نشریه تحقیقات مهندسی سازه های آبیاری و زهکشی
سال بیست و سوم شماره 87 (تابستان 1401)

Most regions of Iran are considered as arid and semi-arid regions. Water management in the agricultural sector is very important as the largest consumer of water resources in the country. In order to better plan and manage water resources in the agricultural sector, it is necessary to have sufficient information about the amount of water used in different products. Given the importance of its lemon product in the country, and conducting little research on this issue, determining the applied water for lemon orchards in the country can be useful for planning and macro decisions in the country. A review of literature shows that a lot of information has been collected in the world about the required water and the effect of different irrigation methods on citrus fruit yield. However, little research has been done on irrigating lemon trees under the management of gardeners. In Iran, little research has been done on the management of lemon irrigation. Therefore, in this study, the volume of applied water and water productivity of lemon trees in the country have been measured and evaluated.

In this field study, irrigation water volume and lemon yield in over 210 selected orchards in Fars, Hormozgan, Kohgiluyeh, Boyer-Ahmad and South Kerman provinces were measured directly. Fruit yield was obtained in three consecutive years and their mean was used in the analysis. Analysis of variance was used to investigate the possible differences in yield, irrigation water volume and water productivity in lemon production. After determining the inflow of water to the garden by carefully monitoring the garden irrigation program and measuring the area under cultivation, the volume of irrigation water applied by lemon trees in each garden was measured. Multiplying the flow rate during the total irrigation period during the season, the amount of irrigation water volume was obtained. In each of the gardens, items such as soil texture of the gardens, electrical conductivity of soil and irrigation water, etc. were also measured. The amount of evapotranspiration of the lemon tree in each region was calculated using meteorological data of the station closest to the project implementation area in the last 10 years and the year of the research using the Penman-Montieth method. The results were compared with the calculated net required irrigation water and the values presented in the National Water Document (NETWAT).

The results showed that the differences in yield, applied water volume, and indicators related to water productivity were significant in the mentioned provinces. The weighted average yield of lemon was 21.7 tons per hectare. The weighted average volume of irrigation water and total applied water were 11938 and 12993 cubic meters per hectare, respectively. The weighted average irrigation water productivity was estimated to be 1.94 kg/m3. Weighted average water+long-term effective rainfall productivity was 1.59, kg/m3. Weighted average of water and current year effective rainfall productivity were 1.75 kg/m3, respectively. The proportion of irrigation water volume of lemon orchards with gross water requirement in selected provinces was similar. In general, the average difference between the depth of irrigation water and annual and long-term gross water requirement in the country was -17 and -1 percent, respectively. In the orchards under drip irrigation system compared to surface irrigation, fruit yield and water productivity increased 43 and 89 percent, while irrigation water volume decreased about 20 percent. Salinity of water and soil, age of trees, literacy level of gardeners, climate, soil texture were some of the factors that affected yield, water productivity and volume of irrigation water.

Accurate determination of plant required water and volumetric water delivery can be very effective in reducing irrigation water and increasing water productivity. In addition to these two factors, adhering to irrigation scheduling in lemon orchards can produce the maximum yield per allotted amount of water. In creating or renovating of lemon orchards, cultivars should be planted that are resistant to cold and salinity and have the ability to export, while increasing the area under cultivation in proportion to water resources.

Pressurized irrigation systems are efficient tools for improving agricultural water productivity. Although increasing irrigation efficiency leads to saving water and increasing water efficiency, the implementation and usage of pressurized irrigation systems require energy supply and related tools and equipment, followed by greenhouse gas emissions. In this regard, one of the factors in the degradation of the environment is the phenomenon of global warming due to carbon dioxide emissions. In the present study, drip irrigation systems implemented in Qazvin province during 2010-2020 were randomly selected and evaluated for energy flow and greenhouse gas emissions. In this research, 17 drip irrigation systems, including pistachio, apple, peach, and nectarine crops, were randomly selected and studied in terms of energy flow and emissions of greenhouse gases. According to the energy equivalent coefficients and carbon dioxide emissions coefficient, the total input energy and carbon dioxide emissions for the drip irrigation systems were calculated. The country's agricultural authorities have considered and invested in the development and implementation of pressurized irrigation systems as one of the methods for proper use of water. Due to the phenomenon of global warming, the primary source of which is greenhouse gas emissions, any activity in the production of equipment, energy, and mechanization of irrigation systems leads to the production of greenhouse gases, which in turn increases the air temperature and crop water requirements and climate change. Given the phenomenon of global warming, the main source of which is the production of greenhouse gases, any activity in the direction of the production of equipment, energy, and mechanization of irrigation systems leads to the production of greenhouse gases, which in turn increase the temperature and change the need for water and climate change.

In this research, after collecting data on drip irrigation systems at different stages of equipment supply, we used drilling machines, welding equipment, and manpower based on the equivalent energy extracted from the sources for each of the stages of equivalent energy in terms of Megajoules. The process of implementation and operation of the irrigation system was calculated, and then we used greenhouse gas emission coefficients for three important greenhouse gases: carbon dioxide, nitrogen oxide, and methane, and considered the global warming potential of each gas using the relation "Greenhouse effect =" ∑_"i" ▒"m" _"i" "×" 〖"GWP" 〗_"i" that "i" is The amount of carbon dioxide equivalent to the emitted from the installation and operation of the drip system.

The results showed that the total annual energy consumption and carbon dioxide greenhouse gas emissions in the evaluated irrigation systems averaged 36,2022.68 MJ per hectare and 1974.07 Kg/ha, respectively. The results showed that the highest share contribution of energy consumption and carbon dioxide emissions with 85.27% and 86.15%, respectively, are related to the operation stage of the pumping station system. Besides, the production of system equipment and its transportation to the project site accounted for 12.83% of energy consumption and 10.93% of carbon dioxide emission. The results of energy flow calculations and carbon dioxide emissions using equivalent energy coefficients, global warming potential, and greenhouse gas emissions coefficient showed that the average total energy consumption and greenhouse gas emissions, due to equipment supply, system installation, and the operation of the pumping station, are 534,035 GJ and 29.611 tons of carbon dioxide equivalent per hectare in the period of fifteen years of the economic and useful life of a drip irrigation system. If the irrigation systems are evaluated from an environmental point of view, air pollutants emissions can be considered an influential factor. This issue has been neglected in the country concerning systems evaluation.

The findings of this study show that the amount of energy consumed and carbon dioxide emissions in different stages of drip irrigation systems are very different from each other and the energy consumed in the pumping stage to provide the required working pressure has the largest share. Factors affecting pump power It seems that by applying water consumption management, selecting pumps with higher efficiency, and avoiding imposing additional load on the network, energy consumption in the pumping network can be reduced. On the other hand, due to the efficiency of electricity production in power plants in Iran and its efficiency of transmission and distribution, if the mentioned efficiencies are improved, the equivalent of energy consumption due to electricity consumption in the pumping stage will be reduced. Due to the topographic conditions and geometric shape of farms and their distance from factories producing equipment, energy consumption and subsequent carbon dioxide emissions for different farms will not be a fixed number. The share of all practical steps except pumping energy consumption will be reduced annually.

The side weirs are widely used in sewage networks to aerate streams, irrigation and drainage networks to control water levels for dewatering, rivers for coastal management, and flood management of dams. One of the newest types of weirs researchers have considered in recent years is the piano key weir. Piano key weirs have a higher efficiency than other weirs due to their special geometry, especially the presence of upstream and downstream overhangs, as well as inlet and outlet keys. The use of piano key weirs as side weirs has received less attention from researchers, and because these weirs show better performance in discharge, more and more research is needed. The main objectives of the present study are first to investigate the effect of trapezoidal piano key weir height as one of the geometric parameters affecting the discharge coefficient and second to investigate the water surface profiles at the upstream and downstream ends and within the location of the weir in the main channel. In parallel with the main objectives, the study of the Dimarchi hypothesis in estimating the discharge coefficient and the study of discharge efficiency of the trapezoidal piano key is also followed. In this regard, four models of trapezoidal piano key overflow with a height of 10, 15, 20, and 25 cm (TPKSWp10, TPKSWp15, TPKSWp20, and TPKSWp25), a labyrinth trapezoidal weir model with a height of 20 cm (TNRSW) and also rectangular sharp crest weir as The control model (Lisw) was tested under the subcritical flow with the Froude numbers in the range of 0.10 to 0.74. De Marchi, in 1934, assuming that the specific energy was constant at the upstream and downstream ends, calculated an equation for estimating the discharge coefficient of the side weirs that were related to the hydraulic parameters of the flow at both the upstream and downstream ends of the weir. In this study, the main hypothesis for estimating the piano key weirs' discharge coefficient is the Di Marchi hypothesis. The results show that, firstly, due to the specific energy changes at the upstream and downstream ends of the trapezoidal piano key models (ΔE/E1), especially in the TPKSWp10 and TPKSWp15 models, and the occurrence of hydraulic jump that affects the essence of the flow, use the Dimarchi hypothesis And comparing the discharge coefficients of trapezoidal piano key side weirs should be done with caution. The discharge capacity of the side weirs is defined as the ratio of flow spill from them to the inflow to the main channel. The results of this study show that the discharge capacity of trapezoidal piano key weirs increases with increasing height due to the more uniform water surface profile, reducing the interference of the outlet blades of the inlet and side crest and reducing the vortex in the inlet openings and faster exiting than the outlet keys. In the TPKSWp25 model, the discharge capacity is 2.60 times higher than the Lisw, and for the TPKSWp20, TPKSWp15, and TNRSW models, it is 1.92, 1.59, and 1.38 times higher than the Lisw, respectively. In the present study, two types of diagrams have been used to investigate the effect of the height of trapezoidal piano weirs on the water surface profile due to the complexity of the flow pattern and the simultaneous effect of geometric and hydraulic parameters of the weir and better analysis of these parameters on the water surface profile Also, the water level decreases in the longitudinal section Z*=1 (on the crest weirs) and at the upstream end of the weir due to the increase in the longitudinal acceleration of the flow and being affected by the suction of the flow by the weir in this range in all experimental models. This water level reduction for TPKSWp15,20,25 models and TNRSW models is almost the same and equal to 25%.

In today's agriculture, the use of different chemical and organic fertilizers is inevitable via to adding the amount of production. However, in some cases, application of fertilizers could result to introduce of some pollutants such as nitrates into the environment and water and soil resources. In such a condition, the application of urea coated fertilizers or slow released may cause less pollution. In this research, the amount of nitrate transport in soil profile was investigated due to the application of some common chemical and organic fertilizers in comparison with slow release urea (sulfur coated) fertilizer (SCU). For this purpose, 15 cylindrical columns of soil and water, with a height of 150 cm and a diameter of 10 cm were designed, constructed and used. The columns were filled up to a height of 120 cm with a sandy loam soil. Drainages were installed at different depths of the columns. The amount of applied fertilizers was calculated and applied based on the amount of nitrogen required for the tomato plant. In this research, a statistical factorial with completely randomized design was used to study the factors including: type of fertilizer (no fertilizer as control treatment, urea, ammonium nitrate, coated urea and poultry manure); sampling depth of drainage water (30, 60 , 90 and 120 cm from the soil surface); irrigation rotation (5 times) and sampling intervals in each irrigation (5 times based on specific volumes of drainage water discharge of a complete purvolum of soil) with three replications. The results of the analysis of variance indicated that the effects of the type of applied fertilizer, irrigation rotation and sampling time on the amount of nitrate measured in the effluent samples (nitrate leaching) were statistically significant at the 1% level. But nitrate concentration in the samples prepared from the different depths did not show significant changes. Investigating the mean values of nitrates in drainage water showed that nitrate transfer to soil depth was the highest in ammonium nitrate application (with a mean of 51.67 mg/l) and was the lowest in control treatment (with a mean of 38.39 mg/l). Also, urea fertilizers (with a mean of 48.16 mg/l), poultry (with a mean of 40.70 mg/l) and coated urea (with a mean of 39.88 mg/l) were placed in between them, respectively, and the differences were statistically significant at one percent level. In general, application of coated urea (SCU) fertilizer could have a clear effect on reducing nitrate leaching to soil depth, especially in the condition of this research and in comparison with other types of common fertilizers.In today's agriculture, the use of different chemical and organic fertilizers is inevitable via to adding the amount of production. However, in some cases, application of fertilizers could result to introduce of some pollutants such as nitrates into the environment and water and soil resources. In such a condition, the application of urea coated fertilizers or slow released may cause less pollution. In this research, the amount of nitrate transport in soil profile was investigated due to the application of some common chemical and organic fertilizers in comparison with slow release urea (sulfur coated) fertilizer (SCU). For this purpose, 15 cylindrical columns of soil and water, with a height of 150 cm and a diameter of 10 cm were designed, constructed and used. The columns were filled up to a height of 120 cm with a sandy loam soil. Drainages were installed at different depths of the columns. The amount of applied fertilizers was calculated and applied based on the amount of nitrogen required for the tomato plant. In this research, a statistical factorial with completely randomized design was used to study the factors including: type of fertilizer (no fertilizer as control treatment, urea, ammonium nitrate, coated urea and poultry manure); sampling depth of drainage water (30, 60 , 90 and 120 cm from the soil surface); irrigation rotation (5 times) and sampling intervals in each irrigation (5 times based on specific volumes of drainage water discharge of a complete purvolum of soil) with three replications. The results of the analysis of variance indicated that the effects of the type of applied fertilizer, irrigation rotation and sampling time on the amount of nitrate measured in the effluent samples (nitrate leaching) were statistically significant at the 1% level. But nitrate concentration in the samples prepared from the different depths did not show significant changes. Investigating the mean values of nitrates in drainage water showed that nitrate transfer to soil depth was the highest in ammonium nitrate application (with a mean of 51.67 mg/l) and was the lowest in control treatment (with a mean of 38.39 mg/l). Also, urea fertilizers (with a mean of 48.16 mg/l),

Manning's equation is the most popular equation to determine the flow resistance in the steady and uniform flows. The amount of flow resistance in alluvial rivers depends on the type of bed form and its geometrical characteristics. In ripple and dune bed forms, which are formed at Froude numbers less than one (lower flow regime), the flow separation from their crest is the main factor of flow resistance (Shafai Bajestan, 2008; Julien, 2010). The effect of bed form on flow resistance have been studied by few researchers such as: Talebbeydokhti et al. (2006), Omid et al. (2010), Nasiri Dehsorkhi et al. (2011), Chegini and Pender (2012), Kabiri et al. (2014), Samadi-Boroujeni et al. (2014), Kwoll et al. (2016), and Heydari (2020). However, no research has been observed regarding the effect of the dune bed form height on Manning's roughness coefficient. Therefore, the main goal of the present study is to investigate the effect of dunes with different height of 1, 2, 3, and 4 cm on Manning's roughness coefficient in a straight flume under different discharges and bed slopes.

The experiments were performed in a straight flume of 12 m in length and 0.30 m wide (Figure 1). In this study, different flow discharge of 10, 15, 20, 25, and 30 l/s and different bed slopes of 0.00001, 0.0001, 0.0005, 0.001, and 0.0015 were tested. Each dune was made in an asymmetric triangular shape with cement-sand mortar. The dune's height was equal to 1, 2, 3, and 4 cm, and the its length was selected as 25 cm. After each dune was built, the sediment with average size (d50) of 0.45 mm was glued to its surface. The total number of experiments in the present study was 100. Dune bed form dimensions were in lower flow regime. All the experiments were carried out at lower flow regime with, the Froude number values ranged from 0.44 to 0.7.

Figure 4 shows the variation of the Manning's roughness coefficient against relative submergence (y/Δ) for dunes with a height of 1 cm. This figure shows that, with increasing relative submergence and bed slope, Manning's roughness coefficient decreased.Figure 5 shows the changes in the Manning's roughness coefficient against Froude number for dunes with different heights (slope of 0.0001). It can be seen that as the Froude number increased, the Manning's roughness coefficient decreased.
Figure 7 illustrates the effect of Δ/λ on the Manning's roughness coefficient. This figure shows that the Manning's roughness coefficient increased with increasing Δ/λ. Calculations showed that the Manning's roughness coefficient in dunes with Δ/λ = 0.08, 0.12, and 0.16 was, on average, 17, 30, and 55% more than dune with Δ/λ = 0.04, respectively.Figure 8 shows the effect of the dune bed form height on the Manning's roughness coefficient. By increasing bed form height, Manning's roughness coefficient increased. Calculations showed that the Manning's roughness coefficient in dunes with height of 2, 3, and 4 cm was, on average, 16, 31, and 55% more than dune with a height of 1 cm, respectively.

The results of this study shows that with increasing the Froude number and the relative submergence (y/Δ), the flow resistance or Manning's roughness coefficient decreases. Moreover, the increase in the Δ/λ and the bed form height leads to an increase in Manning's roughness coefficient. Calculations showed that the Manning's roughness coefficient in dunes with height of 2, 3, and 4 cm was, on average, 16, 31, and 55% more than dune with a height of 1 cm, respectively. In addition, the form Manning's roughness coefficient (nb'') for dunes with heights of 1, 2, 3, and 4 cm is, on average, 30.7, 40.2, 46. 5, and 53.4% of the total Manning's roughness coefficient (nb), respectively.

In recent years, pollution of surface water resources, especially rivers, has posed an environmental challenge. Pollution from municipal or industrial wastewater and waste disposal into rivers are important problems for human societies to protect the environment. Knowing the level of river water pollution as one of the sources of human water needs is essential and therefore modeling the quality of river water is very important. Hydraulic structures in rivers are one of the ways to control pollution in open-channel flows. Check dams are one of the types of these structures that due to the porosity of their environment can play a controlling role in the transport of contamination by increasing hyporheic exchanges as well as transient storage of contamination in their porous media. Transient storage model (TSM) is one of the methods of pollution transport analysis, especially in rivers with high hyporheic exchanges. The efficiency of the (TSM) is in the correct estimation of the four parameters of the model (Dx, As, A and α). Previous studies have not investigated the effect of hyporheic exchanges due to gabion check dams on the four parameters of thel (TSM). In this study, the effect of gabion check dams on pollution transport and the four parameters of the (TSM) with OTIS numerical model were investigated.

Experiments of tracer material (NaCl) were performed in a flume with a length of 12 m, a width of 0.5 m and a height of 0.7 m in four flow discharges (2.5, 5 and 7.5 lit/s). An ultrasonic flow meter was used to measure the flow discharge in all experiments. Materials with medium diameter (D50) of 11.85 mm and porosity (n) of 0.28 were used to create a sedimentary bed with a length of 12 m and a thickness of 12 cm at the bottom of the flume. In this study, two types of gabion check dams with medium diameter (dg) of 11 mm (fine-grained) and 19 mm (coarse-grained) were used. In each experiment (except for the control experiment), 1 to 3 check dams were used at intervals of 2.5, 5 and 7.5 meters from the beginning of the flume, respectively. In this study, check dams with lengths of 0.75 and 0.35 m, widths of 0.5 and heights of 0.4 m were used. The length of the flume was divided into four equal reaches (L1, L2, L3 and L4). Two sensors were placed to measure the electrical conductivity (EC) of water at the end of each reach to measure the amount of contamination. Micro-propeller and ultrasonic depth-gauge were used to measure the velocity (V) and depth (h) of water flow in each reach. The laboratory results in L4 reach were simulated by the OTIS-P numerical model and the four parameters of the (TSM) were estimated.

The results showed that gabion check dams increased the transient storage of solute in the porous media of such dams, thus reducing the peak contamination concentration (Cmax) in the main flow area. On the other hand, check dams in the flow path will act as a sedimentary bed-form, which increases the hyporheic exchanges between the main flow area and the porous media of such dams. Increasing hyporheic exchanges into the porous media of the dams will also reduce the (Cmax) in the main flow area. Increasing hyporheic exchanges into the porous media of the dams also reduces the contamination concentration (Cmax) in the main flow area. Reducing the (Cmax) in the main flow area will also increase the longitudinal dispersion coefficient (Dx).Comparison between the storage zone exchange coefficients (α) estimated by the OTIS-P numerical model showed that these coefficients decreased with decreasing the length of check dams (a). Reducing the length of check dams (a) will reduce the space of the porous media in the flow path. Therefore, the solute will leave these storage zones with a shorter residence time, so the storage zone exchange coefficient (α) decreases with decreasing the length of check dams (a).Gabion check dams made of fine-grained materials reduce the exchange discharge between the check dams and the main flow area. The use of fine-grained materials reduces the rate of contamination transfer to the downstream reaches, so the (Cmax) in the downstream reaches will decrease, so the(Dx) will increase in the fourth interval (L4).

 Increasing the number of gabion dams (N) from one dam to three dams caused an approximately 1.43 to 1.71 times the value the (Dx). Increasing the length of gabion dams (a) from 35 cm to 75 cm caused approximately 1.43 to 2.49 times the value of the(Dx).Increasing the length of gabion dams (a) from 35 cm to 75 cm caused an approximately 1.10 to 4.43 times the value of the (α). The use of fine-grained materials in gabion dams increased the (α).

Melon, with the scientific name Cucumis melon L, is an annual plant belonging to the Cucurbitaceae family (Mas, 1986). Melon is one of the most important products, which is rich in absorbable vitamins and minerals needed by the human body. According to the statistics of the World Food Organization (FAO), Iran with the production of 1731 thousand tons of melons in 2018, was the third producer after China (with the production of 12727 thousand tons) and Turkey (with the production of 1754 thousand tons), and the countries of India, Kazakhstan and America are ranked 4th to 6th in the world with 1231, 894 and 872 thousand tons respectively. Improving water productivity in crop production is necessary due to limited water resources in Iran. According to the surveys conducted on the volume of irrigation water (water applied) or the water given by farmers to melon cultivation, there are no accurate and reliable statistics in the country, and no relatively accurate measurement or estimation has been done in the country. On the other, melon cultivation is important in Iran, so it is necessary to study the volume of applied water in production of this product. In iran, development of pressurized irrigation systems has been one of the main programs in developing agricultural sector in the past few decades. Assessing the effects of these systems can be important in increasing of water ues management, national policies and planning. In this article, based on the field data of the research, it is tried to explain the amount of water used and water productivity of melons in the country and the effect of irrigation management (traditional and modern) on the amount of water given to melons.

In order to determine the volume of water used, yield and water productivity of melon crop with the management of farmers in Khorasan Razavi, Fars, Khuzestan, Semnan and Sistan and Baluchestan provinces in calendar year of 2020, 138 melon farms were selected. In these farms, the volume of applied water by farmers was measured. Water irrigation applied (water used) 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. In this study, the method of analysis of variance is used to investigate the possible differences in yield, applied water and water productivity in melon production. Data adequacy was assessed by using the method provided by Sarmad et al. (2001). Then, the effect of drip irrigation method on applied water, application efficiency and physical water productivity was investigated in the study areas.

The results showed that the differences in yield, applied water and water productivity indices in melon production were significant in selected provinces (P ≤ 0.01). The average weighted of yield, applied water and water productivity in Iran were 24962 kg / ha, 7117 m3/ha and 3.4 kg / m3, respectively. The total water for irrigating melon in Iran was estimated at 570.8 million cubic meters. The average yield of melon in furrow and tape irrigation was 20,954 and 24,500 (kg/ha), respectively. In other words, the average yield in tape irrigation method was 14.5% more than furrow irrigation method.The average volume of water in furrow and tape irrigation methods was 7940 and 6073 (m3/ha), respectively. The average volume of irrigation water in the tape irrigation method showed a decrease of 23.5% compared to the volume of irrigation water in the furrow method. The average water productivity in furrow and tape irrigation methods was 3 and 4.3 kg/m3 per hectare, respectively. The average water productivity in tape irrigation method showed an increase of 30% compared to the average of furrow irrigation.

The results of this research showed that tape irrigation method can improve yield, water consumption management and water productivity for melon. Also, the results of this study provide useful information on applied irrigation water management indicators in melon production to managers and water decision makers within Iran. The results of this research show that the use of drip irrigation systems (tape irrigation system) for melon cultivation in the country (and other row crops) can increase water productivity and reduce water consumption in the agricultural sector. However, the operation management of these systems in the country has a relatively long distance from the desired level