Question

An average family of four uses roughly 1200 liters (300 gallons) of water per day. (One liter = 1000 cm^3.) How much depth would a lake lose per year if it uniformly covered an area of 50 square kilometers and supplied a local town with a population of 40,000 people? Consider only population uses, and neglect evaporation and so on.

Answer 1

Assume 40,000 people use the same amount as 10,000 families of 4. The total water use per day will be 1200*10^4 = 1.2*10^7 liters = 1.2*10^4 m^3. Per year that is V = 4.38*10^6 m^3.

The drop in water level per year is V/A, where A is the area of the lake, 50*10^6 m^3.

Answer 2

So, would that make it 8.76*10^-2? If so, what would the units be?

Answer 3

Yes, in meters. That's about 3 1/2 inches