An average family of four uses roughly 1200 liters of water per day. In the town of Bonk- Population 40,000- drinking water is provided from a lake that covers an area of 50 square kilometers.
A). In a clear, coherent, paragraph length explanation, describe how you would figure out how much depth the lake loses each year due to the town's usage. Be sure you are thorough in your explanation.
B). Using the method described above in A, calculate the depth the lake loses each year due to the town's usage.
C). Describe as you would to a non-physicist how much land area this lake covers compared to land references with which you are familiar with such as a football field. Justify your answer.
If a family of four uses roughly 1200 liters of water a day, then a town with population of 40,000 (that is, 10,000 families), uses `1200*10,000 = 12,000,000` liters of water a day.
To calculate how much depth the lake, which is the town's source of water, will lose due to the town's usage, we first need to convert liters to cubic meters. One liter equals to 1 cubic decimeter, which is one tenth of a meter. Therefore,
1 liter is one tenth cubed, or one thousandth, of a cubic meter. To find the volume of water used per day in cubic meters, divide 12,000,000 by 1000:
12,000,000/1000 = 12,000 cubic meters.
The volume of water used by the town in one year can be calculated by multiplying 12,000 by the number of days in a year, 365:
12,000*365 = 4,380,000 cubic meters, or roughly 4,500,000 cubic meters.
The depth lost every year will be the volume of water used divided by the area of the lake. Since the area of the lake is 50 square kilometers, or 50,000,000 square meters, the depth lost every year will be
4,500,000/50,000,000 = 0.09 meters, or 9 centimeters. This is about 3.5 inches.
The town loses about 9 centimeters, or 3.5 inches, of the depth of the lake per year.
C) To understand how much land this lake covers, consider a city block 200 meters long and 100 meters wide. This city block will have the area of 20,000 square meters. The lake will cover the area equal to 50,000,000/20,000 = 2500, or twenty five hundred city blocks.