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Name 2.) Water Cycle a.) The drinking water in Boston comes from the Quabbin Res

ID: 113695 • Letter: N

Question

Name 2.) Water Cycle a.) 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 pr he 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? Please show your calculation and explain all your assumptions. (5 points) b.) Why does the Quabbin not dry up even 30 days after the last rain? (3 points) c) How does protecting the Quabbin Watershed ensure good drinking water quality? (2 points)

Explanation / Answer

a) Given, Precipitation = 130 cm/year

Reservoir volume = 1.5 * 1012 litre = 1.5 km3

Watershed area = 100 km2

Residence time = amount of water in the reservoir / rate of addition or loss of water

Amount of water in the reservoir = Volume/ area

= 1.5 km3 / 100 km2

= 1.5 * 10 -2 km

= 1.5 * 103 cm

So, residence time = (1.5 * 103 ) / 130

= 11.53 year

b) The Quabbin does not dry up even 30 days after the last rain because water level does not fall below the normal operating range of 85% when the reservoir exceeds its capacity ( 412 billion gallon ).

c) The Quabbin watershed ensures good drinking water quality by ' Watershed Protecting Plan '. This plan checks the details for the tributaries and the reservoir for the bacteria, nutrients, turbidity, algae and hydrogen ion activity.