Journal of Irrigation Sciences and Engineering
Year:2019 | Volume:42 | Issue:3 |Papers Count:15

Introduction The Curve Number (SCS-CN) method, one of the most widely used methods for estimating runoff in hydrology, has been developed by soil conservation services. The application of SCS equation in Iran may be mixed with considerable errors due to different climatological, geological, and hydrological characteristics. In addition, the other cause of error in this method is the relationship between Ia and S (Equation 2), which is experimental and has been taken from rainwater data in small laboratories (Anonymous, 1972). This relationship can be criticized in terms of the document and was examined in various studies of its accuracy and application (Bo et al., 2011, Shi et al., 2009, Baltas et al., 2007, Mishra et al., 2006, 2004, Hawkins et al., 2002), In order to calibrate the SCS equation and evaluation in empirical relations, Pasekohak catchment was selected. Pasekohak basin includes four sub-basins where flood runoff was gauged during five flood events. Curve Number (CN) for the sub-basins was estimated according to the remote sensing, geological maps, and field works. The real hydrograph for each event was compared with SCS hydrograph in HECHMS software, and the calibration and correction of SCS coefficients were conducted. The results suggest a correction coefficient of 0. 92 for SCSLag, the average ratio of Ia/S is 0. 044, which is completely different from 0. 2 in SCS. The CN in the study area is 0. 41 of CN provided by SCS...

Introduction Due to problems with on-site irrigation channels, such as occupying a high level of the land, a lack of suitable loan materials, and the possibility of dealing with multiple complications, the use of prefabricated channels is one of the most competitive options available for the existing channels. From the theoretical point of view, the most effective hydraulic cross-section for the coated channels in which smooth water flows is the semicircular section. Nevertheless, in terms of implementation, the use of the semicircular cross-section is generally limited to the reinforced concrete channel. One of the important issues in outdoor hydraulic engineering is having sufficient knowledge about the amount of hydraulic resistance against the flow. The estimation of hydraulic resistance of the flow in open channels has always faced a serious challenge because of the presence of secondary currents and the vortex viscosity. The determination of the contribution of flow pipes in the bed and wall is faced with errors due to the effects of the walls on the maximum velocity position. Accurate prediction of boundary shear stress distributions in the open-channel flow is crucial in many engineering problems, such as channel design, the balance of energy, and sedimentation. Determining the exact bed and wall shear stress is important from a theoretic and applied point of view, for example, its role in scour and sedimentation studies and designing shield conservations...

Introduction Groundwater represents one of the largest stocks of accessible freshwater and accounts for about one-third of freshwater consumption globally (Famiglietti, 2014). Overpumping the groundwater, especially in arid and semiarid areas, has had negative effects on the environment. Recognizing the productivity of water and soil resources is the first step toward planning and managing the increasing optimum operation of these resources. Water resource management, especially that of groundwater, is very important in the arid and semiarid regions (Moslemi, 2015). Water Crisis is one of the most important environmental hazards that have social and economic consequences. Now we have a serious challenge in countries that they have been overpumping groundwater, which further extraction from groundwater table has caused a decrease in the groundwater level in most areas in the world (Moslemi, 2015). Statistics in world resources show that groundwater decreasing process has hard conditions. The index of the water crisis in Iran, considering its presence in a dry and semi-arid region, is more unfavorable than the average level in the world, in other words, up to one percent of world populations live in Iran while its portion from sweet water resources is just 0. 36 %. On the other hand, all the world just uses 45% of the resources, but Iran has used 66% of its saved sweet water (Khorani and Khajeh, 2014). In population program and their environment national organization, Iran is at the 100th place on the list of countries that their rehabilitation of sweet water per person is low. According to international standards, Iran will soon be in a state of a scarcity of water and will be in a group of countries facing a water crisis (Bargahi and Mousavi, 2007)...

Introduction There are different types of stilling basins, including the standard stilling basin USBR, stilling basin SAF, the stilling basin with a continuous sill, and the stilling basin with perforated sill noted. Each basin, depending on the intensity of the hydraulic jump, usually needs components to reduce the length of the hydraulic jump as much as possible while shaping it at a specific location. These components include the chute block, baffle piers, and perforated sills that are the subject of this study. These types of dampers are the most common energy dampers in dams and irrigation and drainage networks, and they generally have a high efficiency of over 60% in energy dissipation. The purpose of this study is the evaluation of one and two perforated sill(s) in the stilling basin and its impact on characteristics of the hydraulic jump, such as the length of the hydraulic jump, the dissipation of energy, and the required tailwater depth, and also, to determine the optimal distance of one and two perforated sill(s) from the beginning of the stilling basin with a fixed height for the perforated sill and ratios of the opening of holes equal to 50%...

Introduction Climate change is a serious challenge to human interest by its adverse effect on various sectors, such as water sources, agriculture, and energy. According to IPCC report, the average annual temperature of the earth has been raised between 0. 3 to 0. 6º because of the spread of the greenhouse gases, and this report predicts this amount will increase between 1 to 3. 5º until 2100(Boberg et al, 2010). To study the effect of greenhouse gases in the atmosphere and the oceanic-atmospheric, general circulation model in regional scale is the most efficient vehicle. These models have been developed to simulate the current climate. They also performed well in predicting future changes in the climate and simulating interactions of soil, atmosphere, and oceans (IPCC, 2007). The effect of climate change on water sources is assessed using rainfall-runoff models by simulating hydrological processes. Studying future climate change and its likely events will help planners and water sources administrators to cope with the future challenge. Considering these likely changes will contribute to objective planning toward optional operations. Predicting future runoff value is one of the most important factors about dam construction, water transferring, agricultural growth and industrial activities...

Introduction Rockfill dams are considered as detention structures, used to control floods. Due to rocks’ size and large pores in between, Darcy’ s law is invalid in these dams. Many studies have been conducted to investigate the non-linear flow in homogenous coarse porous media. Wilkins (1955), Ahmed and Sonada (1969), and Stephenson (1979) tried to introduce appropriate coefficients of the non-linear flow equation. Other studies have been also conducted to investigate the flow in heterogeneous rockfill structures, such as Hosseini and Joy (2007), introducing a one-dimensional model for non-linear flow in homogenous and heterogeneous coarse porous media. Realizing the importance of layered rockfill dams and the few conducted studies in this field, flow through layered rockfill dam, and horizontal and vertical arrangement of layers have been modeled in the current study. In this regard, a two-dimensional numerical model solving the governing equations by finite volume method has been developed...

Introduction Evaporation loss is a key component of water resource management in arid and semi-arid regions where they are not uniformly distributed temporally. Also, due to the climate condition and physical characteristics of arid areas, a major part of rainfall will be out of reach in the form of flash floods and a few percent is recharged to groundwater aquifers. Rainwater harvesting system (RWHS) is considered as one of the most instrumental techniques that can save rainwater for domestic or agricultural uses. It is a technology used for collecting and storing rainwater in rooftops, land surfaces, or rock catchments using some simple techniques, such as natural and/or artificial ponds and reservoirs. In recent years, climate change has caused significant changes in the meteorological and hydrological components. Also, since precipitation is the main driver of RWHS, changes in its value and time can significantly change the operation of these systems. Therefore, in order to reach sustainable development, water resource management based on rainwater harvesting systems will be inevitable. These systems are moderately reliable methods to increase available water. The main aim of this study is the reliability assessment of rainwater harvesting systems designed for a future period (2017-2030) in Birjand, the center of Southern Khorasan Province, east of Iran...

Introduction River flow prediction is one of the most important key issues in the management and planning of water resources, in particular the adoption of proper decisions in the event of floods and the occurrence of droughts. In order to predict the flow rate of rivers, various approaches have been introduced in hydrology, in which intelligent models are the most important ones. The application of artificial neural networks (ANNs) to various aspects of hydrological modeling has undergone much investigation in recent years. This interest has been motivated by the complex nature of hydrological systems and the ability of ANNs to model non-linear relationships. ANNs are essentially semiparametric regression estimators and well suited for hydrological modeling, as they can approximate virtually any (measurable) function up to an arbitrary degree of accuracy (Hornik et al., 1989). A significant advantage of the ANN approach in system modeling is that one need not have a welldefined process for algorithmically converting an input to an output...

Introduction Drought is one of the most important weather-induced phenomena which may have severe impacts on different areas, such as agriculture, economy, energy production, and society. From a meteorological point of view, drought can be induced by lack of precipitation, hot temperatures, and enhanced evapotranspiration. The efficiency of the drought monitoring system depends on the index which is selected based on the drought and climate conditions of the region. Precipitation-based drought indices, including the Standardized Precipitation Index (SPI) (McKee et al., 1993), China Z Index (CZI), (Percent of Normal Index) PNI, and others cannot identify the role of the temperature increase in the drought condition and in addressing the consequences of climate change. Recently, two new standardized drought indices have been proposed for drought analysis on multiple time scales: the Reconnaissance Drought Index (RDI) (Tsakiris and Vangelis, 2005) and the Standardized Precipitation Evapotranspiration Index (SPEI) (Vicente Serrano et al., 2011). The objective of this study is to evaluate the characteristics of drought, according to SPEI, SPI, and RDI. In addition, this study evaluates trends in meteorological drought frequency, duration, and severity during the study period through a multi-indicator approach and at low rainfall regions of Iran, providing a complete picture of the areas that suffered frequent and severe droughts in the past periods. Moreover, this might push towards the development of better frameworks for drought assessment, adaptation, and mitigation, in a possibly drier future...

Introduction The vortex tube is a structure with a slot along its longitudinal axis on top, which is installed across the width of the channel bed. This tube functions based on the gravitational force of sediment particles and swirling rotational force in the tube. It can transfer particles falling from its top slot to a specific side of the tube (Moazen and Shafai, 2003). Studies have shown the mechanism of this structure in separating the bed load. The current study used barriers with different shapes (square, triangle, and arched), heights and angles at the vortex tube upstream to increase the sediment trapping efficiency. These tests were conducted by changing the Froude number of the channel (flow hydraulic conditions). The results are provided below...

Introduction Climate change, in addition to increasing temperature, causes changes in the duration, intensity, form, and timing of rainfall in different parts of the Earth, which can cause droughts and floods. It also changes the volume, duration, and runoff duration, which will bring about many developments and changes in the water-resource management (Kamal and Massah Bavani, 2009). In order to reduce inconsistencies, studying the impacts of climate change on water resources is necessary. One of the most widely used models for these future studies is Atmosphere-ocean General Circulation Models (AOGCMs) (Wilby and Harris, 2006). In general, most studies present a high degree of uncertainty as a result of using AOGCMs in the simulation of climate change and hydrology parameters. the outputs of simulated water-resource models under climate change could be relied on when the uncertainties are taken into account at all stages (Semenov and Stratonovitch, 2010). In order to innovate the research method, in this study 10 AOGCMs under three greenhouse gas emission scenarios (A1B, A2, and B1) were used in the simulated range of hydro-climatic variables through climatic models and downscaling methods in the Dez Oliya basin during 2040-2069. In Summary, when reviewing the range of hydro-climatic variable changes in the future period, it could be observed that the uncertainty of AOGCMs under all three emission scenarios is greater than the downscaling methods...

Introduction Based on the previous research, the flow rate estimation by the DCM method has been widely used in compound channels and many computational models have been developed accordingly. Therefore, a compound channel dividing into sections according to the most accurate method is a requirement that all researchers agree. While vertical lines are used in models for dividing the compound channel into the main channel and floodplain, some researchers maintain that vertical lines have an inaccurate performance compared with horizontal and diagonal lines, especially for low discharge (Khatua et al., 2013, Mohaghegh and Kouchakzadeh, 2008, and Ozbek et al., 2004). However, the methods for discharge estimation based on the shear stress calculation uses vertical lines (Ackers, 1993, Shiono and Knight, 1991, and Bousmar and Zech, 1999). In this research, it has been attempted to present the best angle of the dividing line, which results in a 0% error rate calculated by comparing the effect of dividing lines with different angles on the calculation of the discharge of the compound channel...

Introduction Denil fishway contains a direct rectangular channel in different slope rates associated with special baffles inside the channel. The layout of the baffles provides an energy dissipation process which provides an acceptable operating condition for passing the fish in continues path along the channel. Denil fishway divides the current to two different parts, including the main current located at the middle of the channel and lateral currents along the frame position. The interaction between main and lateral currents provides the main process of mass and acceleration movement and concludes a significant energy reduction based on the turbulent process. In the other words, it can be concluded that the frequent baffles make the channel very rough, which results in a suitable condition for migrating fishes to the upstream (Cea et al., 2007). Rajaratnam and Katapodis (1983) conducted common research on the hydraulic of the fishway structures. They focused on the Denil fishway as one of the most important fishway structures among different types. The result of their study on the Denil fishway is the developed equation for measuring the discharge of the flow in the channel in various geometric scenarios. The physical model of the Denil fishway was constructed in the hydraulic laboratory at Alberta university, and the flow rate and velocity profiles were measured using the electromagnetic flowmeter and miniature velocimeter, respectively. Rajaratnam and Katapodis (1983) introduced six different Denil fishway types. The result of this study has shown that the output data are relatively similar to the Denil type 2. Equations (1), (2) are the main equations of the Denil fishway type 2 based on Rajaratnam and Katapodis (1983) studies...

Introduction In the pursuit of detecting the trend and the shift in trend in hydro-meteorological variables, various statistical methods have been developed and used over the years. Of the two methods commonly used (parametric and non-parametric), the non-parametric method has been favored over parametric methods. Long term trend analysis can reveal the beginning of the trend year, trend changes over time, and abrupt trend detection in a time-series. It is expected that the findings of this study will bring about more insights on understanding the regional hydrologic behavior over the last several decades in Iran...

Introduction The world population today is about 6. 5 billion, and it is estimated that it will increase to 9. 1 billion by the year 2050 (UN, 2004). It is estimated that irrigation consumes more than 80% of the good quality water. Due to the reduction in available water resources, the application of water-saving strategies, such as deficit irrigation and the use of underground water resources, can reduce water usage for irrigation. One strategy for the source control is to restrict the outflow in field drains such that the height of the water table is maintained at a shallow depth that allows certain crops to utilize groundwater to satisfy a portion of their water requirements. Shallow groundwater can be a significant source of water for agricultural production, especially during the drought period. The fraction of the crop water demand that can be met by shallow water tables depends on the crop grown, irrigation and drainage management, the soil type, the depth to the water table, and the shallow groundwater salinity(Ayars et al. 2006). A wide range of crops has been successfully grown that obtained a significant portion of the crop water requirement from shallow groundwater. The types of crops range from truck crops (pepper and carrots) to grain, hay, and some tree crops (e. g. date palm) that have salt tolerances from sensitive (lettuce) to tolerant (cotton). Although such observations have been made for moderately salt-tolerant perennial crops, such as alfalfa hay, vine and tree crops have a larger potential for in-situ water use from shallow groundwater than do annual crops because of their well-developed and established root system after the first growing season. Hutmacher et al. (1996) showed that cotton (Gossypium hirsutum L. ) crops can obtain 20 to 50% of their water requirement from shallow groundwater under the proper irrigation management. The timing and amounts of surface irrigation impact the extent to which crops will utilize shallow groundwater. Judicious use of deficit irrigation in combination with shallow groundwater management is necessary to achieve optimal results (Ayars et al., 1999)...