Soils 456  Final Exam Sprint 2004

 

1.  A main line for the drip irrigation designed in lab was installed from the south side of the horticulture farm to the vegetable irrigation site.  The line installed was a schedule 40 3 inch pipe if the velocity is 5 ft/sec. The line was used to irrigate the sprinkler experiment in addition to the 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. Give in your answer the design pressure of the pipe.

 

 

 

 

 

 

 

 

 

 

2. Explain how the process by which infiltration of water occurs. List two type of  mathematical functions that  fits the infiltration rate process measured data  and explain how to derive the coefficients of those functions based on measured data. How is the infiltration function used in designing a sprinkler and surface irrigation system. 

 

 

 

 

 

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 and explain how to design the component. m.  Start with the water needs of the plant. Give the urls or the pages in your book where you get the needed design information. Assume that the flow rate in the main and sub main is 35 gpm, give the specific equipment needed for that flow rate, specify size  and  supplier.

 

 Example,

 

A filtration system is a sand media filter and the design criteria is to select a crushed granite or silica to remove particles of 50 to 100 micrometers or larger in diameter with a screen mesh of 200.  The design criteria is a  surface area of the filter of 1 ft^2 for every 17 gal /min of flow. From this information the size tanks can be specified and the type of sand media filtration material. The location of the sand medial filter is before any solenoid control valves see picture of location.  The filter contains a  pressure  actuated automatic  controlled back flush  system.  Area of filter is 2 ft^2 which is a filter of 1.5 ft in diameter. Select  yardney 18-2 filter which is  1.5 ft in diameter.

http://www.yardneyfilters.com/sand_media.htm

 

 

 

6. A cotton field was planted last year on  April 25, 2001 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. Turn in spreadsheet showing calculations. 

 

 

 

  1. 8 points extra credit.  Using Basin program calculate the application efficiency of a pecan border irrigation that has soil infiltration type SCS group 3 and net targeted infiltration amount of 4 inches and a bare soil with a manning n of 0.04.  Use the general design criteria SCS.  The length of the basin is 500 ft the width is 450 ft and the flow is 3600 gpm