Question

The graph below shows the change in groundwater storage of several regions in the California Central Valley from 1962 to 2002.


Image courtesy of USGS

The bold dark blue line on the graph represents the change for the entire Central Valley groundwater system, which is the largest water reservoir in the state of California. The groundwater supply in this system was depleted by almost 60-million acre-feet in the 40 years represented by the graph.

Which of the following scenarios would best explain the drastic reduction in water resources shown by the graph?
A.
The California Central Valley region received record amounts of precipitation between 1962 and 2002.
B.
The human population of the Central Valley region of California almost doubled between 1962 and 2002.
C.
Many nonnative species of animals were introduced into the California Central Valley region between 1962 and 2002.
D.
The vegetation in the California Central Valley region changed from tropical to drought-resistant between 1962 and 2002.

Answer 1

The scenario that would best explain the drastic reduction in water resources shown by the graph is:

**B. The human population of the Central Valley region of California almost doubled between 1962 and 2002.**

An increase in human population typically leads to higher water demand for domestic use, agriculture, and industry, which can significantly contribute to the depletion of groundwater resources. The other options do not directly relate to the reduction of groundwater storage in the same way that population growth and increased water use would.