برآورد ردپای آب و آب مجازی برای تعیین الگوی کشت بهینه؛ مطالعه موردی: شهرستان‌های قائنات و زیرکوه

برای اجتناب از پیامد های منفی بیلان منفی آب در شهرستان‌های قائنات و زیرکوه، محدودیت کشت محصولات زراعی با نیاز آبی بالا ضروری است. در این پژوهش با استفاده از برنامه ریزی غیرخطی چندهدفه (mop)، الگوی کاشت بهینه با هدف حداکثرسازی سودخالص و حداقل سازی آب مجازی، ردپاهای آب سبز، آبی، خاکستری و سفید محصولات زراعی منطقه قائنات و زیرکوه پیشنهاد شده است. در تمامی محصولات مورد مطالعه، ردپای آب آبی بیش از سایر اجزای ردپای آب بود که نشان‌دهنده اتکای زراعت بر منابع آب های سطحی و زیرزمینی است. در مدل mop سطح زیر کشت سیب‌زمینی، خربزه و جو قائنات و سطح زیر کشت خربزه، چغندرقند، سیب زمینی، هندوانه، یونجه و زعفران زیرکوه نسبت به الگوی جاری افزایش یافت. کاهش سطح زیر کشت 50 درصدی پنبه، یونجه، هندوانه قائنات و پنبه، گندم و جو زیرکوه در الگوی mop از دیگر موارد مهم نتایج بود. با تعیین الگوی کشت بهینه می توان اثرات محیطی کشاورزی بر منابع آب را کاهش داد، به‌طوری‌که اجرای این الگو در منطقه کاهش 26 درصدی آب مجازی، چهار درصدی ردپای آب آبی، 18 درصدی ردپای آب خاکستری به‌میزان 368779 تن در هکتار نسبت به وضع موجود را نتیجه داد. با توجه به یافته‌های این مطالعه توجه به اهداف محیطی موثر بر منابع آب در بهینه‌سازی الگوی کشت ضروری است. با استفاده از مدل پیشنهادی می توان علاوه‌بر انتخاب الگوی مناسب و استفاده بهینه از منابع آب و زمین، در حدود 13 میلیون‏مترمکعب آب را نسبت به الگوی جاری در منطقه ذخیره کرد.

Use of Water Footprint and Virtual Water to Determine the Optimal Cropping Pattern; Case Study: Ghaenat and Zirkoh Counties

IntroductionManagement of water consumption in arid and semiarid regions in recent years has been considered a key issue in the field of water resources management. Zirkoh and Ghaenat counties are the hot spots of water consumption in the region. Water footprint and virtual water are critical indicators for water resources management. Therefore, the development of the cropping pattern with high water requirements has led to a negative water balance in the Ghaenat and Zirkoh counties. To prevent the negative consequences of this crisis, it is necessary to consider the restriction of cropping pattern with high water requirements in the region, as well as the assessment of water footprint and virtual water of agricultural products. Also, one of the strategies for managing and optimizing the consumption of water resources in the region is to determine the appropriate cropping pattern with regard to the local conditions. Therefore, this study has been conducted with the aim of calculating the components of water footprint and virtual water in the cropping patterns of Zirkoh and Ghaenat counties and determining the optimal cropping pattern for planting crops from the perspective of water footprint.Materials and MethodsIn this study, the amount of virtual water and green, blue, gray, and white water footprint for wheat, barley, potato, sugar beet, cotton, alfalfa, and saffron were calculated in the current cropping pattern and at multiobjective nonlinear programming (MOP) approach with the objectives of maximizing net profit and minimizing virtual water, green, blue, gray and white water footprint as the optimal cropping pattern in Ghaenat and Zirkoh counties. The study area was irrigated areas of Zirkoh and Ghaenat counties in 2017.Results and DiscussionThe results showed that the indices of virtual water and water footprint components in Zirkoh county were higher than in Ghaenat county. Also, in two counties, the blue water footprint was more than the green water footprint, and the results showed that a large amount of water resources in this area is spent on the production of cotton. In all studied crops, blue water footprint was more than other components of water footprint, which shows the reliance on the surface and subsurface water resources. The results also showed that the area under cultivation of potatoes, melons, and barley in the multiobjective pattern of Ghaenat and the area under cultivation of melons, sugar beets, potatoes, watermelons, alfalfa, and saffron increased compared to the current cropping pattern. Reduction of the area under cultivation of cotton, alfalfa, and watermelon in Ghaenat county and cotton, wheat, and barley in Zirkoh county by 50% in the multiobjective crop pattern were other important results. By determining the optimal cropping pattern, the environmental effects of the agricultural sector on water resources could be reduced so that the implementation of this pattern in the region reduced virtual water by 26%, blue water footprint by 4%, gray water footprint by 18% compared to the current cropping pattern.ConclusionAccording to the findings of this study, it is necessary to pay attention to the environmental objectives affecting water resources in optimizing cropping patterns. Using the proposed model, in addition to selecting the appropriate model and optimal use of water and land resources to increase profits and reduce water and virtual water footprint, about 13 million cubic meters of water could be saved compared to the current cropping pattern in the region. Therefore, by implementing the optimal cropping pattern, in addition to reducing the environmental effects, the net income could be maximized of water consumed per cubic meter in the region, and by reducing water consumption, we can help achieve sustainable consumption of limited water resources in the region.Materials and Methods: In this study, the amount of virtual water and green, blue, gray, and white water footprint for wheat, barley, potato, sugar beet, cotton, alfalfa, and saffron were calculated in the current cropping pattern and at multiobjective nonlinear programming (MOP) approach with the objectives of maximizing net profit and minimizing virtual water, green, blue, gray and white water footprint as the optimal cropping pattern in Ghaenat and Zirkoh counties. The study area was irrigated areas of Zirkoh and Ghaenat counties during 2017. Results and Discussion: The results showed that the indices of virtual water and water footprint components in Zirkoh county were higher than Ghaenat county. Also, in two counties, the blue water footprint was more than the green water footprint and the results showed that a large amount of water resources in this area is spent on the production of cotton. In all studied crops, blue water footprint was more than other components of water footprint, which shows the reliance on surface and subsurface water resources. The results also showed that the area under cultivation of potatoes, melons, and barley in the multiobjective pattern of Ghaenat and the area under cultivation of melons, sugar beets, potatoes, watermelons, alfalfa, and saffron increased compared to the current cropping pattern. Reduction of area under cultivation of cotton, alfalfa, watermelon in Ghaenat county and cotton, wheat and barley in Zirkoh county by 50% in the multiobjective crop pattern were other important results. By determining the optimal cropping pattern, the environmental effects of the agricultural sector on water resources could be reduced, so that the implementation of this pattern in the region reduced virtual water by 26%, blue water footprint by 4%, gray water footprint by 18% compared to the current cropping pattern.Conclusion: According to the findings of this study, it is necessary to pay attention to the environmental objectives affecting water resources in optimizing cropping pattern. Using the proposed model, in addition to selecting the appropriate model and optimal use of water and land resources, to increase profits and reduce water and virtual water footprint, about 13 million cubic meters of water could be saved compared to the current cropping pattern in the region. Therefore, by implementing the optimal cropping pattern, in addition to reducing the environmental effects, the net income could be maximized of water consumed per cubic meter in the region, and by reducing water consumption, we can help achieve sustainable consumption of limited water resources in the region.