Showing 10 results for Swat
Amir Sarreshtehdari, Mohammad Ghafouri, Ali Jafari Ardakani, Reza Bayat,
Volume 2, Issue 3 (9-2014)
Abstract
Soil and Water Assessment Tool model, SWAT, uses different layers of watershed data which out of soil layer is the important one. Soil layer data should be extracted from detailed soil maps. In most developing countries including Iran, these detailed maps are not available except for irrigation districts and rarely for dry land farming areas and also for some strategic places of development purposes. For larger plains, the available soil maps information are reduced to semi-detailed scale which adds uncertainty in data required for catchments and hydrologic modeling. This research studied the relations between land use (LU) maps, land suitability for agricultural activities (LS) and physiographic soil unit (PU) on one hand and detailed soil maps and their embedded data on the other hand. The research has focused on the replacement of data derived from the detailed soil maps (from large scale soil map information) with those of readily available LS, PU and LU maps. Using these two sets of data for modeling of hydrologic system with SWAT on a 5793 Km2-watershed in west of Iran showed no significant difference between the simulated discharges at the watershed outlet. So the available LS map for the whole country may be used for both plains and catchments in SWAT simulation.
Samane Mahzari, Farshad Kiani, Mojgansadat Azimi, Farhad Khormali,
Volume 4, Issue 2 (6-2016)
Abstract
The adequacy of the SWAT model in the estimation of runoff, sediment yield and nitrate loss in the Gorganrood watershed was tested, using the existing spatial database as the primary data. The model was then executed for a 31-years’ time period. In combination with the SWAT model, the Sequential Uncertainty Fitting Program (SWAT-CUP and SUFI-2) was added used to calibrate and validate a hydrologic model of the watershed. The obtained values at 14 stations were between 0.48 to 0.83 for NS and 0.58 to 0.90 for R2, respectively. The results showed that nitrate loss was higher in cultivated lands, and in the loess deposits. The maximum amounts of runoff and sediment yield were largely produced in steep areas of the watershed, where dry farming was practiced. In general, the results showed that SWAT could be a proper tool for simulating runoff, sediment yield and nitrate loss into the river.
Majid Hosseini, Mohammad Ghafouri, Mahmoudreza Tabatabaei, Nadergholi Ebrahimi, Arash Zare Garizi,
Volume 4, Issue 3 (9-2016)
Abstract
The performance of the SWAT2012 model for estimation of hydrological budget in Gharasou watershed, west of Iran, during 1995 to 2005 was assessed. Digital Elevation Model, hydro-climatological data, soil and land use maps with their properties relevant to the watershed were considered to fulfill the model. A branch program in SWAT-CUP software (SUFI2) program implemented to simulate and validate the model. Both coefficients of determination (R2) and Nash- Sutcliffe coefficient exploited reliable analysis for simulation of the model from 0.37 to 0.87 and 0.39 to 0.73, respectively. Results showed that evapotranspiration was the main source of waste water (49.3%) in the study area. Surface runoff, subsurface flow, groundwater flow, and variation of soil moisture are 14.8, 0.8, 29.9 and 5.2 percent during the study period, respectively. The monthly proportions of different water pathways of input to the river flow take place from intense storms and snow melt during April to the end of May. This study has produced a technique with reliable data base for water budget in Gharasou catchment, which could be successfully developed to manage water resources by many government agencies.
A. Raeisi , A. Talebi , Kh. Abdollahi , A. Torabi Haghighi,
Volume 8, Issue 1 (3-2020)
Abstract
Aims: Affecting factors on runoff generation in mountainous areas, where the hydrological processes are complex, play an important role in the recognition of hydrological phenomena. The aim of the present study was to simulate the water balance of Farsan Basin using the SWAT model.
Materials & Methods: In this semi-distributed research, SWAT model was used to simulate the monthly runoff the basin of interest. The study area was Farsan watershed, it is the part of Beheshtabad Basin. Basin's curve number was estimated using a remotely sensed NDVI. The calibration and validation of the model were carried out by using the SUFI2 Algorithm (sequential uncertainty fitting) for two periods, one from 2001 to 2011 and another from 2012 to 2015.
Findings: The threshold depth of water in the shallow aquifer to start evaporation (REVAPMN) had the least sensitivity, while the soil evapotranspiration (ESCO), the time delay of the transferring water from the last soil profile to the groundwater level (GW_DELAY), and curve numbers in normal condition (CN2) were the most sensitive factors, respectively. To evaluate the simulation, R2 (coefficient of determination), bR2 (weight correlation coefficient), and NS (Nash Sutcliffe model efficiency) at the calibration stage were 0.63, 0.33, and 0.57, respectively. Whereas at the validation phase, these coefficients were found to be 0.69, 0.68, and 0.52, respectively.
Conclusion: A proper specification of these sensitive parameters may be the key factor for runoff simulations. The impact of change in surface parameters may have a great influence in both generating runoff and mountain hydrology.
M. Norouzi Nazar , E. Asgari , M. Baaghideh , S. Lotfi ,
Volume 8, Issue 3 (7-2020)
Abstract
Aims: In recent years, interest in quantifying ecosystem services (ESs) has dramatically grown among the scientific society. By increasing global environmental crises as a result of population growth, it is becoming increasingly essential to quantify the impacts that human activities have on ESs. Soil and water assessment tool (SWAT) is a process-based distributed hydrological model that has been widely recommended to quantify the ESs. The purpose of the present study is to employ the SWAT model for quantifying the flood regulation ecosystem service in one of the highest flood prone watersheds in the west of Iran.
Materials & Methods: In this study, after calibration and validation of daily and monthly discharge using SUFI-2 algorithm, the flood regulation index (FRI) was calculated for each year of simulation period (1989-2017).
Findings: The results show that climate variables such as precipitation could severely affect the quantities of FRI in different years. According to middle of 95PPU, the FRI varies from 0.22 in the wettest year of 1994 to 0.72 in the driest year of 2017 with precipitation values of 1080 and 380mm, respectively. The results also indicate that lower, middle, and upper limits of FRI 95PPU show the correlation coefficient of 28, 66, and 72% with the precipitation values in different years.
Conclusion: The available knowledge on the application of SWAT model in addressing ESs can be similarly used in the regions with corresponding environmental challenges of the low delivery level of regulation ESs.
Volume 12, Issue 1 (1-2010)
Abstract
In the present study, the Soil and Water Assessment Tool (SWAT 2000) model was tested on both a monthly and yearly basis and applied to the Kordan Watershed, located in Iran. The main objective of the research was to assess the accuracy of the model in sediment-yield and surface water bicarbonate concentration estimation. The attributes of sub-watersheds, tributary channels and the main channel in each sub-watershed were generated using the Digital Elevation Model (DEM) and Geographical Information System (GIS) Arc View SWAT 2000 interface. The model was calibrated and validated for the period from 1990 until 2004. Calibration results revealed that the model predicted monthly and yearly sediment-yield, but not such good results were obtained for the bicarbonate concentration. Therefore, some efforts were made in order to find a solution for SWAT bicarbonate temporal modeling. Around 70 samples of the Kordan River water quality data were used and, upon doing statistical calculations, the best correlation between the average pH–EC of water and the bicarbonate concentration was obtained. The formula shall be tested at several watersheds, and it can also be defined to SWAT in order that the model is able to calculate bicarbonate concentration according to pH and EC of the river water, which are introduced to SWAT by the user as a stream water quality file (SWQ) .
Mahnaz Kiyani Majd, Mohammad Nohtani, Mohammad Reza Dahmardeh Ghaleno, Zahra Sheikh,
Volume 12, Issue 4 (12-2024)
Abstract
Aims: The Digital Elevation Model (DEM) plays a crucial role in the SWAT model and significantly impacts its output results. This study evaluated the effect of different spatial accuracy of DEM in runoff simulation using the SWAT and SWAT-CUP models for the Lar Watershed in Sistan and Baluchestan Province.
Materials & Methods: This study examines the impact of different accuracies of Digital Elevation Models (DEMs) with resolutions of 12.5, 30, 50, 90, 450, and 1000-meters on discharge simulation using the SWAT model for the Lar Watershed, located in an arid region. The model was selected for 30 years (1988-2017), with 18 years for the calibration period and 12 years for validation. The SWAT-CUP software and the SUFI-2 method were used. The model’s accuracy was also evaluated using the Nash-Sutcliffe efficiency (NS), coefficient of determination (R²), r, and p coefficients.
Findings: The discharge simulation results reveal that variables such as area, sub-basin, Hydrologic Response Unit (HRU), watershed slope, and mean channel slope are particularly affected by DEM accuracy. With increasing DEM accuracy, the length of the main channels decreases, and lower-order channels are eliminated, reducing the calculated discharge depth. Our sensitivity analysis identified seven key parameters influencing discharge simulation in the Lar Watershed. The most critical parameters were r__CN2.mgt, v__ALpha_BF.gw, and r__SOL_AWC.sol, consistently recognized as highly sensitive in similar studies.
Conclusion: During validation and calibration, DEM resolutions of 12.5 and 1000 meters exhibited lower accuracy than those of 30, 50, 90, and 450 meters, suggesting that extremely high or low spatial data accuracy does not enhance simulation accuracy. Additionally, minimal differences were observed among the results for DEM resolutions of 30, 50, 90, and 450 meters. This can be attributed to adjustments in calibrated variable values and the application of the SUFI-2 method across different DEM accuracies. Finally, based on the results of this research, the DEMs with spatial resolutions of 30, 12.5, 50, 90, 450, and 1000 meters demonstrated the best performance for simulating monthly discharge in the Lar Watershed. Additionally, based on the value of the objective function (NS) during the calibration and validation stages, it can be concluded that the SWAT model can simulate the monthly discharge of the Lar Watershed with acceptable accuracy. Therefore, it can be said that the SWAT hydrological model can be used in arid regions to implement management scenarios quickly and at a low cost for decision-making.
Volume 14, Issue 3 (11-2014)
Abstract
This paper evaluates the efficiency of using surface water simulation results to improve the accuracy of groundwater simulation due to improving the accuracy of its input boundary conditions. The three most important data sets of boundary conditions in groundwater flow simulation are groundwater recharge, evapotranspiration rates and their regional distributions that little information is usually available about them. Moreover, the incorrect definition of these values can lead to uncertain groundwater modeling that is not applicable for groundwater resources management. In the most of previous studies done in Iran, percentage of the average regional precipitation and the local pan evaporation data (available from local weather stations) are used as the regional groundwater recharge and evapotranspiration rates, respectively but they have high uncertainty in their quantities and spatial distributions. In this research in order to solve this problem, the values of groundwater recharge and evapotranspiration rates and their regional distributions, obtained from SWAT modeling results, were used as the related input boundary conditions data in groundwater flow simulation using MODFLOW model. SWAT model is a comprehensive watershed model that calculates these values in each Hydrologic Response Unit (HRU). The study aquifer in this research was Silakhor shallow aquifer with the area of 590 km2 located in Lorestan province of Iran. The annual water table depth in different locations of this aquifer had been reported from 0.75 to 40 meter. Using this approach for improving boundary conditions in groundwater simulation and its evaluation was carried out for first time in Iran. The SWAT model was run for a period of 7 years from 2002 to 2008. After calibration and verification of the model using hydrodynamic data of Silakhor and Tire-Doroud gauging stations, the values of groundwater recharge and evapotranspiration rates in each HRU were extracted. The MODFLOW model was run for the period of 9 months of 2009 using these simulated boundary conditions and the other required information. For comparison of the calculated values with the observed values of water table depths in the 20 piezometers for the period of 9 months of 2009, the Root Mean Square Error (RMSE) and Mean Absolute Errors (MAE) were obtained 1m and less than 1m, respectively. In continuous of this research, the values of 5, 10 and 15 percent of regional average precipitation and the evaporation data in Silakhor pan evaporation gauging station were used as usual boundary condition for groundwater simulation using the MODFLOW model. For comparison of the simulated values of water tables depths obtained from this usual approach with the observed ones, the both of RMSE and MAE values were calculated more than 1 meter. Therefore this research showed that using integrated SWAT-MODFLOW models was more applicable in the groundwater simulation in the study aquifer.
Volume 14, Issue 5 (9-2012)
Abstract
In recent years, changes in catchments water balance due to land use management have become the main concern of water resources authorities in Iran. Due to rapid population growth and land use changes, especially construction of Taleghan dam, Taleghan catchment has undergone rapid changes such as urban development, declining of rangelands, and deterioration of environment and erosion of soil resources by cultivating the hilly lands along the slopes for wheat or barely production. The extent of rangeland area shrinkage is substantial: from 83% during the early stages of dam construction down to 35% by the end of the study period. The ‘good’ rangeland area decreased to 5.90% from 34.49% while the poor rangeland increased from 19.04 to 23.35% during the period of 1987 to 2007. These changes could potentially have devastating impacts on water balance of the catchment. The main objective of this research was to examine the effects of land use changes on water balance of the Taleghan catchment before and after the dam construction. The Soil and Water Assessment Tools (SWAT) model was applied for predicting water balance in the middle and outlet of the catchment. The main input data for simulation of SWAT are Digital Elevation Model (DEM), soil type, soil properties, and hydro-climatological data. Comparing the water balance for 1987's land use for the middle station (Joestan) and the outlet station (Galinak) showed that surface runoff was 21% of the precipitation for the upper part of the catchment and 33% at the outlet. Total groundwater and lateral flows were 37 and 19%, respectively. The water balance at the outlet was predicted for two other scenarios of 2001 and 2007. The results showed 7.3% increase in surface runoff and 11.3 and 11% decrease in the lateral flow and groundwater flow, respectively. These results indicated progressive increase in surface runoff and decline in interflow and groundwater flow.Therefore, one of the main challenges facing development planners is the control of the accelerated degradation of the natural resources that has been taking place during the last decade.
Volume 21, Issue 2 (7-2017)
Abstract
Abstract 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.
