36 
Modern Business Geography 
for the irrigation of parts of the dry West. It has also drained 
swamps and meadows to make them available for farming. Under 
the Reclamation Service of the Department of the Interior, more 
than thirty government projects have been started since 1902 for 
the reclamation of arid lands. - 
QUESTIONS, EXERCISES, AND PROBLEMS 
A. The effect of rainfall on agriculture in the United States. 
Ll. On an outline map of the United States shade the areas of (a) heavy (over 
50 inches), (b) medium (20 to 50 inches), and (c) light (under 20 inches) 
rainfall as shown in Figure 6. Pick out three localities and ask someone 
else in the class to tell why the rainfall is light, medium, or heavy there. 
Be ready to decide whether the answers are right or wrong. 
Land receiving less than 20 inches of rainfall is considered arid or semi- 
arid. Make a list of fifteen states that are wholly or partly in the arid 
or semi-arid belt. 
Name areas where the rainfall is 60 inches or more. Which of these are 
30 level that the land is too swampy for farming? (See Figure 22.) 
The total area of American farm land could be increased about one tenth 
if the 120,000 square miles of swampy lands were reclaimed by drainage. 
Compare the area of the swampy lands with the area of your state. 
Does Figure 22 show much waste land in your state? What kind? 
On the irrigation projects of the United States the average value of 
the crops per acre in 1919 was $63.60; the cropped area amounted to 
1,100,000 acres. How much wealth was thus added to the country that 
year because of the irrigation work of the United States Recla- 
mation Service? Locate three of the irrigation projects. 
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Figs. 20, 21. Note the wide range of temperatures in Alaska. Note also the great difference 
between winter and summer temperatures in the Yukon valley; there the July temperature is 
high enough for agriculture, and the summer days are long and sunny. But the growing season 
is too short for many crops. The southern coast has about the same winter temperature as 
the North Atlantic states, and almost the same summer temperature as the coast of Washington 
and Oregon, and the growing season is long enough for any of the temperate-region crops; but 
heavy summer rainfall limits agriculture.