بررسي رابطه تغييرات آب زيرزميني و شاخص خشكسالي (مطالعه موردي: حوزه آبخيز شريف آباد در استان قم)

The Investigation of the relationship between groundwater level variation and drought index (Case study: Sharifabad Watershed in Qom Province)

زﻣﯿﻨﻪ و ﻫﺪف: ﭘﺪﯾﺪه ﺗﻐﯿﯿﺮ اﻗﻠﯿﻢ ﺑﺎ ﺗﻐﯿﯿﺮ در ﻣﯿﺰان ﺑﺎرش، ﺑﺮ ﻣﯿﺰان آب ﻣﻮﺟﻮد در آﺑﺨﻮانﻫﺎ ﺗﺄﺛﯿﺮ ﻣﯽﮔﺬارد. در اﯾﻦ ﺗﺤﻘﯿﻖ ﻫﺪف آن اﺳﺖ ﮐﻪ اﺑﺘﺪا ﻣﯿﺰان ﻣﺘﻮﺳﻂ آب زﯾﺮزﻣﯿﻨﯽ ﺑﺎ اﺳﺘﻔﺎده از ﻣﻨﺎﺳﺐﺗﺮﯾﻦ روش زﻣﯿﻦ آﻣﺎر ﺑﺮآورد ﮔﺮدد و ﺳﭙﺲ راﺑﻄﻪ ﺷﺎﺧﺺ آب زﯾﺮزﻣﯿﻨﯽ ﺑﺎ ﯾﮑﯽ از ﺷﺎﺧﺺﻫﺎي ﺧﺸﮑﺴﺎﻟﯽ در ﻣﻘﯿﺎس ﻣﺎﻫﺎﻧﻪ و ﺳﺎﻻﻧﻪ ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﮔﯿﺮد ﮐﻪ اﻫﻤﯿﺖ ﺑﺎرش در ﺗﻐﺬﯾﻪ آب زﯾﺮزﻣﯿﻨﯽ ﻣﺸﺨﺺ ﺷﻮد. روش ﺑﺮرﺳﯽ: ﺣﻮزه آﺑﺨﯿﺰ ﻣﻮرد ﻣﻄﺎﻟﻌﻪ، ﺣﻮزه آﺑﺨﯿﺰ ﺷﺮﯾﻒ آﺑﺎد واﻗﻊ در اﺳﺘﺎن ﻗﻢ ﺑﺎ وﺳﻌﺖ آﺑﺨﻮان27035/2 ﻫﮑﺘﺎر ﻣﯽ ﺑﺎﺷﺪ. در اﯾﻦ ﻣﻨﻄﻘﻪ 16 ﭼﺎه ﻣﺸﺎﻫﺪاﺗﯽ داراي آﻣﺎر ﻣﯽﺑﺎﺷﻨﺪ ﮐﻪ در اﯾﻦ ﻣﻄﺎﻟﻌﻪ، ﺳﻄﺢ اﯾﺴﺘﺎﺑﯽ ﭼﺎه ﻫﺎي ﻣﺸﺎﻫﺪاﺗﯽ ﻣﻨﻄﻘﻪ در ﻃﯽ ﺑﺎزه زﻣﺎﻧﯽ 1384-1394 ﺑﺎ اﺳﺘﻔﺎده از ﻣﺪلﻫﺎي وارﯾﻮﮔﺮاﻣﯽ ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﮔﺮﻓﺖ و ﻣﺘﻮﺳﻂ ﺳﻄﺢ اﯾﺴﺘﺎﺑﯽ در ﻫﺮ ﺳﺎل ﺑﺎ اﺳﺘﻔﺎده از ﺑﻬﺘﺮﯾﻦ ﻣﺪل ﺗﻌﯿﯿﻦ ﮔﺮدﯾﺪ. ﺳﭙﺲ ﺷﺎﺧﺺ SWI در ﺣﻮزه آﺑﺨﯿﺰ ﻣﺤﺎﺳﺒﻪ ﺷﺪ. ﻫﻤﭽﻨﯿﻦ در اﯾﻦ ﺗﺤﻘﯿﻖ از ﺷﺎﺧﺺ SPI ﮐﻪ ﯾﮑﯽ از ﺷﺎﺧﺺﻫﺎي ﺧﺸﮑﺴﺎﻟﯽ اﺳﺖ اﺳﺘﻔﺎده ﺷﺪه و ﺑﺎ اﺳﺘﻔﺎده از ﺿﺮﯾﺐ ﭘﯿﺮﺳﻮن، ﻫﻤﺒﺴﺘﮕﯽ اﯾﻦ ﺷﺎﺧﺺ ﻫﺎ در ﻣﻘﯿﺎس ﻣﺎﻫﺎﻧﻪ و ﺳﺎﻻﻧﻪ ﺑﺮرﺳﯽ ﺷﺪ. ﯾﺎﻓﺘﻪ ﻫﺎ: ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ در ﻣﯿﺎن ﻣﺪلﻫﺎي وارﯾﻮﮔﺮاﻣﯽ ﮐﻪ ﺑﺮاي درونﯾﺎﺑﯽ داده ﻫﺎي ﻣﺎﻫﺎﻧﻪ ﺳﻄﺢ اﯾﺴﺘﺎﺑﯽ اﻋﻤﺎل ﺷﺪ، ﻣﻨﺎﺳﺐﺗﺮﯾﻦ ﻣﺪل ﮐﺮﯾﺠﯿﻨﮓ اﺳﺖ. ﻫﻤﭽﻨﯿﻦ ﺿﺮﯾﺐ ﻫﻤﺒﺴﺘﮕﯽ ﭘﯿﺮﺳﻮن ﺑﯿﻦ دو ﺷﺎﺧﺺ SWI و SPI در ﻣﻘﯿﺎس ﻣﺎﻫﺎﻧﻪ و در ﺳﻄﺢ اﻋﺘﻤﺎد 99% در ﭼﺎه ﻫﺎي ﻣﻮرد ﺑﺮرﺳﯽ ﻣﻌﻨﯽ دار ﻧﻤﯽﺑﺎﺷﺪ. ﻫﻤﭽﻨﯿﻦ اﯾﻦ ﺿﺮﯾﺐ ﻫﻤﺒﺴﺘﮕﯽ در ﻣﻘﯿﺎس ﺳﺎﻻﻧﻪ ﻧﯿﺰ ﻣﻌﻨﯽدار ﻧﯿﺴﺖ. ﻧﺘﯿﺠﻪ ﮔﯿﺮي: در اﯾﻦ ﺗﺤﻘﯿﻖ ﻣﻌﻨﯽدار ﻧﺒﻮدن ﻫﻤﺒﺴﺘﮕﯽ ﺑﯿﻦ ﺷﺎﺧﺺ ﺧﺸﮑﺴﺎﻟﯽ SPIو ﺷﺎﺧﺺ آب زﯾﺮزﻣﯿﻨﯽ در ﻣﻨﻄﻘﻪ ﻣﻮرد ﻣﻄﺎﻟﻌﻪ در ﻣﻘﯿﺎس ﻣﺎﻫﺎﻧﻪ و ﺳﺎﻻﻧﻪ ﺑﯿﺎﻧﮕﺮ آن اﺳﺖ ﮐﻪ اﮔﺮ ﺑﯿﻼن آﺑﯽ در اﯾﻦ ﮔﻮﻧﻪ ﻣﻨﺎﻃﻖ درﻧﻈﺮ ﮔﺮﻓﺘﻪ ﺷﻮد، ﺑﺎرش ﺳﻬﻢ ﻧﺎﭼﯿﺰي در ﺗﻐﺬﯾﻪ آب زﯾﺮزﻣﯿﻨﯽ دارد. ﻟﺬا ﻣﯽﺗﻮان ﻧﺘﯿﺠﻪ ﮔﯿﺮي ﻧﻤﻮد ﺑﺨﺶ اﻋﻈﻢ ﺑﺎرش ﻣﻨﻄﻘﻪ ﺑﻪ ﻋﻠﺖ ﺗﺒﺨﯿﺮ و ﺗﻌﺮق زﯾﺎد از دﺳﺘﺮس ﺧﺎرج ﻣﯽﺷﻮد و ﻗﺎدر ﺑﻪ ﺗﻐﺬﯾﻪ آﺑﺨﻮان ﻧﻤﯽﺑﺎﺷﺪ.

Background and objective: The climate change phenomenon affects water storage in aquifers through changes in rainfall volume. In this study, the aim is to estimate the average groundwater level using the most appropriate geostatistical method and then investigate the relationship between groundwater index and one of the drought indices on monthly and annual scale in order to specify the importance of rainfall in groundwater recharge. Method: The watershed of this study was Sharifabad watershed located in Qom province with an aquifer area of 27035/2 hectares. There are 16 observation wells in this area. In this study, during the period of 1384-1384, the water level of observation wells in the area was investigated using variogram models. The average water level was determined using the best model per year, then the SWI index at the watershed was calculated. The SPI index, one of the drought indicators, was also used to investigate precipitation variation and then, using Pearson coefficient, the correlation of these indices was investigated on monthly and annual scale. Findings: The results showed that among the variogram models that were used to interpolate the monthly water level data, Kriging model is the most appropriate. Also, Pearson correlation coefficient between SWI and SPI indicators is not significant on monthly basis at confidence level of 99% in both observations of Mozafarabad and Alborz. Moreover; this correlation coefficient on the annual scale is not meaningful either. Discussion and Conclusion: In this study, the insignificance relationship between SPI and groundwater index in the study area indicates that precipitation has a small proportion in groundwater recharge in the water balance of these areas on monthly and annual scale. Therefore, it can be concluded that the most part of rainfall is out of reach due to excessive evapotranspiration and is not able to recharge the aquifer in the region.