The island of Korčula is located along the eastern coast of the Adriatic Sea. It has Mediterranean climate with mild and wet winters and hot and dry summers. The island's water supply has been managed in two ways: through a pipeline from the mainland and by drawing groundwater. The island's water is mainly used for drinking and for sanitary needs of the population and tourists, and only a small part is used in industrial production. Tourism causes high seasonal water needs which can hardly be met with the existing water supply system. Agriculture has long tradition on the island. Today, 3 500 ha are cultivated which is about 12.7% of island area, while only 20 ha are irrigated. Therefore total agricultural production is variable and mainly depends on climate. Due to more often and stronger droughts, yields are decreased which causes high economical losses. This paper deals with island's natural features, water needs especially for agriculture, water resources management and finally it suggests measures and activities to improve existing water use.

The article analyses the series of annual, monthly and daily air temperatures and annual and monthly rainfall at two meteorological stations in Vela Luka and Korcula on the island of Korcula (Croatia), for which there are long time series of observations. Today's locations of meteorological stations are only 33.5 km apart.The average annual air temperature at the Vela Luka station is on average 1 degrees C lower than that measured at the Korcula station. A significant upward trend in mean annual and mean monthly air temperatures was observed at both stations, with the increase being much milder at the Vela Luka station. Warming processes are significantly faster at the Korcula station than at the Vela Luka station. Significantly different values of air temperatures, and in particular the fact of different reactions of air temperatures to climate change at two stations, can be explained by their local position in relation to the open sea and orography of the surrounding terrain. While the Vela Luka station is exposed to the open sea and away from the mainland, at Korcula station the impact of the sea is less significant because the sea is located in a narrow channel between the island of Korcula and the Peljesac peninsula. The distance of the Korcula meteorological station from the Peljesac peninsula and the mainland is significantly smaller, which affects the faster trend of rising air temperatures at this station than at the Vela Luka station, where the influence of the sea mitigates the effect of global warming. Orography and proximity to land affect significantly higher rainfall occurrences at Korcula station. Average annual rainfall at this station is 231 mm or 27.5% higher than at Vela Luka station. Both stations show a trend of decreasing annual rainfall.

The Miljašić jaruga is one of the most important watercourses in Zadar County (Dalmatia, Croatia). The total length of this area is approximately 16 km, with an associated topographic catchment of approximately 191 km2. The downstream portion of the stream is influenced by the sea (estuary). The hydrological regime of the Miljašić jaruga is strongly influenced by climatic features; therefore, for most of the year, there is an outflow of catchment waters, whereas in the summer dry months, the river bed is mostly without outflow. It is also common for extreme precipitation to occur after a long dry period, resulting in sudden increase in water levels and flash floods. One such extreme event occurred on September 11, 2017, when a severe storm followed by heavy rain affected Zadar and its hinterlands. On that occasion, approximately 240 mm/m2 fell in Zadar over a period of 6 h, with an intensity of up to 70 mm/m2/h. Such extreme rainfall activated violent and torrential runoff, flooding, and damage in the entire catchment area of the Miljašić jaruga, particularly in the most downstream part of the basin, in the area of the estuary and the town of Nin. Numerous infrastructural and communal facilities have been damaged, including the Nin Salt Works. This paper presents the hydrological analysis of a flash flood event in the Miljašić jaruga estuary. A hydrological series of 26 and 27 years were compared, whereas the longer series include historical flood, using three distributions: normal, log-normal and Gamma. The relevant hydrological parameters (water levels and flows) used for dimensioning the flood defense system show great variability depending on the available data (time series) and calculation methodology. For example, variation of flow rate reached 41 m3/s for 100-year high waters, that is, from 60 m3/s (n = 26, normal distribution) to 101 m3/s (n = 27, log-normal distribution). In engineering practice, the unreliability of the estimation of statistical quantities should be considered to improve the effectiveness of flood defense systems. The rehabilitation and reconstruction work conducted after a flood on hydrotechnical structures (embankments) in the estuary area is described. In addition, there is a need for adequate water management across the entire basin, such as the construction of retention and barriers, which would increase the level of flood protection in the most downstream parts, i.e., the estuary.

The Peruća Reservoir, a critical karstic water resource in Dalmatia, Croatia, experiences significant water quality fluctuations influenced by rapid surface and groundwater recharge and climate change. This study develops a predictive framework utilizing a hybrid Graph Neural Network (GNN) and Transformer model to forecast key water quality parameters. Based on a dataset of monthly surface water quality measurements from 2019 to 2021, including water level, dissolved oxygen (DO), electrical conductivity (EC), pH, hardness, temperature, and precipitation, the model accurately predicts the Water Quality Index (WQI), DO, and EC ( R ² > 0.92 for 5-day forecasts). The analysis focuses on temporal water quality variations at a single monitoring station due to data limitations, with spatial resolution limited to inflow influences. Climate projections for 2050, assuming a 5% decrease in precipitation and a 1.7 °C temperature rise, indicate a potential decline in reservoir water levels by 0.75–1.17 meters and a summer WQI reduction to 67–70. The proposed model consistently outperforms benchmark Random Forest and Long Short-Term Memory (LSTM) models, demonstrating its robust predictive capability and providing crucial decision-support for the sustainable management of karstic reservoirs.