بررسي رابطه ي خشكسالي هيدرولوژيكي در واكنش به خشكسالي هواشناسي و اثرات مخزن (مطالعه موردي: حوضه آبريز زاينده رود)

Evaluation of Hydrological and Meteorological Drought Relationship and Reservoir Impacts (Case Study: Zayandeh Rood River Basin

ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ وﻗﻮع ﺧﺸﮑﺴﺎﻟﯽ ﻫﯿﺪروﻟﻮژﯾﮑﯽ ﺑﻌﺪ از ﺧﺸﮑﺴﺎﻟﯽ ﻫﻮاﺷﻨﺎﺳﯽ، ﺗﻌﯿﯿﻦ راﺑﻄﻪ زﻣﺎﻧﯽ ﺑﯿﻦ اﯾﻦ دو ﺧﺸﮑﺴﺎﻟﯽ اﻣﺮي ﺿﺮوري اﺳﺖ. در اﯾﻦ ﻣﻄﺎﻟﻌﻪ، ﺣﻮﺿﻪي آﺑﺮﯾﺰ زاﯾﻨﺪهرود در ﻗﺴﻤﺖ ﻣﺮﮐﺰي اﯾﺮان ﺑﻪﻋﻨﻮان ﻣﻨﻄﻘﻪ ﻣﻄﺎﻟﻌﺎﺗﯽ اﻧﺘﺨﺎب ﮔﺮدﯾﺪ. اﯾﺴﺘﮕﺎهﻫﺎي ﻣﻨﺘﺨﺐ در اﯾﻦ ﺣﻮﺿﻪ ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ ﻣﻮﻗﻌﯿﺖ و روﻧﺪ دادهﻫﺎي ﺑﺎرش آﻧﻬﺎ، اﯾﺴﺘﮕﺎه داﻣﻨﻪ ﻓﺮﯾﺪن، اﯾﺴﺘﮕﺎه ﻗﻠﻌﻪ ﺷﺎﻫﺮخ )ﺑﺎﻻدﺳﺖ ﺳﺪ( و اﯾﺴﺘﮕﺎه ﭘﻞ زﻣﺎنﺧﺎن )ﭘﺎﯾﯿﻦدﺳﺖ ﺳﺪ( در ﻧﻈﺮ ﮔﺮﻓﺘﻪ ﺷﺪه اﺳﺖ. در اﺑﺘﺪا ﺑﺮ اﺳﺎس دادهﻫﺎي ﻣﺎﻫﺎﻧﻪي ﺑﺎرش و ﺟﺮﯾﺎن ﻃﯽ ﺳﺎلﻫﺎي 1360 ﺗﺎ 1389، ﺳﺮيﻫﺎي ﺷﺎﺧﺺ ﺑﺎرش اﺳﺘﺎﻧﺪارد )SPI( و ﺷﺎﺧﺺ ﺟﺮﯾﺎن اﺳﺘﺎﻧﺪارد )SSI( )ﺑﻪ ﺗﺮﺗﯿﺐ ﻧﺸﺎندﻫﻨﺪه ﺧﺸﮑﺴﺎﻟﯽ ﻫﻮاﺷﻨﺎﺳﯽ و ﺧﺸﮑﺴﺎﻟﯽ ﻫﯿﺪروﻟﻮژﯾﮑﯽ(، ﻫﺮ ﯾﮏ ﺑﺎ دوره زﻣﺎﻧﯽ 3 ﻣﺎﻫﻪ ﻣﺤﺎﺳﺒﻪ ﺷﺪﻧﺪ. ﺳﭙﺲ ﺑﺎ اﺳﺘﻔﺎده از ﺗﺌﻮري ران وﯾﮋﮔﯽﻫﺎي ﺧﺸﮑﺴﺎﻟﯽ ﻫﻮاﺷﻨﺎﺳﯽ و ﻫﯿﺪروﻟﻮژﯾﮑﯽ، از ﺟﻤﻠﻪ ﻣﺪت زﻣﺎن و ﻣﻘﺪار ﺧﺸﮑﺴﺎﻟﯽ ﺷﻨﺎﺳﺎﯾﯽ ﮔﺮدﯾﺪ. در اداﻣﻪ ﺑﺎ اﺳﺘﻔﺎده از ﻧﺮماﻓﺰار R و ﺑﺮﻧﺎﻣﻪﻧﻮﯾﺴﯽ در آن، ﺑﻬﺘﺮﯾﻦ ﻣﺪل ﺑﺮاي ﺑﺮرﺳﯽ راﺑﻄﻪ ﺑﯿﻦ ﺧﺸﮑﺴﺎﻟﯽ ﻫﻮاﺷﻨﺎﺳﯽ و ﻫﯿﺪروﻟﻮژﯾﮑﯽ ﻣﻮرد ﭘﺮدازش ﻗﺮار ﮔﺮﻓﺖ. ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ ﺗﻌﺪاد ﻧﻤﻮﻧﻪﻫﺎ، ﻣﺪل اﻋﺘﺒﺎرﺳﻨﺠﯽ ﻫﻢ ﺷﺪ. راﺑﻄﻪاي ﮐﻪ ﺧﺸﮑﺴﺎﻟﯽ ﻫﯿﺪروﻟﻮژﯾﮑﯽ ﺑﻪ ﺧﺸﮑﺴﺎﻟﯽ ﻫﻮاﺷﻨﺎﺳﯽ واﮐﻨﺶ ﻧﺸﺎن ﻣﯽدﻫﺪ ﺑﺎ اﺳﺘﻔﺎده از ﯾﮏ ﻣﺪل ﺗﺎﺑﻊ ﻏﯿﺮﺧﻄﯽ در اﯾﺴﺘﮕﺎه ﻗﻠﻌﻪ ﺷﺎﻫﺮخ و اﯾﺴﺘﮕﺎه ﭘﻞ زﻣﺎنﺧﺎن ﮐﻪ ﺑﻪ ﺗﺮﺗﯿﺐ ﺷﺮاﯾﻂ ﺑﺪون ﻣﺨﺰن و ﺷﺮاﯾﻂ ﺗﺤﺖ ﺗﺄﺛﯿﺮ ﻣﺨﺰن را ﻧﺸﺎن ﻣﯽدﻫﺪ، اﯾﺠﺎد ﻣﯽﮔﺮدد. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ ﯾﮏ راﺑﻄﻪ ﻏﯿﺮﺧﻄﯽ ﺑﯿﻦ ﺧﺸﮑﺴﺎﻟﯽ ﻫﯿﺪروﻟﻮژﯾﮑﯽ و ﺧﺸﮑﺴﺎﻟﯽ ﻫﻮاﺷﻨﺎﺳﯽ وﺟﻮد دارد و آﺳﺘﺎﻧﻪاي ﮐﻪ در آن ﺧﺸﮑﺴﺎﻟﯽ ﻫﯿﺪروﻟﻮژﯾﮑﯽ ﺷﺮوع ﺑﻪ واﮐﻨﺶ ﺑﻪ ﺧﺸﮑﺴﺎﻟﯽ ﻫﻮاﺷﻨﺎﺳﯽ ﻣﯽﮐﻨﺪ ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ ﻣﺪل ﺗﺎﺑﻊ ﻏﯿﺮﺧﻄﯽ ﺑﺪﺳﺖ ﻣﯽآﯾﺪ. ﻣﺪل ﺗﺎﺑﻊ ﻧﻤﺎﯾﯽ ﺑﺎ داﺷﺘﻦ ﺷﺎﺧﺺﻫﺎي اﻋﺘﺒﺎرﺳﻨﺠﯽ ﻣﻨﺎﺳﺐ و ﻫﻤﭽﻨﯿﻦ ﺿﺮﯾﺐ 𝑅2 ﺑﺎﻻ در ﻫﺮ دو اﯾﺴﺘﮕﺎه، ﺑﻪﻋﻨﻮان ﺑﻬﺘﺮﯾﻦ ﻣﺪل اﻧﺘﺨﺎب ﺷﺪ. ﻣﺪت و ﻣﻘﺪار ﺧﺸﮑﺴﺎﻟﯽ ﻫﯿﺪروﻟﻮژﯾﮑﯽ در اﯾﺴﺘﮕﺎه ﻗﻠﻌﻪ ﺷﺎﻫﺮخ ﺑﻪ ﺗﺮﺗﯿﺐ ﺑﺮاﺑﺮ 1/7 و 1/9 اﺳﺖ و ﻫﻤﭽﻨﯿﻦ ﻣﺪت و ﻣﻘﺪار اﯾﻦ ﺧﺸﮑﺴﺎﻟﯽ در اﯾﺴﺘﮕﺎه ﭘﻞ زﻣﺎنﺧﺎن )ﺗﺤﺖ ﺗﺄﺛﯿﺮ ﻣﺨﺰن ﺳﺪ( ﺑﺮاﺑﺮ 0/55 و 1/45 اﺳﺖ. در اﺻﻞ زﻣﺎن وﻗﻮع ﺧﺸﮑﺴﺎﻟﯽ ﻫﯿﺪروﻟﻮژﯾﮑﯽ در ﭘﺎﯾﯿﻦدﺳﺖ ﺳﺮﯾﻊﺗﺮ اﺗﻔﺎق ﺧﻮاﻫﺪ اﻓﺘﺎد. اﯾﻦ ﻣﻄﺎﻟﺐ ﻧﺸﺎن داد ﮐﻪ ﻓﻌﺎﻟﯿﺖﻫﺎي ﻋﻤﻠﯿﺎﺗﯽ ﻣﺨﺰن ﺳﺪ زاﯾﻨﺪهرود ﺑﻪﻃﻮر ﻗﺎﺑﻞﺗﻮﺟﻬﯽ ﻣﺪت و ﻣﻘﺪار ﺧﺸﮑﺴﺎﻟﯽ ﻫﯿﺪروﻟﻮژﯾﮑﯽ را ﻧﺴﺒﺖ ﺑﻪ ﺷﺮاﯾﻂ ﺑﺪون ﻣﺨﺰن، ﮐﺎﻫﺶ ﻣﯽدﻫﺪ.

Regarding the occurrence of hydrological drought after the meteorological drought, determining the relationship between these two droughts is necessary. In this study, the Zayandehrood Basin in the central part of Iran was selected as the study area. Selected stations in this basin; Damane Fereydan station, Ghaleh Shahrokh station (upstream of dam) and Zamankhan bridge station (downstream of dam) were considered according to their location and trend of precipitation data. Initially, on the basis of monthly rainfall and flow data from 1360 to 1389, the standard precipitation index (SPI) and the standard flow index (SSI) (Meteorological droughts and hydrological drought, respectively), each with a three-month period were calculated. Then using the Run theory, the meteorological and hydrological drought characteristics, including the duration and magnitude of drought were identified. In the following, using R software and programming in it, the best model was sought to investigate the relationship between meteorological and hydrological drought. According to the number of samples, the model was also validated. The relationship in which a hydrological drought reacts to the meteorological drought is created using a nonlinear function model in Qaleh Shahrokh and Zaman Khan Bridge stations, which show the condition without the reservoir and the condition affected by the reservoir, respectively. The results showed that there is a nonlinear relationship between hydrological drought and meteorological drought and the threshold at which a hydrological drought begins to react to meteorological drought is achieved with respect to the nonlinear function model. The exponential function model with the appropriate validation indexes as well as high 𝑅2coefficients in both stations was selected as the best model. The duration and magnitude of hydrological drought at Qaleh Shahrokh station is 1.7 and 1.9, respectively. Also, the duration and magnitude of this drought at the Zaman Khan Bridge (under the influence of the dam reservoir) is 0.55 and 1.45. Originally, the time of occurrence of hydrological drought in the downstream of the dam will be occurred faster. These findings indicated that the operational activities of Zayandeh Rud reservoir significantly reduced the duration and amount of hydrological drought as compared to non-reservoir conditions.