Volume 15, Issue 2 (10-2024)
J Watershed Manage Res 2024, 15(2): 77-88 |
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bayani H, bagheri A, Akbari Nodehi D, Karimi V. (2024). The Effect of Land Use Change on Runoff Using the SWAT Model in the Tajan Watershed. J Watershed Manage Res. 15(2), 77-88. doi:10.61186/jwmr.15.2.77
URL: http://jwmr.sanru.ac.ir/article-1-1264-en.html
URL: http://jwmr.sanru.ac.ir/article-1-1264-en.html
1- Department of Watershed Science and Engineering, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran
2- Department of Water Science and Engineering, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran
3- Department of Soil Conservation and Watershed Management Research, Mazandaran Agriculture and Natural Resources Research and Education Center, AREEO, Sari, Iran
2- Department of Water Science and Engineering, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran
3- Department of Soil Conservation and Watershed Management Research, Mazandaran Agriculture and Natural Resources Research and Education Center, AREEO, Sari, Iran
Abstract: (305 Views)
Extended Abstract
Background: Land use/land cover (LULC) change in a specific area results from environmental and socioeconomic issues, as well as human activities over time and space. Increases and decreases in population growth in the system, climate, financial development, and physical elements, such as landscapes, soil grade, and type all influence LULC changes. The examination of conducted and documented research regarding the impact of land use change on the hydrological response of a watershed indicates that numerous studies have focused on this field both in Iran and globally. However, the effect of the pattern of landscape and the trend of its characteristics has not been observed to date. In this study, the processes of changing the landscape of the land, management scenarios, and the runoff of the Tajan watershed were investigated taking into account a 20-year period in the basin using the SWAT model under the scenarios of the continuation of land use changes. The relationship between flow and topography parameters was examined to take into consideration the potential possibilities of using topography parameters in watershed management.
Methods: The study area is the Tajan River basin (about 4000 km2) surrounded by the Alborz Mountains in the south and the Caspian Sea in the north, located in Mazandaran Province. The environmental hydrological flow index was investigated using the SWAT hydrological model, which is a semi-distributed, continuous hydrological model developed for water resource managers to select the most appropriate strategy or solution by considering the impact of various management practices on river flow and non-point source pollution. Then, the flow intensity of the area was investigated using the land use maps of the region under the periods 1991, 1995, 2000, 2010, 2016, and 2020 in terms of the changes in the landscape. Calibration and validation periods were selected based on the availability of hydro-metric station statistics located on the Tajan River for the years 1997-2012 and 2013-2018, respectively.
Results: The simulation results showed good simulation capability of the SWAT model in estimating the flow of Kordakhail, Parvij, Rigcheshmeh, Varand, Vastan, Garmrood, Karchai, and Aliabad hydrometric stations. EFC indicators, which are categorized into low monthly flows, very low flows, high flow pulses, small floods, and large floods, were also considered in this study because they are crucial for maintaining the ecological integrity of the river. The first EFC group, low monthly flow, represents surface flow, indicating that changes in these parameters could be associated with the availability of surface flow. Essentially, a minor decrease in low monthly flow can be observed in April, May, and October to December, ranging from 0.2% to 1.1% based on the average forecast of the ensemble. Conversely, low monthly flows from July to September are expected to increase significantly by 4.3% to 9.4% at a 95% confidence level. Overall, the flow process was estimated using the SWAT OUTPUT VIEWER. After examining the capability of the model for the effect of its effect on the amount of runoff, the results showed that the amount of runoff will increase in the land LULC, it is necessary to develop strategies for the river runoff management. The reason for the low results at some stations was the lack of a sufficient number of the rain gauge and synoptic stations in the areas to record heavy rainfall on a daily scale with better spatial coverage.
Conclusion: In the present study, the SWAT modeling and land change analysis were investigated as new planning tools to investigate land dynamics in the Tajen watershed from 1990 to 2020. The results of the analysis of changes during the years 1990-2020 showed the reduction of forests by 1211 hectares. The most deforestation was observed in the margins of former agricultural lands due to better access. In addition to the increase in population growth, the use of forest wood as fuel and the construction and repair of villagers' houses are other reasons for deforestation in the study area. The destruction of forest lands can also be attributed to livestock grazing. Similar to other modeling studies, the results presented in this research include various inherent limitations, and the modeling uncertainty was multiplied due to the application of land cover flow simulation in the hydrology model. This study clearly predicted the effects of vegetation change conditions in the Tajen watershed in several intervals. However, the decrease in water availability in late spring and summer can jeopardize the amount of water for irrigation downstream the basin, unless proper water management and storage is implemented along with better use and management of runoff. The results of this study especially confirm the importance of land cover, which can have a small effect, decrease, or increase the amount of water. Moreover, this study provides valuable and important information for decision-makers to design compatible scenarios in accordance with the principles of sustainable development, which aims to manage the flow. Finally, the results of this study especially confirm the importance of land cover, which can have a small, decreasing, or increasing effect on water quantity.
Background: Land use/land cover (LULC) change in a specific area results from environmental and socioeconomic issues, as well as human activities over time and space. Increases and decreases in population growth in the system, climate, financial development, and physical elements, such as landscapes, soil grade, and type all influence LULC changes. The examination of conducted and documented research regarding the impact of land use change on the hydrological response of a watershed indicates that numerous studies have focused on this field both in Iran and globally. However, the effect of the pattern of landscape and the trend of its characteristics has not been observed to date. In this study, the processes of changing the landscape of the land, management scenarios, and the runoff of the Tajan watershed were investigated taking into account a 20-year period in the basin using the SWAT model under the scenarios of the continuation of land use changes. The relationship between flow and topography parameters was examined to take into consideration the potential possibilities of using topography parameters in watershed management.
Methods: The study area is the Tajan River basin (about 4000 km2) surrounded by the Alborz Mountains in the south and the Caspian Sea in the north, located in Mazandaran Province. The environmental hydrological flow index was investigated using the SWAT hydrological model, which is a semi-distributed, continuous hydrological model developed for water resource managers to select the most appropriate strategy or solution by considering the impact of various management practices on river flow and non-point source pollution. Then, the flow intensity of the area was investigated using the land use maps of the region under the periods 1991, 1995, 2000, 2010, 2016, and 2020 in terms of the changes in the landscape. Calibration and validation periods were selected based on the availability of hydro-metric station statistics located on the Tajan River for the years 1997-2012 and 2013-2018, respectively.
Results: The simulation results showed good simulation capability of the SWAT model in estimating the flow of Kordakhail, Parvij, Rigcheshmeh, Varand, Vastan, Garmrood, Karchai, and Aliabad hydrometric stations. EFC indicators, which are categorized into low monthly flows, very low flows, high flow pulses, small floods, and large floods, were also considered in this study because they are crucial for maintaining the ecological integrity of the river. The first EFC group, low monthly flow, represents surface flow, indicating that changes in these parameters could be associated with the availability of surface flow. Essentially, a minor decrease in low monthly flow can be observed in April, May, and October to December, ranging from 0.2% to 1.1% based on the average forecast of the ensemble. Conversely, low monthly flows from July to September are expected to increase significantly by 4.3% to 9.4% at a 95% confidence level. Overall, the flow process was estimated using the SWAT OUTPUT VIEWER. After examining the capability of the model for the effect of its effect on the amount of runoff, the results showed that the amount of runoff will increase in the land LULC, it is necessary to develop strategies for the river runoff management. The reason for the low results at some stations was the lack of a sufficient number of the rain gauge and synoptic stations in the areas to record heavy rainfall on a daily scale with better spatial coverage.
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