بررسي تأثير كاشت تاغ‌زارها بر منابع آب زيرزميني (مطالعۀ موردي: دشت جعفريۀ قم)

Investigation of the effect of Haloxylon planted on groundwater resources (Case study: Jafarieh plain Qom)

ازﺟﻤﻠﻪ ﮔﯿﺎﻫﺎن ﺳﺎزﮔﺎر ﺑﺎ ﻣﻨﺎﻃﻖ ﺧﺸﮏ و ﻧﯿﻤﻪﺧﺸﮏ، ﮔﻮﻧﻪﻫﺎي ﻣﺨﺘﻠﻒ ﺟﻨﺲ ﺗﺎغ ﻫﺴﺖ ﮐﻪ ﺑﻪ دﻟﯿﻞ ﺑﺮﺧﻮرداري از ﺷﺮاﯾﻂ ﻣﻨﺎﺳﺐ ﺳﺎﺧﺘﺎري و ﺳﯿﺴﺘﻢ رﯾﺸﻪاي ﻋﻤﯿﻖ و ﻣﻨﺎﺳﺐ، ﻗﺎدر ﺑﻪ اﺳﺘﻔﺎده از ﻣﻨﺎﺑﻊ آب زﯾﺮزﻣﯿﻨﯽ ﻫﺴﺘﻨﺪ؛ ﻟﺬا درك و ﭘﺬﯾﺮش ﺗﺄﺛﯿﺮ ﺗﺎغ ﺑﺮ ﻣﻨﺎﺑﻊ آﺑﯽ ﻣﺤﺪود ﻣﻮﺟﻮد در اﯾﻦ ﻣﻨﺎﻃﻖ ﺑﻪ ﻣﺪﯾﺮﯾﺖ ﺑﻬﺘﺮ ﻣﻨﺎﺑﻊ آﺑﯽ و اﮐﻮﺳﯿﺴﺘﻢﻫﺎي ﻃﺒﯿﻌﯽ ﮐﻤﮏ ﺧﻮاﻫﺪ ﮐﺮد. ﻫﺪف از ﺗﺤﻘﯿﻖ ﺣﺎﺿﺮ ﺑﺮرﺳﯽ ﺗﺄﺛﯿﺮ ﺟﻨﮕﻞﻫﺎي دﺳﺖﮐﺎﺷﺖ ﺗﺎغ ﺑﺮ ﻣﻨﺎﺑﻊ آب زﯾﺮزﻣﯿﻨﯽ در دﺷﺖ ﺟﻌﻔﺮﯾﮥ ﻗﻢ ﻣﯽﺑﺎﺷﺪ. ﺑﻪﻣﻨﻈﻮر دﺳﺖﯾﺎﺑﯽ ﺑﻪ اﯾﻦ ﻫﺪف، اﺑﺘﺪا ﺑﺎ اﺳﺘﻔﺎده از ﺗﺼﺎوﯾﺮ ﻣﺎﻫﻮارهاي و ﺑﻬﺮهﮔﯿﺮي از ﻧﺮماﻓﺰار JMicroVision، ﺗﻌﺪاد ﭘﺎﯾﻪﻫﺎي ﺗﺎغ ﻣﻮﺟﻮد در اﯾﻦ ﺟﻨﮕﻞﻫﺎ ﻣﻮرد ﺷﻤﺎرش ﻗﺮارﮔﺮﻓﺖ. ﺳﭙﺲ ﺑﺎ اﺳﺘﻔﺎده از ﺣﺪاﻗﻞ ﻧﯿﺎز آﺑﯽ ﺳﺎﻻﻧﮥ ﻫﺮ ﭘﺎﯾﻪ ﺗﺎغ ﮐﻪ ﺑﺮ اﺳﺎس ﻣﻄﺎﻟﻌﺎت ﻻﯾﺴﯿﻤﺘﺮي ﺑﻪدﺳﺖ آﻣﺪه اﺳﺖ، ﺗﻌﺪاد ﭘﺎﯾﻪﻫﺎي ﺗﺎغ ﻣﺎزاد ﺑﺮ ﺑﺎرﻧﺪﮔﯽ مﻧﻄﻘﻪ و ﻧﯿﺎز آﺑﯽ آنﻫﺎ ﻣﺤﺎﺳﺒﻪ ﮔﺮدﯾﺪ. ﺳﭙﺲ ﺑﺎ اﺳﺘﻔﺎده از ﻧﺮماﻓﺰار GMS 8.3 و ﮐﺪ MODFLOW ، وﺿﻌﯿﺖ ﺗﺮاز ﺳﻄﺢ آب زﯾﺮزﻣﯿﻨﯽ دﺷﺖ ﺟﻌﻔﺮﯾﻪ ﻣﺪلﺳﺎزي ﮔﺮدﯾﺪ. ﺑﺮ اﺳﺎس ﻧﺘﺎﯾﺞ اﯾﻦ ﭘﮋوﻫﺶ ﻣﯽﺗﻮان ﮔﻔﺖ ﮐﻪ ﺗﻌﺪاد 3746291 ﺗﺎغ در دﺷﺖ ﺟﻌﻔﺮﯾﻪ وﺟﻮد دارد ﮐﻪ ﻣﯿﺰان ﺗﺨﻠﯿﮥ آب زﯾﺮزﻣﯿﻨﯽ ﺗﻮﺳﻂ ﺗﺎغزارﻫﺎ ﺑﺮاﺑﺮ 56/194 ﻣﯿﻠﯿﻮن ﻣﺘﺮﻣﮑﻌﺐ ﺑﺮآورد ﮔﺮدﯾﺪ. ﻧﺘﺎﯾﺞ ﺣﺎﺻﻞ از ﺑﺮرﺳﯽ ﺗﺮاز آﺑﺨﻮان ﺣﺎﮐﯽ از آن ﺑﻮد ﮐﻪ اﻓﺖ ﺗﺮاز آب زﯾﺮزﻣﯿﻨﯽ ﺳﺎﻻﻧﻪ ﺑﻪﻃﻮر ﻣﺘﻮﺳﻂ 0/46 ﻣﺘﺮ در دورة اول ﻣﻄﺎﻟﻌﺎﺗﯽ )1371-1380( و 0/93 ﻣﺘﺮ در دورة دوم )1381-1391( ﻣﻄﺎﻟﻌﺎﺗﯽ ﺑﻮده اﺳﺖ. ﺑﻪ ﻋﺒﺎرﺗﯽ اﻓﺖ ﺗﺮاز آب زﯾﺮزﻣﯿﻨﯽ در دورة دوم 2/02 ﺑﺮاﺑﺮ دورة اول ﻣﯽﺑﺎﺷﺪ ﮐﻪ اﯾﻦ اﻣﺮ ﻧﺸﺎندﻫﻨﺪة اﻓﺖ ﺷﺪﯾﺪ ﺗﺮاز آب زﯾﺮزﻣﯿﻨﯽ در دﻫﮥ اﺧﯿﺮ ﮐﻪ ﮐﺎﺷﺖ ﺗﺎغ ﺻﻮرت ﮔﺮﻓﺘﻪ اﺳﺖ، ﻣﯽﺑﺎﺷﺪ. ﻫﺮ ﭼﻨﺪ اﺛﺮات ﻣﺜﺒﺖ ﺗﺎغﮐﺎريﻫﺎي ﻣﻮﺟﻮد در راﺑﻄﻪ ﺑﺎ ﮐﺎﻫﺶ ﺧﺴﺎرات ﻃﻮﻓﺎنﻫﺎي ﮔﺮد و ﻏﺒﺎر و رﯾﺰﮔﺮدﻫﺎ در ﻣﻘﺎﺑﻞ ﻣﺼﺮف اﯾﻦ ﺣﺠﻢ آﺑﯽ را ﻧﺒﺎﯾﺪ ﻧﺎدﯾﺪه ﮔﺮﻓﺖ.

Investigation of the effect of plant community on limited water resources of deserts is an important issue in water resources management. Different species of Haloxylon are compatible with desert condition and can use groundwater resources due to deep roots and proper structural condition. The purpose of this study was investigation of the effect of Haloxylon planted forests on groundwater resources in Jafarieh plain. For doing the study, at first the number of Haloxylon plants was determined in these forests using satellite images and JMicroVision software. Then using minimum water requirement of each plant, estimated with lysimeter, the number of surplus plants was determined based on their water requirement and rainfall of the region. Then groundwater level status was determined using GMS 8.3 software and MODFLOW model. The results showed that the number of Haloxylon plants in the study area was equal to 3746291 and the amount of groundwater evacuation by these plants was equal to 56.194 Mm3. The reduction of groundwater table was about 0.46 meter in the first study period (1992-2001) and 0.93 meter in the second study period (2002-2012) so that the reduction of groundwater level in the second study period was about 2 times bigger than the first study. This results showed that severe reduction of groundwater table has happened in recent decade because of planting Haloxylon. However the positive effects of these forests on reducing damages of dust storms should not be ignored.