Rainwater Harvesting and Water Conservation

In early November I attended the Irrigation Association’s National Irrigation Show and Educational Conference.  Attendees have the opportunity to attend educational seminars, and to see some of the latest products in irrigation.  Most new products offer water conservation improvements from those utilized in the past.  One heavily marketed water conservation method is rainwater or stormwater harvesting.  This is the practice of catching, and storing, water that would typically be lost to runoff from non-pervious surfaces such as roofs or parking lots.  The stored water is then able to be utilized for non-potable uses such as irrigation.  This is a wonderful way to conserve water, but does have one major downfall.  The cost of providing storage for this captured water is expensive, and the return on investment period is typically longer than many like to see.  Some projects can justify the added expense, because it is part of the stormwater management plan, LEED certification, and/or the organization feels strongly about water conservation.  However, only 5% of our projects fall into one of these three categories.  Does this mean that unless one spends large amounts of money that water requirements for irrigation can not be reduced?  Absolutely not!  Below are several inexpensive methods to reduce landscape water use:  

• Good head to head coverage.  Sprinklers should be spaced so that the water stream from one touches another sprinkler.  This provides good uniform distribution of water throughout the irrigated area.  This is the way the manufacturer’s design the sprinklers.  Stretching the spacing or eliminating a sprinkler reduces distribution uniformity.  The result is longer run times to compensate for the dry areas, and higher water use.  
• Proper sprinkler inlet pressure.  Too much or too low of water pressure has a negative effect on sprinkler performance.  One produces a fine mist that is lost in the wind and evaporation.  The other provides a beautiful green donut pattern in turf areas.  Either results in a higher water bill.  
• Reduced flow rate spray nozzles.  Old style spray nozzles, fixed and variable arc, have a very high flow rate.  A flow rate much higher than most soils can handle resulting in unwanted run-off.  Most manufacturer’s now make spray nozzles that water at a much more manageable flow rate.
• ET-based / soil moisture sensors and smart controllers.  This technology has received a lot of negative and positive publicity.  A lot of the negative opinions of these controllers and technologies are related to the area of the country one resides in and sometimes mis-management.  My opinion concerning smart controllers and sensors are mostly positive.  Our area of the country “supplements” water requirements for landscapes.  Typically controllers are set in the spring for water requirements in July and turned off in October.  Water requirements are greatest in July.  Having a controller reduce watering times, based on current weather or soil conditions, has a huge potential to minimize water use.
• Rain sensors.  Watering is suspended when a pre-set amount of rainfall is received.  Rain sensors or switches are so inexpensive I can not think of a situation when one should not be installed.