راهكارهاي حوضه‌اي و درياچه‌اي بهبود كيفيت آب مخازن سدها (مطالعه موردي: سد شيرين‌دره)

Basin and Reservoir Water Quality Improvement Methods of Dams (Case study: Shirin Darreh Dam

در اين مطالعه، مدل دو­بعدي متوسط­ گيري ­شده در عرض CE-QUAL-W2 براي شبيه­ سازي ترازسطح آب، دماو ﭘﺎراﻣﺘﺮﻫﺎي ﮐﯿﻔﯽ آب ﻣﺨﺰن ﺳﺪ ﺷﯿﺮﯾﻦدره در ﯾﮏ دوره زﻣﺎﻧﯽ ﯾﺎزده ﻣﺎﻫﻪ و در ﺳﺎل آﺑﯽ 1390-91 ﻣﻮرد اﺳﺘﻔﺎده ﻗﺮار ﮔﺮﻓﺘﻪ اﺳﺖ. ﺑﺪﯾﻦﻣﻨﻈﻮر اﺑﺘﺪا ﻣﺪل واﺳﻨﺠﯽ و ﻣﻌﺘﺒﺮﺳﺎزي ﺷﺪ. ﺳﭙﺲ، ﮐﯿﻔﯿﺖ آب ﻣﺨﺰن در ﺣﺎﻟﺖﻫﺎي ﻣﺨﺘﻠﻒ ﮐﺎﻫﺶ ﻣﯿﺰان ﻓﺴﻔﺮ ورودي ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﮔﺮﻓﺖ. در ﻧﻬﺎﯾﺖ، ﺗﺄﺛﯿﺮ ﻣﯿﺰان ﻏﻠﻈﺖ اﮐﺴﯿﮋن ﻣﺤﻠﻮل زﯾﺮﻻﯾﻪ ﺑﺮ ﺑﻬﺒﻮد ﮐﯿﻔﯿﺖ آب ﻣﺨﺰن ﻣﻮرد ﻣﻄﺎﻟﻌﻪ ﻗﺮار ﮔﺮﻓﺖ. ﻧﺘﺎﯾﺞ ﻧﻤﻮﻧﻪﺑﺮداري و ﺷﺒﯿﻪﺳﺎزي، ﮐﺎﻫﺶ ﺷﺪﯾﺪ ﻣﯿﺰان اﮐﺴﯿﮋن ﻣﺤﻠﻮل در زﯾﺮﻻﯾﻪ در دوران ﻻﯾﻪﺑﻨﺪي و اﻓﺰاﯾﺶ ﻏﻠﻈﺖ ﻓﺴﻔﺮ و ﯾﻮﺗﺮوﻓﯿﮏ ﺷﺪن درﯾﺎﭼﻪ را در ﭘﺎﯾﺎن دوره ﺷﺒﯿﻪﺳﺎزي ﻧﺸﺎن ﻣﯽدﻫﺪ. ﻫﻤﭽﻨﯿﻦ ﻧﺘﺎﯾﺞ ﻧﺸﺎن ﻣﯽدﻫﺪ، اﻓﺰاﯾﺶ ﻏﻠﻈﺖ اﮐﺴﯿﮋن زﯾﺮﻻﯾﻪ، ﺑﺎﻋﺚ ﮐﺎﻫﺶ ﻣﯿﺰان آزادﺳﺎزي ﻓﺴﻔﺮ و ﺑﻬﺒﻮد ﮐﯿﻔﯿﺖ آب ﻣﺨﺰن ﻣﯽ-ﺷﻮد. ﺑﻪﻋﻨﻮان ﻣﺜﺎل، ﺑﺎ ﮐﺎﻫﺶ 60 ﺗﺎ 70 درﺻﺪي ﻣﯿﺰان ﻓﺴﻔﺮ ورودي ﺑﻪ ﻣﺨﺰن، ﺷﺮاﯾﻂ ﻣﺨﺰن از ﯾﻮﺗﺮوﻓﯿﮏ ﺑﻪ ﻣﺰوﺗﺮوﻓﯿﮏ ﺗﻐﯿﯿﺮ وﺿﻌﯿﺖ ﻣﯽدﻫﺪ. ﻋﻼوه ﺑﺮ اﯾﻦ، در ﺷﺮاﯾﻂ ﻋﺎدي، ﻣﯿﺰان ﻏﻠﻈﺖ ﻓﺴﻔﺮ در ﻣﺨﺰن ﺑﻪ 50 ﻣﯿﻠﯽﮔﺮم در ﻟﯿﺘﺮ رﺳﯿﺪه ﮐﻪ ﺑﺎ ﺑﻪﮐﺎرﮔﯿﺮي دﺳﺘﮕﺎه اﮐﺴﯿﮋندﻫﯽ، اﯾﻦ ﻣﯿﺰان ﺑﻪ 25 ﻣﯿﻠﯽﮔﺮم در ﻟﯿﺘﺮ ﮐﺎﻫﺶ ﻣﯽﯾﺎﺑﺪ.

In this study, a two-dimensional width averaged model "CE-QUAL-W2" has been used to simulate the water level, temperature and quality of Shirin Darreh Dam during a period of eleven months in years 2012-2013. In this way, the model was calibrated and validated. Then, the reservoir water quality was evaluated for different reduction of the amount of input phosphorus. Finally, the effect of increment of the sub layer oxygen concentration on water reservoir quality improvement was studied. Sampling and simulation results showed a sharp decline in the amount of dissolved oxygen in hypolimnion and an increase in the concentration of phosphorus in this region and so the eutrophic condition of the lake at the end of the simulation. The results also showed that increasing of the sub layer oxygen concentration reduced the amount of phosphorus release and improvement of water quality. For example, the reservoir conditions are changed from eutrophic to mesotrophic, when the amount of phosphorus entering the reservoir reduced 60-70 percent. Furthermore, the phosphorus concentration reached to 50 mg/lit in normal condition which it would be reduced to 25 mg/lit when Oxygenation device was applied.