Thursday, July 4, 2013
Building Unity Farm - Water management
I was recently asked how we manage irrigation at Unity Farm during the peak of Summer heat.
Although we have a stream running through the farm, it's part of a protected wetland, so we do not use it for irrigation.
Our water source is a 300 foot deep well that consistently produces 7 gallons per minute all year long. Sherborn was founded in 1652 and was initially called Bogostow ("Bog's town") because of the many streams, ponds, and wetlands. Our well has the benefit of being at near a drainage swale an nature keeps the aquifer seasonally recharged.
However, irrigating acres of orchards, paddocks, and produce as well as meeting the water needs of the 3 generations living at Unity Farm via a 7 gallons per minute well takes careful planning.
Here's what we do:
In 2012, we replaced the 18 year old well pump, wiring, and control system to give us the best infrastructure possible. We also replaced the pressure tank. The water is so chemically pure that it does not need a filter, a settling tank, or treatment of any kind. We were able to retire all the water treatment equipment that was initially installed after the well was drilled. We placed digital flow gauges on the internal and external water mains so we can measure our water use and rapidly identify any unexpected variations such a broken pipe or leaking valve.
As we designed our animal and crop areas, we incorporated over 50 zones of irrigation controlled by two Hunter irrigation controllers, that enable us to selectively apply drip irrigation or low volume rotors to each area based on rainfall, plant maturity, and seasonal conditions.
For example, 7 gallons per minute can supply 420 one gallon per hour drip heads. For each blueberry zone, we ran 400 feet of drip hose containing built-in one gallon per hour heads spaced every foot. With two heads per plant and twice weekly 30 minute waterings, each plant receives 2 gallons per week precisely targeted to the roots. We have 7 of these zones, running on Wednesday and Sunday nights between midnight and 3:30am.
Our pastures and paddocks have 23 zones of 4 low flow 1 gallon per minute rotors. We run these for 10 minutes between midnight and 4am on Tuesday, Thursday, Saturday.
We tend to be generous with water to new plantings and parsimonious with water to well established plants.
We also have two rain sensors that automatically shutdown all our watering systems whenever more than half an inch of precipitation falls within a 24 hour period.
In summary we have
23 low volume rotor zones for pasture
7 drip lines for berries
House and Barn zones
8 low volume rotor zones for paddocks
4 drip lines for foundation plants around the house
11 low volume rotors zones for landscaping
We've also placed seven 75 foot hoses around the property for selective hand watering, cleaning, and animal care
From 1986-1993 we ran a vineyard on an arid mountaintop in Northern California and developed all the skills needed to carefully manage an agricultural operation from a well with limited capacity.
We've had record heat this season. With targeted use of drip, rotators, and hand watering, everything is thriving on Unity farm.
Posted by John Halamka at 3:00 AM