14.4.1: Control Station
- Page ID
- 44685
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)A sketch of a typical control station for microirrigation is given in Figure 14.6. A control station may include a pumping unit and controls, a backflow prevention device, water meters, filtration units, chemigation equipment, flow and pressure control devices, and irrigation controls. Depending upon the water source, a pump (no. 2 in Figure 14.6) may or may not be required. For some low-pressure surface drip irrigation applications, water from a small tank, barrel, or bucket can be delivered by gravity (Figure 14.7) and a pump is not needed. When the water source is an open body of water or a well, a pump may be at the control station or at some distance. When the water source is adjacent to the control station, the pump and its controls will typically be part of the control station (no. 2 in Figure 14.6). If the pressure is excessive, a pressure regulator or flow control valve will be required (no. 10 in Figure 14.6).
When an irrigation system is connected to a potential source of drinking water or when chemicals are to be injected into the irrigation water, a back flow prevention unit (no. 4 in Figure 14.6) is required. This device prevents any water and chemicals from flowing back into the water supply (see Chapter 15 for more detail).
Common at the control station is equipment for injecting chemicals into the mainline. Chemicals typically injected are for fertilization, water treatment, or pest control. Chemicals are injected into the irrigation water before the primary filter.
Figure 14.6. Example of an arrangement at the control station for a microirrigation system.
Figure 14.7. Examples of a gravity water supply system for surface drip irrigation on smallholder farms. (Photos courtesy of iDE, International Development Enterprises.)
Filters are installed at the control station to prevent the passage of unwanted particles into the system. Filtration of water from municipal sources frequently only require precautionary filtration that is frequently accomplished by a screen filter. Water taken directly from wells or open bodies of water generally require primary and secondary filtration. The primary filter should be located after the pump and chemical injection equipment. Secondary filters are installed downstream from the primary filter to remove particles which may pass through the primary filter during normal or cleaning operations. The most popular filtration system for microirrigation is a primary media filter (no. 6 Figure 14.6) followed by a secondary screen filter (no. 7 in Figure 14.6). See Figure 14.10 for typical filtration systems.
The last major item at the control station is a water measuring meter (no. 9 in Figure 14.6). Types of water meters used for irrigation systems are described in Chapter 3.
Items in Figure 14.6 labeled as no. 3 indicate possible locations for pressure gauges. For well-designed control stations pressure gauges are placed at nearly all of these locations. Measures of pressure are particularly important on each side of the filters. A significant decrease in pressure on the discharge side of a filter compared to before the filter indicates that the filter is becoming clogged and cleaning is required. Of course, the pressure gauge reading as water leaves the control station will provide assurance that the pressure is appropriate for proper operation of the microirrigation system.
Also important at the control station are strategically located valves. The location of valves depends upon the complexity of the control station and the desire of the irrigator to shut down the system to clean, repair, or replace components.