Dear Readers, Welcome to Irrigation Engineering Interview Questions have been designed specially to get you acquainted with the nature of questions you may encounter during your Job interview for the subject of Irrigation Engineering. These Irrigation Engineering Questions are very important for campus placement test and job interviews. As per my experience good interviewers hardly plan to ask any particular questions during your Job interview and these model questions are asked in the online technical test and interview of many IT companies.
Simply stated, irrigation provides the water requirements for sustainability of plants when rainfall is not sufficient.
Ornamentals: Trees and shrubs are irrigated frequently when grown in the nursery and when first planted so that their roots quickly grow out from the root ball and into the soil in the landscape. It is crucial that roots grow as quickly as possible so irrigation can cease. The best way to encourage rapid root growth is frequent light irrigation applied to the root ball after planting. Under ideal conditions (e.g., in non-compacted soils, surrounded by extensive irrigated areas), many Florida-Friendly plants do not require further irrigation except in prolonged drought.
Turf: Although Florida receives substantial rainfall, dry periods are common in the late spring and fall. The dry period in the spring coincides with peak plant water needs due to increasing temperatures, solar radiation, and day length. Due to relatively shallow roots, turfgrasses typically require irrigation at least once a week to maintain quality. On sandy soils, some grasses may need to be irrigated at least two days a week to ensure acceptable quality (Shedd et al., 2008).
Note: The term “irrigation requirements” implies well-watered conditions, which means that this is the amount of irrigation water in addition to effective rainfall (that which is stored in the plant root zone and available for use) needed for plant growth and without any water stress.
Ornamentals: All landscape shrubs and trees grown in a nursery and planted in a landscape require water to become established. Under most circumstances, rainfall occurs irregularly, so irrigation is required, at least until plants are established. Trees require about three to four months per inch of caliper (trunk diameter measured 6" from ground) to become established. Shrubs require about 20 to 28 weeks to become established. Irrigation events should be 2 to 3 gallons of water per inch trunk diameter. For example, a 2-inch tree should be watered 4 to 6 gallons at each irrigation event. Water every other day until plants are established.
In addition to initial watering for establishment, irrigation in the year following establishment may be needed to maintain good quality in dry weather. We have little data on irrigation requirements for plants once established, due to the many factors that influence this. These factors include slope, aspect, soil compaction, soil depth, soil volume, width of soil space, depth to water table, wind, season, size of plant at planting, nursery production method, length of time in the container, and root pruning strategies at planting. This research simply has not been done.
Turf: Under well-watered conditions, Stewart and Mills (1967) reported that annual water consumption in South Florida for St. Augustinegrass and bermudagrass averaged 43 inches/yr over five years. For North Florida, Jia et al. (2007) reported 33 inches of total water requirements for bahiagrass. Irrigation requirements for turfgrass in North Florida are on the order of 20–25 inches/yr and 30–35 inches/yr in South Florida, on average (Smajstrla, 1990). These numbers are net irrigation requirements and do not include added irrigation due to the inefficiency inherent in all irrigation systems. See “Efficiencies of Florida Agricultural Irrigation Systems, ” for more information on irrigation efficiency (Smajstrla et al., 1991). In most years, rainfall will contribute substantially to meeting the total water demand of turfgrasses.
Many studies have been conducted on water use of turfgrasses. Most of these studies are conducted under “well-watered” conditions (i.e., no stress due to lack of water) and should not be confused with drought studies where water is withheld and physiological responses of grasses are studied.
All turfgrasses need water to sustain good quality (dense, uniform, green), whether it comes from rainfall or supplemental irrigation. Drought-tolerant grasses will go into dormancy during dry periods, growing more slowly or turning brown until conditions are favorable for growth. When enough soil moisture returns, these grasses can usually recover from drought-induced dormancy rather than dying. For example, bahiagrass is drought-tolerant, but if it is not supplied with adequate water, the drought response of this grass will result in dormancy and a “dead” appearance.
Much of the literature seems to indicate that there may be differences in water use between different warm-season grasses. These disparities likely stem from natural differences in mowing heights (e.g., St. Augustinegrass lawns versus bermudagrass golf turf), fertility, leaf architecture, etc. However, these differences have not been clearly documented in Florida work.
In one study, Zazueta et al. (1999) found that when maintained under UF/IFAS recommendations, bahiagrass had 11 percent higher water use rates than St. Augustinegrass when well-watered, but that the two grasses had similar transpiration rates when under continual stress. A current UF/IFAS study is exploring the water use rates, under well-watered conditions, of several grasses including St. Augustinegrass and bahiagrass.
A plant's indigenous status does not affect its fertilizer or irrigation requirements. There is no scientific evidence that native plants require less fertilizer and water than plants not native to Florida. To put it another way, residential and commercial landscapes are often very different from the native conditions where a plant originated, even if they are found in the same state. Additionally, a plant that was previously indigenous to a site may not be adapted to the location any longer, depending on the way the site has been altered. In a recent research study, Florida native shrubs required the same irrigation as non-natives (Scheiber et al., 2007). Fertilizer requirements have not been tested.
The scientific evidence seems to point to human behavior with regard to over-irrigation—not particular plants in the landscape—as the reason for much wasted irrigation water. In addition, there is some evidence that in well-watered (i.e., sustained good quality) conditions, bahiagrass uses slightly more water than St. Augustinegrass. Thus, replacing St. Augustinegrass with bahiagrass will not likely reduce water needs for well-watered conditions. In addition to water, there are many other factors, such as maintenance level, diseases, and pests, that need to be considered related to a turfgrass change.
Scientifically, irrigation should occur based on plant response to environmental demand. Thus, irrigation frequency and amount will be defined by the environmental demand (i.e., evapotranspiration, ET), soil water-holding capacity and plant root zone depth. Irrigation should be applied such that the soil water reservoir is filled and gravity drainage and runoff do not occur. This approach is detailed in an EDIS publication entitled, “Basic Irrigation Scheduling in Florida,” (Smajstrla et al., 2006), which provides summary information from internationally recognized publications such as “Crop evapotranspiration: Guidelines for computing crop water requirements” (Allen et al., 1998). This scientifically accepted approach aims to result in “well-watered” conditions where no stress is allowed. In addition, an irrigation system must be well-designed and in good repair to apply irrigation efficiently to plants (i.e., without losses due to runoff and deep percolation).
In practice, irrigation is often limited to specific days of the week by water management districts through most of Florida. Thus, landscape plants may undergo varying levels of stress depending on specific site conditions and plant type.
Ornamentals: In the case of newly planted trees and shrubs, water should be applied to the root ball and perhaps the soil just beyond the root ball. In all of the studies over the past twenty-two years on trees in Florida, the area beyond the root ball has not been irrigated. Trees and shrubs establish just fine without broad, landscape-wide (i.e. sprinkler) irrigation. For example, live oak and southern magnolia tree root systems extend to about 14–20 feet in diameter one year after planting in a non-compacted soil without interference from curbs, sidewalks and other soil obstructions.
Turf: Guidelines for turf irrigation include an irrigation system that is well designed and in good repair. Generally, UF/IFAS irrigation guidelines recommend irrigation of ½–¾ inches when 30–50 percent of turfgrass shows signs of wilt during the day. However, if an automatic irrigation system is used under day-of-the-week water restrictions, program run time recommendations are given in “Operation of Residential Irrigation Controllers.” The recommendations in this publication have been further refined into user-friendly guidelines and posted as the FAWN urban irrigation scheduler.
Physiologically, tolerance means that the organism tolerates the stress without suffering major damage or is able to continue to function in a stress-induced state. Plants may do this through drought avoidance, physiological adaptations that afford tolerance, or through efficiency mechanisms. Drought avoidance may be escape, such as a plant that reproduces quickly, thereby avoiding drought, or through conservation mechanisms such as stomatal closure, change in leaf canopy or orientation, or cuticular resistance. They may also avoid drought by developing an extensive root system.
Physiological adaptations may include osmotic adjustment, changes in cellular elasticity, and dessication tolerant enzymes, all of which help the plant maintain turgor. Efficiency mechanisms include high water use efficiency (WUE). WUE is often defined as growth per units water provided, photosynthesis per units water, etc. Mechanisms that enhance drought tolerance reduce WUE because growth and carbon assimilation are reduced by leaf firing, rolling, etc.
It is important to note that any plant will require frequent irrigation after planting to ensure survival and establishment. For established plants, the irrigation requirement is defined as the water needed, exclusive of rainfall, for a crop to grow without water stress. It is the difference between ET (evapotranspiration or plant water use) and rainfall. ET may be calculated using one of a number of models, all of which have inherent uncertainty. Using climatological data, one can estimate ET and thus calculate the irrigation requirement on a monthly or annual basis as the difference between ET and effective rainfall. Effective rainfall is rainfall that is estimated to remain in the root zone of the plant. Effective rainfall is the result of total rainfall minus losses to drainage and percolation below the root zone.
Ornamentals: Once drought-tolerant plants, like live oak and burford holly, are established, they can withstand extended dry periods with little or no irrigation.
Turf: All of our grasses in Florida use different mechanisms to go into dormancy during drought stress (leaf firing, rolling, etc.). This metabolic resting state allows them to survive the stress and some of them to resume growth after conditions again become favorable.
Yes, reclaimed water can be and is used for irrigation. In fact, Florida is a leader in the U.S. in the use of reclaimed water for irrigation, with approximately 660 million gallons of reclaimed water being used each day, according to the Florida Department of Environmental Protection 2006 Reuse Inventory.
Reclaimed water does typically contain elevated levels of salts relative to Florida surface and groundwater, except where saltwater intrusion is problematic in coastal areas. The elevated levels of salts in reclaimed water may impact different plant species in varying ways due to differences in salt tolerance. Periodic testing of reclaimed water used in irrigation is recommended.
Also, reclaimed water may contain plant nutrients, which may need to be considered in any fertility program. It is not clear that all the nutrients in reclaimed water are available for plants. Finally, the content of reclaimed irrigation water can vary between different municipalities due to permitting differences and specific differences between wastewater treatment plants.
Haley et al. (2007) showed that homeowners did use significantly less water in the winter than other seasons. However, overall homeowners over-watered as much as 2–3 times the amount needed by the plants, based on estimates of climate demand. Thus, there is some indication that homeowners reduce irrigation during periods when less is needed; however, it appears that over-irrigation may still occur.
In a word, yes, but only if they are enforced. Over time, their effectiveness can become reduced. Olmsted (2008) reviewed the literature to determine the effectiveness of day-of-the-week watering restrictions specific to Florida. In Hillsborough and Orange Counties, water use reductions (by utilities) were reported as 17–18 percent; however, no reductions were seen in Seminole County. In South Florida, day-of-the-week restrictions reduced water use up to 21.5 percent during one day/week watering restrictions.
Day-of-the-week restrictions limit flexibility for users who try to plan irrigation based on rainfall trends. In addition, they may encourage over-watering on the allowed day. Just because potable water demands decrease under restrictions, it doesn't mean that irrigation is being applied at the right time and in the right amount—in other words, it's possible that water is still being wasted, even though it may be a smaller amount. However, to a large extent, many landscape plants can survive during most periods of water restriction.
Ornamentals: Irrigation recommendations for trees can be found at http://hort.ufl.edu/woody/. There is no documentation of how many people follow them. It would be difficult to document the effect of specific practices on ornamental plant material, since these materials only make up part of the planted landscape in most cases. Further, in many irrigation systems, turfgrass and ornamentals and trees are not separated in terms of irrigation zones and thus receive the same amount of irrigation relative to the system programming.
Turf: UF/IFAS recommends watering when 30–50 percent of turfgrass wilts. This should provide water conservation benefits relative to “set it and forget it” time clock programming; however, this has not been documented.
Haley et al. (2007) showed that using the schedule recommended in “Operation of Residential Irrigation Controllers ” reduced watering by 30 percent over a thirty-month study. Thus, if this recommendation were followed, substantial water savings are possible for moderate to high irrigators. The “FAWN urban irrigation scheduler " uses these recommendations in a user-friendly fashion to encourage users to adjust irrigation time clocks to better adjust for climatic demand throughout the year.
Some turf species may not need water to survive, but all need water to stay green. Drought tolerance implies that the grasses will “fire” (turn brown) and reduce leaf area to conserve water. Some, such as bahiagrass or centipedegrass, will exhibit better recovery from drought stress. St. Augustinegrass and most of the zoysiagrass varieties will not generally persist well without supplemental irrigation during times of limited rainfall. Fertilization follows a similar trend—bahiagrass and centipedegrass have low fertilization requirements and can persist with relatively low levels of nutrients.
Florida statute 373.62 mandates the installation of a working rain sensor device or switch on all automatic irrigation systems installed since 1991. UF/IFAS research has shown that expanding disk rain sensors can be effective at conserving water. Potential savings of 17 to 34 percent were shown at ½-inch and ¼-inch thresholds under normal rainfall frequencies (Cardenas-Lailhacar & Dukes, 2008; Cardenas-Lailhacar et al., 2008).
Ornamentals: In 22 years of irrigation research on trees and shrubs, only drip irrigation and other low-volume irrigation devices have been used. These devices have allowed very little water application while maintaining plant quality, though there are issues with pests such as squirrels chewing through the lines, causing maintenance problems.
Turf: Cardenas-Lailhacar et al. (2008) showed that technology such as soil moisture irrigation controllers can reduce irrigation by 70–90 percent for a range of products and irrigation watering days without negatively impacting turf quality during normal rainfall conditions. Further work with properly installed soil moisture sensor irrigation controllers on homes in Florida shows the potential for 50 percent irrigation savings without a negative impact on landscape quality (Haley & Dukes, 2007). Similar savings appear possible with other “smart irrigation” controllers such as ET controllers.
Drip irrigation is the process of delivering precise amounts of water and nutrients directly to the plant's root zone, drop by drop, offering growers exact irrigation control and efficient use of limited water resources.
Slow even flow of water to plants and soil: Shrubs and plants will thrive. Application of water and nutrients directly to the plant's roots is the best way to ensure plant health and vitality.
Easy to install - flexible and daptable: Dripperline installs easily in tight, awkwardly shaped areas that are hard to water with conventional spray systems.
Solves spray irrigation: problems No damaging spray on buildings, windows, fencing, or pedestrians in high traffic areas. Avoids unsightly brown spots on roses and other flowers, since spray never touches the plants. Soil and foliage are kept dry, reducing fungal diseases.
Improved plant growth: Makes plants fuller and healthier. Water and nutrients delivered directly to the root zone promotes healthy plant growth and reduces plant stress. Soil aeration is improved because soil particles are not washed down, decreasing soil compaction and improving root growth.
Saves on maintenance & labor: No moving sprinkler parts to have to repair. Installs with far less labor than sprinklers.
Unobtrusive & aesthetic: Hidden and lying near the plant, colored Brown. Doesn't interfere with landscaping or scenery.
Security: No exposed sprinkler heads, pipes or surface dripperlines to trip on or tamper with.
You'll be delighted with the fuller blooms and greater beauty of your annuals and perennials when watered. Mature plants and shrubs grow fuller and healthier with dripperline's versus sprinkler watering.
To improve the productivity of irrigated land from the present low levels.
To improve use-efficiencies of Water, Energy, Nutrient and Human Effort in Agriculture.
To conserve scarce resources such as Water and Electricity.
To extend the benefits of irrigated agriculture to more people with the available water.
To facilitate better crop management through Fertigation and Chemigation
Crop Yield Enhancement
Saving in Irrigation Water
Saving in Energy in pumping
Savings in Fertilizer consumption
Quality Improvement of Produce
Improved Pest & Disease Control
Improves Soil Health
Reduced Weed Growth
Reduced Labor Costs
Suitable for Marginal lands
Suitable for inferior quality water
When a drip tape or tube is buried below the soil surface, it is less vulnerable to damage during cultivation or weeding. With SDI, water use efficiency is maximized because there is even less evaporation or runoff.
Sprinkler Irrigation is a method of applying irrigation water which is similar to rainfall. Water is distributed through a system of pipes usually by pumping. It is then sprayed into the air and irrigated entire soil surface through spray heads so that it breaks up into small water drops which fall to the ground.
Sprinklers provide efficient coverage for small to large areas and are suitable for use on all types of properties. It is also adaptable to nearly all irrigable soils since sprinklers are available in a wide range of discharge capacity.
Microirrigation is frequent application of water directly on or below the soil surface near the root zone of plants. It delivers required and measured quantity of water in relatively small amounts slowly to the individual or groups of plants. Water is applied as continuous drops, tiny streams, or fine spray through emitters placed along a low-pressure delivery system. Such system provides water precisely to plant root zones and maintains ideal moisture conditions for plant growths.
The basic types of microirrigation system are as follows:
Surface System: It is the system in which emitters and laterals are laid on the ground surface along the rows of crops. The emitting devices are located in the root zone area of trees.
Sub-surface System: It is a system in which water is applied slowly below the land surface through emitters. Such systems are generally preferred in semi permanent/permanent installations.
Bubbler system: In this system the water is applied to the soil surface in a small stream or fountain. Bubbler systems do not require elaborate filtration systems. These are suitable in situations where large amount of water need to be applied in a short period of time and suitable for irrigating trees with wide root zones and high water requirements.
Micro and mini Sprinklers: These are small plastic sprinklers with rotating spinners. The spinners rotate with water pressure and sprinkle the water. These are available in different discharges and diameters of coverage and can operate at low pressure in the range of 1.0 to 2kg/cm2. Water is given only to the root zone area as in the case of drip irrigation but not to the entire ground surface as done in the case of sprinkler irrigation method.
Pulse: Pulse system uses high discharge rate emitters and consequently has short water application time. The primary advantage of this system is a possible reduction in the clogging problem.
Biwall: It is extruded dual chamber micro-irrigation tubing manufactured from Linear Low Density Polyethylene (LLDPE). This system is suitable for all closely spaced row crops like sugarcane, cotton, vegetables, onion, tea etc.
Dripper lines solve the problem and avoid spraying your walls, window and fences. Consistent watering with dripper lines helps establish and protect new shrub beds and planting areas.
It is frequently more profitable to install a systems when you are dealing with long, narrow strips, awkwardly shaped areas, or tree, shrub and bedding plant areas - both from a materials cost and labor standpoint. To help the minimize liability and vandalism and saves your customers' costs associated with continued maintenance and water usage. A simple shrub bed installation is quick and easy, either buried 4" below the surface or beneath mulch.
Subsurface irrigation works better in heavy clay or sand conditions than traditional sprinkler systems. Even "heavy clay" and "sandy" soils are a mixture sand, silt and clay. Loam, which contains equal proportions of sand, silt and clay, is ideal. However, plants can thrive in a very broad spectrum of soil textures when subsurface watering is applied at the proper rate, with appropriate spacing. Different soils create typical wetting pattern shades as seen at right. Note the dramatic overlap ensuring total coverage throughout varying root zone depths.
Drip irrigation works great in clay soils. What most people regard as "heavy clay" and "sandy" soils are actually mixtures of sand, silt and clay which will allow for adequate water movement and retention between soil particles.
When applied slowly (as in drip irrigation) water radiates outward from its source point, creating an overlapping wetting pattern beneath the ground. See the "wetted pattern" illustration" at right. When applied slowly to the soil at a single point, water moves through the soil in two ways:
Downward pulled by gravity.
Outward and upward, pulled by a capillary action.
There are several ways to verify that your system is working, including:
Feel for moisture just below the surface of the soil directly above a dripper.
Run micro tubing to the surface at the end of a zone and use it as a point source dripper.
Install a flag indicator at the end of zone.
Monitor flow at the water meter.
Because water travels both upward and outward from the dripper, the soil will usually be damp at, or close to, the surface.
No. In fact, it will conserve water. The system's controller and rain sensor will be set so you receive only the amount of water you need. You will not over-water or under-water your lawn with an automatic sprinkler system.
Yes. You won't have to spend another minute of your valuable leisure time watering the lawn. Whether you are home or away your system will do the watering for you!
It will do a much better job because a professionally designed system will deliver exactly the right amount of water to individual lawn and garden areas.
If it rained at your house every three days the same exact amount each time you probably would not need a sprinkler system. But nature does not work that way, and the only way to ensure healthy, lush growth is to make certain your lawn and plants receive a regularly timed, evenly measured amount of water. In the dry season when there is little or no rain, your yard can suffer damage after just a few days without water.
By providing raised beds over the laterals.
It’s due to some fine particles clogging the emitter because of bad quality of water. In that case we should provide filtration unit for removing fine particulars present in the water.
50 % of installation drip irrigation cost as given as subsidy by the government.
Normally Black polythene film is recommended for controlling weeds.
Open all end caps in lateral; main and submain pipes and operate the motor at least ten minutes to remove all fine particles presents in drip irrigation system.
In Paired row system, the total number of lateral is less comparing to single row system. Total cost of unit will reduce by adopting this method.
Normally we recommended 60-70 cm from the top of the soil.
There is less pressure in pressure gauge or leaking problem in venturi system or pump is not functioning well.
Because of holes, bents and cuts in laterals. To avoid this close the holes and cut and remove the bends present in the laterals.
This is due to uncleaned lateral and more salinity in water. This can be avoided by cleaning the laterals fortnightly.
Presence of more algae or ferrous material in water. Clean the laterals with water or give chemical treatment.
Rain water entry inside. Corrosion in gauge pointer damage. Provide plastic cover and fix pointer properly.
Leakage in main opened outlet and low water level in well. Arrest the leakage and close outlet and lower the pump with reference to well water level.
Provide bypass before filter and regulate pressure. Place filter element properly. Fill required quantity of sand.
Due to damaged air release valve ring. Replace the damaged ring.
All vegetable crops, Flower and fruit crops and Tree crops.
Lemongrass, Groundnut, Pulses, Sugarcane and Tubercrops.