ارزيابي توليد رسوب در حوزه هاي آبخيز كوچك تحت چراي آزاد و قرق، مطالعه موردي: منطقه سنگانه كلات

Evaluation of sediment yield under open grazing and exclosure micro-watersheds, case study: Sangnaeh area of Kalat

ﻗﺮق ﻣﺮﺗﻊ ﯾﮏ روش ﻣﺪﯾﺮﯾﺘﯽ آﺑﺨﯿﺰداري ﺑﻪ ﻣﻨﻈﻮر ﺑﻬﺒﻮد وﺿﻌﯿﺖ ﻣﺮاﺗﻊ اﺳﺖ. ﺑﺎ اﯾﻦ ﺣﺎل، اﻏﻠﺐ ﻣﻄﺎﻟﻌﺎت ﻫﯿﺪروﻟﻮژي ﻣﺮﺗﻊ ﺑﻪ ﺑﺮرﺳﯽ اﺛﺮ ﻗﺮق ﺑﺮ ﻫﺪررﻓﺖ ﺧﺎك در ﻣﻘﯿﺎس ﮐﺮت ﭘﺮداﺧﺘﻪ اﻧﺪ و ﻣﻄﺎﻟﻌﺎت اﻧﺪﮐﯽ اﺛﺮ اﯾﻦ اﻗﺪام ﻣﺪﯾﺮﯾﺘﯽ ﺑﺮ رﺳﻮب ﺗﻮﻟﯿﺪي آﺑﺨﯿﺰﻫﺎي ﮐﻮﭼﮏ در ﻣﻘﯿﺎس ﻫﺎي زﻣﺎﻧﯽ ﻓﺼﻠﯽ و ﺳﺎﻻﻧﻪ را ﻣﺪ ﻧﻈﺮ ﻗﺮار داده اﻧﺪ. در اﯾﻦ راﺳﺘﺎ، ﭘﮋوﻫﺶ ﺣﺎﺿﺮ ﺑﻪ ﻣﻨﻈﻮر ارزﯾﺎﺑﯽ ﺗﻮﻟﯿﺪ رﺳﻮب در آﺑﺨﯿﺰﻫﺎي ﻗﺮق و ﺗﺤﺖ ﭼﺮا ﺑﻪ ﺗﺮﺗﯿﺐ ﺑﺎ ﻣﺴﺎﺣﺖ ﻫﺎي 1/0 و 1/1 ﻫﮑﺘﺎر در آﺑﺨﯿﺰ ﺗﺤﻘﯿﻘﺎﺗﯽ ﺳﻨﮕﺎﻧﻪ واﻗﻊ در ﺷﻤﺎل ﺷﺮق اﺳﺘﺎن ﺧﺮاﺳﺎن رﺿﻮي ﻃﺮح رﯾﺰي ﺷﺪه اﺳﺖ. ﺑﺮاي اﯾﻦ ﻣﻨﻈﻮر، رواﻧﺎب و رﺳﻮب در ﻣﻘﯿﺎس رﮔﺒﺎر در ﺧﺮوﺟﯽ ﺣﻮﺿﻪ ﻫﺎي ﮐﻮﭼﮏ ﻣﺮﺑﻮط ﺑﻪ 56 رﮔﺒﺎر ﻃﯽ دوره 1385 اﻟﯽ 1395 ﺟﻤﻊ آوري ﺷﺪ. ﻧﺘﺎﯾﺞ دﻻﻟﺖ ﺑﺮ اﺛﺮ ﮐﺎﻫﺸﯽ و ﻣﻌﻨﯽ دار )P≤0/05( ﻗﺮق ﻣﺮﺗﻊ ﺑﺮ رﺳﻮب دﻫﯽ در ﻣﻘﯿﺎس آﺑﺨﯿﺰﻫﺎي ﮐﻮﭼﮏ داﺷﺘﻪ اﺳﺖ. ﺑﻪ ﮔﻮﻧﻪ اي ﮐﻪ ﮐﺎﻫﺶ 582 درﺻﺪي رﺳﻮب در ﺗﯿﻤﺎر ﻗﺮق ﻧﺴﺒﺖ ﺑﻪ ﭼﺮاي آزاد ﺑﻪ دﺳﺖ آﻣﺪ. ﻫﻤﭽﻨﯿﻦ، ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ اﺛﺮ ﻗﺮق ﺑﺮ ﻓﺮاﯾﻨﺪﻫﺎي ﻫﯿﺪروﻟﻮژﯾﮏ داراي ﺗﻐﯿﯿﺮات ﻓﺼﻠﯽ و ﺳﺎﻻﻧﻪ اﺳﺖ، ﺑﻪ ﮔﻮﻧﻪ اي ﮐﻪ ﺑﯿﺸﯿﻨﻪ و ﮐﻤﯿﻨﻪ اﺧﺘﻼف ﺑﯿﻦ ﺗﯿﻤﺎرﻫﺎ ﺑﻪ ﺗﺮﺗﯿﺐ در ﻓﺼﻞ ﻫﺎي ﺑﻬﺎر و زﻣﺴﺘﺎن ﻣﺸﺎﻫﺪه ﺷﺪه اﺳﺖ. ﺑﺎ اﺳﺘﻔﺎده از ﻧﺘﺎﯾﺞ اﯾﻦ ﭘﮋوﻫﺶ، ﻣﯽ ﺗﻮان ﺑﯿﺎن ﮐﺮد ﮐﻪ ﻣﺪﯾﺮﯾﺖ ﭼﺮاي دام ﻃﯽ ﻓﺼﻞ ﻫﺎي ﺣﺴﺎس و ﻫﻤﭽﻨﯿﻦ، ﻗﺮق ﻣﺮاﺗﻊ در ﺻﻮرﺗﯽ ﮐﻪ ﻣﺴﺎﺋﻞ اﺟﺘﻤﺎﻋﯽ آن ﺑﺮﻃﺮف ﺷﻮد، ﺑﻪ ﻋﻨﻮان ﯾﮏ راﻫﮑﺎر ﻋﻤﻠﯽ در ﮐﺎﻫﺶ رﺳﻮب ﺣﻮزه ﻫﺎي آﺑﺨﯿﺰ ﻣﻄﺮح اﺳﺖ.

Rangeland exclusion is one of the watershed management methods that is applied for range rehabilitation. However, most rangeland hydrology studies have been focused on exclusion effects on soil loss at plot scale, whereas their effects on sediment yield at micro-watershed in seasonal and annual scales have rarely been considered. The present study was conducted in two sub-watersheds under exclosure and open grazing treatments, with area of 1.0 and 1.1 ha, respectively, in Sanganeh Watershed, Khorasan Razavi Province, Iran. Runoff and sediment associated with 56 storm events occurred during 2006 to 2016 were estimated at the main outlet of the watershed. The results showed the significant decreasing effect of exclosure treatment on sediment yield at micro-watershed scale (p≤0.05). So that, 582% decrease in sediment yield was obtained in exclosure treatment compared to open grazing. Results also showed seasonal and annual variations of exclosure on hydrological processes so that, maximum and minimum differences in sediment yield among study treatments were founded. The results of this study suggest that livestock grazing management during sensitive seasons as well as rangeland exclosure, if its social problems are resolved, is a practical solution to reduce watershed sedimentation.