Landscape Irrigation Design practice

All 15 free landscape irrigation design questions

1. Which head type covers a large open lawn with the fewest heads?

   • A Pop-up spray heads Spray heads throw only a short radius, so a large lawn needs many more of them than rotors.
   • B Bubblers A bubbler waters one small spot or basin and cannot spread water across an open lawn.
   • C Drip emitters Drip emitters wet the soil at single points, so covering a lawn with them takes far more devices than rotors.
   • D Rotor pop-ups Correct

   Because rotors throw water much farther than spray heads, each rotor covers far more ground and a large open lawn needs far fewer of them.

2. Every drip irrigation system must include:

   • A A flow sensor A flow sensor is an optional part for spotting leaks; nothing requires one on every drip system.
   • B A master valve A master valve is installed only where the design provides one; it is not required on every drip system.
   • C A filter Correct
   • D A quick coupler A quick coupler gives hose access to system water and is not a required drip part.

   Texas A&M AgriLife's drip guide says every drip system must have a filter ahead of the emitters, because the emitters' very small openings clog with grit and sediment. That "must" is AgriLife's advice, not a Texas rule.

3. Which of these is an emission device?

   • A A drip emitter Correct
   • B A zone valve A zone valve opens and closes a zone but applies no water itself.
   • C A backflow preventer A backflow preventer protects the drinking water supply and applies no water to the landscape.
   • D A controller A controller runs the valves on a schedule and applies no water.

   An emission device is any part that puts water onto the landscape, and the definition in 30 TAC 344.1(11) lists spray heads, rotors and drip emitters as common examples.

   30 TAC 344.1(11)

4. Which soil takes in water most slowly?

   • A Sand Sand is coarse and takes in water quickly.
   • B Sandy loam Sandy loam is mostly sand and takes water in faster than clay.
   • C Clay Correct
   • D Loamy sand Loamy sand is coarse textured and takes in water quickly.

   Fine textured soils such as clay have small pores and low infiltration rates, while coarse sandy soils take water in fast. Clay is therefore the slowest of the four.

5. Evapotranspiration is the water lost through:

   • A Runoff and deep drainage Runoff and deep drainage are losses from poor scheduling; evapotranspiration is evaporation plus plant use.
   • B Evaporation from soil and transpiration by plants Correct
   • C Evaporation from the spray while the heads run Water lost from the spray in the air is not the plant's need and leaves out transpiration entirely.
   • D Leaks and overspray Leaks and overspray are system faults and have nothing to do with the plant's water use.

   The plant's water requirement counts water that evaporates from the soil surface together with water the plant itself transpires, and those two together make evapotranspiration.

6. On what basis does TCEQ require an irrigation system's zones to be separated?

   • A Plant type, microclimate, slope, soil and water needs Correct
   • B The days of the week the owner prefers to water Watering days are a schedule choice made after zoning; the rule bases zones on site and plant factors.
   • C The pipe sizes on hand Pipe size follows from the zone's flow; it is not a basis the rule gives for splitting zones.
   • D The controller's station count The controller is chosen to fit the zones, and its station count is not a basis for separating them.

   TCEQ requires separate zones based on plant material type, microclimate, topographic features, soil conditions and hydrological needs under 30 TAC 344.62(e), because each of those changes how much water an area needs.

   30 TAC 344.62(e)

7. Which watering pattern is best for an established lawn?

   • A Light and daily Light daily watering keeps roots near the surface and wastes water to evaporation.
   • B Light, twice a day Watering lightly twice a day grows even shallower roots and loses more to evaporation.
   • C Deep and infrequent Correct
   • D Deep and daily Deep watering every day gives the soil no chance to dry and wastes water.

   Watering deeply and infrequently wets the whole root zone and lets it dry between waterings, because that grows a deeper root system that stands up to drought.

8. With head-to-head spacing, how far does each head's spray reach?

   • A All the way to the next head Correct
   • B Halfway to the next head Spray that reaches only halfway leaves the ground between heads unwatered; head to head means reaching the next head.
   • C Two-thirds of the way there Stopping short of the next head leaves a dry band, and the definition requires the spray to reach it.
   • D Only to the edge of the lawn Where the spray reaches the lawn edge says nothing about coverage between heads, which is what the term describes.

   Head-to-head spacing sets heads within the maker's published radius so that the spray reaches from one head to the next, as TCEQ defines it in 30 TAC 344.1(15).

   30 TAC 344.1(15)

9. How must an irrigation plan used for construction be drawn?

   • A To a stated scale Correct
   • B Freehand with dimensions A freehand sketch with dimensions written on it does not meet the rule that the plan be drawn to scale.
   • C In full color Nothing requires color; the requirement is a drawing to scale.
   • D On the property survey Nothing requires the plan to sit on a survey; it must be drawn to scale and state that scale.

   Every irrigation plan used for construction must be drawn to scale, and 30 TAC 344.61(c) also requires the plan to state the scale used.

   30 TAC 344.61(c)

10. In what unit is a precipitation rate given?

    • A Inches per hour Correct
    • B Gallons per minute Gallons per minute measures flow through a head or a zone.
    • C Gallons per hour Gallons per hour measures the flow of an emitter.
    • D Inches per week Inches per week is how a weekly water need is stated, not the rate a zone applies water.

    A precipitation rate is the depth of water a system puts down over time, and it is therefore given in inches per hour. Landscape rates usually sit between roughly 0.5 in/hr and something over 1.5 in/hr.

11. What must all the heads in one zone have in common?

    • A The same radius of throw Heads with different radii can share a zone as long as their precipitation rates match.
    • B The same arc of coverage Quarter, half and full circles share zones all the time when their rates are matched.
    • C The same precipitation rate Correct
    • D The same nozzle flow Matched nozzles use different flows for different arcs so that the rates come out equal.

    TCEQ requires every emission device in a zone to irrigate at the same precipitation rate under 30 TAC 344.62(f). Heads of different arcs, radii and flows may share a zone only when their rates match.

    30 TAC 344.62(f)

12. At what pressure does TCEQ require heads to be installed to operate?

    • A The maker's recommended pressure Correct
    • B The static pressure at the meter Static pressure is the supply with no water moving; heads are held to the pressure the maker publishes.
    • C The pipe's pressure rating The pipe's rating is the most it can safely hold, not the pressure a head should run at.
    • D 30 psi for every head No single pressure is set for every head; it depends on the maker's figure for the nozzle and spacing.

    TCEQ requires emission devices to be installed to run at the optimum or recommended pressure the maker publishes for the nozzle and spacing used, under 30 TAC 344.62(c).

    30 TAC 344.62(c)

13. On a new system, above-ground spray may not water a strip with paving on two sides if the strip is narrower than:

    • A 24 in 24 in is half the limit; strips from 24 in up to just under 48 in are barred as well.
    • B 36 in 36 in is still under the limit, so the bar reaches strips wider than 36 in too.
    • C 48 in Correct
    • D 60 in The limit is 48 in; a strip 48 in or wider may use spray.

    New systems may not use above-ground spray devices in landscapes less than 48 inches wide or long, not counting the paving, that have walk or drive paving along two or more sides, under 30 TAC 344.62(b)(2).

    30 TAC 344.62(b)(2)

14. Head spacing may differ from the maker's published radius or spacing by no more than:

    • A 5 percent 5 percent is tighter than the rule; spacing may vary by up to 10 percent.
    • B 10 percent Correct
    • C 20 percent 20 percent is twice the tolerance the rule allows.
    • D 25 percent 25 percent is well past the plus or minus 10 percent the rule allows.

    Since the amendment effective July 26, 2020, 30 TAC 344.62(b)(1) lets head spacing vary by up to plus or minus 10 percent of the maker's published radius or spacing and no further.

    30 TAC 344.62(b)(1)

15. The water a well-drained soil still holds after the free water has drained away by gravity is called:

    • A The wilting point The wilting point is the low end, the water content at which most plants can no longer draw enough water.
    • B Saturation Saturation is the soil before the free water drains, with its pores full.
    • C Available water Available water is only the part plants can take up, which stops at the wilting point, not all the water left after draining.
    • D Field capacity Correct

    Field capacity is the water a well-drained soil holds once gravity has drained the free water out, and it sets the top of the range plants draw on. A sandy soil reaches it within hours, while a clay can take several days.

    NRCS NEH Part 652, Irrigation Guide, p. 2-4 Reference document, not law.