نشریه مدیریت جامع حوزه های آبخیز
پیاپی 1 (پاییز 1400)

The aim of this study was to analyze the factors affecting the occurrence of floods and to prepare a zoning map of flood potential in two sub-watersheds of Arghavan and Kalanar, sub-watersheds of Ilam watershed, using AHP method. For this purpose, slope, vegetation, geology, soil permeability, drainage density and watershed shape as effective parameters in flooding in the studied sub-watersheds were selected. After the experts familiar with the watershed completed the questionnaire, these parameters were weighted. Using the results of weighting, the flooding potential zoning map was then calculated. Based on the results, the slope and shape indices of the watersheds had the highest (0.293) and lowest weight (0.072) and effects on flooding, respectively. According to the flood zoning plan, zones with very high flooding class are 1.45% of the area in Arghavan watershed and 14.77% in the sub-watershed of Kalanar, and zones with very low flooding class are 2.86% in Arghavan watershed and 1.25% of the watershed area in Kolanar. According to the final flood potential zoning map, Kolanar sub-watershed has a higher flood potential due to its high slope, impermeable formations, low vegetation and relatively round shape, as well as high specific discharge (0.52 m3/s.km2) compared to Arghavan sub-watershed (0.29 m3/s.km2) and the Arghavan sub-watershed contains a larger volume of floods due to its larger surface area than the Kalanar sub-watershed. As a result, experts should pay more attention to the Kalanar sub-watershed, which has a higher flood potential.

Desertification is defined as the reduction of the ecological and biological potential of the earth, which occurs both naturally and artificially. This phenomenon is one of the important problems of countries for sustainable development management programs, which is the result of a combination of various environmental, human and climatic factors. Water is recognized as an important and influential factor that is the main source of life and also guarantees the survival of sustainable ecosystems. Since water is more important in arid and semi-arid climates than in other climates, measures should be taken to properly manage water in order to prevent critical conditions in these areas. The purpose of this study is to investigate the status of water criteria to assess desertification. Due to the many effects that water indices have on the development of desert areas, in our study, we used quantitative and qualitative indices of groundwater such as electrical conductivity (EC), sodium absorption ratio (SAR), color (Cl), falling groundwater level and irrigation systems to study and determine the class of desertification intensity in Mehran plain. The IMDPA model was applied to evaluate the desertification situation. The results showed that the indices of decline and irrigation systems with average values of 3.11 and 1.75, respectively, have the greatest impact on the desertification process in the region. According to the groundwater status map in the destruction of resources in the study area, it can be concluded that 32% of the total area is in the low class, 48% in the middle class, and 20% of the total area is in the severe desertification class. In general, water resources management should be a priority for executive agencies to prevent desertification.

Rapid population growth, land-use change, and industrial and urban pollution are currently among the most serious human-caused problems in the natural environment. On the other hand, the change in land surface temperature is a factor in assessing the quality of habitat, which is modeled on land-use change. Therefore, it is necessary to examine the correlation between short periods of land-use change and surface temperature. This study shows the role of different land uses in the study area by examining the effect of land use on temperature parameters during the statistical period of 2013-2019 in the northern watershed of Ilam province with two mountainous-plain parts and industrial location despite oil and gas industries. Random forest and machining algorithm techniques were used to prepare temperature and land use maps from Landsat satellite data of ETM and MODIS sensors with a spatial accuracy of 30 and 250 meters, respectively, in Google Earth Engine. The results showed that during the six years, the level of water, rangeland, agricultural, and garden land uses have increased by 0.15, 3.87, and 3.42 percent, respectively, and other land uses such as forests and barren lands have decreased by 13.33 and 0.11 percent. The temperature algorithm using the LST index and creation of thermal islands showed that the average temperature of the region in the base period (2014) was equal to 31.02°C, which at the end of the study period reached 31.88°C. During the six years the temperature has risen by 0.68°C. According to the results, climate and land use are affected by each other and each shows its effects on the other.

Floods are among inevitable hazards but its frequencies and volumes can be varied due to climate change. A comprehensive analysis of synoptic status can be useful for predicting similar events in the future. It is therefore very important for a good environmental management. Flash flood of July 2015 in Saghez was a catastrophe and did severe damage. In order to analyze the catastrophic precipitation, sea level pressure, 300 hPa, 500 hPa, 700 hPa, 850 hPa maps along with Omega, perceptible water map and humidity maps were investigated and analyzed, starting two days before the rainfall until the end of rainfall and even a day after. Results show that immigrant European high-pressure system along with Arabian low-pressure tongue have caused intense rainfall during the day. Mediterranean Sea, black sea and red sea have been effective in enhancing the system too. A day before the rainfall, at surface level, a high-pressure European system from the North West and the low-pressure tongue from the south west were approaching the country and the combination of these two systems have caused intense rainfall on the region. Ag the higher level, trough axis was over Turkey, Iraq and Persian Gulf. Short waves displacements along with change in axis positioning eastward caused pressure centers in the surface level to get closer. At this time, all the western part was located under the eastern axis short wave trough, causing intensifying instabilities along with uplifting humid weather and finally a catastrophic intense rainfall on Saghez and its surroundings on July 18 2015. It is important to pay attention to comprehensive watershed management as one of the major strategies for adaptation and resilience in flood-prone areas.

Livestock grazing management is one of the main manifestations of integrated watershed management. Lack of awareness of the effects of livestock grazing on biodiversity makes sustainable watershed management impossible. Therefore, awareness of the variation in plant diversity and composition under natural disturbances such as livestock grazing is important for optimal ecosystem management. This study aims to investigate the effects of different grazing intensity (low, moderate, and high) on spatial diversity components (α-diversity, β-diversity and γ-diversity), turnover and nestedness components of β-diversity and species composition in semi-steppe Broujen rangelands in Chaharmahal and Bakhtiari Province. Vegetation sampling was conducted based on a random-systematic sampling design using 60 plots of 2*2m in three grazing intensities including low, moderate and high. Statistical analysis was performed in R software using “vegan” and “betapart” packages. The results showed that an increase in grazing intensity could significantly (P-value < 0.01) decrease α-, β- and γ-diversity indices, which, in low grazing intensity, were 11.77, 7.22, and 19, respectively, while in high grazing intensity they were 3.44, 3.55, and 7, respectively. In addition, an increase in grazing intensity could significantly (P-value < 0.05) increase the turnover component of β-diversity due to species replacement, while there was no significant effect for nestedness components of β-diversity. The NMDS analysis results showed that different animal grazing could drive a significant deviation in plant community composition. The results of this study suggest that the light grazing intensity could be used as a suitable management tool in order to maintain and improve plant biodiversity.

The production of waste has caused environmental crises that pose serious threats to the life of creatures on Earth. This study aimed to evaluate the strategy and location of waste disposal site in Kiyan watershed with an emphasis on EIA through survey-analytical method. Based on the locating process, a suitable landfill site of 10 hectares was selected in the village of Karke-oliya. As basalt-andesite rocks have high permeability and are resistant to erosion, the proposed area has high environmental capacity for waste disposal. Data from the Meteorological Organization show the prevailing wind direction within the study area is northwest. The western wind dominates, and since the villages of the study area are northwest and west of the landfill area, the effects of the landfill's unpleasant odor will be far off. In addition, since the area is enclosed in terms of topography, which can be seen in the transverse and longitudinal profiles of the region, the effect of the displacement of lightweight waste by the wind has been neutralized. It is important to note that the suggested burial ground is far from natural drainage, which makes the area suitable for landfill for hydro geological watershed purposes. The results of the environmental impact assessment also showed that the project has a positive impact of about 45%. Therefore, the proposed site is well-suited to environmental standards.