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

Recently, the effects of climate change on the hydrological cycle and regime have become an important research topic. The results of atmospheric general circulation models (GCMs) together with hydrological models are used to determine the impacts of climate change on hydrologic regime. The daily minimum and maximum temperatures, rainfall and sunshine hours of the Shiraz synoptic station were simulated using the LARSE_WG6.0 statistical model. The efficiency of the model for simulating climate variables was determined using historical data of Shiraz station. To investigate climate change on runoff, two scenarios of the HadGEM2-ES model for two periods were downscaled using the LARSE_WG model. In the next step, runoff was simulated using the SWMM model and its results were compared with the measured runoff. For this purpose, 2 events were used for calibration and one event for validation. Based on coefficient correlation (R), root mean square error (RMSE) and Nash-Sutcliffe efficiency (NSE), the model has a suitable efficiency for simulating runoff. Then, LARSE_WG downscaled data were used in SWMM model and the runoff changes in future periods compared to present. According to RCP4.5 and RCP8.5 climate scenarios, precipitation will increase from 16.10 to 8.88% in 2021-2040 and 14.49% and 19.73% in 2061-2080. Therefore, assuming no change in landuse in Shiraz district 8, the volume of runoff will increase from 13.35 to 21.48 percent.

The quantitative and qualitative management of urban runoff is a very complicated. Regardless of the economic and social impacts, water engineers always need to know how to respond to a citychr('39')s drainage system against different climatic conditions. In this research, the combination of ASSA and GIS models in the returns periods of 2, 5, 10 and 50 years were used to determine the flooding points in the 9th district of Mashhad municipality. First, the watershed boundaries, canals and nodes maps was extracted from the GIS environment. Then the ASSA model was simulated for a One-hour design for a different return period. Then, the outputs of the model were analyzed in the GIS software environment. The results showed that with increasing rainfall return period, 2806 nodes in underground and superficial networks of 114, 178 and 226 nodes were flooded and inundation during the return periods of 2, 5, 50 and 50 years, respectively. Field surveys, existing elevation digital maps of the urban runoff network and simulations have shown that the main cause of inundation is the small size of the cross section of the duct, as well as the low slope in some parts of the network. Adaptation of the results of the simulation of rainfall-induced waterlogging in the study area with what happens every year confirms indicates the correctness of the simulations of the model. Moreover, simulation results of the model also showed that there is a good agreement between the simulated results and the measurement.

SWAT is a continuous-time model that operates on a daily time step at the basin scale. The objective of such a model is to predict the long-term impacts of management and the timing of agricultural practices within a year (i.e., crop rotations, planting and harvest dates, irrigation, fertilizer, and pesticide application rates and timing) on large basins. It could, at the basin scale, be used to simulate the water and nutrients cycle of landscapes whose dominant land use is agriculture. It could also help assess the environmental efficiency of best management practices and alternative management policies. The SWAT model uses a two-level disaggregation scheme: a preliminary sub-basin identification is carried out based on topographic criteria followed by further discretization, using land use and soil type considerations. Areas with the same soil type and land use form a Hydrologic Response Unit (HRU), a basic computational unit assumed to be homogeneous in hydrologic response to land cover changes.The development of the digital computer has added a new dimension to hydrology. Previously, finding solutions for different problems took hours with a pen and pencil method, but now it takes seconds with modern computers. Moreover, much more complex methods of analysis are now feasible because of the speed of the solution-finding provided by the computer. The impact of the computer has been particularly great in the area of rainfall-runoff modeling. As flood routing and unit hydrograph analysis are mathematical modeling’s, surface-water hydrology is, historically, concerned with modeling. Due to the climate type and the spatial and temporal inconsistency of rainfall in Iran, large floods cause many damages in different parts of the country annually, as the Mediterranean climate and different weather conditions throughout a year provide the ground for the majority of short-term atmospheric rainfall.

Karkheh Basin is one of the main watersheds of Iran which has a Mediterranean climate whose level increases during the spring due to simultaneous rains and snowmelt. As one of the most important hydrological processes of the watershed for better understanding the hydrological issues of flood control structures for long-term planning, applying best management practices and making better use of their potentials, Runoff simulation plays an important role in water resources studies. Thus, to calibrate the model, select sensitive parameters were used in the sensitivity analysis step. Having imported the sensitive parameters into SWAT-CUP software, they were repeated 500 times with the SUFI2 algorithm, and finally, the optimal value for each parameter was determined.

At Hamidiyeh station, the Nash Sutcliffe coefficient was -0.19 and -0.04 in both calibration and validation periods, respectively, and was 0.76 and 0.77 in Chamangir Station, respectively. The coefficients of determination for the Hamidiyeh station in the calibration and validation periods were 0.02 and 0.22, respectively, and for the Chamangir station, they were 0.88 and 0.75, respectively.This study investigated simulated runoff, using the SWAT model based on the meteorological data regarding the Karkheh watershed. A comparison of simulated runoff results with observational runoff at the hydrometric stations was performed automatically by the SWAT_CUP software package SUFI2 algorithm. Correlation between observed and simulated data was calculated based on the Nash Sutcliffe coefficient and the determination coefficient at different stations of the basin. Nash coefficient - Sutcliffe and coefficient of determination at all hydrometric stations except for the five stations which differed in their calibration and validation periods, were found to be close to their optimum values.

The coefficient - Sutcliffe of the other 6 stations was more than 0.5, indicating that the model was capable of simulating runoff. In the mirage stations of Sarab Seyed Ali, Pulchehr, and Noorabad, the SWAT model failed to simulate runoff well, which could be due to the location of these stations in the elevated areas of the basin and its branches that were snowy. The lack of proper distribution of meteorological stations in these areas makes the model unable to simulate well the snow runoff. In Hamidiyeh and Pai-Paul stations, the SWAT model was could not establish a reliable relationship between the observed and simulated runoff due to the impact of the construction of the Shahid Abbaspour Dam on the river flow hydraulics.

Accurate estimation of a watershed response to rainfall events plays an important role in its soil and water resources management as well as civil works design within watersheds and over or around its downstream rivers. Nowadays, due to improvement in our knowledge and understanding from watershed systems and enhancement in hardware and software technology as well as facilitation in learning and application of these technologies, researchers prefer to design and apply their required models themselves according to their aims and availability of data. The aim of this research is to develop a spatio- temporally distributed model within PCRaster GIS and programming environment to achieve a better representation of watershed processes at a small scale agricultural micro-watershed. In this study, based on the available local data, an event based rainfall – runoff hydrological simulation model was developed within PCRaster GIS and programming software and its performance was evaluated using observed data from a 27.6 ha agricultural micro-watershed discharging to the Shahrak – Behzisti residential area in the Gorgan city. This is a tightly coupled GIS model. During the research period, only two rainfall events leading to runoff generation occurred on 2/11/2014 and 16/9/2015 which were, respectively, used for calibration and validation of the model. Statistical comparison of the simulated and observed hydrographs of the rainfall - runoff events on 2/11/2014 and 16/9/2015 showed the correlation coefficients of of 0.69 and 0.65 and Nash-Sutcliffe criteria of 0.5 and 0.51, respectively. The results indicate that the developed model has a good performance at simulating rainfall-runoff processes during events.

In mountainous regions, snow forms a part of the precipitation. Therefore, snow melting is an important process in hydrology and hydraulic in these areas that its role should be considered independently in runoff generation. The Shemshak watershed basin located in Tehran province was selected as the study area of this research to examine the efficiency of the WetSpa hydrologic model to simulate the runoff generated from snow melting in a 12-year period (2002-2014). Spatially distributed model of WetSpa simulates various hydrological processes such as snow melting using degree-day method in a cell and on hourly and daily time scales. Different hydrologic processes in this research are simulated by the WetSpa model using climatic data (rainfall, temperature, evaporation, and discharge) and spatial maps (land use, soil texture, and Digital Elevation Model). Evaluation of the model performance to simulate the daily hydrograph based on the Nash-Sutcliffe and Kling-Gupta showed that the values of these criteria are 71.3% and 83%, respectively. based on the results, the WetSpa model has a good capability to simulate the runoff generated from snow melting in the daily time scale. Also, the snow coefficient for the study region was 0.28.

This study was conducted to evaluate the capability of the DHSVM model to simulate hydrological processes in a mountainous watershed with a minimum agricultural land use. The required climatic parameters were set for the daily time step. The inverse distance method was used to interpolate the climatic variables from the stations to the network cells. Time inputs to the model were prepared for the years 2008 to 2013. The land cover map was prepared using the supervised classification method of Landsat TM data. The stream network map was generated using the DEM map in ArcGIS software. The soil texture map was prepared using field sampling and in the laboratory. Primary tests to the determine sensitivity of input parameters showed that this model is sensitive to lateral hydraulic conductivity, exponential coefficient of hydraulic conductivity, porosity, field capacity, and minimum stomatal resistance. In this study, except for the lateral hydraulic conductivity and exponential decrease coefficient, all other parameters (soil and vegetation) were determined based on previous studies and field measurements in a similar way for both categories of data.  The time series of the data were divided into three, warm- up or preparation periods (2008-2009), calibration (2009-2011) and validation (2011-2013). The model was calibrated using stream flow data from 2008 to 2010. Different efficiency criteria were calculated between simulated and observed flows. NSE value for calibrating was 0.59 and for validation was 0.606. In general, the results of this model implementation in the studied basin with the quality and quantity of input data to the model are satisfactory.

Study on natural processes related to water as well as knowledge about runoff and hydrological conditions is necessary for improvement of water management in Iran. Since most of watersheds in Iran are ungauged, so using hydrologic models to simulate the runoff is inevitable. In this study, continuous distributed hydrologic model WetSpa was used to simulate Zoshk watershed runoff. Three basic maps including digital elevation model (DEM), landuse and soil texture are the model inputs. Required meteorological data are potential evapotranspiration, precipitation and temperature. The basin outlet discharge in Zoahk gauging station is used to calibrate and evaluate the model. Calibration period is from 2009/01/01 to 2011/31/12 and validation period is from 2012/01/01 to 2014/31/12. PEST software was used to calibrate the model parameter. Results show good agreement between calculated and measured hydrographs. The model predicts the hourly hydrographs with a good accuracy, so that according to the Nash-Sutcliff criterion the accuracy is more than 85% and 83% for calibration and validation periods, respectively. The result shows that this model only simulates the high flows well and the simulation result is not appropriate for low flows. This is due to the use of river flow for dry season irrigation.

Run off simulation is one of the most important topics in hydrology And its study is based on rainfall- run off models. Several rain fall and run off models have been developed and the most appropriate model should be selected for each catchment. By applying the appropriate model the water consumption will be optimized. The model should be selected for each catchment based on the model abilities and limits. In this study, the performance of two rain fall and runoff models, GR2M and GR4J were compared in Darehtakht Basin in Lorestan Province during 1379 to 1392. The Nash coefficient was used as a decision criteria for comparing two model performances. Nash coefficient for GR4J and GR2M were 42.7 and 65.5, respectively. Results showed that both models can predict the performance of the catchment accurately, but, based on Nash coefficient the GR2M is more accurate than the GR4M.

The runoff simulation in a watershed provides insight on the processes affecting runoff generation and the stream flow characteristics like spatial and temporal variability of stream flow. This insight helps managers and planners in informed decision-makings on water resources management and planning. The objective of this study is to compare the performances of the complex SWAT model and the simple IHACRES model for simulating runoff in the Doiraj river basin, Ilam province. For this purpose, SWAT model due to having many parameters affecting stream flow and the use of GIS, and IHACRES model due to the low and easy access data requirements, are very practical. In this study, the data over a period from 1994 to 2004 and the statistical criteria of R2, bR2, and NS were used to evaluate performances of IHACRES and SWAT models. For IHACRES model, values of R2, bR2 and NS were estimated equal to 0.34, 0.112 and 0.33, respectively for calibration period and values of 0.47, 0.235 and 0.43, respectively for validation period. In addition, for SWAT model, the coefficients were estimated equal to 0.41, 0.314 and 0.12 respectively, for calibration period and values of 0.68, 0.632 and 0.56, respectively for validation period. Final results of this study showed higher performance of SWAT model relative to IHACRES model for simulating daily runoff in Doiraj river basin and can be used to simulate runoff in the watersheds with limited data and similar natural conditions.

In order to assessment and prediction of hydrological processes with inherent complexity, processes changes effects on the nonlinear behavior of watershed system in the past and future and specification of water and soil conservation operation, using indirectly methods such as simulation of watershed processes therewith directly methods is necessary. The objective of this research is evaluation of runoff generation in space and time using distributed hydrological WetSpa model in Taleghan watershed of the Sefidrood basin. Thus flow hydrographs and peak discharges in any space of the stream network were predicted also spatially distribution of hydrological processes such as runoff was simulated using incorporating of both daily meteorological data in an 11 year period and three base maps information. Simulated results reveal that there is good agreement between observations and simulations. The Nash- Sutcliffe criteria, 83.3% and accuracy of the simulation show the high performance of the model in this watershed. Regarding to the outputs and spatially distributed hydrological factors in daily time step the model is capable to analyze topography, soil type, and land use effects on the hydrological behavior of the watershed.

Rainfall characteristics are different spatially and temporally and this issue has impact on runoff. So, considering the spatial and temporal distribution of rainfall is one of the most important factors in the simulation of rainfall-runoff. Spatial and temporal distribution of rainfall is not same in a basin due to its topographic and climatic variations, but to simplify the calculation of storm movement in sub basins, this issue is not considered in most studies and is led to the under or over estimate of the peak discharge of runoff. So, in this research, at first spatial distribution of rainfall was calculated in each sub basin using the recorded data of rainfall in daily rain-gauge stations of Amirkabir dam basin and Inverse Distance Weighting (IDW) method. Temporal distribution of rainfall was examined in two cases. At the first case, that is a widespread method for regions without station, the used rainstorm in all sub basins considered as same as the nearest stable rain-gauge station and in the second case, time of rainfall occurrence in sub basins has been estimated based on the distance of the center of gravity of sub basins from the nearest rain-gauge station to the study area and the time of rainstorm in the other rain-gauge stations and then was shifted based on the hyetograph of rainfall in sub basins. To evaluate the impact of temporal shift of rainfall on peak discharge, simulated runoff was compared in two stable and moving storm cases. Results of rainfall simulation for five selected storm events showed that temporal shift of rainfall (second case) significantly has improved the estimation of peak discharge and time to peak of the rainfall compared to the first case.