engleski

Stable isotope composition of precipitation as signal of possible climate change: the case of the mountain Učka (Northern Adriatic, Croatia)

The highest average annual rainfall in Croatia is in the Northern Adriatic, with some parts of the region receiving more than 2000 mm per year. Characteristics of the region’s weather are periods of intense rain alternating with dry periods in which the amount of precipitation can be negligible for more than a month. The area's water supply relies on karst groundwater sources that are primarily fed by Mediterranean precipitation. The aforementioned precipitation regime results in high groundwater yields in the cold part of the hydrological year and substantially decreased water quantities in the summer months. Under such specific conditions, it is of considerable importance to find out about the potential for climate change in order to ensure timely adjustment of the management and use of natural sources of water. We present a comparison of the isotopic composition of precipitation collected on the mountain Učka in periods 2008-2011 and 2019-2020. Rain gauges were located on a vertical gradient from sea level up to nearly 1400 m. Unlike the isotopic altitude effect that did not change significantly compared to the one reported for the first period (Roller- Lutz et al, 2013), the weighted means of isotopic values were more positive in the second period. For the cold part of the hydrological year, local meteoric water line has recently moved to higher values, indicating the sources of precipitation from drier Mediterranean regions. Local meteoric water line for the warm part of the last hydrological year, indicates presence of increased evaporation and thus confirms lower precipitation amounts.

water stable isotopes ; climate change

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