12.7: Questions
- Page ID
- 44659
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)1. Describe the advantages and disadvantages of hand-move, towline, and side-roll irrigation systems. Discuss any issues that would limit the adequacy at these types of systems.
2. Discuss two of the general management problems associated with moved lateral irrigation systems (e.g., side-roll, hand-move, towline).
3. Determine the required set time for a side-roll irrigation system with the following characteristics:
Spacing along the lateral is 40 ft.
Spacing along the mainline 60 ft.
Sprinkler discharge is 8 gallons per minute.
Application efficiency is 75%.
Soil water depletion at irrigation is 2 1 /2 in.
4. A tow-line irrigation lateral has a sprinkler spacing of 40 ft. The spacing between adjacent positions for the lateral is 70 ft. The diameter of coverage (dc) for the sprinklers is 103 ft, and the average wind speed is 7 miles per hour. Is the sprinkler spacing and distance between laterals acceptable for good water distribution?
5. Determine the maximum acceptable irrigation interval for a silty clay loam soil where the root depth is 4 feet deep, fdc is 45% and the anticipated net crop water used rate is 0.3 in/day.
6. Determine how the management plan would change in Figure 12.7 for a crop that had a root depth of 2.5 ft and the soil was a sandy loam soil.
7. How would you change the orientation of the mainline and laterals in Figures 12.6 and 12.7 if three laterals were required for the field? What sizes of mainline would you recommend and what total length of pipe would be needed to minimize investment cost?
8. A lateral in an existing solid-set irrigation system consists of 2½-inch PVC pipe that runs up a hillside with a 2% slope. Sprinklers are 30 feet apart on the 600-ft long lateral. Impact sprinklers with a single 3 /16-inch nozzle are used. The design called for an average nozzle pressure of 55 psi. Your client has complained about dry areas at the distal end of the lateral.
a. Do you expect uniformity to be an issue with this system?
b. How could pressure regulators be used to improve uniformity? Where would you put them and how many would you recommend?
c. Suppose you decided to change nozzles in the lateral to achieve acceptable uniformity without regulators. What size of nozzle would you recommend at the distal end of the lateral?
9. The gun on a traveler irrigation system discharges 400 gpm and the towpath spacing is 240 feet.
a. What travel velocity is required to apply a gross depth of 2 inches?
b. What is the application rate if the wetted radius of the gun is 200 ft?
10. How many gallons of diesel fuel are required to apply an acre-inch of water with the traveler system shown in Figure 12.22?
11. The design net system capacity (Cn) for a moved-lateral irrigation system on an alfalfa field is 0.21 in/d. The system is moved every 12 hr (set time = Ts = 12 hr), with downtime to move the system being 1 hr. Downtime allowed for harvesting alfalfa is 10%. The ELQ is 75% (allows for 10% drift & evaporation; assumes no runoff). Determine the gross system capacity (Cg) in gpm. If the area of the field is 33 ac, what is the minimum flow rate (Qmin) needed for the system?
12. Your client purchased a field identical to the one in Figure 12.6, except the soil is a silt loam and the field has a hard-hose traveler. The traveler has the characteristics listed below. You will need to determine mainline orientation and size, length and width of towpath, and times for management. Justify any additional assumptions you require.
a. Develop a traveler management spreadsheet and plan for the field.
b. Discuss any issues you foresee for this field and propose solutions as needed.
Traveler and field characteristics are as follows:
The soil is predominately silt loam.
A hard hose traveler uses a 1.46-inch diameter nozzle operated at 60 psi.
Characteristics of the gun are available from Table 12.6.
Parameters for gun discharge equation are Cd = 15.97, a = 0.50, and b = 2.586.
The inlet pressure for the hose reel should be 104 psi for 60 psi at the nozzle.
A 4-inch inside diameter hard hose (Hazen-Williams’s coefficient of 150 is appropriate).
Hard hose is 1320 feet long.
Cart and turbine losses as a function of flow can de determine from Figure 12.21.
The irrigator plans to irrigate field beans with a root depth of 3.5 feet and and critical depletion fraction of 45%.