فصلنامه علوم و مهندسی آبیاری
سال چهل و پنجم شماره 1 (بهار 1401)

Today, gabion structures and especially gabion stepped spillways have become more popular due to the significant effect of stairs on flow energy dissipation, appropriate stability, being economic, easy implementation, and raising the oxygen level in the water. This type of weirs has more flexibility compared with its impervious type and is resistant to loads due to water pressure. The resistance to water load is likely to be related to flow passing through the porous media, and the gabion stairs can assist with the faster water drainage and reduce the water load behind the structure (Zhang & Chanson, 2016). Extensive studies have been performed on impervious stepped spillways, namely Gonzalez et al. (2016) and Zhang and Chanson (2015).Reeve et al. (2019) used a numerical model to investigate the flow hydraulic properties on gabion stepped spillway. They studied gabion stepped spillways with four different stair geometries under similar conditions. Their results indicate that flat gabion steps can dissipate more energy than overlapping, inclined, and pooled steps.Despite extensive investigations on impervious stepped spillways, there has not been sufficient research on gabion stepped spillways. Hence, the primary purpose of this study is to investigate the gabion stepped weirs features, including energy dissipation and characteristics of downstream hydraulic jump.

In general, the entry of sewage into rivers and the decomposition into river water has led to a reduction in water quality and, in particular, a decrease in DO concentration (Sarda and Sadgir 2015). To have the optimal water quality characteristic, river reception capacity should remain within acceptable limits along the river. Using management tools, including water quality simulation models, can be very beneficial in this context. QUAL2KW is one of the best tools to simulate water quality due to its flexibility, ease of use, and availability. Studies with the QUAL2KW model for simulating water quality in rivers and basins using parameters BOD (Fang et al. 2008), Nitrogen, Phosphorus, and COD (Grabiç et al., 2011) have been carried out. This study aims to provide a model for simulating water quality parameters in rivers with steep slopes and short paths. Therefore, the analysis of BOD, DO, and COD qualitative parameters and awareness of the Abbas-Abad River's location and time trends (seasonal) in Hamadan during dry and wet seasons were considered.

Accurate estimation of water requirements of plants is a key factor in controlling several hydrological processes including: planning and management of water resources, especially in arid and semi-arid regions (Laaboudi et al., 2012; Wen et al., 2015) water pricing and water requirement for Irrigation (Yassin et al., 2016). In this study, multivariate regression methods and gene expression planning were evaluated to estimate reference evapotranspiration. For model input data, the Khorramabad Synoptic Station information including: maximum and minimum temperatures, maximum and minimum relative humidity, sunny hours and monthly wind speeds in the range of 1983-2017(420 months) were used. Based on the relationship between input and output parameters, six input patterns were determined for modeling.70% of the data were used for training and 30% were used for model validation.The results of multivariate regression showed that the proposed model had acceptable accuracy with R2 = 0.952.The analysis of model coefficients showed the greatest effect of maximum temperature with a coefficient of 0.604 on reference evapotranspiration. Gene expression planning results showed that the fifth pattern with four main operators was R2 = 0.958 and RMSE = 0.704 in the training phase and R2=0.977 and RMSE = 0.615 in the test phase had better performance.

Salt-affected soils have gained a major global-regional-national-ecosystem-farm level concern (Hossain, 2018). One of the important options in leaching is to precisely determine the volume of water required due to the problem of water scarcity (Karandish, 2016; Babazadeh et al., 2017). The aim of this study was to evaluate the amount of leaching water in two continuous and intermittent methods to compare these two methods with each other and with pre-leaching soil characteristics on three series of saline soils of Mighan plain in Markazi province with different texture. Leaching operations were performed using the methods described in 50 cm in 5 alterations. Electrical conductivity and soil sodium absorption ratio after leaching were measured and compared with these two parameters before leaching. Also, in order to determine the most appropriate leaching method, Dunnett multiple comparison test was performed in three areas and five soil depths. The results of this study showed that, on average to the desired depth, leaching improved soil salinity and sodicity so that soil salinity was reduced from 20.12 ds/m to 7.80 ds/m in continuous leaching method and to 5.63 ds/m in intermittent method and exchangeable sodium percentage was declined from 40.35 to 37.11 in continuous leaching method and to 29.18 in intermittent method. The lack of decrease in exchangeable sodium percentage due to the decline in soluble salts and relative abundance of sodium ion in soil solution after leaching which confirms the study of soluble cations in the soil. It is resulted that, intermitted leaching method has better leaching efficiency in all three areas and can be recommended for leaching the soils of the study area.

Accurate prediction of dam breach parameters in embankment dams is an essential step in the risk management plan. Overtopping and piping are the leading causes of embankment failure in the world. The failure of this type of dam is typically proposed by hydrological and hydraulic computational models of the dam (Wahl, 1998). The relationships for assessing the breach and flow characteristics are generally obtained by artificial intelligence and regression analysis from case studies of historical dam failure. These models relate the input parameters such as the dam height (Hw) and the flow volume through the breach (Vw) to the observed breach parameters resulting from the actual failures. Several relationships have been proposed to calculate Qp as a function of Hw and Vw (De Lorenzo & Macchione, 2014; Hagen, 1982; Kirkpatrick, 1977; Singh & Snorrason, 1984; Hakimzadeh et al., 2014). Downstream sediment transport studies show that breach geometry directly affects the output hydrograph. Investigations on historical records for Qp determination show that Hw and Vw could provide more accurate results than El and Ew. Moreover, the combination of these parameters significantly increases computational accuracy (Thornton et al., 2011; Wang et al., 2018). Several laboratory and field studies have been performed to investigate the hydraulic properties of the breach and the output hydrograph in overtopping failure cases (Dhiman & Patra, 2017; Sadeghi et al., 2020; Vaskinn et al., 2004). Determination of the average breach width (Bave) is an essential factor in determining progressive erosion (Von Thun & Gillette, 1990; Froehlich, 1995) as well as the height of breach (Hb). The range of variation in Bave as a function of the dam height (Hd) is an important issue in the breach lateral evolution process (Johnson & Illes, 1976; Singh & Snorrason, 1984).

Optimizing the use of water resources is inevitable due to water shortages in agricultural areas.  Pistachio gardening has been an attractive agricultural activity for several decades in Iran. Given the limited water resources, areas under pistachio cultivation in arid regions are not economical due to low production. There has been a continuous trend towards application of efficient irrigation systems such as pressurized subsurface drip irrigation methods, but their complexity and high initial investment, make them less suitable for small scale and scattered owners. This research describes the field performance of a very low-pressure subsurface irrigation method which has been introduced before (Dastorani et al., 2010). In this subsurface porous pipe irrigation system, water is delivered directly to the pistachio tree’s roots via perforated PVC pipes covered by plastic textile sleeves. The feasibility of this system has been demonstrated for irrigating pistachio orchards. They compared the effect of traditional (surface) irrigation and such subsurface irrigation method on crop yield and annual growth traits. Their results showed that subsurface irrigation method had relatively higher performance than the surface method. To accurately design such a system, it is necessary to assess the time variations of irrigation parameters including lateral infiltration q (leakage flow rate per unit length), local water pressure along laterals Px in terms of input water flow rate If , and pipe orifice density n, as it is the subject of this research.

The recent growth in population has led to an increase in food supply requirements which, in turn, has resulted in an increase in groundwater exploitation. In areas where fresh and saline aquifers are adjacent, the overexploitation of fresh groundwater leads to a decrease in fresh ground water level and, as a result hydraulic gradient of saline groundwater towards fresh groundwater increases. Also, a decrease in fresh groundwater level leads to a decrease in the plain discharge. This way, the saline water cannot exit the plain and pressure head rises leading to extra waterlogging and salinization. Interception drain is an effective solution to intercept saline flow and discharge it out of the plain. In effect, the drainage system reduces saline water table level and prevents waterlogging and salinization. Salt marshes of Qazvin plain, located in the south-east of Qazvin, is facing the same problem and saline soil areas in the region have accordingly increased 10000 ha in recent years (Saman Abrah and Kamab Pars engineers, 2010). An interception drain system was thus implemented in the study area in order to reduce the saline water table level and prevent waterlogging and salinization. Following the construction of the drain in the region, 99 observation wells were also drilled around the drain in 9 sections (A-I) such that each row has 11 observation wells so as to monitor the groundwater fluctuation and salinity. At each section, 7 wells were located on the upslope and the remaining 4 wells were on the downslope (Sotoodehnia et al, 2014). However, it takes a lot of money and time to measure water table level and salinity from observation wells continuously. Modelling is indeed a cost-effective way to predict the water table level and salinity in future. HYDRUS is a powerful tool that can be used to simulate and monitor the drain situation reliably, but it should be calibrated for the study area. Calibration of HYDRUS means estimating soil hydraulic and solute transport parameters that can be done with HYDRUS inverse solution ability. Using HYDRUS-2D, Abbasi and Tajik (2007) estimated both soil hydraulic and solute transport parameters in the field scale. They also compared the measured and simulated values of soil moisture and salinity. Though soil moisture was almost overestimated, and salinity was almost underestimated, the results showed that the errors were small and the model was accurately calibrated (Abbasi and Tajik, 2007). The main objective of this study was thus to assess HYDRUS-2D ability for simulating solute transport in a very saline aquifer in the study area, and also to consider saturated and unsaturated regions simultaneously. Moreover, this study employed HYDRUS-2D to simulate salinity transport in the areas where the amounts of salinity was extremely high. According to Latifi et al. (2020), evaporation is an effective factor in groundwater fluctuations.This study also examines the effect of evaporation and aquifer thickness in an inverse solution. Aquifer thickness and evaporation have an important effect on the inverse solution due to the statistical indexes involved. Thus, some statistical indexes were carried out to assess the accuracy of calibration, and the results showed that the model was calibrated accurately.

In recent decades, changes in climate and social norms in the direction of uncontrolled extraction of groundwater resources have led to a sharp decline in groundwater levels and a reduction in the karst springs discharge. Springs that have a smaller catchment area, where a part of their catchment area is located in alluvium, and there is more connection between karst and alluvial aquifers, are more vulnerable to human activity. To evaluate these effects, karst springs in the central areas of Kermanshah province have been studied. Accordingly, four dried-up springs in the region have been studied more accurately, indicating a significant relationship between the groundwater level in the surrounding alluvium and the karst spring discharge. The study aimed to estimate the minimum groundwater level to maintain the karst springs discharge. According to the findings, if the groundwater level around the springs reaches or less specified amount, these springs will be dried. This level has been named the minimum allowable groundwater level (MAGWL). The way to preserve the springs is to keep the groundwater level of the surrounding areas above the MAGWL. According to the average annual decrease of groundwater level in the study area, the need for management and control of the extraction from the alluvial aquifers is strongly felt.

This study examined the feasibility of using zeolite clinoptilolite to filter nitrate, phosphate pollutants and salt from the agricultural drainage water. To that end, significant pollutant absorption parameters, such as adsorbent particle size, pollutant concentration, salinity, temperature, retention time, pH, and adsorbent concentration were optimized in the batch condition. Having optimized the parameters, the researchers conducted adsorption experiments on an experimental model, similar to the subsurface drainage systems applied in farms. Adsorption experiments were carried out at the optimized parameter levels on four models, namely a reference model (D0), a model with adsorbents around the drains (D1), a model with adsorbents around the plant roots (D2), and a model with adsorbents on the soil surface (D3). These models were fed with untreated drainage water from the farms in the south of Khuzestan during the fertilization season. The results showed 63 percent nitrate removal efficiency, 39 percent phosphate removal efficiency and 79 percent salt removal efficiency by using 30 g.L-1 of 1000 µm adsorbent particles for a pH of 5, initial pollutant concentration of 80 mg.L-1 nitrate and 10 mg.L-1 phosphate in 12 dS/m salinity during a 90-minute retention time period at 50 °C ambient temperature. These parameter levels led to nitrate, phosphate, and salt removal efficiencies of 59.72 percent, 29.28 percent, and 77.47 percent respectively, in the model with clinoptilolite adsorbents around the drains (D1).

Recently, desert and desertification issues are known as one of the most problem in most countries especially developing countries. With an attention to the natural resources of Iran we can concluded that the most of Iranian lands are classified as deserts. Desert scientists believe that in addition to natural factors, human factors has a significant and important role in desertification. As natural factors are the most of the desertification criteria, models of desertification potential assessment are provided locally. In this time, using of desertification models is the best method for assessment of effective factors on land degradation and desertification severity from experts viewing. Despite of models abundance, one model is the best that has adapted considering to environmental and human conditions. To assess desertification, various research done in outside and inside of Iran. Zehtabian et al (2008) was evaluated soil and water criteria base on Medalus methodology in Ain-e- Khosh’s Dehloran and presented desertification map at the end of research. Desertification intensity class is critical for the entire region based on desertification map. Shakerian et al., (2012)  Evaluated desertification intensity in Jarghooyeh region, based on IMDPA model.their results showed that, this area classified in low class of desertification. According to the new definition of Desert, more parts of Iran encounter desertification problem. In order to challenging with desertification, it is necessary to do some scientific research and assessment in different parts of the country. The results may help to control and reduce the damages resulted from this phenomenon. The aim of this research would be the effects of climate indicator on desertification with method Iranian Model (IMDPA) in central part of Iran.