IRRIGATION AND DRAINAGE 157 



EXERCISE II. Irrigation in the United States. 



Materials. Books on irrigation; encyclopaedia and magazine articles 

 and Government bulletins dealing with this topic; also weather maps 

 of the United States. 



Procedure. Using such sources of information regarding irrigation 

 projects as are available in your institution, sketch on Weather Bureau 

 maps or similar outline maps of the United States, the location of the 

 principal irrigation projects of this country. 



EXERCISE III. Irrigation problems. 



1. What is an acre-inch? 



2. How many square feet are there in an acre? 



3. How many cubic feet of water are contained in one acre-inch? 



4. What is meant by a "second-foot?" 



5. What is the relation between a second-foot and a miner's inch? 



6. How many second-feet are delivered by a stream of fifty miner's 

 inches flowing for one hour? 



7. What relation is there between this and one acre-inch? 



8. Utilizing the answer to the above question, answer the following 

 questions: 



a. How many acre-inches will a stream of 50 miner's inches deliver 

 to 10 acres of ground in 24 hours? The volume of a circular reservoir 

 with perpendicular sides is ascertained according to the following 

 formula: 



V equals 7rr 2 H 

 TT equals 3.1416 

 r equals radius of circle 

 H equals Height 



b. How many cubic feet in a circular reservoir with a radius of 

 50 feet and a height of 10 feet? 



c. If a river has a flow of 1000 second-feet, how many acres will 

 it irrigate with five acre-inches of water during a period of thirty days? 



