In addition to air temperature at 2 m above ground, the following water balance components are considered: precipitation amount, potential and real evapotranspiration, surface runoff, recharge of water into the soil, loss of water from the soil, soil moisture content, and measured river discharge. Monthly air temperature and values of all water balance components (some of calculated using the Palmer method) have been considered for 24 weather stations across Croatia for the period 1951–2000, and for the Zagreb-Grič station for a much longer period, 1862–2000. The Sava River discharge for two hydrological stations (Zagreb and Županja) for the period 1931–2000 has also been used. Twenty-five year moving averages have been calculated from annual mean values and, – for air temperature only, a principal component analysis has been performed. We have found a long-term positive trend in air temperature, and potential and real evapotranspiration; and a negative trend in runoff (discharge) over almost the whole of Croatia, while the moving-average precipitation amounts show cyclical variation. No obvious trend for the recharge of water into the soil and its losses from the soil have been found, however, a negative trend in soil moisture content has been observed. The positive trends in air temperature and potential (real) evapotranspiration and the negative trends in soil moisture content and runoff (discharge) are consistent (to some degree) with recent global climate warming. This fact strengthens the importance of this study.

Theoretical and applied climatology

Earth Sciences; Meteorology/Climatology; Waste Water Technology / Water Pollution Control / Water Management / Aquatic Pollution; Climate Change; Atmospheric Protection/Air Quality Control/Air Pollution; Earth, ocean, space; External geophysics; Water in the atmosphere (humidity, clouds, evaporation, precipitation); Exact sciences and technology; Meteorology; Southern Europe; Europe; Croatia; time series analysis; Dynamical climatology; Century 20th; Meteorological observation; trend-surface analysis; Hydrometeorology; global change; climate warming; Observation data; water balance; Long term variation; climate change

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