جستجوی مقالات مرتبط با کلیدواژه « روش های تجربی » در نشریات گروه « جغرافیا »

Knowing the maximum flow rate is necessary to deal with floods, and one of the main problems in watershed planning is the lack or absence of necessary statistics, especially hydrological statistics. Therefore, the absence or lack of hydrometric information in watersheds requires appropriate experimental methods to estimate the maximum discharge. Thus, this research aims to estimate the maximum discharge in the mountainous part of Qaranqoo Chay and analyze the hydrological changes of the river. This research relies on fieldwork, using satellite images and topographic and geological maps. In this research, the water velocity was first measured using the Costa and Jarrett method, and then the flood discharge was estimated based on that. The hydrological conditions of the river were also calculated according to the data of the upstream and downstream stations of the range and using 18 indicators. The research results show that the maximum flood estimated by the Costa method (89.60 m3/s) is closer to the observed values, which indicates the efficiency of this method. Based on the research findings, the connection of Saraskandchay, Shorchay, and Khatonabadchay branches, high slope and impervious formations, low cross-section and channelization of the flow, local blockage due to the fall of large stone fragments and the filling of the section can be considered as the reason for the high maximum flood values in the mountainous part of Qaranqoo Chay. In addition, the results of the study showed that the construction of the Sahand dam caused a fundamental change in the downstream flow regime, and these changes affected the hydrological characteristics.

Choosing housing is the most basic need of every household.Therefore,identification and evaluation of effective factors in choosing housing from the viewpoint of the homeowner's households will play an important role in helping urban managers to promote and improve the housing conditions of the people.Accordingly,the present study was conducted to investigate and evaluate the factors affecting the probability of choosing housing with emphasis on the demographic characteristics of homeowning households in Isfahan. The research method is applied in terms of purpose and is descriptive-survey based on the data collection method. Data gathering method, documentary method by studying and investigating previous research, and field method. Data collection was done by designing empirical questionnaire, randomly from 300 households. These data were categorized in the EXCEL software and analyzed using the discrete multinomial logit model (MNL) in STATA software based on Random Utility Theory (RUT). The results of this study, taking into account the Z statistic of the variables, indicated that 11 variables were confirmed related to the properties of the housing, as well as the confirmation of 20 variables demographic variables defined in The model is relevant. The most influential demographic variables include: having children aged 18 and above, the number of home purchases, the reason for settling in Isfahan and the level of social relationships between the individual and his family, respectively,with 41,37,36,33%, the coefficient of positive effect on the probability of choosing in the multiple logit function.The results showed that the socio-economic are important and,in urban housing studies,should be specifically considered

Among factors affecting crop production, especially rainfed crops, the rainfall and its distribution during crop season have a significant role. In addition, all the precipitation that falls during the growing season does not have the same effect on crop yield, and is not used in agriculture. So, quantification of Effective Rainfall (ER), as a portion of the precipitation which is stored in plant root zone and meets the needs of evapotranspiration requirements in different climatic zones is an essential component of water resources in rainfed wheat areas. Effective rainfall used in this study is “That portion of the total precipitation on the cropped area, during a specific time period, which is available to meet the potential evapotranspiration requirements in the cropped area. A precise estimation of effective rainfall is still needed not only for planning and management of rainfed wheat production, but also for risk management strategies in farms. Since a precise estimation of effective rainfall is necessary for increasing agricultural production, major challenge is to design a soil-water balance model that provides more accurate calculation of effective rainfall. The main goal of this study was to compare different effective rainfall estimation methods for rainfed wheat. In this study, we adopted a two-layer soil–water balance (SWB) model. In the model,not only the portion of precipitation retained on root zone in current day is included, but a portion of the previous day’s precipitation saved between the previous and current root-zone development is also added to the effective rainfall of the current day. In the model, the soil reservoir is divided into two layers; 1) an active layer in which roots are presented at any given time, t, and from which both moisture extraction and drainage could occur; 2) immediately below the active layer, there is a passive layer of depth (maximum root depthroot depth attained any day after sowing) from which only drainage would occur. Because of a high cost associated with direct measurements, estimate of effective rainfall component is often based on empirical models. The aim of this study is to compare empirical methods of effective rainfall estimation with a proposed method based on soil-water balance equation. Following, six methods have been used to calculate effective rainfall for 21 agrometeorological stations of Iran:• Renfro Equation method • U.S. Bureau of Reclamation method • Potential Evapotranspiration/Precipitation Ratio method • USDA-SCS method • FAO method • TR21/SCS method For this purpose, four groups of data (including weather data, phenological data, soil characteristics, and wheat yield data) were used relevant to the 21 agro-meteorological stations representing arid, semi-arid, semi-humid, and humid regions of the country. Before using the weather data for estimating effective rainfall, data reconstruction was performed using Normalratio method (where required). The results of calculating the effective rainfall for rainfed wheat crop at the 21 agrometeorological stations, using selected methods and comparing the different methods of estimating effective rainfall, showed that: 1) in spite of data limitations, the new procedure had appropriate performance in estimation of that part of wheat yield which could only be explained by effective rainfall. Therefore, this method can be used as an efficient tool in computer based programs developed for agricultural risk management of rainfed area. 2) It has been observed that the higher the values of de Martonne Aridity Index, the lower is value of “effective rainfall/rainfall during the cropping season”. 3) The best result for arid and semi-arid climates was obtained by PET/P method (d-index= 0.8), and for semi-humid and humid climates by FAO method (respectively 0.9 and 0.8), and USDA-SCS method (respectively 0.8 and 0.7). A soil water balance model for estimating effective rainfall is applied for evaluating the accuracy of six established effective rainfall estimation methods. Renfro Equation provides an initial approximation based on aridity factor. The accuracy of this method is very low and it is exclusively empirical. USBR method considers only the runoff. The accuracy of this method is low and is not suitable for wide application. PET/Precipitation Ratio method takes the first approximation by runoff, soil and aridity factor. This method is suitable for preliminary plans, and is more effective than other methods, nearly in all regions. USDA- SCS method takes the first approximation of soil and crop beside aridity factor. This method is suitable for those areas that have low intensity of rainfall and high infiltration rate.

Residential environment and its selection process are the main issues in studies of urban planning. Uncertainty and complexity of human behavior، both citizens and decision-makers، will effect on the selection process. Recently، economic valuation methods have been used to study the factors and reproductive rules affecting the choice of residents. In this regard، the choice experiment method (CEM) has steadily gained ground. Over more than three decades has passed since the advent and widespread use of CEM. However، in our country، this method has received less attention. This paper introduces the application of the CEM in the study of urban residential environment. The results of this study show that CEM can measure the environmental values. But، these values have been less considered in urban projects. Some of the advantages of using this method include: identifying and ranking environmental values، measuring willingness to pay (WTP)، assessing policies، and providing recommendations to improve existing situation.

In this study undertaken in Babolroud Basin، seven models that included MPSIAC، EPM، Fournier، Douglas، Kirkby، Geomorphology and Hydrophysical were evaluated to determine the best model for estimation of soil erosion and sediment yield. These models have not been previously compared together. The zoning soil erosion intensity map was prepared from each model by using GIS. The estimated sediment yield was compared with the observed data (43 years of data from Ghorantalar Station) by using the statistical evaluation criteria such as relative and absolute difference، and correlation coefficient. Results showed that the MPSIAC model in the Lowland and Azar sub-basins، the Geomorphology model in the Karsang and Esklim Sub-basins، and the EPM model in the Babolak Sub-basin were more precise and efficient than the other models. By investigating the observed sediment data in Babolroud Basin، the MPSIAC model was used with a relative difference of 7. 932% (76659. 896 ton/y) and correlation coefficient of 0. 86، which was the most appropriate model to estimate soil erosion rate and sediment yield in this basin.

Tighab catchment has located between Khash and Iranshahr Townships. In this survey after collecting long time temperature, discharge and precipitation statistics (22 years) for catchment, we carried the research in two parts. The first section has been allocated for evaluating different methods for estimation of annual discharge of catchment and the second one for evaluating flood-water and selecting the best and the most appropriate methodology to estimate its value. Different statistical tests have been done on the data to ensure data homogeneity and distribution of selected stations, Using Justin, Indian Committee Agriculture (ICAR), Institute Irrigation Investigation up state of Indian and Lisi methods, the height of annual run-off has been calculated and the best method for estimating annual discharge was selected. Therefore, among used methods, Justin method gave better results because of considering more climatic and non-climatic parameters and regional coefficients for estimation of annual discharge. It is thereby suggested to be used in the Tighab catchment. At the next step, the regional flood-water has been studied and after estimating flood-water discharge in station, and investigating of different methods of flood estimation and selecting the most appropriate method at different return periods was also done. According to observed results, in order to obtain maximum floodwater momentary discharge, the SCS method shows more generality. In this study, since there is a serious limitation of ground water in Tighab region and so with the purpose of collecting and haltering surface and groundwaters, the attempt was focused on estimating both the value of annual discharge and the sub-basin flood-water of the study region.