فصلنامه مهندسی منابع آب
پیاپی 48 (بهار 1400)

Oxygation is a variant of subsurface drip irrigation in which ambient air is injected through the system via a venturi, thereby plant roots receive air and water simultaneously. The objective of this research was to study the effect of two surfactants and certain ratios of them on the uniformity distribution of emitter air flow rates along lateral pipes in an oxygation system.

Two non-ionic surfactants, namely, Triton X-100 and Tween 80, and three mixtures of them with different ratios including 2:1, 1:1, and 1:2 were added to irrigation water and the results were compared to the case where no surfactant was used. For statistical analysis of data, the Kolmogorov–Smirnov and Friedman tests along with Christiansen Uniformity Coefficient were used.

In the absence of surfactants, Christiansen uniformity coefficient (CUC) for emitter air flow rates was -67 percent. The relative increase in CUC, when Triton X-100, Tween 80, and the ratios 2:1, 1:1, and 1:2 were applied, amounted to 211, 162, 210, 213, and 206 percent, respectively.

The results of this research clearly indicates that application of surfactant mixtures with synergic interaction will effectively enhance distribution uniformity of emitter air flow rates.

Cavitation is one of the most important problems that may occur due to high flow velocity in dam spillways. In order to predict of dam spillway structure during operation, Azad dam spillway hydraulic model has been modeled in Tehran Water Research Institute.

In this study, using computational fluid dynamics in the form of a finite volume method used in ANSYS FLUENT software, flow modeling in these channels, and a fluid volume model (VOF) in a three-dimensional state, including two-phase flow of water and air, used for Considering current turbulence, k-ε model has been used. In order to confirm the results of the model, a comparison was made with the results of a hydraulic model implemented without the aero-damping system of Azad spillway.

Then, in order to confirm the location and number of aeration systems, two scenarios (two and three aeration systems) including step ramp (RAMP) on the floor and the wall of the duct with a suitable slope and the installation of the aeration slot in the wall have been used, which sends air near the floor And the walls will be.

Then, by checking flow parameters such as speed, pressure and cavitation index, overflow with two aeration systems was confirmed as the best option.

Choosing a water meter for a household is one of the major issues in water and wastewater companies. In recent years, due to the increase in the number of subscribers, increase in the number of accident due to the inadequacy of water meters, also various parameters of the water meter and environmental and regional conditions, the selection of water meters is more evident. The decision maker needs to select the most suitable water meter to achieve the desired output at a lower cost and his ability.
Studies show that there is no research on the use of MADM techniques in the field of water meter selection for household use. In the research of industrial and volumetric meters, also only a few parameters have been investigated and according to the researcher's opinion, the solution has been presented without considering the quantitative effect of factors. In the present research, first, the key attribute for evaluation of the meters are identified. Then based on the Entropy method and opinion of industry experts, the weight of criteria is calculated. Then, TOPSIS technique attempts to present a strategy for water and wastewater companies to choose suitable meters for home appliances.
Finally, the calculations for meters’ attribute determine the relative importance of attribute and also water meter ranking, which can be used for selection of the water meters.
According to the results of this research, the order for selecting the water meters is presented, that semiconductor multi-jet meters ranked in the first order.

Following the terrorist attacks of September 11, 2001 in the United States, concern about the security of water distribution systems has increased. Water distribution systems are highly vulnerable to intentional or accidental contamination, due to their physical and geographical characteristics. Such threats can affect public trust in the distribution system. Putting a contaminant warning system up, including sensors in the water distribution network, is a hopeful approach to disconnect water supply networks at the time of the occurrence of pollution. Due to the high cost of purchasing, installation and maintenance of such sensors, their location should be calculated by using optimization algorithms.

In this research, a multi-objective optimization model has been developed using harmony search algorithm to calculate the optimal location of detection sensors in water distribution systems based on two criteria for minimizing the time detection of pollution and maximizing the coverage of sensors. The simulation of events in different scenarios is done by connecting the EPANET hydraulic model toolbox and the MATLAB software, and the second example of EPANET software is as the case study.

The results show that the optimal detection time is 19296 seconds
and the optimal coverage is 26494 gallons per minute. By increasing the importance of optimal detection time to the increasing the sensor coverage, the detection time decreased by 32%, and the sensor coverage, by contrast, decreased by 26%.

It seems that in situations where two criteria are of equal importance, one of the sensors is located in a crowded place to reduce the time of contamination detection and the other in the middle of the network to increase network coverage.

The leading cause of damages on bridge is local scouring around piers. Many studies were carried out to control and reduce this phenomenon and suggested more solution methods to protect bridge piers. Protection is divided into direct and indirect methods. In this study, to reduce scouring depth around the pier, an indirect method is used by changing the pier's head angle in a flow direction.
An experimental study on clear-water at a different angle of piers head under steady flow is presented. Experiments were used to assess the ability to change the head angle of piers to protect them. Toward this end, five angles (α) 90, 85, 80, 75, 70-degree with the flow direction were considered. The bed material size d50 was 0.9 mm and all experiments were done in Gunt hydraulic standard flume.
The results showed that the pier with a 70-degree attack angle could reduce the scour depth more than others. This happens due to diverting part of streamlines to downstream, and it can have a 36 per cent reduction overall.
The scouring depth and sediment point bar created around the pier with an inclined head compared with the control pier (α=90-degrees) have less scouring depth due to minor deviation of flow streamlines and reduction of disturbances around the pier.

Iran is facing shortage of water resources due to the climate in which it is located. Since large areas of urban surfaces are Impenetrable streets, the volume of water harvested from these surfaces is significant and can reduce the pressure on water resources and meet a large portion of the non-potable demands, it also prevents the spread of pollution caused by overflows and backlogs in surface water collection facilities and uneconomic increase of their volumes.
In this paper, the design of rainwater harvesting system from asphalt surfaces was carried out with the aim of meeting part of the green space demand of Tarbiat Modares University faculty of agriculture, using drone images. For this purpose, available data of 22 years of daily precipitation and 761 aerial images were obtained using DJI Phantom3 Professional drone. Then, the digital elevation map of the case study was prepared and to determine the runoff direction, the basin of the area was carried out in the GIS. Reliability percentage and overflow ratios of the tanks were estimated for each level for different tank volumes. Then the optimal volume of each tank was determined using genetic algorithm.
The results showed that due to the topographic status of the faculty street surfaces, the runoff from them could not be collected in one tank, so 4 tanks A, B, C and D with optimized volumes of 6.15, 3.46, 1 and 20 cubic meters were considered in different parts of the street surfaces, respectively.
With designing rainwater harvesting systems, a significant amount of rainwater can be stored for non-potable consumption.

Considering Iran's place in arid and semi-arid regions, inappropriate distribution of barley rainfall, water storage and dam construction are necessary. One of the important issues in the preservation and stability of earth dams is the seepage problem, which, considering that the water head in the upstream reservoir of dam is changing in different seasons of the year, the amount of seepage of the dam changes continuous.

In this study, transient seepage for 2D and 3D modes was investigated using SEEP/W and SEEP 3D software based on finite element in upstream and downstream reservoirs for saturation and semi-saturation modes.

Considering this modeling, by increasing the water level in the upstream reservoir, the amount of seepage of dam increases and vice versa, which indicates a direct relationship between them. The accuracy of the calculated seepage thorough SEEP 3D software is higher than SEEP/W software in two-dimensional mode for saturation mode, which its determination coefficient thorough SPSS software is equal to 0.92, in comparing to the actual seepage at that point, which indicates the high compatibility of this software with reality. For the semi saturated mode at the downstream of the dam when the water level decreases upstream, the calculated seepage accuracy in seep/W software is higher than seep 3D software and its determination coefficient is 0.72, which indicates the superiority of SEEP/W software for two-dimensional modeling of transient seepage in semi-saturation mode.

In general, SEEP/W software is more accurate than SEEP 3D software for calculating transient seepage in semi-saturated soils.

Identification and evaluation of effective parameters in Inter-Basin Water Transfer (IBWT) projects are essential for the calculation of financial and economic indicators. Due to many qualitative parameters in these projects and inability to quantify most of them, an integrated economic valuation model is presented in this study.

In this model, the effective criteria and indicators are first prioritized using Analytic Network Process (ANP) as a Multi Criteria Decision Making (MCDM) method. Then, these criteria and indicators are quantified by two direct and relative valuation methods. Finally, two financial indicators: Benefit-Cost Ratio (BCR) and Net-Present Value (NPV) are modified and evaluated.

The results indicated that the political and security criterion is in the first place with significant difference with the others. Also, applying model for economic reassessment of the Chalus Water Transfer Scheme in Iran showed the value of BCR at discount rates of 6% and 8% are to be 0.2 and 0.14, respectively; and NPV is negative. Therefore, this project is not considered to be economically beneficial at its present feature.

It seems that political and security issue is very considerable in Inter-Basin Water Transfer (IBWT) projects. On the other hand, quantifying and valuating effective parameters can help more accurate economic analysis for new and ongoing projects