Manifestations of climate change in the ice regime of the rivers of the Debed River basin (Armenia)

Assessing of the dynamics regularity of the ice regime main characteristics on the Debed River basin rivers is an important scientific and practical issue for water management planning and implementation, water resources rational use and protection, and climate change. The article highlighted several questions for the whole observation period, the duration of the ice phenomena period and the dates when ice phenomena onset explored. The ice phenomena observations data for the Debed River basin provided by the «Hydrometeorology and Monitoring Center» SNCO of the Ministry of Environment of the Republic of Armenia. The study carried out for 15 locations at the Debed River basin based on a long-term time series (from 1939 up to 2018). Most of the Debed River basin rivers have unstable ice formation or do not freeze at all. Ice phenomena on the studied rivers have diverse features due to different climatic, morphometric and hydraulic conditions. Due to the high flow rates, ice is observed only in cold winters on the deep areas for a short period. Most rivers have various ice phenomena with different scales and duration. Also, there are almost no springs and autumn ice run and ice jams, but shore ice distributed wildly. Ice phenomena on rivers largely depend on the catchments altitude. On average for the river basin, ice phenomena usually begin from the second decade of November up to the third decade of December and end from the third decade of February up to the third decade of March. The changes dynamics in the beginning and end of ice events, the duration of ice events and ice cover at the Debed River basin assessed. Trends for two periods represented: 1966-1995 and 1996-2018. The changes in the dynamics of air and water temperatures, as well as of precipitation studied. The trend of air temperature is only positive, a more intensive increase of air temperature is observed in the period 1996-2018. The trend of water temperature and precipitation for the period 1966-1995 is negative, and for the period 1996- 2018 - positive. It was found that the current changes of the ice regime at the Debed River basin occur mainly under the influence of climate change conditions. In the context of climate change, there are shifts at the beginning of ice events to a later date, and at the end of ice events to an earlier date, which causes an ice phenomena duration reduction (especially since 1994 to 1995).

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