The drinking water in Boston comes from the Quabbin Reservoir. This water is pumped across Massachusetts to provide clean drinking water to the population of Boston. Assume the average precipitation in New England is 130 cm/year and that the volume of the Reservoir is 1.5 x 1012 liters. Assume the watershed draining into the Quabbin has an area of 100 km2. What is the residence time of water in the Reservoir with respect to rain?