6.3.2. Results of the Hubelj - Mrzlek- Podroteja Area (M. ZUPAN, B. REICHERT) 6.3.2.1. First Tracing Experiment in October 1993 Uranine injected in the ice cave Belo Brezno was detected in the springs Hubelj, Lijak and Mrzlek after the heavy rain events from October 21 till October 25, 1993 (compare Chapter 6.2.1). The uranine breakthrough curves for the three karst springs are given in Fig. 6.6, 6.7 and 6.8. Tab. 6.8 presents an overview of the relevant curve parameters. 0,200 0,180 •5 ^ 0,160 o I 0.140 ? E. 0,120 2 oT 0,100 § i 0,080 ß i 0.060 0,040 0,020 0,000 San^iing poirt: HLBEU 14.10.93-23.3.04 T 35 i 30 I 25 T 20 I 15 T 10 T 5 J. o £ O 8 ■«r Time (h) uranit« Fig. 6.6: Results of the first tracing experiment, Oct 1993: Breakthrough of uranine in the Hubelj spring and the discharge of the Hubelj during the observation period of 3900 hours. Samplit^ poirt: LIJAK 13.10.93-23.3.94 0,300 •5 ^ 0,250 -.1 "B) 0,200 If 0,150- § I 0,100 o 2 O 3 0,050 -0.000 o o o o .. . _ s 8 8 ? t- T- OJ CM Time (h) uranine i END OF iSAlVPUNG O O O ....... 14 - 12 + 10 I 8 4 6 - 4 - 2 ■ O i o Sampling polt«: MRZLEK Pump station, 14.10.93-16.2.94 1 EN0C3F 1 SAMPLING , / — I , ■■ ' r- i - n -i - 1 -■ 1 -^r ^ - 8 (M Time (h) prec Lokve Fig. 6.8: Results of the first tracing experiment, Oct 1993: Breakthrough curve of uranine in the Mrzlek spring (sampling in the pumping station) during the observation period of 3900 hours. Hence the spring is situated in the Soča river no discharge measurements are available. To describe the hydrologic situation the daily precipitation heights of the station Lokve is depicted. Tab. 6.8: Overview of relevant parameters derived from the uranine breakthrough curves in the springs Hubelj, Mrzlek and Lijak in the first tracer test, Oct 14, 1993: time (t^^ J, concentration (C) and velocity (v^^^J of the first appearance, time of maximal concentration (t ), maximal concentration (C ) and dominant ^ inax" ^ max' velocity (v^^J in the springs and the recovery (R). Spring C [mg/m ^max [h] Vmax [m/h] ^raax [mg/m tdom [h] Vdom [m/h] R [kg] R [%] Hubelj 0.0300 196 35.1 0.1850 234 29.4 0.107 2.14 Mrzlek pumping station 0.3850 216 92.4 0.3850 216 92.4 2.0 (1.45) * 40 (29)* Lijak 0.0009 214 63.0 0.2570 238 56.6 0.507 10.10 Hotešk 0.0027 309 67.9 0.0027 309 67.9 -1) 2.00 = recoveiy rate for the Mrzlek estimated on the basis of Q„e», for 1961 to 1990 (1.45)*-recovery rate for the Mrzlek estimated on the basis ofQ„„, for 1993 to 1995 * 1) = only a singular peak, no recovery estimation Hence the spring Lijak is only temporarily active (compare Chapter 2.6.2) in the framework of former investigations a borehole was drilled nearby to enable a regular monitoring of the karst groundwater. The regular sampling during the tracing experiment for the sampling point Lijak was not in the spring itself but in this nearby borehole. Only for the long-term investigation direct samples of spring were analysed. The comparison of the results is striking, but so far explainable. The concentrations in the spring samples were definitely higher than in the borehole samples at the approximately the same time (Tab. 6.9). Tab. 6.9: Comparison of the uranine concentrations in the Lijak spring and Lijak borehole Uranine - mg/m'' Date / hour Lijak borehole Lijak spring 28.10.93 / 11:30 0.065 28.10.93 / 10:00 0.112 23.12.93 / 10:45 udl 23.12.93 / 13:00 0.088 19.01.94 / 11:30 udl 19.01.94/ 13:00 0.054 udl = under detection limit Uranine was not detected in the samples taken from the smaller karst springs Skuk and Gorenje in the vicinity of the Hubelj spring. In the spring Hotešk only one singular uranine peak with a very low concentration (0.0027 mg/m') was detected in the sample taken on October 27, 1993. This peak should nut be overemphasised; it might represent a background value which ranges up to 0.006 mg/m^ (compare Chapter 6.3.4) 6.3.2.2, The Second Tracing Expeximent in April 1994 Uranine The repeated injection of uranine in the injection point Belo Brezno in spring 1994 resulted in uranine breakthrough in the springs Hubelj and Mrzlek, but astonishingly not in the spring Lijak (Fig. 6.9 and 6.10). Compared to the first tracing experiment a distinct delay of the breakthrough of the maximal uranine concentration occurred (Tab. 6.10). On the other hand uranine appeared earlier for the first time than in the first tracing experiment. It has to be taken into account that the appearance of uranine in two samples taken on April, 19, 1993, and April, 20, 1993, could possible originate from the first tracing experiment. In comparison with the first tracing experiment the maximal concentrations were much lower in the Hubelj, but higher in the Mrzlek (Tab. 6.10). Sampling prtrt: HUBEU 18.4.-29.7. 0,018 r 0,016- f 0,014 j 0,012 1 —0,010 -§0,008 -10,006 = 0,004 0,002 T 0,000 Time (h) urmikie Fig. 6.9: Results of the second tracing experiment, April 1994: Breakthrough of uranine in the Hubelj spring and the discharge of the Hubelj during the observation period of 2500 hours. Sanpling point: MRZLBKPua^Jstetion 16.4.-29.7.1994 u 0,600 0,500 0,400 0,300 --0,200 0,100 0,000 i- Tab. 6.10: Overview of relevant parameters derived from the uranine breakthrough curves in the springs Hubelj and Mrzlek in the second tracer test, April 16, 1994: time(t^^^J, concentration (C) and velocity (v^^^J of the first appearance, time of maximal concentration (t^^J, maximal concentration (C^^J and dominant velocity (^do,J springs and the recovery (R). Spring C [mg/m tmax [h] ^max [m/h] Cmax [mg/m tdom [h] Vdom [m/h] R [kg] R [%] Hubelj 0.0085 70 98.2 0.017 414 16.6 0.001 0.02 Mrzlek pumping station 0.0009 168 119 0.579 318 62.8 2.98 (2.15) * 59.6 (43)* 2.98 = recovery rate for the Mrzlek estimated on the basis of for 1961 to 1990 (2.15)* = recoveiy rate for the Mrzlek estimated on the basis of for 1993 to 1995 Pyranine Pyranine, injected in the doline Mrzli Log, was detected in the samples of the karst spring Podroteja and Divje Jezero (Fig. 6.1). While in the spring Podroteja an almost classical pyranine breakthrough curve was observed, only one single pyranine peak occurred, with a much lower concentration in the Divje Jezero (Fig. 6.11). An overview on the determined values gives Tab. 6.11. Sampling point; PODROTEJA and DIVJE JEZERO 16.4.-29.7.1994, 0,160 0,140 -•S"^ 0,120 --" 1 0,100 - 0,080 0,060 , 5 0,040 " 0,020 -0,000 Time (h) Tab. 6.11: Overview of relevant parameters derived from the pyranine breakthrough in the springs Podroteja and Divje Jezero in the second tracer test, April 16, 1994: time(t^^^J, concentration (C) and velocity (v^^^J of the first appearance, time of maximal concentration (t^^^J, maximal concentration and dominant velocity (v, J in the springs and the recovery (R). Spring C [mg/m tmax [h] ^max [m/h] Cmax [mg/m tdom [h] ^dom [m/h] R [kg] R [%] Podroteja 0.0507 309 24.7 0.1579 380 20.1 Divje jezero 0.0870 822 9.2 0.0870 822 9.2 6.3.2.3, Third Tracing Experiment in August 1995 Uranine This tracing experiment was realised at low water conditions (compare Chapter 6.2.3) and the results are quite different from the previous ones. In the Hubelj the first appearance and the maximal concentration of uranine were reached earlier compared to first two tracing experiments. While in the first period of the observation time a continuously breakthrough occurred, later only single samples were uranine positive. At all the uranine concentrations Sampling pdrt: HUBEU 1.8.95-15.11.96 0.012 "5 ^ 0,010 I" 0,008 v 0,006 1 O'O®* 3 0,002 0,000 EM5 0F / SAMPLING I/ -- i -T-i !-1-i-i------! j i 1 1........... t------1--!-1-1-T 11 25 20 15, 10 5 0 Time (h) uranine were low (Fig. 6.12). Contrary to the Hubelj the first appearance and the maximal uranine concentration in the Mrzlek pump station was reached much later (Tab. 6.12). While for the first and the second experiment only water samples from the Mrzlek pumping station were available, both, the pumping station and the spring in the Soča river were sampled for the third experiment. The comparison of the result proved the assumption that the karstic flow was practically the same in both samphng points (Fig. 6.13 and 6.14). Sampling potrt: MRZLEK Pump station, 1.8.95-4.1.96 0,250 I "S 0,200 §i 1 I § .| 0,100 o 1 0,050 0,000 Fig. 6.13: Results of the third tracing experiment, August 1995: Uranine breakthrough curve in the Mrzlek pumping station. Tab. 6.12: Overview of relevant parameters derived from the uranine breakthrough in the springs Hubelj and Mrzlek (for both the pumping station and the spring in the Soča river) in the third tracer test, August 1, 1995: time{t^^^J, concentration (C) and velocity (v^^J of the first appearance, time of maximal concentration (t^^^^J, maximal concentration (C^^^J and dominant velocity (v^^J in the springs and the recovery (R). Spring C [mg/m tmax [hi Vmax [m/h] r [mg/m tdom [h] Vdom [m/h] R [kg] R [%] Hubelj 0.0019 144 47.7 0.0107 180 38.2 0.0008 0.01 Mrzlek pumping station 0.0028 804 24.6 0.2042 888 22.3 4.6 (3.2)* 66 (45.7) * Mrzlek Spring 0.0010 798 24.8 0.2057 887 22.3 5.05 (3.6)* 72 (51.4) * 4.6 = recovery rate for the Mrzlek estimated on the basis of Q„c„ for 1961 to 1990 (3.2)» = recovery rate for the Mrzlek estimated on the basis of Q„j„ for 1993 to 1995 The Lijak spring was only active for a short period of time. Only two water samples taken on August 28, 1995, and September, 19, 1995 were analysed. The latter had an uranine concentration of 0.023 mg/m-\ Unfortunately no sampling in the borehole was possible due to technical reasons. Pyranine Pyranine injected in the doline Malo Polje was detected in the karst springs Podroteja and Divje Jezero (Fig. 6.1). Unfortunately, the pyranine breakthrough took place just in the time period when samples got lost for those two sampling points. Therefore only 5 samples for a time period of in 9 days are available. Despite the missing samples the concentration curves look like a periodical content of the tracer (Fig. 6.15, Fig. 6.16) Compared to the second experiment by high water conditions the time of first appearance and of maximal concentration in Podroteja was longer as expected by prevailing low water conditions. A direct comparison to the single peak characterising the pyranine breakthrough in spring 1994 is not possible. (Tab. 6.13) Sampling point: PODROTEJA 1,8,95-15.11.95 0,020 0,018 t ■S^c 0.016 I g I 0,014 r 1 § 0,012 ! t g 0,010 " " 0,008 i 0,006 -0,004 -0,002 -0,000 — i I o S. i o o o § g 8 8 i CM ^ Time (h) o o CO o 8 CM O O CM CM O O O O ■ 0,1 0 ^pr 94) ft j ^ ' fd iJOj 1 \ A 3(4ugö5) - - ^^, ^ i-- 25 50 75 time after inaction [d] 0,6 0.5 0,4 cn E 0,3 OH 3 0,2 in o> 0,1 0 100 0,200 <5-0,150 Ol -0,100 CO ^ 0,050 0,000 (Oct 93) i sjAug 95) I ■ ......... i i <2 Api j 94) 1 i j i jl... M/V^i 0,020 0,015 "a E, 0,010 a ih ro 0,005 S 0,000 25 50 75 time after injection [d] 100 Fig. 6.19: Comparison of the uranine breakthrough in the Hubelj spring for the three repeated injections in the ice cave Belo Brezno in 1993, 1994 and 1995. The ice cave Belo Brezno, the injection point for repeated uranine tracing under different hydrologic conditions in the central part of the Trnovski Gozd plateau, is developed in the limestones of the Trnovo nappe. Following the general SW dip of the Uppertriassic, Jurassic and Cretaceous carbonate rocks of the Trnovo nappe, directed by the mainly NW-SE striking strike slip faults main reoccurrence of the tracer injected in Belo Brezno is the karst spring Mrzlek at the deepest regional base level of the karst groundwater. During all hydrologic situations tested the Mrzlek spring was the main outlet. A direct comparison of the breakthrough curves resulting from the three uranine injections in experiments is given in Figs. 6.18 and 6.19. Caused by the flooding of the spring outlet by the Soča river due to the construction of the Solkan hydropower plant, no current discharge measurements are available. Based on a mean discharge calculated from existing long-term observations from 1960 to 1990 the recovery was roughly estimated.