سنجش ارتباط بین نوسانات آب زیرزمینی و مساحت پهنه‌های آبی (مطالعۀ موردی: تالاب ارژن فارس)

بررسی نوسان‌های سطح آب دریاچه‌ها به‌منظور حفاظت آن‌ها به‌لحاظ اهمیت، ماهیت و موقعیت این مجموعه‌های آبی و به‌عنوان یک میراث طبیعی در سال‌های اخیر در بین کشورها در سطح ملی و منطقه‌ای جایگاه ویژه‌ای پیدا کرده است. نوسان‌های یادشده تاثیرات زیادی بر محیط پیرامون و از جمله تغییرات سطح آب زیرزمینی در حوضۀ آبخیز دریاچه‌ها داشته است. تالاب ارژن با وسعتی حدود 22 کیلومترمربع به‌عنوان یکی از دریاچه‌های آب شیرین ایران از اهمیت ویژه‌ای برخوردار است. هدف اصلی این پژوهش بررسی تغییرات سطح آب تالاب ارژن و ارتباطش با تراز آب زیرزمینی با استفاده از تصاویر ماهواره‌ای و سیستم اطلاعات جغرافیایی است؛ برای رسیدن به این هدف با استفاده از کدنویسی در سامانۀ گوگل ارث انجنین و از طریق تصاویر ماهواره‌ای چندطیفی ماهواره‌ای لندست از سال 1986 تا 2018، نوسان‌های سطح آب تالاب ارژن در دورۀ زمانی مذکور استخراج شد. بررسی‌ها نشان‌دهندۀ نوسان‌های گسترده در طول بازۀ زمانی 1986 تا 2018 است به‌طوری که از 8.22 کیلومترمربع در سال 1986 به صفر کیلومترمربع در سال 2018 رسیده است. بیشترین تغییرات به‌دلیل کاهش ارتفاع آب دریاچه به‌ویژه در جنوب‌شرق و سواحل غربی تالاب ارژن است. بر اساس نتایج به‌دست‌آمده، بیشترین مساحت تالاب در سال 1989 (14/78کیلومترمربع) بوده و از سال 2010 کاملاً خشک شده است. برای بررسی وضعیت آب‌های زیرزمینی از سری زمانی منتج از داده‌های ماهوارۀ گریس استفاده گردید که بر مبنای ضریب jpl (86% همبستگی) مشخص شد سطح آب زیرزمینی در آبخوان ارژن سیر نزولی طی کرده و حدود 20 سانتی‌متر کاهش یافته است.

assessing the relationship between alterations in groundwater level and physical changes in water bodies: a case study of arjan wetland, fars province

introduction: considering the rapid changes occurring in natural phenomena of the earth and their considerable influence on human life throughout time, it is crucially important to thoroughly examine such changes so that one can better understand the natural and human processes involved in those changes. monitoring and assessing the areas where the aforementioned changes occur are considered as important steps in national development and the management of natural resources. in this regard, remote sensing technology is uniquely applicable in collecting information concerning such phenomena, taking into account various advantages of multispectral satellite imagery, including their availability and interpretability. this study, therefore, sought to investigate the changes made in arjan wetland using rs and gis technology. to put it more precisely, the current study examined the changes that occurred in the wetland’s banks, the decline of the area covered by the wetland’s water, and the changes made in the earth’s surface temperature and groundwater level. throughout the past few decades, remote sensing technology has widely been used by scholars to detect such changes over time. on the other hand, coastal areas, especially inland lakes, have received special attention as ecological environments. materials and methods: this study used two types of data: meteorological data including precipitation, temperature (average, maximum, minimum), humidity, evaporation, and transpiration data, and remote sensing data, including the information collected from landsat and modis images to calculate water indices and surface temperature. it should be noted that modis satellite images used in this study possessed low spatial resolution and high temporal resolution. moreover, the ndwi was calculated for the study period (19682018) using coding in the google engine system. on the other hand, grace satellite imagery was used to estimate the alterations made in the groundwater level within the study area. moreover, the data regarding the observed wells within the study area were used to validate the results and zone the aquifer’s water level. to determine the optimal position of the earth’s surface and remove hydrological effects, the grace satellite (gldas model) was used.discussion and results: like other lakes, the fars province’s lakes are completely dependent on the status of water resources in the related watershed. having been dried up since 2013, arjan seasonal wetland, where the water height reaches one meter during high water periods, is currently in critical condition. in winter and spring, the surplus water is stored in the surrounding plain due to the increase in the plain’s surface inflows and the limited irrigation capacity in its eastern part, turning the wetland into a lake. in this study, first, the area of ​​arjan wetland was examined in terms of climatic parameters. while arjan wetland experienced lots of fluctuations throughout the study period (19862018), it could be argued that its main crisis started in 2010 when the area of ​​the lake was reduced to less than half, and finally became zero in 2013.