Risk assessment of contamination of groundwater in karst in the recharge area of the Jadro and Žrnovnica springs : doctoral thesis

U posljednje vrijeme sve se više ističe neprocjenjiva vrijednost zaliha podzemnih voda visoke kakvoće koje se nalaze u krškim područjima Republike Hrvatske. Zajedno s tim dolazi i spoznaja o iznimnoj ranjivosti krških vodonosnih sustava koji su zbog svojih karakterističnih obilježja jako podložni negativnim antropogenim utjecajima. U ovom radu predložen je pristup zaštite krškog vodonosnog sustava od istraživanja njegovih geoloških, hidrogeoloških i hidroloških značajki do korištenja rezultata tih istraživanja u multiparametarskim metodama procjene ranjivosti, opasnosti i rizika od onečišćenja podzemnih voda. Područje istraživanja obuhvaćeno ovim radom je sliv izvora Jadra i Žrnovnice. Izvori Jadro i Žrnovnica predstavljaju nezamjenjive izvore pitke vode za stanovništvo grada Splita i njegove šire okolice, kao i osnovni uvjet socio-ekonomskog razvoja tog podruĉja. Na temelju do sada provedenih istraživanja uočen je trend narušenja kakvoće izvorskih voda u uvjetima naglašenog gospodarskog razvoja, kao i neodgovarajuće zaštite izvorišta pitke vode. Koncept prirodne ranjivosti podzemnih voda temelji se na pretpostavci da fizikalna, kemijska i biološka svojstva okoliša mogu, do nekog stupnja, pridonijeti zaštiti podzemnih voda od antropogenih utjecaja. Analizom rizika od onečišćenja podzemnih voda izdvajaju se dijelovi sliva koji su zbog svojih prirodnih značajki ranjiviji na vanjske utjecaje i dijelovi sliva koji su već ugroženi zbog postojećih izvora onečišćenja. Istraživanje rizika provodi se u tri faze: izrada karte prirodne ranjivosti, zatim izrada karte opasnosti, te na kraju njihovo integriranje u kartu rizika podzemnih voda od različitih vrsta izvora onečišćenja. U ovom radu prirodna ranjivost procijenjena je pomoću četiri postojeće metode SINTACS, EPIK, PI i COP. Svaka od tih metoda modificirana je i testirana na temelju karakterističnih pokazatelja područja i na kraju je predložen najprihvatljiviji pristup procjene prirodne ranjivosti prilagođen dinarskom kršu Republike Hrvatske. Izrađena je karta klasificiranih opasnosti u slivu Jadra i Žrnovnice, te je na kraju predstavljena karta rizika od onečišćenja podzemnih voda u slivu Jadra i Žrnovnice. Sve tri karte predlaže se koristiti za upravljanje i zaštitu zaliha podzemnih voda na području sliva, pri određivanju prioritetnih sanacijskih zahvata, te pri odlukama o korištenju i namjeni prostora.It is well known that groundwater is the main source of potable water in the Republic of Croatia. Approximately half of the country’s territory is covered by karstified carbonate rocks, the so-called Dinaric type of karst, which are famous by the priceless supplies high quality groundwater. This is why the utmost caution must be paid explicitly to groundwater protection in karst aquifers. Karstified carbonate rocks are typically covered by a thin, irregularly distributed soil layer, and are intersected by a multitude of interconnected fractures facilitating the rapid infiltration of surface water. Groundwater flows through the conduits and fissures with high velocity and with a relatively short retention time, allowing the quick and far-reaching spread of potential contamination from the surface. This is why karst aquifer systems are thought to be extremely vulnerable and easily threatened by each and every human activity. This doctoral thesis proposes approach to the protection of the karst aquifer system from exploration of its geological, hydrogeological and hydrological features to the use of these studies results in the methods of vulnerability, hazard and risk of groundwater contamination assessment. Study area encompasses the catchment area of the Jadro and Žrnovnica springs of approximately 560 km2 located in the wider hinterland of the city of Split. It is part of the Cetina river basin. The springs are located in the foothills of the Mosor and Kozjak Mts. in the contact zone between permeable carbonate sedimentary rocks and the coastal flysch belt. Jadro is situated at an altitude of 35 m a.s.l., while Žrnovnica lies at the altitude of 90 m a.s.l. According to the available hydrological data, the minimum discharge of the Jadro spring ranges between 3.60 m3/s (August 1995) and 3.90 m3/s (September 1997, August and September 2003). Žrnovnica joins several smaller springs upwelling in the broader area. The minimum measured discharge of this spring area is up to 250 l/s (September 1993) while the maximum discharge is up to 19.1 m3/s (December 2004). The Jadro spring is used for the water supply of Split, surrounding settlements and the towns of Solin, Kaštela and Trogir. Žrnovnica is used for the water supply of the village of Žrnovnica and irrigation of agricultural areas. The catchment area is predominantly composed of carbonate rocks, limestone and dolomite, and flysch sediments, while other rocks occur more rarely. Three quarters of the catchment area are composed of permeable carbonate rocks and because of that it is even more difficult to protect groundwater resources. Jadro and Žrnovnica springs are irreplaceable sources of drinking water for the population of the city of Split and its surroundings as well as the basic requirement of socio-economic development of the area. Data from an earlier conducted researches shows an increasing trend in the quantity of a number of contaminants in the spring water due to economic expansion in the catchment area and lack of appropriate protection of drinking water sources. The concept of groundwater intrinsic vulnerability is based on the premise that the physical, chemical and biological properties of the environment provide a certain degree of protection to the groundwater from human influence. Risk assessment of groundwater contamination identifies parts of the catchment area that are, because of its natural features, more vulnerable to external influences then those parts of the basin that are already at risk because of existing contamination sources. Risk assessment is carried out in three phases: assessment of intrinsic vulnerability, hazard mapping and integrateing these two maps into the groundwater risk map. In this paper, intrinsic vulnerability was assessed by four methods: SINTACS, EPIK, PI i COP. Each of these methods were modified and tested based on the characteristic parameters of the study area. Results of the applied methods (corresponding vulnerability maps) were compared and finally it is proposed the most suitable approach for evaluation intrinsic vulnerability adjusted to Croatian Dinaric karst. Furthermore, a map of classified hazards in the catchment of Jadro and Ţrnovnica springs was created. The final result of this analysis is the risk of groundwater contamination map in the catchment area of Jadro and Žrnovnica springs. All three maps are utilized primarily for groundwater management and protection in the particular area and as an irreplaceable background for decision making in management and land use