تغييرات زماني و مكاني تراز آب‌زيرزميني دشت‌ قروه و دهگلان و رابطه‌ آن با خشكسالي

Spatial and Temporal Variations of Groundwater Level in Qorveh-Dehgolan Plain and its Relationship with Drought

در سال­ هاي اخير پديده خشكسالي باعث كاهش شديد آب­هاي سطحي در دشت قروه و دهگلان شده است. اين امر ﻣﻮﺟﺐ اﻓﺰاﯾﺶ ﺑﻬﺮهﺑﺮداري از ﻣﻨﺎﺑﻊ آبزﯾﺮزﻣﯿﻨﯽ و ﺗﺸـﺪﯾﺪ اﻓﺖ ﺳﻄﺢ اﯾﺴﺘﺎﺑﯽ ﺳﻔﺮه ﻫﺎي اﯾﻦ دﺷﺖ ﮔﺮدﯾﺪه اﺳﺖ. ﻫﺪف از اﯾﻦ ﭘﮋوﻫﺶ ﺑﺮرﺳــﯽ واﮐﻨﺶ آبﻫﺎي زﯾﺮزﻣﯿﻨﯽ دﺷــﺖ ﻗﺮوه و دﻫﮕﻼن ﻧﺴــﺒﺖ ﺑﻪ وﻗﻮع ﺧﺸــﮑﺴــﺎﻟﯽﻫﺎ و ﺗﺮﺳــﺎﻟﯽﻫﺎ و ﻧﯿﺰ ﻣﯿﺰان ﻫﻤﺒﺴـﺘﮕﯽ ﺑﯿﻦ آن ﻫﺎﺳـﺖ. اﺑﺘﺪا ﻣﺸـﺨﺼـﻪ ﻫﺎي ﺧﺸـﮑﺴـﺎﻟﯽ ﻫﻮاﺷـﻨﺎﺳﯽ و ﻫﯿﺪروژﺋﻮﻟﻮژﯾﮑﯽ ﺑﻪﺗﺮﺗﯿﺐ ﺑﺎ اﺳﺘﻔﺎده از ﺷـﺎﺧﺺ ﺑﺎرش اﺳـﺘﺎﻧﺪارد ﺷـﺪه )(SPI و ﺷـﺎﺧﺺ ﻣﻨﺒﻊ آب زﯾﺮزﻣﯿﻨﯽ )(GRI ﻣﺤﺎﺳـﺒﻪ ﺷﺪ. ﺳﭙﺲ ﺿﺮﯾﺐ ﻫﻤﺒﺴﺘﮕﯽ ﺑﯿﻦ ﺷــﺎﺧﺺ SPI و GRI ﺑﺪون اﻋﻤﺎل ﺗﺄﺧﯿﺮ زﻣﺎﻧﯽ و ﺑﺎ24 ،21 ،18 ،15 ،12 ،9 ،6 ،3 ،1 و 48 ﻣﺎه ﺗﺄﺧﯿﺮ ﻣﺤﺎﺳــﺒﻪ ﺷــﺪ. ﻧﺘﺎﯾﺞ ﻧﺸــﺎن داد ﮐﻪ ﺑﯿﺸــﺘﺮﯾﻦ ﻣﻘﺎدﯾﺮ ﺿــﺮاﯾﺐ ﻫﻤﺒﺴــﺘﮕﯽ ﻣﺜﺒﺖ ﻣﻌﻨﯽ دار ﺑﯿﻦ 24-SPI و 48-GRI ﺑﺎ ﺗﺄﺧﯿﺮ 48 ﻣﺎﻫﻪ ﺑﻮده و در 89/8 درﺻــﺪ از ﭼﺎهﻫﺎ SPI ﺑﺎ GRI ﺑﺎ ﺗﺄﺧﯿﺮ 48 ﻣﺎﻫﻪ ﻫﻤﺒﺴــﺘﮕﯽ ﻣﺜﺒﺖ ﻣﻌﻨﯽدار داﺷــﺘﻪ اﺳــﺖ . ﺑﻨﺎﺑﺮاﯾﻦ ﺧﺸــﮑﺴــﺎﻟﯽ ﻫﯿﺪروژﺋﻮﻟﻮژﯾﮑﯽ ﺑﺎ ﺗﺄﺧﯿﺮ زﻣﺎﻧﯽ ﻧﺴـﺒﺖ ﺑﻪ ﺧﺸـﮑﺴـﺎﻟﯽ ﻫﻮاﺷﻨﺎﺳﯽ اﺗﻔﺎق اﻓﺘﺎده اﺳﺖ. ﺑﺮاي ﺑﺮرﺳﯽ وﺟﻮد و ﯾﺎ ﻋﺪم وﺟﻮد روﻧﺪ در ﺗﻐﯿﯿﺮات ﺳـﻄﺢ آب زﯾﺮزﻣﯿﻨﯽ از آزﻣﻮن ﻣﻦ- ﮐﻨﺪال اﺳﺘﻔﺎده ﮔﺮدﯾﺪ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ در ﺳﻄﺢ اﻃﻤﯿﻨﺎن 99% در ﻃﻮل دوره آﻣـﺎري ﻣﻮرد ﻣﻄـﺎﻟﻌـﻪ ﺳـــﻄﺢ ﺗﺮاز آب ﭼـﺎه ﻫـﺎي ﭘﯿﺰوﻣﺘﺮي ﮐـﺎﻫﺶ ﯾﺎﻓﺘﻪ اﺳـــﺖ و ﻣﺘﻮﺳـــﻂ ﮐﺎﻫﺶ ﺗﺮاز آبزﯾﺮزﻣﯿﻨﯽ در ﻣﻨﻄﻘﻪ 0/82 ﻣﺘﺮ در ﺳـﺎل ﺑﻮد. ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ ﻧﻘﺸﻪ ﻫﺎي ﭘﻬﻨﻪﺑﻨﺪي، ﺑﯿﺸﺘﺮﯾﻦ روﻧﺪ ﺗﻐﯿﯿﺮات ﺳﻄﺢ آبزﯾﺮزﻣﯿﻨﯽ ﻣﺮﺑﻮط ﺑﻪ ﺑﺨﺶ ﻣﺮﮐﺰي دﺷﺖ اﺳﺖ ﮐﻪ ﺑﯿﻦ 1/5 ﺗﺎ 2/4 ﻣﺘﺮ در ﺳﺎل ﻣﯽﺑﺎﺷﺪ.

In recent years, drought caused a sharp decline in surface water resources in Qorveh-Dehgolan plain. This caused increasing exploitation of groundwater resources and exacerbation of aquifer level declining. The aim of this study is to evaluate interaction between groundwater and drought and wet periods in Qorveh-Dehgolan as well as to determinate correlation between them. At first, meteorological and hydrogeological drought characteristics were calculated by Standardized Precipitation Index (SPI) and Groundwater Resource Index (GRI), respectively. Then correlation coefficient between SPI and GRI were calculated without lag time also with 1, 3, 6, 9, 12, 15, 18, 21, 24 and 48 months lag times. The results showed that the highest value of positive and significant correlations were between 24-month SPI and 48-month GRI with 48 months delay and in 89.8% of wells, SPI and GRI had positive and significant correlation with 48 months delay. Therefore, the hydrological drought happened with lag time to meteorological drought. The Mann-Kendall test was used for determinating the trend existence or inexistence in groundwater level changes. The results showed that the water level of piezometer wells declined during the studied period at 99% confidence level. The average of groundwater level declining was 0.82 m/year. Regarding to the plotted maps, the steepest trend of groundwater level happened in central parts of Qorveh-Dehgolan plain that was between 1.5-2.4 m/year.