فصلنامه مهندسی منابع آب
پیاپی 56 (بهار 1402)

In recent years, the supply of energy for irrigation systems of pistachio gardens in Pakdasht is an important issue. With the implementation of targeted subsidies plan, the price of energy has increased significantly. In these conditions, the use of solar energy is the best solution, especially for areas away from the national electricity grid.

In this study, drip irrigation system was designed for 4 pistachio gardens in Pakdasht with areas of 12, 24, 48 and 96 ha and slopes of 0, 1, 2, 3 and 4%. Irrigation was done in two modes: 24-hour irrigation, 12-hour irrigation, then the annual investment costs of the solar system and the national electricity were calculated.

Comparison cost of solar equipment in 12 and 24 hour irrigation showed that in the slope of 4%, the cost of solar equipment in 24-hour irrigation for 12, 24, 48 and 96 ha were 0.6, 0, 68.45 and 97.36 million Rials more than cost of solar equipment in 12-hour irrigation and the investment cost of mechanical equipment and purchasing pipes in 12-hour irrigation were 9.68, 70.46, 240.93 and 451.25 million Rials more than cost of them in 24-hour irrigation, respectively. In general, total cost of the solar system in 24-hour irrigation is less than 12-hour irrigation. Selected solar system (24-hour irrigation) was compared with a pumping system connected to the national electricity grid. The comparison showed that economic feasibility of solar system is depend on the pumping station power and distance of gardens from the national grid.

Proper knowledge of groundwater geochemistry and identification of the risk factors for the aquifer system is very important to control and improve the management of groundwater resources in arid and semi-arid regions.

Sampled data during six years from 2014 to 2019 were used to assess the temporal variation of geochemical parameters of the wells in the study area. Water quality index (WQI), Piper diagram, Wilcox Diagram, and Gibbs Diagram were employed for evaluating the status of groundwater using sampled data in 2019.

The results showed that the total hardness (TH) exceeded the standard value proposed by WHO for six years. The study area is categorized in a moderate range in terms of drinking water quality. Calcic-bicarbonate and temporary hardness (Ca-Mg-HCO3) were obtained as the hydrochemical factor and type of the groundwater in most of the samples, respectively. A little salty and salty water were identified as the status of groundwater quality for agricultural purposes. Rock dominance was also determined as the controlling factor in groundwater of the study area. The results of multivariate statistical analyses indicated that wastewater, fertilizers, agricultural effluents, and geological structures were the most important sources of entering the hydrochemical parameters.

The results of this study indicated that anthropogenic activities, geology structures, and the effects of Urmia lake are the most important factors to the concentration of physicochemical parameters in the groundwater.

The use of obstacles in dam reservoirs is considered an effective method for directing sedimentation toward the middle of the reservoir (instead of sedimentation next to the dam wall where the facilities are located). In the present study, to control the saline density current, the effect of cylindrical, cubic, and pile-shaped obstacles on the characteristics and motion of the body of the density is experimentally investigated.

In this regard, 323 cylindrical obstacles with a diameter of 1 cm and a height of 30 cm, were placed on the bed of a Plexiglas in a channel with a length of 12.5 m, a width of 30 cm, and a height of 40 cm in a zigzag form along with the same number of cubic obstacles with dimensions of 1.1 cm and a height of 30 cm in the next step. The experiments were performed with three flow rates (0.27, 0.55, and 0.83 liters per second), three slopes (0.2, 0.5, and 1%), and constant concentration (15 g/l).

The results showed that the use of obstacles reduces the height of the body of density current along the channel. The height of the body in cubic obstacles is more than cylindrical obstacles. The use of obstacles affects the velocity profiles and reduces the velocity of the body of the density current. The flow rate of the body of density current in a bed without obstacles has an increasing trend while it has a decreasing trend in the bed with obstacles. Therefore, the reduction of flow rate in cubic obstacles was 1.5 to 2 times compared to the cylindrical obstacles. As a result, flow rate control in cubic obstacles was greater. Also, by moving along the channel, the reduction of the concentration of body of the density current in cubic and cylindrical obstacles was 49% and 41%, respectively, compared to the bed without obstacle

As a result of global warming, the climate will change in terms of average temperature and rainfall, with groundwater being one of the factors impacted. Consequently, the influence of climatic elements such as temperature and precipitation on groundwater drought values in the Talesh plain was investigated.

Initially, the LARS-WG model was used to calculate climate change values. Subsequently, using the Mann-Kendall test and the Pearson correlation of these two indices, the values of meteorological and groundwater drought indices were produced, as well as a study of the trend of these indices.

The findings of the annual changes in rainfall and temperature throughout the following period (2020–2040) reveal that precipitation of 9, 1.75, and 0.75% and the temperature of those have grown by 1.05, 1.32, and 1.81 °C under the scenarios of RCP2.6, RCP4.5, and RCP8.5, respectively. Also, in the basic period, the declined average level of the aquifer in this 15-year period was 0.86 m. On the other hand, the impacts of climate change on decreasing groundwater level over the future period compared to the base period under the above scenarios indicated that the aquifer by 2.07, 2.21, and 2.34 m, respectively. Although it indicates that the rainfall has risen in the area, unrestricted drain from the aquifer has resulted in a decline in groundwater. The study also reveals that meteorological drought occurred in the basic era at a rate of 49.66, 50.35, and 41.73% at the scales of 12, 24, and 48 months, respectively. Therefore, in order to mitigate the severity of the drought and avoid excessive groundwater aquifer fall in this plain, required actions are essential to decrease water consumption by water resources managers and executive bodies under the present circumstances.

A physical model was prepared to investigate the effect of the geometric shape of the bridge pier with the abutment attached to it on the reduction of scour depth. This model was made of a laboratory flume with a length of 7.5 meters, a width of 30 cm, a depth of 45 cm with a variable slope and a glass body with bridge pier width of 4 cm were used. For bed sediments, a layer of natural river sand with an average diameter of 0.9 mm and a standard deviation coefficient of 1.1 and a uniformity coefficient of 1.25 were selected and used in a layer with a thickness of approximately 14 cm for experiments.

The geometric shape of the bridge piers, as well as the presence of the footing, prevents direct contact of the descending current, reduces the activity of horseshoe vortices and thus reduces the scouring speed, and delays the scouring start time.

According to the results of the experiments, the greatest decrease in scour depth was related to (0.26 descent and p1 base). The results showed that in the same condition, the relative scour depth at p1 base was less than other bases and reached its maximum in the control base. Also, the relative scour depth increased with increasing the number of landings in the same position. The abutment attached to the bridge base has reduced the scour depth by 29.6%.

In the present study, we investigated the effect of the location and height of a three-dimensional porous obstacle (with porosity in all three dimensions) which is located on the bottom of the steps in the width of the flume and the number of steps with this type of obstacle has been investigated on a stepped spillway.

The slope of the spillway was 1: 2 and had 8 steps, the total height was 87 cm and the width of the flume was 1.2 m. The measuring instruments in the present study were point gage, image processing technique and observations of the experiment.

In a continuous three-dimensional porous obstacle, according to the relative height, location and number of steps with an obstacle, the starting flow boundaries of the placement change compared to the flat step, so that by increasing the relative distance of the obstacle from the edge of the steps and decreasing the number of steps with continuous porous obstacle. The tendency of the flow to expand in the upper range of the transition flow (neighborhood with the skimming flow regime) increases.

In the nappe flow regime, the placement of a three-dimensional porous obstacle for the variables of the present study increases the energy dissipation by up to 5% more than in the flat step (control). For transitional and skimming flow regimes, in most cases, continuous porous obstacle placement has no positive depreciation effect. In addition, according to the size of the areas formed by BIV, it can be said that in conditions where the mixing area measured in two consecutive steps was more than the flat step, energy dissipation has also increased.

Drought is one of the natural hazards that have random and nonlinear behavior due to its various climatic parameters. SPI index is the most common index extracted from rainfall that has been used in modeling drought by various researchers.

The use of computational intelligence methods to model drought in recent years has been much considered by researchers in the field of water resources. In this research, SVR and GPR algorithms individually and also the combination of these algorithms with wavelet algorithms have been modeled and predicted by SPI index, and the purpose was to evaluate the improvement of computational intelligence algorithms in combination with wavelet. In this research, the time series data of 10 synoptic stations in Iran in the period 1961 to 2017 have been used on a monthly basis for modeling the drought as the input of the studied algorithms.

The results of this study showed that the use of the wavelet method in combination with SVR and GPR computational intelligence algorithms improved the results in all time scales. Also, the modeling improvement is due to the use of wavelet in combination with the SVR model with an average RMSE difference of -0.1540 and R2 difference of 0.1491 and the GPR model with an average RMSE difference of -0.1554 and R2 difference of 0.1530 Compared to the single SVR and GPR models showed that the GPR model in general (all time scales and all stations) had a better improvement in the hybrid model than the single model.

Iran is located in arid and semi-arid climate and the rainfall in Iran is less than one-third of the world average. The agricultural sector is the main cause of water loss, as more than 90% of the water is consumed in this sector.

This study is a survey. Documentary method has also been used to develop theoretical records and empirical records.

The effects of water scarceness on social security feeling variable showed that 32.2% of its changes were explained by the model. There is a covariant relationship between external factors affecting the sense of collective security and the sense of intellectual security, as well as external factors affecting the feeling of surface water shortage and the sense of life security. On the other hand, the feeling of lack of surface water has a direct effect on the sense of intellectual security. The results of this study show that water scarcity has a direct impact on farmers' safety, based on the findings, the mean sense of social security and its dimensions among farmers in Fahlian plain which has better water resources status is more than the amount for Kharameh farmers who have poor water resources status, so water scarcity is effective in terms of financial, life, intellectual and collective.