**Table3.**Mann-Kendalltestresults.

#### **4. Discussion**

Like in other studies, we also found the highest precipitation (more than 1200 mm) to be over the Adriatic coast, the Alpine region, and over the coast of Turkey and the Atlantic Iberian Peninsula. The lowest precipitation was found in the southeast region of the basin, over the southern Iberian Peninsula, and over the northern coast of Africa, with less than 400 mm of precipitation. Past studies determined that precipitation changes in the MB are partially influenced by North Atlantic Oscillations (NAO), upon which their vegetation dynamics and compositions are based. Precipitation is significantly correlated with the NAO, which is known to be the primarily responsible atmospheric event for budget fluctuations; however, no significant correlation has been found for evaporation yet [48]. Besides that, there could be multiple factors that act together and contribute to the basin's hydrological responses. They could be region-specific characteristics, topography, geography, location, or precipitation regimes; however, their proportional influence has not yet been accounted for in the basin. A recent study indicated that the incoming P flux mostly comes from sources inside the Mediterranean. This proportion is only 35%, while 10% is from ET over nearby land in continental Europe, and 25% originates in the North Atlantic. The remaining 30% comes from the tropical Pacific or the Southern Hemisphere, indicating its direct connections with multiple locations on earth due to a global terrestrial energy redistribution. Therefore, fluxes have a more global than regional influence that links climate change effects with the water cycle in the basin [49,50].

As also noticed over Turkey and the west Balkans (Figures 5c and 6), hydro-climatic fluctuations are projected to increase, which would decrease annual precipitation in the southern Europe–Turkey region and the Levant, while in the Arabian Gulf area precipitation may increase. Besides that, daytime maximum temperatures appear to increase most rapidly in the northern part of the region, i.e., the Balkan Peninsula and Turkey, which means more evaporation. This will have marked effects on the ecosystems' productivity and functioning, as seen in the analysis. Moutahir [51] also noticed negative trends in the different water balance components, although they focused on the pine stands in the sub-humid belt of Spain; according to their budget analysis, the native pine population is likely to disappear in the future under extreme climate scenarios of water stress. The waterlimiting conditions in the region are threatening for native tree plantations. Even the small quantity of water used by trees is important in the hydrologic budget of the Mediterranean areas where rainfall is limited; this indicates how significant the accurate computation of AET is in the budget [52]. In these regions, AET is mostly found to be higher: more than 54% of total precipitation, and mostly where tree density was lower [53]. This also shows how crucial precipitation is for forest growth and how it can control regional forest expansions or declines. Since many projected studies revealed that rainfall frequency is likely to be lower in the future, it would reduce the chances for aquifer recharge, despite their increasing size with extreme rainfall events. Changes in the precipitation intensity, size, and temporal distribution are expected in this region, and will have different effects on the water balance. Even in older studies, after precipitation, evaporation is recorded as the largest term in the Mediterranean freshwater budget in the 50 years of one study period (1948–1998) [48]. They also found that the Mediterranean region was under a freshwater deficit at the annual scale. The decrease in open water evaporation under future climate scenarios as a result of increased relative humidity will have a positive effect on the water cycle, but this trend would be seasonal and common in the winter only.

The goal of this paper was to provide a picture of the mean annual water budget along with the long-term variability of hydrological fluxes in the MB. It also justifies that complex morphology and climate variability contribute to significant annual differences in total precipitation and its geographical distribution. Rainfall and surface inflows (streams and rivers) are the major inflows, whereas evapotranspiration from different land uses and drains from the region to sea are the major outflows. A recent in situ study in Italy also validated our conclusion about the deficit state of the basin. They found a negative trend in the estimated infiltration for the consecutive five hydrological years (2017–2022). This

infiltration decrease was associated with a decrease in precipitation; however, they found AET in a less significant negative trend in the same period. This affirms that climate stresses are dominant in the MB, and that reduced surface water input will affect the groundwater input as well [54,55]. Scarascia-Mugnozza et al. [56] measured the hydrological balance at different integration times and found evapotranspiration was correlated to the water status of soils and plants. The indicated water stress can affect carbon metabolism, the water relations of forest trees, and ecosystem stability. All in all, AET was found to be an effective measure. This study highlights that both the accounting of the water budget at multi-scale and multi-functional systems are very important in considering the significant climatic influence over the water cycle and the budget. These findings could facilitate future climate preparedness and monitoring tasks.
