Soils 456  Final Exam Spring 2008

1.  A main line for the drip irrigation is schedule 40 3 inch pipe having a velocity of 5 ft/sec. The main line comes from an outlet 300 ft away.  The line was used to irrigate the sprinkler experiment in addition to a vegetable garden.    Explain what would happen in the line if the valve at the end of the line were closed quickly.   If the operating pressure of the system is 60 psi will the pipe burst from the surge pressure plus the operating pressure exceeding the design pressure of the pipe. Show all work. Give in your answer the design pressure of the pipe and the surge pressure.

2. Explain what type of experiment to conduction, what type of data to collect , and  how to derive the coefficients  of the infiltration function based on measured data. How is the infiltration function used in designing a sprinkler and surface irrigation system.  Explain the answer fully.

3. An Electric diaphragm valve has a in-rush current of 0.45 A and a minimum operating voltage of 21 V. It is connected to a controller with size 16 conductors. How far apart can the controller and valve be placed if the controller output voltage is 28.

4. A furrow irrigation system has an advance and recession of :

 Advance Time After Start hrs. Advance( ft) Recession (ft) 0 0 - .33 200 - .7 400 - 1.4 600 - 2.3 800 - 4 1000 - 5 - 0 5.2 - 200 5.4 - 400 5.6 - 600 5.8 - 800 6 - 1000

A furrow 1,000 ft long in soil having a final  infiltration rate of 1 inch per hr and an infiltration function of I=1.0 t^-0.5  where t is in hr and I is in inches/hr   is irrigated for 5 hours with a stream of 45 gpm. The accumulative infiltration function is D= 2 t^0.5.  This represent an area of 0.069 acres since the row spacing is 3 ft.

a. Plot the advance and recession curves on the computer

b. Compute the time that surface water is in the furrow at each section

c. Compute the inches of water that enters the soil at each station.

2. Determine water distribution efficiency

3. Assuming that 3 inches of water had been depleted from the soil before irrigation, compute the application efficiency.

5. Describe the process and list the steps in designing a drip irrigation system and then list the components of a drip system that must be designed.  Start with the water needs of the plant. Give the urls or the pages in your book where you get the needed design information.

Example,

6. A cotton field was planted last year on April 25, 2007 at the plant science university farm. Lyndecker  farm. The soil was a loam soil. Determine the dates that a 3 inch irrigation should have been applied through out the growing season. . Turn in spreadsheet showing calculations.

7. Explain the evolution of irrigation technology, identify the different types of irrigation technology and explain the advantages and disadvantages of each technology.

8  10 points extra credit.  Using Basin program calculate the application efficiency and border width of a pecan border irrigation that is dead level that has a clay loam soil  and net targeted infiltration amount of 4 inches and a bare soil with a manning n of 0.04.    The length of the basin is 500 ft,  the width is 450 ft and the flow is 3600 gpm. Use screen capture to turn in results. Explain why you selected the design that you did. The  distribution efficiency must be greater than 75%