Water resources analysis of the Rječina karst spring and river (Dinaric karst)

The paper deals with complex hydrological/hydrogeological behaviour in the Rjecina karst spring and river basin located in the north-western part of the deep and developed Croatian Dinaric karst. The Rjecina 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 Rjecina 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 Rjecina 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. Key words: hydrology, hydrogeology, karst, Rjecina Spring, Rjecina River, Dinaric karst. Analiza vodnih virov kraskega izvira in reke Rjecina (Dinarski kras) Clanek obravnava zapletene hidroloske/hidrogeoloske razmere v zaledju kraskega izvira in reke Riecine v severozahodnem delu globokega in dobro razvitega hrvaskega Dinarskega krasa. Izvir Rjecina je eden najvecjih kraskih izvirov na Hrvaskem, zajet je za oskrbo s pitno vodo za mesto Reka in njeno okolico. Poleg rabe izvira Rjecine za oskrbo z vodo je razlog za spremenjen hidroloski in hidrogeoloski režim celotnega zaledja tudi gradnja hidroelektrarne Reka (HEPP). Za analizo antropogenih vplivov na sistem smo zato naredili hidrolosko analizo pretokov reke in izvira Rjecina pa tudi analizo razpoložljivih podatkov merjenja podzemne vode. Analiza je pokazala, da se je zaradi povecanja zajemanja vode in zmanjsanja kolicine padavin povprecen letni pretok izvira v obdobju 1980–2016 zmanjsal za približno 25 %. Podrobna analiza meritev podzemne vode je nakazala znacilnosti delovanja vodonosnika ter pokazala potrebo po dodatnih meritvah in dolocitvi zaledja izvira. Kljucne besede: hidrologija, hidrogeologija, kras, izvir Rjecina, reka Rjecina, Dinarski kras.