Table 4. Mean Averages and Standard Deviations of 3H-3He and Sulfur Hexafluoride (SF6) Water Ages and Corresponding Residence Times for Different Depth Regions in Lake Vana


	3H-3He: 1990	3H-3He: 2005	SF6: 2005

Mean water age Above 100 m	2 +/- 2	5 +/- 4	5 +/- 3
Mean water age Below 325 m	10 +/- 0.5	22 +/- 3	22 +/- 1
Mean residence time below 325 m	8 +/- 2	17 +/- 5	17 +/- 3

aFor 3H-3He water ages we used (3He/4He)ter = 5 x 10-6 to obtain agreement between SF6 and 3H-3He water ages.