تحليل خشكسالي هيدرولوژيكي آبهاي زيرزميني دشت مهران با استفاده از شاخص GRI

Hydrological Drought Analysis of Groundwater in Mehran Plain Using GRI Index

ﺧﺸﮑﺴﺎﻟﯽ آب ﻫﺎي زﯾﺮزﻣﯿﻨﯽ زﻣﺎﻧﯽ اﺗﻔﺎق ﻣﯽ اﻓﺘﺪ ﮐﻪ آﺑﻬﺎي زﯾﺮزﻣﯿﻨﯽ ﯾﮏ ﻣﻨﻄﻘﻪ ﺗﺤﺖ ﺗﺎﺛﯿﺮ ﺧﺸﮑﺴﺎﻟﯽ ﻃﻮﻻﻧﯽ ﻣﺪت ﻗﺮار ﮔﯿﺮﻧﺪ، در اﯾﻦ ﻧﻮع ﺧ ﺸﮑ ﺴﺎﻟﯽ اﺑﺘﺪا ﺗﻐﺬﯾﻪ، ﺳﭙﺲ ﺳﻄﺢ اﯾ ﺴﺘﺎﺑﯽ و ﻧﻬﺎﯾﺘﺎً ﻣﯿﺰان ﺗﺨﻠﯿﻪ ﺳﯿ ﺴﺘﻢ ﻫﺎي آﺑﻬﺎي زﯾﺮزﻣﯿﻨﯽ ﺗﺤﺖ ﺗﺎﺛﯿﺮ ﺧﺸــﮑﺴــﺎﻟﯽ ﮐﺎﻫﺶ ﯾﺎﺑﺪ. ﺑﻨﺎﺑﺮاﯾﻦ ﺑﻪ ﻣﻨﻈﻮر آﮔﺎﻫﯽ از وﺿــﻌﯿﺖ ﺧﺸــﮑﺴــﺎﻟﯽ آب ﻫﺎي زﯾﺮزﻣﯿﻨﯽ دﺷﺖ ﻣﻬﺮان در اﺳﺘﺎن اﯾﻼم از ﺷﺎﺧﺺ GRI اﺳﺘﻔﺎده ﮔﺮدﯾﺪ. ﺑﺪﯾﻦ ﻣﻨﻈﻮر آﻣﺎر 23 ﺳﺎل از ﺳﺎل 1375 ﺗﺎ ﺳﺎل 1397 ﺗﻌﺪاد 19 اﯾ ﺴﺘﮕﺎه ﻫﯿﺪروﻣﺘﺮي ﭘﺲ از ﺗﺪﻗﯿﻖ و ﺑﺎز ﺳﺎزي داده ﻫﺎ اﻧﺘﺨﺎب ﺷﺪ. ﭘﺲ از ورود داده ﻫﺎي ﺧﺎم اوﻟﯿﻪ در ﻓﺎﯾﻞ ﻣﺤﺎ ﺳﺒﺎت ﮔﺎم ﺑﻪ ﮔﺎم ﺷﺎﺧﺺ GRI اﻗﺪام ﺑﻪ ﻣﺤﺎ ﺳﺒﻪ ﻣﯿﺎﻧﮕﯿﻦ، LN ، ﻓﺎﮐﺘﻮر U، ﭘﺎراﻣﺘﺮ Shape و ﭘﺎراﻣﺘﺮ Scale، ﻟﮕﺎرﯾﺘﻢ در ﭘﺎﯾﻪ e و ﺗﻮزﯾﻊ اﺣﺘﻤﺎﻟﯽ GAMMA ﺑﺮاي داده ﻫﺎي ورودي و ﻣﺤﺎﺳـــﺒﻪ ﻣﻘﺪار )H(x و ﺗﻔﮑﯿﮏ آن در ﺣﺪ ﺑﯿﻦ 0/5 - 0و 1 - 0/5 و ﻣﺤﺎﺳــﺒﻪ ﭘﺎراﻣﺘﺮ t و Z و در ﭘﺎﯾﺎن اﺳــﺘﺨﺮاج ﻧﺘﺎﯾﺞ ﻧﻬﺎﯾﯽ ﻣﺤﺎﺳــﺒﻪ ﺷــﺎﺧﺺ GRI ﺑﺎ ﺗﺮﮐﯿﺐ ﻣﺤﺎﺳــﺒﺎت ﻣﻮﺟﻮد در دو ﺟﺪول ﻧﻬﺎﯾﯽ. ﻧﺘﺎﯾﺞ ﺗﺤﻘﯿﻖ ﻧﺸــﺎن ﻣﯽ دﻫﺪ ﮐﻪ ﺧ ﺸﮑ ﺴﺎﻟﯽ د ﺷﺖ ﻣﻬﺮان از ﺳﺎل 1375 ﺗﺎ ﺳﺎل 1388 ﻧﺰدﯾﮏ ﻧﺮﻣﺎل اﻟﺒﺘﻪ ﺑﺎ ﯾﮏ ﻧﻮ ﺳﺎن ﺷﺪﯾﺪ ﺑﻮده و از ﺳﺎل 1388 ﺗﺎ 1397 دﭼﺎر ﺧﺸﮑﯽ ﻣﻼﯾﻢ ﺷﺪه اﺳﺖ.

Groundwater drought occurs when the groundwater of an area is affected by prolonged drought. In this type of drought, first the feeding, then the water level and finally the discharge of groundwater systems due to drought are reduced. Therefore, in order to know the drought status of groundwater in Mehran plain in Ilam province, GRI index was used. For this purpose, statistics of 23 years from 1996 to 1397, 19 hydrometric stations were selected after verifying and reconstructing the data. After entering the primary raw data in the step-by-step calculation file of the GRI index, calculate the mean, LN, U factor, Shape parameter and Scale parameter, logarithm in base e and possible GAMMA distribution for the input data and calculate the value of H (x) an‎d its separation in the range between 0.5-0 and 1.5-1 and the calculation of the parameter t and Z and at the end of extracting the final results of the calculation of the GRI index by combining the calculations in the two final tables. The results show that the drought in Mehran plain from 1375 to 1388 is close to normal, but with a sharp fluctuation and from 1388 to 1397 has suffered mild drought.