Arena Watering Key Points 

What is the “ideal” moisture content for my Arena?

• On most footing types, a 10% moisture content is considered “Ideal”

How do I measure moisture content?

• The moisture content is the % of water in the footing on a per weight basis.  The simplest way to measure the moisture content is by a soil moisture probe.  These moisture meters will give an approximate % of moisture present.

Now that I know the moisture content, how do I get to the 10% level?

• Once the moisture content is known, then we can calculate the amount of water to apply with the Rapid Rain™ arena watering system.  Typically between 18 and 20 gallons of water per 1000 square feet will increase your arena moisture content by 1%.  If you need to raise your existing level by 5%, then you will need to apply approx 90-100 gallons of water per 1000 square feet through your Rapid Rain™.

This figure is derived by calculating the volume of soil in the 1000 square ft (3 inches in depth) and multiplying by the bulk density of typical footing.  Then the desired water percentage is figured using approx 8 lbs of water/gallon.  Again this does not have to be complicated.  Use the 18-20 gallons of water rule, and you will be close.

How many square feet are in my arena?

• This can be calculated by multiplying the length times the width of the arena in feet to obtain your square feet amount.  For example, a standard Dressage Arena is 66ft x 197 ft (20M x 60M).  This is a total of 13,000 square feet.

How long should I run my Rapid Rain™ to achieve the proper water application?

• Using the above figures, one can easily determine how long to run your Rapid Rain™ watering system.  Let us use the above arena size as an example.  Your arena is 13,000 square feet, and the footing is considered noticeably dry (3-4% moisture).  Therefore, from the above calculation we know that we need 6% more moisture to reach the 10% optimum level.  If we use the 19 gallons for every 1%/1000 square feet, then we would need 6x19 gallons or 114 gallons total per every 1000 square feet.  Since we have 13,000 square feet, then 13x114 gallons would be 1482 gallons total needed on the arena to have approximately a 10% moisture content 3” in depth.  We can look at the Rapid Rain™ Performance Guide and estimate the gallons per minute being applied at the arena site,   Let us use 6.5 gallons per minute as an average flow rate for the Rapid Rain 860 model.  Then 1482 gallons/6.6 GPM = 228 minutes or 3.8 hrs of run time for the Rapid Rain™ to increase the arena by 6% moisture.  If we were only increasing the arena by 3% moisture, then the run time will be cut in half (1.9 hour run time).  The Rapid Rain™  speed control allows you to change your run times as needed.    

How often should I water my arena?

• There are many different footing types, and therefore theories on watering regimes for arenas.  Our experience has been that moisture levels should be obtained by deep watering combined with arena grooming to establish a good moisture “base”.  Supplemental watering should be completed when needed to maintain the ideal 8-10% moisture level.  The speed control adjustment on the Rapid Rain™  allows you change your water applications in order to match your moisture needs (see above).  We do recommend that you stay relatively consistent with your watering schedule since this allows you to become comfortable with speed settings on the Rapid Rain™.

What kind of sprinkler head works best on my Rapid Rain™?

• The standard sprinkler we use on the Rapid Rain is a fast return impact sprinkler with adjustable nozzles (including low angle nozzles for indoor arenas).  This sprinkler performs very well in a variety of applications.  Under certain circumstances, we recommend other head types such as a rotor.  These heads can be purchased on our on-line store.