Climatic water balance dynamics over the last five decades in Romania's most arid region, Dobrogea

The analysis of a territory's climatic water balance dynamics against the background of climate change is a key component for increasing water resource management efficiency. The present study aims to analyse climatic water balance (CWB) dynamics in Romania's most arid region, Dobrogea, located in the southeast. The study covers the 1961-2009 period, and is based on annual and seasonal CWB values (mm), provided by nine weather stations located throughout the region. The study, based on statistical and GIS techniques, is divided into two main stages, both carried out at annual and seasonal scales-trend analysis using the Mann-Kendall test, the Sen's slope method, and CWB value distribution type analysis. In order to identify the probabilistic types of distributions, four mathematical models were identified-Pearson, Gamma, Chi-Squared and Wakeby, statistically verified with the P-P Plot, Q-Q Plot and Probabillity Difference Graph (PDG) curve tests. Thus, in terms of trends, the results showed a deficit increase especially at the northern stations, mainly for annual values (with a peak in the northeast, where CWB rates reached -3.2 mm/yr). While general CWB declines occurred in winter, spring and summer, apparent decrease rates were found in the northern region (highest negative rates-summer, northwest, -1.4 mm/yr). Autumn is an exception, due to overall increase rates which peaked in the southwest (2.3 mm/yr). However, the entire trend analysis indicated a general lack of statistical significance. The distribution type histogram analysis showed that, annually and seasonally, deficit values are generally dominant (more noticeable in the northern region), except for the winter season, mainly characterized by surplus intervals. Thus, the results suggest a climatic water deficit increase over the last five decades especially in northern Dobrogea, which signals the need for a spatial prioritization targeting a more efficient water resource management, necessary first and foremost for increasing regional agricultural system productivity.