The observed changes in the precipitation regime in Romania – constraints for river restoration

The success of river restoration depends on precipitation and their hydrological effects. In the context of global warming, an increase in the frequency of extreme events has been observed, with a rapid alternation between periods of excess precipitation with floods and periods of deficit precipitation with drought. Understanding the spatio-temporal variability of the precipitation regime allows to set guidelines for river restoration at a large scale. The main aim of the study is to analyze the variability and observed changes in the precipitation regime in Romania. The research is based on the monthly amounts and maximum precipitation in 24 hours data recorded at 23 meteorological stations, which are part of the Regional Basic Synop Network (RBSN) and belong to the National Meteorological Administration (NMA), for the period 1981 – 2020. Based on these monthly data, the annual, seasonal and semestrial precipitation amounts were calculated. Standardized anomalies and decadal averages were also calculated both annually and for the months January, April, July and October, which are considered typical months from a climatic point of view. The analysis of changes in the precipitation regime is completed by calculating linear trends and statistical significance at annual and seasonal level by applying the Mann-Kendall statistical test. From the analysis of these monthly data of the precipitation amounts, it was found that from January or February to June or July, the monthly precipitation regime shows ascending values, which then gradually decrease until the end of the year. The annual precipitation amounts, at the level of Romania, decrease from west to east as a consequence of oceanic influence’s decrease in the same direction. The variation of the average decennial values of the precipitation amounts indicates increases and decreases from one decade to another, but without significant changes. The trend of average monthly precipitation amounts is predominantly decreasing, but without being statistically significant according to the Mann-Kendall test. In Romania, in the transitional temperate continental climate, the great variability of precipitation in time can be a drawback for self-sustainable river restoration.

D.M. (Oprea) Constantin, I.A. Șandor and G. Ioana-Toroimac were supported by a grant of the Ministry of Research, Innovation and Digitization, CNCS - UEFISCDI, project number PN-III-P1-1.1-TE-2021-0600, within PNCDI III.