اثرات تغيير كاربري اراضي بر رسوب دهي حوضه كوهدشت با استفاده از تكنيك منشايابي رسوب

The Effects of Land Use Change on Sediment Yield of Kouhdasht Basin Using Fingerprinting Technique

ﺗﻮﻟﯿﺪ رﺳﻮب از ﻣﻬﻢﺗﺮﯾﻦ ﻣﺴﺎﺋﻞ زﯾﺴﺖﻣﺤﯿﻄﯽ ﺣﻮزهﻫﺎي آﺑﺨﯿﺰ اﺳﺖ ﮐﻪ ﺑﺸﺪت ﺣﯿﺎت اﻧﺴﺎﻧﯽ و زﻧﺪﮔﯽ ﺟﺎﻧﻮري را ﺗﺤﺖ ﺗﺄﺛﯿﺮ ﻗﺮار ﻣﯽدﻫﺪ. ﺑﻨﺎﺑﺮاﯾﻦ ﺣﻔﺎﻇﺖ ﺧﺎك و ﻣﺒﺎرزه ﺑﺎ ﻓﺮﺳﺎﯾﺶ از ﺿﺮوريﺗﺮﯾﻦ اﻗﺪاﻣﺎﺗﯽ اﺳﺖ ﮐﻪ ﺑﺎﯾﺴﺘﯽ ﺑﻪ آن ﺗﻮﺟﻪ ﺷﻮد. ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ اﯾﻦ ﮐﻪ ﻋﻮاﻣﻞ ﻣﺨﺘﻠﻔﯽ ﻣﺎﻧﻨﺪ ﺗﻐﯿﯿﺮ ﮐﺎرﺑﺮي اراﺿﯽ ﻣﯽﺗﻮاﻧﺪ ﺑﺮ ﻣﯿﺰان رﺳﻮبدﻫﯽ ﺣﻮﺿﻪﻫﺎ اﺛﺮ ﮔﺬارد، ﭘﮋوﻫﺶ ﺣﺎﺿﺮ ﺑﺎ ﻫﺪف ﺑﺮرﺳﯽ اﺛﺮ ﺗﻐﯿﯿﺮ ﮐﺎرﺑﺮي اراﺿﯽ ﺑﺮ رﺳﻮبدﻫﯽ ﺣﻮﺿﻪ ﮐﻮﻫﺪﺷﺖ واﻗﻊ در ﻏﺮب اﺳﺘﺎن ﻟﺮﺳﺘﺎن اﻧﺠﺎم ﮔﺮﻓﺖ. ﺑﻪ اﯾﻦ ﻣﻨﻈﻮر اﺑﺘﺪا ﺗﻐﯿﯿﺮات ﮐﺎرﺑﺮي ﺑﺎ اﺳﺘﻔﺎده از ﺗﺼﺎوﯾﺮ ﻣﺎﻫﻮارهاي ﺑﺮرﺳﯽ و ﺳﭙﺲ ﻣﯿﺰان دﺑﯽ رﺳﻮب ﺑﺎ اﺳﺘﻔﺎده از دادهﻫﺎي دﺑﯽ ﺟﺮﯾﺎن و ﻏﻠﻈﺖ رﺳﻮب اﯾﺴﺘﮕﺎه ﻫﯿﺪروﻣﺘﺮي ﮐﺸﮑﺎن اﻓﺮﯾﻨﻪ در ﺧﺮوﺟﯽ ﺣﻮﺿﻪ ﻣﺤﺎﺳﺒﻪ ﺷﺪ. ﺳﻬﻢ ﻫﺮ ﯾﮏ از ﮐﺎرﺑﺮيﻫﺎي اراﺿﯽ در ﺗﻮﻟﯿﺪ رﺳﻮب ﺑﺎ اﺳﺘﻔﺎده از ﺗﮑﻨﯿﮏ ﻣﻨﺸﺎﯾﺎﺑﯽ رﺳﻮب ﺑﺮ اﺳﺎس ﻣﺪل ﻋﺪم ﻗﻄﻌﯿﺖ Bayesian ﺑﺮآورد ﺷﺪ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد، ﺗﻐﯿﯿﺮ ﮐﺎرﺑﺮي از ﻣﺮﺗﻊ و ﺟﻨﮕﻞ ﺑﻪ ﮐﺸﺎورزي ﻗﺎﺑﻞﺗﻮﺟﻪ ﺑﻮده ﺑﻪﻃﻮريﮐﻪ از ﺳﺎل 1361 ﺗﺎ ﺳﺎل 1395 ﺑﻪ ﺗﺮﺗﯿﺐ ﺣﺪود 49 و 24/8 درﺻﺪ از زﻣﯿﻦﻫﺎي ﻣﺮﺗﻊ و ﺟﻨﮕﻞ ﮐﺎﻫﺶﯾﺎﻓﺘﻪ و 47/5 درﺻﺪ ﺑﻪ زﻣﯿﻦﻫﺎي ﮐﺸﺎورزي اﺿﺎﻓﻪﺷﺪه اﺳﺖ. ﻧﺘﺎﯾﺞ ﺑﺮرﺳﯽ دادهﻫﺎي اﯾﺴﺘﮕﺎه ﻫﯿﺪروﻣﺘﺮي ﮐﺸﮑﺎن اﻓﺮﯾﻨﻪ ﻧﺸﺎن داد، ﻣﯿﺎﻧﮕﯿﻦ دﺑﯽ رﺳﻮب از 5/954 ﺗﻦ در روز ﻣﻨﺘﻬﯽ ﺑﻪ ﺳﺎل 1361 ﺑﻪ ﻣﯿﺎﻧﮕﯿﻦ 7/079 ﺗﻦ در روز ﻣﻨﺘﻬﯽ ﺑﻪ ﺳﺎل 1395 رﺳﯿﺪه اﺳﺖ. ﻧﺘﺎﯾﺞ ﻣﺪل ﻣﻨﺸﺎﯾﺎﺑﯽ رﺳﻮب ﻧﯿﺰ ﻧﺸﺎن داد اراﺿﯽ ﮐﺸﺎورزي ﺑﯿﺸﺘﺮﯾﻦ ﺳﻬﻢ را در ﺗﻮﻟﯿﺪ رﺳﻮب ﻣﻨﻄﻘﻪ دارد. ﺳﻬﻢ )ﻋﺪم ﻗﻄﻌﯿﺖ 5 ﺗﺎ 95 درﺻﺪ( ﻫﺮ ﯾﮏ از ﻣﻨﺎﺑﻊ ﮐﺸﺎورزي، ﻣﺮﺗﻊ و ﺟﻨﮕﻞ در ﺗﻮﻟﯿﺪ رﺳﻮب ﺑﻪ ﺗﺮﺗﯿﺐ ﺑﺮاﺑﺮ ﺑﺎ 95 )99-86(، 3 )12-0( و 0/9 )3-0( درﺻﺪ و ﺿﺮﯾﺐ اﻫﻤﯿﺖ ﻧﺴﺒﯽ ﻫﺮﮐﺪام از اﯾﻦ ﻣﻨﺎﺑﻊ ﺑﻪ ﺗﺮﺗﯿﺐ ﺑﺮاﺑﺮ ﺑﺎ 0/28 ،1/5 و 0/03 ﻣﺤﺎﺳﺒﻪ ﺷﺪ. اﯾﻦ ﻧﺘﺎﯾﺞ ﻧﺸﺎن ﻣﯽدﻫﺪ، ﻣﻬﻢﺗﺮﯾﻦ ﻋﺎﻣﻞ در اﻓﺰاﯾﺶ دﺑﯽ رﺳﻮب، ﺗﻐﯿﯿﺮ ﮐﺎرﺑﺮي از ﻣﺮﺗﻊ و ﺟﻨﮕﻞ ﺑﻪ ﮐﺸﺎورزي اﺳﺖ.

Sediment yield is the most important environmental issues in watershed basins which greatly affects human and animal life. Therefore, soil conservation and sediment control is one of the most important measures that should be paid attention. As various factors such as land use change can affect sediment yield, this study was performed to investigate the effect of land use change on sediment yield of Kouhdasht basin, located in the west of Lorestan province. For this purpose firstly, land use changes were investigated using satellite imagery and then sediment discharge was estimated using discharge and sediment concentration data of Kashkan Afrine station located at the basin outlet. Finally, the contribution of land use in sediment yield was estimated using the fingerprinting technique based on the Bayesian uncertainty model. The results showed that the change in land use from grazing land and forest to agriculture was significant. So that during 1361-1395, 49 and 24.8% of the grazing and forest lands were reduced, respectively and agricultural lands increased by 47.5%. Also the results obtained from Kashkan Afrine station data showed that the average sediment discharge increased from 5.954 ton/day in 1361 to 7.079 ton/day in 1395. The results of fingerprinting sediment model indicated that the agricultural lands have the most contribution in sediment yield. The contribution (uncertainty of 5 to 95%) of agriculture, grazing land and forest in sediment yield were calculated to be 95 (86-99), 3.1 (0-12) and 0.9 (0-3) percent, respectively and the relative importance of each resources was calculated to be 1.5, 0.28 and 0.03, respectively. These results indicated that the most important factor increasing sediment discharge is the land use change from forest and rangeland to agriculture.