Hossein Karimi; Amir Lakzian; Gholamhossein Haghnia; Hojat Emami; Majid Soufi
Abstract
In the past decades, the study of soil erosion has gained considerable attention by many researchers. This was thorough understanding of soil erosion processes and variable factors affecting it which is essential for making land management decisions. The aim of this study was to investigate the spatial-temporal ...
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In the past decades, the study of soil erosion has gained considerable attention by many researchers. This was thorough understanding of soil erosion processes and variable factors affecting it which is essential for making land management decisions. The aim of this study was to investigate the spatial-temporal coefficient of variation of soil erosion and flow hydraulic parameters in top-down conventional ploughing rills with 20 percent average slope. The artificial rills were produced with a length of 10, 20 and 30 meters. Hydraulic parameters and sediment concentration were measured at three equal time and distance intervals after applying 10, 15 and 20 Lmin-1 inflow rates for 10 minutes. Consequently, sediment detachment and transport rates were calculated. In addition, relative errors (RE) of these parameters were calculated in order to investigate the coefficient of variations. The results showed that there was a significant difference (P<0.01) between sediment (soil detachment rate, transport rate and sediment concentration) and hydraulic parameters. Stream power was significantly different with sediment detachment and transport rates (P<0.05). Temporal evaluation revealed that coefficient of variations in the first and final time intervals of RE values of detachment and transport rates were more than middle time slot. This is perhaps due to stochastically movement of available sediment in the first step and undercutting and bank failure of rills in final stage. Spatial variability showed that the RE in the primary section is significantly (P<0.01) greater than following sections, whereas there was no significant difference between second and third sections.
Heshmatolah Agharazi; Aliakbar Davudirad; Mahdi Mardian; Majid Soufi
Abstract
Recognition of effective processes of erosion, especially, threshold is one of the most important strategies in water and soil resources management. Gully erosion is one of the most important sources of sediment yield in watersheds that is defined as different thresholds like area-slope or topography. ...
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Recognition of effective processes of erosion, especially, threshold is one of the most important strategies in water and soil resources management. Gully erosion is one of the most important sources of sediment yield in watersheds that is defined as different thresholds like area-slope or topography. In this paper, the area- slope threshold was investigated in Zahirabad Watershed in Markazi province, Iran. First, based on field surveys and digital elevation model, morphometric characteristics of 14 gullies were measured, accompanied by soil sampling and vegetation cover measurements. Second, homogeneous groups of gullies were defined by factor and cluster analysis and power relations of area-slope was prepared. Results demonstrated that there was no considerable correlation between area and slope of gully watersheds. So, coefficient of determination of creation point and head-cut of gullies were 0.111 and 0.181, respectively. According to the results, the dominant process in creation and head cut development of gullies in Zahirabad was related to flow concentration and rill erosion of high slopes. Considering the prevail of loamy texture of soils land use changes and deterioration of vegetation cover, it is suggested to investigate the optimization of land use schemas, and land cover improvement on sloppy lands with the objective of gully control.
Rahim Kazemi; Hamid Davoudi; Mohammad Jafar Soltani; Amir Sarreshtehdari
Abstract
There are more than 5.5 million date palms in Bushehr province in southern Iran. Repeated droughts and lack of irrigation water in recent years are being the most important factors for yield reduction and low quality of date fruits. Proper utilization of water supplies in order to increase water use ...
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There are more than 5.5 million date palms in Bushehr province in southern Iran. Repeated droughts and lack of irrigation water in recent years are being the most important factors for yield reduction and low quality of date fruits. Proper utilization of water supplies in order to increase water use efficiency and also, identification of more tolerant plants are so sensed according to recent drought crisis in the region. Although, date palm can suffer water shortage for a long time but higher water levels and annual soil temperature between 17 to 45 centigrade degrees would make the highest production. Therefore, a study was conducted in Bushehr Agricultural Research Center to determine the responses of three date palm cultivars of Kabkab, Zahidi and Shahabi to deficit irrigation. This experiment was carried out on randomized complete block design with three replications during 2004 to 2007. The irrigation treatments of this study were water depth in four levels of 35, 50 and 65 percent of irrigation water, which shows the cumulative evaporation of class A pan. Irrigation water was offered to plants under pressured system. Tree responses were evaluated in each year for the following properties: fruits and seeds weight, length and diameter, pulp to seed ratio, TSS, pH and yield. Results showed that cultivar effect was significant in all date palm responses (p>0.01) which can prove different inherent qualitative and quantitative characteristics in date palm cultivars. Zahidi cultivar proved to have higher water use efficiency in water stress conditions during drought periods. Irrigation treatments affected only the yield responses. Although, 65 percent of irrigation water showed to have higher production abut it was classified in the same statistical class with 50 percent of irrigation water. This means that in the situation of water shortage, 50 percent of irrigation water would be the choice. Also, mean water usage during three years of the experiment were 5497, 7758 and 9822 m3 ha-1 per year in the irrigation treatments with 0.544, 0.481 and 0.409 kg m-3 water use efficiency respectively. The sequence of water stress toleration in three date palms was Zahidi > Shahabi > Kabkab.
Majid Mahmoodabadi; Elham Sirjani
Abstract
Soil erosion is a dynamic process with high variability in sediment size distribution. Dynamic recognition of sediment size distribution is as a base for modeling of soil erodibility and movement of nutrients, pollutants and fine particles in consequence of erosion. This study focused on sediment transport ...
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Soil erosion is a dynamic process with high variability in sediment size distribution. Dynamic recognition of sediment size distribution is as a base for modeling of soil erodibility and movement of nutrients, pollutants and fine particles in consequence of erosion. This study focused on sediment transport mechanisms due to sheet erosion on two different soils (cropland and sandy) using flume experiment. The experiment was performed applying different flume slopes (1.5 and 2 %) and flow rates (75, 100, 125, 150, 175 and 200 ml/s). The result showed that hydraulic condition as well as soil type, played an important role in selective transport of sediment particles so that, in the sediment size distribution of cropland soil two peaks were observed. For the first (fine particles with size of 0.042 mm), the dominant transport mechanism was attributed to suspension- saltation, while for the second peak (large particles with diameter of 1.5 mm), bed load was known as the main transport mechanism. Moreover, increasing stream power, the selectivity of fine particles declined therefore, both fine and large particles were transported by the flow. For sandy soil, only one peak for the range of 0.109 to 0.175 mm was observed. In this soil, saltation was the main mechanism in transporting sediment. Increasing flow rate, the frequency of particles smaller than 0.015 diminished, whereas particles larger than 0.218 mm increased. For both soils at higher stream powers, the relative importance of transport as suspension and bed load decreased and increased, respectively. The findings of this research reveal that sediment size distribution and also transport mechanisms depend on hydraulic condition such as slope and flow rate.
Mohammad Ebrahim Banihabib; Ehsan Emami
Abstract
Sediment yield of watersheds is considered as a problem of water resources management and operation. Considering important role of sedimentation, accurate measurement and estimation of it is important for national investment in water resources development. Accuracy of sediment yield estimation depends ...
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Sediment yield of watersheds is considered as a problem of water resources management and operation. Considering important role of sedimentation, accurate measurement and estimation of it is important for national investment in water resources development. Accuracy of sediment yield estimation depends on the estimation methods. There are different parameters affectingt sediment yield. These parameters should be considered in simulation of sediment yield. An artificial neural network model is used for estimation of sediment yield in this research. The model with proper structure and sufficient data is trained and tested and it can recognize the relation of the parameters and sediment yield. The proper structure is found to be MLP. The result of the model is compared with a regional analysis model and it shows notable increasing of accuracy by the artificial neural network model.
Ataollah Kademorasoul; Mostafa Chorom
Volume 1, Issue 1 , May 2009, , Pages 1-8
Abstract
Water resources management is one of the most important environment challenges in watersheds. Loosing of soil caused by water erosion is one of dominant geographic processes over the most lands of the world. Nowadays, the feasibility of using mathematics models and advancement software technology has ...
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Water resources management is one of the most important environment challenges in watersheds. Loosing of soil caused by water erosion is one of dominant geographic processes over the most lands of the world. Nowadays, the feasibility of using mathematics models and advancement software technology has made available the quick recognition of erosion and sedimentation processes. In this study, the model of WEPP (version 2006) was provided for simulation and forecast of erosion and sedimentation in the study watershed. The WEEP model is a deterministic model with distributed parameters. In this research, watershed of Imamzadeh Abdollah of Baghmalek which lies in north-east of Khuzestan province is studied. Creation of a climate file is made available as an input file using the model of CLIGN and software of BPCDG as well as preparation of soil, basin management file using Excel and EPIC models. All the parcels of basin were defined for the model and executed using the aerial photos, drainage map, hypsometric map and software of Arc View (version, 3.3). Outputs of the model in the erosion section indicated average soil erosion which was some 22.54 tonha-1. Also, the sediment load was about 3468.2 tons, which indicated a difference of 9 percent in comparison with measured rates. Meanwhile, outputs of the model have well provided the feasibility of distinguishing sensitive hillsides to erosion. Based on outputs and ruling management on the hillsides, the protective recommendations like the proper ways for planting and gabion covering, building traces or groins in course of taking the best management practices were accomplished.
Esmaeil Sharifi; Hossein Ali Habibi; Mohammad Namaki; Samad Shadfar
Volume 2, Issue 1 , May 2010, , Pages 1-10
Abstract
Leadership is one of four basic steps in the management process. It involves leading, influencing and motivating group or organization members and or any social structure. Investigation of leadership characteristics in watershed management which is a non-governmental social structure is of important ...
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Leadership is one of four basic steps in the management process. It involves leading, influencing and motivating group or organization members and or any social structure. Investigation of leadership characteristics in watershed management which is a non-governmental social structure is of important consideration. In this research, various theories of leadership along with integrated definition of its obligations were brought under consideration. Furthermore, various methods and styles of leadership were analyzed by exact designing about its network. Thirteen required attitudes for practicing of management were extracted and determined during this research. Nowadays, scientists believe that consultation and intermediation skills are the most important factors in non-government and social organizations since in the various research is known that economic analysis are among the isolated matters for these non-governmental social systems. Importance of getting in contact with minorities and other cultural groups, ability in resolving of wrangling and evaluation of politic conditions, and also distinguishing of social requirements have been recommended as the most important factors for management of such an organizations. In consequence of different adjusting theories and styles of leadership in various conditions of watersheds and their residents, the best of leadership options were introduced in different cases. Finally, considering the exploiting of scientific management in watershed administration, suggestion for training managers with scientific skills in post graduate studies are made for watershed management.
Mehdi Rahmani Jevinani; Rahim Kazemi; Seyed Reza Emam jomeh
Abstract
In flood water spreading site selection, Electrical resistivity tomography (ERT) plays an essential role in identification of the geological characteristics such as: depth of bedrock, thickness of the alluvial deposits, water table, fault and impermeable layer. ERT methods try to answer some of the important ...
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In flood water spreading site selection, Electrical resistivity tomography (ERT) plays an essential role in identification of the geological characteristics such as: depth of bedrock, thickness of the alluvial deposits, water table, fault and impermeable layer. ERT methods try to answer some of the important parameters for flood water spreading site selection. ERT method is based on a new approach for modeling distribution of resistivity values under different topographic condition. In this research, ERT studies were designed in a rectangular grid with three profiles in parallel, perpendicular to the channel and the average distance of 600 meters and a length of 1250 meters that covers water spreading and adjacent area. On the profiles, a total of 18 Schlumberger sounding with broadening the AB/2, 100 and 147 meters to 250 meters away from each other were considered. The exact location of the fault was determined by preparation of Two-dimensional cross sections obtained from inverse modeling that were performed with the RES2DINV software. By extraction and interpretation of data which is modeled by SURFER, ver7 and providing pseudo resistivity sections in different depth, type of fault, amount of sedimentary strata displacement and alluvium thickness were determined. By comparing the resistivity values with the existing well logs in the study area, the relative permeability of underlying layers were determined.
Seyed Hamidreza Sadeghi; Zeinab Karimi; Zahra Hashemiarian
Abstract
Annually, high amount of soil is washed out by erosion from the watershed. Implementation of appropriate management methods to control soil erosion is therefore essential. Application of economically-effective and environmentally friendly amendments to soil is one of the solutions and new technologies ...
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Annually, high amount of soil is washed out by erosion from the watershed. Implementation of appropriate management methods to control soil erosion is therefore essential. Application of economically-effective and environmentally friendly amendments to soil is one of the solutions and new technologies to control soil erosion. However, the comprehensive assessment of the impact of commonly used soil amendments on soil erosion has not been conducted. The present study therefore aimed to assess the performance of combined application of polyacrylamide powder (6 gm-2) and vermicompost (24 gm-2) in comparison with individual application of the polyacrylamide and vermicompost as well as control (without amendments) condition to control runoff and soil erosion under laboratory condition and on a clay-loamy soil. The study variables of runoff, soil loss and sediment concentrations were measured under a simulation rainfall intensity of 80 mm.h-1 and duration of 8 minutes. The results indicated a statistically significant effect (p=0.00) of all study treatments on the reduction of runoff, soil loss and sediment concentration from the study small plots. The combined effect of polyacrylamide and vermicompost on runoff and sediment concentration was also found greater than that recorded for soil loss.
Elnaz Azartaj; Ali rasoulzadeh; Ali Asghari
Abstract
Soil and water are the most valuable national resources. Unfortunately in recent decade, due to land use change and vegetation cover degradation, most of the rainfall changed into runoff and in addition to loss of this vital resource, causes abundant loss of life and property by creating enormous floods. ...
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Soil and water are the most valuable national resources. Unfortunately in recent decade, due to land use change and vegetation cover degradation, most of the rainfall changed into runoff and in addition to loss of this vital resource, causes abundant loss of life and property by creating enormous floods. The aim of this study is to assess the effect of land use change from range land to agriculture with different percent of vegetation cover on runoff and soil erosion. For this purpose, three types of land use included preserved range land with 100 percent of vegetation cover; range land with 50 percent of vegetation cover and agricultural land (range land changed to agriculture) were identified in the study area. Then, in each land use, three slopes were determined (10, 15 and 24%). This study was carried out split plot experiment based on completely randomized design. In each land use and slope, runoff and erosion were measured in plots randomly using rainfall simulator with 1.5 mm.min-1 intensity and 15 min duration with 3 replicates. Results showed that the maximum of runoff, sediment mass and sediment density were in the range land changed to agriculture with 24% slope and the minimum of them were in the preserved range land with 10% slope. Also the results showed that the change of range lands to agricultures increase runoff 5 times. In the other hand, with increasing slope from 10 percent to 24 percent, runoff increased 1.7 times. Runoff coefficient was determined for 3 land uses and 3 slopes level. The maximum and minimum runoff coefficient were found 0.72 and 0.06 for the range land changed to agriculture with 24% slope and preserved range land with 10% slope, respectively.
Mohammad Ebrahim Banihabib; Bahman Vaziri
Abstract
Since most of water and soil researches require artificial rainfall simulation, thus rainfall simulators are applied instruments in this field of study. For this reason, various rain simulators have been designed, built and employed in researches till now. Even though all rainfall simulators provide ...
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Since most of water and soil researches require artificial rainfall simulation, thus rainfall simulators are applied instruments in this field of study. For this reason, various rain simulators have been designed, built and employed in researches till now. Even though all rainfall simulators provide good simulation for rainfall intensity, but simulation of varied rainfall by them are expensive and complicated, and field study cannot conducted easily by them. Thus, in this research, in order to simulate rainfall similar to natural rain and applicable for field tests, it is aimed to design and build a simple and affordable rainfall simulator using flow cascades reservoirs (tanks) routing. The result of calibration the simulator shows it has error less than 5%. Moreover simulation of observed hyetograph of Niyavaran station showed error of 6.1%. The simulator can simulate hyetographs with 3 hours duration and 30 millimeter per hour intensity. Consequently, the proposed instrument and its numerical model can be applied for simulating artificial rainfall hyetograph in rainfall erosion and infiltration field research tests.
Elham Afrough; Masoud Masoudi; Seyed Yousef Erfanifard
Abstract
Destroying natural resources and environment is one of the most important problems in different regions around the world, especially in arid zones. So that extent areas of these zones are being destroyed in extensive spectrum of these destruction processes. For this reason, evaluating and providing vulnerability ...
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Destroying natural resources and environment is one of the most important problems in different regions around the world, especially in arid zones. So that extent areas of these zones are being destroyed in extensive spectrum of these destruction processes. For this reason, evaluating and providing vulnerability map of vegetation degradation in our country can considerably help the management and executive planning. In the present research, the criteria used in a new model called NIDLTS are proposed for evaluating the vegetation degradation. These criteria are natural index(N), human indirect index (I), human direct index (D), livestock pressure (L), trend of degradation (T) and state indicators (S). In order to estimate each criterion, a number of risk index were used. Natural indices studied in this research were climate change, draught, climate and suitability of lands. Human indices which were studied are population density, population growth, governmental expenses from executive works and researches, changing natural resources land to agricultural lands, percentage of unemployment, percentage of illiteracy. The indices of studied status are percentage of crown cover, production of the present biomass and production of the present biomass to the potential. Hazard index related to each destruction group were classified in to five classes of hazard intensity with numerical values in order to be analyzed in GIS. Then, the weight of each index and each main group of NIDLTS framework were calculated by Hierarchy Analysis Process (AHP); so that giving priority was done through investigating their share and effects in the vegetation decline. Finally, the vulnerability map of vegetation risk was generated through overlaying all the layers for each criterion in GIS. Results showed that among the human factors, the changing land use from natural resources to agriculture is the most important factor, whereas among the natural factors, drought is the most important factor in the study area. Also, among all the criteria, natural index has the highest effect and the trend of degradation of natural resources lands has the lowest effect in the vegetation degradation during the time. The final hazard map showed that the most widespread hazard class is moderate, followed by no-hazard in the region. It seems logical that the proposed model of NIDLTS for assessing the hazard of vegetation degradation can provide a more accurate estimation of vegetation degradation in a region with taking into consideration of the ecological, anthropogenic and hazard trend in comparison with some other evaluations that only consider the current state of vegetation degradation.
Naghem Navabi; Mahnoosh Moghaddasi; Naser Gangi
Abstract
Drought is a natural phenomenon that occurs in almost all parts of the world. The effects of this crawling phenomenon are more pronounced in arid and semi-arid areas due to their annual rainfall. In contrast to traditional methods based on meteorological stations observations that focus more on weather ...
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Drought is a natural phenomenon that occurs in almost all parts of the world. The effects of this crawling phenomenon are more pronounced in arid and semi-arid areas due to their annual rainfall. In contrast to traditional methods based on meteorological stations observations that focus more on weather drought, the use of remote sensing and satellite imagery as a useful tool for monitoring agricultural drought has been considered. In the present study, the aim of comparing and assessing agricultural drought monitoring in Urmia Lake basin using VCI, VHI, TCI vegetation cover indices during the years 2000 to 2011 is using Madison. For this purpose, the NDVI index was first calculated from the images of Madis during June, July, August and September. Then, by comparing the mean of this index during these months, Shahrivar was selected with the maximum value as the month of the indicator. With regard to the minimum and maximum NDVI index in the months of September 2003 and 2008, VCI, VHI, TCI dash mapping maps were prepared. In order to evaluate the performance of agricultural drought indices, correlation coefficients were calculated for VCI, VHI and TCI profiles with SPI Meteorological Index. The results showed that the remote sensing index had a good accuracy in estimating the spatial and temporal dispersion of agricultural drought, so that the correlation coefficient between the VHI and SPI index was 0.86, which indicates that the index is consistent with the SPI meteorological index.
Majid Soufi; Reza Bayat; Afshin Partovi
Abstract
Some parts of “morpho-climatic classification of Iran's gullies” national project in Soil Conservation and Watershed Management Research Institute, refer to the amount of produced sediments and reclamation measures for their management and the amount of damages resulting from their development. ...
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Some parts of “morpho-climatic classification of Iran's gullies” national project in Soil Conservation and Watershed Management Research Institute, refer to the amount of produced sediments and reclamation measures for their management and the amount of damages resulting from their development. The results of this research indicate that Iran's gullies are categorized in two classes, small (<1 m) and medium gullies (1-10 m). One meter of gully has produced 19 m3 of sediment. Generally, they are distributed in rainfed lands and rangelands with loam, sandy loam and clay loam soil textures. The most important causes of gully formation and development are rangeland destruction, rangeland change to cropland and garden, and non-proper road and culvert construction. The present research showed that more than 50% of Iranian gullies had no management and reclamation measures, so that in 90% of some provinces and 30-50% in other areas, no management measures have been taken. More mechanical measures such as loose rock dams, rock and cement dams and gabions dams with the aim of sediment trapping are taken in Iran's provinces. Most measures are taken in small gullies, but just a few in medium ones. Management measures for prevention of gully formation are negligible in rainfed lands and serious attention is recommended to be paid to the design and construction of culverts and roads in mountainous and steep areas. Biological methods, blankets and rip-rap methods are used less in Iran. Demolition and abandoned old Ab-anbars had a role in have gully formation and development.
Reza Chamani; Mehdi Vafakhah; Seyyed hamid reza Sadeghi
Abstract
Today, drought has become one of the hot topics of global concern, but its impact on the provision of services and functional health of watersheds in the face of this natural disaster has been less evaluated. Accordingly, in this study, the effect of drought on the Efin Watershed health has been evaluated ...
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Today, drought has become one of the hot topics of global concern, but its impact on the provision of services and functional health of watersheds in the face of this natural disaster has been less evaluated. Accordingly, in this study, the effect of drought on the Efin Watershed health has been evaluated based on changes in Reliability (Rel), Resilience (Res) and Vulnerability (Vul) indicators in the period 2005-2019. Based on this, the rainfall data of three rain gauge stations were interpolated using Inverse Distance Weighting (IDW) for the watershed and sub-watersheds. Standardized Precipitation Index (SPI) was then determined based on the mean and standard deviation of monthly data and was used to calculate the Rel, Res and Vul indicators. Finally, the overall health status of the watershed was determined by calculating the geometric mean of these indicators. The annual results showed that Efin Watershed in terms of Rel, Res and Vul indicators extends between 0.83-0.92, 0.17-0.33 and 0.24-0.54, respectively. The RelResVul index also has values between 0.37-0.53. The average watershed health indicator in this period was also calculated to be 0.42, which indicates mean watershed health condition. Spatial variations of watershed health also showed that Rel, Res and Vul indicators fluctuated between 0.85-0.86, 0.21-0.24 and 0.76-0.78 in different sub-watersheds. The results of rainfall analysis of the region, indicate that due to the relative stability of rainfall, the impact of human intervention and intensification of watershed health threatening factors, more than ever effect on the current situation and if not addressed will have harmful effects.
Narges Ghasemiamin; Nasim Arman; Hossein Zeinivand
Abstract
Land use and its fluctuations is one of the most important factors that affects on the natural cycle in the ecosystem. Land use changes cause change in watershed hydrological cycles, water balance between precipitation, evaporation, infiltration and runoff response. Understanding the relationship between ...
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Land use and its fluctuations is one of the most important factors that affects on the natural cycle in the ecosystem. Land use changes cause change in watershed hydrological cycles, water balance between precipitation, evaporation, infiltration and runoff response. Understanding the relationship between land use changes and its factors and secondary effects on the hydrological regime provides the necessary information for planning of land use and sustainable management of natural resources. At first, land use maps related to years of 2000 and 2014 were prepared, then CLUE-s model was applied to simulate land use map of 2025. For simulating runoff, WetSpa model was employed to simulate daily runoff with land use maps related to years of 2000, 2014 and 2025. According to the results, the Nash-Sutcliffe evaluation criterion was calculated 68.26 % and 66.75 % for the calibration and validation periods, respectively. In addition, model Aggregate Measure (AM) was calculated 64 % and 54.15 % for the calibration and validation periods, respectively. Land use maps comparison showed, the main land use changes in Nojian Watershed was the conversion of forest and rangeland areas to agricultural lands .As a result of these changes the annual runoff volume, peak discharge, mean daily discharge increased to 16.20, 11.35 and 9.15 percent, respectively. Results of statistical analysis using paired t-test showed that land use change has effect on discharges in the study area at the level of 1%.
Seyed saeed Eslamian; Farshad Fathian; Hadi Hasanzadeh
Abstract
There are two parametric and nonparametric approaches for frequency analysis of hydrological data. Current methods of frequency analysis are based on the parametric methods. Moments, maximum likelihood and probability weighted moments are from various parametric methods for frequency analysis. In this ...
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There are two parametric and nonparametric approaches for frequency analysis of hydrological data. Current methods of frequency analysis are based on the parametric methods. Moments, maximum likelihood and probability weighted moments are from various parametric methods for frequency analysis. In this research, maximum likelihood and L-moment methods are used for precipitation frequency analysis. L-moment is a new method for frequency analysis and one of the specific kinds of probability weighted moments. The results of frequency analysis with L-moment are compared with maximum likelihood method and kernel functions of nonparametric methods of normal, log-normal, rectangular and triangular kernel function. In this research, monthly and annual precipitations are fitted to thirteen distribution functions such as Logistic, Generalized Extreme Value and etc. with estimation of L-moment and maximum likelihood methods. The results showed that L-moment parametric method is best fitted to monthly and annual data due to mean relative deviation and mean square relative deviation goodness of fit tests compared to maximum likelihood parametric method. The L-moment parametric method is also best fitted to Boushehr, Jask and Mashhad annual data due to mean relative deviation and mean square relative deviation goodness of fit tests compared to kernel nonparametric methods with rectangular, triangular and normal functions. Therefore, L-moment method is a suitable method for frequency analysis of other hydrological parameters such as flood and drought for planning of water resource management and hydrological analysis.
Davood Nikkami; Peyman Razmjoo; Farzad Bayat Movahed
Volume 2, Issue 2 , July 2010, , Pages 65-72
Abstract
The amount of water erosion is basically related to rainfall erosivity and its consequent runoff. In soil erosion and sediment yield models, intensity and energy of rainfall are mostly considered. In this research, some parameters such as the amount of rainfall, maximum intensity and energy in different ...
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The amount of water erosion is basically related to rainfall erosivity and its consequent runoff. In soil erosion and sediment yield models, intensity and energy of rainfall are mostly considered. In this research, some parameters such as the amount of rainfall, maximum intensity and energy in different basic times are correlated to the amount of runoff and sediment outflow from erosion plots to investigate rainfall erosivity index. For this purpose two years of precipitations of Sohrain-Gharacharian flood spreading research station were monitored by recording raingauge. During 2003-2004 period, two plough treatments of parallel and perpendicular to slope direction on three slope classes of 0-12, 12-20, and 20-40 percent with three replicates and randomized complete block design were studied under regional wheat planting and fallow conditions in 1.8x22 sq. meter erosion plots. The correlation between the amounts of runoff and sediment, as dependent variables, resulted from 12 rainfall events and the amounts of rainfall, maximum 1, 5, 15, 30, 60 and 120 minutes of rainfall intensity, rainfall energy and rainfall erosion index, as independent variables, computed by different methods were analyzed with the SPSS V11. Two variables of the amount of rainfall and the maximum rainfall intensity in different base times had the maximum correlation with the amount of runoff and sediment at the levels of 99 to 95 percent.
Payam Ebrahimi; Karim Soleymani; Kaka shahedi
Abstract
Neka watershed is associated with a large number of floods from the past, and had irrecoverable damages. Land use and its changes is one of the most important factors in country planning and policy making. In this research, land use map of year 2000 was prepared for Neka watershed by ETM+ images of 2000 ...
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Neka watershed is associated with a large number of floods from the past, and had irrecoverable damages. Land use and its changes is one of the most important factors in country planning and policy making. In this research, land use map of year 2000 was prepared for Neka watershed by ETM+ images of 2000 and IRS 1D images of 2011 based on digital processing of maximum probability in ENVI environment. Then, 2 km path upstream to Neka city was entered to GIS environment by 1:1000 scale plane maps and creating regional TIN and HEC-geo-RAS attachment. Finally, all data were imported to HEC-RAS software and flooding zonation was determined based on determination of roughness coefficient for two, three, five, 10, 20, 50, 100 and 200 return periods with Cown method. Results demonstrated that agricultural lands, Useless lands and municipal lands have been increased by 2.27, 7.31 and 1.91 percent, and forest and rangelands have been decreased by 10.22 and 1.27 percent respectively. These changes caused an increase of 13.14 percent of flooding zone in year 2011 compared to year 2000.
Peyman Daneshkar Arasteh; Masoud Tajrishy; Bahram Saghafian
Abstract
Earth skin temperature including soil, water, snow, and vegetation surface temperatureis one of the main variables in geo-science studies. Generally, spatial distribution ofsurface temperature is needed in such studies. Spatial monitoring of surface temperatureis possible using remote sensing data, and ...
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Earth skin temperature including soil, water, snow, and vegetation surface temperatureis one of the main variables in geo-science studies. Generally, spatial distribution ofsurface temperature is needed in such studies. Spatial monitoring of surface temperatureis possible using remote sensing data, and the time series of images provide acontinuous spatio-temporal framework required in modeling energy balance of regionalevaporation, optimization of energy demands or dispersion of atmospheric pollutions. Inthis paper, some common methods of surface temperature estimation using satelliteimagery were introduced and calibrations of several forms of split window equationwere addressed for Sistan area, Iran. Split window method is based on the fact that theatmospheric transmittance varies with wave length and uses a combination of thermalinfra-red brightness temperature and emissivity. To calibrate the split window equation,ground observations and 22 NOAA/AVHRR images during 1992 to 2002 were used todevelop regression models. Statistical tests were performed to evaluate the equationsand coefficients. Ten AVHRR images were used to verify the developed equations. Theresults indicated that three different forms of split window equations successfullypassed the χ2 statistical test. Both, F and Kruskal-Wallis tests showed that they are notstatistically different at 95 percent significant level. Therefore, the simplest form ofequation was used to derive surface temperature maps in the Sistan region, and isrecommended as the most applicable one.
Ali Mollaie; Abdol Rasoul Telvari
Volume 1, Issue 2 , July 2009, , Pages 70-77
Abstract
The first step for design flood estimation of a watershed is determination of the design rainfall characteristics. One of rainfall characteristics is its distribution over the rainfall duration. This is known as the temporal pattern of the design rainfall. In the present study, the data of four synoptic ...
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The first step for design flood estimation of a watershed is determination of the design rainfall characteristics. One of rainfall characteristics is its distribution over the rainfall duration. This is known as the temporal pattern of the design rainfall. In the present study, the data of four synoptic stations in Kohkiloyeh and Boyerahmad province have been used to determine the temporal pattern of rainfall, using the Pilgrim (ranking) method. Rainfalls of various durations less than 30 hours were classified into 1, 2, 3, 6, 9, 12, 18, and 24 hour durations, and then dimensionless temporal pattern were derived. In ranking method, each event is divided into a number of equal periods. Then, each individual burst is ranked according to the amount of rainfall in that period. The percentages of rain in all periods could be then ranked. The average percentages of rainfall among all recorded rainfall are estimated. The results show that, short duration rainfalls have maximum intensity in the second quarter, while longer duration rainfalls (12, 18, 24 hours) have maximum intensities in the third and fourth quarters. Thus, as rainfall duration increases, the maximum rainfall intensity moves towards the second half of time duration.
Jalal Yarahmadi; Ali Rahimi Khoob
Abstract
Evapotranspiration is one of the most important parameters for designing irrigation systems and estimating crop water use. Joining the models of reference evapotranspiration with the data derived from satellite images provides the opportunity for studying spatial variations of this parameter in extensive ...
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Evapotranspiration is one of the most important parameters for designing irrigation systems and estimating crop water use. Joining the models of reference evapotranspiration with the data derived from satellite images provides the opportunity for studying spatial variations of this parameter in extensive levels. In this study, four empirical models were evaluated including Hargreaves-Samani, Blaney–Criddle, Turc, and Linacre, which are dependent on temperature data for estimating reference evapotranspiration. Daily LST data obtained from MOD11A1 and MYD11A1 of MODIS were used rather than temperature data in these models. The minimum and maximum daily temperature, relative humidity, daylight hours, and wind speed were collected from weather stations located in five units of sugarcane farms (Shoaybie- SH, AmirKabir-AM, Farabi-FA, Khazaie-KH, and Ghazali-GH) in order to estimate reference evapotranspiration by Fao-Penman-Monteith equation as the target output. Calibration was done by the data of Shoaybie, Amir Kabir and, Farabi stations while the data of Khazaie and Ghazali stations were used for verification. This research showed that estimation of reference evapotranspiration can accurately be performed by LST data of Modis (MOD11A1 and MYD11A1) without direct measurements. Besides, the results revealed that use of LST data of MOD11A1 can lead to more accurate result for verification than MYD11A1. This outcome was resulted by comparing the precision measures of reference evapotranspiration based on the type of used thermal product as an input. Furthermore, comparing the precision measure of the models imply that operating the Turc model based on LST data of MOD11A1 can have more accurate results than other models (RSME and R2 are 1.3 mm.d-1 and 0.86, respectively).
Freidoon Soleimani; Mohammad Hossein Mahdian; Majid Heidarizadeh
Abstract
Due to the water resources limitation in the country, subsurface flow of the seasonal rivers has an important role. These water resources can be used when collected by underground dams in locations with appropriate properties. In order to use the subsurface flow, it is necessary to estimate water resources ...
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Due to the water resources limitation in the country, subsurface flow of the seasonal rivers has an important role. These water resources can be used when collected by underground dams in locations with appropriate properties. In order to use the subsurface flow, it is necessary to estimate water resources potential accurately. Therefore, the aim of this study is to estimate the volume of subsurface flow using Salas model based on hydrologic balance. For this reason, the meteorologic and hydrometric information and data of 15 stations were by gathered and two hydrometric stations of Abgelal and Marghab were chosen as suitable ones by assessing and field survey. At these stations, the balance of subsurface flow was estimated using the above mentioned model. The results showed that in Abgelal watershed, 73 and 11 percent of the total rainfall were lost due to evapotranspiration and infiltration respectively, and just 16 percent was outflowed from watershed in the form of surface runoff. Also, most of the rainfall was outflowed through surface runoff in Marghab watershed and the coefficient of runoff was 58.7 percent. In this watershed, 41.2 percent of the total rainfall was infiltrated and 29.9 percent was lost due to evapotranspiration and 27.4 percent was infiltrated. Considering the area of Abgelal watershed of 151.6 km2, about 8.4 million m3 is drained annually as subsurface flows. According to the area of Marghab watershed of 664.3 km2, annually about 250 and 43 million m3 are drained as surface and subsurface flows, respectively. Also, evaluation of the model in both stations using relative root mean square error, Nash-Sutcliffe efficiency and mean absolute error, showed the amounts of 2.53, 0.53 and 10.08 in Marghab and 0.97, 0.32 and 8.9 in Abgelal station.
Abolghasem Bagheri; Alireza Nikooie; Farhad Khodadad Kashi; Mohsen Shokatfadaei
Abstract
Although government’s supportive payments to agricultural activities is fulfilled for the purpose of increasing of social benefits, but it will cause some economic and environmental externalities. So that today the development of agricultural activities lead to decline in groundwater level in most ...
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Although government’s supportive payments to agricultural activities is fulfilled for the purpose of increasing of social benefits, but it will cause some economic and environmental externalities. So that today the development of agricultural activities lead to decline in groundwater level in most of these aquifers. This topic has increased the interest of related governmental sectors in developing and application of water conserving policies in aquifers. The objective of this study was to analyze and evaluate the outcomes of energy subsidies decline as specified water conservation policy alternatives on groundwater consumption and cropping patterns on the aquifer of Mahyar plain in Isfahan province, using non-linear optimization model. A Positive Mathematical Programming (PMP) model was developed and calibrated to land and water usage data for a base period of 2004-2005. The PMP approach produces a constrained non-linear optimization model that mimics the land and water allocation decision facing producers each year. The choice variables in the model are the acreages planted to each of the major crops and the water use by crop. The result showed that water application per acre decreased significantly under the high price scenarios, during the early years of the simulated period. This suggests that high energy prices have a significant effect on the rate of increment of the Mahyar aquifer stability.
Reza Bayat; Amir Sarreshtedari; Ali Jafari Ardekani; Reza Sokuti Oskuee
Abstract
Due to vegetation cover importance in protecting soil and its important role in controlling erosion, this study was conducted to determine the effect of land use managementon the Orumiyehlake watershed erosion rate, using GIS and RS technologies and EPM model. Using ETM+ 2002 satellite imagery, field ...
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Due to vegetation cover importance in protecting soil and its important role in controlling erosion, this study was conducted to determine the effect of land use managementon the Orumiyehlake watershed erosion rate, using GIS and RS technologies and EPM model. Using ETM+ 2002 satellite imagery, field work and existing map, required layer of model prepared and soil erosion was estimated in the current situation. Management scenarios, with good and bad actions through changes hypothetically in land use rank (decreased and increased in steps of five to 50 percent), the rate of soil erosion and changes in estimates were calculated. Results showed that maximum of erosion rates is belong to 3015 and 3054 sub-watershed with values of 768 and 749, minimum is belong to 3072 and 3056 sub-watershed with values of and 287 respectively and the mean for the watershed 485.9 . Trend of erosion rate change due to land use change was linearly and positive, meanwhile ultimate condition with 50% addition or reduction to land use rank, respectively caused 83.7 and -64.6 percent change in soil erosion.
