پژوهشنامه مدیریت حوزه آبخیز
پیاپی 26 (پاییز و زمستان 1401)

Intensification of natural disasters make it important to know the time variations of rainfall for wet and dry spell management and adaptation strategies. Measuring and predicting of precipitation anomalies using statistical methods is an important tool for climate studies. Seasonal changes determine the distribution of precipitation occurrence over a year period.

The purpose of the present study was to investigate the seasonality variations of monthly rainfall data using circular statistics method at 28 rain gauge stations in a 30-years period. According to the results, the seasonality index of monthly rainfall, standard deviations and standard deviations were calculated in the monthly time scale. In the circular statistics method, the time of occurrence of the event is determined based on the angle on the scale of the studied event interval.

According to the results, the value of the seasonality index (r) in the 8 rain gauge stations are greater than unity, which includes Pol Almas, Kousetopragi, Nir, Lay, Sarein, Siyahpoosh, Neur and Yamchi, meaning that the occurrence of precipitation in these stations occur completely with seasonal natureAccording to the results, there is no correlation between the mean amount of rainfall and the values of the seasonality index (r). The highest Seasonal index (r) is calculated for the Lay station with a value of 1.53 and the minimum value of the seasonality index (r) is assigned to the time series of Totoonsin station with zero SI value. At most of the studied stations, it is observed that the value of the SI value (r) is close to 1 which indicate the seasonal nature of the precipitation occurrence.

Based on the values of the seasonality index, wet periods and the time distribution of rainfall in different months of the year can be determined. Also, the seasonality index can be used to determine the duration of droughts. The numerical calculation of the index over a long period of time can provide a more comprehensive understanding of precipitation distribution. Most of the rain gauges with seasonal rainfall pattern located in the east and west part of the Ardebil province. In conclusion, determining the distribution of precipitation in the study area showed that the precipitation occurrence in the Ardabil province occurs seasonal with distribution of precipitation in two to three months of the year.

Floods are one of the most important natural disasters that cause the most damage to infrastructure sectors and greatly affect people's economic and social activities. The occurrence of this phenomenon cannot be prevented, but by taking measures, its effects can be reduced to a great extent. One of the management methods to reduce damage caused by floods is to identify vulnerable areas. The purpose of this research is to determine the vulnerable areas of Tajen watershed using a new approach.

Therefore, in this study, with the aim of identifying flood vulnerable areas in four economic, socio-cultural, structural-physical and policy-institutional dimensions, the "Best of the Worst Method (BWM)" which is based on linear planning, for Index weighting was used. In order to rank the criteria, Friedman test was used. The statistical population of the study is the villages at risk of flooding in Tajan watershed in Mazandaran province. To do this, 208 questionnaires were randomly completed by residents of 40 villages. In this study, in order to analyze the questionnaires and implement the BWM method, SPSS16 software and Lingo18 optimization model were used, respectively.

The results of Friedman statistical test showed that there was a significant difference (Sig = 0.00) between the criteria studied in this study. The economic criterion with a rank of 2.85 has the highest importance compared to the other three criteria. Also, the results of weighting the indicators using the BWM method, which are based on the preference of the best and the worst, also showed that in the economic dimension of the agricultural income dependence index (0.284), in the structural-physical dimension of the index, there are appropriate communication channels (road and bright) (0.243), in the policy dimension, the index of destruction of natural resources (0.379) and in the socio-cultural dimension, the index of access to health centers (0.391) have the highest weight and have a great impact on vulnerability in terms of respondents. Residents are flooded. Also, in this study, the value of incompatibility index was less than 0.1, which indicates the good accuracy of the BWM model in weighting vulnerability indices.

In order to reduce costs and reduce the complexity caused by the large number of criteria and sub-criteria affecting the vulnerability of an area to floods, the use of new multi-criteria decision-making methods based on linear programming is emphasized.

Assessing the effectiveness of Land management based on land capability in priority areas to preserve natural resources and prevent adverse effects of rainfall events is essential for comprehensive watershed management. At the same time, it prevents rapid and inappropriate changes in land use and leads to the promotion of ecosystem services. However, evaluation of the effect of management measures on changing soil erosion resulted from various storms with a focus on prioritized sub-watersheds is scant. Therefore, the present study was conducted to estimate and analyze the stormwise soil erosion dynamic under the influence of management measures based on land capability in the prioritized sub-watersheds of the Galazchai Watershed, Oshnavieh, Iran.

To achieve the objectives of the present study, firstly, according to the results of the Borda scoring algorithm, prioritized sub-watersheds with a relative area of about 34% were recognized. Then, the variability of soil erosion in 38 storms in recent years before and after the application of land capability in the mentioned sub-watersheds as well as the watershed was evaluated using the revised universal soil loss equation.

The results showed that the rate of soil erosion of the study storm events varied in the range of 0.012 to 0.028 t. ha-1. Storm-1. However, in terms of management measures based on ecological potential in prioritized sub-watersheds, the rate of soil erosion of all study events at the outlet of the watershed has decreased from seven to 14% and at the outlet of prioritized sub-watersheds in most storms studied varied from two to 34%. However, the land availability in late winter and early spring has increased the rate of soil erosion compared to the initial conditions in the Milan 1, Milan 2, and Gazan 1 sub-watersheds from two to six percent, which can be attributed to the low density of vegetation at the time of storms’ occurance. The results also showed that the highest rate of soil erosion reduction occurred in events with rainfall of five to eight mm and the effectiveness of management measures in the maximum storms was less than the moderate storm events.

The results of the present study showed that if the land-use pattern would be adopted at six percent of prioritized sub-watersheds, the soil erosion resulting from study storms would have been declined by 14 percent at the watershed main outlet. The findings of the current study can provide a suitable management approach for planners and policymakers to apply appropriate managerial scenarios in high-priority areas.

Sediment of eroded soils have different effect on environment based on amount of materials and elements. Nitrogen is an important nutrient that use a lot in agriculture and excessive use of this cause reduce the waters quality.

This project aim is measurement and comparison of soil nitrogen pollution in different land use and relation between each land use drainage pollution when weather is rainy in area of Bostankar river that is located in Shirod city one of the functions of Tonekabon of Mazandaran province. Because of this, soil was sampled from six land use; forest, Orange garden, Kiwi garden, Flower garden, Rice and Tea farms at winter and spring. Then, a water sample was taken from these lands' drainages. Eventually, for checking of Bostankar river situation, water samples wat also taken at 15 points along the river. Amount of total nitrogen, soluble and clinging were measured at water and soil samples.

Results showed that nitrogen amount in drainages at spring were increased than winter, that reason of this matter can be agriculture activities like fertilization and tillage in this period of time. Maximum and minimum nitrogen amount in spring relate to Flower garden and forest, equal 6.60 and 0.30 mg/lit, respectively.

For controlling the nitrogen output and nitrogen pollution at area of study soil, amount of nitrogen fertilizer use should be based on plant need and soil test result.

Introduction and Objetive:

 Estimating the suspended sediment load of hydrometric stations in the watershed requires an accurate understanding of the spatial and temporal variations of the sediment regime. Simultaneous changes and impressability of discharge and sediment from precipitation changes are of mouch importance that rarely considered. Therefore, the aim of tis study was exploring the changes in the slope of the trend curve and also the graphical correlation of monthly and annual data of runoff, sediment values to precipitation values. Toward this, six stations including Atashgah, Pulsoltani, Nayr, Amuqin, Villadergh and Nooran located in the foothills of Sabalan mountain in Ardabil province were chosen and analysed over a 20-year period using the double mass curve method.Therefore, in this study, the amount of monthly and annual runoff and sediment variations in relation to precipitation values at six including Atashgah, PulSoltani, Nir, Amugin, Viladargh and Nooran river gauge stations in Sabalan Mountain, Ardabil province, were evaluated over a 20-year period using the double mass curve method.

Tworad this, the monthly mass curve, the mean monthly rainfall for the same period calculated and was plotted versus corresponding runoff data. Trend Curve Slope (STC) was used to reflect the rate of increase in runoff and sediment amounts based on rainfall or runoff, respectively.

The results of changes in runoff and sediment yield during the available period over the studied rivers showed that except for the Nir station, there were uniform sediment and runoff regime of other stations, during the studied period. Meanwhile, the Nair station had the highest amount of runoff and sediment in all the years studied. Results of double mass curves showed that Nair, Polsoltani and Atashgah stations had no trend of curve slope changes during the statistical period, the amount of sediment and runoff was proportional to precipitation in a consistent variation regime. However, changes in precipitation and runoff with respect to rainfall were observed at Villadargh and Noran stations. Also in the recorded data of Atashagh and Noran stations there is not a trend in the early years of the available data, but the Atashgah station had a decrease in 2000 and 2005 years, and a decrease has been occurred in 2007 at Noran station.

Analysis of Taylor diagrams showed that the correlation between precipitation and runoff and sediment data were in the range of zero to about 0.4. The relative similarity of runoff and sediment change coefficients can be related to the originating the rivers from snowmelt, the annual scale of analyzes, as well as the appropriate vegetation of the upland study area. According to analysis of Taylor diagram, at all stations the standard deviation of sediment data was higher than the standard deviation of flow discharge data. The standard deviation values of the sediment data at all stations are in the same range.

One of the basic measures to reach the optimal management of water resources is modeling and predicting the level of stagnation of wells. Controlling the level of stability using observation wells is considered as the main source of information to investigate hydrological stresses. By using the daily and monthly data of the wells, it is possible to check the fluctuations of the water level, and these checks are necessary for understanding the behavior of underground water resources in the long term and making any kind of management decisions. Considering the importance of predicting the groundwater level, it is important to find an appropriate method in this regard. In recent years, the use of intelligent systems for predicting the level of underground water is rapidly increasing, which is due to the ease of use and the high accuracy of these models in approximating nonlinear and complex mathematical equations. The aim of this research is to predict the level of groundwater stagnation in Bushehr plain with the help of artificial neural network models, support vector machine model and decision tree.

In the first half of the year, all the support vector machines and the decision tree were made from the hot water of Dashtestan. Also, statistical method was used to study the spatial changes of groundwater. The data of month of 50 wells in the plain aquifer was a ten-year period from 2009-2018. To evaluate the results of the mentioned models were used of RMSE, MBE and R2.

The results showed that all three methods had high accuracy in simulating water level. The artificial neural network method with a higher R2 (0.993), the lowest squared mean error (0.29) and the lowest absolute mean error (0.024) was selected as the superior method for predicting the water table. Kriging zoning showed that the groundwater level in most parts of the plain during the study period has decreased. The maximum drop is equal to 10 meters.

The results of the modeling methods and the results of the model evaluation statistics show the good performance of the models in estimating the groundwater stagnation level, but according to the comparison of the explanation coefficient of the models in this research, it was shown that the neural network method Artificial has a higher accuracy in the distribution of available data and the calculated values were less different than the observed values of the artificial neural network model compared to the other two models. In total, the results of the research showed that the artificial neural network method has a higher accuracy in estimating the level of underground water.

Flood is one of the main natural disasters that has affected different regions of the country in recent years and caused a lot of damage. Scientists have always invented different methods to know the magnitude and time of flood and to estimate the height of runoff. Rainfall-runoff models are among the useful and powerful tools in achieving flood characteristics. The purpose of this research is to calibrate and validate the HEC-HMS model as well as to simulate floods as a single event in Tajan basin.

In this study, firstly the variables of precipitation and temperature were entered into the model, then the model was calibrated based on 3 single events and its parameters were calculated. Also, the parameters of curve number (CN) and impermeable surfaces were analyzed in Geographic Information System (GIS) environment and finally based on another single event the model was validated and its accuracy was estimated. The hydrographs generated from the scenarios of the adjusted model parameters were compared with the observed hydrographs of Kordkheil station.

Calibration results showed that the simulated data has a high correlation with the observed data (R>0.9). Also, the validation results using the correlation coefficient test and Student's t test showed that the correlation coefficient of the observation and simulation discharge is equal to 0.9, which shows an acceptable significance. Sensitivity analysis of the model was performed to determine the exact value of a sensitive parameter in exchange for changes of increase and decrease of parameters by 20%. The results of the sensitivity analysis of the model showed that the parameter of the curve number and the amount of initial losses are highly sensitive, so that in the range of -20 to +20% change of the parameter of the curve number and the initial losses, respectively, the sensitivity of the model varied from -2.33 to 7.15 and from 0.79 to -0.73. On the other hand, the model simulation results showed that the best objective function for estimating flood peak flow is Percent Error Peak, which the model predicted with a difference of 0.8% peak flow at Kordkheil station. Also, the objective function of the Percent Error Volume as the best estimator for estimated the flood volume with a difference of 0.

In general, the results of the study showed that the use of the hydrological model system using the geographic information system, rainfall–runoff modelling, flood simulation and predict the peak flow and flood volume, was very efficient and the obtained results are citable. Therefore, the tested models can be used in watershed management.

People's participation in watershed development projects is an important factor in their success or failure. Therefore, in any watershed, it is necessary to identify the factors affecting the weakness of public participation. Previous studies have rarely analyzed the factors preventing people's participation. One of the most important measures that can be taken to remove barriers to the participation of local communities in watershed management projects (biological, mechanical, biomechanical, and managerial operations) is to identify, categorize and rank the factors that weaken their participation in these projects. The purpose of this study was to identify and prioritize these factors in the Ninehroud watershed of Qazvin province. A comparison was also made between the views of experts and the local community's viewpoints on the importance of these factors.

Ninehrood watershed with an area of ​​12,336 hectares is located 30 km northeast of Qazvin. Detailed-executive studies of this watershed were approved by the technical committee of the Natural Resources and Watershed Management Organization of Qazvin province in 2006 and various biological, mechanical, biomechanical, and managerial projects were implemented during the years 2009 to 2016. Identifying the factors affecting the weakness of public participation in the watershed management projects was done based on questions from experts, visits to the area, and face-to-face interviews with residents, as well as previous studies. These factors were classified into four managerial, economic, social, and educational-promotional categories which totally include 18 sub-indicators. In this study, the data collection tool was two types of questionnaires including pairwise comparisons and Likert scale questionnaires were designed and their validity was confirmed by a group of experts. In order to know the views of local communities about the importance of these factors, according to Cochran's formula, 298 samples were selected from 1323 household heads in the watershed, and questionnaires were completed. To find out the views of experts on the importance of these factors, questionnaires were also completed by 19 experts. The reliability of the questionnaires was assessed by Cronbach's alpha test. Then, the FAHP technique and Friedman test were applied respectively to prioritize the indicators and sub-indices preventing public participation in watershed management projects.

The results showed that from the perspective of both groups, managerial and economic indicators had a greater role in weak public participation than social and educational-promotional indicators. The results also indicated some differences in the importance of the sub-indices from the perspective of the two groups. From the experts' perspective, "lack of full allocation of operating funds on time" and "local and tribal disputes" with an average rank of 13.72 and 7.03 had the most and least importance respectively. This is while the watershed residents have introduced "Non-matching of proposed projects with their needs" and "lack of full allocation of operating funds on time" with an average rank of 14.96 and 3.98 as the most and the least important sub-indicators respectively. From the perspective of both groups, three sub-indicators including the lack of multipurpose projects design, the concentration of decision-making power at headquarters, and the lack of employing local laborers in project implementation (Employment), were also ranked as the first six priorities which have had more role in the weak participation of people.

In general, the results of this study showed some similarities in the views of the two groups on some of the participation barriers, but in some cases, there were significant differences. Therefore, group decision-making with the presence of local communities on watershed management projects is proposed as a way to converge the views of these two groups.

Water management in water basins is difficult due to the lack of data collection stations. Today, rainfall-runoff simulations with different models will help manage existing water resources. Therefore, using hydrological models that allow the identification and management of the basin with minimal data can be a suitable method.

In this study, in order to simulate runoff caused by rainfall and to investigate the mechanism of runoff formation and outflow in the catchment area of the Shahid Rajaei Dam, located in Sari, the HBV-light model with existing data from 1981 to 2015 was used. Its performance was also evaluated under climate change conditions with two scenarios of RCP2.6 and RCP8.5 in the two time periods of near future (2016-2040) and distant future (2041-2065).

The results showed that the increase in temperature in the two scenarios of RCP2.6 and RCP8.5 by 11.5 and 13.9% in the near future and 13.9 and 24.2% in the distant future, respectively. Rainfall in the two climate scenarios RCP2.6 and RCP8.5 will also decrease by about 58% in the distant and near future. The output results of the model showed that the effect of climate scenarios on peak discharges will increase in the near future (2016-2040) and decrease in the distant future (2041-2065). The difference between the mean peak discharges in the future time window compared to the base period was significant at the 95% confidence level (Kruskal-Walli’s test). RCP2.6 and RCP8.5 will increase by 36% and 28% in the near future and decrease by 12% and 3% in the near future, respectively. These changes in peak discharges will increase the probability of occurrence of extreme phenomena (severe peak discharges) due to changes in the statistical distribution.

In general, these results indicate that the management, operation and maintenance of water resources accumulated at the site of the Shahid Rajaei Dam will face serious challenges. Therefore, it is suggested to apply advanced leading scenarios in catchment management while examining more closely and comparing with the results of other hydrological models.

In the northern provinces of Iran, especially Mazandaran, Gilan and Golestan provinces, the percentage of landslides is relatively high due to the construction of forest roads. Considering the importance of road maintenance projects during the implementation of the forest respiration plan, it’s necessary to zoning areas suseptble to landslides. Given that the effects of the forest respiration plan were not studied; in this study we investigate the effect of respiration plan on the maintenance projects of forest roads. The purpose of this study is landslide hazard zoning around forest roads by considering the ground control points (GCPs) and modeling the factors affecting the occurrence of landslides around forest roads.

Darabkola forest in the southeast of Sari was selected for this study. First, the factors affecting the occurrence of landslides were identified in the region. Then the layers of slope, slope direction, road network, soil and buffer of distance from road, fault lines and waterways was prepared using the QGIS 3.61 software. Also, GCPs from area suseptble to landslide as well as recently occurred landslides were recorded separately using the GPS device and then digitized in QGIS environment. Prioritization was performed using the analytical hierarchy process (AHP) and after applying the weight of the layers and reclassification, the final zoning map was obtained.

According to the results, 29.71 and 35.28% of the area have very low and low risk of landslides, respectively. Also, 21.75% of the area has a medium risk, 10.89% of the area equivalent to 289 hectares has a high risk and 2.37% of the area which is equivalent to about 63 hectares of the area has a very high risk of landslides. The results of accuracy of landslide zoning showed that from 29 points recorded as ground control points, 22 of them are located in areas with high and very high landslide risk and only 4 of them are located in areas with moderate landslide risk. Therefore, the results of zoning are consistent with the ground reality with high accuracy and showed less efficiency in only 3 cases. In Darabkola forest, due to the presence of marl bedrock and lack of drainage, several shallow landslides with distances of less than 200 meters along the road have been recorded, which are developing due to lack of management. Also, most of the landslides in the study area observed at a distance of less than 200 meters from waterways. Field visits show that most recorded landslides observed in areas where the road crosses along valleys and or intersects the valleys and due to lack of drainage, it causes multiple landslide along the road.

This study showed that zoning confirms the ground realities. Accoeding to the intersection of roads and waterways in the valleys, Darabkola forest roads need projects related to soil and water conservation. It seems that improving the road drainage and using soil bioengineering methods can help to improve road maintainance and vegetation cover in landslide area.

One of the most important challenges in recent years is the issue of climate change and its effects on water resources, which is considered one of the main areas of research around the world. Two obvious signs of climate change are changes in the mean and extreme values of climate variables that can increase the Probability of flood occurrence. Therefore, it is necessary to study the effect of climate change on floods in the future.

In this study, using the observed daily data of precipitation and temperature in the period 1961-2005 synoptic and climatological stations inside and around the Bakhtiary catchment, the effect of climate change was investigated. To predict future precipitation and temperature, the data of the canESM2 general circulation model under RC 2.6 and RCP 8.5 scenarios for climate variables for the period 2006 to 2100 were used. The effective criteria in downscaling were selected according to the correlation between the predictor and predictands variables from the NCEP-NCAR reanalysis database. Then the MORDOR-SD semi-distributed models were used to evaluate the effects of climate change on runoff. This model was calibrated and validated using daily rainfall, temperature, and observation data at Tang-e-Panj Bakhtiary station for the period 1976-2006. Applying the results of changes in precipitation and temperature data obtained from the SDSM model under the two scenarios mentioned and reproducing them in large numbers by nonparametric bootstrap method and replacing the resulting maximum daily events in the hydrological model to achieve maximum daily flood and probability made it possible. At the end of the simulation and calculation of the cumulative distribution function (CDF) of the simulated events, the maximum daily discharge values in different return periods were calculated.

The results showed that, temperature and precipitation parameters under RCP 2.6 and RCP 8.5 scenarios with average evaluation criteria MAE = 1.29, RMSE = 1.96 and NASH = 0.56 for precipitation decreased by an average of 5.4 to 11% compared to the base period for temperature with evaluation criteria of MAE= 2.27, RMSE= 2.71 and NASH 0.92 = from 6.5 to 10.4% increase compared to the base period. The results of the Nash-Sutcliffe and Kling-Gupta evaluation criteria are 0.76 and 0.83, respectively, which shows the acceptable ability of the hydrological model in the simulation. The results of the study showed that the maximum daily discharges simulated using scenario 8.5 in different return periods show higher values than the maximum daily discharges in scenario 2.6 but there is no significant change compared to the maximum daily data in the base period.

In general, it can be said that the use of climate data in the future for planning in the field of integrated water resources management and prevention of natural hazards such as extreme floods and droughts can be a useful tool for planning managers.

In today's world, resource constraints, population growth, growing human needs and desires, and fierce competition in the global economic arena have forced countries, especially developing countries, to consider strategic planning for rangeland management in order to survive and develop economically. On the other hand, the issues related to sustainable development, over time, have become a key issue in development strategies at the national level and economic institutions and have been discussed from various angles and as a strategic model can re-engineer rangeland management. Rangelands in rural areas have an infrastructural role in their economy and pave the way for moving towards sustainable development goals. Therefore, addressing rangeland management issues is of particular importance. The purpose of this study is to analyze the challenges of rangeland management in rural settlements of Kermanshah province.

The method of this research is descriptive-analytical. In this study, field studies (questionnaires) were used to collect data. The statistical population of this study includes 29 managers with rangeland management expertise; In this study, factor analysis has been used to analyze the data. The face and content validity of the questionnaire was confirmed by the corrective opinion of university professors and experts of the University of Isfahan and after making the necessary corrections in several stages. In the present study, Cronbach's alpha method was used to assess the validity of the measurement tool

Findings showed that the challenges of rangeland management in rural settlements are very wide. The results of this study with factor analysis test showed that 44 indicators were classified into 10 factors, explaining a total of 56.96% of the total variance and the highest value with a variance of 6.77 and a specific value of 2.98 is related to the planning weakness factor and the lowest is related to the variance of 5.59 and the special value of 2.01 is related to the human barriers factor.

Many years of experience show that the most important reasons for rangeland degradation are factors such as centralization policies and the governmentalization of natural resource management and lack of attention to the role of non-governmental organizations (as a public institution), Participatory.

Ab-Bandan is a native or man-made pond in northern Iran that is used to store surface water. Secondary uses of these structures include fish farming and recreation areas. These water bodies can increase pollutants and their penetration into the aquifer, by accumulating water for a long time. Therefore, it is necessary to investigate their qualitative conditions and their impact on the ecosystem of the region.

In this study, to investigate the effect of Ab-Bandans on the aquifer, the water quality of three Ab-Bandans in Mazandaran province and the wells around them have been investigated. Wells were selected at approximately 100, 200, and 300 m distances around the Ab-Bandans. During three-month periods with an interval of 15 days, water from the Ab-Bandans and surrounding wells was sampled. The parameters of nitrate, nitrite, PH, EC, and TDS were measured to determine the water quality of the Ab-Bandan and its effect on the aquifer.

Results have shown that the water quality of Ab-Bandansis in good condition for fish farming. In agricultural use, only the pH parameter is higher than the allowable range, which is normal for Ab-Bandans and swamps. Investigation of wells' water quality also shows that their quality is favorable for drinking use - which is their most important use, and only in some wells, initial treatment is required. Qualitative comparison to evaluate the quality changes at different distances from the Ab-Bandan shows that the amount of contaminants decreases with increasing distance from the Ab-bandan. Between the second well and the third well, the changes in the parameters are about 0.5% and in the distance of 300 meters of the wells, the quality conditions of the aquifer can be considered stable and it can be stated that the Ab-Bandan no longer affects the water quality of the aquifer.

Investigations show that the quality conditions of the Ab-Bandan are in favorable condition for use in fish farming. In agricultural use, pH is higher than the permissible range, which was related to the quality conditions of the Ab-Bandan.

Drought is one of the most destructive weather events that cause great damage to human societies every year. Therefore, drought indices can indicate the natural limits of droughts. In this way, they make it possible for us to evaluate at different time and place scales. In this regard, in the present study, zoning and monitoring of meteorological drought in arid desert areas using indices (SPI, SIAP and PN) in Zahedan plain were studied.

In this study, daily rainfall data sets of operating stations in the study area were collected. Due to the low density of stations and severe limitations of data access in arid areas, five stations (refinery, FBI, Khinjak train, Pudeh Chah and meteorological department of Zahedan) were evaluated as suitable during a 30-year joint statistical period (1987-2016). The selected stations had complete time series and no statistical deficiencies during the selected statistical period. After ensuring the quality of the data by using homogeneity, random and discrete tests, the annual SPI, SIAP and PN indices of the annual time scale were extracted using DIP software and also in order to zoning the evaluated indices by distance photo interpolation method in the environment. Arc GIS was used.

By calculating the coefficient of variation from year to year during the census period (1987-2016), the minimum coefficient of variation was 88.7 and the maximum value was 208.8, it was found that Zahedan plain has irregular rainfall and high variability, which indicates the Occurrence of drought in the region. Then, by examining the three indices of SPI, SIAP and PN, it was found that the conditions of Zahedan plain based on SPI indices were 24 normal years, SIAP 25 normal years and PN 25 years of drought were weak. Also, according to all three indices, the most severe meteorological drought that occurred in Zahedan plain during 2003 was related to 2003. The values ​​of each of these indicators for 2003 are -1.49, -1.16 and 25.32, respectively. According to SPI index, during 24 years of normal statistical period, SIAP index has 25 years of normal conditions and according to PN index of Zahedan plain with 6 wet years, 12 normal years and 5 years of weak drought. The annual drought threshold for the three indices is SPI 1-, SIAP -0.25 and PN 80. In addition, monitoring of spatial variations of three indices, SPI, SIAP and PN, showed that during the statistical period, the northern half of Zahedan plain was more affected by drought. Based on the meteorological zoning maps of Zahedan plain, it was determined that based on the SPI index in the years 1999-2005 of the northeastern region, the SIAP index during the years (1987-1989, 1998-2006) of the northern and northeastern parts and based on the PN index during In the years 2003-2006, the southern and western parts of Zahedan plain had more potential in terms of continuity, frequency and severity of meteorological drought.Overall

Considering that the spatial zoning maps of drought indicate the spatial expansion and more intensity of critical zones during the 30-year statistical period studied in the present study, the identification of these vulnerable and endangered areas and The extent of this phenomenon is also necessary for the implementation of management as well as development, economic, social, environmental and agricultural planning by the government of men and policy makers.

 Evaluating the effects of watershed management measures on various components of watersheds is very important for improving the performance of actions. Accurate evaluation requires continuous and correct monitoring. While monitoring is not mostly considered in developing countries due to the high cost of its implementation. Therefore, sufficient data are not available for evaluating watershed management measures. So, the methods should be selected based on available data to achieve appropriate results. Current research is conducted to evaluate the implemented watershed management measures (mechanical, biological) since the early 2001s in Qarnaveh watershed which is one of the subbasins of Gorganrood river great catchment using analysis of available data by different approaches.

In order to investigate the effect of climatic and environmental components on erosion and sedimentation, temporal changes of land use and precipitation were assessed in the study period. Due to the importance of investigating local effects of measures, their impact on erosion was investigated using satellite images before and after construction of checkdams. Then, the changing points were identified using recorded suspended load in Tamar station and sequential Mann Kendall approach. Then the amount of erosion and sedimentation for defined study periods was estimated using RUSLE and sediment rating curve approaches.

Satellite image time series mostly showed local erosion control for upstream of checkdams. While, estimated erosion using RUSLE and sedimentation using sediment rating curve for determined study periods using sequential Mann Kendall showed increase in erosion from 36.9 to 38.8 ton per hectare per year from period of 1999-2008 to 2009-2016. Comparison of estimated sediment of Tamar station for two study periods also showed an increase in sedimentation.

Although watershed management operation has had positive local effects on reducing sedimentation, the combined effects of other components such as land use and meteorological conditions resulted a relative increase in erosion and sedimentation of Qarnaveh watershed. Therefore, to evaluate the effects of watershed management measures, the spatial scale of the effects and the interaction between different components should be considered.

Intensity, duration, and type of precipitation are among the data that are very important in creating floods. Heavy precipitation that turns into runoff can cause floods and catastrophic consequences. If the highest precipitation that causes flood is calculated, it can be used to reduce the destructive effects of the flood. The probable maximum precipitation during the current century compared to the past has increased significantly due to climate change. Estimation of this parameter is very important and is usually used for engineering applications and estimating the probable maximum flood.

In this study, the estimation of the probable maximum precipitation of the Talar basin in Mazandaran province was studied by the synoptic method. Precipitation statistics of regional stations and the IDW method were used to draw rainfall maps.

The Zirab station with 245.5 mm recorded the highest rainfall in 7 days and was identified as the center of precipitation. Using dew point temperature and wind speed, the storm maximization coefficient was calculated to be 76.1 and the maximum probable precipitation for a duration of one to seven days was obtained, which on average the rate of increase in precipitation according to the maximum probable precipitation is 75.96%. Examination of sea level maps and 500 hPa level in the storm of March 17, 2017, shows that a low height is located in Iran, the axis of trough starts from the east of the Black Sea and continues to the center of Iran and in the west, it can be seen on the high Black Sea. Its ridge axis starts from the north of the Blacking Sea and extends to the southeast of the Mediterranean. The trough with very strong vorticity and a strong ridge next to it formed a Blocking.

Deployment of the Blocking and the embedment of short waves in front of the trough added to the unstable weather conditions in the area. The low-pressure system in northwestern Europe crossed the Black Sea and western Iran, then entered the southern shores of the Caspian Sea. Deployment of low dynamic pressure on the Caspian Sea Moisture fluid from the sea to the study area increased the precipitation system. As a result, the relative humidity of the northern coasts of the country reached 90% on March 17 and 18, and in the design of hydraulic structures, emphasizing this storm, the maximum possible rainfall of 4 to 6 days should be considered, which was estimated stronger than other continuities.

 Dam failure and release of stored water behind the dam is one of the most important issues in dam design and it is necessary to pay attention to its occurrence and consequences. Therefore, policymakers and planners are obliged to take measures to prevent the possible dangers of breaking the dams. Among these measures, we can mention the creation of a retaining wall in the path of flood flow due to the failure of dams.

In the present study, the construction of a retaining wall in the flood flow path due to the failure of the Ghare Aghach earth dam at different distances and scenarios has been investigated. Parameters due to dam failure were determined using the BREACH model and then its information was entered into HEC-RAS software.

If the hole is created at the level of 2451 meters from the body, 18 of the 50 sections examined will collide from the right bank or the left bank, or both. At a distance of 300 meters from the dam, the water flow at a height of 1.74 meters from the right and the water flow at a height of 2.55 meters from the left shore collide. At a distance of 2200 meters from the dam, the water flows at a height of 5.15 meters from the right bank and at a height of 0.51 meters from the left bank. At a distance of 3,000 meters from the river, water rises to a height of 3.39 meters from the left side. At 3100 meters from the dam, the water flows to a height of 2.68 meters from the left bank. At a distance of 4400 meters from the river, water at a height of 1.19 meters from the right bank collides. Finally, section 4700 of the water river attacks at a height of 3.48 meters from the right bank. However, if a hole is created at the level of 2446 meters from the body of the dam, 15 of the 50 sections examined will be attacked from the right or the left bank, or both. Therefore, in this case, at a distance of 300 meters from the dam, water flows to a height of 0.8 meters from the right bank and also water flows to a height of 2.21 meters from the left bank. At a distance of 2200 meters from the dam, water flows at a height of 4.21 meters from the right shore. At a distance of 3000 meters from the dam, the water flow at a height of 2.86 meters from the left bank. At 3100 meters from the dam, water flows at a height of 2.23 meters from the left bank. At a distance of 4400 meters from the river, water at a height of 0.9 meters from the right bank collides. Finally, at a distance of 4700 meters from the location of the dam, the water flow at a height of 2.97 meters from the right shore collides.

Areas with higher probability of flooding and with priority to the construction of a retaining wall were identified. The failure of the dam at level 2451 compared to level 2446 will cause flooding of more sections on the sides of Mehrgerd river. Among the sections studied, the most water flows attack at a distance of 2200 meters and is related to the time when a hole is created at the level of 2451 meters from the body of the dam, which due to its critical location is more important than other sections and the need to construct The wall is a barrier.

Desertification is a complex socio-economic issue resulting from the interaction of several factors. This phenomenon is always in uncertain environments and is strongly influenced by vague and implicit judgments. Therefore, the use of multi-criteria fuzzy decision-making mechanisms seems necessary in evaluating desertification strategies. On the other hand, often the input data to these devices are inaccurate and variable. So, performing sensitivity analysis on output data is an important step in such evaluations. The aim of this study was to analyze the sensitivity of priority strategies in the Yazd-Khezrabad sub-catchment in central Iran.

In order to achieve this goal, first in the framework of fuzzy multi-criteria decision-making method and with using triangular number, fuzzy pairwise comparison decision matrix was formed and the initial priority of strategies was estimated. Then the sensitivity analysis process was performed separately on the criteria and strategies in the framework of the Triantaphyllou-sensitivity analysis model. Following the determination of the most sensitive criteria and strategy, new weights of criteria and strategies were replaced based on the most sensitive criteria and strategy in the decision matrix. By calculating the weighted average of each row of the modified normalized matrix, the degree of preference or final weight of the strategies was estimated.

The results showed that the adjustment strategy in groundwater abstraction (A31) is still considered as the most important strategy as the initial results with a degree of preference of 92.9%. While the ranking of other strategies has undergone serious changes.

It is concluded that according to the mentioned macro strategy, the process of desertification can be slowed down and the destroyed areas revived by implementing aquifer projects, improving irrigation methods, land improvement, controlling the growth of industries and aquaculture crops.

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.

Soil is one of the most important national assets of any country. Since the effects of aggregate detachment and formation of surface sealing on increasing flood fertility, reducing soil fertility and increasing erosion is an important issue, the aim of this study was to investigate the role of surface sealing in sediment concentration and soil loss.

The present study was performed on two loamy-sandy and loamy-sandy-clay soil textures under the influence of three rainfall sequences with intensities of 50 and 90 mm h-1 and duration of 15 minutes at the intervals of 10 days in small erosion plots with dimensions of 0.5×0.5 m with a slope of 18%. Also, two weighted average indices of the diameter of soil grains and a three-dimensional scanner with an accuracy of 20 micrometers were used to measure the surface coating.

The results showed that rainfall sequence had a significant effect (p<0.01) on sediment concentration and soil loss. As a result of the sequence of rainfall, the loss of soil in the loamy-sandy texture increased by about 45% in the rainfall intensity of 50 mm h-1, while it decreased by 38% in the rainfall intensity of mm h-1, and in the loamy-sandy-clay texture respectively Rainfalls of 50 and 90 mm h-1 reduced soil loss by 5 and 67%, respectively. Sediment concentration also decreased after rainfall sequences. The results of measuring soil loss showed that, except in loamy-sandy texture at an intensity of 50 mm h-1, in both soils, the amount of soil loss decreased from the first rainfall to the third rainfall. The results of three-dimensional scanner at rainfall intensity of 50 mm h-1 showed that the soil surface roughness in loamy-sandy texture decreased from 1.30 to 1.18 mm and in loamy-sandy-clay texture decreased from 1.80 to 1.31 mm, but at rainfall intensity of 90 mm h-1, the soil surface roughness increased and the formation of surface sealing was prevented.

The results showed that soil surface roughness and surface sealing resulting from previous rainfall can change soil surface conditions and runoff and soil loss at the plot scale and the intensity of these changes is under the interaction of rainfall intensity and soil texture.