engleski

Comparison of spring discharge on the three most important high-karst rivers in Croatia – Kupa, Gacka and Una

Kupa, Gacka and Una are the three most important high-karst rivers in Croatia due to their pronounced source zones. Presently, only the Gacka source zone is used for water supply, but future needs may call for broader exploitation of underground water reserves in these zones. Therefore, we have performed a hydrological analysis of water discharge from Kupa, Gacka and Una springs. Special attention was given to preservation of mentioned springs, since all of them have been proclaimed as natural heritage and categorized as hydrological monuments of nature. Herein we analyzed the characteristic time series of discharge, trends, yearly distribution of flow, recession curve, autocorrelation and cross-correlation functions. Comparison of water discharge with rainfall was carried out and reaction rate of karstic aquifers at each source zone was determined in response to the rainfall. On a longer time-scale we have found a general similarity between the aquifers in the Kupa, Gacka and Una source zones, but some differences are present in short-term reaction to change in hydrological conditions. Gacka springs have the highest underground water reserves, while Kupa and Una tend to quickly drain their aquifers. In that sense we recommend that plans for future development of water supply should not include Kupa and Una springs, since their value as noteworthy monuments of nature is much higher.

hydrological analysis; water supply; karst spring; water discarge; karstic aquifers

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