مجله مهندسی و مدیریت آبخیز
سال پانزدهم شماره 2 (تابستان 1402)

Gully erosion is a water erosion that has a great contribution to land degradation and is known as one of the most important environmental hazards in the world and especially in Iran. In recent years, machine learning techniques and geographic information systems have been highly effective in determining areas sensitive to gully erosion and have increased accuracy and speed in the evaluation and potential of gully erosion and in determining effective factors on gully erosion has also been effective. The loess lands of Golestan Province are more susceptible to water erosion due to sufficient depth and almost uniform silty graining, excessive use, cultivation on sloping lands, and wrong land management so that all types of erosion can be observed in these areas. The most common type of erosion in these sediments is gully erosion. The studied watershed is faced with the increase of dry and abandoned land, land use change, the presence of surplus livestock in the forests, and also the population increase. Therefore, this area is facing an increase in sensitivity to gully erosion, and areas with the potential for gully erosion should be identified and managed. 

The studied watershed with an area of 222,000 ha and an elevation range of 58 to 2168 m is located in the northeast of Golestan Province. The average rainfall of the area is between 224 and 736 mm. In this research, first, the location of the gullies was obtained from the General Directorate of Natural Resources and Watershed Management of Golestan Province. Then, from the total of 1127 gullies position, 70% were randomly classified as training data and 30% as validation data. To determine the effective variables in gully erosion sensitivity, 14 factors were identified and in the next step, the collinearity test between the variables was performed using SPSS software. By using the indices of tolerance coefficient and variance inflation factor, if there is collinearity between the variables, they were removed from the modeling process. Considering the importance of the DEM map and its application in the preparation of various factors of the current research, a DEM was prepared using ALOS satellite images. The layers of slope and aspect are prepared by using a digital elevation model and slope and aspect functions respectively. Slope length index in SAGA GIS software, layers of distance from stream based on the map of stream, and distance from roads based on existing roads, and using the Euclidean distance function in the ArcGIS software was prepared. Stream density and road density layers were obtained based on the map of existing streams and roads in the region and using the line density function in ArcGIS. The lithology layer was extracted from the geological map of the region and the land use layer was obtained from the General Directorate of Natural Resources and Watershed Management of Golestan province. The rainfall map has been prepared using the information from 35 rain gauge stations. First, the average rainfall of 26 years was calculated for each station, and then rainfall zoning was done using the global Kriging Method (due to the lowest RMSE) in ArcGIS. The TPI layer was prepared using the DEM and using the SAGA GIS software. The HAND index is a topographic-hydrological index of the DEM of the nearest drain, representing the hydrological behavior of the watershed. To evaluate the models, the relative performance detection curve (ROC) was used for the predictive power of the models.  

The results showed that there is no co-linearity between the variables and therefore all the variables were used in the modeling process. The relationship between gully erosion and elevation showed that lower elevations are more sensitive than higher elevations and more susceptible to gully erosion near waterways. The results showed that with the increase in drainage density, the sensitivity of gully erosion increases, and the possibility of gully erosion increases. The results showed that the old barracks, shale, and loess have the greatest impact on the sensitivity of gully erosion. The results show a decrease in the sensitivity of gully erosion with a decrease in the HAND index. This result indicates that in the areas where the level of saturation in the watershed level increases, the possibility and sensitivity of gully erosion increases. The results showed that among the types of land use, canals, poor pastures, and agricultural land use have the highest sensitivity to gully erosion. This is even though the forest areas have the lowest sensitivity to this erosion. The results showed that in the rainfall range of 220 to 420 mm, the possibility of gully erosion has increased, and the range of 420 to 500 mm has shown the highest level of sensitivity, and with the increase of rainfall from 500 mm to above, a reduction in the sensitivity of gully erosion has been encountered. One of the reasons for reducing the sensitivity of gully erosion in higher rainfalls is the increase in vegetation and the creation of suitable conditions for landslides. The results showed that the depth of the valley up to 235 meters have increased the probability of gully erosion, and from 235 meters above, it has decreased the probability of erosion. The results showed that the sensitivity of gully erosion increases near roads, and this case shows the effects of road construction and the aggravation of conditions for gully erosion. 

This research was conducted to determine the effective factors on gully erosion and zone its spatial distribution in the northeast of Golestan Province. In this study, by considering 14 important factors and using RF, ANN, and CART models, a sensitivity map of gully erosion was prepared. Because the identification of gully erosion-sensitive areas based on traditional methods and expert opinions do not have acceptable accuracy, it is necessary to use modern machine learning methods. The results showed that the factors of distance from the road and land use are the most important factors affecting the sensitivity of gully erosion, which requires land use management as human activities. The ROC curve showed that the accuracy of the models in estimating areas with gully erosion sensitivity was excellent in the test stage (ANN) and very good in the test and validation stage (RF and CART), which means the excellent performance of the models.

Segzai plain, 40 kilometers from Isfahan city, with an area of about 40,000 ha, is considered a serious threat to this historical city. This plain, which until a few decades ago was a relatively prosperous reed and meadow, has now become a huge danger in terms of nature destruction and environmental pollution. Two natural and human factors play a role in the desertification of this region. Among the natural factors are low rainfall, high evaporation, the presence of limiting layers in the soil and strong winds and from human factors, excessive grazing and overgrazing of livestock as well as bush-cutting, rapid population growth and excessive exploitation of existing resources decline Underground water and most importantly, exploitation of surface mines, especially gypsum mines, can be mentioned. The main goal of this research was to evaluate the effectiveness of the SEBAL model for estimating the actual evaporation and transpiration of the Segazi Plain, considering the arid and semi-arid location of the region using the landsat 8 image. 

To do this research, first, landsat 8 images were processed. Extraction of required information from satellite images in this research was done during three main stages, i.e. pre-processing, processing and post-processing. In other words, in the pre-processing stage, after performing atmospheric, geometric and other necessary corrections, the image was referred to the ground. In the area of data processing, different highlighting methods and statistical analyzes and remote sensing were done in order to achieve the information layers of the plan. In order to evaluate the results in the image processing stage, the post-processing of the data based on various analyzes was used to evaluate the reliable layers in terms of accuracy and precision. After that, the SEBAL algorithm was implemented.  first the amount of net radiation (Rn) was calculated according to the temperature of the earth's surface and vegetation and the amount of energy reaching the earth, then the heat flux of the soil (G) was obtained to determine the amount of transfer capability The heat into the soil was determined, then it was determined to calculate the amount of sensible heat flux (H), which determines the loss of energy from the soil to space. Finally, after determining the sensible heat flux, evaporation and transpiration were calculated. The SEBAL algorithm calculates the energy balance equation in order to calculate the actual evaporation and transpiration of the plant. 

Surface albedo parameters (the highest and lowest weighted values are around 0.85 and 0.16), soil surface temperature (the highest and lowest weighted values are around 326 and 299 degrees Kelvin), NDVI vegetation index (the highest and lowest weight values related to areas with good vegetation close to +1 and related to water and water bodies close to -1), the amount of net energy reaching the surface of the earth (the highest and lowest weight values are about 703 and 210 Wm-2, soil heat flux (the highest and lowest weight values are about 130 and 35 Wm-2), sensible heat flux (the highest and lowest weight values are about 323 and 23 Wm-2 , momentary evaporation and transpiration (the highest and lowest weight values are about 0.842 and 0.225 mm) and daily transpiration evaporation (the highest and lowest weight values are about 20.2 and 5.4 mm) are among the most important effective parameters in this Sabal algorithm which were investigated in this research. Changes in actual transpiration evaporation (the highest weight values about 0.85 mm and the lowest weight values about 0.16 mm). The obtained results showed that the SEBAL model has well predicted evaporation and transpiration in areas that have vegetation, mostly agriculture and gardens, so that the amount of water loss through evaporation has been predicted close to the values found in the eastern synoptic station of Isfahan (airport Shahid Beheshti) is registered. 

The amount of error obtained in SEBAL calculation was 0.1%. The amount of real momentary evaporation and transpiration has been calculated in the range between 0.22 and 0.84 mm, according to the weather conditions of the region and the temperature of the air near the surface (27 to 50 degrees) and the amount of evaporation and transpiration recorded by the Penman-Monteith equation (30.0 mm in the east of Isfahan synoptic station), this value is in a reasonable range. Comparing the outputs of Sabal model with the amount of evaporation and transpiration obtained in the same station, which shows the root mean square error (RMSE) value of 0.1, indicates the suitability of this algorithm in calculating evaporation and transpiration in Segazi region. Considering the growing need of the country to prevent the wastage or excess consumption of water in the agricultural sector, either through changing the cultivation pattern or changing the irrigation methods, the application of the developed tool of the Sabal algorithm in this research can provide valuable information to the experts and managers of the water sector put agriculture. The results obtained from this implementation of this research showed that remote sensing has a good potential for estimating actual evapotranspiration (ETA) by having different algorithms such as SEBAL algorithm and minimum ground information.

Fire, as one of the important and common occurrences in all forest and rangeland ecosystems, in addition to affecting the physical characteristics of the soil, generally causes the soil to become hydrophobic and thus reduce water permeability. The set of these changes can affect the stability of soil aggregates and splash erosion as the first stage of soil erosion. Therefore, investigating the effect of fire on soil erosion can lead to a better understanding of post-fire processes in ecosystems. Accordingly, the present study was planned with the aim of investigating the effect of fire on soil aggregates stability and splash erosion components in laboratory conditions on the rangeland soil in Kajur watershed located in the north of Iran. 

The corresponding experiments were done in three control plots and 12 plots covered with dry residues of rangeland species with four densities (250, 500, 750 and 1000 g m-2) based on the mass of plant residue per unit area and cpnsequently with four different fire intensities in three replications. Then, splash cups were placed on the soil surface and rainfall with an intensity of 60 mm h-1 and a duration of 30 minutes was simulated, and the splash erosion components including upward, downward, total and net splash were measured. The soil aggregate stability was also investigated by comparing the mean weighted diameter of the soil aggregates before and after the rainfall simulation in all plots. 

The results showed that the effect of fire treatment on reducing total and net splash variables and increasing soil aggregate stability was significant at 95% and 99% confidence levels, respectively. With the increase in the intensity of the fire treatment, in general, the trend of changes in soil aggregate stability and splash components was increasing and decreasing, respectively. The fire treatment with an intensity of 250 g m-2 of the dry residues of the rangeland species reduced total and net splash by 35 and 44%, respectively, while the treatment of fire with the intensities of 500, 750 and 1000 g m-2 of the dry residues of the rangeland species reduced total and net splash more than 95%. Although the soil aggregate stability increased significantly with increasing the intensity of the fire treatment, the reduction of the total and net splash in the fire treatments with an amount of >500 g m-2 of the dry residues of the rangeland species was no longer significant. The significant participation of small particles of the soil surface without aggregation in the splash changed the intensity of the effect of fire treatment. The percentage of reduction of total and net splash due to the fire treatment with different intensities was not the same, which shows that the splash in the upstream and downstream directions did not decrease in the same proportion. The soil aggregate diameter from the control treatment to fire treatments with low to high intensities had a decreasing trend, generally. 

According to the results of the present research and the importance and recognition of the effect of fire on soil stability, the effect of fire treatment on soil stability should be done in soils with different textures and organic matter contents, especially considering the fire treatment with lower and higher intensities and shorter and longer dutations. It is suggested that the use of suitable tools to measure soil surface temperature during fire treatments should also be considered in future studies.

Rivers are highly variable systems and one of the most important water ecosystems that play an important role in the life of humans and other living beings and are easily affected by pollution. (Maanan et al., 2015). The concentration of heavy metals in sediments is generally several times that of water bodies, and heavy metals are not destroyed and decomposed during natural processes, therefore, heavy metals can be stored in sediments and remain there for a long time. For this reason, surface sediments are one of the main reservoirs of heavy metals and other pollutants (Islam et al., 2016). The Karoun River is not immune from these pollutions and many wastes from metal, petrochemical and oil, cellulose and food industries, domestic and hospital sewage and agriculture are discharged into this water environment. On the other hand, this river supplies water for these industries and is a source of drinking water for cities such as Ahvaz, Khorramshahr and Abadan. The fishes of this great river are one of the main sources of nutrition for the people of the region, as a result of the presence of pollutants, especially potentially fertilizing elements in Karoun, it can cause pollution of sediment, water and food and affect the life cycle of this great river. damage (Rastmanesh et al. 2015). Considering the quantitative extent and diversity of human activities in the Khuzestan plain and the entry of all kinds of effluents and sewage into the Karoun River, investigating the pollution, pollutants and risk levels is an inevitable necessity. Therefore, this research aims to determine the level of enrichment of elements, to determine the ecological risk and dangerousness of pollution in comparison with the quality standards of sediments in the Karoun river in the Weis basin to the beginning of Ahvaz city using geochemical data and statistical analysis. It was done by XLSTAT2018 software. 

In order to evaluate the pollution of the sediments of the Karoun River bed, 22 samples were taken with a boat from a depth of 0-10 cm and based on common methods in sedimentary geology Tucker (1988) and Arzani (1997) of sediments was harvested. Then, the samples were prepared in the water and soil laboratory of the Soil Conservation and Watershed Research Institute for the granulation test and determination of the concentration of toxic metal elements. In order to investigate the state of sediment pollution, the obtained concentrations have been compared with the standard values of ISQGs, severe effect level (SEL), probable effect level (PEL) and global base values. 

According to the results obtained from the grading, the sediments of the river bed in most of the stations have a granular texture and are of the type of mud, silty sand and sandy mud. These sediments have an average of 0.62% organic matter in terms of organic matter. The results of the pollution level also showed that the concentration of toxic elements As, Cr and Ni have values beyond the standard values of ISQGs and PEL. Based on the comparison between sediment quality criteria and standards, Karun River in the studied area has clean sediments from the point of view of Cd and Pb elements. The results of calculation of enrichment factor showed that Zn element has moderate to significant enrichment. The enrichment of Cu, Ni and Cr was in the range of moderate pollution. The semi-metal As is in the range of low to medium enrichment and the two elements Cd and Pb have low enrichment. The average enrichment of elements is Zn>Ni>Cu>Cr>As>Pb>Cd. Finally, the results obtained from the risk index showed that the values of the risk index for all samples are in the low risk range (RI<150). The statistical analysis of the samples showed that there is a significant positive relationship between Cr, Ni, Cu and AS with clay. So clay particles are the main carriers of Cr, Ni, Cu and AS elements. A high correlation coefficient between elements indicates a common source, mutual dependence, and the same behavior during transportation. 

The current research leads to sufficient understanding of the geochemical situation and any change from natural conditions and revealing the local and thematic enrichment of pollution levels for aquatic animals and users, especially in the field of agriculture and food cycle in the Karun River in the Vays basin to the city of Ahvaz. has been The results of the enrichment factor showed low to high pollution for selected elements. The potential ecological risk values of all selected elements except As in sample 21 are in the low risk range, and AS in sample number 21  is in the medium risk range . The risk index values for all samples are in the low risk range . Based on the comparison of sediment quality criteria with the standards, Karoun River has clean sediments from the point of view of Cd and Pb elements in the studied period. So that 100 percent of the samples have a concentration lower than ISQG. Cr with 27% and Ni with 100% has a concentration beyond the PEL pollution level and all the values obtained for Cr and Ni elements have a concentration beyond the minimum concentration of the ISQG pollution level. In this way, there is a possibility of poisoning for aquatic animals and water exploitation by the toxic elements Ni and Cr. Comparing the concentration of elements with the standards showed that in stations number seven (subordinate to Mahi Shiban), 21 (east coast of KianPars) and 10 (Kouresh sewage), Cr and Ni elements have concentrations beyond the PEL pollution level and more As. It is from the minimum level of ISQG and the most polluted stations are in the study period. So, the maximum enrichment of Cr and As has also happened in station number seven. Element clustering analysis showed that organic materials are the main carriers of Cu and Zn elements and clay particles are the main carriers of Ni and Cr elements. Also, in the case of Cu and As elements, clay particles play the main role. But the toxic metal Pb has not shown any significant relationship with other elements as well as organic materials and clay particles. So Pb element has a different origin than Cu, Zn, Cr, Ni and As elements. The results of principal component analysis, while confirming the correlation coefficient and cluster analysis, showed that Cu, Zn, Cr, Ni, and As are of anthropogenic origin, and Pb and Cd are of terrestrial origin. This study has an important contribution in determining the origin, pollution and ecological risk of potential fertilizing elements and can help in identifying pollutant sources and pollutant control.

Today, the estimation of the rainfall resulting from rainfall, especially in small basins with no statistics, is one of the main activities among hydrologists, and the estimation of the volume of runoff resulting from rainfall and the application of surface water collection and containment methods, both in terms of water supply And it is very important in terms of flood prevention. In this research, by using the simulation of the conversion of rainfall to floods in a long statistical period of about 20 years between January 23, 2000 and September 23, 2021 in the Astana-Kochsafhan catchment area with HEC-HMS software, one of the main objectives of the selection effect The type of flow conversion hydrographs was checked on the amount of calculation error of the closed boundary flood. The main goal of this research was to investigate the importance of the dimensionless Muskingum coefficients in developing a flood distribution model in a computer simulator. 

For do this research, two types of models were used in extracting the flow hydrograph. The first model continued by using the integration of the general set of sub-basins until the stage where only 5 general sub-basins or 4 sub-basins in the upstream of the catchment area leading to the outlet of the range continued. The process of removing the sub-basins was done by combining the area and other physiographic parameters in the geographic information system environment and using the HEC_GeoHMS extension. 

In addition to the principle of trending, by analyzing the results, it was found that each of the surface current conversion methods under known and more widely used titles have limitations, weaknesses and strengths that can be The title of local regressions was also considered for this transformation, the SCS method as the most well-known method, due to its lower limitation in models with local conventional scale in the limits of third-order watersheds, showed that the error of the obtained data It has been less than other cases. This amount of error was predictable in itself. Clark's method, which has a more structured approach, like Schneider's calculation method, calculates the error in its general form, as well as in the maximum values, moment of occurrence, volume, etc. slow In particular, Schneider's method is designed for large domains in its default. In this study, unlike the SCS method, in which the Nash function error number is 0.540 and the RMSE is 0.7, as well as the deviation percentage is 28.01, for the Clark method, the Nash function is 533. 0 and RMSE is 0.7 and the deviation percentage is 29.71. This calculation also confirms from the point of view of error measurement that one of the best criteria for observing the difference cannot be RMSE. In the model The detailed analysis of the trending effect, the error of 0.537 in the Nash function is very close to the figure calculated in the similar case (initial aggregated model). However, only this error measurement should not lead to the opinion that the creation of more detailed models cannot improve or destroy the structure of its numerical code. Because although the differences in measurement errors can be ignored in a certain way, the total amount of flow in the aggregated model was equal to 19672395 cubic meters. While the same parameter in the partial model has a difference of 277655 cubic meters. 

In general, separation of basic discharge with advanced methods such as WHAT cannot necessarily help to increase the correlation between observational data in a continuous model. On the other hand, calculating the discharges that leave the hydrographic network under the heading of deviation from the hydrographic network in the process of flood flows is the basic condition for reducing the model error, regardless of the type of hydrograph selected in the model.

Income-generating industrial tourism is economically viable, with social and cultural exchange, and at the same time contains the least environmental pollution. Geotourism was first used in the early 1990s to study a special place containing obvious geological and geomorphological phenomena. Today, the development of tourism around the world has attracted a lot of attention because tourism has become an industry that brings many benefits to both the host and the visitor. This industry has become the main source of income, employment, private sector growth and infrastructure development in many countries. The purpose of this study is to investigate the capabilities and capabilities of geotourism in Khatirkuh region located in Savadkuh city of Mazandaran province using the combined SWOT-ANP and QSPM analysis. 

In terms of the work steps, this research is descriptive-analytical. The method of data collection was library and survey type field studies (interviews and questionnaires) and the theoretical framework was also done using documentary method. In order to carry out the research, a questionnaire containing 83 questions was divided into four parts: economic, social, environmental and ecological and the ability of geotourism, and some questions related to suggestions and solutions are given at the end of the questionnaire. The designed questionnaire, after its reliability and validity test, was given to 71 local people, employees, experts and students, and each of the questions in the questionnaire were designed as four options based on a Likert scale. Then, using SWOT model, the strengths, weaknesses, threats and opportunities of the region in the field of geotourism were identified and prioritized and prioritized using the network analysis process method. Finally, geotourism development strategies were identified using SWOT-ANP. 

The results showed that the total weighted scores of strengths (S) and weaknesses (W) were 2.881 and 2.549, respectively, and the total weighted scores of opportunities (O) and threats (T) were 2.922 and 2.39, respectively. Given that the total SO scores are higher than the WT, an appropriate strategy for geotourism development planning in the region would be an aggressive strategy. Also, based on the results of quantitative strategic planning method (QSPM), the prioritization of these strategies with total points of 29.283, 28.350, 27.744, 26.877 and 26.534 respectively include ST6, SO1, SO7, WO2 and WO1 strategies. Financial resources for developing the region's tourism infrastructure, investing in infrastructure, creating new jobs for indigenous peoples, investing well in cultural sectors, and educating indigenous peoples to connect with tourists were identified more than other strategies. 

Considering the priority of the proposed strategies for the region, it can be said that for the sustainable development of geotourism, incentives should be considered for the private sector of Khatirkoh region, because private investors are looking for more income by entering this industry, and this is their issue. makes it necessary to provide appropriate services. Unfortunately, there is not much incentive for the participation of the private sector in the tourism industry, especially in the field of geotourism in Iran and naturally in the Khatir-Kuh region. If the problems caused by not handing over to the private sector and infrastructure facilities are solved, we will witness a more sustainable development in the region.

Soil is one of the most important natural resources of any country, which plays a key role in food security, self-sufficiency in food production, national economy, and sustainable agriculture. Soil erosion is one of the most obvious factors of soil loss, and rain erosion is one of the most important forms of erosion. Therefore, the knowledge of the processes governing soil erosion and sediment transport is very important in water and soil resources management, as well as, the development of soil erosion models to achieve sustainable development is of great importance. Previous research has shown that rainfall patterns are one of the factors influencing rain erosion. Vegetation also reduces soil erosion by protecting the soil against the effects of raindrops and runoff. Rain erosion is especially important in arid and semi-arid areas due to the lack of vegetation and low initial soil moisture. This research was conducted, regarding the effect of rainfall patterns on rain erosion, by investigating the rainfall pattern and vegetation changes over 25 years in Ebrahim Abad and Royan watersheds situated in Semnan City. 

First, the physical characteristics of the watersheds were obtained; using ArcGIS software, and the precipitation information was extracted from the rain gauge sheets with an accuracy of 10 minutes. To compare the rainfall for different amounts of precipitation, the dimensionless cumulative rainfall curve of each event was obtained. The time of each rainfall was divided into 10 parts and the percentage of rainfall was determined for each part. The rainfall curve was divided into 4 quartiles (1st, 2nd, 3rd, and 4th quartiles) depending on the occurrence of the maximum precipitation. According to the information on the sediment layers in check dams located at the outlet of each watershed and the precipitation data, the storm-related to each sediment layer was determined and the effect of the storm pattern on the sediment pattern was investigated. To check the similarity of precipitation and sedimentation patterns in check dams, the average difference in precipitation and sedimentation in each time step and standard deviation changes were used. Considering the dynamic changes of vegetation compared to other characteristics of the watershed, remote sensing data were used to investigate the changes in vegetation and its area. Due to the effective performance and high accuracy of NDVI index and landsat satellite images in dry areas, Google Earth Engine system was used to estimate vegetation cover, manage and recall the satellite images. Then, the influence of watershed characteristics such as slope, area, soil type, shape factor, and vegetation cover on watershed sedimentation was investigated. 

The average similarities in precipitation and sediment pattern in Ebrahim Abad and Royan watersheds were 48.2 and 46.1%, respectively. Also, the percentage of coarse-grained sediments augments by increasing the precipitation quarter number, during each storm event, which shows the important role of the rainfall pattern on the sedimentation pattern in each watershed. The average monthly vegetation cover (obtained from Landsat images) in Ebrahim Abad and Royan watersheds during the mentioned period was 5.15 and 4.99%, respectively, which is less estimated than reported by previous research. In this research, a threshold limit of 0.1 has been used for the NDVI index, in which very weak vegetation has been omitted.

In both watersheds, in more than 51% of cases, by increasing vegetation cover in each storm event, the thickness of the corresponding sediment layer augments, which shows the effect of vegetation cover on the erosion and sedimentation of the watersheds.

Proper watershed management is based on ecological principles, and understanding the ecological process is the main prerequisite for natural resource planning. The watersheds adjacent to the Oman Sea and the Persian Gulf have special conditions compared to other watersheds in the country, such that these watersheds have many salt domes. These geomorphological facies affect the quality of underground water in the areas and require special management techniques. Among the ecological factors, soil is one of the factors that play an important and influential role in the distribution and density of vegetation. The strong correlation and close relationship between vegetation and soil are such that a change in the status of each will have a very strong impact on other ecosystem functions. The present study was conducted to investigate the changes in plant communities and the role of soil factors on these communities in these Gulf and Omani vegetation areas in Bastak city of Hormozgan. 

For this purpose, after determining the desired area, using Google Earth satellite images and ground control, typing was performed and then sampling was done in each type on three transects of 1000 meters with a plot of 4 square meters with a suitable distance. In each plot, canopy percentage, density, height, and two diameters perpendicular to each other of dominant plants were measured. To study the soil, 9 profiles were dug in each type and sampled from two depths of 0 to 45 and 45 to 90 cm and transferred to the laboratory. Statistical analysis was performed by SPSS software and a comparison of means by Duncan method in a randomized complete block design. 

The results show that during the 20 years of 1379-1399, all land uses have undergone drastic changes. In this period, pastures have decreased by 18.32%, of which 83.50% belong to pastures, 9.85% to saline and barren lands, 0.70% to urban-man-made areas, and 5.95% to agricultural lands. The results of the correlation coefficient analysis indicate that the vegetation parameter was electrically correlated with the amount of sodium at 95% statistical level. The height of plant species is related to the percentage of saturated moisture and the percentage of silt in the first and second depths. Showed a negative correlation with soil acidity at both depths with a negative approach at 95% level. 

Soil salinization and its development in dry and semi-arid fragile watersheds is one of the environmental hazards that has received attention in recent years. Faramarzan city of Bastak is one of the areas that have arid and semi-arid environmental conditions and one of the environmental hazards of this watershed is salinization and salinization of lands. In summary, it can be stated that the trans-border area of Bastak is limited by the salt marshlands of Hormozgan in the high areas with salt domes and in the lower areas with the salty river. The type of plant species in the plant types in this salt marsh was different according to the salinity center, and this difference is the result of the soil charact.

Dust event is one of the natural events that occur widely in the world, especially in dry areas. One of the main and effective factors in the occurrence of this phenomenon is the geographical location and climatic conditions of the regions affected by this phenomenon. The purpose of this research is to analyze the cause-and-effect relationships of dust events in Hendijan region with the approach of the Driver-Pressure-Situation-Effect-Response (DPSIR) framework. 

The DPSIR process is an analysis based on the "cause-disability" relationship of factors for policy-making and management planning. The DPSIR framework is a systems thinking framework that assumes cause-and-effect relationships between environmental and socio-economic systems. This conceptual framework uses a cycle of causes and results for the proper integration of basic economic, social and environmental data and information, specifies the relationship between environmental processes and human factors, and also leads to an understanding of the relationship between policy levels and environmental studies. The trend of each component of DPSIR was also evaluated by applying quantitative criteria for the time period of 2007-2019. 

The results of the research showed that the total index of all DPSIR components has an upward trend for the studied period. The slope of the trend related to D, P, S, I and R components was equal to 0.06, 0.03, 0.02, 0.05 and 0.02, respectively. Although some responses were made to reduce the influence of others. The components of DPSIR have been adopted to improve the dust situation, but the research results and the process of changes showed that they were not sufficient and integrated. In this research, a variety of answers related to the components of the driving force, pressure, situation, and effects were identified. The results showed that dust concentration and dusty days in the region increased during the study period and more attention was paid to reactive responses and less focus on preventive responses. Also, paying attention to the response of increasing the efficiency of irrigation due to the high correlation between the state of dust concentration and pressure factors such as the amount of rainfall, soil moisture, and exploitation of water resources in the research area, special attention to the development of water extraction systems as one of the most important responses. Management issues due to the existence of negative and high correlation with the dust situation during the years of research, adequate and sustainable supply of water resources by reducing and minimizing the diversion dams downstream of the Kowsar and Ask dams due to the increase in dust concentration with the increase of flood diversion operations and construction Reservoir and diversion dams since 2009, Considering the water rights of wetlands in the region with the aim of preventing wetlands from drying up and creating a dust center, especially in the west of Hendijan city, and carefully choosing the appropriate plant species, as well as carrying out desertification operations (planting saplings, mulching, building windbreaks). With the ecological conditions of the region, due to the negative correlation between the desertification operation and the reduction of dust concentration since 2014, it can help to improve the dust situation in the research area. 

In this regard, it is recommended to respond to driving forces (D) and pressures (P) so that while improving the conditions and adverse effects caused by it, the drivers and pressures that create the current situation can also be controlled. Based on this, the incomplete implementation of the answers is another reason for not achieving management goals and making the situation and the number of dusty days more unfavorable. It is also suggested to implement the integrated watershed management program in Hendijan city through the development of a joint water, agriculture, and natural resources program upstream of the watershed in order to clarify the effective measures of the water production, distribution, and consumption chain in the upstream lands.

Investigating the climatic condition over watersheds has a decisive role in water resource management planning. Meanwhile, changes in temperature and precipitation have a great effect on the discharge of rivers, soil erosion, and fluctuations in the level of ground water, and the occurrence of floods. It is very necessary to carry out research related to climate change in order to prepare as much as possible to deal with the harmful costs caused by this change. The review of the studies conducted in Iran also shows that the scale of the study is in most cases at the local level and the study of the mean annual discharge trend and its magnitude has not been studied especially over Iran country. Therefore, the current research was planned with the aim of determining the mean annual discharge trend and magnitude over Iran. 

In the present study, the trend of mean annual discharge in Iran was determined by considering the effect of dams using Mann-Kendall and Sen’s slope methods. First, the statistics of all the hydrometric stations located in the Iran six major drainage watersheds were obtained from Iran Water Resources Management Company. Finally, 139 hydrometric stations with a statistical period of 17 to 65 years were selected in this study. The statistics of these stations were compared with the data available in nearby stations and suspicious values were also controlled. The homogeneity of the data and reconstructing the missing data was carried out using the run test and linear regression through the station with the highest correlation coefficient for each station with incomplete station, respectively. In the next step, non-parametric Mann-Kendall and Sen’s slope estimator tests were carried out within XLSTAT software in order to evaluate the trend and its magnitude analyses. After determining the trend of the study hydrometric stations, the spatial distribution map of the mean annual discharge trend in Iran six major drainage watersheds were prepared within Arc/GIS 10.2 software.  

The results showed that 14 hydrometric stations were affected by the dam. However, in the hydrometric stations without dam, 84, six and 35 hydrometric stations have a decreasing trend (60%), an increasing trend (5%), and no trend at the 95% confidence level, respectively. Examining the trend of the time series of mean annual discharge in each of Iran six major drainage watersheds also showed that 80% of the study stations in the Persian Gulf and Oman Sea watershed have a decreasing trend, while no trend were detected in 20%, 10% and 9% of the total study stations in the Caspian Sea, the Central Plateau, and the Persian Gulf and Oman Sea watersheds, respectively as well as all the stations of the eastern watershed (Hammon). In the meantime, all study hydrometric stations in Urmia Lake and Sarakhs watersheds and 68% of the study hydrometric stations in the Caspian Sea watershed have a decreasing trend. 

The results obtained from this research showed that the decreasing trend was detected in most of the hydrometric stations (84 hydrometric stations). Therefore, the decreasing trend of hydrometric stations in Iran can be related to the decrease in rainfall, increase in temperature and the emergence of excruciating droughts caused by climate changes and also human interference, including the excessive increase in the construction of dams and the change of unprincipled land use. However, one of the limitations of the current research is not taking into account climate changes and land use changes and determining the contribution of each of the mentioned factors in the decreasing and increasing trend of the mentioned stations. The results of the present research can be very useful and important for water planners and politicians in order to manage water resources.