Client Login
Home
Careers
Resources
Landscape Irrigation 
  

Water Management, Inc’s mission is to provide the highest quality professional design and consulting services, with a focus on offering innovative and sustainable solutions towards water conservation. We fully recognize our environmental responsibility strive to help educate and motivate others to promote the conservation of our water both inside and outside.  We offer many irrigation services and sustainable practices that are easily implemented.  Water conservation depends on several factors, including:

     --Controllers
     --Plant and grass selection
     --Distribution system

 

 

Irrigation Services

Typical irrigation control systems consist of automatic valves connected to a multi-station clock controller.  Watering is based on preset schedules regardless of weather or soil conditions.  These systems are generally not effective at delivering water to the turf roots in an efficient manner while eliminating runoff because they are open looped.  They require human intervention (programming) to turn the system on and off as the needs arise.  Because the major focus of landscape managers should be spent on turf maintenance and upkeep, most of the time landscape managers are not available to adjust the watering schedule based on plant needs or changes in weather patterns.

One solution is to install a “smart controller” that is essentially a automatic controller that is connected to soil moisture sensors or to a weather station – this way a closed-loop systems can be created that allows for feedback to the irrigation system so that it can turn on and off automatically.

Smart controllers based on evapotranspiration (ET) rate receive daily local weather updates that it uses to determine each zones ET rate – a combination of the soil’s and the plants evaporation rates based on changing weather data (temperature, wind, humidity, solar radiation) or historical ET rates.  It uses this information to determine how much water the grass / plants in that zone will need.  In cool weather an ET based controller might not apply water for several days.  In hot weather, the controller will water as long and as often as the turf needs.  While ET controllers are more accurate than typical control systems, these systems require additional knowledge to operate and understand.

Several types of analysis need to be done in order to create an effective strategy to lower irrigation water usage and discover potential new sources of irrigation water to supplement the potable water supply. 

Designing water efficient irrigation systems starts by doing a comprehensive irrigation system audit to identify key factors that influence performance efficiency.  Some of these factors include distribution uniformity, precipitation rate, controller settings, pressure and how these interact with existing property soil characteristics.  Delivering the correct amount of water to the turf, trees, shrubs and flowers at the right interval and in the right way requires expertise in evapotranspiration (ET) and soil dynamics.  Choosing the right technology for your landscape application is the key.  The best manual irrigation, ET controller, or soil moisture sensor will not be effective without correctly integrating irrigation system components with the natural landscape.  The best way to achieve maximum water savings is through proper analysis and implementation. 

Landscape irrigation system audits should be done periodically to evaluate the system performance.  A typical irrigation audit consists of a series of field procedures for collecting and compiling irrigation system data: then using the data to evaluate system performance characteristics, such as distribution uniformity and precipitation rates of the components.

Listed below is an outline of the type of information that we would collect during a comprehensive irrigation audit so that various irrigation measures and improvements can be identified along with the anticipated costs and associated savings.  Our irrigation audits often include rain water harvesting opportunities.

 

 

Irrigation Audit

  1. Perform distribution uniformity testing on the irrigation systems including assessment of nozzles sizes, pressures, spray-pattern and system layout.
  2. Determine what type of watering schedules are currently being used and also determine based on historical evapotranspiration rates the amount of water that would be required to benefit the turfgrass and allow the water to fully penetrate down six to eight inches.
  3. Survey athletic fields’ irrigation pipes, connections and fittings for leakage. 
  4. Check nozzle sizes and note areas that need fixing such as broken rotors, pipes and sprinkler heads.
  5. Develop models/graphs of historical and real-time weather data to determine evapotranspiration, and to determine worst-case scenarios for amount of water needed by turfgrass in seasons past, present, and future.
  6. Identify areas where rain sensors can be installed to shut-off irrigation clocks when raining. Identify where new controllers can be installed along with support equipment.
  7. Locate, identify and read all irrigation meters.
  8. Analyze data gathered during irrigation audit and summarize.  Find out the capabilities of campus maintenance team and evaluate as to what type of education or additional equipment may be needed to help maintenance in the best possible way.

Ideally water usage is determined from dedicated water meters for the irrigation system, but often that information is not available, therefore usage is calculated using the following formula:

Estimated Application Rate Inches per Hour/Actual Minutes per Day X Cycles per Week X number of weeks per season X Estimated Acres X 27,154 gallons of water per acre inch divided by Percentage of Shutdowns during rainfall events = Estimated Gallons per Year.

 

 

 

Improved distribution uniformity auditing technique:

A different and newer method for determining the efficiency of the irrigation system other than using catch cups is to determine the efficiency of the system by using a Time-Domain Reflectometry System (TDR) to record the soil moisture.  A distribution uniformity calculation can be done taking the recorded soil moisture data.  Commonly, the calculation is done with water collected in catch cans laid out in the area being irrigated.   A formula known as Low Quarter Distribution Uniformity (DULQ) is most commonly used.  The DULQ is the average of the lowest 1/4 of the catch can volumes divided by the overall average of all catch can volumes.  The process is detailed in the Certified Landscape Irrigation Auditor manuals available from the Irrigation Association.  A similar process is followed to compute the DULQ of the soil moisture data. The data is ranked from lowest to highest soil moisture content. The average of the lowest quarter of readings is divided by the overall average. The result is presented as a percent. The value of this calculation, compared to the catch can DULQ, is that it is a measure of water in the soil profile as opposed to water applied to the turf surface.  Factors such as compaction, thatch, slope, and moisture re-distribution can cause the variability pattern to be very different between the application (catch can) and soil moisture measurements.

Using the TDR system a histogram can be built and which can then be used as a tool for visualizing which part of the complete data range comprises most of the data.  A 2-dimensional color chart of geo-referenced data from a TDR soil moisture probe with a serial input connected to a GPS source.  The contour plots give a powerful visual image of the variability across the site.  The data point charts give you the ability to see the impact of individual data points on the interpolated map.  A summary of the data is also included along with a histogram to give an additional visual image of the data.  Below shows the results of these tests:

The park pictured here has 118 rotors and 182 spray heads.  The park has rotors that are quite evenly spaced across each valve.  During the audit process, rotor pressure was taken and the pressures were 30 psi to 38 psi.  That pressure is too low for the Rainbird Falcon 6504, Rainbird 4151, Rainbird R-50 and older Rainbird T-Bird Rotors.  The main issue was the miss matched heads. 

A catch cup test was performed at night when the rotors were running on the large middle outfield of the baseball field and the pressure was recorded at 40 psi, the lower end of the pressure chart required by the manufacturer for these rotors. 

Using the catch cups (see section of map where a red square is drawn) the distribution uniformity is 74% DU.  This is a good reading but if you look at the rest of the park with using a TDR soil moisture probe and GPS mapping the story is different. 

The overall park DU becomes a 51.6%.  This is due to the wrong nozzles in the rotors, differing rotor and spray head spacing, overlap of rotors and spray head zones, lower pressures and incorrect irrigation scheduling.

The histogram of data along with the color legend shows quite a difference between soil moisture levels.  The statistical data from this testing indicates that the average reading is 37.8, and the highest volumetric water content was 89.1 with the lowest volumetric content at 6.6.  This difference is quite large. 

 

 Click to view a list of measures WMI recommended during an irrigation audit in Southern Nevada.

 

  
  
  
  
 
  
  
 
  
  

Water Management Inc © 2009