مجله مهندسی و مدیریت آبخیز
سال چهاردهم شماره 4 (زمستان 1401)

The purpose of this study was to investigate the oak forest dieback with respect to drought occurrence, soil moisture changes and dust occurrences factors in Ilam, Kermanshah, Lorestan and Chaharmahal and Bakhtiari provinces of Iran. The data used were field surveys collected through GPS, MODIS satellite imagery, GLDAS Soil Moisture, dust and precipitation data of the meteorological stations of the provinces during an 18-years period (2000-2017). The results of the study of greenness values of the forests in the study area showed that the first decline occurred in 2005 and repeated more severely with much wider spatial extent in 2008. Investigation of the relationship between drought events and its spatial and temporal variations with the changes in forests greenness of the study area showed that the reduction in precipitation amount is one of the main reasons for forest greenness reduction in the study area. The increased frequency of periods of rainfall shortage and drought duration, especially at 9 and 12-month time scales, showed a significant relationship between drought occurrences and forests greenness in the study area. The results indicated that by decreasing precipitation drought periods increased, soil moisture decreased, and dust storm occurrences increased. As a result, in most of the years, with decreasing soil moisture and increasing dust storms, the forests greenness of the study area has decreased and vis versa. Therefore, there is a direct relationship between soil moisture and forest greenness while an inverse relationship exists between dust and forest greenness.

Flood control projects, artificial recharge of ground water aquifers, and optimizing the efficiency of water and soil resources are the most important benefits that have been achieved as a result of the construction of flood spreading stations in the country. The aim of this research is assessment and determination of effectiveness of Jajarm flood spreading project. For this purpose was the economic evaluation of flood spreading project using Net Present Value (NPV) and Benefit/Cost/ ratio studies in Jajarm Station. The social impacts of the Jajarm flood plan were also assessed through a popular questionnaire. Results showed that NPV was 262258 million Rials with discount rate according to the Central Bank. This shows that the Jajarm flood project is economically justified on the basis of economic evaluation and that investment is economical. The evaluation of the impacts of the floodplain project from the view point of the users of the project margin, also indicates that the people of the region are relatively satisfied with the project. Particularly people's satisfaction with the role of the flood spreading project in reducing flood damage to residential, land and communication areas in the region is significant.

Runoff is one of the major components of the hydrological cycle, which leads to soil loss from steep slopes and sediment production in watersheds. Investigation of effective factors in runoff coefficient is important in watershed management. The aim of this study was to investigate the effect of soil properties on runoff coefficient in Alanagh, Livar and Shekaralichay sub-basins in East Azarbaijan Province. After soil sampling, some physicochemical properties were measured and runoff data were obtained from the relevant stations. Based on the results, runoff coefficient in the studied sub-basins is affected by various soil properties such as particle size distribution, gravel, organic matter, lime, aggregate size and stability, and saturated hydraulic conductivity. As the percentage of sand and gravel increases and the percentage of clay and silt decreases, soil permeability increases and runoff coefficient decreases. Organic matter and lime are two important factors in the aggregate formation and stability, and improving the saturation hydraulic conductivity which plays a key role in reducing runoff production. The results of multiple linear regression analysis showed that runoff production in the Alangh sub-basin has a significant relationship with soil organic matter (r=-0.95, p<0.01) and bulk density (r=0.9, p<0.01). Organic matter content has the main role in runoff production in Livar sub-basin (r=-0.94, p<0.01) and Shekaralichay sun-basin (r=-0.95, p<0.01). Runoff coefficient in all sub-basins in the area is strongly related to organic matter content (r=-0.86, p<0.01), soil structure stability (r=-0.68, p<0.01) and stream density (r=0.49, p<0.01). This study showed that preserving and increasing soil organic matter can be an effective strategy in conserving rainwater and reducing runoff by improving soil structure and permeability.

Nowadays, global climate change has been observed which had an impact on both surface and groundwater resources management. The main objective of this research is change detection of groundwater fluctuation caused by climate change in Borkhar Plain, Isfahan Province. In this way, both Mann-Kendal and Sen’s slope non-parametric analysis were used using 19 piezometric wells data for the period of 1991-2019. Pearson correlation matrix along with correlation between climatic elements including temperature, precipitation and evapotranspiration (Thornwhite) with water table levels were determined. Based on this, a multivariate regression model was developed to model the annual time series at a confidence level of 0.95. Climatic factors of 2080-2099 period were simulated using the output of HadCM3 model through Lars-WG downscaling model for Maymeh Station under two scenarios A2 and A1B and based on the developed regression model, the water level of Borkhar Plain was simulated. The results showed that in the base period, the water table in the study area has been decreased with an annual slope of 47 cm per year. Correlation analysis showed that the three climatic elements of precipitation, temperature and evapotranspiration in a linear composition modeled 0.75 of the annual groundwater changes in the plain. The results of the exponential microscale model implemented on HadCM3 data showed that in the period 2080-2099 under both scenarios, the groundwater level of the region will decrease between 15 to 17 meters compared to the base period.

Nowadays remote sensing is known as practical method for studying Land Use (LU)/Land Cover (LC) changes. Due to the vast area of agricultural lands, Barandouzchay Basin is one of the important watersheds among all of watersheds in Lake Urmia River Basin. In this study, in order to evaluate LU/LC change, Landsat-5 TM and Sentinel-2A satellite images were used from 2005 to 2016. The maximum likelihood classification method was used to prepare LU/LC maps. The results of overall accuracy and Kappa coefficient showed high accuracy of maximum likelihood classification method. In order to extract the change detection maps, image difference method was used. Results showed that orchard and nonproductive trees have been increased during 2010-2016 years in Barandouzchay Basin. In the years before 2010, trees were relocated by young trees in Barandouzchay Basin. Drylands and bare lands are classified in the 2005-2010 years which has been increased. The most land use change was related to urban and lowest change was related to rainfed area from 2005 to 2010 and the most land use change is related to bare lands and lowest rate is related to nonproductive tree area from 2010 to 2016.

Desertification is a problem that is currently affecting many countries in the world, including Iran. This problem is seen not only in arid and semi-arid areas, but also parts of semi-humid areas. The purpose of this study is to investigate and zoning the intensity of desertification using the modified Medalus Model and hierarchical clustering method in the Baqous Plain of Sabzevar. For this purpose, effective criteria in desertification including climate, vegetation, soil, erosion, and selection management, and the geometric mean of the indicators were calculated. Data layers indicators related to each criterion were prepared using the GIS system. This information was scored based on the Medalus method and from the geometric mean of the indicators of each criterion, the final map of the status of each criterion was prepared and from the geometric mean of the criteria, the current map of the desertification of the region was prepared. Results showed that the criteria of vegetation, climate, and erosion were more effective than other factors in desertification of the region and high sensitivity and critical type was matched with the poverty of vegetation and the dryness of the climate, and work units 1 and 2 have the largest area of desertification types with high intensity. The results also showed that 21% of the study area is in the high sensitivity zone, 28% in the high and critical sensitivity zone, 17% in the low sensitivity zone, 28% in the low and critical sensitivity zone, and 6% in low sensitivity zone to erosion. 55.6% of the results of modified Modalus Model were obtained by significant clustering methods. According to the spatial distribution map of desertification intensity extracted from the model, it can be used as an auxiliary tool against desertification and prevent excessive destruction of the region in the future.

Precipitation estimation is of great importance in energy balance calculations, hydrological studies, meteorology and agricultural, industrial, domestic and drinking purposes. Due to the importance of precipitation data in various sciences and the lack of an extensive and appropriate rainfall network, especially in mountainous catchments, it is necessary to estimate precipitation data and evaluate their accuracy. The purpose of this study is to evaluate the precipitation data of three IMERG satellite products of near real-time type, 3B42RT-7 of real-time type and PERSIANN-CDR of final-run type in the period of 06/01/2000 to 09/31/2018 in 41 rain gauge stations and three synoptic stations in and around the Neishabour Catchment area on a daily and monthly time scale. Examination of various statistical indicators showed that none of the three satellite products is a good representative of terrestrial data on a regional and daily scale. Therefore, the use of these products on a daily basis in this basin in hydrological models is not recommended. On the other hand, the monthly scale showed much better performance due to the adjustment of the error of estimating daily precipitation. So that, the correlation coefficient and Nash Sutcliffe coefficient of PERSIANN-CDR with monthly precipitation data in the basin are about 90% and 0.75, respectively, and the evaluation of this product is much better than the two products 3B42RT-7 and IMERG. Accordingly, the use of monthly scale precipitation products of the final-run type in water balance studies, especially in basins without statistics, can be considered.

Gully erosion contributes severe land degradation. It is therefore, necessary to identify the aggravating factors and to provide for sensitive areas to gully development. The aim of this study was to determine the spatial and climatic distribution of gully in Kermanshah Province, Iran and to identify the morphological characteristics and the main factors of their development. First, using 1: 20,000 and 1: 50,000 aerial photographs, the predominantly gully areas of the province were identified and then this information was corrected using field suevey. The climatic zones of the gully areas are identified using existing maps and modified by the Domarten Method. In each climate, one to three gully areas were identified as targets and in each of them a gully was identified and two replications were identified. The gully chanel chrectreristices were location, landuse, dimensions at the head-cut, intervals of 25, 50 and 75%, slope, width, length and cross section. The results showed that 17% of areas in the Kermanshah Province was affecterd by gully erosion comprising eight sub-climate classes. Dominat topographic conditions of gullies were developed at hilly and gentle plain areas with Trapezoidal cross section. The cross section indicated deep and V-shaped gully in marl formations (Fars group). These areas included Sarfiroozabad, Somar and Jabbarabad where most of gully measures were deeper and wider than other parts. Among the effective factors in creating and expanding the gully, we can mention heavy rainfall, slope, soil erodibility and destruction of vegetation upstream of the basin as natural factors and change of land use and improper exploitation as human factors in developing gully erosion.

Occurrence of numerous floods in different regions of the country has always caused a lot of damages in various fields. Therefore, it seems necessary to prepare and compile a comprehensive plan in the field of flood control. The study area is influenced by the Mediterranean climate and within the radius of the Caspian and Caucasian climates. Due to the high altitude differences, it has a variety of climates and high variability in rainfall, and known as one of the areas exposed to destructive floods. The purpose of this study is to identify flood prone areas based on multi-criteria decision making and neural network model in Khodaafarin Watershed. For this purpose, according to the factors affecting the occurrence of floods, the information layers of the region including Curve Number (CN), Gravilius coefficient, runoff height, precipitation, distance from waterway, soil retention, waterways, slope, drainage density, geology and vegetation, according to the study of maps, reports, satellite images and field surveys. In order to weight the criteria in the present study, network analysis method (ANP) and Super Decisions software were used. The factor of runoff height with the amount of 0.241, slope with the amount of 0.207 and precipitation with the weight of 0.169 were the most important in relation to flood occurrence. Finally, by combining these layers according to their weight in the GIS environment, a flood risk zoning map was extracted in five classes. The results also showed that, 43 square kilometers (3% of the area) of the watershed is in the very high flood risk class and 288 square kilometers (18% of the area) in the high flood risk calss. More than 21% of the area is among the areas with high and very high flood potential. Therefore, it seems that the need for surface water management in the region in order to prevent floods and the proper use of water in the region is necessary.

One of the natural landscapes observed in arid and desert areas is the accumulation of loose sand in and around plants, which over time causes the formation of sand masses. In Arabic, this type of land is called “نبکه: /næbkæ/”, which means small hill and ridge. The word has been translated from Arabic into English as well as Persian, and in most scientific texts in these two languages, the word “nebkha” and “نبکا /nebkɑ/” are used to express this form of land, respectively. Studying the scientific texts, it was found that there are other writing methods such as nabkha, nebka, nabka and nabkhah for this word, which with the images used to show this phenomenon, indicates that all the authors meant nebkha. These differences in spelling prevent researchers from accessing most of the research done on this phenomenon. In addition, terms such as coppice dune and phytogenic hillock are found in the equivalent of nebkha in the literature. In this short article, the use of the word nebkha in the texts as one of the landform of deserts has been studied. The results showed that in order to obtain more comprehensive information when studying this phenomenon from different aspects such as geomorphology and ecology, it is necessary to search for different writing methods and equivalent words.