@article { author = {Asgari, Ebrahim and Esmali-Ouri, Abazar and Mostafazadeh, Raoof and Ahmadzadeh, Gholamreza}, title = {Spatial variations of runoff, sediment and runoff threshold of Gharehshiran watershed in Ardabil Province}, journal = {Journal of the Earth and Space Physics}, volume = {44}, number = {3}, pages = {697-713}, year = {2018}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2018.253440.1006980}, abstract = {Diverse factors affect the characteristics of the watershed that lead to spatial and temporal variations in the runoff and sediment production processes. Runoff and sediment are the main important elements in the hydrological cycle, and their changes directly affect river systems and sedimentary environments; and their spatial and temporal variations change the morphology of the rivers. Due to differences in soil characteristics, source materials and geological formations, vegetation and slope in different parts of a region, the amount of runoff and sediment produced in these areas can vary with spatial variations. The purpose of this study is to evaluate the spatial variations of runoff and sediment and runoff threshold using rainfall simulation data in the Gharehshiran watershed in Ardebil Province. Considering the importance of spatial distribution of sampling points across the catchment area, the locations of the samples were determined, taking into account the access path to the points, as well as sampling in different formations through determining the boundaries of the study area. The field experiments and simulation of precipitation were carried out using a 1×1m rainfall simulator in 45 points in different geologic formations of the watershed area. The amount of runoff and sediment were measured in each experiment along with recording the threshold time of runoff generation. The measured variables were mapped and interpolated by using Kriging method over the study area. To assess the accuracy of the interpolation results, 7 samples were selected randomly and the Root Mean Square Error (RMSE), Mean Absolute Error (MAE) and Mean Bias Error (MBE) statistical measures were calculated by comparing observational and estimated values. Then, the correlation between the studied variables in various geological formations was evaluated using Pearson correlation analysis. The relationship between sediment and runoff amount, and runoff threshold time were also evaluated using a triple diagram model. The results of the interpolated maps showed that the lowest values of runoff time threshold (1.99-3.17 min) were observed in the geological formations of upper part of the watershed having dacite and tracite igneous, volcanic rocks. While the runoff time thresholds were increased (6.13-7.25 min) in the low land areas with the old alluvial terraces. The amount of generated runoff in the upper hillslopes of the watershed with dacite and tracite rocks was estimated as (6.07-7.25 lit/m2), and the amount of sediment was low (1.25-1.66 g/l). Meanwhile, in the lower parts of old alluvial terraces, the amount of runoff production was low (2.20-3.50 lit/m2) and the amount of produced sediment was higher with values of (2.25-3.5 g/l). The results of correlation analysis showed that the correlation coefficients between runoff threshold and runoff volume were significant at 0.01 significant level (r = -0.802). Also, a significant negative correlation (r = -0.672), were observed between runoff and sediment values. The relationship between the runoff time threshold and the sediment content was positive at significant level of 0.01 (r = 0.900). The results of interdependency between the sediment, runoff and runoff time threshold values using triple diagram models showed that the sediment amount was about 2g/l at high runoff time thresholds of 4 minutes with 2.5-5.5 lit/m2 runoff amounts. In general, it can be said that the sediment production in the study area is strongly under the effects of runoff amounts in lower time thresholds of runoff. As a remark, the results pointed out that the internal relationship of runoff and sediment production are affected by a variety of effective factors which requires comprehensive studies to reach a final conclusion.}, keywords = {Spatial Variation,Rainfall simulator,Runoff threshold,Geologic Formations,Gharehshiran watershed}, title_fa = {تغییرات مکانی رواناب، رسوب و آستانه شروع رواناب در حوزه آبخیز قره‌شیران اردبیل}, abstract_fa = {تعدد عوامل مؤثر در خصوصیات حوزه آبخیز منجر به تغییرات مکانی و زمانی در فرآیندهای تولید رواناب و رسوب می‌شود. پژوهش حاضر با هدف ارزیابی تغییرات مکانی مقادیر رواناب، رسوب و آستانه شروع رواناب با استفاده از داده‌های شبیه‌سازی بارش در حوزه آبخیز قره‌شیران اردبیل انجام گرفت. شبیه‌سازی بارش با استفاده از دستگاه باران‌ساز در 45 نقطه در سازندهای مختلف زمین‌شناسی حوزه آبخیز انجام و پس از اندازه‌گیری مقدار رواناب و رسوب در هر نمونه متغیرهای مورد مطالعه با روش کریجینگ درون‌یابی و تغییرات مکانی ارزیابی و ارتباط مکانی مقادیر این متغیرها مورد بررسی قرار گرفت. نتایج نقشه‌های درون‌یابی نشان داد که سازندهای بخش‌های بالادست حوزه آبخیز (گدازه‌های داسیتی و تراکیتی) در آستانه‌های پایین (17/3-99/1 دقیقه) رواناب تولید می‌شود و به سمت سازندهای بخش‌های پایین‌دست (مانند پادگانه‌های آبرفتی قدیمی) آستانه تولید رواناب (25/7-13/6 دقیقه) افزایش می‌یابد. مقدار رواناب در بالادست حوزه (گدازه‌های داسیتی و تراکیتی)، زیاد (25/7-07/6 لیتر بر مترمربع) ولی مقدار رسوب کم (66/1-25/1 گرم بر لیتر) و در پایین‌دست حوزه (مانند پادگانه‌های آبرفتی قدیمی) مقدار رواناب تولیدی کم (50/3-20/2 لیتر بر مترمربع) و مقدار رسوب تولید شده بیشتر (5/3-25/2 گرم بر لیتر) می‌باشد. نتایج ارتباط بین مقادیر تغییرات رسوب، رواناب و آستانه شروع رواناب در نرم‌افزار Surfer نشان داد که در آستانه‌های بالای 4 دقیقه و رواناب‌های بین 5/5-5/2 لیتر، مقدار رسوب بیشتر از حدود 2 گرم بر لیتر می‌باشد و به‌طور کلی می‌توان گفت که در آستانه‌های پایین اثر تولید رواناب بر تولید رسوب در حوزه بیشتر است و در آستانه‌های بالا اثر تولید رواناب کاهش می‌یابد.}, keywords_fa = {Spatial Variation,Rainfall simulator,Runoff threshold,Geologic Formations,Gharehshiran watershed}, url = {https://jesphys.ut.ac.ir/article_67783.html}, eprint = {https://jesphys.ut.ac.ir/article_67783_2bcf903f41e24d8ec837ee370c59efee.pdf} }