UDC 556.34:551.44(474.2) Oliver Koit, Nataša Ravbar, Andres Marandi & Jaanus Ter-asmaa: Treshold-controlled three-stage hydraulic behaviour of a mantled shallow carbonate aquifer (Tuhala karst area, North Estonia) As karst aquifers are often characterised by non-linear behaviour , ascertaining the turning points in their hydraulic regime may provide essential information on the functioning of the aquifer. These characteristics also apply to the Silurian-Ordo-vician aquifer system, composed of diverse carbonate rocks, in Estonia. The aquifer system is an important source of drinking water in northern Estonia. It also comprises the Nabala-Rakvere aquifer, a locally important groundwater resource that underlies the Tuhala karst area famous for an intermittently overflowing karst spring known as the Witch's Well. The water rich in humic substances of the Tuhala River recharges the Tuhala karst system, which is drained by two spring groups. In order to develop measures for the sustainable management of the aquifer in the future, the aim of this study was to enhance understanding of the hydraulic behaviour and hydrodynamic properties of the Tuhala karst system. From October 2014 to December 2016 an extensive field campaign was carried out comprising the observation of 22 surface-and groundwater monitoring points for water level and physico-chemical parameters and the performance of four quantitative tracer tests. The data obtained were evaluated in accordance with the input-output water level relation curves and a conceptual model of the system was set up. The results show that a strong hydraulic link exists, primarily through well-developed conduits between the recharge and discharge area of the karst system. Depending on the hydrological conditions, groundwater flow direc-Izvleček UDK 556.34:551.44(474.2) Oliver Koit, Nataša Ravbar, Andres Marandi & Jaanus Terasmaa: Določanje mejnih vrednosti tristopenjskega hidravljičnega obnašanja pokritega plitvega karbonatnega vodonosnika (Tuhalski kras, severna Estonija) Kraški vodonosniki se pogosto obnašajo nelinearno, zato lahko z ugotavljanjem mejnih vrednosti v hidravličnem režimu zago-tovimo bistvene informacije o delovanju vodonosnika. To velja tudi za silurijsko-ordovicijski vodonosni sistem v Estoniji, ki ga sestavljajo različne karbonatne kamnine in je pomemben vir pitne vode na severu države. Vključuje tudi vodonosnik Naba-la-Rakvere, ki je lokalno pomemben vodni vir. Na tem območju se nahaja Tuhalski kras, ki je znan po občasno bruhajočem kraškem izviru Witch's Well (čarovničin vodnjak). Tuhalski vodonosnik napaja reka Tuhala, bogata z huminskimi snovmi, prazni pa se skozi dve skupini izvirov. Da bi v prihodnje raz-vili ukrepe za trajnostno upravljanje vodonosnika, je bil namen te raziskave izboljšati razumevanje hidravličnega obnašanja in hidrodinamičnih lastnosti kraškega sistema. Od oktobra 2014 do decembra 2016 smo opravili obsežno terensko delo, ki je obsegalo spremljanje vodostajev in fizikalno-kemijskih parametrov v 23 površinskih in podzemnih točkah ter izve...

The isotopic investigations of groundwaters stored in the Rogaška Slatina fractured aquifer system were performed in the periods 1978-1985 and 2007-2011 aiming at answering open questions on the groundwater recharge and dynamics, on connections between different types of aquifers and on solute transport. Environmental isotopes 2 H, 18 O, 3 H, 13 C of dissolved inorganic carbon and 14 C were analysed in mineral, thermo-mineral and spring waters. Results indicated the source and mechanism of groundwater recharge, its renewability, a transit time distribution, hydraulic interrelationships, the groundwater origin and its evolution due to effects of waterrock interaction. They proved the hypothesis that the Boča massif should be a catchment area of the Rogaška mineral waters. The estimates of the mean residence time of mineral waters in the aquifer system are between 7200 and 3400 years, depending on the location and depth. Thermo-mineral water is the oldest water in the study area with the mean residence time of 14000 years. V obdobjih 1978-1985 in 2007-2011 so bile izvedene izotopske raziskave podzemne vode, uskladiščene v razpoklinskem vodonosnem sistemu na območju Rogaške Slatine, z namenom, da se odgovori na odprta vprašanja o napajanju podzemne vode in njeni dinamiki, o povezavi različnih vrst vodonosnikov in o prenosu snovi. V mineralnih, termomineralnih in izvirskih vodah smo analizirali 2 H, 18 O, 3 H, 13 C v raztopljenem anorganskem ogljiku in 14 C. V rezultatih smo opisali vire in mehanizme napajanja podzemne vode, njeno obnovljivost, zadrževalni čas v vodonosniku, izvor in geokemijski razvoj zaradi reakcij s kamninami. Potrdili smo hipotezo, da je masiv Boč napajalno območje Rogaških mineralnih vod, ki se zadržujejo v vodonosniku s povprečnim zadrževalnim časom od 7200 do 3400 let. Le ta je odvisen od lokacije in globine. Termomineralna voda je starejša -njen povprečen zadrževalni čas je 14000 let. Izvleček

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Kratka vsebinaNa obmo~ju vodnega telesa Pivovarne Union se je za~el izvajati leta 2003 ob{iren {tudij toka podzemne vode in prenosa snovi, katerega namen je, da se a) dolo~i in napove {irjenje podzemne vode in urbanega onesna'enja skozi pleistocenski aluvialni prodni vodonosnik ter b) analizira tveganje prenosa onesna'enja do vira pitne vode v spodnjem prodnem vodonosniku. Prvi dve raziskovalni fazi sta temeljili na izotopskih raziskavah. V 16 opazovalnih vrtinah se je vzpostavil monitoring sestave stabinih izotopov δ 18 O in δ 2 H ter osnovih fizikalno-kemi~nih parametrov vode. Rezultati so omogo~ili vpogled v hidrodinamiko opazovanega vodonosnika, pa tudi v starostno strukturo vzor~enih vod. Identificirana je bil vertikalna komponenta toka, ki je glavni faktor za prenos in {irjenje onesna'enja do podzemnega vira pitne vode. AbstractA study of groundwater flow and solute transport commenced in the area of the Union Brewery water body in 2003 with the intention of a) assessing and predicting the movement of groundwater and urban contaminants through the Pleistocene alluvial gravel aquifer and of b) analysing the risk of contaminat transport to drinking-water resources in the lower gravel aquifer. The first two research phases based on isotopic researches. The monitoring of groundwater composition of δ 18 O in δ 2 H stable isotopes and basic physicochemical parameters was established in 16 observation wells. The results have produced general information on the hydrodynamic functioning of the study area and they provided, an insight into age structure of sampled water. The vertical flow component was identified, which is the main influence on contaminant transport towards the drinking-water resource. UvodPodzemna voda pleistocenskega aluvialnega prodnega vodonosnika je vse pomebnej{i vir pitne vode za obmo~je mesta Ljubljane. Ta vodni vir je neprecenljiv tudi za Pivovarno Union d.d., ki le'i v urbanem in industrijskem okolju, v neposredni bli'ini centra Ljubljane. Pivovarna izkori{~a s {ti-rimi produkcijskimi vodnjaki kvalitetno podzemnov vodo spodnjega pleistocenkega prodnega vodonosnika in jo uporablja za proizvodnjo ustekleni~ene vode, brezalkoholnih pija~ in piva. Omenjeni vodonosnik je lo~en z neprepustno bariero od zgornjega prodnega vodonosnika, za katerega pa so dosedanje raziskave pokazale, da je onesna-'en tako mikrobiolo{ko kot kemi~no. Dose-