Water transit times and flow paths from two line injections of 3H and 36Cl in a microcatchment at Gårdsjön, Sweden

✍ Scribed by Lars Nyberg; Allan Rodhe; Kevin Bishop

• Book ID: 101283361
• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 247 KB
• Volume: 13
• Category: Article
• ISSN: 0885-6087
• DOI: 10.1002/(sici)1099-1085(19990815)13:11<1557::aid-hyp835>3.0.co;2-s

✦ Synopsis

To investigate groundwater transit times and ¯ow paths in shallow till soil, within an acidi®cation study at GaÊ rdsjoÈ n, Sweden, two line injections of 36 Cl and 3 H were made in groundwater during 1992. The ®rst injection in January, when the two tracers were injected at the same depth, gave tracer transit times from injection line to outlet of some hours due to a runo event on the ®rst day. The subsequent recession period left a considerable amount of tracer in the unsaturated zone, which had transit times that ranged from weeks to months. Tracer recovery at the outlet was 78% for 3 H and 47% for 36 Cl. Cl retention was indicated. The second injection in November, when 3 H was injected at 30 cm depth and 36 Cl at 60 cm depth, gave recoveries of 96% for 3 H and 83% for 36 Cl. Apart from an advective ¯ow-dependent tracer transport, very fast tracer pulses occurred. The velocities for those pulses were of the order of tens of metres per hour. Highest tracer concentrations were observed in the super®cial soil layers, which suggest that these layers were the dominant ¯ow paths.