Question

The water budget is defined by the amount of water going into a system and the amount of water exiting the system. A system has a positive change of total water when the amount of water entering the system exceeds the amount of water exiting the system. A system has a negative change of total water when the amount of water exiting the system exceeds the water entering the system. Use your knowledge of unit conversions to determine whether the following system has a positive change or a negative change of total water volume. Show your work and include in your answer the total volume of loss or gain in this system in cubic feet per year.

Answer 1

In order to determine if there is a positive change or negative change in the water volume of the lake, proceed as follow:

Convert 258,000 cubic feet to gallons:

`258,000ft^3\cdot\frac{7.48\text{gal}}{1ft^3}=1,929,840gal`

Now, consider as positive values the volume of water in the lake and the annual volume of precipitation, and as a negative value the annual colume of evaporation.

Then, you can write for the change in the total volume of water:

change = 1,929,840gal - 1,800,000gal

change = 129,840gal

Hence, the change in the volume of the water in the lake is positive