ارزیابی اثرات تغییر اقلیم بر مقادیر رسوب معلق در تعدادی از حوزه‌های آبخیز استان اردبیل

برآورد رسوب‌دهی رودخانه به‌دلیل پیچیدگی‌های آن یکی از مواردی است که مورد توجه پژوهشگران قرار گرفته است. اﺳﺘﻔﺎده از ﻣﻨﺤﻨﯽﻫﺎی ﺳﻨﺠﻪرﺳﻮب و راﺑﻄﻪ ﺗﻮاﻧﯽ ﺑﺮازش داده ﺷﺪه ﺑﯿﻦ دادهﻫﺎی دﺑﯽ و ﻏﻠﻈﺖ رﺳﻮب ﻣﻌﻠّﻖ ﯾﮑﯽ از ﻣﺘﺪاولﺗﺮﯾﻦ روشﻫﺎی ﺗﻌﯿﯿﻦ ﻣﯿﺰان ﻏﻠﻈﺖ رﺳﻮب ﻣﻌﻠّﻖ اﺳﺖ. از طرفی پدیده تغییر اقلیم با تاثیر روی بارش، درجه‌حرارت و دبی جریان تولیدی، به‌صورت غیرمستقیم کیفیت آب را نیز تحت تاثیر قرارمی‌دهد. هدف پژوهش حاضر به‌‌دست آوردن تغییرات رسوب طی دهه آینده (2030-2011) با استفاده از معادله سنجه‌رسوب می‌باشد. برای این‌منظور از مدل هیدرولوژیکی ihacres و مدل اقلیمی larswg استفاده شد. مدل ihacres ابتدا برای 7 ایستگاه هیدرومتری واسنجی و اعتبارسنجی شد سپس با به‌کارگیری مدل larswg میزان تغییرات درجه حرارت حداقل، حداکثر و بارندگی برای دوره آینده به‌دست آمد. این تغییرات به مدل ihacres اعمال شد و میزان دبی جریان دوره آتی تخمین زده شد. از طرفی با استفاده از داده‌‌های دبی و رسوب مشاهداتی منحنی‌سنجه‌رسوب تهیه شد. با تغییر مقادیر دبی جریان در ایستگاه‌های مطالعاتی مقادیر دبی رسوب معلق برای دوره آتی محاسبه شد. نتایج نشان داد مقدار بارندگی 3.68 درصد کاهش یافته و دمای حداقل 16.48 و دمای حداکثر نیز 5.39 درصد افزایش یافته است. بررسی میزان رواناب طی دهه آینده در ایستگاه‌های هیدرومتری نشان داد که دبی متوسط به‌طورکلی 0.16 درصد کاهش یافته است. تعداد وقایع دبی اوج افزایش یافته است که بیش‌ترین افزایش مربوط به ایستگاه هیدرومتری یامچی با دبی متوسط 2.09 و 16 واقعه دبی اوج بالای 6 مترمکعب برثانیه می‌باشد. این تغییرات اقلیمی به‌طور متوسط منجر به کاهش 74 درصدی بار معلق رسوب در ایستگاه‌های مطالعاتی شده است. نتایج پژوهش حاضر نشان دهنده تاثیر قابل توجه تغییر اقلیم بر حوزه‌های آبخیز استان اردبیل می‌باشد و با توجه به اثرات زیست محیطی تغییر اقلیم لازم است راهکارهایی جهت مدیریت مناسب حوزه‌های آبخیز اتخاذ شود.

assessing the effects of climate change on assessing the effects of climate change on suspended sediment values in some watersheds of ardabil provincet values in some watersheds of ardabil province

introduction estimation of the rivers sediment load has high complexity due to effecting different parameters in this aspect. regarding the power relationship between discharge data and suspended sediment load use of sediment rating curves is one of the most common methods for determining the sediment yield in ungauged watersheds. sediment condition shows the upstream characters and using of the obtained data makes a relation between erosion and sediment load. the different parameters such as climate, land use, data accuracy and the applied methods have the effect on the sediment rating curve shape. agriculture activities such as tillage in the direction of slope lead to accelerated erosion in the watersheds, especially in the mediterranean area. these decades many studies assessing the effects of climate changes in the future period and it affects on runoff. in this study, the main objective is to obtain sediment changes during the future decade (20112030) using the curve rating in sediment estimating. for this purpose, the ihacres hydrologic model and the lars_wg climate model were used. material and methode the ihacres model for seven hydrometric stations was calibrated and validated. this model is a rainfall and runoff erosion that require a little data for running including minimum and maximum temperature, rainfall, discharge and study are. this model defined as a lumped model and highly common in watersheds with scarce data. with running this model in all of the models the model parameters were calibrated. also, the lars_wg model was used for determining the weather changes that are occurring in the samian watershed. this watershed has near to 4 thousand square kilometers that have many subwatersheds. in this study, the watersheds in the west of the samian watershed were selected for modeling. the average of rainfall in this area is between 220 and 457 mm, and the weather temperature changes in this region are high and that is between 32 to 34 c°. the results of lars_wg showed the weather changes in each part of the hydrological model inputs that these changes were applied to the ihacres model and the discharge flow rate was estimated for the future. on the other hand, using the observed discharge and sediment yield were calculated the sediment curve rate. by changes in flow discharge at the study stations, were calculated the suspended sediment discharges for the future period. results and discussion the results of the lars_wg model showed that the amount of precipitation decreased to 3.68 percent and the minimum and the maximum temperature increased by 16.48 and 5.39 percent, respectively. decreasing of the input precipitation in most part of the world particularly in iran watersheds mentioned in many studies. one of the other the most important effect of the climate change in this area is minimum and maximum temperature increase that leads to evapotranspiration increasing and soil moisture loss. the results of the ihacres model showed that this model has the suitable capability for simulation runoff in the study area, therefore, it was used for estimating the future runoff regarding climate changes. the model output showed that during the next decades the average flow rate in the hydrometric stations will decrease by a total of 16 percent and the number of peak flood events will increase, that the highest increase between the study watersheds observed in the yamchi hydrometric station with a mean of 2.09 m3s1 and 16 peak events with over 6 m3s1. using the obtained results of the climatic model, hydrological model and the sediment rating curve the suspend sediment changes were estimated for the future period. the result shows that these climatic changes will lead to a 47 percent reduction in the average of suspended sediment load at study stations. conclusion the consequences of the climate changes have the significant effect on water resources quality and quantity. the aims of this study were calculating the weather changes and it’s ruling on discharge and sediment yield changed. the results of this study indicate the effect of climate change on the ardabil province watersheds is remarkable. considering the environmental impacts of climate change and dependence on human life on the environment it is necessary to implement an appropriate approach for decent management in watersheds.