Water supply in times of climate change—Tracer tests to identify the catchment area of an Alpine karst spring, Tyrol, Austria

Figures & data

Figure 1. Simplified geological map of the project area, modified after Schäffer et al. (2018) and Kogler (2018). Relief shading was taken from the Tyrolean Geographic Information System (2019). The continuous red line indicates the catchment area of the sink; dashed red lines mark possible extensions of the catchment relating to the Tuxbachquelle

Figure 2. Position plan of the measuring points for both tracer tests: light blue circles indicate springs; dark blue circles creeks. The map background was taken from the Tyrolean Geographic Information System (2019). Overview of the first and maximal uranine transit in the different measuring points during the tracer tests at low (Q_LOW) and high (Q_HIGH) runoff

Figure 3. Measured extinctions in the Tuxbach gorge during the first hours of the tracer test at low runoff

Table 1. Schedule for both tracer tests

	Preparation	Uranine intake	Direct monitoring	Indirect monitoring
Test at low runoff in 2016	4 to 8 September	8 September, 10:30 a.m., 160 g	8 to 14 September	14 September to 11 October
Test at high runoff in 2017	7 to 9 June	9 June, 9:35 a.m., 1.6 kg	9 to 13 June	14 to 29 June

Table 2. List of measuring points

Measuring point	Abbreviation	Position (UTM 32T)	Altitude (m)
Brunnhausquelle	BHQ	712653; 5225049	1,170
Dornauquelle 1	DQ-1	713642; 5224986	1,131
Dornauquelle 2	DQ-2	713566; 5225017	1,126
Grünbergquelle	GBQ	711849; 5224621	1,380
Grinbergbach—Upper section	GB-U	711859; 5224132	1,553
Grinbergbach—Middle section	GB-M	711850; 5224245	1,502
Grinbergbach—Lower section	GB-L	711931; 5224888	1,273
Goldbründl—Confluence	GO-C	713070; 5225538	897
Goldbründl—Spring	GO-S	713079; 5225494	916
Gamshüttenwegquelle 1	GQ-1	713217; 5225159	1,082
Gamshüttenwegquelle 2	GQ-2	713295; 5225092	1,101
Gamshüttenwegquelle 3	GQ-3	713227; 5225107	1,107
Lampnerquelle 1	LQ-1	713141; 5225259	1,055
Lampnerquelle 2	LQ-2	713170; 5225282	1,039
Quelle in der Seiche	QDS	713049; 5225431	990
Tuxbach—Gorge	TB-G	713066; 5225542	896
Tuxbach—Innerberg	TB-I	711920; 5225522	949
Tuxbachquelle	TQ-0 to TQ-12	713199; 5225543 713108; 5225560	894–901

Table 3. Qualitative classification of the activated carbon bags of the tracer test at low runoff

	Short-term activated carbon bags (days in September)					Long-term activated carbon bags
Measuring point	7–8	8–9	9–10	10–12	12–14	08/09–14/09	14/09–11/10
BHQ		−	−		−	−	−
DQ-1		−			−	−	+
DQ-2		−			−	−
GBQ		−		+	−	−	++
GB-U		−			−	−
GO-C	−	−	−	−	−	−
GQ-1	−			−	−	−
GQ-2		−	−	−	−	−	−
GQ-3		−	−	−	−	−
LQ-1		−	−		−	−	−
LQ-2		−	−	−	−	−	+
QDS	−	−	−	−	−	−	−
TB-I	−			−	−	−
TB-G	−		−	−	−	−	+
TQ-1	−	+	−	−	−	−	++
TQ-2	−	−	−	−	−	−	+
TQ-4	−	−	−	−	−	−
TQ-10	−	−	−			−

Note: − = no evidence; + = possible evidence of traces; ++ = strong evidence. Empty fields indicate no sample.

Table 4. Comparison of selected parameters of the measuring points within the Tuxbach gorge from 8 to 14 September 2016

Measuring point	Q (L/s)	T (°C)	pH	κ at 25°C (µS/cm)	Turbidity (FNU)
TQ-1	190–275	6.1–6.5	7.62–8.29	133–152	0.1–2.1
TQ-2	19	6.1–6.4	7.93–8.34	134–153	2.0–2.4
TQ-3	0.2–2.3	6.1–6.9	7.46–8.29	132–152	1.5–3.0
TQ-4	ca. 2	6.1–6.5	7.58–8.35	135–139	1.5–4.3
TQ-5	ca. 100	6.1–6.2	8.20	143	2.1–3.8
TQ-10	<0.05	6.4–6.8	8.21	145–155	4.1
GO-C	0.3–1.9	8.2–10.0	7.98–8.38	169–220	0.7–1.2
TB-G	3,000–3,500	10.5–13.2	8.34–8.39	304–338	250–410

Table 5. Comparison of selected parameters of the measuring points within the Tuxbach gorge from 7 to 29 June 2017

Measuring point	Q (L/s)	T (°C)	pH	κ at 25°C (µS/cm)	Turbidity (visual)
TQ-0	0–0.25	5,2	8.25	126	Clear
TQ-1	262–330	5.0–5.5	8.27–8.47	103–138	Clear to slightly muddy
TQ-3	ca. 15	5.0	8.25	112	Clear to slightly muddy
TQ-4		5.0–5.6	8.25–8.36	102–138	Clear to slightly muddy
TQ-5	ca. 110–115	5.0	8.25	112	Clear
TQ-6	ca. 0.25	5.0	8.29	111	Clear
TQ-9	ca. 4–5	4.9–5.4	8.17–8.38	104–138	Clear
TQ-10	ca. 25–30	4.9–5.2	8.16–8.38	104–138	Clear
TQ-11	ca. 44–50	5.0–5.3	8.07–8.31	104–138	Clear
TQ-12	ca. 3–10	4.9–5.3	8.14–8.33	104–138	Clear
GO-S	ca. 0.25–1,000	5.2–5.6	8.15–8.48	106–115	Clear
GO-C		6.1–6.6	8.11–8.20	115–144	Clear
TB-G	5,300–5,700	8.4–12.8	8.17–8.31	245–277	Heavily muddy

Figure 4. Measured extinctions during the tracer test at high runoff at selected measurement points in June 2017

Table 6. Qualitative classification of the activated carbon bags of the tracer test at high runoff

	Short-term activated carbon bags (days in June)					Long-term activated carbon bags  (days in June)
Measuring point	8–9	9–10	10–11	11–12	12–13	8–13	13–28
BHQ	−	−	−	−	−	−
DQ-1	−	−	−	−	−	+
DQ-2	−	−	−	−	−	−
GBQ	−	+	+	+	+	+	++
GB-U			−	()	−	−	()
GB-M		+++
GB-L		+++	+++	+++	+++	+++	()
GO-C	−	−	+	()	+	+	+++
GQ-1					−		+
GQ-2	−	−	−	−	−	−	+
GQ-3	−	−	−	−	−	−	−
LQ-1	−	−	−	−	−	−	−
LQ-2	−	−	−	−	−	−	+
QDS	−	−	−	−	−	−	+
TB-G	−	+	++	+	++	++	++
TQ-1	−	−	−	+	+	+	+
TQ-4	−	−	−	−	−	+	+++
TQ-9	−	−	−	−	+	+	++
TQ-10	−	−	−	+	+	+	+++
TQ-11	−	−	−	+	+	+	+++
TQ-12	−	−	−	+	+	+	+++

Note: − = no evidence; + = possible evidence of traces; ++ = strong evidence; +++ = certain evidence of uranine; () = damage or loss of samples due to floodwater or mudflow. Empty fields indicate no sample.

Figure 5. Water temperature, electrical conductivity, and quantitative estimated turbidity at the Tuxbachquelle (outlet TQ-1) in comparison to precipitation at Gamshütte. Important precipitation events are marked with a gray background

Figure 6. Water temperature, electrical conductivity, and estimated discharge based on photos at Goldbründl (measuring point GO-A) in comparison to precipitation at Gamshütte. Important precipitation events are marked with a gray background

Table A1. Chemical properties of Grinbergbach at low runoff compared to spring water at the beginning and end of the tracer test. Samples taken in September 2016

	Measuring point
	GB-U	GBQ	GBQ	BHQ	BHQ	QDS	QDS
Date	05/09	05/09	14/09	05/09	14/09	04/09	14/09
T (°C)	10.8	5.9	6.0	7.0	6.7	11.2	9.2
κ at 25°C (µS/cm)	76	51	52	114	115	246	252
pH	7.87	7.57	7.09	7.66	7.18	7.52	7.24
EH (mV)	304	348	335	337	314	299	333
O2 content (mg/L)	9	10	11	10	10	8	9
O2 saturation (%)	101	99	101	95	96	88	89
Q (L/s)	ca. 5	1.32	0.50	1.53	1.20	0.54	0.25
Na^+ (mg/L)	0.01	0.32	0.28	0.88	0.97	3.46	3.14
NH4^+ (mg/L)	<0.01	0.02	0.04	<0.01	<0.01	<0.01	<0.01
K^+ (mg/L)	0.44	0.76	0.73	1.20	1.21	2.57	2.44
Mg^2+ (mg/L)	2.05	0.88	0.85	2.30	2.32	4.31	4.32
Ca^2+ (mg/L)	12.8	8.65	8.75	19.3	19.5	44.5	44.8
Sr^2+ (mg/L)	<0.1	<0.1	<0.1	0.18	0.15	0.19	0.22
F^− (mg/L)	0.02	0.03	0.03	0.07	0.06	0.05	0.05
Cl^− (mg/L)	0.50	0.72	0.12	0.75	0.72	6.74	6.53
NO2^− (mg/L)	0.01	<0.01	< 0.01	0.01	<0.01	<0.01	<0.01
Br^− (mg/L)	0.09	0.08	0.06	0.13	0.11	0.37	0.21
NO3^− (mg/L)	0.98	1.89	1.78	1.69	3.57	7.81	7.52
PO4^3− (mg/L)	0.09	0.09	0.06	0.09	0.07	0.04	0.05
SO4^2− (mg/L)	1.82	2.46	2.50	5.11	5.11	3.32	3.43
HCO3^− (mg/L)	46.4	28.1	28.1	65.9	65.9	149	142
TDS (mg/L)	65.2	44.0	43.3	97.6	99.7	222	214
∆ ion balance (%)	−1.63	−5.16	−1.48	−1.31	−2.40	−1.42	3.32
Measuring point	GQ-2	GQ-2	GQ-3	GQ-3	LQ-1	LQ-1	LQ-2	LQ-2
Date	06/09	14/09	06/09	14/09	07/09	14/09	07/09	14/09
T (°C)	7.1	7.5	7.8	8.0	8.3	9.1	9.4	10.5
κ at 25°C (µS/cm)	122	127	145	147	133	137	82	86
pH	8.01	7.41	7.87	7.53	7.86	7.53	7.82	7.24
EH (mV)	307	315	316	311	347	314	366	307
O2 content (mg/L)	10	10	8	9	11	10	10	10
O2 saturation (%)	92	93	80	85	100	99	101	100
Q (L/s)	0.63	0.60	0.06	0.05	0.22	0.05	0.16	0.07
Na^+ (mg/L)	1.20	1.12	1.58	1.41	1.21	1.08	1.21	1.26
NH4^+ (mg/L)	<0.01	<0.01	0.01	0.02	<0.01	<0.01	0.02	<0.01
K^+ (mg/L)	1.30	1.47	1.59	1.64	1.46	1.47	1.09	1.09
Mg^2+ (mg/L)	2.05	2.50	4.31	4.45	2.82	2.77	2.10	2.25
Ca^2+ (mg/L)	21.5	22.2	22.2	22.8	23.1	23.8	11.8	12.8
Sr^2+ (mg/L)	0.22	0.21	0.30	0.29	0.13	<0.1	0.14	0.13
F^− (mg/L)	0.07	0.07	0.09	0.08	0.09	0.09	0.08	0.08
Cl^− (mg/L)	0.49	0.62	0.49	0.40	0.40	0.54	0.40	1.02
NO2^− (mg/L)	<0.01	<0.01	<0.01	<0.01	0.01	<0.01	<0.01	0.07
Br^− (mg/L)	0.11	0.11	0.12	0.17	<0.01	0.13	0.07	0.10
NO3^− (mg/L)	2.02	1.90	1.01	1.10	<0.01	1.03	2.02	2.21
PO4^3− (mg/L)	0.06	0.05	0.07	0.05	0.04	0.05	0.05	0.05
SO4^2− (mg/L)	5.40	5.74	8.47	8.72	5.24	5.37	5.21	5.75
HCO3^− (mg/L)	72.0	68.3	81.8	83.0	83.0	79.3	43.9	43.9
TDS (mg/L)	106	104	122	124	117	116	68.2	142
∆ ion balance (%)	−1.00	8.06	1.45	2.43	−0.61	3.26	−3.51	3.32
Measuring point	DQ-1	DQ-1	DQ-2	DQ-2	TQ-1	TQ-1	GO-C
Date	06/09	14/09	06/09	14/09	04/09	14/09	14/09
T (°C)	7.1	8.3	6.7	7.4	5.7	6.1	9.4
κ at 25°C (µS/cm)	128	125	124	141	137	152	220
pH	7.71	7.96	7.74	7.74	8.06	8.31	8.43
EH (mV)	278	392	287	311	272	354	346
O2 content (mg/L)	10	10	10	8	9	10	10
O2 saturation (%)	100	99	90	87	119	85	98
Q (L/s)	1.90	1.21	0.47	0.64	5.7	6.1	<0.1
Na^+ (mg/L)	1.12	1.07	1.03	1.15	0.78	0.95	2.15
NH4^+ (mg/L)	<0.01	<0.01	<0.01	0.04	0.02	<0.01	0.03
K^+ (mg/L)	1.21	1.21	1.22	1.27	0.81	0.78	1.56
Mg^2+ (mg/L)	1.59	1.71	1.90	1.92	3.19	3.43	4.19
Ca^2+ (mg/L)	23.3	24.3	22.0	22.4	21.7	23.6	34.6
Sr^2+ (mg/L)	0.21	0.18	0.07	0.20	0.08	0.11	0.11
F^− (mg/L)	0.06	0.06	0.06	0.07	0.06	0.08	0.07
Cl^− (mg/L)	0.39	0.68	0.81	0.62	0.75	1.15	3.95
NO2^− (mg/L)	<0.01	0.01	<0.01	<0.01	0.04	<0.01	0.01
Br^− (mg/L)	0.12	0.14	0.12	0.11	0.12	0.13	0.16
NO3^− (mg/L)	3.02	1.92	1.87	1.84	1.46	1.34	4.08
PO4^3− (mg/L)	0.08	0.06	0.08	0.05	0.09	0.05	0.08
SO4^2− (mg/L)	4.17	4.26	5.14	5.12	6.75	8.93	6.59
HCO3^− (mg/L)	73.2	78.1	75.7	67.1	73.2	73.2	115
TDS (mg/L)	108	110	114	102	109	114	172
∆ ion balance (%)	1.80	−5.57	0.68	8.01	0.91	5.34	0.32

Note: TDS = Total dissolved solids.

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