جستجوی مقالات مرتبط با کلیدواژه « Estimation » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

Nowadays, waste management has become a serious concern of society due to increasing population growth rate and waste production. Despite efforts have been made to reduce the landfilling rate in Iran, a large amount of waste is still disposed of in landfills. Leachate generation is a major problem of landfills and, if not managed properly, it can cause significant threat to surface water and groundwater near to the landfill. Therefore, it is necessary to design a proper collection system to remove the leachate from landfill efficiently. Knowing the rate of leachate generation with reasonable accuracy is the critical input to design a landfill leachate collection system. In this study, a water balance method was used to estimate the amount of leachate produced in the Halgheh Darreh landfill of Karaj. In this model, we have considered a wide range of parameters that contribute to leachate generation in a landfill including rainfall, annual heat index, runoff, potential and actual evapotranspiration, the rate of leachate recirculation, evaporation from the surface of recirculation ponds, the amount of water used in gas production and also the initial moisture content of waste at the gate of landfill. The leachate generation rate was calculated for each month. In order to validate the results of the model, the actual leachate production was measured in December, January, February, March, April, May, June, and July. The comparison of the model estimates against the actual values measured at the site indicated an acceptable accuracy with a correlation coefficient (R) and the coefficient of determination (R2) equal to 0.966 and 0.933, respectively. Also, the root-mean-square error (RMSE) and mean absolute value of error percentage (MAPA) were 1328.27 and 9.17%, respectively, showing a small difference between the actual values and predicted values by the model. Also, the sensitivity analysis of the input parameters showed that the most important factor influencing the leachate generation is the moisture content of the incoming waste. The model developed in this study was a simple model and, with limited modification, it can be applied in other landfills located in arid regions of Iran.

Understanding the flooding phenomenon and its effective factors is an essential prerequisite of its control and management. This phenomenon is influenced by hydrological, climatic and physiographic factors, as it has always been one of the most important issues in hydrology. Using the overlapping of the climate and the border maps of the country, catchments of each climatic region were demarcated. Furthermore, 314 hydrometry stations with a common period (1976-2011) in six climatic zones were selected. The instantaneous peak discharge value was calculated for a 50-year return period. 15 hydrological, climatic and physiographic parameters affecting the flood severity, namely average altitude, catchment area, the Gravelius coefficient, the slope, the main river length, the annual average precipitation, the average number of rainy days, the base flow index (BFI), the hydrograph recession coefficient (K), the curve number (CN), the permeability and the flow duration curve indices (FDC indices) of, Q2, Q5, Q10, Q20, were calculated for each catchment. The factor analysis after data standardization was performed in order to select the most important independent factors affecting flooding severity for each climatic region and the regression between the Flooding severity index and the selected factors in different climate zones were extracted and analyzed. Results indicated that the parameters used in all of the climatic regions explained more than 74% of the variance of the data. Common parameters in the first class of effective factors in all of the climatic zones were different flow parameters of (BFI, K, FDC indices), along with some parameters that were related to the intrinsic characteristic of the catchment, such as the CN and permeability. The flow exceedance value of, Q2, Q5, Q10, Q20 in all of the climatic zones were ranked first and may be recommended for estimation and prediction in the ungauged catchment. The normal distribution of errors and the coefficient of Durbin Watson (between 1.5 and 2.5) reflect the confidence of the regression equations to estimate the Flooding severity in the ungauged catchments in the different climatic zones.

Runoff and sediment yield are important issues in water resource management that led to some problems in utilization of water structure and dams. Runoff volume, soil erosion intensity and sediment yield in watersheds are related to watersheds hydro-geomorphologic characteristics. Therefore, the aim of this research is to assess a relationship between watersheds hydro-geomorphologic characteristics with runoff and sediment yield in upstream of Samian hydrometer station with 42157 ha area. For this aim, the upstream watershed of this hydrometric station and 19 other sub watersheds were determined. The watersheds characteristics were divided in 6 groups and 76 parameters. Using of the correlation matrix, Ward clustering method and PCA method were determined parameters for modeling in three different scales that prepared 72 equations for estimation runoff and sediment yield. Also, the statistical coefficient consists of NS, R2 and RMSE were used for assessment of the obtained equations. Results showed that the obtained equations from total watershed scale with NS coefficient between 0. 95 and 0. 99, and R2 coefficient between 0. 97 and 0. 99 have the highest accuracy. Also, the equations obtained of selected parameters with PCA method have high precision than clustering method. Regarding importance of runoff and sediment yield estimation in ungauged stations, the regional modeling method can be used with high performance.

Soil erosion leads to washing topsoil, organic matter and soil fertility will decrease eventually. In order to combat erosion and loss of soil, conservation and watershed sediment generation in the NIR region, based on the WSM modeling was performed to estimate the severity of soil deposits. The model with six factors was scored for each work unit. Usually suitable model for certain areas that used them in different situations, needs to model coefficients be calibrated in the study area. For calibration, were measured the amount of precipitation from the model (estimated) and the simulated rain (objective) per work units in this watershed. The results were showed that in some work units the amount of estimated is more than 10 times versus the amount of real data (model with overestimating). The coefficients correction was done by optimizing in the Solver, with convergence (10-4), mutation and forward derivative (0.075) technology, with default values. With using the correction coefficients in the model and establishing a revised model, estimated sediment was closer to the objective values and were increased the correlation between estimate and the observed. Thus the modified model for areas with similar soil and climatic conditions in Yazd province, which has been used with caution. It is suggested to improve the coefficients, with the modified model results in a basin with actual values, to evaluate more confidently be used as local models.

Precipitation is one of the most important aerology parameters whose forecasting has significance in the prediction of drought and management of catchment. Today by creating evolutionary algorithms, this is done quickly and more accurately. One of these algorithms is the Imperialist Competitive Algorithm. In this study, using data for 15 years (1996-2010) in three synoptic stations in Kerman, the performance of this algorithm in forecasting daily precipitation is checked. The results show relatively good performance for this algorithm in precipitation, with a correlation coefficient of 0.8605, root mean square error of 1.029 and Willmott index of agreement of 0.96. However, because of the large number of dry days, accumulation of points are located in the origin of the coordinates.

Soil erosion and its consequences are major obstacles for development of the country. On the other hand, natural factors underlying erosion in Iran have caused Iran to have a high potential for water erosion. Knowing the erosion conditions are very important for erosion control, but significant differences can be observed in the presented information. Then, in this article it has been tried to present an illustrated image of the water erosion conditions in Iran. Reviews show that professionals have declared specific erosion rate of 16 to 25 t/h/y. In landscape of the country watersheds plan, the mean of specific erosion, total erosion of the country and total sediment of the country have been estimated using EPM model equal to 6.94 t/h/y, 975 and 129 million tons respectively. While, using the rating curves studies, total sediment yield has been estimated equal to 250 million tons per year. The results of erosion and sediment studies in 38 catchments in Qazvin province, indicate the rate of 16.6 t/h/y for the mean of specific erosion. The average sediment production of country is less than 15 t/h/y, based on the sediment measurement in reservoirs of small dams. Therefore, accurate estimation of the sediment yield with proper methods is necessary, since the estimated methods and the achieved values are very different. However, it can be said that the average erosion rate of the country lies between 7 and maximum 16 t/h/y. According to the area of Iran, soil erosion of the country would be 1.15 to 2.64 billion tons annually that is considered a high rate of water erosion.

It is essential to have correct information to determine short-term and long-term capacity of rangelands. Total forage yield cannot be used by livestock due to allowed utilization limit and palatability of species. Varkesh, Khodkavand and Orazan sub- basins of Taleghan region were selected for this research and within key region of each vegetation type, sampling was conducted based on randomized- systematic approach. Four transects of 100 m length was established in each type along and in vertical direction to the slope. Based on vegetation type and uniformity, 10 random plots of 1m2 area were considered and then by clipping and weighting method and considering palatability and allowed utilization limit, available forage yield was calculated. The results showed that among 10 existing types, five types do not have grazing suitability due to weak condition and high sensitivity to soil erosion and were not considered for calculating available forage yield which is mostly related to mountainous and steep slope of the region, low palatability of some class III species (Centaurea virgata and Astragalus aegobromus), sensitivity of soil to erosion and also existence of poisonous species in the region.