نشریه تحقیقات مهندسی سازه های آبیاری و زهکشی
سال بیست و دوم شماره 82 (بهار 1400)

Allocation of budget to pressurized irrigation projects is supported by the government to manage, saving water resources and increase agricultural production and is considered as the ideal project of the country. Cost-effectiveness and awareness of the cost of an irrigation system is important and necessary for the government. Therefore, estimating the initial and final cost of the project, especially irrigation systems, is one of the project management tools that allow project managers to make more accurate decisions at different stages. Finding a model to identify the important factors affecting the final cost of an irrigation system, as well as formulating it for use throughout the country and regions with different characteristics, is what the present study seeks.

The aim of this study was to estimate the cost of drip irrigation projects in the early stages of design using genetic programming technique, using data from 100 drip irrigation projects, in four sections including; cost of pumping station and central control system (TCP), cost of on-farm equipment (TCF), cost of installation and performing on-farm and pumping station (TCI) and total cost (TCT). First, a database containing 39 important and influential variables on the cost of the mentioned sections was prepared and the prices of the projects were updated for the base year of 2019. In the next step, the most important features that had the highest impact on the costs were selected using Eureqa Formulize software and using genetic programming. In the last stage, different models were presented in each section to estimate the cost and the best model in each section was introduced based on the statistics of accuracy and complexity.

The results of correlation analysis between independent variables and dependent variable (cost of each section) show that in TCP section PP variable (pump power required), in TCF section L16mm variable (total lateral length), in TCI section SR variable (plant row spacing) and in the TCT section, the HP variable (pumping height) with the correlation coefficient (R) equal to 0.766, 0.638, 0.355 and 0.429, respectively, had the highest value among the other variables and all were significant at the level of one percent confidence. Also, the results of cost modeling for drip irrigation system showed that in the TCP section, a model with an evaluation criterion of R equal to 0.449, MAE (average absolute error value) equal to 27236333 Rials and complexity of 22 was the best model. These evaluation criteria for the best model in the TCF section were equal to 0.848, 21198257 Rials and 13, in the TCI section equal to 0.770, 45483996 Rials and 11, and in the TCT section these criteria were 0.743, 77220845 Rials and 15, respectively.

In this study, the cost estimation of different parts of the drip irrigation system was modeled using genetic programming algorithm, and the obtained results showed that the presented models had excellent accuracies in each part. The results of this study can be a very useful tool for researchers, managers, students, consultants, contractors and those who are concerned in the water industry. By conducting similar research, it is possible to make an economic estimate with a high accuracy before the implementation stage. AcknowledgementThis article is extracted from the Ph.D. dissertation, the first author of the article. For this purpose, the authors of the article would like to thank the Department of Irrigation and Reclamation Engineering, Faculty of Agriculture Engineering and Technology, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran for their excellent cooperation, providing the necessary facilities for this research and the preparation of relevant articles. Keywords: Pressurized Irrigation, Cost Estimation, Genetic Algorithm, Feature Selection, Eureqa Formulize.

Today, one of the most important challenges of the present and the future, especially in the arid regions of the world, is the issue of water shortage and in some cases the water crisis. One of the ways to improve water productivity and better water management in agricultural sector as the largest consumer of water is the use of super-absorbent materials to improve soil texture, increase soil water retention, reduce erosion and increase germination. The aim of this study is to evaluate the effect of Aquasource superabsorbent polymer on physical parameters and soil-water characteristic curves (SWCC) of different soil textures.  

Aquasource is a new generation of potassium-based superabsorbent polymers that are biodegradable and free of destructive acrylamide compounds. In order to evaluate the effect of Aquasource hydrogel on hydro-physical properties of soils, some experiments in the form of a completely randomized design with 3 replications was performed. The first factor was different levels of superabsorbent (0, 0.5, 1 and 2% by weight of superabsorbent/soil) and the second factor was three different soil textures (sandy-loam, clay-loam and silty-clay). SWCCs related to all treatments were determined by determining the moisture content of the samples at different pressures (0, 0.3, 0.5, 1, 3, 6, 9 and 15 bars) using a pressure plate device. Then, to obtain the soil moisture characteristic curve parameters  in each sample, two softwares RETC (v.6.02) and Rosetta (v. 1.1) were used.  

The results of variance analysis and mean comparisons based on Duncan's test showed that in all soil textures studied, the application of superabsorbent and the increase Aquasource amounts, increased the moisture contents at the field capacity and permanent wilting point. However, the highest amount of soil available water for plant use in sandy loam, clay loam and silty clay textures was 9.8%, 13.8% and 12.7%, respectively, and they are related to the use of 0.5% w/w of superabsorbent in these treatments (Fig. 1). The use of larger amounts, up to 2%w/w, reduced the soil available water for plant use. This issue can be related to the reducing the interaction of soil particles and polymers with increasing the amount of superabsorbent application in soil. At high levels of superabsorbent consumption, the contact of the hydrogel with the soil particles is reduced, followed by the aggregation of the superabsorbent. This prevents the proper exchange  between the superabsorbent and the surrounding soil, and thus despite the presence of moisture in the soil-superabsorbent system, this moisture cannot be used for the plant, so that in all three soil textures the lowest amount of plant available water belongs to the treatments of 2% w/w of Aquasource. The results of statistical analysis for estimating the parameters of the soil-water characteristic curve due to the application of different levels of superabsorbent in different soil textures using two software RETC (v.6.02) and Rosetta (v. 1.1) showed that the fit The Van-Genuchten (Moallem) model in RETC software in all treatments has provided a good approximation of the parameters of the soil-water characteristic curve (R2> 0.98). Also, with increasing the amounts of superabsorbent, the accuracy of the model in estimating the parameters decreased to some extent.    

Application of Aquasource superabsorbent and increasing the application level of this superabsorbent polymer (from 0 to 2% by weight of superabsorbent/soil) in sandy-loam, clay-loam and silty-clay soil textures caused an increase in the moisture content at field capacity and permanent wilting point. Application of 2% W/W in sandy-loam, clay-loam and silty-clay soil textures increased the moisture content at the field capacity by about 2.4, 1.6 and 1.5 times, respectively, compared to the control treatments of each soil textures. However, the highest amounts of plant available water in all three soil textures were obtained by applying 0.5% W/W (superabsorbent/soil). Application of 0.5% W/W in sandy loam, clay loam and silty clay textures increased the plant available water by about 1.23, 1.19 and 1.12 times compared to the control treatments in each soil textures, respectively. However, the use of larger amounts reduced the plant available water. At low levels of Aquasource application, the interaction between the   superabsorbent polymer and the soil particles in the soil/polymer system facilitates the transfer of moisture stored in the superabsorbent to soil particles. However, increasing the application level of this polymer up to 2% W/W has an inhibitory effect and in this case, the interaction between the polymer and soil particles is reduced, which leads to a lack of proper drainage of moisture from the polymer.   Acknowledgement The authors would like to thank Agricultural Engineering Research Institute for supporting this research.

Development of modern irrigation systems has been one of the main programs in developing agricultural sector in the past few decades. Assessing the role of these systems in increasing indicators of irrigation water management can play an important role in future national policies and planning. Therefore, this study was conducted with the aim of appraising water consumption management indicators in tomato production in different regions of Iran and evaluating the role of surface drip irrigation systems in increasing these indicators.

In this study, a field survey was conducted to measure yield and applied irrigation water of tomato under the farmers’ management in tomato production hubs. Volume of applied water by farmers in 176 farms in Fars, South Kerman, Hormozgan, Bushehr, Khorasan Razavi, Qazvin, Khuzestan, Golestan, Zanjan, Hamedan and Semnan provinces with different conditions of climates, irrigation methods (furrows and drip), salinity of irrigation water and soil; and different tomato cultivars were measured during growing season 2018-2019. The measured applied irrigation water values were compared with the net irrigation requirements estimated by the FAO Penman-Monteith method using meteorological data from the last 10 years, as well as the values of the national water document. Then, the effect of modern irrigation methods (surface drip irrigation) on applied water, application efficiency and physical water productivity was investigated in the study areas. Crop yield was recorded at the end of the growing season and water productivity (WP) was calcucated as the ratio of yield to total applied water (irrigation water and effective rainfall). Analysis of variance was used to investigate the possible difference between yield, applied water and WP among the hubs. Data adequacy was assessed by using the method provided by Sarmad et al. (2001).

The results showed that yield, applied irrigation water and WP in tomato production hubs were significantly different at the P ≤ 0.01. The average volume of applied irrigation water by the farmers was 7729 m3/ha. Water productivity in production areas varied from 4.33 to 9.52 kg/m3 and its average was 7.10 kg/m3. The average net irrigation requirement and irrigation application efficiency were 674 mm and 78%, respectively. Irrigation application efficiency obtained from the studied tomato farms was slightly higher than the average irrigation efficiency in Iran reported by Abbasi et al. (2016). Deficit irrigation was occurred in the fields of some areas such as Bushehr, Golestan and Semnan. Tomato planting time (spring or autumn) affected applied irrigation water, yield and WP. The volume of water used in autumn planted farms (5356 m3/ha) was less than spring planted farms (9831 m3/ha). The average yield of tomatoes in spring planted farms (74.3 t/ha) was significantly higher than the yield of fields planted in autumn (46.1 t/ha). However, the average of WP in spring planting farms (7.7 kg/m3) was higher than the productivity of farms planted in autumn (6.6 kg/m3). The application of surface drip irrigation systems in comparison with furrow irrigation resulted in 25% reducing in applied water, 10% increasing the application efficiency and 16% improving in water productivity.

In general, the results of this study provide useful information on applied irrigation water management indicators in tomato production to managers and water decision makers within Iran. Proper development and management of drip irrigation systems for row crops such as tomatoes and autumn planting of tomatoes in warm tomato production hubs is recommended for effective use of autumn rainfall. Also, training and application of methods to improve the performance of surface irrigation (using methods to reduce evaporation and the use of low pressure systems) is recommended to increase irrigation efficiency and reduce applied irrigation water.

Since the 1990 s, a number of countries adopted the transfer policies or irrigation management ‎transfer (IMT), and in some cases, the incentive to reform water laws was provided (Bruns et al., ‎‎2005). Making of the investment decisions and water allocation by local and private organizations ‎requires that the‏ ‏water users‏ ‏have confidence in the quantity and time they receive water and this ‎requires the existence of legal transparency. Therefore, water laws should provide a full and ‎indispensable set of rights for use of water (Bayat et al., 2016). In this study, by focusing on the ‎privatization of agricultural water, relevant law clauses were extracted during different periods, and ‎the effectiveness of these rules on management of water resources was analyzed‏.‏

In this study, the purpose of “law” is all ratification of parliament, official codes, and ‎administrative regulations. Since land containing groundwater resources are usually governed by ‎private management, the focus is on the rules associated with irrigation networks with surface water ‎resources. To implement the study all documents related to water laws, approved by various ‎organizations of the country, included the resolutions and bills of the Islamic Parliament of Iran, ‎national development plans, the resolutions of the Supreme Council for Water, the efforts of the ‎relevant Ministries, and published procedures and executive regulations. Then the material related to ‎the issue of privatizing and reducing the government’s leadership and authority, or common and ‎applicable laws that lacked relevance to privatization issues were extracted from them and, besides ‎international documents in this regard, were analyzed in a descriptive way‏.‏

Until 1929, water governance issues were solved by the common rule of society in the ownership ‎of wells and qanats. Then, by compiling civil code, water governance was enforced using this law. In ‎‎1944, with the approval of the law allowing the establishment of the irrigation agency, the ‎individual aspect of irrigation was limited to traditional water rights and the government supervised ‎all irrigation affairs. In this period, for the first time, public and private institutions were allowed to ‎build and invest in irrigation networks. By approving the establishment of companies to exploit ‎lands downstream of the dams, the exploitation of command area of irrigation networks was given to ‎natural persons and non-governmental individuals. After the Islamic revolution, according to the ‎constitution and the approval of the cabinet of ministers, the government was obliged to dispose of ‎its shares in the operation of irrigation networks by maintaining state ownership of the ‎infrastructure. Nevertheless, the devolution of these private companies only occurred in the ‎ownership of the shares and these companies are still dominated by the government in management, ‎structure and the way of referral. The development plans of the country and the approvals of the ‎supreme council of water have stressed the acceleration of the privatization process and the ‎reduction of government incumbency in water projects, but financial support and the executive ‎program have not been taken into account to meet their goals. The set of criteria for operation and ‎maintenance of irrigation networks was notified to the ministry of power in 2005. However, except ‎for identifying the competence of companies, other parts of it could not be implemented, so it is ‎needed to update these instructions. In the study of international experiences of water reform with ‎the approach of privatization in developed (United States and France) and developing countries ‎‎(Chile, Mexico, Turkey and India), some cases such as clear and transparent water rights with ‎guarantee the implementation of the rules, financial independence of water custodian, appropriate ‎water pricing, establishing a legal framework for privatization process and conducting regular ‎assessments to evaluate the results of transfer of management is considered as the most important ‎measures in water privatization.‎

‏‌‏Conclusions

By changing the policy of government from centralization to the participation of the private ‎sector and the stakeholders, the current laws in the field of water resources need to be reviewed. Due ‎to the importance of the subject, in this research, we proceed to aggregation rules and procedures ‎related to this discussion and review the consequences of implementing laws and policies of ‎privatization in irrigation networks. The results showed that although there are laws and regulations ‎to attract private sector capital, the time of implementation of water plans and low investment ‎profits has prevented the private sector investment in this sector. The generality of laws, disregard ‎for restrictions, climatic conditions and political changes in the country (such as change of ‎government), has made the implementation of water development programs less effective. In ‎addition, attracting the full political support at high levels of management and legislation of the ‎country, and the use of simple legal framework with accordance of the capacity of water users, were ‎the main factors in success of pioneer countries in water privatization.‎

Iran is a land of low rainfall and due to the consequences of climate change and the existence of drought, water loss should be prevented in any way to eliminate water shortage in the country. In the province of West Azerbaijan, a large amount of water is lost every year due to evaporation.Solar energy is known as free and clean energy and even the main source of other types of energy on the earth. The scarcity of fossil fuel, as well as non-uniform distribution of this kinds of energy source in the work, motivate humans to find other types of energy especially clean and sustainable solar energy. Nowadays, the rising earth population and impacts of fossil fuel on the environment leads to accelerate the construction of solar power stations (Turki and Abedi, 2012). Owing to the location of Iran in suitable latitude and altitude, the country has a sunny and dry climate. Therefore, the significant magnitude of The sun's radiant energy reaches the earth's surface. On the other hand, the hot and dry climate of Iran makes high evaporation of water from reservoirs of dams. Covering the surface of freshwater reservoirs with physically thin covers could prevent or reduce the evaporation rate of water. Soltani et al., (2015) reported that water evaporation in aquatic environments could be reduced up to 10% in the presence of the planet. Rezzade et al., (2017) informed that scattering of colored floating balls could prevent evaporation rate from medium to small reservoirs up to 71.5%. Based on their results, the white color balls are more effective than the dark colors such as black in control of evaporation under similar conditions. One of the common means to cover the surface of reservoirs large dam in order to reduce evaporation of water is to use solar panels.

In this study, the reduction of evaporation from the Nowruzlu diversion dam was investigated by using solar panels. This high diversion dam is located in the northwest of Iran, province of West Azerbaijan. The dam is constructed to divert the resealed water from Boukan earth dam to supply agricultural demands left side intake and domestic, industrial and agricultural demands by right side intake. The height of the dam is about 10 meters, the lake area is 0.2 km2, and the volume of water is more than 14 MCM. The object of this method is not only to reduce evaporation from the reservoir of the dam but also to produce clean solar energy for the domestic energy supply. For this purpose, the actual evaporation of the dam lake water was estimated using the data of Noruzlu dam climatology station. With PVsyst software, the amount of solar energy load in the Norozlo dam range was extracted. Finally, the project was economically evaluated and its profitability was analyzed. In this research, we used recorded evaporation data from the local synoptic station located in a dam site based on a standard A class pan. The solar energy potential was estimated by using the photovoltage software PVSYST model. The software provides an effective tool to simulate and calculate the distribution of energies throughout the year in any region on the earth. The output of the software is categorized in three was as follows based on the software documents: • The total energy production [MWh/y] is essential for the evaluation of the PV system’s profitability. • The Performance Ratio (PR [%]) describes the quality of the system itself.• The specific energy [kWh/kWp] is an indicator of production based on the available irradiation (location and orientation).

The numerical analysis to evaluate installation circumstances for solar panels revealed that, by 36o inclination, 2 kw/m2 energy would be produced. In order to supply domestic requirements of 1000 houses, 2568 m2covering of lake surface will be sufficient. Hence, via the mentioned states, 2Mw electricity will be produced, in another word, the annually produced energy could be more than 730 Mw. The results showed that according to economic estimates, the average cost for self-sufficiency in electricity consumption in 5 villages (each of them with 200 houses) around the dam is about 37,680 billion Iranian rials (IRR). By calculating the revenue from the reduction of evaporation and electricity generation, the return on investment of this technology will be compensated in 5.7 years.

Density difference causes density flow. Density flow is the the movement of the forehead, body, and tail of the heavy fluid into the ambient flow, and the buoyancy or gravity force causes the drive force. The movement of dense current under clear water creates a shear layer at the interface between clear water and density fluid. Therefore, at the interface, many cuts and vortices are created and this causes the entrainment of smooth water and density flow, which reduces the amount of density difference and the buoyancy force. Hosseini & Fattahi (2020) showed that the variations in the waterway shape causes higher velocity of density flow and decreases the flow thickness. Also, increasing the density of density flow, increases the maximum velocity in velocity profiles. This increase in the maximum velocity of the density flow is more pronounced in streams with higher inlet flow. The velocity profile patterns in the wall and jet area of the density flow body are influenced by the flow regime.

In this research, the density flow is illustrated in 3 different models according to Figure 1. The opening rate of the density flow valve is considered to be 1 cm. In this research, we have tried to show the effect of curvature at 180 ° bend and sinusoidal shape restricted channel and the flood plain. In this simulation the channel with 4 different longitudinal slopes, 0.002, 0.005, 0.008 and 0.02, are modeled and also 4 different densities, 0.00667, 0.00727, 0.00859 and 0.01 g / cm3, and 4 f Froude numbers, 1.2, 3, 5 and 8, have been used. Moreover six different mesh gridding for the flood plain and six different mish gridding for the channel are considered. it should be mentioned that 6 types of turbulence models ( The k-e model (standard, RNG, investigable), the kw model (standard, SST) and the RSM model (linear strain-pressure) are used.

Four types of networks were selected for finite channel with sinusoidal curvature. Figure (3) compares the different mesh gridding with the tested mesh and it was observed that in the range close to the bed, at high speeds, meshes with dimensions of 60 × 20 × 140 are very close to the experimental model developed by Hosseini & Fattahi (2020). Also, considering all 3 optimal models for turbulence models, k-ε models can be considered more optimal than k-ω and RSM models. The effects of the increasing slope of the flume bed in the wall area is more tangible than in the jet area while Froude number and input density are the same. On the other hand, increasing the slope of the channel bed from 0.2% to 2%, reduces the density flow thickness along the channel. As a result, the flow velocity shows an increase in the density flow which causes the growth of the drive force and will increase the turbulent flow velocity by increasing the inlet Froude number from 1.22 to 8. In all laboratory data, the density current concentration profile in the jet area shows a higher dispersion of 47% than the wall area. By increasing the slope of the channel from 0.2% to 2%, the dispersion rate increases by 65%. Richardson data and entrainment ratio in model No.1 increased by 10% compared to the experimental model and also these data increased by 19% in model No.2 compared to the experimental model.

In this research, we tried to simulate the three-dimensional density flow in models with 180 degree bend and limited sinusoidal curvature as well as sinusoidal patterns with plain flood. Also, the most optimal computational mesh, turbulence model, slope, density and Froude number are investigated as long as the studies include the depth profiles of velocity, density, turbulence, etc. in a situation where the channels are curved. Moreover, by increasing the number of Froude numbers from 1.22 to 8, due to model number 1 with 180 degree curvature, the pattern of density profile decreases by 19% and 21.3% compared to models number 2 and 3, respectively. Also, in all laboratory data, the density current concentration profile in the jet area shows a higher dispersion of 47% than the wall area. With increasing the slope of the channel from 0.2% to 2%, the dispersion rate increases by 65%. Richardson number has established a significant relationship with the entrainment ratio, which has a correlation of 0.71. Also the numerical entrainment ratio (for all three models) increased by 4.4% compared to the experimental model.AcknowledgmentsWe would like to thank Water and Hydraulic Laboratory of Shiraz University for their effective cooperation.

Taking water from rivers is one of the most important topics in hydraulic engineering. One of the problems associated with most intakes is the accumulation of sediments in intake entrances. Failure to control the sediment's entering the intakes results in its transfer into irrigation channels and their establishment that creates many problems due to sediment transport or its settlement in various parts. Due to the development of computing systems as well as unmeasurable complexities of water flow and sediment in laboratory models, using numerical simulations can be very effective and substantial in hydraulic investigation of such flows. Flow passing through the lateral intakes and channel junctions is usually turbulent. Turbulence is one of the most important features of the flow pattern in a bend which influences a lot of processes occurred in rivers including erosion, sediment transport, bed morphology, and shape of natural channels. Investigating the kinetic energy of flow turbulence in open channels due to the maximum shear flow of the bed and the scouring of the floor is very important and can be considered for prediction of bed topography. The accumulation and sedimentation in water intake and reduced intake efficiency is one of the problems that arise in most intakes.

Therefore, in the present study, the sediment controlling structure, a skimming wall, was used in front of the intake. Then, the three-dimensional flow in sedimentary bed around the intake entrance was simulated by Flow3D model and results were compared with experimental model. In this research to increase intake efficiency and control the amount of sediment entering the intak, two structural skimming wall in front of the intak and spur dike on the opposite shore it is used. In the research using three-dimensional flow field numerical model FLOW3D around 60 ° lateral intake located on the direct path was solved numerically and counters velocity and turbulence kinetic energy is drawn. The experiments conducted and results were compared with the numerical model. Flow hydraulic and dynamics in front and inside the intake is studied. Velocity vectors inside the intake, in both longitudinal and lateral directions were compared with experimental results.

In the absence of structures, inside the main channel, the flow separation width at levels close to the bed is broader than the higher levels. However, by installing skimming wall in front of the intake, the flow separation close to the substrates carrying more sediment is reduced and it is increased on the surface that has less sediment. It also allows less sediment into the intake. In the absence of structures, the surface flow lines in the intake tend to the right wall and the bottom flow lines tend to the left wall. The width of separation zone on the surface is broader than the one on the floor. In presence of skimming wall structure or both skimming wall and spur dike, the flow lines near the bottom tends to the channel center. In addition, the zone with stagnant flow on the left side of intake is broader at the bottom than on the surface. In all three cases, the maximum longitudinal velocity and the maximum resultant velocity have occurred at the beginning of the intake inlet in its left corner. The maximum transverse velocity has occurred in the intake center. In these figures, there are areas with secondary vortex flow on downstream and the left of the intake.

The results showed that by adding the structure of the spur dike in the main channel, the velocity in the main channel is 1.5 times compared with the other two cases. and the area inside the intake also affects. Also, the tip of the axis of the velocity vectors is displaced to the intake. As a result, In the back area of the spur dike, the longitudinal velocity decreases and there deposition. Comparison of the distribution of the maximum kinetic energy of flow turbulence at two different depths indicates a 50% increase in the maximum kinetic energy of turbulence in the upper layer compared to the lower layer.