نشریه تحقیقات مهندسی سازه های آبیاری و زهکشی
سال بیست و چهارم شماره 92 (پاییز 1402)

The aim of this research is to optimize the design parameters of underground drainage systems with an economic approach. The study of the relationship between the depth and distance of drain installation has been the subject of many researchers, each of whom has tried to reduce the costs of drain implementation. In this research, genetic and multi-world algorithm optimization model was used to optimize the main design parameters of the underground drainage system of regional agricultural lands around Gorgan city. The area of the construction area of the drainage system was around 200 hectares. In this research, by using genetic and multi-world algorithm, the design parameters were selected in such a way that they lead to the lowest implementation cost of the underground drainage system. In this regard, the design parameters have been selected by combining Hohhot's permanent equation and optimization algorithms.

The area under study is Aliabad district, one of the functions of Gorgan city. The lands of Ali Abad region are also located in the upper part of the plains. These lands are located in eastern longitude and northern latitude. The study area covers about 200 hectares.
Genetic Algorithm:Genetic algorithm is an optimization method inspired by living nature, which can be referred to as a numerical method, direct and random search in classifications. This algorithm is based on repetition and its basic principles are adapted from genetic science.
Multi verse Algorithm:The big bang theory considers the occurrence of a big explosion as the beginning of the origin of our universe. According to this theory, the big bang is the origin of everything in this universe and nothing existed before it. A population-based algorithm performs the search process in two stages: exploration and exploitation. In this algorithm, the concepts of white hole and black hole are used to explore the search space. In contrast, wormholes help exploit search spaces.

Genetic Algorithm:By applying the genetic algorithm optimization model to the data of the studied lands, the optimal parameters were calculated. Table (4) shows the design parameters obtained from the genetic algorithm optimization model in different drainage coefficients for the allowed depth of drain installation. Considering the entire search area (permissible depth of drainage installation from 1.5 to 3.5 meters from the ground surface), the results obtained from the land input data of the studied area showed that taking into account the drainage coefficient of 2.5 mm per day, the minimum cost the equivalent of 51.3 million Tomans has happened in 8 hectares at a depth of 2.62 meters from the ground surface with an installation distance of 79.9 meters and a diameter of 125 mm.
Multiverse algorithm
The optimal parameters were calculated by applying the multi-world algorithm optimization model. Table (7) shows the design parameters obtained from the optimization model in different drainage coefficients for the allowed depth of drain installation. Considering the entire search area (permissible depth of drain installation from 1.5 to 3.5 meters from the ground surface), the results obtained from the input data of Aliabad lands showed that taking into account the drainage coefficient (discharge intensity) 2.5 mm per the minimum cost equivalent to 51.5 million Tomans has happened in an 8-hectare unit at a depth of 2.61 meters from the ground with an installation distance of 79.5 meters and a diameter of 125 mm.
Comparing the results of genetic and multiverse algorithms
Comparing the performance of genetic and multi-world algorithms shows the high efficiency of both algorithms in solving the problem of optimizing the diameter of drainage pipes and their installation depth. Both algorithms have almost the same performance in solving this optimization problem; So that both algorithms in the distance of the impervious layer to the depth of the drain installation (D) is equal to 2.25 meters, the stabilization depth of the water table (in the middle of the two drains) from the ground level (H) is equal to 1.5 meters and intensity Drainage or drainage from the surface unit (q) is equal to 4 mm per day, and they have calculated the optimal depth of drainage installation to be 13.3 meters

The design of drainage systems consists of choosing three parameters: depth, diameter and distance of drains. Various approaches can be used to choose the best combination of three parameters. One of the approaches can be to reduce the costs of implementing the drainage system. In this research, using the genetic algorithm, these parameters were selected in such a way that they lead to the lowest implementation cost of the drainage system. In this regard, the design parameters have been selected by combining Hohhot's permanent equation and genetic algorithm.

In the quantitative model development of the Nexus chain within the boundaries of irrigation networks, the role of social parameters is as much important as technical parameters if it is not higher. The social parameter’s role is essential in the explanation, definition, and description of the governing equations. The social parameters explain many systemic archetypes and become the balancing or reinforcing factor of some system loops. Of course, the main goal of extension programs is not limited to agricultural development; Rather, it aims to solve the three basic problems of third world rural communities, i.e. weak production, lack of equality in income distribution and lack of participation of villagers in social activities, so as to pave the way to achieve sustainable rural development in all its dimensions and elements. Nevertheless, although sometimes agricultural education and extension programs are considered ineffective and undesirable; But it cannot be ignored in the present and future development of rural areas.

Agricultural education and extension factors are the parameters that affect technical parameters in several aspects. These factors affect the cultivation pattern, method of water use, amount of required water, and irrigation management. The conceptual and quantitative model of the Nexus chain in the boundaries of the Qazvin irrigation network is developed. In addition to several technical relevant parameters in the Nexus chain, the agriculture extension is considered as well. The effects of agriculture extension parameters were investigated on the three integrated systemic archetypes defined in the model (a subsystem of "limit to growth" of agricultural expansion, "shifting the burden" of groundwater resources problem and "fixes that backfire" of development of arranged delivery).

• According to the extraction of the available historical education data in the last twenty years from the sites affiliated with the Ministry of Agriculture, the equations in the three subsystems were calculated by multivariable linear regression and curve regression.
The model was run for the years 2005 to 2016. Verification and validation tests were performed for the model and its results were interpreted for the Nexus index. It should be noted that all the input data in the model were entered into the model in a standardized way and the results between zero to one were calculated in a dimensionless manner. Nexus index is a linear combination of 8 partial indices in Qazvin irrigation network: water productivity in food, surface productivity in food, energy efficiency in food, economic productivity of food, economic productivity of water, economic productivity of energy, food production index in the network relative to the province and the index of the amount of water delivered to the water demanded. Because each part of the training was effective in a different variable; Therefore, the amount of changes in that variable was observed and their changes were recorded, and finally, in loading the model during the years of implementation of the model, the amount of the Nexus index, which was a combination of all three trainings; It was observed that they are shown in the diagrams of figures 6 to 8. and figure 9 shows changes on Nexus index in modelling years.
• The model was set for the coming years (by 2031). For this purpose, all inputs of the model were calibrated until the aforementioned year. By implementing the model, it is possible to monitor the effects of training on key indicators and finally the nexus index and study their effectiveness. Diagrams 9 to 11 show the impact of the continuation of the current trend in the farmers' training system on the vital parameters of the Nexus chain in Qazvin irrigation network. Also, the diagram in Figure 12 shows the effect of the downward trend in the education system on the trend of the Nexus index. It should be noted that the water productivity index reflects the training parameter in the direction of reviving water resources, and the index of the ratio of delivered water to the requested water reflects the network's utility index, which itself reflects the adjustment of the water demand from the network and ultimately reflects water storage in Qazvin network, and finally, the index of the ratio of agricultural products produced in the network to its similar amount in the province reflects the training parameter in line with the method and pattern of cultivation in the irrigation network.
The existing relationships in these interactions as well as the amount of their variations in the differential equations of each subsystem indicate the effectiveness of the agricultural extension activities on the subsystems. According to the developed regression equations and considering the effect of balancing extension parameters, it is expected that the increasing extensional activities as a policy lever will stop or at least balance the decreasing utility and weakening performance of the irrigation system.

Data assimilation is a scientific method which integrates information from the actual measurements and the model predictions within a defined framework to enhance the accuracy of the estimations of variables or parameters under investigation. This process comprises of two phases called prediction and update. In the prediction phase, the model estimations are computed using the Monte Carlo simulation method. This process continues until observation data (measurements) becomes available. In the update phase, model estimations and observations are combined, taking into account the confidence level associated with each one of the data sources (observations, and model estimations), resulting in posteriori estimates (updated outcomes). This study focuses on improving the accuracy of the estimates of the soil moisture contents at root zone depth using the ET estimation model suggested for non-standard conditions by FAO 56 (Allen et al., 1998) through the utilization of two data assimilation methods namely the Ensemble Kalman Filter (EnKF) and the Particle Filter (PF). ET was calculated according to the Surface Energy Balance (SEBAL) algorithm using Landsat 8 satellite imagery as observation data for the data assimilation system. In order to ascertain the effectiveness of the data assimilation methods applied, results obtained from a data assimilation system (referred to as BL) which was implemented in two sugar beet fields and two corn fields in the Jovein region were utilized. In the BL system, simulated soil moisture contents of the root zone layer obtained by numerically solving the Richards equation were combined with the soil moisture measurements taken at specific points in the fields using soil moisture sensors (TDR). 51 TDR access tubes were installed in the fields to measure soil moisture contents at various depths using Time Domain Reflectometry (TDR) sensors. Soil moisture measurements were recorded from Khordad to Aban 1399 (write in English calendar).The essence of data assimilation methods lies in the amalgamation of homogeneous information about the studied phenomenon obtained through different mechanisms. In this study, the observations utilized included ET calculated based on the SEBAL algorithm. In the FAO-56 model, evapotranspiration and soil moisture content of the surface and root zone layers were computed. Since soil moisture contents of the surface and the root zone layers serve as the initial conditions for subsequent simulation steps, data assimilation was applied to the soil moisture content instead of the ET. To achieve this, ET obtained from the SEBAL algorithm was converted into soil moisture content and subsequently used in the data assimilation process.The average standard deviation of the simulated soil moisture contents (σ) in the PF and EnKF approaches was 36% and 32% lower, respectively, compared to the open-loop (OL) approach. Throughout the growth period, PF and EnKF consistently resulted in lower σ compared to OL in the three fields which were irrigated by center-pivot irrigation systems. However, following each irrigation event in the field M, which was irrigated by a drip irrigation system, σ suddenly increased and became nearly equivalent to OL. This was attributed to the greater depth of irrigation water in this field as compared with the other three fields. On the average, the magnitude of σ change (σΔ), representing the reduction in σ before and after the update, was 0.032 and 0.037 for PF and EnKF, respectively. Consequently, the results suggested that data assimilation reduces the uncertainty of simulation results.The research findings indicate that data assimilation significantly reduced the BIAS and nRMSE indices compared with the OL approach. The average BIAS for EnKF, PF, and OL was 0.018, 0.020, and 0.028, respectively, while the average nRMSE for the three methods was 17.3%, 17.5%, and 18.9%, respectively. In other words, the use of ET observations obtained from Landsat 8 satellite imagery and the SEBAL algorithm significantly improved the accuracy of the estimation of ET with the FAO-56 model. Therefore, the obtained results suggest that data assimilation can be employed to enhance the accuracy water consumption estimates and to improve irrigation management.

With the occurrence of flood, the velocity and depth of the flow in the river increases and the flow enters the flood plains. The velocity difference between the deeper section and the shallow area causes the transfer of momentum between these areas and complicates the flow structure. The formation process of secondary flows and its pattern in compound channels have been investigated by researchers such as:Tominaga & Nezu, 1991. The presence of vegetation on flood plains causes complexity in the analysis of hydraulic problems of compound channels. For example, Hamidifar et al. (2012, 2014), using laboratory measurements, showed that the presence of vegetation reduces the flow through the cross section by about 30%. At the same time as the water level rises during the flood, the deck of the bridges will go under water and the current passing under it will be pressurized. In this condition, the flow field is affected by the presence of vegetation, compound channel and pressurized flow. In this research, the laboratory investigation of these complex conditions has been done.

The experiments of this research were done with 3 geometric ratios of the compound cross-section, 3 relative depths, 3 vegetation densities, and control experiments in a compound channel with a length of 10 meters and a width of 1.5 meters. The measurement of the flow velocity parameter, the scouring rate of the bridge pier in the conditions of pressurized flow has been done according to the variables mentioned above.

Comparison of depth velocity and logarithmic velocity distribution in the condition without vegetation on the flood plain, the sign shows that in all sections, the distance between the channel bed and the water surface, the difference between the measured velocity values with the logarithmic distribution of the velocity increases. This difference is due to the presence of the bridge deck and the flow retardation. Also, vegetation causes the depth distribution profile of flow velocity to deviate from the curve of logarithmic flow velocity, and the biggest difference will occur in the upstream area between the interface of main channel and flood plain. This phenomenon increases the amount of apparent shear stress between the main channel and the floodplain.With the increase in the density of vegetation, the percentage of floodplain participation in the total discharge is reduced by 20%. The highest participation percentage of floodplain is about 30% in the state without vegetation. In different densities of vegetation with an increase in relative depth from 0.3 to 0.5, the percentage of floodplain participation in the total discharge is less than 10%. With the increase in the density of vegetation, the difference between the percentage of floodplain participation in different cross section widths has decreased.

The findings of recent research to check hydraulic parameters can be summarized as follows:- Increasing the density of vegetation increases the longitudinal velocity in the main channel and decreases it in the floodplain.- Longitudinal velocity and averaged- depth velocity in the main channel in the case without vegetation is lower than the case with vegetation.- Increasing the relative depth increases the percentage of floodplain participation by an average of 5%, and the increase in vegetation density causes a decrease of 17% in the floodplain participation.- With the increase in the vegetation density of the floodplain, the velocity changes in the floodplain decrease compared to the main channel.- Examining the profiles of the depth distribution of the flow shows that due to the presence of the bridge deck and the retardation of the flow, the depth distribution differs greatly from the logarithmic distribution of the velocity . This is despite the fact that in the conditions without the presence of the bridge deck, this amount of difference reaches its minimum.- The presence of the bridge deck and the creation of backwaters reduce the difference in flow velocity in the main channel and floodplain upstream of the bridge, and this in turn reduces the strength of the secondary currents between floodplain and the main channel.- The difference between the global average velocity of the flow and the local velocities increases the slope of the (a-1) and (b-1) lines due to the flow retardation.

Alfalfa is irrigated by drip, strip, Furrow and rain irrigation methods. Surface irrigation methods are unjustifiable and not economical due to the low potential of irrigation efficiency in dry areas. Rain irrigation methods cannot be justified in hot and dry areas due to high evaporation and high water requirement of alfalfa. Alfalfa is a plant whose leaves are sensitive to burns caused by poor quality water as a result of water spraying in the rain irrigation method (Hengeller, 1995). Micro irrigation methods (surface and subsurface drip) are among the alternative methods of rain methods. The subsurface drip irrigation method has not been developed in Iran due to the existence of ambiguities and some dark and unclear points regarding its efficiency for crops (clogged outlets, salt accumulation, risk of blockage of pipes by roots). These concerns require that before any development of subsurface drip irrigation method for different crops, necessary researches should be done in this field. Therefore, conducting any research on the efficiency of this method for alfalfa, which is a valuable fodder plant but requires a lot of water, seems necessary. This research was conducted with the aim of investigating the effect of subsurface drip irrigation method on alfalfa yield, the amount of water consumed and determining the appropriate distances and depths for sub-pipes.

In order to investigate the effect of installation depth and distance of irrigation strips (laterals) in subsurface drip irrigation method on yield and water use efficiency in alfalfa cultivation, a study was conducted for two years on the farm of Damghan Agricultural Research Station. The design was implemented in the form of split strips based on randomized complete blocks with two factors and three replications. Factors included: 1- Distance of irrigation strips from each other in three levels (80, 100 and 120 cm) 2- Depth of installation of irrigation strips in two levels (30 and 45 cm below the soil surface). Depth of strips installation was considered as the main factor and distances as the sub-factor. The length of each experimental plot was 60 m and the width of the plots for the distances of 80, 100 and 120 cm were selected as 4, 5 and 6 m, respectively. Strips irrigation with a with a diameter of 20 mm with a discharge of 1.6 (lit/hr) and a distance of 60 cm for each dropper were selected. After preparing the ground and sowing the seeds, the subsurface irrigation pipes were placed (according to the treatments) with using the machine. Irrigation water was calculated by Penman-Monteith method and was given to the plant with an irrigation cycle of 4 days.

The results showed that the effect of pipe spacing on product yield (dry matter) and water use efficiency was significant, but the effect of pipe installation depth on yield and water use efficiency was not significant. The interaction effect of distance and depth of tapes irrigation on crop yield and water use efficiency was significant. There was no significant difference between crop yield in treatments with lateral distance of 80 and 100 cm. With increasing lateral distance from 80 to 120 cm, crop yield decreased sharply. Due to the yield of treatments and the cost of subsurface drip irrigation, the treatment of lateral distance of 100 and depth of 45 cm was suggested as the superior treatment.

The subsurface drip irrigation method for perennial crops is one of the efficient and appropriate methods. This method has a much higher efficiency than other irrigation methods due to the reduction of evaporation losses and the increase of irrigation efficiency especially in arid and semi-arid areas. The non-interference of irrigation in this method with the traffic of agricultural machines (especially during harvest) increases the ability and functionality of this method. But one of the problems of this method is the damage of rodents to the sub-pipes under the soil surface, which makes it difficult to determine the places of damage and repair them. Based on the results of this research, to prevent the damage of rodents, it is recommended to fight against these rodents and also to increase the installation depth of secondary pipes up to 50 cm. Clogging of droppers caused by poor filtration performance and penetration into and around the pipes are other problems of this method. To avoid these problems, it is recommended to inject acid and herbicide regularly into the irrigation system.

It is possible to effectively control water in paddy fields, prevent flooding problems, and create optimal conditions for the growth of agricultural products with simultaneous and correct management of irrigation and drainage. Due to the high initial cost of the construction of subsurface drainage, Mole drainage is a suitable and more economical alternative in clay soils. Constructing the mole drain at a critical depth and passing the water through the cracks, improves the soil conditions and removes excess water from the soil surface. Mulqueen (1985), reported that gravel mole drain is a suitable alternative to traditional mole drain. Considering the limited studies in the field of mole drainage, the purpose of this study is to evaluate the performance of low-cost mole drainage for draining excess water from paddy fields and its environmental effects. Therefore, the effect of traditional mole and gravel mole drain on drainage water quality and control of the water table of paddy fields in the mid and end of rice season was investigated.

The experiment was conducted in the agricultural year of 2022-2023 in the research farm of the Faculty of Agricultural Sciences, University of Guilan (IRAN). The split-plot experiment was implemented in a randomized complete block design in three replications under the main drainage treatment on two levels: (1) Traditional mole drain (without gravel) and (2) Gravel mole drain and the sub-treatment of irrigation method in two levels: (1) Flood irrigation and (2) Alternative irrigation. In the stages of tillering and harvesting, mid and end season drainage were done respectively. During the drainage period, the water table was measured with a piezometer. By sampling the drainage water, its quality parameters including acidity, electrical conductivity, nitrate, nitrite, phosphate, sulfate, chloride, total suspended and dissolved solids, sodium, calcium, magnesium, and ammonium were measured. The results of the investigated treatments were statistically analyzed using SAS software.

With the start of mid season drainage, after one day, the water table reached the middle of the soil profile and more than half of the root development depth was in anaerobic conditions. Five days after the drainage in the traditional mole drain, the depth of root development was in aerobic conditions. The highest value in average acidity and sodium adsorption ratio was 6.99 and 4.65 meq/l respectively in mid season in gravel mole drain and flood irrigation. The highest concentration of ammonium and nitrate in mid season drainage was 0.20 and 0.21 mg/l, respectively, and the highest average electrical conductivity and total dissolved solids at the end season were 3845 µS/cm and 2475 mg/l, respectively, in traditional mole drain and flood irrigation. In mid and end season drainage, the amount of total suspended solids in the mole drain with gravel was 60% and 88% higher than the traditional mole drain, respectively. The highest concentration of nitrite was obtained in the gravel mole drain and flood irrigation with a value of 6.75 mg/l during mid season drainage. The average concentration of phosphate and sulfate in gravel mole drain compared to the traditional mole in mid and end season decreased by 25 and 30%, respectively, and sulfate by 3 and 5.5%. Also, the average concentration of chloride in the gravel mole drain was lower than the traditional one.

The comparison of results indicated that the average amounts of electrical conductivity, total dissolved solids, sodium adsorption ratio, sodium, ammonium, phosphate, sulfate, and chloride of drainage water in mid and end season were lower in gravel mole drain than the traditional one. The results of statistical analysis showed that the treatment of drainage, irrigation, and time at the level of one and five percent were effective on most of the parameters, while the values of electrical conductivity, total dissolved solids, and nitrite of the drainage water showed that their difference was not significant. The traditional mole drain was more successful in controlling the water table. A comparison of the quality parameters of drainage water with the standard of the Iranian Environmental Protection Organization for the discharge of drainage water into surface waters showed that most of the parameters, except for ammonium and total suspended solids, were within the permissible limits.