شناسایی رابطه شدت مدت بارش‌ها با دبی جریان در رودخانه دز تحت تاثیر بارش‌های فوق سنگین (سیلاب سال های 2016و 2019)

بارش مهمترین و موثرترین منبع آب یک حوضه ابریز می باشد که با توزیع نابرابر مکانی و زمانی در سطح حوضه تغییر می کند. در این پژوهش دو بارش سنگین که منجر به بروز سیلاب‌ در سال‌های 2016 و 2019 شد به منظور آگاهی و شناخت سازو کارهای موثر بر رخداد این بارش ها و شناسایی رابطه شدت مدت بارش با دبی جریان مورد بررسی واقع گردید. جهت تحلیل این روابط رویکرد محیطی به گردشی انتخاب شد. بعد از ترسیم نقشه های سطوح بالای جوی و تشخیص سامانه موثر در ایجاد بارش‌های فوق سنگین، دبی سیل ایجاد شده ناشی از سامانه های مذکور از داده های ثبت شده استخراج گردید. سامانه موثر در ایجاد بارش های فوق سنگین، سامانه کم فشار سودانی می باشد. نتایج بدست آمده نشان می دهد که دبی اوج سیلاب‌ها با تاخیری 12 تا 24 ساعته از روز اوج بارش‌ها بوده است و روند افزایشی رواناب ارتباط بسیار تنگاتنگی با افزایش شدت و تداوم بارش ها دارد. مقادیر دبی بدلیل بارش‌های فوق سنگین با مجموع بارش‌های بیش از 160 تا 120 میلی‌متر در برخی از ایستگاه‌ها بصورت تصاعدی هندسی در ایستگاه‌های هیدورومتری ثبت شده‌اند.

identifying the relationship between intensity duration of rains and flow rate in dez river under the influence of heavy rains (2016 and 2019 floods(

introductionprecipitation is the most important and effective source of water in a watershed, which changes with uneven spatial and temporal distribution in the basin. in this research, two heavy rains that led to floods in 2016 and 2019 were investigated in order to know and understand the mechanisms affecting the occurrence of these rains and to identify the relationship between the intensity of the rainfall and the flow rate. in order to analyze these relationships, an environmental approach was chosen. after drawing the maps of the upper atmospheric levels and identifying the effective system in causing super heavy rains, the flood discharge caused by the mentioned systems was extracted from the recorded data. the most effective system in causing heavy rains is the sudanese low pressure system. the peak flow of floods has been delayed by 12 to 24 hours from the day of peak rainfall and the increasing trend of runoff is closely related to the increase in intensity and continuity of rainfall. due to heavy rains with total rains of more than 160 to 120 mm in some stations, the discharge values have been recorded geometrically exponentially in hydrometric stations. the importance of investigating the phenomenon of precipitation is more obvious when a place witnesses a small or significant fall or suddenly a large amount of precipitation. in recent years, several studies have been conducted in relation to heavy rains, heavy rains and flood potential in the synoptic method and with the help of maps of different levels of the atmosphere in the world and in iran. considering the importance of rainfall and its impact on various economic, agricultural and social sectors, the need to investigate and identify the synergistic patterns of rainfall in the study area for use in planning and optimal management of water resources is evident. ecosystems and physical structures of human societies are adjusted to normal climatic conditions, and when extreme climatic phenomena occur, they can rarely equip and prepare themselves. therefore, the temporal variability of precipitation, especially extreme precipitations, has many economic effects.materials and methodsthe study method in this research is a combination of field method and statistical analytical method. research is of applied type. obtaining atmospheric data of pressure, omega, specific humidity and flow for the indicated atmospheric levels during a 33 year period (1990 2017) from the website (ncep/ncar) and european center for medium range forecasting (ecmwf) determining the heaviest precipitations that occurred in the dez river basin with the index method 98% percentile base and then determining the most durable rain waves (indicator waves) in each year and taking into account the duration of rainy days during the 33 year statistical period (1990 2017) and drawing weather maps using grads and surfer software and performing factor analysis method and clustering and visual analysis to identify the atmospheric patterns of heavy and long term rainfall occurrences and synoptic analysis of the atmospheric patterns of heavy and long lasting cloud precipitations and the investigation and analysis of the historical course of heavy and long term cloud precipitations and the investigation and analysis of the degree of correlation or the relationship between the intensity of rainfall and the intensity of surface runoff and choosing the factor that expresses the highest intensity of rainfall.results and discussionthe findings of this research are presented in two separate sections. in the first part, synoptic patterns leading to selected super heavy rains will be presented. in the second part, the flood discharge resulting from these extremely heavy rains has been analyzed.