Značilnosti kanalskega in razpoklinskega toka izvira Pinarbaşi, Centralni Taurus, Seydişehir, Turčija

This study was conducted to investigate the flow and storage mechanisms of a karst aquifer located at the central Taurus Mountains, Turkey. As the biggest discharge point of the aquifer system, the flow characteristics are investigated at Pinarbaşi spring by using recession and time-series analyses. Continuous water level measurements are taken from the spring and are converted to flow rate by using a rating curve. The spring flows for 7 months (December 2014 – July 2015) and dries up for the rest of the year. Six individual recession periods are investigated and analyzed in the discharge time series. The recession coefficients (between 0.029 day-1 and 0.695 day-1) show that the flow within the aquifer system is mainly controlled by large open conduit and partly fracture porosity. The peak discharge is measured as 7.08 m3/s, and the maximum storage within the aquifer is calculated as 3.15 million m3. The continuous discharge data of the spring were evaluated combined with daily rainfall, temperature, electrical conductivity, and amount of suspended sediment in the water. Also a dye-tracing test was also applied to obtain the recharge-discharge relationship and porosity type of the aquifer system. Statistical tests on discharge hydrograph and tracer test showed that the memory of the karst aquifer was found to be about 3 days in the DJF period and about 15 days in the MAM period. The average elevation of the recharge area of the spring was determined to be 1,490 m by using stable isotope data of snow samples and was validated by dye tracer test made via the swallow hole in the recharge area. The total discharge for the year 2015 is estimated at 16.2 million m3 that approximately 25% of the total discharge is caused by snowmelt.Raziskovali smo dinamiko toka in skladiščenja v kraškem vodonosnika v Centralnem Taurusu v Turčiji. Z recesijsko analizo in analizo časovnih vrst pretoka smo raziskovali značilnosti največjega izvira vodonosnika, izvira Pinarbaşi. Časovno vrsto pretoka smo izračunali iz podatkov zveznih meritev nivoja in pretočne krivulje. Izvir je bil aktiven med decembrom 2014 in julijem 2015, preostali del leta je bil suh. Analizirali šest recesijskih obdobij. Koeficienti recesije, ki so med 0.029 dan-1 in 0,695 dan-1, kažejo na kanalsko in razpoklinsko poroznost. Največji izmerjeni pretok je bil 7,08 m3/s, največji izračunani volumen uskladiščene vode pa 3,15 milijona m3. Z analizo časovnih vrst smo raziskovali korelacijo med pretokom ter padavinami, temperaturo, električno prevodnostjo in motnostjo. Polnjenje in praznjenje ter strukturo vodonosnika smo določali tudi z sledilnim poskusom. Statistična analiza in rezultati sledenja so pokazali, da je spominski čas vodonosnika 3 dni v obdobju od decembra do februarja in 15 dni v obdobju od marca do maja. Z analizo stabilnih izotopov v vzorcih snega smo ugotovili, da je povprečna nadmorska višina prispevnega območja 1490 m. To potrjuje tudi sledilni poskus z vnosom sledila v enega od ponorov, ki jih najdemo na tej nadmorski višini. Celoten odtok izvira v letu 2015 ocenjujemo na 16,2 milijona m3, pri čemer je približno 25 % prispevalo taljenje snega

Revealing the positive influence of young water fractions derived from stable isotopes on the robustness of karst water resources predictions

Introducing additional information sources, such as hydrochemical signatures and water isotopes, into the model calibration has shown to be useful to enhance model robustness by increasing parameter identifiability and maintaining simulation reliability. Our study explores the added value of discharge young water fractions (Fyw, derived from the volume-weighted δ18O concentrations) on the model reliability as a calibration constraint. For this, we coupled a karst hydrological model (VarKarst) with a catchment-scale transport model (StorAge Selection (SAS) function approach) to simulate discharge δ18O concentration (δ18OQ) and corresponding Fyw. We performed a multi-variable calibration scheme by simultaneously constraining a large model ensemble (1x106 realizations) with respect to the model performance on discharge and Fyw. By searching a model output space in which the model performance on discharge and model performance on Fyw provides an optimal trade-off, we extracted hydrologically more informative model realizations. We tested our calibration approach at the Wasseralm spring, which supplies drinking water to the city of Vienna, Austria. The contribution of the information content of Fyw to the model robustness was assessed by the degree of reduction in the parameter and simulation uncertainties. Our results indicate that the inclusion of Fyw notably reduced the uncertainty in model parameters (6 parameters out of 8), simulations (14 % vs. 10 % by δ18OQ), and water balance components for the model internal states (around 40 %). Our findings reveal that Fyw confirms the model reliability (KGE: 0.71 ± 0.01 in validation) in that it mainly reduces the parameter equifinality by providing physically more plausible and identifiable parameter sets. Therefore, Fyw is a potentially useful metric to better constrain the model outputs, thereby limiting the model uncertainty