فهرست مطالب فاطمه بالویی

Reducing the effects of drought and optimal management of water resources is affected by the forecast of regional planners of areas affected by the risk of drought, so the evaluation and study of this phenomenon can be very important. Therefore, this study was conducted to Monitor temporal-spatial changes of meteorological drought and trend analysis of climatic variables in Khuzestan province during the period 2000 to 2020 using the SPEI index and ArcMap, XLSTAT, and RStudio software. Two non-parametric methods including Mann-Kendall and Sen's estimator slope methods were used here to analyze the annual trends of data. After calculating the drought, the effect of this phenomenon on the water area of Horul Azim and Shadgan wetlands in 2000, 2006, 2015, and 2020 was investigated. The results showed that there is a direct relationship between the changes in the wetlands cover and the problem of drought, and with the increase of drought, the water cover of the wetlands decreases and with the increase of drought, the area of water in the wetlands increases. The results also showed that the analysis of the trend of changes resulting from Sen’s slope for precipitation and temperature in the stations varied between -1.87 and 3.38 and 0.016 and 2.25, respectively. The highest slope of changes with increasing rainfall was observed in the western and central regions of the province and the slope of negative changes in rainfall has often occurred in the southern regions. Also, temperature analysis with this test showed that the temperature in all stations with a relatively slow slope in the study period had a positive and increasing trend. It is worth mentioning that the existence of increasing and decreasing trends indicates the existence of climate change, so it is necessary to study this issue and provide solutions to water resources management in times of crisis. The increasing and decreasing trend indicates the existence of climatic changes and fluctuations; Therefore, investigating this issue and providing solutions to manage water resources in times of crisis seems essential.

Airborne particles play an important role in the balance of atmospheric radiation and climate change. The relationship between aerosols and climate systems has received increasing attention as our understanding of these issues increases. A dust storm is a complex process that is influenced by the interactions of atmospheric systems and is basically caused by conditions such as high wind speed, bare soil and dry air.

Aerosol optical depth (AOD) is one of the most important parameters in the field of dust related research. Aerosol optical depth actually refers to the distribution of dust aerosols in the atmosphere. In this research, the dust condition was investigated using the AOD parameter of MODIS product. In order to investigate the relationship between environmental factors, NDVI was used. For each year, based on the total images taken, which is about 24 images per year, the average vegetation cover index was calculated in the Google Earth Engine system as a time series. In this study, among the climatic factors, annual rainfall data from synoptic stations were used to investigate the effect of rainfall on the amount of dust changes in the period from 2013 to 2022. Also, a 90-meter DEM was prepared from the SRTM sensor in order to prepare layers of slope percentage, slope direction and elevation classes.

In the research, firstly, to evaluate the dust situation, the aerosol optical depth product was obtained from the MODIS sensor. In order to highlight and monitor as much as possible, the dust phenomenon of the months of June to September, corresponding to the late spring and summer season of each year, when the majority of dust storms are concentrated in these months, was chosen. After downloading the images, the 9-year statistical period (2013-2022) was considered as the studied statistical period in Khuzestan province. The average optical depth of dust was obtained each year based on the images taken in the same year. The results show that most of the dust was spread in the years 2015, 2016, 2017 and 2018, so that a large part of the province faced the dust phenomenon in these years. The investigation of the dust situation in 2013 and 2014 showed that although most of Khuzestan province is facing a relatively low average AOD, the maximum AOD value is related to classes with values of 0.71 to 1.5 and more than 1.5 located in the southwest. is the province; The maximum value of AOD in these years was 2.82 and considering that AOD is between zero and 5 in the mentioned years, the southern regions have faced a high average dust phenomenon. The purpose of this study was to monitor dust and investigate its relationship with various factors of topography, vegetation and climate. The results of dust relationship with the mentioned factors showed that among all the factors, height and slope direction have the highest correlation (83 percent) and (72 percent) respectively with the phenomenon of dust in the opposite direction, so that an increase in the amount of height causes a decrease in dust and south-facing directions. And smooth areas will have an increase in the amount of this phenomenon. Therefore, by using remote sensing techniques, it is possible to identify dust centers as a valuable tool to combat the expression factor.

Desertification is one of the most obvious ecological and environmental problems in arid and semi-arid regions. n this study, to identify dust spots, changes in the average occurrence of dust storms were obtained using MODIS sensor data from 2013 to 2022, and then its relationship with climatic factors, sun cover with NDVI index, and topography were evaluated. A decrease in the amount of precipitation that can lead to a decrease in soil moisture, vegetation cover and an increase in drought; Also, the changes in land use in recent years are all among the factors that have led to an increase in the phenomenon of dust, especially in Khuzestan province. Examining the influencing factors such as topography, vegetation and climatic factors is of great importance in identifying and prioritizing the control of dust centers, in addition, the MODIS optical depth sensor product can be of great help as a valuable tool for monitoring and managing this event.

Today population growth, inaccurate management practices and land degradation processes have caused many watersheds to be severely degraded, leading to increased runoff and sediment. In this study, the aim of the study was to investigate the effect of land use change on surface water fluctuations in the Doiraj watershed. Landsat satellite imagery was used for three periods of 1995, 2006, and 2015, it was found that the major changes occurred with decreasing forest and rangelang  levels and increasing land barren. For modeling rainfall-runoff, a SWAT computer model was used. Then, using the SWAT_CUP model, The performance of the model was evaluated using statistics, NS, R2, P_FACTOR and R_FACTOR. After calibration and validation, the values of these coefficients were 0.58, 0.60, 0.81, 0.87 for the calibration period and 0.56, 0.57, 0.81 and 89 for the validation period of the model, respectively was obtained. Annual runoff estimation indicated that changes in forest, pasture and wasteland land use from 1995 to 2015 increased the outflow runoff the basin from 3.91 to 5.85 m3 / s.

Changes in land cover and land use effect on natural processes such as soil erosion and sediment production, flooding and soil physical and chemical properties. One of the important impacts of land cover type on processes in watersheds is its role on soil erosion rate. The purpose of this study was to investigate the effect of vegetation changes and conservation factor on soil erosion in Doiraje watershed of Ilam province using GIS and RUSLE model . The results showed that the changes in Landuse/cover  increased the amount of soil loss. Soil conservation scenarios showed that with all factors constant, soil conservation with a correlation coefficient of 0.46% was secondarily important after topography with a correlation coefficient of 0.81% in determining soil erosion. The highest soil erosion under the soil conservation scenario was 2015, with an average of 48.91 ton / ha. Examination of land use / cover change scenarios showed that by keeping all factors constant, soil protection with a correlation coefficient of 0.46% in the second place after topography with a correlation coefficient of 0.81% and vegetation factor in the third degree played an important role in determining the amount of soil erosion. Is. The highest soil loss under the third scenario was in 2015 with an average of 108.94 tons per hectare per year.

Different models have been proposed to describe and predict the hydrology of the watershed which are different in terms of objectives and spatial and temporal scales. In this study, the SWAT model was used to simulate the hydrologic response of the doiraj basin. The main inputs of the model, which include meteorological data, a basinchr('39')s elevational digital model map, a soil map and land use map, are entered into the model. The model was implemented according to the curve number method, then, using the SWAT_CUP model, the performance of the model increased with entering the observation data of the discharge from the basin and performing the calibration steps during the period from 1996 to 2008. And then the validation step from 2009 to 2012 confirmed the modelchr('39')s ability to simulate rainfall-runoff and its use for study purposes. Long-term mean soil moisture in 1996, 2008, and 2013 was 524.24, 337.59, and 468.77 mm, respectively. The study of the simulated water balance components showed that for 1996, despite heavy rainfall, the water balance was almost zero, indicating a loss of water in the basin in the basin, with major evapotranspiration losses. The water balance is positive for 2008 and 2013 because the sum of evapotranspiration, river flow, lateral flow, infiltration and surface runoff are lower than the sum of precipitation.

Today, there are many factors affecting watersheds, consequently changing natural ecosystems succession. The aim of this study was to investigate the effect of drought events on land use changes at Doiraj Watershed of Ilam Province from 1996 to 2015. For this purpose, Landsat satellite images were used for land use change monitoring and Standardized Precipitation Index (SPI) was applied for drought characterization. The results showed that during the two last decades, the forest and rangeland have been continuously destroyed. However, in the first period (1996-2006), land use changes and land degradation have been more intensive than the second period (2006-2015). Generally, in the past twenty years, about a quarter of the forest land and more than half of the rangeland had been destroyed or changed to become other land uses. Drought monitoring results also showed an extremely wet condition in 1996 and normal and near normal conditions for 2006 and 2015. Therefore, we can conclude that in the first period, in addition to human activities, changes in drought condition as a climatic factor could affected  land use change and land degradation.