مجله مدیریت آب و آبیاری
سال یازدهم شماره 1 (بهار 1400)

Due to the high cost of construction of the dams, increasing the lifespan of this construction structure has been considered by water engineers. Sediments near the dam wall reduce the useful life of this structure. Constructing obstacles in the path of density currents be is one of the most widely used methods in controlling these sediments. In this study, the effect of permeable obstacles on density current head flux has been studied experimentally. The obstacles were made in the shape of trapezoid and were filled with sand particles with a diameter of one centimeter also salt were used to prepare the density current. In these experiments, the effect of inlet flow, flume slope and obstacle height on density current was investigated. Examining the variables of this study, it has been found that the reduction percentage of the density current head flux for the dimensionless ratio of height 1 is between 33.1 to 61%, for the dimensionless ratio of height 1.5 is between 43.2 to 63.3% and for the dimensionless ratio of height 2 is between 68.2 to It is 100%, also increasing the inlet flow ratio and flume slope increases the momentum of the current and thus reduces the efficiency of the obstacles. In addition, at the end, the density current head was modeled as linear and nonlinear regression.

Declining the quality and quantity of water resources in recent years has threatened food security, health and the development of communities, especially in arid and semi-arid areas. The purpose of this study is to investigate the quantitative and qualitative conditions of surface and groundwater resources in the drinking and irrigation sections of Zayandeh Rood basin that faces political and social sensitivities in addition to the dangers of the arid regions of the Central Plateau of Iran. In this paper, using the integrated groundwater footprint (iGF) and for the first time integrated surface water footprint (iSF) indices as well as applying the Schoeller and Wilcox standards for checking quality of drinking and agricultural water, respectively, water resources status has been evaluated in 2006 and 2016. The average of integrated groundwater management index in Zayandehrud basin for drinking and irrigation purposes in 2006 is equal to 8.9 and 1.3, respectively and these values have decreased to 7.3 and 1.1 in 2016. Furthermore, in 2006 the average of integrated index of surface water footprint for whole basin in drinking and irrigation water were obtained 3.8 and 2.4, respectively and these values have improved to 3.3 and 2 in 2016. However, the results of these two years show a relative improvement in water resources in the Zayandeh Rood Basin, but they are far from acceptable conditions, especially in the drinking water sector, which requires serious attention of decision makers for developing of dynamic plans for sustainable development of this basin.

Climate change on a large scale increases changes in boundary indicators. Since these indicators play an important role in the occurrence of droughts, floods and other climate disasters, it is necessary to study their behavior in the context of climate change. In the present study, 24-hour precipitation data of 11 Synoptic Stations during statistical periods (1987-2017) have been used. Climate change indicators (ETCCDI) have been used to extract trends using R-ClimDex software Also to check the linear trend of the test TFPW-MN and in order to zoning the precipitation conditions, PCA method has been used in the form of Minitab statistical software. The results of m-Kendall test show that precipitation indicators in all studied stations have a decreasing and negative trend and homogeneous slope. After forming the variable correlation correlation matrix, the principal components were reduced to 11 components using the analysis method and rotated using a varimax rotation. By examining the results of PCA algorithm, four climatic types were identified. The fourth climatic type (Shiraz station) has the most effective role in creating climatic conditions in precipitation with a relatively 85% specific variance of the total changes. As a result, it can be said that the overall structure of precipitation in the study area is affected by latitude, the existence of rough configuration and air masses. And by changing any of these factors, the rainfall will change.

Due to the limited water resources for agricultural production in Iran, increasing water productivity and optimal use of water resources in the agricultural sector is essential. This experiment was conducted to study the effect of irrigation methods and plastic mulches on water productivity and early maturity of Melon culitvar “Garmak”, in Isfahan province. Statistical design was split plot based on RCBD in three replication with distributing three irrigation systems (surface, drip and porous pipe) in main plots, two types of soil covers (black and transparent and without cover as a check) in sub plots. The results showed that in terms of crop yield, there was no significant difference between drip and surface irrigation methods with a yield of 59 and 54 tons per hectare. Crop yield in the porous pipe irrigation method was drastically reduced, while the drip irrigation method reduced the applied water compared to the surface irrigation method by 50 percent and increased the applied water productivity more than 2 times. Drip irrigation had a significant effect on the early maturity of the crop, so that the early yield increased by 28 percent. The effect of different plastic mulches on yield, yield components and crop maturity was significant at 5 percent probability level. The interaction effects of irrigation method and mulching on yield and early maturity also showed a significant increase in both transparent and black mulch. Crop yield and yield of early maturity increased in both transparent and black mulch. The highest yield and early maturity of the crop were obtained in drip irrigation with transparent mulch, 66500 and 22603 kg / ha respectively, which increased by 42 and 133 percent, respectively, compared to surface irrigation without mulch. Plastic mulches were effective in reducing soil evaporation, conserving moisture, controlling soil temperature and reducing weed growth. For optimal use of water resources, the use of drip irrigation in combination with plastic mulch in Melon crops is recommended as a solution to reduce water consumption and achieve a marketable product.

The operation of reservoir dams has so far been done with emphasis on the goals of meeting water needs and controlling flood energy and improving environmental conditions, and less attention has been paid to the issue of sediment removal from the reservoir of the dam. In this study, a semi-cylindrical structure in front of the lower discharge was tested to determine a method to improve sediment discharge. The experiments were performed by constructing 16 physical models with different lengths and widths of gaps in four water heights, three half-cylinder diameters and a total of 208 experiments. The results of the experiments showed that by placing a semi-cylindrical structure in front of the lower discharge, the volume of leaching sediment increases. In other words, a pair of rotating vortices is created inside the semi-cylindrical structure on both sides of the central axis of the valve, in which case the installation of a half-cylinder with different diameters increases the volume and length of scale washing compared to the model without a cylinder. . So that by increasing the height of the gap four times, the volume and length of sedimentation increase by 101.3 and 27.2 percent. The results of this study showed that the installation of semi-cylinders with diameters of 12.7, 15.2 and 19.2 on average will result in an average of 587, 732 and 829 percent increase in sediment volume compared to the model without cylinders. Also, installing semi-cylinders with diameters of 12.7, 15.2 and 19.2 on average will increase the length of scouring by 94, 106 and 111 percent, respectively, compared to the model without cylinders

The use of drip irrigation systems in agriculture is associated with several problems. Clogging of filters and drippers and, thus reducing the uniformity of water distribution needs to be addressed. Proper design and construction of the filter can be one of these suitable solutions to the problem. In this study, a physical model including a filter tank with a height of one meter and a diameter of 60 cm for placing sand with different sand size and thickness of different layers along with a pump, a power of 0.5 horsepower to provide pressure, two pressure gauges were used to determine the hydraulic load losses in the sand filter and, raw water of specified quality. 9 treatments of granulation and layering and, two treatments of water quality containing the amount of suspended solids were used. The aggregation of these treatments was 1.77, 0.89, and 0.45 mm, respectively. The results showed that the load loss changes in the granulation range of 0.89 – 1.77 mm is less than the range of 0.45–0.89 mm. the load loss increased with the smaller particle size of sand. The results showed that the percentage change of filtration in the granulation range of 1.77 - 0.89 is less than the range of 0.45 - 0.89 mm and with increasing the height of the middle layer, the percentage of filtration of filters increased. The results showed that the percentage change of filtration in the granulation range of 0.89 – 1.77 mm is less than the range of 0.45 - 0.89 mm. The percentage of filtration increased with increasing the height of the middle layer. But, the changes in the percentage of filtration for changing the height from 12 to 17 cm were more than the changes in the percentage of filtration from 17 to 22 cm. Clay particles, plant debris, insects are water-soluble substances that must be refined by filters for drip irrigation.