Environmental Erosion Research

fa تحلیل روند و رابطه تغییرات دبی با بارش و بار رسوب رودخانه‌ای (مورد مطالعه: ایستگاه‌های منتخب حوضه‌های اصلی ایران) Trend Analysis and the Relationship Between Flow Variability, Precipitation, and River Sediment Load (Case Study: Selected Stations of Iran's Main Basins) مدلسازی و تحلیل زمانی و مکانی رخداد انواع مختلف فرسایش محیطی مستخرج از پایان‌نامه / رساله / طرح پژوهشی در این پژوهش، روند تغییرات دبی، بارش و رسوب سالانه طی یک دوره ۳۰ ساله (۱۴۰۲–۱۳۷۳) در حوضه‌های آبخیز زرینه‌رود، قره‌سو، کشف‌رود و دز با بهره‌گیری از آزمون ناپارامتری من-کندال، تخمین‌گر شیب سن و رگرسیون مورد بررسی قرار گرفت. علاوه بر این روش‌ها، به منظور تحلیل دقیق‌تر نوسانات زمانی و فرکانسی متغیرهای بارش، دبی و رسوب، از تبدیل موجک پیوسته نیز استفاده شد تا تغییرات زمانی طیف فرکانسی  نیز  بررسی شود. نتایج نشان داد که بین دبی و رسوب، بدون تأخیر زمانی، همبستگی معنی‌داری در سطح ۰۱/۰ وجود دارد و ضریب همبستگی بین ۶۸/۰ تا ۹۶/۰ متغیر است؛ به‌طوری که کمترین و بیشترین میزان همبستگی به ترتیب مربوط به زرینه‌رود و کشف‌رود است. نتایج تحلیل تأخیر زمانی نیز نشان داد که به جز رودخانه دز (با بیشترین همبستگی بین دبی و بارش دو روز قبل)، در سایر رودخانه‌های مورد بررسی، بیشترین همبستگی بین دبی و بارش یک روز قبل مشاهده شده است و در هر دو تأخیر زمانی، نتایج در سطح ۰۱/۰ معنی‌دار هستند. نتایج تحلیل روند نیز حاکی از کاهش بارش و دبی در اغلب ایستگاه‌ها طی دوره آماری بوده است، به‌جز ایستگاه آق‌دربند در کشف‌رود. این کاهش در ایستگاه‌های زرینه‌رود و سد دز با آماره من-کندال برابر با ۳/۲- و ۲- در سطح ۵ درصد معنی‌دار گزارش شد. روند رسوب نیز در بیشتر حوضه‌ها کاهشی بوده و این روند در ایستگاه‌های سامیان (قره‌سو) با مقدار ۱/۳- و تله‌زنگ (دز) با مقدار ۴/۳- در سطح ۱ درصد و در ایستگاه‌های زرینه‌رود و سد دز در سطح ۵ درصد معنادار تشخیص داده شد. تحلیل گرافیکی آزمون من-کندال نیز نشان‌دهنده دو نقطه شکست مهم در سال‌های ۱۳۷۷ و ۱۳۸۶ بود که بیانگر کاهش چشمگیر دبی و رسوب در ادامه دوره آماری است. نتایج تحلیل موجک نیز نشان داد که در اغلب ایستگاه‌ها، الگوی سالانه در بارش و دبی به‌عنوان مؤلفه غالب مشاهده می‌شود. همچنین در برخی ایستگاه‌ها نوسانات میان‌مدت با دوره‌های ۲۴ تا ۳۶ ماهه نیز شناسایی شد که می‌تواند با پدیده‌های اقلیمی مرتبط باشد. رفتار رسوب نسبت به دبی و بارش ناپیوسته‌تر و بیشتر وابسته به رخدادهای حدی بود، به‌طوری‌که در برخی حوضه‌ها مانند دز و قره‌سو، افزایش ناگهانی توان موجک در مقیاس‌های کوتاه‌مدت مشاهده شد. نتایج حاصل اهمیت تحلیل موجک به‌عنوان ابزاری مکمل در کنار روش‌های آماری سنتی را برجسته می‌سازد، چرا که این روش امکان بررسی دقیق‌تر و چندمقیاسی پویایی زمانی متغیرهای هیدرولوژیکی را فراهم می‌سازد.   1- Introduction Changes in precipitation, discharge, and sediment load in rivers and water resources are crucial parameters in water resource management studies. This study analyzes the trends of discharge, precipitation, and sediment in the watershed areas of Zarrineh River, Qareh Sou, Kashaf Rud, and Dez over a 30-year period (2023-1994) using the non-parametric Mann-Kendall test and Pearson correlation method. The findings indicate a significant correlation between discharge and sediment without any delay, with correlation coefficients ranging from 0.68 to 0.96. Additionally, a significant correlation between discharge and precipitation is observed only in the Dez and Qareh Sou rivers, with a stronger connection to precipitation from one day prior. The trend analysis of precipitation and discharge across various stations indicates an overall decline in these parameters, except for the Aghdarband station in the Kashaf Rud basin. The highest decreasing Sen's slope for precipitation is noted at the Dez dam station, while significant reductions in discharge are seen at the Samian and Arbab Kandi stations. In other stations, changes appear as short-term fluctuations. An assessment of sediment trends reveals a decrease in sediment levels across most watersheds, excluding the Kashaf Rud basin. These changes are also found to be significant in various stations. Moreover, the Mann-Kendall graphical test indicates a break point and a shift in 1998 and again in 2007, which results in a notable decrease in discharge and sediment in the studied watersheds. 2-Methodology The study area of this research includes four important watersheds in the country: Qara Su, Zarineh Rud, Dez, and Kashaf Rud. The Qara Su watershed, which is part of the Aras sub-basin, features the longest and most water-rich internal river of Ardabil province, named Qara Su. This river originates from the Talesh highlands. The Zarineh Rud watershed is located in the south and southeast of Lake Urmia and is recognized as the largest sub-basin of Lake Urmia. This watershed contains a river of the same name, which flows through the provinces of Kurdistan and West Azerbaijan and, at 302 kilometers long, is one of the longest and most water-rich rivers in the region. In this research, precipitation, flow, and sediment data were collected from the selected stations, and the trends of these time series data were analyzed using the non-parametric Mann-Kendall test and the Sen's slope estimator. Additionally, to identify points of change and trend breaks, the Mann-Kendall graphical method was employed, and Pearson correlation tests were conducted to examine the relationships between flow, precipitation, and sediment. The Mann-Kendall test is based on the ranks of data in time series and is used to assess trends in hydrological and meteorological data. The slope estimation of the trend line using the Sen method is employed as a non-parametric technique that calculates the median slope by analyzing the differences between observations in a time series. In this method, a slope is calculated for each pair of consecutive data points, and their median represents the slope of the trend line. Moreover, the correlation coefficient serves as a criterion to determine the degree of association between variables and to identify the type, direction, and extent of their linear correlations 3- Results This study analyzed the trends of annual discharge, precipitation, and sediment load over a 30-year period (1994–2023) in four watersheds: Zarrineh River, Qareh Su, Kashaf  rud River, and Dez. Using non-parametric methods like the Mann-Kendall test, Sen’s slope estimator, and regression line slope, the researchers found a significant correlation (p < 0.01) between discharge and sediment load across all basins, with correlation coefficients ranging from 0.68 to 0.96. Discharge and precipitation showed lower correlation coefficients between 0.32 and 0.55, with only the Dez and Qareh Su rivers demonstrating significant correlations. Lagged analysis indicated that discharge correlated most strongly with precipitation from the previous day, except for the Dez River, which correlated with precipitation from two days earlier. Trend analysis found that precipitation and discharge were declining across most of the study period, particularly at Zarrineh River and Dez dam stations, where significant changes were noted (Mann-Kendall statistics of -2.3 and -2.0, respectively). The highest decline in precipitation was observed at Dez dam station with a Sen’s slope of -5.8. In Qareh Su, significant declines in discharge were identified at Samian and Arbab Kandi stations, while some stations exhibited only minor fluctuations. Sediment load trends showed a universal decline across the studied basins, except for the Kashaf rud  River. Notable reductions were observed at Samian station in Qareh Su and Taleh Zang station in Dez, both significant at the 1% level. The Mann-Kendall test indicated breakpoints in 1998 and 2007, signaling sustained reductions in discharge and sediment load across most basins throughout the period of study. 4. Discussion & Conclusions This study investigates and analyzes the relationship and trends of precipitation, discharge, and sediment in the Zarrineh River, Qareh Su, Dez, and Kashf rud River. The amounts of discharge and sediment also follow the trends of precipitation; except for the Agh-Darband station in the Kashf rud River, in other stations, they show a decreasing and negative trend. This decreasing trend has become significant in the three rivers of Qareh Su, Zarrineh River, and Dez. The highest slope of change in discharge and sediment, similar to the precipitation variable, is related to the dam station. In the watersheds of East Azerbaijan, it corresponds to a significant decrease in discharge and sediment. The examination of the points of rupture and break in the changes also revealed that the changes are reducing in the studied variables. This decreasing trend has continued until the end of the studied statistical period. The analysis of the relationship between discharge, sedimentation, and precipitation also showed that there is no strong and significant correlation between discharge and either precipitation or sediment in any of the rivers studied. Therefore, despite a direct relationship, one should not always infer an increase or decrease in sedimentation to be directly related to an increase or decrease in precipitation and discharge. In conclusion, based on the results obtained from the analysis of the annual trends of precipitation, discharge, and sediment in the four rivers studied in different watersheds, it was determined that in most of the examined areas, the mentioned variables demonstrated a decreasing trend. Based on the slope estimator, the annual changes in discharge and sediment are more severe and more pronounced than those in precipitation in the region. The results of this study indicate that if attention is not paid to climatic and hydrological changes.   تحلیل موجک, شیب سن, روند, من-کندال Precipitation, Sen’s Slope, Sediment, Trend, Discharge, Mann-Kendall 1 21 http://magazine.hormozgan.ac.ir/browse.php?a_code=A-10-39-3&slc_lang=fa&sid=1 Fatemeh Modares فاطمه مدرس fateme.modarss@modares.ac.ir 100319475328460010106 100319475328460010106 No Physical Geography, Faculty of Humanities, University of Tarbiat Modares, Tehran گروه جغرافیای طبیعی، دانشکده علوم انسانی، دانشگاه تربیت مدرس، تهران Manuchehr Farajzadeh منوچهر فرج زاده farajzam@modares.ac.ir 100319475328460010107 100319475328460010107 Yes Physical Geography, Faculty of Humanities, University of Tarbiat Modares, Tehran گروه جغرافیای طبیعی، دانشکده علوم انسانی، دانشگاه تربیت مدرس، تهران Majid Shah Hossini مجید شاه حسینی m.shahhosseini@modares.ac.ir 100319475328460010108 100319475328460010108 No Physical Geography, Faculty of Humanities, University of Tarbiat Modares, Tehran گروه جغرافیای طبیعی، دانشکده علوم انسانی، دانشگاه تربیت مدرس، تهران