Studying and Monitoring Changes in Horul Azim Wetland Using Landsat 8 Images

Wetlands are one of the most important ecosystems and living areas in the world, one of the most obvious beauty and masterpieces of creation. As an essential part of the global ecosystem, these wetlands have played an important role in preventing or reducing the intensity of floods, feeding underground aquifers, providing a unique habitat for plants and animals, maintaining water quality, agricultural production, fisheries, saving floods, and controlling soil erosion. The current research aims to investigate the changes in water surface and water area as well as the changes in the land cover of Horul Azim Wetland for the statistical period of 2013 to 2022 using Landsat8 satellite images. In this study, maps of water areas and land cover were made using Landsat8 image integration techniques and by applying the AWEI spectral index and maximum likelihood algorithm in ENVI5.3, ArcGIS software. By checking the accuracy of the results of satellite image processing and classification (2013 Kappa coefficient equal to 95% and overall accuracy 96%, year 2022 Kappa coefficient equal to 90% and overall accuracy 92%) It was found that the supervised image classification, the maximum likelihood algorithm for the studied area is close to ground reality and has acceptable accuracy. Also, the maps related to the monitoring of changes in the water area of Horul Azim wetland (AWEI index) showed that the size of the wetland has been decreasing in the studied years, so in 2013 the area of the water area of the wetland was equal to 336 square kilometers. which has decreased to 147 square kilometers in 2022. The results of the classification of images in the studied years also indicate the decrease of water and plant covers and the increase of barren lands and salt marshes in the studied periods. There have been many influential factors, including environmental and human factors, on this process of changes in the studied periods. 

Wetlands are considered one of the most obvious beauties of nature, the most useful and at the same time the most challenging part of nature's ecosystems. These vital and diverse habitats are among life-giving systems that have absolutely no substitute. Recently, it has been estimated that global wetlands occupy about 6.2 to 6.7 percent of the earth's surface. With more than 251 large and small wetlands, Iran is of special importance in Southwest Asia due to its geographical location. Horul Azim Lagoon has changed its area and water level in the past decades due to various reasons. Considering the ecological importance of this wetland for the country, it is necessary to monitor and evaluate the changes in this wetland and study the consequences of these changes. The study of land cover changes has a very long history and coincides with the beginning of human life. Thus, after the formation of societies, the first humans began to change the cover of unused land to suitable land for agriculture and animal husbandry. Considering the importance and necessity of monitoring the change of Horul Azim wetland. We intend to use satellite images by applying the technique of integrating Landsat 8 satellite images during the period from 2013 to 2022. By applying the maximum likelihood classification method and AWEI spectral index, let's investigate the changing process of land cover and water areas of Horul Azim lagoon.

In this research, Landsat 8 multi-temporal satellite images (OLI meter) have been used. In total, 2 images were obtained from the US Geological Survey website and were used in the analysis of the research steps that will be described below. In total, 2 images were obtained from the US Geological Survey website and were used in the analysis of the research steps that will be described below. In total, 2 images were obtained from the US Geological Survey website and were used in the analysis of the research steps that will be described below. Radiometric (atmospheric) corrections were done for all the used images. In this study, to highlight the images and extract more information from the images from the false color combination, Landsat 8 and (5-4-3 near-infrared bands, red and green). To use different applications, the Gram, Schmidt and Pansharpring methods showed better sharpness of the features of the study area than other methods, so the combination of images was applied with this method. To identify the blue zone of the investigated area from the AWEI spectral index and to investigate land cover changes, the maximum likelihood classification method has been used.

In the present study, using ENVI 5.3 software in band calculations Spectral index, AWEI was selected and calculated for the years 2013 and 2022 to extract the water area of Horul Azim lagoon. the results showed that; the AWEI index has values greater than zero (positive values) indicating the water zone and smaller than zero (negative values) indicating the non-water zone (vegetation and soil). After performing the classification process, it is necessary to calculate the accuracy of this classification. To ensure the accuracy of the classification, the classification accuracy was evaluated, for this purpose, the Kappa coefficient and overall accuracy were calculated using the ground control points for each class separately in ENVI 5.3 software. The result of the accuracy evaluation is shown in the error matrix table. According to the available data, the spatial resolution of the images, and the researcher's knowledge, 4 educational classes, including water cover, vegetation cover, barren land, and saline land, have been selected for each image separately. The results obtained from the maximum likelihood classification method in the ENVI5.3 software environment were changed to vector format and the result was transferred to the GIS software environment in shape file format and land cover classes was determined.

The results of monitoring changes in the water area of Horul Azim lagoon (AWEI index) showed that the size of the wetland has been decreasing in the studied years it was also determined by checking the accuracy of the results of processing and classification of satellite images that the classification of images in a supervised manner, the maximum likelihood algorithm for the studied area is close to the ground realities and has acceptable accuracy. The results of the classification of images in the investigated years also indicate a decrease in water and vegetation cover and an increase in barren and salt marshlands in the investigated periods. There have been many influential factors, including environmental and human factors, on this process of changes in the investigated period, which include these cases: Successive droughts and the occurrence of harmful changes in the climate have caused changes in environmental conditions such as high salinity and inappropriate temperature. This means that significant changes in the ecosystem have reduced the number of aquatic species, animals, and plants, as well as people, which has led to a decrease in diversity indicators and an increase in dominance. The increase in pollution was caused by the entry of industrial, agricultural, and urban effluents into the rivers leading to the wetland. In addition, the construction of roads and embankments, in addition to cutting off the water connection of parts of the wetland, has turned them into salt marshes and dry land. The construction of the Karkheh dam and a result of not respecting the water rights of the lagoon, human encroachments, and occupations, including road construction, Oil activities, and encroachment on wetland lands have caused some parts of the wetland to dry up completely As a result of the fragmentation of the wetland and the increase of dry and salinity spots, the drying of the wetland is spreading. This trend states that the increase in human interventions will lead to an increase in the destruction process.