تغيير مصرف آب کشاورزی با توجه به تغییر اقلیم
محورهای موضوعی : توليد محصولات زراعي
1 - استادیار گروه عمران دانشگاه ازاد اسلامی واحد تهران جنوب
کلید واژه: آب مصرفي, بیلان آب تبخيرتعرق و تغيير اقليم ,
چکیده مقاله :
تغيير اقليم و افزايش دما يكي از مسایل مهم زيست محيطي به حساب مي آيدكه مي‌تواند بركشاورزي يك منطقه اثربگذارد. تبخيروتعرق پتانسيل و نياز آبي محصولات کشاورزی هرمنطقه متاثر از تغييرات اقليمي است. منطقه موردمطالعه درطول جغرافيايي ´20-°58 و ´8-°60 شرقي وعرض جغرافيايي ´0-°36 و ´5-°37 شمالي در استان خراسان رضوي قرارگرفته است . متوسط دماي سالانه منطقه 5/12 درجه سانتی گراد و بارش سالانه6/278 ميلي‌متر است. نتايج نشان مي‌دهدكه نيازآبي محصولات کشاورزی منطقه در50 ساله اخيرو به ويژه در25 سال دوم (1975-2000) داراي روند صعودي است. براساس نتايج مدل جهاني تغيير اقليم، مقادير تبخيرتعرق در منطقه مورد مطالعه براي دوره 2000-2050 محاسبه گرديد. درتمام ماه‌هاي سال نسبت نیازآبی ماهانه 50 ساله آینده به 50 ساله اخير بزرگ‌تر از يك است. اين نسبت بين 05/1 تا 22/1 قرار دارد ونشان دهنده افزايش 22درصدي نيازآبي دردوره منتهي به سال2050 است. حجم كل نياز آبي(خالص) براي الگوي كشت فعلي 410 ميليون مترمكعب درسال برآوردگرديد، درحالي كه اين رقم براي دوره 50 ساله آينده490 ميليون مترمكعب است كه افزايش19 درصدي را شامل مي شود. بر اساس این برآورد نيازآبي براي اغلب محصولات کشاورزی منطقه 22درصد افزايش خواهد داشت که كمترين افزايش درمورد يونجه معادل 14 درصد می باشد. درشرايط تغيير اقليم، مصارف آب در بخش كشاورزي(ناخالص) دراين دشت به 4/1388 ميليون مترمكعب مي رسد كه ازمنابع سالانه بيشتر است.كمبود در شرايط تغيير اقليم به 198% (تقریبا دو برابر) در ماه تير خواهدرسيد. ضريب بحران كم آبي سالانه و ماهانه در شرايط فعلي 98/0 و 4/2 و در شرايط تغيير اقليم 15/1 و 3 خواهد بود. اين اعداد نشان دهنده وضعيت فوق بحراني دراين منطقه است. نتايج نشان مي دهد كه با شرايط گرم شدن هوا و تغيير اقليم ناشي از صنعتي شدن و گازهاي گلخانه اي با فرض خوش بينانه ثابت بودن منابع آب، مصارف آب كشاورزي كه عمده مصرف نيزهست به شدت افزايش خواهد يافت و براي مقابه با آن بايستي راهكارهاي مديريتي اتخاذ گردد.
Climate change and increase in the temperature are important ecological issue in human life which can affect regional agricultures. Evaporation, potential transpiration, and water requirements of the culture pattern in every region are affected by changes in the climates. The studied area is located between 36°00'N & 37°05'N, and 58°20'E & 60°08'E, with an average temperature of 12.5°C and annual precipitation of 278.6 mm. Results assert that water requirement has been ascending within the 50 recent years, especially during the second 25 years (1975-2000). Evapotranspiration for the 2000-2050 periods was calculated by means of The Global Climate Change Model. The ratio of the recent-50-year January to September monthly evapotranspiration to the coming same period is bigger than one; the 1.05-1.22 ratio indicates a 22 percent growth of water requirement in the period ending in 2050. The total net water requirements for the current culture pattern were estimated at 410 million m3 per year; while the figure for the next 50-year period -with a 19 percent of increment- will be 490 million m3. Water requirement for a majority of the culture pattern will be 22 percent up. The least increase was 14 percent, which was calculated for alfalfa. Exceeding the yearly available water supplies, in the changing conditions of climate, agricultural water consumption in the plain touches 1388.4 million m3. Given the climate change, the shortage will reach 198 percent in June and July. The present critical water shortage coefficient of 0.98 (yearly) and 2.4 (monthly) will go up to 1.15 and 2.4. These figures indicate extremely crucial conditions in the region. Findings assert that even optimistically assuming that the water supplies will be enduring, agricultural water consumption (i.e. the major type of consumption) will dramatically increase, due to the warming weather, climate change originated in industrialization, and greenhouse gasses; so managerial solutions are needed to tackle the problem.
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