Background: Soil erosion and sedimentation are among the major problems and environmental challenges in watersheds. The sediment load in rivers causes numerous issues, such as sedimentation in dam reservoirs, changes in river courses due to sedimentation in their beds, reduced water carrying capacity in waterways and water transfer facilities, and changes in water quality for drinking and agriculture. These problems are of great concern to researchers and water resource managers as they can investigate sedimentation, erosion, and potential effects on biological processes. Therefore, it is essential to investigate and evaluate suspended sediment concentrations to determine water quality and hydrological functions. In this regard, the use of accurate, extensive, and cost-effective techniques, such as remote sensing, is invaluable for improving sedimentation estimation and, consequently, water quality assessment. Understanding the spatial relationships between upstream vegetation and sedimentation is crucial for the effective control and optimal management of water resources and soil. The present study aimed to determine the relationship between vegetation cover and suspended sediment concentrations in the Doab Mereg and Gamasiab watersheds. Methods: In this research, the Sentinel-2 satellite data were investigated in the first step. If there were cloudy conditions, dust particles, or other radiometric problems, they were removed from the calculations. Then, factors such as band type (visible and infrared bands), river width (higher than the image pixel - 40 meters at the Doab station and 80 meters at the Polchehr station), separation power, and sensor location (10 and 20 meters) were considered to select the appropriate image pixel for obtaining the spectral reflectance of water. The pixel corresponding to the hydrometric station and its surroundings was selected to extract the spectral reflectance. Then, the suspended sediment concentration statistics of the Doab Mereg station located in the Qarasu River and the Polchehr station located in the Gamasiab River in the five-year period (2016 to 2020) were used simultaneously to investigate the correlation between the spectral reflectance of the Sentinel-2 image bands and sediment concentration. Next, the Normalized Difference Vegetation Index (NDVI) for the two May and June seasons was extracted using Sentinel-2 images. The relationship between vegetation cover and suspended sediment concentration recorded at the station and extracted from the images was estimated separately. Results: The results of the correlation analysis of suspended sediment concentration showed that the best result for the Doab and Polchehr stations belonged to band 4 (R2 = 0.86) and band 5 (R2 = 0.83), respectively. The suspended sediment concentrations varied from 0.17 to 76.45 and 0.44 to 118.86 mg/liter in the Doab Mereg and Polchehr stations, respectively. In the Doab station, the depth of the power state had the highest correlation coefficient between the observational data (recorded in the station) and the data extracted from the images. In the Polchehr station, it had a high correlation coefficient in both polynomial and exponential modes. The best values of the coefficient of determination (R2) of the normalized vegetation cover difference index for the Doab and Polchehr stations were 0.98 and 0.64, respectively. This means that the amount of sediment decreases with an increase in vegetation cover. The average values of the vegetation index for the Mereg watershed (0.35) and the Gamasiab watershed (0.28) show the relatively sparse vegetation in the area. The lowest average values of vegetation cover in the studied season (spring) were respectively equal to 0.11 and 0.21 in the Mereg watershed in June and the Gamasiab watershed at the end of May. The results of the regression test showed a strong and significant relationship between the density of vegetation and the amount of suspended sediment concentration recorded in the hydrometric stations of the two basins. Conclusion: The results showed that six models were extracted for the studied area, which had acceptable and suitable R2 and error values. Among the obtained models, better results were obtained in the single-band model than in the case of using the band ratio. The highest correlations belonged to bands B2, B3, B4, and B5 in the Doab Mereg station, and to B4 and B5 in the Pol Cheher station. The highest R2 values obtained for the two stations were 0.86 and 0.83, respectively, in the exponential model. The results of this study show that Sentinel-2 can be used as a suitable tool to estimate suspended sediment concentrations with acceptable accuracy in small-scale basins and flood conditions, which has been confirmed in a number of similar studies. Sediment rate refers to the positive effect of vegetation on soil protection and the reduction of sediment production and transport within watersheds. In general, the results demonstrate that vegetation has been effective in the quantity and quality of the spatial changes in the sedimentation rate of the basins. In fact, the NDVI vegetation index, as a representative of the vegetation, can be successfully used to create a statistical model of the changes in the sedimentation rate. The revitalization of vegetation should be included in development plans.

In the present study, the Soil and Water Assessment Tool (SWAT 2000) model was tested on both a monthly and yearly basis and applied to the Kordan Watershed, located in Iran. The main objective of the research was to assess the accuracy of the model in sediment-yield and surface water bicarbonate concentration estimation. The attributes of sub-watersheds, tributary channels and the main channel in each sub-watershed were generated using the Digital Elevation Model (DEM) and Geographical Information System (GIS) Arc View SWAT 2000 interface. The model was calibrated and validated for the period from 1990 until 2004. Calibration results revealed that the model predicted monthly and yearly sediment-yield, but not such good results were obtained for the bicarbonate concentration. Therefore, some efforts were made in order to find a solution for SWAT bicarbonate temporal modeling. Around 70 samples of the Kordan River water quality data were used and, upon doing statistical calculations, the best correlation between the average pH–EC of water and the bicarbonate concentration was obtained. The formula shall be tested at several watersheds, and it can also be defined to SWAT in order that the model is able to calculate bicarbonate concentration according to pH and EC of the river water, which are introduced to SWAT by the user as a stream water quality file (SWQ).

Introduction: The coastal environment of Bushehr is supposed to be affected by polycyclic aromatic hydrocarbons (PAHs) and oil pollution. Despite carcinogenic characteristics of PAH compounds to living organisms and human beings, the available information concerning PAHs contamination in Bushehr is not sufficient. This study was carried out to investigate concentration and distribution of PAH compounds based on number of rings in their structure, in the coastal sediment of Bushehr.Material and methods: Samples were collected from five different stations along intertidal zone of the shoreline. The samples were digested; their PAHs contents were extracted and analyzed using High Performance Liquid Chromatograph (HPLC).Results: Results showed that the total PAHs (tPAHs) concentration in stations Rafael, Sheghab, Abshirinkon, Lian and Helyleh were 844.95, 3078.42, 4790.32, 2988.06 and 2430.62 ng g-1 (dw) respectively. A significant difference was observed between tPAHs concentrations in different stations.The maximum tPAHs concentration was measured in station Rafael, while its minimum level was observed in Abshirinkon. Based on the number of the rings in the molecules, the PAHs composition in different stations varied significantly (P<0.05).Conclusion: Compared to previous studies from other locations of the world, PAHs contamination in the Bushehr coastal sediment was evaluated as moderate to severe. The major part of contamination was comprised by High molecular weight PAHs with 5 or 6 rings while 2, 3 and 4 rings compounds had less contribution. Since the adverse and carcinogenic effects of high molecular weight compounds are more severe in aquatic organisms and because its continuous anthropogenic discharges in Bushehr, regular monitoring of PAHs in the area is necessary.

Some contaminants associate with soil particles and, thus, their transport and fate in the environment is determined by the soil erosion processes. Eutrophication, low oxygen levels and high nutrient (nitrogen and phosphorus) concentrations in reservoirs, canals and other water courses, is a common water pollution feature. Phosphorus (P) is one of the major plant nutrients and also the major nutrients controlling eutrophication of surface water. P load pulsed by heavy rainfall may damage the ecological quality of downstream. The present study was conducted in Kojour Watershed located in Mazandaran province. The results showed that P loss varied from 0.26 gr lit-1 to 1860.64 gr lit-1. It also proved that P concentration could not estimated by flow discharge, while sediment concentration can estimate loss of P with determination coefficient and estimation error of 94% and 23%, respectively. The results could facilitate the application of given methods obtained in the present study to other ungauged watersheds with similar conditions and leading to the suitable soil and water management and planning.

The port of Bushehr, located in southwestern Iran and serving as the capital of Bushehr province, has experienced significant economic growth driven by activities such as fishing, the operation of a nuclear power plant, shipbuilding, and exports. Access to the port is facilitated by two critical channels: the outer access channel in the Bushehr Gulf and the inner access channel in Khur-e Soltani. Dredging operations in the basins and access channels are essential for maintaining safe navigational depths, but they incur substantial operational costs. Effective long-term planning necessitates extensive temporal data and high spatial continuity to inform management and infrastructural decisions. This study involved simulating sediment transport in the Bushehr access channel using the numerical MIKE 21 model, with an emphasis on validating the accuracy of the results. The analysis utilized hydrographic data and historical dredging information from the years 1990 to 2000, as well as hydrographic data spanning 1998 to 2011. By examining past dredging activities, we gained insights into sediment deposition patterns across various segments of the channel, which proved beneficial for engineering evaluations and assessing the numerical model’s performance. The modeling results revealed that different sections of the access channel experience varying rates of sediment deposition. Notably, during high tide, the highest sediment transport rates were observed in the Khur-e Soltani and Lashkari areas. Furthermore, the section of the channel upstream of Abbasak Island exhibited a significant potential for sediment transport due to elevated tidal velocities. These findings underscore the necessity for tailored dredging and sediment management strategies. A comparative analysis of the modeling results against hydrographic data and previous dredging information demonstrated good agreement, confirming the model’s accuracy in predicting sedimentation rates.

Over the last years, artificial intelligence models have been widely and successfully applied in many fields. In the present study, the efficiency of adaptive neuro-fuzzy inference system (ANFIS), SVM (Support Vector Machine) and Least Squares Support Vector Machines (LS-SVM) have been investigated to estimate the sediment concentration in four gauging stations, namely Jangaldeh, Nodeh, Arazkoosh, and Gazaghly along the Gorganrood River in Golestan province, Iran. The models were defined based on the five different combinations of the river flow and precipitation using time lags from 0 to 2 previous days. The results showed that the LS-SVM model with simplex search procedure had a better performance than the grid search method. Meanwhile, the results obtained from ANFIS model which estimated sediment concentration in Jangaldeh, Nodeh, Arazkoose and Ghazaghli stations with MEF Error of 5. 3, 13. 4, 4. 8 and 2. 8 percent, respectively, suggested a higher performance than other models. Overall, at all stations except Gazaghly, considering the antecedent flow with two-day time lag as the input data of the model increased the error magnitudes. Furthermore, the rainfall of the same day and one-day time lag could only enhance the efficiency of the model at Arazkooseh station.

Natural disturbances as well as man-made activities may cause an increase in sediment supply to rivers.Rivers naturally react to these changes to reach a new balance between imposed conditions. This accordance always lasted until the new dynamic equilibrium regains. The objective of this experimental study is to show the most remarkable features of the morphological responses of alluvial sand-bed channels reacting to changes in sediment supply. The observed results of this research indicate that for a constant rate of sediment concentration, the increase in flow discharge may be followed by channel section increasing. Also, channel widening trend with flow and sediment supply is steeper than no supply condition while increasing in sediment concentration increases the rate of change of widening. It was concluded that the stable channel width is greater with sediment supply than that of no supply conditions.

The primary method for measuring suspended sediment concentration (SSC) is the gravimetric analysis of water–sediment samples collected using grab or bottle samplers from the sea or rivers at regular or irregular intervals. Although this method is reliable, it requires substantial effort and cost for sampling, transportation to the laboratory, and long processing times for sample analysis. This study aims to introduce an alternative method for estimating SSC based on measuring the water turbidity (WT) of water–sediment samples. A case study was conducted in the coastal waters of the Caspian Sea to determine the Pearson correlation coefficients between these two parameters. In-lab calibration between SSC and WT data using site-specific sampling is essential, as the mean particle size and particle size distribution (PSD) can vary considerably in space and time. Therefore, several water–sediment samples were collected from inside and outside the basins of Amirabad and Anzali ports, and grain-size analyses were performed. Subsequently, sediment–seawater mixtures (50 L) were prepared stepwise at eleven concentrations: 125, 250, 500 mg/L and 1, 2, 3, 4, 5, 6, 7, and 8 g/L. For each concentration, WT was measured using a HATCH 2100N turbidimeter and an auxiliary TSW-20 turbidity sensor. Sieve and hydrometer analyses were conducted, and particle size distribution curves for two water–sediment samples from inside the basins of Amirabad and Anzali ports were plotted. The D10, D30, D50, D60, and D90 statistics were extracted and compared. WT values for the eleven sediment mixtures were measured using the HATCH 2100N turbidimeter. Pearson correlation coefficients between SSC and WT were calculated for linear, second-order polynomial, third-order polynomial, and power regression fittings, and SSC–WT correlation curves were drawn. A step-by-step alternative method for estimating SSC based on WT measurements using a laboratory turbidimeter was designed. Applying this method to the case study yielded Pearson correlation coefficients between SSC and WT for water–sediment samples from Amirabad Port. The proposed approach is suitable for use in a real-time and continuous sediment monitoring network, enabling the integration of WT as a surrogate parameter for SSC in the national sediment monitoring database.

Objective: Zayandehrood habitat has economical and environmental importance in central plateau of Iran and it performs a vital role for habitants, agriculture section and the industries which are located along river bed. So current research has been done to measure the contamination of heavy metals, its changes along the river route and defining the important and effective regions on this contamination. It was defined and stations of sampling along the zayandehrood river route to gain this aim.Methods: The samples were taken from the depth of 30 to 50 cm of the substances which are located in river bed. In each sample, the absorbable thickness and whole metals of Lead, Cadmium, Cobalt, Nickel and Copper were measured. The maximum thickness for all studied elements in this station was observed after Isfahan city (Isfahan-Yazd Highway Bridge). Among these heavy elements, the thickness absorbance amount for lead metal in 6 stations was in toxic amount. The thickness of Cobalt in 5 stations and Copper in one station was in toxic amount. The absorbance amount of lead in Dorche bridge was 2.5 times and in Yazd-Isfahan Highway Bridge was 3.5 times more than the toxic amount.Results: According to the results of this research and according to other researcher’s studies, Cadmium metal which has special importance because of its pollution on the environment has pot and toxicity along the river route, but the studies have been done via other researches in Gavkhooni pond, have registered the toxicity amount of this element. we can conclude that Isfahan city and also the region which is the center of big industrial factories near Nekouabad Dam and Polchalleh, have the most pollutant effects on zayandehrood habitants.