چالش های مدیریت منابع آبی و حفظ اکوسیستم درحوضه دریاچه ارومیه (مقاله علمی وزارت علوم)
درجه علمی: نشریه علمی (وزارت علوم)
آرشیو
چکیده
دریاچه ارومیه، بزرگترین دریاچه داخلی ایران، در سال های اخیر به علت کاهش چشمگیر سطح آب دریاچه در نتیجه تغییرات اقلیمی، فعالیت های انسانی و احداث سدهای متعدد در حوضه آبریز آن با بحران خشکی روبرو شده است. این تحقیق به منظور شناسایی علل خشک شدن دریاچه ارومیه، از داده های ماهواره ای استفاده کرده و به تحلیل عوامل انسانی و طبیعی تأثیرگذار بر کاهش سطح آب دریاچه می پردازد. تغییرات اکوسیستم و مساحت دریاچه با بهره گیری از تصاویر سنتینل (2017 و 2023) و روش NDVI مورد بررسی قرار گرفته است. بر اساس تجزیه و تحلیل داده ها مشخص شده است که اراضی ساخت وساز که در سال 2017 حدود 09/133796 هکتار بوده، در پایان دوره به 40/188779 هکتار، اراضی باغی از 88/5696 هکتار در سال 2017 به 38/6744 هکتار در سال 2023 و اراضی زراعی نیز از 07/979333 هکتار در سال 2017 به 62/1380279 هکتار در سال 2023 افزایش یافته است. همچنین میزان آب از 55/134726 هکتار در سال 2017 به 57/49401 هکتار در سال 2023 کاهش یافته است. همچنین نقشه های NDVI حوضه دریاچه ارومیه در بازه زمانی 2017 تا 2023 بیانگر این است، مقدار عددی این شاخص در سال 2017 بین 810/0 تا 018/0 و برای سال 2023 مقدار عددی بین 834/0 تا 112/0- را نشان می دهد که به علت افزایش اراضی باغی و زراعی، حجم وسیعی از آب حوضه ارومیه خشک شده است. از سوی دیگر در اطراف حوضه دریاچه ارومیه به دلیل بهره برداری از 39 سد، آب ورودی دریاچه به شدت کاهش یافته است.. نتایج نشان می دهد خشک شدن و کاهش سلامت اکوسیستم حوضه دریاچه ارومیه ناشی از سه عامل اصلی زیر است: توسعه ناپایدار بخش کشاورزی، ساخت سدهای متعدد در اطراف دریاچه برای بهره برداری از آب حوضه و تشدید تغییرات اقلیمی به همراه وقوع خشکسالی، که از جمله عوامل دیگر به شمار می روند.The challenges of water resource management and ecosystem preservation in the Urmia Lake basin
Extended Abstract Introduction Lake Urmia is one of the largest saltwater lakes in the world, located in the northwest of Iran, and is recognized as a sensitive and unique ecosystem. Unfortunately, this lake has faced serious environmental crises in recent decades. One of the main challenges is the significant decrease in the water level of the lake due to climate change, human activities, and the construction of numerous dams in its watershed. According to recent reports, the water level of Lake Urmia has significantly decreased since the mid-1990s, leading to very adverse effects on biodiversity and marine life. This crisis, in addition to threatening the environment, has also had profound economic and social impacts on local communities. In this context, the main objective of this research is to examine the role of NDVI and analyze its relationship with the health of the Lake Urmia basin ecosystem. By utilizing satellite data, we aim to record changes in NDVI over time and assess its effects on ecosystem health. With the help of this data, it will be possible to identify areas under pressure and formulate policies for the proper management of water resources and the protection of related ecosystems. Methodology The importance of assessing ecosystem health, especially in areas with specific environmental conditions, has become one of the key topics in environmental sciences today. In this study, Sentinel satellite images were obtained from the Copernicus Open Access Hub platform. The selected dates included various time periods from 2017 to 2023 to examine changes in land use and vegetation cover over time. Sentinel images were downloaded in different bands, including red (B4), green (B3), blue (B2), and near-infrared (NIR; B8). These bands were essential for calculating NDVI and analysing land use. To ensure high data quality, pre-processing steps included atmospheric corrections and cloud removal. QGIS software and the ENVI remote sensing tool were used for atmospheric corrections and cloud removal. Additionally, geometric corrections were performed in later stages to align the images. One of the effective tools in this regard is the use of the Normalized Difference Vegetation Index (NDVI). NDVI, as a remote sensing index, has significant capabilities in assessing and monitoring vegetation conditions. Results and Discussion Through necessary investigations and analyses of land use change maps, it was found that the area of construction land, which was approximately 133,796 hectares in 2017, increased to 188,779 hectares by the end of the period. Additionally, the area of orchards rose from 5,696 hectares in 2017 to 6,744 hectares in 2023. The agricultural land also increased from 979,333 hectares in 2017 to 1,380,279 hectares in 2023. Furthermore, the area of water bodies decreased from 134,726 hectares in 2017 to 49,401 hectares in 2023. The increase in agricultural land in the Urmia Lake basin is one of the most significant changes that has occurred in recent decades and has had multiple impacts on the region's ecosystem. Various factors such as population growth, rising demand for food products, and the desire for diversity in crop cultivation have led agriculture to become one of the main activities of the local population. This change has directly affected water resources, soil quality, and biodiversity in the basin. Conclusion The conducted studies indicate that the increase in vegetation cover and the construction of dams in the watershed of this lake are among the effective factors in this trend. The first point to consider is the direct relationship between vegetation cover and ater absorption. The increase in vegetation cover, especially in the watershed of the lake, helps in moisture retention in the soil and reduces evaporation. Although this issue can help conserve water resources in the short term, in the long run, the increased vegetation will require more water, and local factors may seek to allocate more water for this purpose. Secondly, the construction of dams for managing water resources and storing water during critical times also affects the natural flow of water to the lake. These dams can be significant in optimizing water consumption, but at the same time, they create natural barriers in the river's path and disrupt the water flow to the lake. As a result, with the reduction of water entering the lake, the water level gradually decreases.
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