جستجوی مقالات مرتبط با کلیدواژه « رسوب گذاری » در نشریات گروه « محیط زیست »

Estimating the amount of sediment by the river is one of the topics that has been considered by many researchers since the past. Reduction of the dam reservoir capacity because of sediments has different effects on different sections and causes adverse effects on the water rights that were initially agreed upon, which will impose several economic and specific consequences. This study aims to model and estimate the amount of suspended sediment using existing experimental equations and new methods called black box.

The discharge (volumetric flow rate) related to Zayandehrud River in Eskandari station, one of the hydrological measuring stations, has been used to estimate the amount of sediment. For this purpose, water discharge and sediment rate are used as input and output, respectively.

According to the obtained results, it is concluded that the RBF network has better performance due to less error in the test stage, but the MLP network seems to have a better performance considering other parameters and the error in the TRAIN stage.

Finally, after modeling by using neural networks, the Einstein relationship, and the sediment measurement curve, it is inferred that neural networks are more accurate to estimate the amount of sediment.

In order to plan and recognize the destructive condition of the watershed, it is indispensable to know the extent of erosion and sedimentation produced from each basin. In this study, the soil erosion and sediment estimation of the Khorkhoreh basin using Sediment Rating Curves were investigated. By integrating geological and geomorphological layers in GIS and removing polygons under 6 ha, 24 working units and 68 sub-basins were attained. To identify the erosion type through field visits, the Bureau of Land Management (BLM) scoring was carried out in each work unit. Using the sediment curve, the amount of total suspended load in the basin was obtained as 2990 ton/yr. With the calculations performed, the amount of specific sediment yield in the Khorkhoreh basin was found to be 25.3 ton/km2. All types of erosion were seen in the portions of the basin, while most of the basin area belongs to the “sensitive” and “very sensitive” to erosion classes. Examination of erosion types showed that in most of the basin’s working units, all types of erosion such as Sheet erosion, Rill erosion, Gully erosion, Channel erosion, and Stream Bank erosion can be observed.

Corrosion and precipitationare physicochemical processes that reduce the amount of water flow in water transfer pipes and the effective life of water supply facilities, increase the energy consumption for water transfer, and cause some diseases among consumers. The present study was conducted to investigate the corrosion tendency and precipitationalong the Gorganroud River from highlands to the Gorgan Gulf.

In this study, the results of the analysis of 11 physicochemical parameters (Calcium, Magnesium, Sodium, Potassium, Bicarbonate, Sulfate, Chloride, total dissolved solids, electrical conductivity, temperature, and pH) of the Gorganroud River during a period of 10 years were used (2004-2014).First, the annual mean changes in the qualitative parameters of water samples during the statistical period of the studied stations were investigated. Then, triangular diagrams were used to assess the Gorganroud River hydrochemical at the studied stations. Next, changes in water hardness as an important qualitative parameter in the industrial, agricultural, and drinking sectors were investigated along the Gorganroud River. Saturation indices were used to predict and the probability of precipitation or dissolution of some carbonate minerals (such as calcite, dolomite) and evaporites (such as anhydrite, gypsum, and halite) along the Gorganrood River. Then, the trend of changes in Langelier, Ryznar, Puckorius, Larson-Skold corrosion indices, corrosion ratio, and the calcium carbonate precipitation potential of Gorganroud River at four stations was investigated. Next, a one-way ANOVA test was used to investigate the significance level of indices in the studied stations. Finally, the relationship between mineral saturation indices and corrosion indices was investigated.  

Based on the accumulation and distribution pattern of the samples in the triangular diagram, the dominant water type in the Gorganroud River is bicarbonate on the margin of heights, and as it enters the plain and the chloride ion concentration increases, it tends to reach full maturity, the sodium chloride type. Hardness increased along the water movement path. The results of saturation indices showed that the river’s water is supersaturated with carbonate minerals and undersaturated with evaporite minerals. Based on Ryznar, Puckorius and Larson-Skold indices, Gorganroud River water tends to cause corrosion. However, the precipitation rate increased from the margin of highlands to Gorgan Gulf. The results of the calcium carbonate precipitation potential and Langelier Index indicated that Gorganroud River tends to precipitation over the study area. Investigation of the relationship between saturation indices with corrosion indices and calcium carbonate precipitation potential showed linear relationships between qualitative indices and saturation indices. The results of the statistical test showed a significant difference between the calculated indices in the studied stations.  

Although based on the hydrochemical results the main factor controlling water chemistry of the Gorganroud River was the water-rock reaction, factors such as saline water intrusion of Gorgan Gulf in the lower part of the river and inflow of untreated effluents into the river caused rapid hydrochemical evolution of the river and reached the sodium chloride type. Increasing the number of physicochemical parameters along the river path in addition to increasing the water hardness, has reduced corrosion and increased precipitation rate. Statistical results showed a clear linear relationship between saturation indices and corrosion and sequestration indices in water.

Hydro-suction is an appropriate and economical method for dredging deposited sediment at reservoirs. In this study, a physical model was made and some experiments were designed to analyze the ranges of blockage depth in different hydraulic conditions. In the model, 80 tests were conducted using three diameters (d), three water heads (H) and different diving depths of pipe inlet (Z) from the sediment level to the blockage depth. In general, the results indicated that the more increase in the diving depth, the higher hydro-suction efficiency. In some of the experiments, a vortex flow was observed under the pipe inlet. The results indicated that the formed vortex flow have a positive effect on the hydro-suction efficiency. The results associated to the blockage depth approved that hydro-suction systems with larger pipe diameter and more water head have a greater blockage depth (Zb). The Froude number (Fr) analysis indicated that an increase in Fr would cause increment efficiency and blockage depth of hydro-suction system. Subject to a constant pipe diameter, the results revealed that increasing the H/d ratio equal to 66.66 and 133.33%, would enhance the Zb/d ratio equal to 58.89 and 112.22%, respectively.