Journal of Irrigation Sciences and Engineering
Year:2018 | Volume:41 | Issue:3 |Papers Count:18

Each year rivers transport a lot of sediments, especially for flood times, to dams’ reservoirs and the main cause for this transportation is density current phenomenon. This phenomenon forms when a liquid with a density of ( ) flows in another liquid with density of (. This density deference could be due to the temperature, or dissolve solids, or suspended solids deference or a combination of them (Graf and Altinakar, 1998). Vargavand (2013) made a density current using the solution of water and salt and investigated the effect of a bed with cylindrical and conical roughness on water entrainment coefficient. His results showed that the water entrainment coefficient not only affected by Richardson number but the height of bed roughness is also an important parameter. Daryaee (2014) investigated the water entrainment coefficients for four bed slopes, two sediment concentrations and four different bed roughness height in a sedimentary density current. The results of this research showed that by increasing roughness height velocity decreases and this increases Richardson number and a result water entrainment coefficient decreases. However, roughness blocks cause for more turbulent flow which extended up to interface of density current and ambient water and this phenomenon makes more water entrainment. The aim of this research is to investigate the effect of bed roughness, bed slope, and hydraulic parameters of density current such as flow rate and concentration on water entrainment of a salty density current...

Rainfall-runoff simulation models can be used in many water resources applications such as flood control, drought management. Although modeling is both continuous and single-event, continuous modeling has been less important in our country. In continuous models, more hydrological parameters are involved in comparison with single-event models, although this leads to more complicated modeling, but instead of a more realistic conditions of the hydrological system of the watershed will be illustrated and, in continuous systems, the surface water status can be monitored over a long period of time. Single-event models simulate only one incident, hence the moisture content between rainfall events is not considered, in contrast to continuous models of longer periods for estimating the response of the hydrologic information of the basin considered throughout the length of the rainfall events and between them (Lastoria, 2008). The American Hydrological Engineers Center (HEC), along with continuous hydrologic modeling, added the Soil Moisture Accounting (SMA) soil moisture content algorithm based on the PRMS model to the HMS software (Bennett, 1998). In this research, the aim is to provide an automatic calibration model based on the anion colony for the HMS-SMA soil moisture model. In this continuous model, the multiplicity of the considered parameters of the model, in addition to causing the difficulty of calibration by the method of trial and error, which also allows the automatic calibration of the software package to fail. For this purpose, in this research, by selecting a continuous HMS-SMA rainfall-runoff model, an external optimization program (Anion Cluster Algorithm (ACOR)) was used to overcome the weakness...

Bridges are one of the most important structures which are under attention from many years. Bridge is a structure to cross over obstacles such as rivers or valleys. In recent decades, despite using modern materials and technology, and spending lot of costs for designing and building bridges, failure of them are commonly reported due to flood and local scouring. Local scouring occurs by placing obstacles such as abutments in flow direction. Different methods of reducing scour hole have been investigated by researchers. (Johnson et al. (2001) and Kayaturk et al. (2012)). The methods of scour reduction are divided to two main groups, known as direct and indirect methods. In direct methods or bed resistant methods, the resistant of bed against scouring is increased by adding different materials to the bed and near groin. In these methods, flow patterns remain constant but resistant of bed materials increases. Morales et al. 2008 investigated these kinds of methods by using of gravels and rocks. Korkut et al. 2006 used sacks of sands (geo bag). In indirect methods which are known for changing flow pattern, changes are made to flow pattern to reduce the power of destructive vortexes or remove them from head of abutment. Examples of investigating these methods are using parallel walls in abutments by Li et al. 2006, using submerged plates by Johanson et al 2001 who investigated a short vertical abutment in flood plain of a river. They investigated effects of different cases of placement submerged plates in main channel on water scouring. They reported that these plates eliminate vortexes from abutment and scour hole will transfer to the middle of the river; however scour depth will increase in this method...

Nowadays, in water resources management, climate change is one of the main challenges. Changes in the water cycle are one of the most important of ground responses to warming it (IPCC 2014). Changes of precipitation and temperature caused by climate change, will damage to the products of garden and agricultural. Therefore, in order to increase the food security in future periods, it is necessary to evaluate the climate change impacts on the agricultural of regions and provide adaptation strategies its. So Regarding the importance of climate change, the purpose of this study is simulating the performance of the agricultural sector Hashtgerd Plain under climate change impacts in the future period (2020-2049)...

Underflow density currents traveling through density-stratified fluids begin to separate from the bed as they reach areas of similar densities, after which they continue their path as interflows through the surrounding ambient fluid. This point, which is referred to as “ separation point” of density currents, acts as the boundary between the underflow and interflow density currents. A density current within a stratified environment is known as intrusive gravity currents (IGC), which travel horizontally at a roughly constant velocity U within the stratified layer after propagation (Nokes et al., 2008). Regarding underflow density currents, efforts have been made by many researchers e. g. Singh, and Shah (1971), Lee, and Yu (1997) and Farrell, and Stefan (1986) in the past decades to determine the location of the plunge point of underflow density currents (which is similar to the separation point in interflow currents) using experimental and theoretical methods based on the Densimetric Froude Number at the plunge point Fp. Although studies have been conducted on interflow density currents, including Kao (1977), Wells, and Nadarajah (2008), An, and Julien (2014) and Zhang et al. (2015). Not any research has been found in the literatures about the height of density current at the point of separation from the bed. Hence, in addition to examining the height variations in density currents at the separation point with respect to changes in hydraulic parameters such as flow rate, density of the flow at the inlet, as well as the bed slope, the present study attempted to derive a relation for prediction of density current height at the point of separation from the bed under different conditions...

Stream flow forecast is a fundamental tool that could be utilized for appropriate water resource management. The enhancement of accuracy as well as the increase of time horizon for stream flow forecasts is essential especially for agricultural sector which is the most vulnerable sector during water shortages. In this regard, the application of stochastic approaches like Ensemble Streamflow Prediction (ESP) procedure for long-term forecast with respect to streamflow uncertainty can be proposed. The ESP procedure produces streamflow forecasts in the form of multiple hydrographs, each a possible realization of seasonal streamflow (Day, 1985). One example of ensemble streamflow forecasts is the National Weather Service’ s ESP procedure. Faber and Stedinger (1002) successfully combined reservoir operation models with updated information from ESP of the National Weather Service (Faber and Stedinger, 2001). Using ESP forecasts, Eum et al. (2011) also developed a procedure to calculate optimal water release curtailments during droughts using a future value function derived with a sampling stochastic dynamic programming model. The main objective of this paper is to present a probabilistic approach and forecast the inflows to Jiroft dam reservoir. In this regards, using ESP approach as well as Artificial Neural Networks (ANNs) the 1-to 12-month ahead probabilistic scenarios of Halil river were forecasted.

Coasts play an important role in economy of each country for their strategic location for residential, recreational, and industrial activities. Hence, a need has arisen to protect and maintain these coasts against waves and currents. (Rageh et al., 2009). The main cause of damage to coastal structures is the wave impact force. Protective structures such as submerged breakwaters, screen breakwaters, and various piles are often designed to provide additional attenuation of the impact force impact. The use of vertical slotted barriers can be a cost effective solution for wave energy dissipation when sloped rubble structures are not desirable. For a cost-effective design of such barriers, an accurate estimation of dynamic pressures characteristics is needed. Many experimental and theoretical studies were carried out for determining the dynamic pressures acting on different shapes or structures supported on piles. Neelamani & Sandhya (2005) investigated wave reflections, run-up and run-down, and wave pressures on plane, dentate and serrated seawalls. Krishnakumar et al. (2010) studied the effect of wave screens on the reduction of pressures and forces on a vertical wall on its lee side due to directional waves. Shih (2016) investigated the performance of a pervious pipe screen breakwater installed in front of a seawall in terms of reducing the wave impact force and wave pressure. The preceding brief review suggests that there is not much experimental data published on the wave induced dynamic pressures acting on compound wave screen. In this study, experimental investigations on wave pressures on different compound wave screen configurations were carried out in regular wave. The wave screen consists of a perforated wall that extends from above the seawater to above the seabed. The gap between pipes allows the seawater exchange, the sediment transport and the fish passage and the results of this study can be used for a better hydrodynamic design of vertical structures...

Since the importance of water in the durability and survival of life is clear to everyone, water issue has always been the focus of researchers and experts. Iran, having its own geographical and climatic location, has a small share of rainfall. Therefore, having an average annual rainfall of about 240 millimeters, one-third of the global average (860 millimeters), it is part of the dry and semi-arid climate (Alizadeh, 1997). Due to the lack of statistics, complexity of hydrological ecosystems and the impossibility of full recognition of the conditions in many catchment areas of the country, the use of methods that measure the amount of runoff from rainfall in non-statistical basins or those with incomplete statistics are of prime importance. One of these methods is the use of the capabilities of hydrological models in the simulation of hydrological processes which is one of the initial stages of water resources management and planning, and also the study of the hydrological effects of land use change and the way of exploitation of natural resources in a basin, where it is possible to simulate the hydrological processes, such as runoff, in the basins with complete statistics with the lowest cost and minimum time, and then use the information to estimate runoff in similar basins with no statistical data or incomplete statistics (Namdorost, 2002). LARS-WG5 is one of the generators of meteorological accidental data that is used to generate daily rainfall data, daily irradiance and maximum and minimum daily temperatures in a station under present and future climate conditions (Semenov and. Brooks., 1998). Zarghami et al (2001) reported a 2. 3 degree increase in temperature and a 3 percent reduction in rainfall over the years 2020-2090 for East Azarbaijan province with the LRS-WG Exponential Meteorological Scale under the A1B, A2 and B1 scenarios using HADCM3 output...

Evapotranspiration is one of the most important factors in hydrological cycle. Potential evapotranspiration is used to design in irrigation and drainage networks and hydrological studies (Davis & Dukes, 2010). The conducted studies in different regions of the world have shown that the FAO-Penman-Monteith model can be presented as the most accurate method under various climatic conditions (Irmak et al, 2003, ASCE-EWRI, 2005, Jabloun & Sahli, 2008, Martinez & Thepadia, 2010 and Azhar & Perera, 2011). The calibration of the mentioned equation using lysimetric data in a wide range of climatic conditions and its applicability without the requirement for local calibration in different climatic conditions are the benefits of the FAOPenman-Monteith equation (Landeras et al, 2008). On the other hand, the Valiantzas model is one of the newest methods for estimating ETo. Advantages of using the Valiantzas equations in the estimation of reference evapotranspiration include simple application for spatial calibration, easy application for temporal distribution of reference evapotranspiration values, easy use for routine hydrological applications and simplicity of equations for other hydrological applications (a, b, c, Valiantzas, 2013). The purpose of this study was to evaluate and compare the accuracy of five different Valiantzas models for estimating reference evapotranspiration at the studied stations located in the northwest of Iran (Urmia Lake basin) including Urmia, Salmas, Mahabad, Takab, Tabriz, Sarab and Maragheh and providing the best version of the Valiantzas as the results of which are the highest concurrence with the FAO-Penman-Monteith method.

Moisture flow through unsaturated zone is vital in agricultural engineering, soil science, groundwater hydrology, and environmental engineering. Moisture flow through unsaturated zone is complex due to the dependencies of flow and storage properties on the pressure head and is commonly analyzed by solving Richards’ equation. Solution of Richards’ equation requires the knowledge of soil hydraulic conductivity and water content versus pressure head functions referred to herein as the soil hydraulic properties. Since these functions are highly nonlinear, direct laboratory and field measurements are tedious, time consuming, and involve considerable uncertainty (Hari Prasad et al., 2010). An alternative to the direct determination is to employ the parameter estimation methods using inverse procedure for the determination of hydraulic properties. Indirect methods are divided into several categories, including methods based on pedotransfer functions, semi-physical, and inverse methods (Abbasi, 2007). Determination of hydraulic properties by inversion of in situ measured moisture contents, pressure heads and cumulative infiltration have become an alternative to direct measurements due to decrease in the computational costs and development of efficient optimization algorithms...

Regime and hydraulic geometry are two of the most important proposed models over the past century in the related disciplines of river engineering and fluvial geomorphology. Therefore, the hydraulic geometry is of prime importance in planning, design, and management of river engineering and training works (Huang, 1996). The first systematic analysis was conducted on canal systems in India by Kennedy (1895) who exhibited a relation between velocity and depth. Downstream hydraulic geometry relationships describe the shape of bank-full alluvial channels in terms of bank-full width, average flow depth, average flow velocity and channel bed slope. Although some concepts of hydraulic geometry were proposed toward the end of the nineteenth century, the real impetus toward formulating a theory of hydraulic geometry was provided by the work of Leopold and Maddock (1953). Leopold and Maddock (1953) adapted the ideas from regime relations for canals to the description of natural stream channels. Generally, there are two experimental and analytical methods to obtain the hydraulic geometry relations in order to determine the stable geometric dimensions of the rivers. Different researchers have studied hydraulic geometry relations for straight rivers without considering the effect of the secondary flow. The main focus of this study is to analytically derive the hydraulic geometry equations considering the concept of secondary flow in meandering channels.

Non-saline water resources are scarce, especially in arid and semi-arid regions. Therefore, the consumption of saline water is inevitable in agricultural usage. Iran has large saline water sources that have different levels of salinity. The use of these resources requires special management practices for the reduction of their negative environmental impacts. The usage of saline drainage waters, generated by irrigated agriculture, seems inevitable for plants irrigation. Salinity stress reduces the osmotic potential, as well as all major processes of plant including growth, photosynthesis, protein synthesis, and lipid and energy metabolism. Of course, the response of plants and tolerance of different species of plants are different to salinity. The rapid reduction of leaf area and number of leaves, decreasing biomass (dry matter) of the shoot and root, as well as reducing the plant height and active root level in the soil are among the plant responses to salinity stress. Salinity induced changes in photosynthesis, stomatal behavior, chlorophyll content and accumulation of metabolites at growth various stages of ber (Hooda et al, 1990; Ramoliya and Pandey, 2007). Investigating the applicability of agricultural lands drainage in irrigation of juvenile ber plantation and determining the production function of water salinityshoot dry matter of juvenile ber were overall objectives of this research...

Horizontal intakes are one of the most important parts of hydraulic sets such as rivers for irrigation or reservoirs for power generation and industrial purposes. Air entrainment, by means of a free air-core vortex occurring at intake pipes, is an important problem encountered in hydraulic engineering...

Stepped spillways are hydraulic structures which due to the high energy loss of flow have important role in reducing dimensions of stilling basin of downstream of the dams and consequently their economical design. The dam designers tended to study the characteristics of flow on this type of spillways in recent decades. Horizontal steps, inclined steps, and steps with end sills may be used in stepped spillways. The energy loss of flow on stepped chute depends on the total discharge per unit width of chute, the total flow head, the step height, the step length, the gravitational acceleration, and the height characteristics of the step. For the inclined step, the height characteristics is the increment of step above the horizontal level or the angles of step. The objective of the study is to compare the relative energy dissipation between horizontal steps and inclined steps and find the optimal energy dissipation efficiency for flow on stepped chutes. In this paper, the effect of angles of inclined step, relative critical depth, and relative discharge on the relative energy dissipation over stepped spillways are investigated and discussed, too. To achieve this goal, first the FLUENT model’ s output results for simulation of flow passing over a stepped spillway are validated using the experimental data, and then effect of the of angles of inclined step is examined. Also, an equation for the estimate of the relative energy dissipation for inclined stepped spillways was developed...

The Wetlands are one of the most important ecosystems on Earth that human activities, including urban development and agriculture, road construction, often cause indirect damage and cause significant loss of lagoons and coastal areas. Therefore, we need a sophisticated tool and method to access and understand the conditions of the wetland. Strategic planning is a systematic approach that supports and validates the strategic management process. Strategic planning consists of four basic elements including environmental review, strategy formulation, strategy implementation, and control and evaluation. Strategic planning models are countless, but almost all of them are inspired by the SWOT analytical model. Ghareh Gheshlagh wetland the most important and largest satellite wetlands of Lake Urmia Basin and One of the important bird areas, IBA, is in the world. Unfortunately, in recent years due to destructive human activities are faced with many risks. This applied scientific research, with the aim of providing Strategic Plan for development Environmental Protection of Ghareh Gheshlagh wetland. Considering the conditions and internal and external factors prevailing in the region and using SWOT analysis was conducted...