a physical model were used to develop a hydraulic design with squire and circle inlet and analysis method for Labyrinth Morning Glory Spillway. The analysis of experimental data in circle and square inlet showed, that increase in length of spillway and zigzag, causes decrease in the discharge coefficient. Finally the result of effect spillway inlet on flow rate demonstrate that discharge coefficient in square inlet is more than circle, whereas without vortex breaker.
M. J. Asadi, S. Shabanlou, M. Najarchi, M. M. Najafizadeh,
Volume 23, Issue 3 (12-2019)
Abstract
In this study, the discharge coefficient of the circular side orifices was predicted using a new hybrid method. Combinations made in this study were divided into two sections: 1) the combination of two algorithms including Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) and providing the PSOGA algorithm 2) using the PSOGA algorithm in order to optimize the Adaptive Neuro Fuzzy Inference Systems (ANFIS) network and providing the ANFIS-PSOGA method. Next, by identifying the parameters affecting on the discharge coefficient of the circular side orifices, 11 different combinations were provided. Then, the sensitivity analysis conducted by ANFIS showed that the Froude number and the ratio of the flow depth to the orifice diameter (Ym/D) were identified as the most effective parameters in modeling the discharge coefficient. Also, the best combination including the Froude number (Fr), the ratio of the main channel width to the side orifice diameter (B/D), the ratio of the orifice crest height to its diameter (W/D) and the ratio of the flow depth to the orifice diameter (Ym/D) for estimating the discharge coefficient was introduced. For this model, the values of Mean Absolute Percentage Error (MAPE), Root Mean Square Error (RMSE) and correlation coefficient (R) were obtained 0.021, 0.020 and 0.871, respectively. Additionally, the performance of the ANFIS-PSOGA method was compared with the ANFIS-PSO and ANFIS methods. The results showed that the ANFIS-PSOGA method for predicting the discharge coefficient was the superior model
A. Rezaei Ahvanooei, H. Karami, F. Mousavi,
Volume 23, Issue 3 (12-2019)
Abstract
In this research, by using FLOW3D, the performance of non-linear (arced) piano key (PKW-NL) in plan and linear piano key weir (PKW-L), with equal length of weir, was compared. Results showed that nonlinearity of the weir caused 20% increase in the discharge coefficient. Investigating the velocity contours for these two weir models also showed that maximum velocity within the PKW-NL weir structure is about 30% lower than the PKW-L weir. Also, the performance of non-linear piano key weir was evaluated under inward (PKW-IC) and outward (PKW-OC) curvatures to the channel. Results showed that in the case of PKW-IC weir, the discharge coefficient was increased by 8% as compared to the PKW-OC weir. Investigating the pressure contours for these two weir models also shows that the average pressure within the PKW-IC weir structure is about 5% higher than the PKW-OC weir. This increase in pressure leads to a decrease in the speed and better distribution of flow over the weir keys.
S. Nikkhoo Amiri, M. Khoshravesh, R. Norooz Valashedi,
Volume 23, Issue 4 (12-2019)
Abstract
Today, the rising surface temperature of the planet and its effects on the water cycle have attracted the attention of many researchers. The aim of this study was to investigate the effect of climate change on the Tajan (the upstream of Shahid Rajaei dam) catchment area. In order to study the output of CanESM2 model, the SDSM method was used to estimate the magnitude of the data. Flow discharge changes in Shahid Rajaei Dam were simulated using the weather data of Kiasar synoptic station and the temperature and precipitation changes were simulated using the climate scenarios of RCP2.6 and RCP8.5 for the 2016-2066 period. Also, the effect of different scenarios on the outflow of the Soleiman Tangeh hydrometric station was evaluated by SWAT hydrologic model. The results showed that the annual precipitation would be decreased by 58% and the air temperature would be increased by 14% under RCP2.6 scenario. Also, in the RCP8.5 scenario, precipitation would be decreased by 59.5% and the temperature would be increased by 21%. Peak discharge for RCP2.6 and RCP8.5 scenarios would be increased by 4% and 5.7%, respectively, and the average annual discharge might be decreased by 16% and 16.5% in the future period (2016-2066). Therefore, it can be planned by the investigation of conditions for cropping patterns in the downstream to consider the environmental impacts for future periods.
R. Gharibvand, M. Heidarnejad, H. A. Kashkouli, H. Hasoonizadeh, A. Kmanbedast,
Volume 24, Issue 1 (5-2020)
Abstract
The flow fields over a trapezoidal labyrinth weir (two-cycle) and a piano key weir were simulated using Flow3D, studying the impact of each model on the flow field in the weirs and the coefficient of discharge in comparison with the available experimental data. Moreover, the models were investigated experimentally in a 12.5 m long, 0.3 m wide, and 0.4 m high rectangular flume under clear-water conditions. The results showed good agreement between the data from the numerical and experimental models. The piano key weirs had a higher coefficient of discharged compared with labyrinth weirs. The coefficient of discharge was observed to increase by 26 percent as the height of the PKW was increased by 50 percent (from 5 to 7.5 cm). This increase was 24 percent for labyrinth weirs.
N. Sadeghian, A. Vaezi, A. Majnooni Heris,
Volume 24, Issue 1 (5-2020)
Abstract
Few studies have been done regarding the role of the raindrop in the hydrodinamic mechanism of soil erosion. In this study, rainfall simulation experiments were conducted to evaluate the role of raindrop in runoff discharge, sediment concentration and hydraulic properties of flow under four slope gradients (5, 10, 15 and 20%) in a clay soil using a 90 mm.h-1 rainfall intensity to reach the steady state flow. Soil sample was packed into the erosion flume with 0.3m× 0.4m × 4 m in dimensions and tested under two soil surface conditions: one with raindrop impact and one without raindrop impact. The results showed that runoff discharge, sediment concentration, flow depth, shear stress, stream power, Reynolds number and runoff velocity under without raindrop impact condition were significantly lower than those in the condition with the raindrop impact with a factor of 0.62 to 3.54, 0.08 to 11.83, 0.91 to 0.96, 0.26 to 3.25, 0.52 to 4.45, and 0.36 to 3.27, 0.23 to 0.79 times, respectively; on the other hand, the Darcy Wysbach, Chezy and Manning coefficients were increased significantly under without raindrop impact (P<0.01). Flow velocity was the key hydraulic parameter strongly affecting the hydraulic properties. These findings indicated the importance of raindrop impact in the detachment rate of soil particles through the change of the hydraulic characteristics. This study also revealed the key role of raindrop impact on the runoff hydraulic characteristics, as well as particle detachments rate in rills. Information about the role of raindrop impact is a substantial step in modeling the rill erosion. Therefore, elimination of raindrops impact, especially in the steep slopes, with the conservation of natural vegetation cover can sufficiently prevent runoff production as well as the particle detachment rate.
P. Heidarirad, A. A. Kamanbedast, M. Heidarnezhad, A. R. Masjedi, H. Hasoonizadeh,
Volume 24, Issue 1 (5-2020)
Abstract
Water supply at a desired rate at any time to meet the water requirements regardless of river discharge must be considered in the general design of intakes provided that the needs do not exceed the river flow. Due to the lack of necessary information in this field and the importance of sediment transport to the lateral intakes at river bends, this study aimed at understanding the mechanism of this phenomenon. To this end, the combined effect of convergence and divergence in lateral intakes on the sediment transport was investigated. According to the results, the diversion discharge to the intake was increased by converging the laboratory flume. By narrowing and converging the end of the flume, the diversion discharge was increased further, so that as the flume was converged to the size (b/B) of 0.75 and 0.5, the diversion discharge to the intake was increased by 13.6% and 75%, respectively. This could be connected to narrowing, flow obstruction and backflow to the intake. In contrast, different results were found by diverging the flume. In other words, the inflow to the intake was decreased by diverging the flume. As the flume end was diverged, the diversion discharge was decreased further. By diverging the flume to the size (b/B) of 0.75 and 0.5, the diversion discharge to the intake was decreased by 21.9 and 31.8%, respectively. The average diversion discharge to the intake at 30, 60 and 90º was 13.2, 15.2 and 11.5%, respectively. By converting the flume to the size (b/B) of 0.75 and 0.5, the diversion sediment to the intake was increased by 18.5 and 71.4%. In contrast, by diverging the flume to the size (b/B) of 0.75 and 0.5, the diversion sediment to the intake was decreased by 35.4 and 49.9%, respectively.
M. Khast, M. Hesam, A. Hezarjaribi, O. Mohamadi,
Volume 24, Issue 1 (5-2020)
Abstract
Due to the increasing number of small crops, the system of irrigation without a pump can be an economical way. Therefore, in this research, the effects of the type of droplet and the height of water supply system utilization on the characteristics of water distribution (discharge, dispersion uniformity coefficient (CU) and coefficients of variation of discharge) were investigated. In this research, the pressure functions of 1, 2, 3 and 4 meters and three irrigation repeats were investigated; also, the discharge characteristics of jet pots of 2 and 8 nozzles, easy dripper and netafim were addressed. The results indicated that at 1 m pressure, drippers of pots of 2 and 8 nozzles with the uniformity coefficients of distribution were equal to 89.39 and 99.30%, and the discharge rate was 3.60 and 3.62 liters per hour at a pressure of 2 m. An easy-drain drip with a discharge rate of 3.85 L / h and a uniform distribution of 99.44%, at a height of 3 and 4 m, the droplets of the netafim with an outlet discharge were 3.87 and 3.97 liters per hour and the uniformity coefficients of 99.32 and 99.47 percent had the best broadcast conditions. According to these significant differences (P <0.05), it can be concluded that at pressures less than 2 m of jar droplets and at more than 3 m, netafim and Easy Dipper types could have better leakage due to pressure regulators. In general, each of the four types of emitters produced a uniform dispersion and the optimum discharge at different pressures.
A. Alizadeh, B. Yaghoubi, S. Shabanlou,
Volume 24, Issue 2 (7-2020)
Abstract
In this study, the discharge coefficient of sharp-crested weirs located on circular channels was modeled using the ANFIS and ANFIS-Firefly (ANFIS-FA) algorithm. Also, the Monte Carlo simulations (MCs) were used to enhance the compatibilities of the soft computing models. However, the k-fold cross validation method (k=5) was used to validate the numerical models. According to the input parameters, four models of ANFIS and ANFIS-FA were introduced. Analyzing the numerical results showed that the superior model simulated the discharge coefficient as a function of the Froude number (Fr) and the ratio of flow depth over weir crest to the weir crest height) h/P(. The values of the mean absolute relative error (MARE), root mean square error (RMSE) and correlation coefficient (R) for the superior model were calculated 0.001, 0.002 and 0.999, respectively. However, the maximum error value for this study was less than 2%.
R. Daneshfaraz, M. Sattariyan Karajabad, B. Alinejad, M. Majedi Asl,
Volume 24, Issue 4 (2-2021)
Abstract
The scour around the bridge piers is one of the main causes of bridge failure and the extraction of aggregates may aggravate this phenomenon. The present study comprehensively investigated the scour around the groups of bridge piers in the presence of aggregate extraction pits, using different discharges. The bridge piers roughened by gravel had been compared with the simple bridge piers; so, the results showed that the roughening caused the reduction of the scour depth. Scour depth change rate led to an increase in the equilibrium time. The results also showed that the reduction of the scour depth at the downstream groups of piers was more than that in the upstream. For the lowest discharge, the aggregate extraction pits had a considerable effect on the scour depth difference for the groups of piers in the downstream and upstream. On the other hand, the effects were decreased when the rate of discharge was increased. The experimental results obtained by the rough surface models showed that as the discharge was increased, the local scour was increased too; at the same time, the bed profile was posed at the low level. Generally, the scour depth of the groups of piers in the downstream of the extraction pit was more than that in the upstream. The results of the current research, therefore, demonstrated that the surface of the bridge pier roughened by gravel reduced the scour depth.
M. Alinezhadi, S. F. Mousavi, Kh. Hosseini,
Volume 25, Issue 1 (5-2021)
Abstract
Nowadays, the prediction of river discharge is one of the important issues in hydrology and water resources; the results of daily river discharge pattern could be used in the management of water resources and hydraulic structures and flood prediction. In this research, Gene Expression Programming (GEP), parametric Linear Regression (LR), parametric Nonlinear Regression (NLR) and non-parametric K- Nearest Neighbor (K-NN) were used to predict the average daily discharge of Karun River in Mollasani hydrometric station for the statistical period of 1967-2017. Different combinations of the recorded data were used as the input pattern to predict the mean daily river discharge. The obtained esults indicated that GEP, with R2= 0.827, RMSE= 59.45 and MAE= 26.64, had a better performance, as compared to LR, NLR and K-NN methods, at the validation stage for daily Karun River discharge prediction with 5-day lag, at the Mollasani station. Also, the performance of the models in the maximum discharge prediction showed that all models underestimated the flow discharge in most cases.
A. R. Bahrebar, M. Heidarnejad, A. R. Masjedi, A. Bordbar,
Volume 25, Issue 2 (9-2021)
Abstract
The combination of a labyrinth weir with an orifice is a proper solution for floating material to pass over the weir and transfer sediment through the orifice. Additionally, creating a slot in the overflow wing leads to higher discharge. This study examined four discharges (5, 10, 15, and 20 liters per second) with channel width and height of 30 and 40 cm in trapezoidal-orifice, square-orifice, and triangular-orifice labyrinth weirs in the laboratory and using Flow3D with RNG k-epsilon (k-ε) turbulence model, the results were compared with one another. Comparing the discharge flow over weirs and measuring the discharge coefficient among the mentioned models showed that the triangular-orifice labyrinth weir had the highest discharge rate. Moreover, the increased Ht/P ratio (Ht represents total hydraulic head; P denotes weir height) for all models resulted in the increased discharge coefficient. Due to the efficiency of this type of weirs, the highest discharge coefficient was obtained at low Ht/P ratios. At lower ratios, since there was free flow, the coefficient of weir discharge increased, and as the ratio increased, the weir was partially submerged. Furthermore, for the weir design, the best Ht/P ratio was between 0.13 to 0.41, and the maximum discharge coefficient (Cd = 1.2) was within this range.
J. Meshkavati Toroujeni, A.a. Dehghani, A. ٍemadi, M. Masoudian,
Volume 25, Issue 3 (12-2021)
Abstract
One of the crucial problems that exist in the irrigation networks is the fluctuation of the water surface flow in the main channel and changes in the flow rate of the intake structure. One of the effective methods to decrease these fluctuations is increasing the weir crest length at the given width of the channel with the use of the labyrinth weirs can be achieved for this purpose. The labyrinth weir is the same linear weir that is seen as broken in the plan view. In this study, a labyrinth weir with a length of 3.72 m, three different heights of 15, 17, and 20 cm, three different shapes of dentate (rectangular, triangular, and trapezoidal), and a linear weir were used in a recirculating flume with 15 m length and 1 m width. The result showed that for a given length and height of weir, with the increasing of the upstream water head to the weir height ratio (
), the discharge coefficient decreases. The results showed that by increasing weir height, the discharge coefficient decreases for a given length of the weir. Linear weir and labyrinth weir without dentate create more water depth at the upstream by 3.3 and 1.2 fold compared with dentate labyrinth weir.
