The drinking water in Boston comes from the Quabbin Reservoir. The water is pumped across Massachusetts to provide clean drinking water to the population of Boston.
Assume the average precipitation in New England is 130cm/year and that the volume of the Reservoir is 1.5x10^12 liters. Assume the watershed draining into the Quabbin has an area of 100km^2.
What is the residence time of water in the Reservoir with respect to rain? Please show your calculation and explain all your assumptions.


This is an equation I have been given and I have no earthly idea where to start...

What do I do to start this equation?


Thanks.

You'll want to convert to some like units. I would suggest cm^2 for area which is currently km^2, and mL for the basin volume which is in L. This is because cm^3 = mL.

Multiply the Rainfall per year by the area of the watershed. (cm^3/yr)

Then divide the basin volume by the product in the first step to get your answer in years. (mL and cm^3 will cancel)




In reality, this is missing some information like flow rates and evaporation/usage rates. But I assume it's meant to be simple based on the given information.

This post was edited by timmayX on Oct 3 2017 02:29pm

Thanks! I did all of the conversions and just started to plug n play.
The Residence time came out to 11.5 years!