بررسي رابطه تغييرات سطح تالاب شادگان و EC آب تالاب در طي زمان با استفاده از تصاوير ماهواره‌اي و روش‌هاي زمين‌آماري
محورهای موضوعی : مدیریت منابع آب
بهمن یارقلی
1
(استاديار، مؤسسه تحقيقات فني و مهندسي کشاورزي، سازمان تحقيقات آموزش و ترويج کشاورزي، کرج، البرز، ايران.)
یاسمن سمائی
2
(فارغ التحصيل کارشناسي ارشد، گروه علوم و مهندسي آب، دانشگاه بين‌المللي امام خميني (ره)، قزوين، ايران.)
کلید واژه: تصاوير ماهواره اي, تالاب شادگان, شوري, وسعت آب, روش‌هاي زمين‌آماري,
چکیده مقاله :
مقدمه و هدف پژوهش: تالاب‌ها به‌واسطه‌ي برخورداري از کارکردهاي مثبت محيط‌زيستي و ارائه خدمات مستقيم و غيرمستقيم به جوامع بشري و نيز به‌عنوان يک دارايي، بسيار حائز اهميت هستند. اين امر باعث شده در جوامع مختلف توجه فزاينده‌اي براي احيا و نگهداري آنها صورت گيرد. تالاب شادگان تالابي است با آب شيرين –شور و لبشور و سالانه حدود 900 ميليون مترمکعب از منابع آبي جراحي وارد شادگان مي‌شود. متأسفانه اين تالاب به‌واسطه فعاليت‌هاي توسعه‌اي پيرامون آن، افزايش ورود آلاينده‌ها و کاهش جريان‌هاي شيرين ورودي، با تهديد جدي روبرو است. برداشت‌هاي بي‌رويه از منابع آب تالاب و تخليه زباله‌هاي شهري درون محدوده‌ي آن در کنار تکه‌تکه کردن تالاب به‌واسطه احداث جاده‌ها، ايجاد ايستگاه‌هاي تقويت فشار برق، گاز و لوله‌گذاري نفت و نيز ايجاد صنايعي چون نوپانسازي، الکل‌سازي و کشت و صنعت نيشکر که پساب خود را درون تالاب تخليه مي‌کنند، همه و همه در نابودي اين تالاب نقش داشته و دارند. ارزش اقتصادي تالاب‌ها از يک‌سو و تنظيم آب و هوا، جلوگيري از سيل، حفاظت از تنوع گياهي و جانوري، زيبايي و جاذبه‌هاي بصري ذاتي تالاب، جاذبه‌هاي توريستي و ايجاد فضايي براي زندگي پرندگان مهاجر و مکاني غني براي بررسي‌هاي تحقيقاتي و علمي از سوي ديگر از مهم‌ترين موضوعات موردتوجه در يك تالاب است. توسعه طرح‌هاي منابع آب و تنظيم جريان رودخانه‌ها اغلب به‌عنوان جدي‌ترين تهديد براي پايداري اکولوِژيکي رودخانه و تالاب‌ها شناخته‌شده است. مواد و روش‌ها: با توجه به اهميت تالاب شادگان از جهات مختلف، در اين پژوهش با استفاده از شاخص هدايت الکتريکي، روند تغييرات شوري آب در سطح اين تالاب را در پنج دهه اخير پهنه‌بندي و تحليل شد و در نهايت رابطه ميان مساحت و شوري آب در سطح اين تالاب مهم به دست آمد. همچنين با استفاده از داده‌هاي هدايت الکتريکي 23 ايستگاه موجود در سطح تالاب و با کمک تصاوير ماهواره‌اي و تکنيک‌هاي سنجش از دور و روش درون‌يابي IDW به بررسي تغييرات اين شاخص در مدت ذکرشده پرداخته شد که منجر به يک رابطه رياضي شد. نتايج و بحث: بر اساس نتايج تحقيق، فعاليت‌هاي انساني بالادست، به‌ويژه سدسازي و طرح‌هاي توسعه کشاورزي، تأثير زيادي بر کميت و کيفيت تالاب داشته است. با تغييرات اقليمي و خشکسالي، اين اثرات تشديد شده و منجر به کاهش سطح تالاب و همچنين افزايش شوري آب تالاب شده است. اين تغييرات را مي‌توان هم از نظر ابعاد زماني و هم از نظر مکاني مشاهده کرد. متعاقباً، نتايج بيانگر روند افزايش شوري از بخش هاي جنوبي به سمت شمال و همچنين نمود بيشتر افزايش شوري در قسمت هاي جنوبي در اثر کاهش جريان آب شيرين ورودي ( تابيش از دو برابر) نيز مي‌باشد. بر اساس نتايج، سه سطح شوري در تالاب وجود دارد: شور، لبشور و فوق شوري و افزايش شوري در هر سه پهنه مشاهده مي‌شود. نتايج و معادلات حاضر بعنوان يک دستاورد مورد استفاده مديران آب و محيط زيست بوده و آنها مي‌توانند با اندازه‌گيري وسعت تالاب با استفاده از فناوري هاي مختلف، EC آب در ايستگاه‌هاي کليدي و شاخص و در نهايت در سطح تالاب را تخمين بزنند. و يا برعکس با مشخص بودن EC، وسعت تالاب را برآورد کنند. بنابراين با گذشت زمان، سطوح و مناطق شور و فوق شوري گسترش يافته و سطح آب شور کاهش يافته است. انتظار مي‌رود که اين روند در طول زمان ادامه يابد و در نتيجه آب نمک دريا به سمت تالاب پيش برود و ميزان شوري در آن افزايش يابد. نتيجه‌گيري: بر اساس اين مطالعه، با توجه به رابطه بين شوري و سطح تالاب و همچنين مساحت آبي تالاب، مي‌توان شوري آن را در سه پهنه تخمين زد. با اندازه‌گيري شوري آب در چندين ايستگاه کليدي در هر يک از سه منطقه، مي‌توان سطح آب تالاب را تخمين زد. در پايش، مديريت و حفاظت کيفي تالاب و در نتيجه گونه هاي آن، اين معادله و روابط آن مي‌توانند نقش مهمي ايفا کند.
Introduction: Wetlands are highly beneficial to human societies due to their positive environmental functions, direct and indirect functions, as well as their value as an asset. It has led to an increase in the attention given to their restoration and maintenance in different societies. Shadgan Wetland contains fresh-salty, and brackish water, and approximately 900 million cubic meters of Jarahi water resources enter Shadgean every year. The wetland is at risk of serious harm as a result of the developmental activities occurring around it, which are causing pollutants to enter the wetland and reducing the quantity of fresh water coming in. A number of factors contribute to the destruction of this wetland, including over-exploitation from its water resources, the discharge of urban waste within its limits, the fragmentation of the wetland as a result of road construction, the construction of stations to increase the pressure on electricity, gas and oil pipelines, as well as effluents from industries such as bread making, alcohol production, sugarcane cultivation and industry. The economic value of wetlands and climate regulation, flood prevention, protection of plant and animal diversity, beauty and inherent visual attractions of wetlands, tourist attractions, as well as creating an opportunity for migratory birds to nest and a place for scientific research are among the most important considerations in the design of a wetlands. The development of water resources schemes and the regulation of river flows are often recognized as the most serious threats to the ecological sustainability of rivers and wetlands. Method: This study attempts to determine the change in water salinity of Shadegan wetland in the last five decades using the electrical conductivity index due to the importance of Shadegan wetland in various ways. Finally, a relationship has been established between the area and the salinity of this significant wetland. Also, by using electrical conductivity data from 23 stations in the lagoon and with the help of satellite images and remote sensing techniques and interpolation methods (IDW), the changes of this index in the mentioned period were investigated, leading to a mathematical relationship. Results and Discussion: According to the research results, upstream human activities, especially dam constructions and agricultural development projects, have had a great impact on the quantity and quality of the wetland. With climate change and drought, these effects have intensified, resulting in a reduction of the wetland level as well as an increase in the salinity of the wetland water. These changes can be observed both in terms of their temporal and spatial dimensions. Consequently, the results show the trend of increasing salinity from the southern parts to the north and also the greater manifestation of the increase in salinity in the southern parts due to the decrease in the incoming fresh water flow (more than twice). According to the results, there are three salinity levels in the wetland: saline, brackish water, and super salinity, and a salinity increase is observed in all three zones The present results and equations are used as an achievement by water and environment managers and they can estimate the EC of water in key and indicator stations and finally at the level of the wetland by measuring the size of the wetland using different technologies. So over time, the levels and zones of saline and super salinity have expanded, and the levels of brackish water have decreased. It is expected that this process will continue over time, resulting in the sea salt water advancing towards the wetland and increasing the amount of salinity within it. Conclusions: According to this study, based on the relationship between salinity and the level of the wetland, as well as the water area of the wetland, it is possible to estimate its salinity in three zones. By measuring the salinity of water at several key stations within each of the three zones, the wetland's water level can be estimated. In monitoring, managing, and qualitatively protecting the wetland and consequently its species, this equation and its relationships can play an important role.
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