فصلنامه علوم و مهندسی آبیاری
سال چهل و چهارم شماره 4 (زمستان 1400)

Irrigation has greatly contributed to crop production in arid and semi-arid regions. In addition, agricultural production in irrigated lands is more sustainable than in rain feed lands, which has helped significantly stabilize food prices in the world (Hanjra et al., 2009; Rosegrant and Cline, 2003). Considering the role of irrigation and scarce water resources, the United Nations Development Program has predicted that the future of food supply for the world's growing population will be affected by the water crisis, not the crisis of arable land (Du Toit, 2011). Therefore water is a major player in increasing agricultural production (Hanjra and Qureshi, 2010). At the same time, competition for water between the agricultural, industrial and urban sectors is also increasing (Dubois, 2011). Under such circumstances, any method or technology that can increase the productivity of water consumption (product per unit volume of water) will contribute to the development of food security. Naturally, cheap and simple methods and technologies, especially among low-income farmers in developing countries, will become more common; deficit irrigation is one of them.Beans are an important source of protein, fiber, and nutrients and have for centuries played an important role in the human diet (Yonts et al., 2018). The bean is a water-consuming plant, its net water requirement in the Khorramabad Plain (Project Area) is about 5500 m3/ha, which is 2.5 times more than wheat and 2 times more than rapeseed (Zabihiafrous et al., 2018). Deficit irrigation of beans can be an effective solution to reduce the irrigation water consumption of this crop and increase its water productivity.

Hydraulic conductivity of soils is one of the most important parameters in designing soil structures, water, and environmental resources management. Hydraulic conductivity in the soil varies with the size of their particles. Several studies by different researchers on fine-grained soil hydraulic conductivity and coarse-grained soils are done. In some studies, the methods and materials used to reduce soil hydraulic conductivity. On the other hand, nanoclays are nanoparticles of layered mineral silicates. Depending on chemical composition and nanoparticle morphology, nano clays are organized into several classes such as montmorillonite, bentonite, kaolinite, hectorite, and halloysite(Majeed and Taha, 2013). Organically modified nanoclays (organoclays) are an attractive class of hybrid organic-inorganic nanomaterials with potential uses in polymer nanocomposites, as rheological modifiers, gas absorbents, and drug delivery carriers(Abbasi et al, 2016).Plate-like montmorillonite is the most common nanoclay used in materials applications. Montmorillonite consists of ~ 1 nm thick aluminosilicate layers surface-substituted with metal cations and stacked in ~ 10 µm-sized multilayer stacks. Depending on the surface modification of the clay layers, montmorillonite can be dispersed in a polymer matrix to form a polymer-clay nanocomposite. Within the nanocomposite individual, nm-thick clay layers become fully separated to form plate-like nanoparticles with a very high (nm × µm) aspect ratio.In this study, the effect of different amounts of montmorillonite nano clay (0.25, 0.5, 0.75, and 1%) on the hydraulic conductivity in three different densities (85, 90, and 95%) of sandy and clay soils have been investigated experimentally.

Drought and water shortage in Iran is a climatic fact and due to the growing need for water in different sectors, this problem will become more acute in the coming years. Therefore, managing water consumption and applying advanced techniques in the agricultural sector as the largest consumer of water in the country, can be very helpful. One of the most effective strategies to improve water productivity in agricultural sector is to use hydrogel polymers to improve soil texture, increase soil water retention, reduce erosion and increase germination (Nirmala and Guvvali, 2019). However, in general, due to differences in the synthesis and chemical structure of polymers, the water uptake and storage capacity of these hydrophilic polymers are different, and hence their effect on changes in soil moisture and storage capacity will be very different (Yu et al ., 2017). The aim of this study was to investigate the effect of different levels of Aquasource hydrogel on yield, yield components and water productivity of peppermint (Mentha piperita) at different irrigation intervals.

This study uses the blocking of a two-cycle circular piano key weir (C.P.K) that benefits from a considerable vortex breaking capability compared to other kinds. To do so, the impact of floating objects on the blocking amount of this weir is investigated using 13 pieces of wood with slenderness coefficients (Ld/Dd) of 15, 20, and 25. Three slopes of 1:0.5, 1:1, and 1:1.5 (vertical: horizontal) were chosen to study the impact of the bottom slope of the input and output keys on the blocking probability. To reach the mentioned slopes, the shape of the weir was designed and built with three P/D relative heights of 0.5, 1, and 1.5. The experiments showed that the weir had more blocking probability with a relative height of 1.5 than the other models with fewer key slopes. In addition, individual experiments revealed that the diameter of floating objects was more influential on blocking probability than the length of the objects and the amount of upstream watery load. It can generally be concluded that increasing the diameter and length of the floating objects are directly and indirectly correlated with the blocking amount and the amount of watery load on the weir crown, respectively. Comparing the obtained results with the bell-mouth spillway reveals that the C.P.K weir benefits from more sediment trapping capability.

Monitoring and conservation of the wetlands are very important due to their role in eco-system protection and providing the socio-economic needs of the local community. Sarp and Ozcelik (2017); Nandi et. al. (2018); Ali et. al. (2019) used NDWI, MNDWI and AWEI indices to monitor waterbodies changes based on Landsat (ETM+, OLI) dataset. In this study, these indices were applied to monitor area changes of Hor-alazim and Shadegan wetlands in Khuzestan province that were selected as case study areas for period 2000-2018. Wetlans area changes were evaluated for three months, include April, September, and January in any year that represent inflow changes. Mann-Kendall statistics was also used to study the changes in a wetlands area. The  MNDWI index in comparison to NDWI and AWEI has better performance and higher accuracy. The results of Man-Kendall statistics showed that wetlands area changes have no significance relation in 95% confident level. Also, the correlation between temperature and wetland area changes showed that on average, the wetlands temperature changes by ±0.4 C for per 1000-hectare area change.

Deficit irrigation is a suitable method for obtaining the economic and acceptable yield with the minimum amount of water (Zegbe et al., 2004). Although the yield in unit area is decreased in this irrigation method, the amount of consumption water, water harvesting, delivery and distribution costs of water decreased, which results in more benefit (Yazar et al., 2009).Partial root drying (PRD) is the modified method of deficit irrigation which some part of plant roots is irrigated and another part of them are placed in dry soil. For the first time, the concept of PRD was applied by Grimes et al. (1968) in the United States. In this method, water uptaking from the wet zoning of plant roots holds the water status in plant in a favorable condition (Davies et al., 2002), and the other part of roots placed in dry soil results in increasing abscisic acid hormone production.The most important growth indices which are used frequently in plants include leaf area index (LAI), crop growth rate (CGR) and relative growth rate (RGR) so that plant production dry matter can be investigated using these indices (Modarresi et al., 2004). Investigation of variations of growth indices of five maize hybrids under two different irrigation regimes indicated that interrelationship between leaf area index and grain yield was significant (Nori Azhar and Ehsanzadeh, 2007).Water scarcity is one of the most important factors that decrease the maize yield and yield reduction depending on corn cultivars and growth stages that are affected by water stresses. With regard to desirable features of leafy and commercial hybrids of maize and also different effect of stresses in different stages of vegetative and reproductive growth, the objective of this study was to investigate the effect of water stress and new deficit irrigation strategies on growth indices of two corn cultivars in Kashmar climate.

One of the most critical challenges of the twenty-first century is to resolve water crisis. This crisis is characterized by scarcity of water, the destruction of natural ecosystems, and food shortages. In spite of extensive efforts made to ensure food security, human societies still have trouble feeding their populace. This problem is most likely due to their inability to access healthy and safe water resources (Kijne, 2003). The solution to the water crisis can be expressed as better development and proper management of water resources systems. Various technical and managerial solutions should be taken such as upgrading and improving irrigation systems, introducing new irrigation methods, deficit irrigation, optimizing the cropping pattern, improving the efficiency of irrigation networks, etc. to improve water productivity in agriculture. The system dynamics methodology is a modeling and simulation technique and is specially designed for long-term, chronic, and dynamic management issues (Vlachos et al., 2007). Crop pattern scenarios, crop production, and agricultural pollution in a region in southern Turkey have been studied by Saysel et al. (2002) with a system dynamics approach. Also, the system dynamics approach was applied in the study of integrated water management at the catchment scale by Soltani and Alizadeh (2017). In this study, the systems dynamics approach, which is a suitable method for studying complex water systems, was applied in water productivity investigation in the Qazvin irrigation network.

Flood is one of the most common and dangerous natural disasters occurring worldwide (Samanta et al., 2018). Iran is ranked sixth in the world in terms of flooding (Khosroshahi and Saghafian, 2003) due to the disturbance of the hydrological balance of the country's watersheds, of which Abolabbas River Basin is no exception. In effect, due to the hydrological imbalance of the watershed, the river runoff cannot be transferred well (Tehrany et al., 2013). Given that each part of the basin has a certain potential in the production of runoffs and floods, once water overflows into the surrounding lands floods occur. It is thus necessary to prepare flood sensitivity maps and identify susceptible areas for flood prevention and management (Bout et al., 2018). This study was thus intended to prepare hazard maps for different parts of the watershed, and to prioritize the effective parameters in the occurrence of floods in the study area.

This study considered 11 important indicators including altitude, runoff curve number, slope, slope direction, rainfall, vegetation, drainage density, distance from waterway, land use, stream power index and topographic wetness index to determine the flood potential of Abolabbas River Basin with an area of 281.23 square kilometers. For the purpose of this study, the layers were scaled and the individual pixels were weighted and then prioritized using the TOPSIS technique (Rasooli et al., 2018).

Recorded daily weather data are used as climate input in a number of models that continuously simulate the natural resource systems (Yu, 2003). However, it is sometimes difficult to obtain the required data, and also to process them simply because they are lacking or unavailable. Weather generators have been accordingly developed to produce synthetic weather sequences capturing the essential features of observed weather data needed for running the models. In effect, weather generators are widely used in hydrological, ecological, and crop-yield modeling frameworks. CLIGEN (CLImate GENerator), which was first developed as a component of the Water Erosion Prediction Project (WEPP) (Nicks et al., 1995), is a stochastic weather generator that generates long sequences of daily precipitation (e.g., the pattern of each rainfall event including its duration, time to peak, and intensity), maximum and minimum daily temperature, dew point temperature, solar radiation, and wind speed and direction. CLIGEN has been currently used as a general weather generator beyond its initial intention in many locations around the world. This research was thus conducted to examine the efficiency of CLIGEN in generating the weather data in Sanganeh station in the northeast of Iran.

Sediment control is one of the issues of paramount importance in designing irrigation networks and water supply facilities. The most important methods of erosion and sedimentation management and control include basin management, sediment trap management in upstream, and sediment trap source management out of the river. Jafari et al. (2019) investigated the effect of submerged vanes and their dimensions on the bed load transport in the widened part of the river using a laboratory model. The results showed that by increasing the dimensions of submerged vanes, the speed of the bed load transport decreased, and as a result the performance of vanes improved. In a similar research strand, the present study evaluated the effect of obstacle installation and its size in the widened part of the river on the bed load transport using a laboratory model.

Using a dimensional analysis of the effective variables in the widened part of the river and installing obstacles, this study identified the influential parameters on the bed load transport. Some experiments were then carried out by simulating the widened conditions of the river in a laboratory canal. Then, a witness experiment was carried out in the widened part of the river without the presence of an obstacle. This was followed by 21 experiments in the widened parts of the river by installing an obstacle. Linear obstacle arrangement in the basin was then performed in 5 rows and 3 columns and it was considered constant for all experiments. Moreover, the discharge rate and depth, according to the initial experiments and the amount and manner of sediment movement, were constant for all experiments and equal to 10 liters per second and 0.16 meters, respectively. In order to examine the effect of the obstacle size, 15 obstacles with 0.04 meter height (hb), different width (Wb) and length (Lb) with 0/02, 0/03, 0/04 and 0.05 meters were installed and tested. At the end of the performance, the main section (i.e., the widened part) of the bed load control was examined quantitatively and qualitatively. To examine the quantitative performance of the main section, equation (1) was used. Rs = (1) In (1), Rs is the reduction in the distance of sediment flow in the widened part with an obstacle relative to the state without an obstacle (i.e., witness test), xe is the progression of sediment flow in the widened section without an obstacle, (xe- xb) is decreasing the progression of the sediment flow in the widened part with an obstacle relative to the widened conditions without an obstacle.