Air temperature is the main climatic variable for climate change and global warming assessment. In different regions, different climatic features and forcing factors affect air temperature behaviour ...and development differently. In this paper, time series of monthly and annual absolute minimum, mean and absolute maximum air temperatures measured in the period Jan. 1949–Dec. 2018 at two meteorological stations, Zagreb Grič and Lastovo, were analysed. The stations are situated in distinct climatological areas in geographically and climatologically completely opposite parts of Croatia. The climate of Zagreb Grič station is mild continental. Station Lastovo is located on the small isolated Adriatic Sea island, which has a hot Mediterranean climate. The distance by air between the two analysed meteorological stations is 340 km. In time series of the absolute annual minimum air temperatures measured at both analysed stations, an increasing trend is not statistically significant, while in the time series of mean annual and absolute annual maximum air temperatures, the trends are statistically significant at the level
p<0.01.
The statistically significant trend of air temperature increase at both stations appeared in the warm season of the year generally from May to August. The day-to-day (DTD) method established a decrease in night-time to night-time air temperature variability, and an increase in the day-time to day-time temperature variability at Lastovo. In Zagreb Grič, the situation is the opposite but the process is very slow.
Proposal of a new method for drought analysis Bonacci, Ognjen; Bonacci, Duje; Roje-Bonacci, Tanja ...
Journal of Hydrology and Hydromechanics,
03/2023, Letnik:
71, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Below-average precipitation and above-average air temperature are important factors in the occurrence and intensity of drought. In the context of global climate change, air temperature increase, as a ...key climatological parameter, has to be considered when calculating the drought index. We introduce a new method of drought analysis, relying on standardized values of precipitation and mean air temperatures for a certain period. The standardized value is calculated by subtracting the average value for each period from each measured value and dividing the obtained value by the standard deviation of the sample. Next, the New Drought Index (NDI) is calculated by subtracting the standardized temperature value from the standardized precipitation value. NDI values were determined for the monthly and annual precipitation time series and mean monthly and annual air temperatures measured at the stations Split-Marjan and Zagreb-Grič between 1948 and 2020. The NDI indicates that the risk of drought has intensified significantly in recent decades, which may be related to the effect of global warming.
The paper deals with complex hydrological/hydrogeological behaviour in the Rječina karst spring and river basin located in the north-western part of the deep and developed Croatian Dinaric karst. The ...Rječina Spring is one of the major karst springs in Croatia, used for water supply of Rijeka City and its surrounding area. Beside the use of Rječina spring for water supply, the development of the Rijeka hydroelectric power plant (HEPP) also changed hydrological and hydrogeological regime of the whole catchment. In order to analyse the anthropogenic influences in the system, hydrological analysis of the Rječina river and spring discharge was done, as well as the analysis of the available data of groundwater measurements. The analysis showed that, due to the increase of water caption and decrease of precipitation, the average annual spring discharge decreased for approximately 25% in the 1980-2016 period. Detailed analysis of groundwater measurements indicated aquifer behaviour and the need for additional measurements and catchment delineation.
The air temperature trends measured at the central meteorological station Varaždin and the water temperature measured at the Botovo station on the Drava River were analyzed from 1 January 1969 to 31 ...December 2021. Analyses were performed for three different time scales: year, month, and day. Mann–Kendall testing statistically determined the significant trends over the analyzed period and found increasing air and water temperatures. From 1975 to 1989, three reservoirs of different volumes and water surface areas were built. The Botovo water measuring station is 11 km from the third largest reservoir and 28 km from the mouth. Applying the day-to-day (DTD) method, we determined that the variations in the daily air temperatures are significantly higher than the simultaneous variations in the daily water temperatures. Also, the rise in water temperatures at the downstream water measuring station Botovo was influenced by the construction of reservoirs. The commissioning of the second reservoir in 1982 caused a significant rise in water temperature at the Botovo station. Trends in water temperature increase during all months of the year were statistically significant, while air temperature trends were statistically significant during the warm parts of the year.
The paper analyzes the data of groundwater level (GWL), groundwater temperature (TW), and electrical conductivity (EC) measurements in three deep piezometers (B1, B2, B3) in the Jadro spring basin, ...taken from October 2010 to December 2021. The variation of these parameters is analyzed at different time scales: annually, monthly, daily (24 hours), and hourly. They are compared with the data of the same parameters measured at the Jadro Spring. The analysis of the maximum observed rise and fall rates of the GWL showed that the piezometers were drilled in very different karst environments. Piezometer B1 is located in a karst matrix where the water flows predominantly in a diffuse laminar (slow-flow) regime. Piezometers B2 and B3 are located in a fault line where numerous large karst underground formations occur and rapid turbulent water flow takes place. The mean annual flows of the Jadro Spring strongly depend on the mean annual GWL-s in each of the piezometers. For much of the year (about 99%), the GWL in all three piezometers is more than 210 m below the ground surface. As the measuring sensors are located near the bottom of the piezometers, the groundwater temperature is almost stagnant. It is always at 12.5 ºC in piezometer B1 and behaves almost identically in piezometer B3. Water temperature is the highest in piezometer B2 and hovers around the average value of 13.5 ºC. At the Jadro Spring, the average water temperature is 12.95 ºC. The electrical conductivity values are the highest in piezometers B2 and B3, with an average of around 0.5 mS/cm. They are lower in piezometer B1, where they range around an average value of 0.465 mS/cm, while at the Jadro Spring, they vary from 0.40 mS/cm to 0.48 mS/cm, with an average value of 0.44 mS/cm. A distinct seasonal pattern in groundwater level behavior is evident across all piezometers. However, no discernible upward or downward trend is observed.
The Mediterranean region is one of the regions in the world that is most vulnerable to the impact of imminent climate change. In particular, climate change has an adverse effect on both the ecosystem ...and socioeconomic system, influencing water availability for both human and environmental purposes. The most endangered water resources are along the coasts and on islands since they have relatively small volumes and are intensively exploited. We analyzed the time series of air temperature and precipitation measured at four meteorological stations (Komiža, Palagruža, Lastovo, and Biševo) located on small islands in the Croatian part of the Adriatic Sea in this study. The investigated time series extend from the 1950s to the present, being contemporaneous for approximately 50 years. Despite possessing discontinuity, they can be considered as representative for assessing climate change and variability in the scattered environment of the Croatian islands. The results showed increasing trends in the annual air temperature, while the annual cumulative precipitation did not show significant variations. In addition, the analyses of the monthly air temperature showed that statistically significant increasing trends occurred from April to August, suggesting a more severe impact during these months. These results are in accordance with regional and local studies and climate models. Although the climate variability during the analyzed period can be considered as moderate, the impact on water resources could be severe due to the combined effect of the increase in air temperature during warm periods and the intensive exploitation for tourism purposes.
Relationship of Sea Surface Temperature (SST) and Surface Air Temperature (SAT) measured at the small island of Hvar (Adriatic Sea) are examined on annual and monthly time scales using data for a ...period of 55 years (1964-2018). The following three SST and SAT indices were analysed: (1) absolute minimum; (2) mean; (3) absolute maximum. The results highlighted a statistically significant increasing trend for all three SST analysed annual indices. In the case of SAT absolute minimum increasing trend is not statistically significant. For the other two indices the trends are statistically significant at the level, p<0.01. Monthly analysis for SST indices almost in all months (except October) have statistically significant increasing trends. In the case of SAT, a statistically significant increasing trend for all analysed indices occurred in summer (July and August). All results point out that the analysed region, especially small Adriatic islands are endangered of climate change, i.e. global warming during the summertime. Using the RAPS method on the minimum annual SST, a statistically significant shift upward was detected in 1988. Ten years later, in 1998, a statistically significant shift upward was detected on the mean and maximum SST and SAT indices. In the case of SAT minimum annual values, a statistically significant shift downward is detected, starting in 1979. In the analysed case of the Island of Hvar, the warming of SST indices is higher than the warming of SAT indices and occur during the whole year (except in October).
Intermittent and ephemeral streams (IRES) are responsible for transporting about half of the water on Earth’s surface. Their hydrological behavior is different in various landscapes. IRES are found ...more often in karst terrains than in any other regions, as a consequence of strong and direct interaction between groundwater and surface water. This paper presents a hydrogeological and hydrological analysis of the intermittent Čikola River and Spring catchment, which is located in deeply karstified and developed parts of the Dinaric karst in Croatia. Hydrological calculations determined that the catchment area covers approximately 300 km2 and very probably changes in accordance with rapid variations in groundwater level. The karst spring of the Čikola River is a cave, extracted for a public water supply with four drilled extraction wells. The results of the interrelated hydrological and hydrogeological analysis show interesting phenomena from an intermittent karst spring (cave) and its catchment, flowing downstream through a karst polje with several smaller confluences, then entering a karst canyon (where the river sinks during certain periods), and ending in an estuary before contributing to the larger Krka River. The research presented was based on water balance calculations, climatic and hydrological time series analyses, spring pumping tests, and thorough hydrogeological interpretation.
PDF
