فصلنامه علوم و مهندسی آبیاری
سال چهل و پنجم شماره 4 (زمستان 1401)

Obstacle usually blocks the current and it has been found by other researchers an obstacle with a height more than two times of body height of flow is necessary to fully block the density current. The construction of an obstacle with this elevation creates problems in terms of performance and sustainability as well as the accumulation of sediments behind it.Rottman et al. (1985) solved the analytical solution of the two-phase current in a horizontal slope with an obstacle in the steady and unsteady flow and concluded that if the height of the obstacle is twice the body height of the density current so the density current is completely blocked. Prinos (1999) conducted studies on the effect of the shape of the obstacle on the current control. In his experiments, he used two semi-circular and triangular obstacles with the same height and concluded that the shape does not have a significant effect on the control of high current. Also, in the range of densimetric Froude number, 0.7 < Frd < 0.8 if the height of the obstacle is twice the height of the body of the density current, the current will be fully restrained. As it has been stated, for a complete block of density current, based on the results of previous investigators, the height of the obstacle should be at least twice the height of the body.The purpose of this study is to use successive obstacles with lower height, with greater sustainability and lower cost, in controlling density current. For this purpose, in different conditions, in terms of slope and concentration, three rows of obstacles with different heights and also different distances were used to control sedimentary and salty density current.

One common method for Blank River protection and restoration is use of Spur dikes. Spur dikes either in the forms of group or single, depending on their permeability is classified an permeable and impermeable. Spur dikes restore flow pattern and prevent erosion of river banks. This leads to stability and immovability of river. However, they have some disadvantages; on installation they require drying river and erosion around their structure causes destruction (Anonymous, 2002, 2003) and (Anonymous, 2010). Due to the mentioned disadvantages use of spur dikes will be halted and use of vane, which has a higher environmental compatibility, is suggested. This study aims to introduce “composite structure”; a new structure with a combination of a Spur dike with different permeability and a single vane. The main aim of this study is to increase the amount of sediment transported behind the structure by water flow produced by the vane in the combination structure.

Climate change caused by global warming has altered temporal-spatial distribution as well as rate and form of precipitation, the magnitude of floods, annual precipitation ​​in rivers, seasonal variation of probable maximum precipitation and flood, water quality, evaporation rate, concentrations of nutrients in aquifers, etc. the Atmosphere-Ocean Coupled General Circulation Model (AOGCM) is currently the most reliable tool to study the effects of climate change on different systems. This model simulates climate parameters. Estimation of probable maximum precipitation (PMP) is an important and practical research method that not only identifies behavior of extreme rainfall in climatology, but also helps hydrologists to design various large water control structures, especially dams. Climate change affects PMP in the coming periods. Consequently, PMP estimates will be modified by hydrologists.

Surface and groundwater dynamically interact at different spatial or temporal scales within a plain. Accurate estimation of water balance components is an important simulation of such interactions. Despite the rapid expansion of numerical models over the past two decades, there is still room for improvement for comprehensive and integrated assessment as well as management of surface and groundwater resources. In particular, the use of coupled surface and groundwater models is important to connect both surface and groundwater, and for proper representation of the water balance in the unsaturated root zone. The results of various studies suggest that the combination of SWAT and MODFLOW models can satisfactorily simulate the interaction between surface and groundwater at different spatial and temporal dimensions (Sophocleous and Perkins, 2000; Sun and Cornish, 2005; Bejranonda et al., 2007). Indeed, if both models are used simultaneously, not only the limitations of the two individual models can be improved, but also the temporal-spatial properties of the target area can be adequately reflected (Kim et al., 2008; Park and Bailey, 2017; Wei et al., 2018). Specifically in the Urmia Lake Basin, which has been severely affected by indiscriminate exploitation of water resources, these models can be used to maximize the supply of Urmia Lake based on the pattern of supplying irrigation needs from integrated water sources. This requires the interaction of surface and groundwater resources in different locations of plains and aquifers to be simulated and predicted based on different shares of agricultural water supply from integrated water sources.The main purpose of this study was to evaluate the interaction between ground and surface water in Mahabad plain using the coupled SWAT-MODFLOW-NWT model as a comprehensive and integrated model. The main challenge in this study is the interaction and monitoring of water table adjacent to the surface water bodies.

Due to drought crisis in recent years, the use of alternative cropping methods that saves water without any decrease in yield is increasing. Regulated deficit irrigation is a method of irrigation in which, by supplying part of the maximum crop requirement at specified times, water management is addressed and therefore the root zone is in a dry area most of the time. Using this method will partially stop the growth of the plant and usually decrease yield (Jovanovic et al., 2010). Root Partial Drying (PRD) is a modified form of the deficit, which includes watering one section of the root zone in each irrigation and dry up another side, so the moisture of this section before next irrigation largely come down (Ahmadi et al., 2010). In the root drying method, the roots of the plant simultaneously with soil drying with the production of Abscisic Acid, prevent leaf expansion and reduce stomatal conductance. Simultaneously with this process, the root in the wet part with adequate water uptake puts the plant in proper moisture (Yousri Ibrahim Atta, 2008). Abscisic acid is a plant hormone whose production is increased by root in dry soils and transported by water flow into the stem. (liu et al., 2008). On the other hand, The quality of production is as important in all crops and especially in rice production in Iran. (Salehifar  et al., 2009) In order to evaluate some of the physical and qualitative properties of rice grain and the amount of nitrogen uptake in rice (Hashemi variety) under different irrigation levels and comparing it with continuous waterlogging, an experiment was conducted during two years of cultivation of 2015 and 2016.

The increasing population and development of agricultural and industrial activities have put excessive pressure on freshwater resources. As a result, wastewater treatment has received growing attention in recent years. It seems more necessary in arid and semi-arid regions such as Iran, where we face climate change and a lack of rainfall (Mohammadi Moghadam et al., 2015; Nikmanesh et al., 2018). However, wastewater is one of the most critical environmental pollutants. If the microbial quality of the effluent and its hygienic aspects are not taken into account, its reuse poses a severe risk to human health and the environment (Abedi-Koupai et al., 2021). Therefore, the primary purpose of disinfection effluent from municipal wastewater treatment plants is to reduce the concentration of water-borne pathogens to less than the amount of infectious. Disinfection is done by physical and chemical methods. In most parts of the world, chlorine is the premier option for disinfecting effluents. That said, the adverse effects of chlorine effluent disinfection on humans and the environment have led to the possibility of using phytoremediation to improve the biological properties of water (Keddy, 2010). The Vetiver (VS) system for wastewater treatment is an innovative phytoremediation technology that has fantastic potential. This plant can grow in saline environments (Sanicola et al., 2019). Moreover, it can significantly improve the water quality parameters (Abedi-Koupai et al., 2021). Therefore, this study aims to investigate the possibility of using Vetiver in urban wastewater hydroponically to evaluate its efficiency in removing and refining pathogens, especially gastrointestinal coliforms. Our purpose is to use the treated water in the agriculture sector for irrigation.

Hydrologists studying rivers must determine the relative importance of in-river processes to understand the fate of pollutants. Storage processes are one of the most of this. Currently, the most reliable method for determining the importance of storage processes in the solute transfer is to estimate the stream-storage exchange coefficient (α) and the cross-sectional area ratio (AS/A) in the transient storage model (TSM) with tracer experiment data (Wallis and Manson, 2019). Calibrating the parameters depends on the reciprocal coverage between parameter effects on BTCs and the model's sensitivity to each parameter (Zaramella et al., 2016). Previous studies have quantified the sensitivity of the TSM in inverse modeling (Kelleher et al., 2013; Wlostowski et al., 2013). Due to tracer test data for these studies, their results cannot provide a comprehensive picture of the model behavior. In this study, using Monte Carlo-based methods, an attempt has been made to investigate the effect of different pollutant transfer circumstances in the river by defining a framework with Peclet and Damkohler numbers and pollutant injection time series on storage parameters sensitivity.

The growing population and, consequently, the need to produce crops on the one hand and the limitation of water resources as an important factor in agricultural production have led to the intensification of the problem of dehydration in many parts of the world, including Iran. Therefore, a balance between water resource constraints and agricultural development is essential. In this regard, the International Water Management Organization (IMO) has estimated in its comprehensive assessment that water management in agriculture in rainforests could lead to a 75% increase in global food products (Di Dono, 2009). Therefore, agricultural development through the development of dry land areas can be considered as a logical solution in the context of the water crisis (Akhavan et al. 2013).

Maximum sprinkler flow rate, maximum irrigation interval, and leaching requirement are the primary factors in designing sprinkler irrigation systems, which are determined based on the physical and chemical properties of water and soil. This study aimed to prepare the spatial maps of the mentioned parameters in the plains of Islamabad-Gharb district, Kermanshah province. In previous studies, kriging and IDW methods have been found to be suitable for zoning the physical and chemical properties of groundwater and soil. Asadzadeh et al. (2019) investigated the spatial changes of groundwater quality indicators in Ardabil plain by kriging method to investigate the water situation in this area for irrigation systems. Yonesi et al. (2020) also zoned some critical water quality parameters (such as nitrate) of the Najafabad aquifer using the kriging method. Kumar and Sangeetha (2020) used the IDW method to classify groundwater quality in the study area and classify it according to drinking and agricultural uses. Karami and Basirat (2015) evaluated the spatial variations of some surface soil characteristics of Arsanjan plain by kriging and IDW methods. on the other hand, a specific method can not be considered the best method for intermediation and zoning of these parameters. In this study, both methods were used for mediation.

Sustainable development and survival depends on environmental protection, especially water. Water treatment aims to produce safe and healthy water, which is possible in water treatment plants. Therefore the importance of water is understandable, and the importance of building and equipping a water treatment plant is paramount. Many principles have been proven. Moreover, ideas for upgrading treatment plants worldwide have increased treatment plants' capacity and improved water quality.. The proposed methods can not only be applied to optimize existing water treatment plants but can also be used to design New refineries will also be used. One of the critical parts that are considered in clarifiers is the weir part. Increasing the weir width to increase the discharge capacity of the design due to the width limit is one of the problems that designers face. This has led engineers to design weirs with nonlinear geometry. Congress weir and piano keys are two essential types of nonlinear overflows in which the length of the weir crest is increased by the crinkle of this structure in the plan. The use of nonlinear overflows is increasing worldwide, which has led researchers to estimate the discharge coefficient for weir efficiency. Tullis et al. (2020) conducted a study to investigate the effect of engineering specifications on the hydraulic performance of congressional weirs. The results of this study showed the effect of the number of weir cycles on hydraulic performance. As the number of congressional weir cycles increases, the hydraulic performance of the overflow decreases. Kumar et al(2019)., in their research, examined the effect of the ratio of crest length to width (L/W) and overflow height (P) of the piano key. Using soft calculations, the discharge coefficient was considered a function of geometric variables without the dimension of piano key overflow. Therefore, in this research, an attempt was made to evaluate the hydraulic flow in the overflow of refinery clarifier structures with the shape of a piano key at its outlet using a physical model.