بررسی رفتار هیدرولوژیکی و روندهای احتمالی جریان حوضه کنگیر تحت تاثیر تغییرکاربری اراضی با استفاده از swat

حوضه آبخیز کنگیر یکی از مهم ترین حوضه های آبخیز ایران از نظر مدیریت منابع آب می باشد. تغییرات کاربری و پوشش زمین (lulc) در این حوضه از اهمیت استراتژیک زیادی برخوردار است چرا که به عنوان یکی از مهم ترین منبع تامین آب استان ایلام بوده است. در تحقیق حاضر، با استفاده از تصاویر ماهواره ای لندست و روش طبقه بندی در پلتفرم گوگل ارث انجین تغییرات کاربری اراضی حوضه در سال های1990،2000،2010،2020 استخراج و تاثیر آن بر تغییرات هیدرولوژی محلی بررسی شد. مطالعه حاضر بر روی حوضه آبخیز کنگیر با هدف انجام تشخیص موثر جریان و ارزیابی اثرات تغییرات lulc در 30 سال گذشته بر روی آب انجام گرفت. مدل ابزار ارزیابی خاک و آب (swat) نشان داد که نتایج شبیه‌سازی شده با داده‌های اندازه‌گیری شده در باز تولید دینامیکی فصلی جریان مطابقت دارد. همچنین مشاهده شد که زیرحوضه هایی که در آنها مرتع غالب است، بیشتر مستعد افزایش رواناب هستند. در زیرحوضه هایی که پوشش اراضی آنها عمدتاً جنگلی است، سری زمانی همگن و بدون روند است. مطالعه حاضر تاثیرات 30 سال تغییرات lulc در حوضه کنگیر را بر رواناب نشان داد که به نوبه خود می تواند نقش مهمی در تغییر چرخه هیدرولوژیکی داشته و در نتیجه این تغییرات می تواند بر فعالیت های انسانی متنوع در منطقه مانند کشاورزی، دامداری، تولید انرژی، امنیت غذایی و تامین آب تاثیر بگذارد. بنابراین، مدل swat تخمین‌گر خوبی برای فرآیندهای شبیه سازی جریان در حوضه‌های کنگیر است و می‌تواند توسط تصمیم‌گیرندگان در مدیریت منابع آب و زیست‌محیطی استفاده شود. 

investigating the hydrological behavior and possible flow trends of the kangir basin under the influence of land use change using the swat model

1- introductionthe swift growth of the population, coupled with the pressing need for economic advancement, has led to an increased demand for various uses within watersheds. land use plays a crucial role in the study of natural resources and the management of environmental systems. it is vital to comprehend the interplay between runoff and alterations in land use, particularly in the context of water resource management and land use planning. a thorough understanding of historical, current, and anticipated changes in land use and land cover is imperative for effective watershed management. this study aims to explore the effects of land use changes on the potential for surface runoff generation in the kangir watershed, employing remote sensing, geographic information systems, and the swat model. the kangir watershed spans an area of 122.71 square kilometers and is situated in the southeastern part of avan gharb, adjacent to the northern region of ilam province. the kangir river, which is the sole permanent river in this basin, originates from sarab avan, located 9 kilometers southeast of avan city, and flows in a south-to-northwest direction.2-metodologythe soil and water analysis tool (swat) was employed to conduct a hydrological simulation of the kangir basin. essential data for the model included soil characteristics, climatic conditions, a topographic map, and a land use map, all of which are crucial for simulating the physical processes associated with flow quantity and velocity. to estimate surface runoff, hydrological response units (hrus) were utilized. the calibration of the swat model results was performed using swat cup software in conjunction with the sufi2 algorithm, which facilitated the identification of key parameters influencing flow dynamics. additionally, land use classifications for the years 1990, 2000, 2010, and 2020 were executed on the google earth engine platform, resulting in the identification of nine distinct land use categories, including irrigated agricultural land, dense forest, semi-dense forest, orchard, pasture, urban areas, shrubland, rocky terrain, and grassland.3- results the integration of land use, soil, and slope class maps into the arc swat software facilitated the development of hydrological response units for the basin through the overlay of these maps. calibration of the model was performed using observed flow discharge data from the kangir and ivan hydrometric stations spanning from 1994 to 2013, employing the swat-cup software alongside the sufi2 algorithm. the subsequent period from 2014 to 2018 served as the validation phase for the model. the outcomes of the calibration and validation processes for both the ivan and kangir stations demonstrate the model’s robust performance within the swat-cup framework. initially, the land use map for the relevant time periods was derived from satellite imagery accessed through the google earth engine system. an analysis of the various land uses in the kangir basin over the years reveals significant alterations compared to 1990, with notable changes observed in human and natural land use when assessed in 10-year intervals. consequently, modeling efforts were directed towards examining flow behavior and the influence of vegetation on runoff, utilizing the swat model based on the land use map from the year 2000.4- discussion & conclusionsthe examination of land use alterations within the kangir basin reveals a notable correlation between these modifications and shifts in runoff behavior. over the last three decades, the basin has undergone considerable changes in land use, marked by a reduction in both dense and semi-dense forests, as well as pastures and wastelands, while urban development, agricultural areas, and pastures have seen significant growth. this transformation is particularly striking when contrasting data from 1990 with that from 2020, underscoring a pattern in which natural vegetation is increasingly supplanted by anthropogenic land uses. the consequences of these land use transformations on hydrological processes are substantial, as this research indicates a clear decline in vegetation density correlating with heightened runoff intensity, particularly evident in the years 2010 and 2020.the findings from the modeling suggest that the most significant rate of land use transformation is associated with a reduction in dense forests, semi-dense forests, orchards, and grasslands, alongside an increase in agricultural land and urban areas. in the simulations performed at the kangir station, the swat model predicted peak runoff levels that exceeded the recorded observations, a discrepancy that can be linked to the ongoing changes in land use. if these trends in land use persist, there will be a notable rise in peak discharge levels, leading to severe flooding events that pose substantial threats to both the economic stability and the livelihoods of the residents within the basin.