جستجوی مقالات مرتبط با کلیدواژه « Watershed Management » در نشریات گروه « جغرافیا »

 Saqezchi-Chay watershed is important because of suitable ecological factors, high plant and animal production, and a water reservoir dam in the outlet part of this watershed. However, it is heavily used, overgrazed, and degraded. Therefore, this research aimed to locate different watershed management operations using a multi-criteria approach and compare AHP and ANP decision support methods in the geographic information system environment at the level of the Saqezchi-Chay watershed.

 The research criteria and sub-criteria include soil (depth and texture), climate (climate type and precipitation amount), land use and Normalized Difference Vegetation Index (NDVI), hydrological factors and soil protection (sedimentation rate, and curve number), topography (elevation, slope, and aspect), and economic and social (distance from the village, distance from the road and distance from the spring) were selected. Expert judgments for weighting were collected through a questionnaire in the field with a statistical population of 29 experts and academic staff members.

 The results of this research showed that the spatial prioritization of planting and pitting operations by the ANP method has a significant correlation with the AHP method at the 95% level and with an intensity of 0.937 and 0.957, respectively.

 According to the field visit and the evaluation of the success of the executive operations in the watershed, the ANP method prioritizes more accuracy and resolution due to its network nature and increasing the range of changes.

Innovation:

 In this research, an attempt has been made to develop a new operational framework for extracting and introducing different watershed projects based on information-based methods and mapping and using the AHP and ANP frameworks by removing expert opinions (especially when the expert does not have enough experience) to choose the best project in the best place.

Soil erosion in Iran is one of the most important problems of drainage basins that can be mentioned as main barriers to the sustainable development of agriculture, geoscience, and natural resources. Therefore, soil erosion control is one of the most urgent environmental issues which need to identify in erosion-prone areas in the watersheds. In many watersheds, the role of land use in soil erosion is greater than of other factors. Knowing the contribution of different types of land use to soil erosion leads to managing land use and reducing the severity of soil erosion, and even increasing the income of the watershed stakeholders. Evaluation and identification of soil erosion in coastal regions are one of the most important measures for comprehensive coastal management. Therefore, the current research was carried out with the aim of estimating soil erosion in different temporal and spatial scales with the G2 model, according to the land use/land covers of the Caspian Sea basin.

The northern region of Iran encompasses the Caspian Sea basin, which spans approximately 91,176 km2, equivalent to around 10% of the country’s total area. It is situated between latitudes 45°39'-35'N and longitudes 59°59'-44'E. With an average elevation of 1,195 m, the watershed exhibits significant variation, ranging from the highest point at Mount Damavand with an elevation of 5,699 m to the lowest point along the Caspian Sea coast at -28 m. The Caspian Sea basin is divided into seven primary basins and further subdivided into 108 sub-basins using the Strahler stream ordering method. In order to prepare soil erosion map in the study area, the input factors of G2 model were prepared in appropriate spatial and temporal scales using meteorological data, satellite images, application of GIS and RS. The G2 model combines five input erosion parameters in a multiplicative equation to produce month-time step maps and statistics of soil erosion. Ideally, a single layer suffices for S, T, and L factors, while a collection of 12 layers (one for each month) is required for the dynamic factors R and V. Also, the values of soil erosion were estimated for different types of land uses/covers in different time scales for the Caspian Sea basin.

The results showed that the average annual soil erosion for the study area is reported to be 11.24 t ha-1, the highest soil erosion rates observed in the West Azarbaijan, Mazandaran, North Khorasan, and East Azarbaijan provinces. On the other hand, the highest monthly soil erosion with the rates of 1.49, 1.48, 1.32, and 1.27 t ha-l were in November, October, April and May, and the lowest monthly soil erosion with the rates of 0.54 and 0.59 t ha-1 were in August and December, respectively. The highest amount of soil erosion occurred in autumn and spring compared to winter and summer. One of the reasons for the increase in soil erosion in the autumn season is the high intensity of rainstorms that occur in lands with little vegetation and in the spring season, may be due to the increase in rainfall and snow melting in this season and its effect on the increase of soil erodibility. Also, minimal soil erosion in summer and winter seasons can be caused by the decrease in the amount and intensity of rainfall or the absence of effective rainfall. In addition, it was found that with the increase of rainfall erosivity, soil erosion increased on a monthly time scale. The highest annual soil erosion with the rates of 16.87, 15.96, 11.51, and 11.22 t ha-1 were in rangeland, shrubland, barren lands and forest II, respectively. As a result, annual soil erosion values in the western, central, and eastern parts were estimated equal to 11.94, 13.47, and 10.53 t ha-1, respectively. Although the difference of soil erosion in monthly, seasonal and annual time scales in all different land use/land covers is significant at the 99% level, but it is not significant in a number of large land use/land covers in the Caspian Sea basin in the western-central, central-eastern and western-eastern parts.

According to the current research, 40.53% of the lands in the studied area have soil erosion of less than 1 t ha-1 yr-1, which are in the range of low erosion, because this amount of wastage is almost equal to the annual soil construction limit and is normal, and these areas do not need watershed operations and the risk of soil erosion is low. While about 18.73% of the land surface of the studied area, soil erosion exceeds 20 t ha-1 yr-1, and it is recommended that in these areas, in addition to biological operations, mechanical operations are also performed to reduce and control soil erosion. The results obtained from the present research provide managers and policymakers with information and appropriate decision-making bases for the management and sustainable use of soil and water resources.

 This research investigates the effectiveness of watershed management activities carried out in the Badkash watershed. 

 All the watershed measures carried out in the area were visited. In connection with biological and biomechanical operations, the NDVI index was compared twice before and after the watershed operation to investigate vegetation changes. The comparison of erosion and sedimentation before and after the operation was carried out using the estimated model of preliminary studies (MPSIAC), and the effectiveness and efficiency of watershed operations on erosion and sedimentation, flood, and vegetation were investigated. 

 Measures taken in the area can trap sediments of about 7518733 cubic meters; of this tank volume, about 5754910 cubic meters have been trapped by the sediments brought upstream of the basin. The rate of specific erosion has increased from 8.74 tons per hectare to 7.46 tons per hectare, and the amount of sedimentation has also decreased significantly. Two areas of 200 and 58 hectares of the basin lands have also been subjected to the biomechanical operation of catchment crescents, and biological mounding operations have also been carried out inside the catchment crescents. 

 The results show that the temporal changes of the NDVI index for the entire area have a positive trend, and since 2018, with the implementation of biomechanical operations in the desired area, the value of this index has increased compared to the long-term average of the entire area.

Innovation: 

Until now, the evaluation of the effects of watershed management measures has been done less. Examining the effectiveness of these measures can help to continue these measures or change how they are implemented. This can help attract the attention of watershed decision-makers in the direction of investment.

During the recent decades, the loss of water and soil resources in watersheds due to their inappropriate exploitation has become increasingly intense, this issue has reduced the production and useful life of reservoirs and increased the amount of sediment production. Today, with the advancement of technology, examining the impact of projects by measuring the effective parameters and studying how to achieve the goals are part of the basic principles of project evaluation. In this study, according to the implemented mechanical and biological operations, the role of watershed operations in controlling erosion and sedimentation in the Saqezchi-chay watershed of Ardabil province was investigated and compared using the MPSIAC method before and after the operation. In this model, 9 effective factors in erosion have been considered, each of which has a score depending on its intensity and weakness, and finally, taking these scores into account, the sedimentation rate of the area is considered. The results of the research show a relative decrease in erosion and sedimentation in the area of watershed operations and, on the other hand, an increase in erosion and sedimentation in other areas without watershed operations, which indicates the positive effect of watershed operations in increasing vegetation and soil protection. Also, the implemented watershed management measures, in addition to increasing the concentration time in the watershed and groundwater feeding, have played an important role in preventing the reduction of the storage volume of the Saqezachi dam. The results indicate the effectiveness of watershed projects in reducing sedimentation in the study area; In such a way that the amount of erosion in the watershed has changed significantly.

Prioritization of Flood Risk in Ganjvan Watershed of Ilam Province Using ELECTRE MODELToday, environmental hazards and dealing with them is one of the most important concerns of researchers in the field of environmental planning and crisis management. Among these hazards, the phenomenon of flood is one of the most dangerous natural disasters that should be given special attention in crisis management. Therefore, prioritizing sub-basins for watershed management operations with a view to flood control and control seems necessary. In this research, an attempt has been made to prioritize the Ganjvan watershed basins in Ilam province to implement flood control management plans against floods using the multi-criteria Electre decision-making method. For this purpose, the studied watershed was divided into five sub-basins of Rizevand, Sarcham Deh Haroon, Sarpetak, Sartang Bijar and Ganjvan. Criteria for prioritization include lithology, slope, height, precipitation, land use and drainage density. The weights of the criteria were obtained based on their entropy model and using the Electre model of watershed sub-basins in the prioritization area, the study and then the prioritization map of these sub-basins was prepared. Flood risk prioritization map in the study area shows that Ganjvan sub-basin with the highest flood potential has the first priority and Sartang Bijar sub-basin in the second priority to implement flood control watershed management plans.The method used in this research can be a practical method to study and implement watershed management operations and flood control in the studied watershed and similar to this basin can be used. By performing watershed management and flood control operations in sub-basins located at the mentioned levels, in accordance with the priorities set by this method, while achieving the desired goals, it can have a direct impact on reducing the executive costs of projects.

Researches in recent years have shown that the implementation of watershed management projects without the participation of the public has not been successful and has led to the inefficiency of projects in watershedchr('39')s protection. In order to solve this problem, prioritizing the indexes and sub-indexes affecting the non-participation of people is a fundamental step in the watershed management cycle, so that identifying the effective factors and prioritizing them will lead to maximum participation of the watershed residents. According to this goal, in this research, prioritization of effective factors was done on non-participation in watershed management projects from the exploiters viewpoint in Chikan and Morzian Sepidan watershed located in northwest of Fars province. The statistical population of this research was 51 exploiters (stakeholders) using Cochran formula. A questionnaire consisting of four indices and twelve sub-indices with Likert scale was used for data collection. The significance of indices and sub-indices was determined by SPSS software (version 23) using t-test and the Friedman nonparametric test was used to prioritize the effective indices and sub-indices. The results showed that in the prioritization of indicators from the beneficiarychr('39')s point of view "economic", "social", "educational-promotion" and "design-executive" indices were the effective factors, respectively and in sub-index "lack of training of basin residents on related plans and objectives" and "lack of attention to Non-Governmental Organizations (NGO) in watershed planning", had the highest and lowest priority in non-participation in watershed planning, respectively. In order to sustainable participation of exploiters in watershed management projects, it is necessary to solve the "economic" problems of beneficiaries and develop a comprehensive program of training and promotion of practical actions.

Different natural phenomena have many variables that make it difficult to find relations among them using common mathematical methods. This problem, along with the impossibility of measuring all elements of nature, has led to a major evolution in the procedure of scrutinizing and explaining. In this way, we can use the fractal geometry with the theory that the order of many natural phenomena is chaotic. Fractal geometry is a quantitative tool for studying the geomorphology of drainage networks and modeling many complex natural phenomena. In fact, geophysical phenomena such as basins are fractal phenomena with fractal behavior. An understanding of geomorphologic characteristics and their performance over basins is very important in the watershed management. This paper focuses on the relationship between fractal dimensions of basin shape and drainage network with the geomorphologic characteristics of basin. Therefore, through an analysis of fractal dimensions and its comparison with geomorphologic characteristics, the fractal behavior of this basin is investigated.

The present study consists of four main sections. The first section is the collection of maps and data. In this section, topographic maps at scale of 1:50000 and geological map at scale of 1:100000 from area were provided. Then, the required layers were extracted from them such as drainage networks and geological units. Sensitivity to erosion of formations was studied in this basin using PSIAC method. In order to investigate more precisely, the Aqda was divided into nine hydrological sub-basins (independent), five non-hydrological sub-basins (dependent) and four hybrid sub-basins. The second section, 18 geomorphologic characteristics were calculated for each sub-basin. In the third section of this study, fractal dimension of drainage networks and basin shape was calculated by box counting method using Fractalyse software in each sub-basin. The focus of the final section is on the relationship between fractal dimensions of basin shape and drainage network with the geomorphologic characteristics of basin.

The results showed that the T8 and To3 sub-basins, respectively, with values of 1.47 and 1.60 have the highest fractal dimensions of the drainage network. Also, the highest fractal dimensions of the basin shape were obtained with values of 1.05 and 1.08, respectively, in the same sub-basins (T8 and To3). The results also indicated that there were significant relations among the fractal dimensions of the basin shape and the drainage network with geomorphologic characteristics. The highest correlation belongs to the regression relations between the total length of stream, basin area and erodible area with the fractal dimension of the drainage network (0.98, 0.97 and 0.95 respectively). Fractal dimension of the basin shape showed the highest correlation of 0.82 and 0.8 respectively with the number of networks and the total length of stream (significant at 99 percent level). Then, the erodible status in Aqda Basin was determined by studying the geomorphologic characteristics and comparing it with the fractal dimensions of the basin shape and the drainage network. The highest erodible status is in T8, T1, T6 and TO3 sub-basins which should be considered in strategies to manage Aqda basin. In fact, this study showed that fractal dimensions allow a quick and accurate analysis of the geomorphologic characteristics of the basin and the drainage network.

Identification, evaluation and prioritization of different areas can produce valuable information for the watershed comprehensive plans, soil conservation and mitigation of the erosion types based on amount of erosion and sedimentation. For this purpose, the geomorphologic characteristics should be investigated in basins. But extraction of these characteristics and estimation of the erodible status in basins are time-consuming and costly. Therefore, it is very necessary to use an index that has an appropriate estimation of the erodible status in basins. Fractal dimension, with time and cost management, can determine sensitive and high priority basins. With knowledge about the relationship between geomorphologic characteristics basins with fractal dimension, we can predict the other characteristics of basin. The results of this study indicated that there were significant relation between the geomorphic characteristics of sub-basins study and fractal dimension of the basin shape and the drainage network. Other researches on fractal dimension analysis have shown that there is a significant relation between fractal dimension and characteristics such as basin shape, area, branching ratio, drainage density and length ratio of drainage network. But in this study, two characteristics of branching ratio and length ratio of drainage network were not significantly correlated with any of the characteristics and fractal dimensions, and the drainage density was correlated only with frequency rank. Therefore, basins with high erosion will not always have high drainage density. For example, quaternary alluvial deposits have high erosion, but their drainage density is not very high (T4 sub-basin). For this reason, in the future studies, it is better to separate the tectonic streams from the erosion streams. Finally, the results of this study can confirm the findings of other researchers that fractal dimension of drainage network reflects the complexity of the basin shape and can be used as a quantitative index for basin analysis and evolution of the basin.

The most appropriate option for flood control in accordance with environmental conditions is watershed management, which has different effects on the hydrological factors, including the amount of surface runoff, sedimentation rate and the permeability in the watershed. The purpose of this study is to simulate and assess changes in surface runoff, sedimentation rate and the permeability using semi-distributed SWAT model in two periods before and after watershed management in the Anbaranchay Watershed. The results showed that the rate of sedimentation in the upstream before watershed management was 22.14 T/ha and after watershed sediment yield per hectare has decreased to 1.84T. Also, the simulation results showed that the amount of CN has changed from 75.68 to 61.24 in watershed and an increase in permeability and the flow lateral is observed. The SWAT model estimated the evapotranspiration 157.4 mm to Anbaranchay watershed. Changes in the hydrological cycle in plain sedimentary region has left the greatest impact. It seems that the SWAT model is able to simulate the hydrological cycle processes and geomorphological studies and provide valuable information.

Radical increase of soil and water resource losses of watersheds has been increasingly intensified in recent decades which is mostly due to irregular utilization of the resources, exacerbating floods, increasing sedimentation rates and reducing the useful life of reservoirs. The current study, conducted in Hajiabad watershed- Kermanshah province, aims to assess the impact of watershed management practices on runoff storage, reducing flood and flood potential. At first, field surveys were carried out, then mechanical and physical properties of constructed structures were recorded and the data were analyzed. In the next step, the impact of structures on flood and runoff control has been studied using HEC-HMS model and watershed flood simulation. According to the evaluations and frequent field visits, Hajiabad watershed has a low flood potential and most of created runoff penetrate before they reach the watershed outlet. In addition, there was no sediment accumulation indicative of the surface runoff behind constructed flood control structures in the Hajiabad watershed (soil dam, dry stone and gabion). It shows that the amount of constructed structures is much more than the area needs.

Demand increasing in water resources in Iran has been caused to water exploitation and disturbing the ground water resources balance. In Hormozgan Province that is located in arid region of Iran, there is not balance between demand and supply of water resources. Isin Watershed that is covered 47793.5 ha area, located in the northern part of Persian Gulf. In this watershed, water supply depends on groundwater resource so has been faced to loss of groundwater level that this losing grows faster and faster. In this study, after collecting information about watershed management for isin watershed, identify and analysis of natural features, various states that may happen be with watershed management or without it, has been projected. Four scenarios developed for this purpose and analysis the results show that, if watershed management will be done in the isin watershed, the amounts of infiltrated water into the groundwater will be 1.5 times more than in which time that do not any watershed management. Accordingly, with implement the watershed management and artificial recharge operations, the average of rainfall infiltration into the groundwater will be 1.72 mcm per year in dry years and 6.63 mcm per year in wet years.

Climate change in Iran and the world is considered by most scientists to be due to the emergence of “greenhouse” state that will have adverse effects on the Planet from different viewpoints. Due to human interference in climate change, undeniable climate change has been asserted in various world reports and the latest statements by the International Community, but scientific doubts also exist on reasoning behind climate change reported by “CHANGEINTERGOVERNMENTALPANELONCLIMATE”. As BRYSON (1977) states, surge from one pattern to another might change the climate of some of the mid-range-latitude areas drastically, and it is very likely to create a “drought-or-flood” pattern. The increase in temperature in some of Iran's meteorological stations indicates a tendency towards arid climate, and probably the period of climate change has begun in the country of Iran. The country, according to the research, has a pattern of a number of years of droughts alternated by a number of rainy years. Environmental problems such as global warming, frequent occurrence of droughts, expansion of deserts and the increasing trend of desertification, increasing number of forbidden areas for the extraction of water and occurrence of destructive floods have caused ecological instability in the country and have increased the vulnerability of the country's natural resources.