During the past couple of decades, the economical development policies of our country have aggravated the environmental problems of many watersheds. The development includes forest reclamation, and deforestation and paddy field reduction by building up residential, commercial, industrial areas and r...
During the past couple of decades, the economical development policies of our country have aggravated the environmental problems of many watersheds. The development includes forest reclamation, and deforestation and paddy field reduction by building up residential, commercial, industrial areas and road construction. They caused the water quality problems of stream and water body by point and nonpoint source pollutions. In addition to land use changes, the recent climate changes also affect the watershed hydrology and environment. From the 2007 IPCC (Intergovernmental Panel on Climate Change) reports, our country belongs to the rapid warming zone and will be strongly expected to be vulnerable to climate change during the 21st century. The objectives of this study are to assess the future potential climate and land use change impact on a watershed hydrology and environment, and suggest BMP (Best Management Practice) methods for the watershed to reduce the impact on the stream water quality. A 370.1 km2 watershed, the part of Anseong-cheon watershed which has the watershed outlet at Gongdo water level gauge station was selected. The CCCma (Canadian Centre for Climate Modelling and Analysis) CGCM2 (Canadian Global Coupled Model) based on IPCC SRES (Special Report Emission Scenarios) A2 and B2 scenarios were adopted for future climate condition, and the data were downscaled by Stochastic Spatio-Temporal Random Cascade Model technique. The future land use condition was predicted by using CA-Markov (Cellular Automata-Markov chain) technique with the past time series of Landsat satellite images. In this study, the technique was modified to enhance the predicted results. A logarithmic function was reflected for the trend of past land use change of each class. Data of water quality protection area and green belt area were considered to include systematic factor. In addition, the minimal preserved probability that is the percent of upper limit of land use change between land use classes in the process of prediction was applied to prevent unrealistic prediction of future land use. The future climate condition of the watershed showed that the mean temperatures of extreme 2090s of A2 and B2 scenarios increased 2.49 ℃ and 1.24 ℃, and the precipitation increased 117.7 mm and 299.8 mm respectively based on 2005 data. The future land use prediction results showed that the 2030, 2060 and 2090 urban areas increased 19 %, 31 % and 40%, and the paddy areas decreased 13 %, 18 % and 21 %, and the forest areas decreased 4 %, 5 % and 6 % respectively based on 2000 land use condition (urban: 42.1 km2, paddy: 189.4km2, forest: 251.7km2). For the assessment of future impact on watershed hydrology and stream water quality, the continuous hydrological and non-point source evaluation model, SWAT (Soil and Water Assessment Tool) was adopted. The model was calibrated and verified using 9 years (1997-2005) using point and nonpoint source data and agricultural management data. The watershed has two agricultural reservoirs (Gosam and GeumGwang). The reservoir operation module in SWAT was modified from original program for daily reservoir release preparation. The model results showed that the Nash-Sutcliffe efficiency of streamflow during the verification period was 0.79 and the RMSE (Root Mean Square Error) of SS, T-N and T-P were 1.33, 1.03 and 0.19 (ton/ha/day) respectively. After model setup, the model was applied to suggest the filter strip along the stream as BMP of the watershed to adopt the future climate and land use changes. In this study, the filter strip was added as a subwatershed instead of buffering along the stream. For a subwatershed which contributes high nonpoint source pollution, the 30 m length filter strip (0.02 % area of the subwatershed) was applied along both sides of 5.4 km stream reach. The filter strip reduced the SS, T-N and T-P of present status (2005) by 9.5 %, 4.1 % and 4.3 % respectively. Among the future precipitation condition, the 2030 precipitation was the extreme case. It reduced the SS, T-N and T-P of 2030 by 8.0 %, 8.4 % and 4.3 % respectively. This thesis has the meaning in providing the methodological procedures for the evaluation of future potential climate and land use changes on watershed hydrology and stream water quality. The model results are expected to plan in advance for the healthy and sustainable watershed management.
During the past couple of decades, the economical development policies of our country have aggravated the environmental problems of many watersheds. The development includes forest reclamation, and deforestation and paddy field reduction by building up residential, commercial, industrial areas and road construction. They caused the water quality problems of stream and water body by point and nonpoint source pollutions. In addition to land use changes, the recent climate changes also affect the watershed hydrology and environment. From the 2007 IPCC (Intergovernmental Panel on Climate Change) reports, our country belongs to the rapid warming zone and will be strongly expected to be vulnerable to climate change during the 21st century. The objectives of this study are to assess the future potential climate and land use change impact on a watershed hydrology and environment, and suggest BMP (Best Management Practice) methods for the watershed to reduce the impact on the stream water quality. A 370.1 km2 watershed, the part of Anseong-cheon watershed which has the watershed outlet at Gongdo water level gauge station was selected. The CCCma (Canadian Centre for Climate Modelling and Analysis) CGCM2 (Canadian Global Coupled Model) based on IPCC SRES (Special Report Emission Scenarios) A2 and B2 scenarios were adopted for future climate condition, and the data were downscaled by Stochastic Spatio-Temporal Random Cascade Model technique. The future land use condition was predicted by using CA-Markov (Cellular Automata-Markov chain) technique with the past time series of Landsat satellite images. In this study, the technique was modified to enhance the predicted results. A logarithmic function was reflected for the trend of past land use change of each class. Data of water quality protection area and green belt area were considered to include systematic factor. In addition, the minimal preserved probability that is the percent of upper limit of land use change between land use classes in the process of prediction was applied to prevent unrealistic prediction of future land use. The future climate condition of the watershed showed that the mean temperatures of extreme 2090s of A2 and B2 scenarios increased 2.49 ℃ and 1.24 ℃, and the precipitation increased 117.7 mm and 299.8 mm respectively based on 2005 data. The future land use prediction results showed that the 2030, 2060 and 2090 urban areas increased 19 %, 31 % and 40%, and the paddy areas decreased 13 %, 18 % and 21 %, and the forest areas decreased 4 %, 5 % and 6 % respectively based on 2000 land use condition (urban: 42.1 km2, paddy: 189.4km2, forest: 251.7km2). For the assessment of future impact on watershed hydrology and stream water quality, the continuous hydrological and non-point source evaluation model, SWAT (Soil and Water Assessment Tool) was adopted. The model was calibrated and verified using 9 years (1997-2005) using point and nonpoint source data and agricultural management data. The watershed has two agricultural reservoirs (Gosam and GeumGwang). The reservoir operation module in SWAT was modified from original program for daily reservoir release preparation. The model results showed that the Nash-Sutcliffe efficiency of streamflow during the verification period was 0.79 and the RMSE (Root Mean Square Error) of SS, T-N and T-P were 1.33, 1.03 and 0.19 (ton/ha/day) respectively. After model setup, the model was applied to suggest the filter strip along the stream as BMP of the watershed to adopt the future climate and land use changes. In this study, the filter strip was added as a subwatershed instead of buffering along the stream. For a subwatershed which contributes high nonpoint source pollution, the 30 m length filter strip (0.02 % area of the subwatershed) was applied along both sides of 5.4 km stream reach. The filter strip reduced the SS, T-N and T-P of present status (2005) by 9.5 %, 4.1 % and 4.3 % respectively. Among the future precipitation condition, the 2030 precipitation was the extreme case. It reduced the SS, T-N and T-P of 2030 by 8.0 %, 8.4 % and 4.3 % respectively. This thesis has the meaning in providing the methodological procedures for the evaluation of future potential climate and land use changes on watershed hydrology and stream water quality. The model results are expected to plan in advance for the healthy and sustainable watershed management.
주제어
#기후 토지이용 비점원 오염 SWAT GCM Downscaling Modified Land Nonpoint Stream
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