MAIN HYDROLOGICAL FEATURES AND RECHARGE ANALYSIS OF THE CAPOSELE SPRING CATCHMENT, SOUTHERN ITALY

Main hydrological features and recharge analysis of the Caposele Spring catchment, southern Italy The Caposele spring supplies with water the Puglia region (southern Italy) since the beginning of the twentieth century by a wide and long (about 400 km) gravity-aqueduct system. Systematic spring discharge measurements exist since 1920. The annual mean discharge of spring is about 4 m3/sec, the spring catchment of the of Mt. Cervialto karst massif is estimated on more than 100 km2. The spring regime is characterised by absence of abrupt peaks in the hydrographs; the flood period occurs in spring-summer time, and the minimum during the autumn-winter time. Thus, the regime is almost opposite that of rainfall which allows a convenient management of the source. The historical data have shown that spring discharge depends also on the hydrological conditions of the previous year because the ‘‘memory effect” of aquifer. The recharge processes have been evaluated using a daily scale recharge model, calibrated on long term annual scale. The results allow to estimate the inertial behaviour of the aquifer, by the difference of recharged and discharged water volume during a hydrological year: after a wet year, an amount of water volume is retained into the aquifer and constitutes the surplus volume stored; after a dry year, the aquifer discharges a water volume higher than the recharged volume (a deficit in storage). Key words: karst aquifer, recharge model, spring discharge, storage, southern Italy. Glavne hidroloske znacilnosti in analiza napajanja zaledja izvira Caposele, južna Italija Izvir Caposele je od zacetka 20. stoletja glavni vodni vir Apulije (južna Italija). Voda je od izvira do mest gravitacijsko speljana po približno 400 km dolgem akvaduktu. Sistematicne meritve pretoka potekajo od leta 1920, povprecni pretok izvira je 4 m3/s, obmocje napajanja je kraski masiv gore Cervialto s povrsino preko 100 km2. Znacilnosti izvira so odsotnost izrazitih vrhov v pretocnem hidrogramu, visok pretok v pomladansko-poletnem casu in nizek pretok v jesensko-zimskem obdobju. Režim pretoka izvira je skoraj obraten od padavin, kar omogoca preprosto upravljanje vodnega vira. Zgodovinski podatki kažejo, da je pretok odvisen od hidroloskih razmer v predhodnem letu, kar je posledica velikega »spominskega ucinka« vodonosnika. Napajanje sistema smo ocenili na podlagi dnevnega modela napajanja, umerjenega na dolgorocno letno obdobje. Z razliko med napajanjem in odtokom v hidroloskem letu, smo ocenili inercijsko obnasanja vodonosnika. Izkaže se, da se v letu z veliko padavinami presežek napajanja skladisci v vodonosniku, v suhem letu pa je volumen odtoka vecji od volumna odtoka. Kljucne besede: kraski vodonosnik, model napajanja, pretok izvira, skladiscenje, južna Italija.