ارزیابی عملکرد شبکه‌های آبیاری تحت تأثیر تغییر اقلیم بدون محدودیت منابع آبی (مطالعه موردی: شبکه آبیاری بیله‌سوار، دشت مغان)

نویسندگان

چکیده

هدف از این پژوهش بررسی اثرات تغییر اقلیم بر عملکرد شبکه آبیاری بیله‌سوار است. در این راستا تحت سناریو‌های A2 و B2 داده‌های دما و بارش با استفاده از مدل Hadcm3 برای دوره‌های اقلیمی آتی 39-2010 و 80-2050 برای منطقه تولید شدند. سپس تبخیر و تعرق پتانسیل محاسبه و نیاز آبی جدید برای ارزیابی عملکرد شبکه با این فرض که از نظر عرضه آب به شبکه هیچ‌گونه محدودیتی در آینده وجود نخواهد داشت،‏ به مدل WaterGems داده شد. نتایج حاصل از ریز مقیاس کردن داده‌های دما و بارش نشان دادند که بحرانی‌ترین تغییرات مشاهده شده دما و بارش تحت سناریوی A2 و در ماه‌های ژوئن و جولای است. به‌طوری‌که در دوره 39-2010 دما در این دو ماه به‌ترتیب 1‎/2 و 3‎/2 درجه سلسیوس افزایش و بارش 1‎/21 و 4‎/38 درصد کاهش و در دوره 80-2050 این رقم‌ها برای دما به‌ترتیب 9‎/4 و 1‎/5 درجه سلسیوس افزایش و برای بارش 1‎/52 و 9‎/57 درصد کاهش،‏ نسبت به دوره پایه خواهند داشت. نتایج ارزیابی نشان داد که با افزایش تقاضا در شبکه،‏ شاخص‌های ارزیابی از جمله عدالت و کفایت توزیع فشار به‌ترتیب 7‎/16 و 5‎/21 درصد نسبت به دوره پایه افت پیدا خواهند کرد.

کلیدواژه‌ها


عنوان مقاله [English]

Performance Assessment of Irrigation Networks to Climate Change without Water Resource Restriction (Case Study: Bilesavar Irrigation Network, Moghan)

نویسندگان [English]

  • zohreh dehghan
  • Mahdi Kouchakzadeh
  • Mahdi Alikhasi
  • Farshad Fathian
چکیده [English]

Although the evidence for anthropogenic climate change is overwhelming, it is still standard practice to preface the statement by saying; most climate scientists believe that increasing concentrations of greenhouse gases have led to changes in climate. According to the fifth IPCC report, increasing concentrations of CO2 and other greenhouse gases has led to fundamental changes due to anthropogenic activities in the global climate over the course of the last century. These changes in the climate will lead to changes in water demands of existing irrigation networks. In the agricultural sector, there are multiple variables which will be affected by climate change. For instance, evapotranspiration is controlled by climatic variables (such as temperature, precipitation, net radiation, wind speed and relative humidity), and changes in climatic regimes can affect hydrological processes, yield production, and the development of agricultural activities. Given the importance of agriculture, there is a significant need to understand the implications of climate change on agriculture, to explore different adaptation options and performance and vulnerability assessments of irrigation networks to impacts and adaptation to climate change. Therefore, the analysis of climate change impacts and adaptation strategies to maintain the performance and stability of irrigation systems, as well as improve their efficiency, are necessary. The goal of this paper is to investigate the effects of climate change on performance of irrigation networks, through a case study of a sprinkler irrigation network in Bilesavar, in Northern Iran.
The Bilesavar irrigation network is located in the Moghan plain in Ardebil province, North of Iran (48o15´ to 48o20´ East longitude and 39o 21´ to 39o 28´ North latitude). The Bilesavar irrigation district is 3,200 ha, with 21 field units or sectors and cropping patterns that are devoted to a wide range of crops such as wheat (40%), barley (15%), alfalfa (20%), cotton (20%) and lentil (5%). Also, the general circulation models (GCMs) are used to estimate the future climate change due to continuous increase of greenhouse gas concentrations in the atmosphere,. The outputs of GCMs cannot be used directly for climate change studies, and they do not provide a direct estimation of the hydrological response to climate change. As a result, downscaling techniques are used to convert the coarse spatial resolution of the outputs of GCMs into finer resolutions, which may involve the generation of point/station data of a specific area using GCM climatic output variables. This study used a statistical downscaling method, SDSM, which has been widely applied to downscale GCMs. In this study, the output from the Hadley GCM3 model (HadCM3) was utilized to downscale temperature and rainfall data for the study area. The HadCM3 model is one of the major models used in the IPCC Third and Fourth Assessments, and it also contributed to the Fifth Assessment. Precipitation and temperature data under A2 and B2 scenarios were produced using HadCM3 in the case study for future periods 2010-39 and 2050-80. Then the potential evapotranspiration was considered as new network water demand, with this assumption that the water supply of Bilesavar’s network there will be no restrictions in the future, and entered to WaterGems model for assessing the performance of irrigation network. Finally, the network performance was evaluated on technical and management approach.
The results of temperature and precipitation downscaling showed that the most critical changes of temperature and precipitation will be occurred in June and July months under scenario A2 for 2010-39. In general, scenario A2 results in more increases in temperature than B2 in each time period, and according to these scenarios, higher temperatures will be seen in 2050-79 compared to 2010-39. As compared with the base period, the temperature will be increased 2.1 to 2.3 oC (for 2010-39); 4.9 to 5.1 (for 2050-80) and precipitation will be decreased 21.1 and 38.4 percent (for 2010-39); and 52.1 and 57.9 (for 2050-80) in June and July, respectively. For ETo, scenario A2 results in a higher increase in ETo compared to B2 in all considered periods and ETo is around 6% higher than the baseline for 2010-39 and 12 % for 2050-79. Overall, the situation will be more unfavorable in the months with peak water demand, and the conditions will be more extreme (less precipitation, more temperature and ETo). The results showed that with increasing water demand in the Bilesavar network, assessment indicators such as equity and adequacy of pressure distribution have declined 16.7 and 21.5 percent in comparison with baseline, respectively.

کلیدواژه‌ها [English]

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