تحلیل صحرایی عملکرد لایه‌های ژئوممبران در کاهش نشت آب از کانال‌های شبکه آبیاری مغان

کنترل تلفات نشت از کانال‌ها و مخازن ذخیره آب به منظور حفاظت از منابع محدود آب کشور ضروری است. برای کنترل نشت، تاکنون روش‌های متعددی به کار گرفته شده است و امروزه استفاده از پوشش‌های ژئوسنتتیک، مانند ورقه‌های ژئوممبران، مورد توجه قرار گرفته است. در این تحقیق، مشکلات موجود در مراحل مختلف طراحی و اجرای پوشش ژئوممبران در کانال‌ها در شبکه آبیاری مغان بررسی شده است. میزان نشت از این نوع پوشش در شرایط مختلف با استفاده از روش ورودی-خروجی بررسی گردید. در تحقیق حاضر، از بین کانال های اجرا شده با پوشش‌های ژئوسنتتیک در شبکۀ آبیاری مغان، کانال پمپاژ 3 مغان با توجه به اهمیت و ویژگی‌های فنی انتخاب و روی آن از نظر ویژگی های هیدرولیکی، کنترل نشت، کارایی و مسائل اجرایی بررسی صحرایی گردید. بر اساس نتایج آزمایش ها، میزان متوسط نشت آب در طول بازه کانال‌ 46/86 لیتر در روز در مترمربع به دست آمد و بر اساس بازدیدهای صحرایی، رسوب و تخریب در کانال مشاهده نشد. این میزان نشت، در مقایسه با دیگر پوشش‌های ژئوسنتتیک مطالعه شده در دیگر نقاط  برای کانال های پوشش شده با پلی اتیلن کم چگالی به ضخامت 2/5 میلی متر (14 تا 69  لیتر در روز در هر مترمربع)، در حد متوسط قرار دارد.

field evaluating the efficacy of geomembrane cover in mitigating water seepage in moghan irrigation network channels

extended abstractintroductionthe performance of geomembrane liners depends on proper design, installation, and maintenance. geomembranes exhibit thermoplastic behavior, expanding and contracting significantly with temperature changes. this can lead to issues like wrinkling and uplift, which can compromise the liner’s seepage control function. proper maintenance is also essential, as geomembranes are sensitive to mechanical damage that can greatly reduce their effectiveness.in iran, geomembrane lining of irrigation canals has been implemented in several projects, including the moghan irrigation network. however, comprehensive studies on the performance and durability of these liners are lacking. this study aimed to evaluate the effectiveness of geomembrane liners in controlling seepage from pumping channel no. 3 of moghan, and identify any issues related to their design, installation and operation. the results can help guide the rational expansion and optimal utilization of geomembrane lining for improving agricultural water productivity in iran.literature reviewgeomembranes exhibit thermoplastic behavior, expanding and contracting significantly with temperature changes. geomembranes layers have a high coefficient of thermal expansion, causing wrinkling or waves in parts of the liner when heated. proper temperature is critical for seam welding to avoid inadequate bonding and uplift of the geomembrane on slopes. long-term wrinkles can also become failure points. proper maintenance is essential for the sustainable operation of geomembrane projects, especially for exposed liners. preventing mechanical damage (intentional and accidental) is crucial for the liner’s durability and effectiveness. geomembranes are sensitive to intentional damage (cutting, burning, abrasion, impact, etc.) which can greatly reduce the liner’s seepage control capacity.methodologythe moghan irrigation network, particularly pumping channel no. 3, has been a focal point for evaluating hydraulic performance, seepage control, and durability in irrigation systems. this channel, which spans 28 kilometers, is crucial for drawing water from the irrigation network and has a capacity of 2.3 cubic meters per second, serving approximately 3,500 hectares of agricultural and industrial land. research conducted on this channel has employed the inflow-outflow method to measure average seepage rates, which were found to be around 46.86 liters per day per square meter. this rate is considered moderate compared to other geosynthetic-lined channels, highlighting the need for ongoing maintenance and monitoring to manage water loss effectively.field inspections have revealed significant deterioration in the channel’s walls and floor, leading to operational challenges. in 1999, significant repairs were made to three critical sections of the canal, covering 8 kilometers in total. however, these repairs proved insufficient, as severe damage reoccurred within two years of service. this situation emphasizes the necessity for robust construction practices and the potential benefits of using advanced materials, such as geomembranes, to enhance the durability and performance of irrigation channels. the research indicates that while immediate repairs can address some issues, long-term solutions are essential for maintaining the integrity of the irrigation infrastructure.overall, the evaluation of pumping channel no. 3 illustrates the complexities and challenges faced in managing irrigation systems, particularly regarding hydraulic efficiency and seepage control. the findings suggest that integrating geosynthetic materials could significantly improve the channel’s performance and longevity, thereby optimizing water resource management in the moghan region. continuous assessment and adaptation of maintenance strategies will be crucial in ensuring that the irrigation network meets the agricultural demands of the area effectively.results and discussionthe average seepage rate along the canal reaches was 0.4686 liters per square meter per day. no sedimentation or damage was observed during field inspections. the results demonstrate the acceptable short-term effectiveness of well-installed geomembrane liners in controlling water losses. properly designed and maintained geomembrane liners can significantly reduce seepage, improving agricultural water productivity. however, geomembranes require careful consideration in design, construction and operation to avoid issues like thermal wrinkling and mechanical damage that can compromise their seepage control function.conclusioncontrolling seepage from water storage and conveyance systems is essential in water-scarce countries like iran. geosynthetic liners, especially geomembranes, are rapidly expanding in iran due to their unique waterproofing capabilities and other advantages like quick and easy installation. however, comprehensive studies on the performance of these liners are lacking. rational expansion, proper utilization and optimal investment requires comprehensive evaluation of completed projects. this study’s results indicate the acceptable short-term effectiveness of well-installed geomembrane liners in controlling water losses. therefore, geomembrane liners can contribute to improving agricultural water productivity by significantly reducing seepage, if they meet waterproofing requirements. however, long-term performance and durability require further investigation.