In this issue of Math in the News we look at the ongoing drought in California. In the process we look at the percent change in the current level of water in reservoirs relative to the average level.

1. MATH IN THE NEWS
Issue 96
The California Drought

2. THE CALIFORNIA DROUGHT
 The year 2013 was the driest year on record since 1894,
and conditions have only continued to worsen in 2014.
This follows several years of dry winters in California,
raising concerns about overall water trends.

3. THE CALIFORNIA DROUGHT
Residents of California have had to restrict their water
usage as a way to conserve the limited amount of water
available. People have been advised to limit watering
plants and grass, and be mindful of water usage in daily
tasks (brushing teeth, taking showers, and doing
laundry). (SaveOurH20, www.saveourh2o.org)

4. THE CALIFORNIA DROUGHT
Californians
have also
suffered from
record wildfires
due to the
extremely arid
conditions. (The
Atlantic)

5. THE CALIFORNIA DROUGHT
 The effects of the drought reach throughout
the United States, as we rely on California
agriculture for almost half of the nation’s
supply of fruits, vegetables, and nuts.

6. THE CALIFORNIA DROUGHT
This map shows the
severity of the
drought throughout
the state of
California.
(Source: United States
Drought Monitor)

7. THE CALIFORNIA DROUGHT
This table shows conditions throughout 2013. Conditions have
been consistently dry, but the severity has been increasing.
(Source, United States Drought Monitor)

8. THE CALIFORNIA DROUGHT
Water is stored in reservoirs.
Current water levels are
shown in the map. The
measurements are in acre-
feet, a unit of volume equal
to the volume of a sheet of
water one acre in area and
one foot in depth.
Source: California
Department of
Water Resources

9. THE CALIFORNIA DROUGHT
With this information, we can
assess the differences between
current water levels and average
water levels, and current water
levels and capacity.

10. THE CALIFORNIA DROUGHT
Transfer information from the map to a chart.
Name of Reservoir
Capacity
(acre-feet)
Average percent
filled
Current percent
filled
Trinity Lake 2,447,650 68% 53%
Lake Shasta 4,552,000 58% 46%
Lake Oroville 3,537,577 61% 46%
New Melones 2,400,000 69% 43%
Folsom Lake 975,000 67% 42%
San Luis 2,041,000 47% 42%
Don Pedro 2,030,000 73% 53%
Millerton Lake 520,500 46% 32%
Pyramid Lake 180,000 103% 94%
Castaic Lake 325,000 94% 84%
Exchequer 1,032,000 42% 23%
Pine Flat 1,000,000 39% 22%
Note how great the difference
is between this year and the
average!

11. THE CALIFORNIA DROUGHT
What is the average amount of
acre-feet of water in each
reservoir at this time of year?

12. THE CALIFORNIA DROUGHT

13. THE CALIFORNIA DROUGHT
Name of Reservoir
Capacity
(in acre-feet)
Average percent
filled
Average acre-feet
filled
Trinity Lake 2,447,650 68% 1,664,402
Lake Shasta 4,552,000 58% 2,640,160
Lake Oroville 3,537,577 61% 2,157,921.97
New Melones 2,400,000 69% 1,656,000
Folsom Lake 975,000 67% 653,250
San Luis 2,041,000 47% 959,270
Don Pedro 2,030,000 73% 1,481,900
Millerton Lake 520,500 46% 239,430
Pyramid Lake 180,000 103% 185,400
Castaic Lake 325,000 94% 305,500
Exchequer 1,032,000 42% 433,440
Pine Flat 1,000,000 39% 390,000
Ex: 1,000,000 x (0.39) = 390,000

14. THE CALIFORNIA DROUGHT
How many acre-feet of water are
currently in the reservoirs?

15. THE CALIFORNIA DROUGHT

16. THE CALIFORNIA DROUGHT
Name of
Reservoir
Capacity (in
acre-feet)
Average
percent filled
Average acre-
feet filled
Current percent
filled
Current acre-
feet filled
Trinity Lake 2,447,650 68% 1,664,402 53% 1,297,254.50
Lake Shasta 4,552,000 58% 2,640,160 46% 2,640,160
Lake Oroville 3,537,577 61% 2,157,921.97 46% 2,157,921.97
New Melones 2,400,000 69% 1,656,000 43% 1,032,000
Folsom Lake 975,000 67% 653,250 42% 409,500
San Luis 2,041,000 47% 959,270 42% 857,220
Don Pedro 2,030,000 73% 1,481,900 53% 1,075,900
Millerton Lake 520,500 46% 239,430 32% 166,560
Pyramid Lake 180,000 103% 185,400 94% 173,900
Castaic Lake 325,000 94% 305,500 84% 273,000
Exchequer 1,032,000 42% 433,440 23% 237,360
Pine Flat 1,000,000 39% 390,000 22% 220,000
1,000,000 x (0.22) = 220,000

17. THE CALIFORNIA DROUGHT
How many fewer acre-feet of water are in each
reservoir than expected (average)? Let’s look at
Trinity Lake.
There are 367,147.50 fewer acre-feet of water than
the average.

18. THE CALIFORNIA DROUGHT
What percent of expected water levels is currently
filled?
The water levels in the Trinity Lake reservoir are
77.9% what is expected at this time of year.

19. THE CALIFORNIA DROUGHT
 Continue exploring the changes in water levels by
answering the following questions:
 How many fewer acre-feet of water are in the rest of the
reservoirs?
 What percent of the expected water levels in the reservoirs
is currently filled?
 How many more acre-feet of water, total, are expected at
this time of year compared with actual current acre-feet of
water?
 Investigate how the water is allocated and the effects the
shortage in water resources has on the state of California
and on the United States.