محمدرضا اختصاصی

Various tools have so far been developed with different efficiency to measure the flow of wind deposits. In this regard, two types of absorption and maintenance efficiency tools are commonly used as technical criteria in selecting sediment traps, bearing the lowest amount of wastage. Accordingly, this study set out to compare and contrast the adsorption and retention efficiency of BSNE and Siphon (3rd generation) as wind erosion sediment trap tools.

The efficiency of siphon traps (3rd generation) and BSNE were investigated and measured at different wind speeds of 7, 8, 9, 11, and 13 m/s using the wind tunnel laboratory of the Faculty of Natural Resources and Desertology. The efficiency was also measured in different events within the natural environment using Wind Erosion Monitoring stations. On the other hand, to check the absorption efficiency, the test tray was filled with air sediments, and the sediment catchers were placed inside the device. Then the sediments collected in the device were measured in terms of different speeds. Moreover, to measure the retention efficiency, the sediment traps were filled with 100 grams of wind-induced sediment, and the amount of lost sediment was measured at different wind speeds. After the sediments were granulated with the help of a shaker machine, the granulation indices of the sediments were obtained using the grain gauge software G.R. Graph.2. Finally, the data collected regarding the efficiency and performance of the two types of sediment traps were analyzed. It should be noted that the results were obtained in terms of 7, 8, 9, 11, and 13 m/s speed rates under different laboratory conditions (wind tunnel) and natural environment or desert at the wind erosion measurement station of Yazd University.

According to the results of the study, the absorption efficiency of the siphon trap was found to be 2 to 5 percent greater than that of the BSNE trap. Moreover, the study found that while the increasing trend of the siphon sediment trap’s efficiency against the wind speed of 13 m/s reached its maximum at roughly 94.6%, the maximum efficiency of the BSNE sediment trap was recorded at the speed range of 11 m/s (92%). Both sediment traps experienced a decline in wind-borne sediment capture efficiency at wind speeds of 11 meters per second. In both traps, the capture efficiency decreased with increasing height above the surface. However, the siphon sediment trap consistently demonstrated a higher capture efficiency compared to the BSNE trap. On the other hand, it was found that at heights lower than 50 cm from the ground, the absorption efficiency of 3rd generation siphon traps was approximately 1.5 times greater than that of BSNE traps. While at higher altitudes, the absorption efficiency of both approaches. Furthermore, the 3rd generation siphon sediment trap could maintain almost 100% retention efficiency due to its special tank design when the wind speed increased to rates over 11 meters per second under super-critical conditions. However, due to the design of the BSNE sediment trap, approximately 3% of the total captured and trapped sediment was lost from the reservoir and escaped into the surrounding environment.The results suggested that the numerical index of the particles collected in siphon sediment traps was lower than that of BSNE, which could partly be attributed to the exit of some of the fine particles when trapped in the reservoir of BSNE sediment traps. Moreover, the numerical value of the skewness index of the sediments collected in each type of sediment trap decreased with an increase in wind speed, tending towards fine particles. In other words, the increased population of fine particles caused a decrease in the average value of the median diameter or D50.

The results indicated that the highest absorption efficiency rates were 94.6 and 92% for 3rd generation siphon trap and BSNE, respectively. Also, compared to the BSNE, the siphon trap performed relatively better in terms of sediment storage and retention under physical and aerodynamic conditions. On the other hand, as for the retention efficiency of both types of sediment traps, it was found that the 3rd generation siphon trap performed 100% successfully at all investigated speeds. However, the efficiency of the BSNE sediment trap decreased from 100% to 97% when the speed increased from 11 m/s to 15 m/s, indicating that by increasing the speed and creating a twisting current inside the chamber of the BSNE sediment trap, part of the fine-grained sediments were thrown out of the trap, thus reducing the retention efficiency of the trap. It could generally be argued that the absorption and retention efficiency of the siphon trap is about 10 to 40% greater than that of the BSNE. Therefore, as the siphon trap is designed and built in Iran, it bears more advantages than its American counterpart.

Windbreaks act as natural or artificial barriers that, by reducing wind speed, prevent soil erosion, reduce humidity, and damage to agricultural products, and increase crop efficiency. Due to the specific climatic conditions of Fars Province, where drought and inappropriate temporal and spatial distribution of rainfall are undeniable realities, it can be said that irrigation water is the most important input for agricultural production, and any sustainable food production and agriculture depends on the correct and rational use of the province's limited resources. A review of research conducted at the national level shows that despite the increase in the efficiency and productivity of irrigation water in the field in recent years, for various reasons, including disregard for climate potential and water resources and unplanned development of agricultural lands to meet the food needs of the country's growing population, excessive extraction of groundwater resources and the destruction of aquifers have been witnessed. The aim of this study was to investigate the effect of density and distance from windbreak on the production of wheat and dry fodder, as well as soil moisture retention at a depth of 10 cm. This study was conducted in the 1401-1402 crop year on four homogeneous and uniform wheat plots with identical varieties, planting dates, planting distances, soil characteristics, and irrigation and fertilization conditions in the Shahed area of ​​the Faculty of Agriculture of Shiraz.

 This research was conducted in the 1401-1402 crop year in four homogeneous and uniform wheat crop plots at the Shiraz University of Agriculture farm (crop area about 547 hectares). For this study, three plots with different densities of tree windbreaks (density above 90%, between 40 and 90% and also less than 40%) and one plot without windbreaks were used. To investigate the effect of distance from windbreaks on soil moisture storage parameters and crop yield, distances of 1, 5, 10 and 15 times the height of the windbreak (average height 12 m) were determined in lands with high, medium and low density and without windbreaks, and soil samples and crop yield were collected in three replications from each distance based on a completely randomized block design. To measure the moisture content after sample collection and transfer to the laboratory, the samples were first weighed, then placed in an oven for 24 hours and weighed again. Also, to measure the yield after harvesting a plot (one square meter) of wheat in completely random replications and at specific intervals from different treatments, samples were collected separately and kept in the environment for four days until the moisture in their forage was completely dried. First, the harvested crop was weighed, then the wheat was separated from the forage, and the net weight of wheat and the weight of dry forage were weighed.

Results and discution:

The parameters studied were analyzed using SPSS software at a significant level of 5% using Duncan's test. The results of comparing the average percentage of soil moisture retention in three densities, high, medium and low, showed a similar trend with respect to height, such that the lowest moisture loss was at a distance of one height from the windbreak and in the plot of land with a density above 90%. The plot of land with a density below 40% at a distance of 10 meters from the windbreak had a similar performance to the land without a windbreak and did not show an effect in reducing moisture loss. In relation to the amount of crop production, the density above 90% has a more significant difference with other densities, so that the average crop production at different distances (1, 5, 10 and 15 times the height of the windbreak) was 2.24 kg/m2, which decreased to 2.13 kg/m2 at medium density, 1.97 kg/m2 at low density, and 1.94 kg/m2 in the plot of land without a windbreak. In other words, under the same agricultural conditions, the amount of crop produced in the plot of land with medium density was 4.9%, in the plot of land with low density was 12.05%, and in the plot of land without a windbreak was 13.4% less than the plot of land with high density. In the plot of land with low density at all distances from the windbreak, the amount of crop produced in the measured area behaved similarly to the plot of land without a windbreak and did not differ significantly from each other.

 The present study investigated the effect of density and distance from windbreaks on the production of wheat and dry fodder, as well as the maintenance of soil moisture at a depth of 10 cm from the soil surface. Windbreaks can reduce water evaporation from the soil and plant surface by reducing wind speed in the areas around them. Therefore, soil moisture is maintained more in lands with windbreaks, which will benefit plant growth and crop production efficiency. As shown in the results, the production and moisture from the soil surface are a function of the height of the distance from the windbreak, and the maximum production was at a distance of five times the height of the windbreak. It is suggested that in studies related to this subject, a plot of land without wheat cultivation and only to examine the soil moisture at different distances from the windbreak should be investigated. Also, for the construction of windbreaks around Shiraz farms, educational and promotional programs should be provided for farmers on the benefits of windbreaks and how to construct them; cultivated fields should be identified, parceled, and prioritized; Also, multipurpose and economically suitable native species for creating windbreaks should be identified and introduced. It is worth noting that creating financial and advisory facilities while encouraging farmers can help accelerate the implementation of this strategy.

The comprehensive management of watershed resources is considered as a new principle for planning the development and management of water and soil resources with an emphasis on the social and economic characteristics of the region in order to provide a sustainable livelihood for the vegetation and users of a basin without vulnerability. Although each country has its own conditions, there are similarities in the challenges faced by watershed management, in particular water resource management. Therefore, it is important to examine the experiences of other countries. In this research, the experiences of comprehensive watershed management approaches at the national and transnational levels were reviewed. The main aim of these plans was to improve and preserve water and soil resources, taking into account the improvement of the livelihood of local communities. According to these studies, a comprehensive watershed management approach has resulted in achievements such as attracting people's participation in projects, protecting water and soil and preventing land degradation, increasing the income of basin residents, women's participation, reducing soil erosion, reducing pollution, etc. The use of successful experiences of countries and the presentation and implementation of the compiled model can serve as a guide for decision-making and action in the field of watershed management, thereby promoting the stability and development of the country's watersheds.

Reducing the adverse effects of wind on the field, biotic and abiotic windbreaks help increase the crop yield. Moreover, by lowering wind speed and controlling wind erosion, windbreaks reduce and control local dust, increase water consumption efficiency, decrease annual evaporation and transpiration, and meet the plants’ water needs. Therefore, this study sought to investigate the potential and limitations of providing windbreaks for the agricultural lands of Shiraz Plain.

This developmental applied study was carried out based on a descriptive-analytical method using field, library, and document studies to collect the required data. To do so, the strengths, weaknesses, opportunities, and threats were identified by attending the farms, collecting the intended data by interviewing the farmers, and administering a questionnaire. Then, the matrix of internal and external factors was prepared and presented to 20 experts working in Jihad Agriculture and Natural Resources of Shiraz for scoring (based on the Likert scale of 5).To prioritize the criteria and indicators involved in providing windbreaks for the farms, a 20-item questionnaire was developed to get the opinions of relevant experts and managers using the AHP method to create comparative matrices and determine their compatibility. In addition, the range of all comparisons’ compatibility was calculated via the compatibility rate formula, the results of which confirmed the acceptable compatibility of the pairwise comparisons.

seeking to take advantage of the opportunities by using the strengths, the study selected an aggressive strategy which comprises a combination of opportunities and strengths after determining the final coefficient based on experts' opinions.
As for the strengths of the option of reducing evaporation, the study found that increasing the yield and the irrigation intervals offered the greatest score (0.367), indicating the positive influence of a windbreak on water consumption. On the other hand, in terms of weaknesses, windbreak shading was found to achieve the highest score (0.358). Moreover, accessing financial facilities was found as the greatest opportunity, with its score being 0.364. Finally, financing the provision of a windbreak was reported as the greatest threat, the score of which was found to be 0.359.

Considering the special climatic conditions of Fars province which is characterized by dryness and improper distribution of precipitation in time and place, any sustainable agricultural and food production depends on the correct and rational application of the province's limited resources. Many studies have already investigated the rate of evaporation and transpiration and product efficiency for instance, Campi et al, 2012; Smith et al, 2021; Cochrane and de Vries, 2014; Thevs et al, 2021).Taking what was mentioned above into consideration, this study suggests that windbreaks be provided for the Shiraz Plain. To this end, some training courses can be organized for the farmers in windbreak advantages and how to provide it, so that they are encouraged to provide for biotic windbreaks and create a protective green belt around the farmlands. In the second phase, the farmlands under cultivation should be identified, plotted, and prioritized. In the third phase, multipurpose native species suitable for planting biotic windbreaks and creating protective green belts should be identified and introduced throughout the areas covered by vegetation. It should be noted that offering financial and advisory facilities to farmers can help precipitate the implementation of the aforementioned strategy.

The increased use of fossil fuels has resulted in the production of pollutants and the release of greenhouse gases, leading to a global rise in temperature and climate change. On the other hand, climate change significantly influences temperature, precipitation, humidity, and cloud cover in local and regional variations. Therefore, considering the varying trends of climate change across different regions, it is crucially important to investigate the long-term trends of key climate parameters, including temperature and precipitation.Global Climate Models (GCMs) are reliable tools for simulating the global climate response to greenhouse gas concentrations. Performing based on greenhouse gas emission scenarios, the models can project the data of future climate variables such as precipitation and temperature for the entire Earth in three dimensions. On the other hand, the temperature is expected to rise in different parts of the world by varying degrees, although the exact amount is uncertain. In this regard, climate change not only raises temperature but also affects the hydrological cycle by accelerating ocean surface evaporation.It is important to acknowledge the uncertainty of GCM outputs in investigations, as its ignorance may reduce the reliability of the results. It should be noted that the raw data obtained from GCMs may not adequately resolve this problem and can diminish the precision of the results. Bias-correction methods have become increasingly common in climate change impact studies over the past decade, ranging from simple averaging methods to complex ones. Therefore, this study sought to investigate the efficiency of LS, NBC, and SDSM bias-correction methods and the combination of SDSM and LS models in reducing the uncertainty of CanESM2 temperature predictions in dry areas. 

covering an area of approximately 74,650 square kilometers, Yazd province is located in the center of Iran between 29 degrees 48 minutes to 33 degrees 30 minutes north latitude and 52 degrees 45 minutes to 56 degrees 30 minutes east longitude, being characterized by the most unfavorable natural factors that dominate Iran’s central plateau.This study used three groups of data: 1) daily temperature data collected from Yazd synoptic station from 1966 to 2020, provided by the National Meteorological Organization; 2) Atmospheric statistics obtained from the National Center for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) for the same period; 3) CanESM2 general circulation model of temperature simulations used for the periods of 1966-2005 and 2006-2045, based on the RCP8.5 emission scenario. The study applied three bias-correction methods, including LS, NBC, and SDSM, and performed LS on the outputs of the SDSM model to correct the temperature outputs of the CanESM2 model under the RCP8.5 emission scenario. To assess the efficiency of the methods used, the outputs of each bias-correction method were compared with observational data during the 2006-2020 period. 

The results revealed a consistent sinusoidal trend in the daily and monthly temperature data. The highest and lowest monthly average temperature rates were found to have been typically recorded in July and January, respectively. Moreover, the average annual temperature indicated an increasing trend from 1966 to 2005, which was found to have continued from 2006 to 2020, but with fewer variations. On the other hand, the results of the CanESM2 temperature simulations based on the RCP8.5 emission scenario suggested that the variations followed a pattern relatively similar to that of the observations. The average annual temperature simulated by the model for both the past (1966-2005) and future (2006-2045) showed a significant increasing trend. However, observational data for the 1966-2005 period indicated a slower increasing trend than the simulated values during the same period. As predicted, compared to the raw model values, the bias-corrected values obtained via the LS method better matched the actual data found for the evaluation period (2006-2020). As for the NBC application, the results suggested that the method improved the accuracy of future average temperature projections of CanESM2. It was also found that SDSM and LS offered relatively acceptable accuracy in terms of SDSM outputs. The results also revealed that the temperature data corrected by all four methods, including LS, SDSM, NBC, and the combination of LS and SDSM agreed well with observational data collected from the synoptic station, whose coefficients of determination were found to be 0.948, 0.968, 0.969, and 0.969, respectively. Moreover, the non-parametric Kendall test revealed a significant increasing trend in the average annual air temperature for both past and future periods in the study area.

the comparison of the coefficients of determination of the average monthly temperature rates corrected by the above-mentioned methods and the ones found for the observational data during the evaluation period indicated that all four bias-correction methods performed acceptably in the study area. It is worth noting that the LS method showed a slightly poorer performance than the other error correction methods. Based on the results of this study, it can be concluded that since the efficiency of methods used for reducing the uncertainty of temperature outputs in dry areas was relatively acceptable, it seems that investigating suitable methods for reducing the uncertainty of precipitation outputs in dry areas would be of greater importance.

Access to groundwater resources as one of the highest quality water sources has always been of interest to residents of dry and desert areas around the world. This essential need has led to the drilling of wells in most of the basins in these areas. On the other hand, the evaporation process from water sources such as wells and qanats also leads to losses and water shortages in dry and desert areas, which are often not considered in water resource management. Therefore, measuring the rate of evaporation from wells and qanats as the most important water sources in dry and semi-arid areas is the main approach of this research. The present study aims to measure the rate of evaporation from wells and qanats and analyze the results of expert surveys regarding the selection of the most suitable methods to reduce evaporation from wells using a hierarchical analysis method or AHP through questionnaire analysis and the results obtained were analyzed using Expert Choice software. This research was conducted in two parts: field operations and installation of four standard gypsum blocks with dimensions of 5 × 3 × 7 cm at depths of 30 cm (well mouth), 1 meter away from the well, 20 meters away from the well, 40 meters away from the well, and measuring and comparing the moisture percentage, as well as laboratory experiments. The results of measuring the moisture percentage in the wells under study showed that with an increase in distance from the well mouth, the moisture decreases, and with an increase in well depth, the moisture percentage increases. The moisture absorbed by the gypsum block inside the moist and water-rich well was higher than the dry wells, including sewage wells. Furthermore, the results of comparing the main criteria in the Expert Choice software showed that the highest weight was related to the type of well (0.66) and the lowest weight was related to the time criterion (0.04). The well depth (0.20) and the type of sediments (0.08) were ranked third and fourth in priority, respectively. The comparison of sub-criteria of the type of well led to the placement of qanat rods in the first rank with a weight of 0.687 and sewage wells in the fourth rank with a weight of 0.127. The comparison of time sub-criteria led to the placement of the summer season in the first rank with a weight of 0.496 and the night in the fourth rank with a weight of 0.04. Based on the sub-criteria of sediment type, the covered basin had the highest weight (0.729) and the bare basin had the lowest weight (0.109). Overall, most experts believed that unused and unexploited wells should be filled. However, they had different opinions on the three parameters under study, with well capping having a higher priority in reducing evaporation from wells with a weight of 0.709, and well mouth capping being the lowest priority with a weight of 0.113.

Wind erosion is one of the natural and important factors that contribute to desertification and land degradation in semi-arid, arid, and hyper-arid regions. Wind erosion is more likely to occur in these areas, which encompass 40% of the earth's surface, due to drought and low soil moisture, limited vegetation, soil characteristics, and erosive winds. Sand transport by erosive winds is a common wind process in arid and semi-arid regions, and it has become a widespread global problem. The biological and economic resources are damaged by this process. To control wind erosion and stabilize shifting sands in these areas, a barrier can be used to reduce wind speed to less than the threshold speed of wind erosion. Depending on the purpose, sand barriers can be used in different heights, dimensions, and arrangements. One of these barriers is a straw checkerboard barrier. The use of this method began in the Soviet Union; then it was transferred to China. Ghana, Egypt, and Mongolia have also introduced and used it in a limited capacity. Sand barriers have a long history in Iran, but their use has declined due to limited and scattered applications. Barriers can be constructed in every region using materials like reed plant stems, cotton plant stems, palm tree leaves, and straw. The aim of this research is to evaluate the efficiency of a checkerboard barrier made from the stem of a reed plant in stabilizing shifting sands. Compared to other materials, their use is cheaper and does not cause any environmental pollution in nature. By controlling wind erosion, improving the conditions of the area and reducing damages caused by the shifting sands, it leads to achieving sustainable development.

The research was conducted in the sand dunes surrounding the village of Hossein Abad Mish Mast in the center of Qom province. The results of the sand rose and wind rose demonstrate that the winds in this region are multidirectional. This research examined the feasibility of utilizing a checkerboard barrier made from reed stems. In order to attain this objective, the surface of a sand dune was covered with the barriers mentioned. The height of these barriers was about 20 cm. The characteristics of sediment grain size were assessed by sampling the surface of the sand inside checkerboard barriers and the control dune in this research. Also, mode, average diameter, skewness, and sorting were investigated.A stabilization efficiency coefficient was calculated to evaluate the impact of the barrier on stabilizing sand dunes. For this purpose, wooden stacks were installed in different parts of the dunes in such a way that they could well express the amount of sand detachment and deposition, and in general the changes in the mobility and displacement of the dunes.The checkerboard barrier's concave shape was measured by installing steel stacks with 10-cm intervals vertically inside a cell on the windward side of the dune. Weekly monitoring of the steel stacks resulted in the drawing of the concave curve of the barrier in Excel.

The reed stem barrier's sediment grain size characteristics showed that it had a significant impact on the accumulation of fine sand particles compared to the control. Consequently, the particles are scattered within the diameter layer of 250-125 microns, while the granulation analysis before the barrier and control dune was implemented revealed that approximately 64% of the particles were scattered within the diameter layer of 250-500 microns. The control dune sediment granulation analysis showed that the particles' average diameter increased by 45.5% from the control dune sample before the barrier was implemented. The reason for this is that the activity of erosive winds in the region has increased. The wind flow passes a large amount of sand particles over the dune due to the intensity of wind erosion in the region. Smaller particles are transported and larger particles remain on the surface of the dunes due to the absence of barriers in the way of wind and sand flow.According to the concave shape of the checkerboard barrier, a small amount of sand particles was observed in the examined cell. The concave surface was not formed during the study period. The height and density of the reed stem barrier are the reasons for this. The height of the reed stem barrier, which is 30 cm, and its semi-denseness caused the flow of sand and wind to lose its energy upon hitting the first rows of the barrier, and deposit the sand particles in the first rows. Therefore, there is a lack of particle deposition in the middle grids of the dune. Using reed stem barriers to control wind erosion is one of the appropriate and effective measures that stabilize the surface of sand dunes. In fragile ecological conditions of desert areas, where it is not possible to establish a plant without support, this method is highly effective.

 One of the most important features of any watershed is the threshold of the start of runoff, which can reflect the different characteristics of the watershed and is an important factor in identifying and determining the flood status of the watershed. Accurate estimation of the amount and duration of runoff due to rain events, followed by the starting point of the flood, is one of the main points of interest in hydrological studies of watersheds. The runoff threshold is the amount of effective precipitation that is required during a certain period of time at the level of a certain watershed to start a flood at the outlet of the drainage channel of that level. The purpose of this research is to determine the minimum rainfall, or in other words, the effective rainfall on the start of runoff, in the Sanij watershed in the province of Yazd. By determining the height of the minimum rainfall for the start of runoff in the mentioned basin or other basins, one of the main and effective components in studies related to flooding and flood risk zoning is provided.

 The study area in the current research is the Sanij watershed, 30 km from Yazd city in Taft city, Yazd province, with an area of 153.173 square kilometers and geographic coordinates 31°32°48 to 31°18°42 north latitude and 36°54° north latitude. 53 to ˝54 ˊ03 ° to east longitude. Its annual rainfall is 220 mm, the average annual temperature is 11.2 degrees Celsius and the average relative humidity of the basin is 42%, the maximum height of the basin is 4036 meters and the lowest point is 2020 meters high. The concentration time of the area (Tc) according to the Bransby-Williams method is 5.18 hours. The stations targeted in this research are the Faizabad hydrometric station at the outlet of the Sanij watershed to provide flood discharge data, the Bidakhoud rain gauge station for hourly rainfall data and the Faizabad climatology station to provide 24-hour rainfall data. daily) whose data was available for the period from 1370 to 1400. To achieve the goal of the research, the relationships between maximum 24-hour rainfall and runoff threshold were investigated. Also, the compatibility of the corresponding hydrographs and hyetographs was studied in order to estimate the minimum rainfall for the start of runoff, and the intensity of rainfall was checked in the time base of 1 hour.   Then EXCEL software was used to analyze statistics and information.

 The results of investigating the relationship between the runoff threshold and the maximum 24-hour rainfall, whose data was a combination of 24-hour rainfall and torrential rainfall, showed that their function is y=0.9131x+ 14.01 and the minimum amount of precipitation with 82% of  R2 is equal to 14.01 mm. It also showed the results in the adaptation section of water patterns and corresponding rain charts; The average height of precipitation for the start of runoff is 18.9 mm. Finally, the average value for the minimum precipitation height in both study methods was 16.45 mm. Also, the intensity of precipitation in the time base of 1 hour was estimated as 13 mm; Therefore, if the intensity of precipitation is more than 16 mm in the time bases above 1 hour, it is expected that runoff will be produced at the outlet of the basin.

 The aim of the present research is to determine the threshold of effective precipitation that leads to the flow and start of runoff in a complete basin in the arid regions of central Iran..By knowing the threshold of the start of runoff in watersheds, one of the main components in hydrometric studies and optimal flood management is provided. The results showed that if the duration of rainfall in the basin is more than one hour and its amount is more than 16 mm, the runoff will flow at the outlet of the basin. It is also important to know the threshold of effective precipitation in the beginning of runoff in watershed plans, optimal use and management of precipitation, as well as the design of rain catchment surfaces to absorb precipitation. It should be noted that the results of this research depend to a large extent on the direction of the entry of rain-producing systems as well as its distance from the outlet of the basin, which is suggested to be investigated in future researches.

The coefficient of hydraulic roughness of rivers is one of the most important factors in the planning, design, operation, and maintenance of water resources projects in river engineering studies. The value of the hydraulic roughness coefficient varies in diverse and complex conditions of rivers and is affected by various factors, usually in hydraulic models the roughness coefficient shows the most sensitivity compared to other parameters. A correct estimate of the roughness coefficient improves the understanding of flow hydraulics and river conditions. Despite many efforts, the inability to accurately estimate the roughness coefficient and the use of Manning's constant value (n) are the main error factors in flood simulation and flow depth calculation. The flow roughness coefficient is typically not constant and changes dynamically as the flow depth changes. The best way to determine the roughness is to measure the flow rate and calculate Manning's n through the inverse solving of Manning's equation. The present study mainly aims to determine more precisely the roughness coefficient of the Sanij River upstream of the Faizabad hydrometric station.

The studied area in the current research is the Sanij watershed, 30 km from Yazd city in Taft city, Yazd province. This basin has an area of 153,173 square kilometers. To achieve the objectives of the research, after conducting field studies, the Faizabad hydrometric station at the outlet of the Sanij watershed was used to collect the required flood discharge and ash-flow data in the study area; Therefore, the hydraulic radius and the value of Manning's roughness coefficient were estimated through the inverse solving of the corresponding equations and the determination of other hydraulic parameters such as velocity and slope. The slope was measured with an inclinometer and a leveler.

The lowest value of the n is equal to 0.034, corresponding to a discharge of 180 m3s-1 , while the highest value of the Manningʼs roughness coefficient is equal to 0.119, corresponding to a discharge of 2.083 m3s-1 . As the discharge decreases, the roughness coefficient increases. The function of the roughness coefficient in relation to the discharge (with R2  = 0.80) indicates their inverse and significant relationship. The function of the hydraulic radius in relation to the discharge (with R2  = 0.944) indicates that the discharge and hydraulic radius have a direct and significant relationship. The roughness coefficient has an inverse lower less-significant relationship with the hydraulic radius. Every flood creates different roughness levels with different sedimentation rates; therefore, Manning's roughness coefficient will vary depending on variations in particle diameter. Usually, the channels or rivers of dry areas are temporary, in the descending branch of the hydrograph and at the end of the flood, larger parts remain on the surface of the bed, and it causes errors in the estimation of Manning's roughness coefficient based on experiments and local visits. The apparent error is caused by the larger diameter particles remaining on the surface of the bed and the carrying of fine particles by the flow. On the other hand, during the flow, the orientation of the sediments is generally in line with the direction of the flood, which creates the least hydraulic roughness; But with the reduction of flood intensity and the remaining of coarse-grained particles, in addition to the increase of hydraulic roughness, the random roughness of particles, which plays an effective role in Manning's roughness coefficient, increases. In flows where the flow depth is lower than D90, or smaller than the diameter of large pebbles in the bed, Manning's roughness coefficient reaches its highest value under static-hydraulic conditions, and inflows with greater depth From D90 due to special hydrodynamic conditions, the lowest value of Manning's roughness coefficient was observed. In other words, at high flow rates, the relationship of the roughness coefficient on the entire flow is reduced; therefore, with the increase of the flow depth, the value of n decreases and the hydraulic radius increases. This phenomenon is mostly seen in rocky channels and rivers. The current research showed that in the rivers of dry and rocky areas, we usually encounter overestimated values of Manning's roughness coefficient due to the presence of large pebbles in the bottom of the dry bed. This phenomenon can be seen especially in floods with lower discharge and the cause of this can be related to the reduction of hydraulic roughness in the bed during the flood flow. This phenomenon can be effective in overestimating or underestimating the roughness coefficient.

The results show that the roughness coefficient changes from 0.034 to 0.119 in the study range and has an inverse and significant relationship with discharge (R2  = 0.8). Moreover, the roughness coefficient has an inverse relationship with the hydraulic radius (R2  = 0.59). The roughness coefficient is not constant and changes in different flood events. Discharges with a depth less than D90  are those in which Manning's roughness coefficient reaches its maximum value of 0.11. In this study, the lowest Manning's roughness coefficient was observed in discharges with a depth greater than D90  and a flood height greater than 50 cm, as in the discharge of 115m3s-1 , the roughness coefficient “n” decreased to a limit of 0.034. The roughness coefficient is unstable in different events, because during the passage of the current or in the ascending and descending branches of the flood hydrograph, depending on the speed and power of the flow, the bed granularity is dynamically changing, and Manning's roughness coefficient (n) is instantaneous. It changes. During the peak flow, it is difficult to understand the hydrodynamic roughness coefficient and it can lead to overestimation or underestimation of the roughness coefficient; Therefore, it is better to consider this case to achieve more accurate values of roughness coefficient in river engineering studies

Providing good quality drinking water is one of the most important concerns of today's societies. Using a proper system for the fair distribution of potable water is very necessary and evidently the type of the system will lead to different amounts of water use per capita. Today, the dispute over good quality water resources in arid regions has escalated, Governments are forced to use separate drinking and sanitation water systems. Understanding the consumption of people in the form of per capita is a prerequisite for the proper design of drinking water distribution networks, the data of which are collected and analyzed in different ways. Quality of groundwater resources in Bajestan region, has led to the plan of separate drinking and sanitation water, with the establishment of government water collection stations since 2014. The purpose of this article is to estimate the per capita drinking consumption by query method by considering 378 samples and random sampling at certain distances from each station. The amount of per capita obtained is estimated at about 3 liters, but its amount has a different distribution in different city districts ranging from 2.5 to 4.5 liters. The highest amount is obtained for the new districts with villa texture and the lowest for the zones with more apartments. The results of the survey of the plan and the problems and consequences of its implementation showed that about 69.03% of people are using the water of these stations for drinking and tea, which is the criterion for determining per capita; The biggest problems of withdrawal stations are the numerous breakdowns of the stations and difficulty harvesting them, which requires the revision of some network operations.

In order to supply the drinking water for inhabitants of arid areas always have several challenges. The main source of fresh water supply in these areas is groundwater, but in recent years, increasing harvests and declining aquifers have increased salinity. Bajestan watershed is no exception of this issue and the main source of drinking water and sanitation is groundwater sources from the Playa, which is of very low-quality water. By decreasing the quality of groundwater resources has created the project to separate drinking water and sanitation by creating “The Government Drinking Water Stations”, since 2014. The purpose of this study is to investigate the rate of realization of this project implementation in order to quality drinking water supply. For this purpose, some of water samples was taken from the network and drinking wells, then the samples were compared with National and International standards and prepared the groundwater resources quality map.

In this study, at the first stage, the water samples taken from drinking wells and distribution network in the same period (2014-2019) were collected and compared with National and International standards. These standards included the standard of the Industrial Research Organization of Iran (1053 Report), WHO, the United States Environmental Protection Agency (EPA), the European Union (EU) and Schuler diagram. Then, Prepared the maps based on 1053 and Schuler diagram (The most common drinking water quality standards in Iran) which were selected by choosing the best interpolation method in the field of Geostatistical by choosing the lowest value of RMSE.

The results of this research showed that all of the quality parameters of distribution network’s water samples were within the standard condition, the values ​​of all the quality parameters were equal or even lower than the standard value of the indicators, So the conditions are optimal. While the water quality parameters in drinking water supply wells were of unfavorable quality according to the values ​​of the standards used in the research; These are EC, TH, TDS, Na, CL ​​in the water samples obtained from the wells on the Playa were 4 to 6 times and in other wells on the plain were 1.5 to 2 times the values ​​found in the standard indices. The results of the interpolation of the quality parameters of the plain's groundwater showed that the Co-Kriging method has the lowest Error in the main parameters of water quality determination, including EC, TDS and TH, which shows the high correlation of the parameters, there was a high correlation of groundwater in the plain with each other.

Comparison of the samples in the two parts of the wells and the drinking water distribution network showed that the current plan has sufficient usefulness to providing the quality the drinking water. Also, based on the map of the quality of the groundwater resources of the plain, the playa has the lowest quality of water resources and the wells located in the plain area have better quality.

One of the major challenges in arid regions such as Iran is the supply of water with appropriate quantity and quality. Drought, disputes over water resources, and providing good quality and quantity water for drinking, agriculture, and industrial sector, have forced governments to use desalination technology or transfer water among watersheds, Water desalination is one of the solutions to providing drinking water in Central Iran and coastal areas. Bajestan plain is no exception and has been using this method for about 16 years to provide drinking water and health for residents. Investors have recently been encouraged to build mineral water plants in arid areas; While the socio-economic and its environmental consequences are not yet clear. The results of this study showed that to supply fresh water from desert saline water with EC about 7500 (µs/cm) and reverse osmosis method with a production volume of 1000 (m3/yr), the price per liter of water is equivalent to 45.067 IRR. In this process, around 500 m³ of saline water and more than 6 tons of salt will be produced, too. This amount of salt will increase the salinity of the lands around the pistachio fields and orchards by 2 to 3 times and decrease the yields by more than 60%. Results showed if the bottles are not recovered, more than 18 tons of polyethylene will be produced. The economic evaluation shows that the value of the Net Present Value Index is negative and Internal Rate of Return is not acceptable, and the B/C is 0.46, which indicates that it is not economical to implement. Implementation of this plan in other arid regions with these conditions will have similar results.

One of the integrated water resources management requirements based on participatory management planning is identification and analysis of key stakeholders. Identifying structural aspects of organizational stakeholder's network can be evaluated using social network analysis and their position and role for inter-organizational integration and coordination in water resources management can be determined. In this study, using social network analysis method, stakeholders related to participatory governance of Abhar plain water resources, including 20 organizational stakeholders were analyzed and policy indicators were evaluated at the level of the network of organizational stakeholders. Indices of density, size, reciprocity, transitivity, centralization and geodesic distance in network of relationships at the macro level, core-peripheral index in the middle scale and centrality indicators at the micro scale of network were examined. Rate of network density index is moderate and according to index of reciprocity, moderate amount of bilateral and reciprocal relations among organizational actors, cohesion and organizational capital are assessed as moderate. According to transitivity index, stability and balance of information exchange network is low. Analysis of core-periphery index of stakeholder's network shows a higher density of links and greater organizational cohesion among central organizations compared to peripheral subgroup and amount of information exchange between central and peripheral subgroups was evaluated as moderate. Based on centrality indicators, geometric position of each actor in network was determined. For decision-making, planning, policy-making and participatory governance of water resources in Abhar Plain, key and effective organizations and political forces, as well as organizations with low power and marginalized, were identified.

Lack of rainfall, reckless grow of planting the agricultural products, uncontrolled abstraction of groundwater resources and lack of proper plans to reduce the adverse effects of the water crisis, has caused a sharp decline in the country's aquifers. The main objective of this study is to strategic management of water resources to determine the most appropriate management strategies for aquifer balancing.

Determining the most appropriate management strategies for balancing the Abhar plain aquifer has been done using the SWOT strategy formulation method. The most important internal and external factors (strengths, weaknesses, opportunities and threats) affecting water resources based on statistics and information collected, identified and after completing the questionnaire and survey, using group decision-making, the best strategy and applicable management approaches were explained.

The results of this study indicate that the weakness outweighs strengths as well as threats over opportunities. In other words, from the perspective of the experts present at the brainstorming session, the conditions of Abhar plain are in the quarter of weaknesses-threats (WT) with a defensive strategy that indicates the critical condition of Abhar plain aquifer in terms of the status of available water resources. Therefore, considering the current critical conditions of Abhar plain, the importance of optimal management, prevention of uncontrolled abstraction of groundwater resources, considering the most important weaknesses and main threats in this plain and the results of SWOT analytical model, the most appropriate solutions achieving the goal of balancing the groundwater aquifer of Abhar plain, are consist of focusing on land integration and preventing their fragmentation through integrated pressurized irrigation systems, changing the type of cultivation, irrigation method, benefiting from suitable climatic conditions for species cultivation low water demand, suitable geographical location in order to develop low water demand industries and equip water wells with smart meters to control and manage consumption. On the other hand implement watershed management and artificial recharge measures to prevent floods and loss of water resources and surface runoff harvesting was determined to control, manage and optimally use surface water resources and reduce abstraction from groundwater aquifers.

Using the capacity of opportunities and strengths ahead, Abhar plain aquifer strategy can be upgraded to ST strategy as well as WO and will be controlled the decreasing trend of Abhar plain aquifer volume.

Due to the low annual precipitation rate and, therefore, the existence of a weak and fragile ecosystem, arid regions are more subject to drought. Moreover, significant fluctuations in the temporal and spatial distribution of precipitation make drought forecasting in these areas a complicated task. Having a dry and fragile climate, Yazd Province has experienced numerous droughts within the past few decades. Therefore, it is highly important to monitor and forecast drought in this region. Population growth has increased water demand. Moreover, the increase in the concentration of greenhouse gases due to rising fossil fuels consumption has caused global warming and climate change, changing the hydrological cycle components including precipitation patterns (snow and rain). Therefore, climate change has changed the frequency, severity, and duration of droughts in many areas, especially in arid and semi-arid regions. So far, several indices have been developed to assess drought. This study used the RDI, which is based on precipitation (as system input) and potential evapotranspiration (as output), to estimate the drought. Furthermore, there are several methods for forecasting drought, among which projections of global climate models derived from greenhouse gas emission scenarios are quite common.

This study sought to analyze the efficiency of global climate models in predicting drought in arid regions (Yazd Synoptic Station, Yazd, Iran). To this end, 1961 to 2005 was selected as the base period, RDI values of which were imported to downscale the model (SDSM). Moreover, 2006 to 2018 was selected as the forecast period whose data were not imported to the model. Finally, the predictions of the model for the period 2006 to 2018 were compared with the observed RDI values of the same period for time scales of one, three, and six months. Accordingly, first, the climatic data collected from Yazd Synoptic Station (minimum and maximum temperature, relative humidity, sunshine hours, and wind speed) were prepared, and then the potential evapotranspiration (PET) was calculated for the period 1961 to 2018 via FAO-Penman-Monteith method. RDI value for the period 1961 to 2018 was then estimated on a monthly basis.Moreover, to predict drought through global climate models, CanESM2 global model forecasts were obtained based on the RCP8.5 greenhouse emission scenario from 2006 to 2018 for monthly precipitation, minimum temperature, maximum temperature, average temperature, sunshine hours, wind speed, and relative humidity. Using SDSM statistical downscaling model, the observed data for the period 1961 to 2005 and the projections of the CanESM2 model for the period 2006 to 2018 were downscaled. On the other hand, the mean surface temperature predictor was used to a downscale minimum and maximum temperatures and sunshine hours. Wind speed and surface-specific humidity predictors were also used to downscale wind speed and relative humidity outputs, respectively. Furthermore, to increase the accuracy, three predictors of precipitation, surface specific humidity, and mean surface temperature were used to downscale precipitation outputs. Finally, as for the high spatial and temporal variability of precipitation in arid regions, possible biases in precipitation data were corrected using the Linear Scaling bias correction method, which is based on the average difference between monthly observed time series and GCM historical simulations time series over the same period of the observed series. These differences were then applied to the future GCM simulated climate data to get bias-corrected climate variables.

The results obtained from the application of the FAO-Penman-Monteith method indicated that the variable trend presented by PET values during the study period was mostly induced by changes in wind speed fluctuations. Moreover, downscaled precipitation values showed a more significant error rate than those of the downscaled temperature outputs, probably due to the fact that precipitation values had more variability than the temperature ones, especially in arid climates. On the other hand, the application of the Linear scanning bias correction model showed that the precipitation values downscaled by SDSM for the base period (1961-2005) were overestimated compared to the real precipitation data over the same period. Therefore, the overestimation was corrected using the Linear scanning bias correction method. After correcting the probable precipitation biases and calculating the RDI index, the results suggested that the use of the Linear scanning bias correction model remarkably increased the accuracy of CanESM2 precipitation outputs.Then, the RDI was calculated by replacing the predicted precipitation and potential evapotranspiration values with the real data in the period 2006 to 2018 by measuring the potential evapotranspiration based on the data mentioned. Accordingly, R2 between real RDI values and the CanESM2-extracted forecasted RDI values for the 2006-2018 period was 0.472 for the 1-month time scale, while R2 was 0.738 and 0.762for for 3 and 6-month time scales, respectively.

The results indicated that the model presented a good performance at 3 and 6-month timescales. Moreover, considerable fluctuations in one-month precipitation values resulted in high variability of the one-month RDI time series, decreasing the model's performance at this timescale. Therefore, for projecting precipitation in arid and hyper-arid zones, a bias correction method should be applied to minimize probable biases. Furthermore, the comparison of actual droughts that occurred from 2006 to 2018 with the values ​​predicted by the model at 1, 3, and 6-month time scales showed that the CanESM2 model predicted the drought patterns with relatively good accuracy at 3 and 6-month timescales. However, as for the one-month timescale, the model presented lower efficiency than the other two time scales due to more fluctuations. Therefore, it can be concluded that GCM forecasts have a relatively acceptable efficiency for long-term drought prediction in arid climates.

Since there are not enough tools to measure flood, erosion and sediment in many watersheds of the country, it is necessary to use indirect methods such as fractal geometry to estimate them. There is very little accurate information about erosion in our country (Mohammadi et al. 2008). Understanding the sedimentation status and sedimentation of basins provides an accurate understanding of erosion and its consequences (Piri et al. 2005). Some parameters of watersheds have a special geometric shape that can be examined with fractal geometry. Mathematically, the basins that have the same fractal dimensions are equivalent to each other and are very similar in terms of geomorphological and hydrological characteristics (Adl and Mehrvand, 2004). The aim of this study is to obtain a significant relationship between fractal drainage network and erosion and sedimentation rates, and to generalize the results to unmeasured areas. 2. Introducing the studied area The studied area consists of 12 basins of Ilam province, which are in the western foothills of Zagros Mountain. Figure 1- The position of studied basins in the country and in the Ilam province Table 1- Specifications of basins and their stream gauging stations

These networks were provided based on 50DEM coordinates that in many cases, there isn’t enough accuracy and some channels are not displayed. Therefore, after transferring data to Google Earth, it was fully matched with the natural drainages and with a 5-meter accuracy, hydrographic network map was drawn and completed to reflect the full details of the network.Thence one cannot scale maps via “Fractalys”, fields with the same space of 25 kilometers on similar formations in different areas were accidentally chosen via “Fish Net” –in Arc GIS, to fix this problem. For each study formation, three 25sq.km. Fields were chosen and by the accuracy of 5 meters. These maps that had the same drawing accuracy and space, were drawn in the same scales via GIS on an A4 page in .bmp” and then were brought to Fractalys and finally, their fractal dimensions were calculated and extracted by the geometric method of counting boxes.

Figure 2- Hydrographic network and fractal dimension of the nazarabad watersheds before hydrographic network modification Table 2- Fractal dimension of watersheds before and after hydrographic networks modification In the following figures, the calculated fractal dimensions are observed for several samples of 25 km units before and after the hydrographic network modification. After the modification before the modification Amiran Aghajari 1.134 1.481 1.149 1.435 Figure 3- Fractal dimension of a hydrographic network of Aghajari and Amiran formations before and after hydrographic network modification. Quaternery Gachsaran Figure 4- Hydrographic network modification in the 25km unit on Google Earth Figures (3) to (4) show that after hydrographic network modification, the density of the hydrographic network and consequently the fractal dimension are increased in units of 25 km. Also, hydrographic network density changes in more sensitive formations are more than resistant formations, so their fractal dimension changes are also higher.Figure 5- Investigating the correlation of fractal dimension with hydrological indexes of Ilam watersheds the R2 value that is representing the correlation value is 0.0905. Therefore there is no significant relationship between the specific flood discharge of watershed and its fractal number. Table (3) Correlation test of specific flooddischarge data (Qw) in terms of (m3/s/ Km2) and fractal number (Fr) of the basins after modification of 25km units In Table 3, the specified number (-.240) indicates the correlation value of the data. Due to the obtained value, there is no correlation between the specific flood discharge and the fractal number of the basin.Figure 6- Correlation line chart of specific flood discharge data and fractal number of basins after modification of 25km un its Figure 7- Investigating the correlation of fractal dimension with the sedimentation index of Ilam watersheds In Figure 8, Due to the R2 value (0.939), it can be also concluded that there is a significant and direct correlation between the specific sediment discharge value and fractal dimension of the watershed. The following tables show the results of the calculations performed in SPSS software. Table 4- Correlation test of specific sediment discharge data (Qs) and fractal number (Fr) of basins after modification of 25km units The results of SPSS in Table (4) show that there is a high correlation between the specific sediment discharge data and fractal number. Because the number of 0.996 equals the correlation value between the two variables of the specific sediment discharge and the fractal dimension of the basins. The dispersion of data in the figure represents a high correlation in the data. Because the data are not scattered.

The fractal dimension gives more accurate results by the box-counting method than the magnification and radial methods..The results of the research show that there is a significant and inverse relationship between the fractal dimension of the formations and their resistance to erosion.As the strength of the formation increases, its fractal dimension decreases and therefore the density of the hydrographic network is lower.There is no regular trend between the hydrographic network density and the fractal dimension of the basin with the specific flood discharge of basins.Also, there is no significant relationship between this index and the fractal dimension of the basin.There is a significant and direct relationship between the fractal number and the specific sediment discharge (at a level of 5%), which indicates the erosion and roughness rate in the basin The highest value of fractal dimension can be observed in areas that are very sensitive, including Doiraj basin to 1.49.The least value of fractal dimension can be observed in areas that are resistant to semi-resistant in terms of geological formations, such as Kolm and Chamagaz equal to 1.14 and 1.11, respectively.

It is necessary to determine the appropriate probability distribution for fitting the flood data. There are several methods for estimating the parameters of probability distribution functions. In the present study, L-moments approach is used for flood frequency analysis in Gavkhouni Basin, Abarkouh- Sirjan Basin and Yazd- Ardakan Basin. Some stations were selected and their data were analyzed to find out peak discharge. Then, Hosking and Wallis homogeneity criterion were used to identify the homogeneous region. Examining the homogeneity criterion closely shows the discordant region. Eliminating and transferring some selected stations, leads to determining a homogeneous region of flood frequency. Parameters of the regional frequency distribution were evaluated using L-moment, moments, and maximum likelihood methods. The results of this analysis were compared using RMSE, R, and RRMSE statistics. The goodness of fit tests such as Chi-square, Kolmogorov-Smirnov were applied for checking the adequacy of fitting of probability distributions to the recorded data. The study reveals that the Pearson Type-3 distribution (using LMM) is better suited amongst the ten distributions used in estimating the peak flood. In general, the L-moment method estimated the peak flood for return periods of 10, 25, 50, and 100-year, and moments method at return periods of 2 and 5-year.

Digital elevation models and its derivatives are important factors for watershed modeling. It is obvious that DEM errors adversely affect the accuracy and thereby modeling of natural processes. This problem along with the impossibility of measuring all elements of nature, has led to a major evolution in the way of understanding and explaining phenomena. In this way, we can use the fractal geometry as a quantitative tool for modeling many complex natural phenomena. In fact, geophysical phenomena such as drainage networks are fractal phenomena with fractal behavior. The purpose of this paper is to evaluate sensitivity of the drainage networks based on DEMs (ASTER & SRTM), flow direction algorithms (Single Flow Direction (D8) and Multiple Flow Direction (MD8)) and topographic maps of 1:25000 in order to study the fractal dimension of drainage network on geological formations of Yazd-Ardakan basin. The results showed that the least difference in the length and the rank of the stream belonged to the drainage network obtained from the topographic maps of 1:25000. After the topographic maps, ASTER and the multi-flow direction algorithm are close to real ground map. Even though the multi-flow direction algorithm shows more detail on the drainage network. But it is not close to real ground map. The difference is particularly noticeable in the first rank of streams. Due to the very high sensitivity of the fractal dimension to the smallest change in drainage network conditions, the drainage network obtained from topographic maps were used to calculate the fractal dimension. The mean fractal dimension of 1.149, 1.16 and 1.207, respectively, represents Taft, Granite and Kahar formations. There is a significant correlation between fractal dimension and sensitivity to erosion of geological formations (level 0.99). In fact, the fractal dimension increases with increasing the sensitivity to erosion along with the drainage density in geological formations. The results showed that fractal dimension allows for a quick and accurate analysis of sensitivity to erosion of the formations of this area.

The increasing exploitation of groundwater reserves and consequently the drop in the water level and reduction of the reserves have seriously caught the attention of officials and planners to the integrated management of groundwater and surface water resources. The evaluation and management of water resources are considered as one of the key factors in comprehensive development. Boein Aquifer in Isfahan Province located in the Gavkhooni Basin is studied in this study. The Standard Precipitation Index (SPI), Reclamation Drought Index (RDI) and Groundwater Standard Index (GRI) in the time scales of three, six, 12, 24 and 48 months and Cultivated Land Index (CLI) in annual time scale are calculated. Results showed that the highest correlation between the SPI and GRI is in 18 and 24 months' time scale, and there is a delay of 1.5 to 2 years between these two droughts. Contrary to the results of some references, the correlation between meteorological drought index and GRI does not always increase with increasing the time scale. A synchronic study of the SPI, GRI and CLI shows a large difference between the SRI and the other two indicators in 2004-2008 periods that may be related to the poor management of the region. However, more close values obtained for these three indices in the recent years mainly due to the better management of water consumption by relevant organizations. To determine homogeneous drought regions, different combinations of temporal and spatial scales were used by creating 39 different scenarios and running 390,000 simulations. None of the heterogeneity measures were met in 90% of cases. This indicated that the linear moment technique is not a suitable method for determining homogeneous arid regions of groundwater probably due to the non-random data. Therefore, the linear moment technique will be more useful if the data is random.

In natural resources, economic evaluation is poor in terms of study due to the uncertainty of non-consuming value of resources. In the present study, the evaluation of water, soil and plant resources in watershed management projects and expert questioning was done to enable the projects to be evaluated and prioritized economically. Three sub-watersheds were selected from the Parcel A watershed of Gheshlagh Dam basin in Sanandaj, that the mechanical, biological and biomechanical operations in each of them was executed. The amount of water, soil and plant resources of each project according to the guidelines of Forests, Rangeland and Watershed Management Organization was estimated. The ratio of income to cost and the cost of each unit of resources were obtained by calculating the value of each unit of resources and calculating revenues and costs in each project. Then, water, soil and plant economics as criteria and watershed projects as sub criteria were determined with paired comparison matrix questionnaires. A project has priority that protects more resources at a lower cost than another. Questionnaires were distributed among experts and data were analyzed by Analytical Hierarchy Process. The results of the expert questionnaire and the valuation of the sources were compared. The results showed that, the cost per cubic meter of water in the mechanical project is higher than biological projects, although experts prioritize mechanical methods economically but biological with an income-to-cost ratio of 2.2 is the top priority .The cost of water in the mechanical, biological projects was respectively 1.4, 1.2 times the price per cubic meter of water in the area. Soil and plant prices were also calculated and the biological project became the top economic priority. Therefore, priority should be given to biological projects that have less cost and more impact on resources, contrary to watershed experts and detailed-executive studies. As well as the mechanical projects should be limited to areas in critical flood situations, provided that operate biological projects in upstream.

Today, various watershed management projects are being implemented in watersheds which sometimes, despite high study and cost, they are inefficient for various reasons and face economic failure. In the present study, first, different watershed projects in the Parcel A of Gheshlagh Dam in Sanandaj were evaluated. Then, their evaluation was examined by determining internal and external factors. The aim is to extract the most important factors and provide strategies that make projects economically viable and functionally effective. Weaknesses, strengths, opportunities, and threats of the region were extracted by experts and, using the SWOT analysis model and quantitative matrix of QSPM, economic-applicable solutions were presented. Results showed high value of management factors, so that the highest final value in external factors was inefficient study projects and the lack of funds for maintenance and repair of projects after implementation with scores of 0.50 and 0.43, respectively, and internal factors had the highest final value related to destruction and burial of dams due to the low quality of construction with a score of 0.59 which had the most impact on strategy selection. Based on the results of the model, the strategies are located in the ST quarter and are of a conservative method, in order to reduce the damage caused by threats and weaknesses by using the strengths of the domain. In accordance with this strategy, solutions were given by experts and prioritized by the quantitative matrix QSPM. The implementation of projects on land owned by individuals or the assignment of the right to maintain them to the owners with a final score of 8.76 was ranked first. The results of this research in the present economic situation of the country are very useful for informing authorities about how to optimize the implementation of watershed projects and will improve the instructions and implementation and the best use of projects.

Dust is one of the phenomena of atmospheric and natural disasters that poses adverse environmental effects and impacts. Due to the wide distribution of dust, this phenomenon can also change the soil and its biology trends. Typically, dust particles have a diameter of less than 100 microns, which can be transmitted horizontally or vertically to the ground after miles. The aim of this study was to determine the amount of dust falling and heavy metals lead and cadmium concentrations in dust samples to evaluate these elements is the urban pollution.

In this study, samples were collected using mild sediment trap for six months. A total of 180 samples were collected. Samples were weighed accurately using a scale of 0.001 g. The analysis of samples was performed using ISO11466. The samples were extracted by the Institute of Water and Soil Research, and the concentration of heavy metals was measured by the atomic absorption spectrometry of the Analyti jena-951 model.

The results showed that in the winter of March and in the spring of June, the highest rate of dust was observed. The mean lead concentration in winter was 97.32 ± 5.40 mg.kg and 90.16 ± 5.93 mg.kg in spring. Also, the average cadmium concentration in winter was 37.19 ± 3.60 mg.kg and 29.62 ± 2.42 mg.kg in the spring. According to the pollution index (PI), the level of contamination of lead is high in the floor, however, according to this index, cadmium contamination in both seasons is more than the level of contamination of lead and is higher than the limit, which is the risk index The ecology of cadmium, with an average of 1673.98 and 1333.03, also confirms this and is in the hazardous area of contamination. Also, the ecological risk of lead metal in winter was 18.14 ± 1.01 and in the spring with a mean of 16.91 ± 1.11 in the low pollution class. According to the values obtained for the pollution load index (PLI), this contamination rate is Cdwinte r˃Cdspring˃Pbwinter˃Pbsprin, and both of these elements are highly polluted in the classroom.

The results of statistical calculations and contamination levels indicate that the amount of dust pollution to lead and cadmium is higher than most of the calculated indices in the classes with high to high contamination.Therefore, these elements have been brought into the environment as a result of human activities and have less natural origin.

Drought is a natural hazardous phenomenon occurring in all climate types. However, it affects arid and semiarid regions more intensely than other areas. It also severely affects both the quantity and quality of water resources in arid zones. Moreover, land-use changes and urban and agricultural development also adversely influence water resources in these regions, especially groundwater resources.The extraction of a significant portion of drinking and agricultural water from groundwater resources has led to a sharp decline in groundwater storage in Iranchr('39')s arid and semiarid regions. Furthermore, as mentioned before, frequent droughts and land-use changes have affected these resources. This study, therefore, sought to investigate the effects of meteorological drought and land-use changes on groundwater quantity and quality in Darab plain, Fars Province, Iran.

Darab Plain is located in the south of Iran. The water supply in this plain is highly dependent on groundwater. The mean annual rainfall is 275 mm, and the mean annual temperature is 22 0C. In this study, data regarding precipitation, groundwater level, and salinity were used to estimate SPI (Standardize Precipitation Index), GRI (Groundwater Resources Index), and SECI (Standardized Electrical Conductivity Index). SPI is considered as the indicator of meteorological droughts. GRI quantifies changes in groundwater levels as a standardized index. SECI is applied to estimate any potential shifts in groundwater quality. Land-use maps of the basin for 2001, 2009, and 2017 were prepared using satellite imagery. Moreover, Landsat TM, ETM+, and OLI sensors were used. It should also be noted that land-use maps were created using the Supervised Classification method (Maximum likelihood algorithm). The produced maps included five classes: urban area, farmlands, gardens, rangelands, and bare lands.

SPI results showed normal classes for most of the years throughout the study period (-0/99 to +0/99). However, the trend line indicated an apparent decreasing trend for SPI during the period. Therefore, it could be concluded that the region is experiencing more droughts. A study of groundwater level changes suggested a continuous reduction of 36 m for the entire study period. While the comparison of SPI and GRI showed a general decreasing trend for GRI, it could be seen clearly that SPI changes caused GRI shifts. Moreover, droughts accelerate GRI reduction, and SPI growth either reduces GRI decreases or increases it slightly.On the other hand, SECI results indicated the salinity growth and quality reduction in the region. During the study period, the plain experienced a 293.6 µmho/cm increase in salinity. Furthermore, the comparison of GRI and SECI showed that any reduction in groundwater level would result in more saline. The comparison of land-use maps during the three years (2001, 2009, and 2017) also proved that agricultural uses increased by only 0.26% in 2009 compared with 2001. However, in 2017 compared with 2009, such uses decreased by 1.62%.The relationships between SPI and land-use changes with GRI and SECI were also investigated, indicating that droughts and land-use changes directly affect the quantity and quality of groundwater in Darab Plain.

Climate change has affected many parts of the world, changing drought characteristics in many regions. Therefore, the subsequent changes in water resources could be considerable. Furthermore, water resources are under pressure for population growth and land-use change. In this study, the collected data was divided into three 8-years periods (1993-2001, 2002-2009, 2010-2017), and the averages of SPI, GRI, SECI, and land-use were calculated for the three periods. The results showed that the increase in the severity of drought and the rise of the agricultural lands in the second period compared to the first one caused a decrease in water quantity (GRI decrease) and quality (SECI increase). However, a decrease in the severity of drought and the fall of the agricultural land-use in the third period compared to the second one lowered the rate of groundwater level decline (compared to the rate of GRI decreasing in the second period). In the third period, SECI increased (less quality) in response to the GRI decrease. The results showed that groundwater resources in Darab Plain were strongly dependent on both drought and land-use changes. The groundwater quality in the region was also directly affected by changes in groundwater level.

Seasonal floodwater has been kept in the lands by using watershed projects so that it penetrates into underground beds, but this case causes different influences on graining, permeability, underground water and vegetation. Three sections were chosen as experiment sites to measure soil changes of watershed projects in Nodoushan watershed area of Yazd province. Seven permeability experiments with double cylinder inside every section and three experiments in the control group were performed. Along with each of these experiments, one sample was collected from 0.5 meter of the surface soil and graining experiment was performed on it. The significance of permeability was investigated by the use of non-parametric Mann-Whitney test and Kolmogorov–Smirnov test. The results show that permeability in Sadrabad, Nodoushan and Alaviyeh in control group were 4.92, 3.52 and 5.89 cm/ hr, respectively. After some periods of dewatering they were reduced 94 percent, 89 percent and 92 percent, respectively. And finally reached to 0.28, 0.37 and 0.47, respectively. Also, the average diameter of the particles decreased about 90 percent. The results of experiments showed that the decrease of permeability was significant in the level of 95 percent.