فصلنامه علوم و مهندسی آبیاری
سال چهل و سوم شماره 4 (زمستان 1399)

There are many slopping lands in Chaharmahl-Bakhtiari Province of Iran, located in the central Zagros, which have suitable conditions for production of rain-fed horticultural products. This study was an attempt to determine the appropriate regions for almond and vine rain-fed cultivation in this province. Water requirement (ET) of the trees was calculated by local information of weather and plants. Annual precipitation (P) and ET were probabilistically analyzed. Required area for micro-catchment (Ac) and suitable regions for rain-fed gardening were then determined at different probability levels (p ) or return periods (T). Finally, average expected yields of almond and grape was estimated. Mapping the gardening-suitable area showed that inappropriate regions for rain-fed almond and vine culture are concentrated in the eastern part of the province due to less P and higher ET. Moreover, almond generally needed larger Ac than vine (about 43%) due to higher ET. Results also showed that increasing runoff coefficient (C) was more effective than enhancing water storage efficiency (E) in reducing required Ac, therefore, increasing 10% and 20% of C and E lead to 48% and 28% smaller Ac, respectively. Average required Ac for almond was calculated as 17.4 m2 which resulted in production of 549.0 kg/ha with p =50% (T=2). The corresponding values for the grape were 9.5 m2 and 2,128.8 kg/ha. Overall, the western areas in the province were more appropriate for rain-fed almond culture, whereas rain-fed vineyard gardens are preferred to be constructed in the eastern parts of the province.

The quality of water can significantly affect concrete properties, including ultimate strength and efficiency. The present work provides a feasibility study of utilizing sugarcane wastewater in the fabrication of concrete for covering irrigation channels. Three other water types, including reverse osmosis (RO) water for the fabrication of the control specimen, tap water, and river water, were employed for comparison purposes. The specimens fabricated using different waste types were maintained within a concrete curing pond for 7, 14, and 28 days. The results showed that the resistance of samples prepared with sugarcane wastewater increased up to 14 days and then decreased resistance by 32%. The use of sugarcane wastewater reduced the efficiency of concrete by up to 75% compared to the use of treated water. Concrete prepared with sugarcane wastewater can be used to fill existing cavities caused by reinforcement in hydraulic structures.

In this paper, the quarter-circular crested stepped spillway (QCSS) is introduced and its hydraulic properties including the discharge coefficient (Cd) and energy dissipation of flow are investigated. The QCSS consists of a quarter-circular as the crest and a stepped chute. The Cd of QCSS variates between 0.9 and 1.4 considering the range of relative upstream head (hup/R) between 0.1 and 1.0, but at the same range of hup/R, the Cd of the broad crested stepped spillway (BCSS) changes between 0.9 and 1.0. The ratio of energy dissipation changes between 30% and 98% for both hydraulic models. Comparing the performance of QCSS and BCSS shows that in the skimming flow condition, the Cd of QCSS is about 30%more than the BCSS. Whereas, in the same flow regime, the energy dissipation of the flow on QCSS is a bit less than the BCSS about 10%.

This study has investigated the effect of roughness such as screen and 3D-porous obstacle with different arrangements on steps, 3D-porous obstacle, and continuous obstacle at the edge of steps in two slopes of 1:2 and 1:3 for all three regimes in the stepped spillways. The image processing results showed that the roughness of the spillways makes the recirculation zone under the pseudo-bottom smaller and a transparent region is formed in the inner corner of the spillway where there is no air bubble. Moreover, adding roughness on bottom and placing the 3D-porous obstacle and continuous obstacle on the edge of step in the step spillway cause the inception point of free aeration move down to the downstream compared with flat steps on both slopes. The placement of the 3D-porous obstacle and screen in all arrangements, as well as the continuous obstacle and 3D-porous obstacle on the edge of the spillway at 1:2 slope do not have a positive effect on the energy dissipation on transition and skimming flow regimes; however, by placing the obstacle at the edge of the spillway with a 1:3 slope, the dissipation performance of the spillway increased for all three regimes with an average of +5%.

This research conducted various experiments using a wind tunnel on soil samples from the most critical parts of dust sources in southeastern of Ahvaz. The main goal of this study is to show the effect of moisture on the movement of soil particles in the dust centers. The laboratory work was carried out in two parts: a: Addition of water to completely disturbed soil surface (wetting in the bag) b: Addition of water to soil layers of samples wetting that was named pseudo undisturbed soil. The results showed that dust generation under natural conditions (dry soils) in a laboratory wind tunnel will be 53 times more than the pseudo undisturbed soils with moisture content of 2-4% in volume. Moreover, soils with moisture contents of 5-8 and 10-12% do not differ significantly from those with 2-4% moisture content in preventing dust generation. If soil surface is disturbed after it is provided with adequate moisture, not only will dust generation not decrease compared to the case when the soil surface was dry but it will also increase by 25 percent. The practical point of this study is that in the study area, increasing soil moisture between 2 to 4% can greatly reduce the formation of dust.

The drying of lakes and wetlands is a significant challenge to the hydrological cycle of resources, to human life, and to animal and plant species. The bed soils of lakes in arid and semi-arid regions become dry and wet due to various factors, such as global warming, which decrease and increase water levels in lakes. Therefore, field measurements and surveys are necessary in the localities of these natural ecosystems and can improve the management and protective measures against various hazardous processes including wind-driven soil erosion in these areas. The purpose of this research was to evaluate the soil erosion potential of Lake Bazangan, a natural lake located in the province of Khorasan Razavi, Iran. Experiments of soil properties were performed to study the rate of soil wind erosion. Wind tunnels were used to model the airflow. The results showed that the clay particle content significantly reduced soil wind erosion rates. Because of SAR's effect on the dispersion of clay particles, the erosion rate increased exponentially with soil solidification. Soil moisture had a significant effect on the cohesion of clay particles and, therefore, reduced the soil wind erosion rate. In this study, the surface erosion of the samples was examined using a calibrated Kinect® sensor, developed by Microsoft, due to easy access, cost-effectiveness, and high accuracy of its sensors. It was observed that sand particles could move easily, with a significant effect on the rate of soil loss.

High flow discharges coming from the hydraulic structures usually carry a high-velocity jet of flow, which could have different short- and long-term impacts on the river mechanics and the habitat conditions. Scouring is one of the major effects of the incoming flow jet, which, once aerated, has a dynamic behavior and structure. Plunge pools are hydraulic structures to prevent the severe damages of the scouring phenomena. In the present study, due to the high complexity of constructing a physical model, the effect of air entrainment on scoured hole’s depth is assessed using the Artificial Neural Network (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS) methods. Each soft computing model’s performance on the scouring is compared to a Nonlinear Regression Method’s result using different statistical measures (RMSE, ME, MAE). The prediction accuracy of ANN, ANFIS, and nonlinear regression using RMSE was calculated as 0.0137, 0.011, and 0.0262, respectively. This study presents a novel achievement in measuring and predicting the scoured hole’s depth as one of the most critical phenomena in hydro-environmental science.

Bridge pier local scouring is a crucial factor in bridge destruction. Studies from different researchers have presented solutions to control this phenomenon. These solutions are divided into two parts, namely, direct and indirect protection. In the direct method, the bed is armoured against scouring whereas in the indirect methods the flow pattern around the pier is changed with geometric parameters. This study defined an element called the deflector structure (flow diverter) to divert the bed’s flow streamline in front of the pier. Experimental scenarios were defined by stabilizing the flow conditions with 0.70, 0.83, and 0.97 relative velocities ( ) and 15-, 30-, and 45-degree wedge deflector structure angles with flow direction for two piers with square and circular cross-sections. The results showed that the dimensionless scour depth parameter ( ) close to the particle movement threshold ( ) was reduced by 70 to 75%, respectively relative to the control model for square and circle cross-section. Changing the angle from 45 to 30 and 15 degrees reduces the local pier scouring and increases the deflector structure’s effectiveness.

Saturated hydraulic conductivity (KS) can be determined with correlation or hydraulic methods. Hydraulic methods can be classified as laboratory and large-scale or small-scale in-situ methods. Auger-hole, inversed auger-hole and Guelph Permeameter are the most common small-scale in-situ methods. The KS determined by small-scale methods has high spatial variability, has different values in the horizontal and vertical directions, and varies in different depths. Large scale methods enter an extensive soil body into the measurement process to eliminate variation. This paper aimed to evaluate the conventional field methods of measuring KS using the drain outflow as the reference method and investigate the effect of initial soil moisture on KS’s measuring accuracy by the inversed auger-hole method. Experiments were conducted in two 10-hectare research fields in south Khuzestan. KS was measured by the inversed auger-hole method in barren, dry soil before constructing the irrigation and drainage network. After the construction, the KS was measured by drainage water outflow as a large-scale method, as well as by auger-hole and inversed auger-hole methods in moist soil after several irrigations. The KS measured by conventional small-scale in-situ methods in Fields One and Two were respectively 42.5% and 62.9% lower than the drainage water outflow method. Considering the drain outflow as the reference method, there is no significant advantage between the auger-hole and inverse auger-hole methods. As in Field One, the values obtained from the auger-hole method were closer to the reference method, and in Field Two, the values obtained from the inversed auger-hole method were closer.

Water and other fluid pipes that are placed on the seabed and rivers bed change the flow pattern around them. These changes increase the shear stress of the bed and the severity of turbulence around the pipe and create a scouring hole under the pipe. The scouring under the pipe may lead to instability, bending, and even breakage of the pipeline. In this study, local scouring around pipelines across the river in unsteady flow conditions was investigated. In the experiments, three pipe diameters (20, 40, and 60 mm) and three installation depths (on the bed, a quarter of the pipe diameter above the bed, and half of the pipe diameter above the bed) were used. It can be understood from the results of this laboratory study that the amount of final scour depth due to the passage of flood hydrograph is always less than the scour depth due to the steady flow corresponding to the peak flow of the hydrograph. For different pipe installation depths, the amount of scouring for the installation depth of one-quarter of the pipe diameter above the bed in both steady and unsteady flow conditions is higher than other installation depths.