Water Storage and Irrigation System

A small deck and arbour disguises the concrete cistern which collects our spring water, and provides a beautiful space from which to enjoy the pond. The hand pump allows us to access water if the power is out.

Water is a precious resource on the Southern Gulf Islands… and figuring out how to manage what we have when we have it is integral for everyone.  The water source for our three acres of land is supplied by a spring, which has been a registered water source since the 1950’s.  It comes out underground from fissures through the bedrock slope that we have built our house on, and it is beleived that the main supply is filled by rain water running off of George Hill, which rises to the north of our property.  While the land had been only mildly developed, the source of the spring was dug and pooled into a gravel bed and directed to a small concrete cistern.  Previous owners added a small water pump and plastic 300 gallon tank for their domestic use, which serviced the trailer that we became residents of when we purchased the land.

2009- pond dug and water cistern going in

The spring flows all year, but has seasonal fluctuations of flow which correspond quite directly to local rain fall.  It slows to a trickle during the dry season, and fills up again within a few weeks of our first fall rains.  So we have a huge abundance of water in the winter, but we still have to be careful not to overtax the storage capacity in the summer.  With more gardens being created, and more water facilities in the house up and running, we needed to amend our water system to include more water storage.

We added a 1200 gallon buried concrete cistern at the time that we dug the pond, in 2009.  Our field is solid clay, and so was horrifically wet all winter and the pond helped to redirect the incoming winter moisture.  The concrete cistern overflows into the pond, which overflows towards the garden.  However, the water level of the pond drops below the outfall in June, and so the spilling waterway dries up in the season when we could use it the most.  As the next 6 years went along, we watered the garden by hand (which got to be a bigger and bigger job) and experienced  a few summers of extended hot dry conditions, which proved difficult for the spring. Last April we addressed this by adding 2 plastic above ground tanks, each holding 2,000 gallons, for the prupose of irrigation.  The summer following was another long and dry season, but we had awesome results with keeping plants well watered through drip lines and mulch, using the water we set aside from the spring.  We had to refill them partly in August, setting the refill flow at a slow trickle overnight.  By the time the rains returned in october, our season of growing was less intense and we could turn off the irrigation.

 

Here is a water map of our system as it is functioning at this time.

  1. Underground spring collects into gravel bed and perforated pipe, then gravity feeds to fill the cistern.
  2. Buried concrete cistern holds 1200 gallons, and overflows into the pond.
  3. Water pump in the shop draws water up to the house for our domestic supply.
  4. Water goes through a UV filter.
  5. Outside house tap is turned on to fill the two above ground cisterns using the filtered spring water. (2000 gallons each)

The water is then fed by gravity into the irrigation lines.  A 1″ hose heads to the orchard, where it is split into a 3/4″ line that continues around the pond, and into a 1/2″ line that runs through the orchard.  Drip hoses with either 6″or 12″ spaced drip holes irrigate the rows of cordon espalier fruit trees, and into the various flower, herb, and berry beds.  The veggie garden system is similar, with various drip lines coming off the 1/2″ line.  We dug the 3/4″ line shallowly into the ground around the pond as well as burying the 1/2″ line in places where it crossed paths to avoid damage from stepping on it or tripping.  Two timers are attached to the lines leading into the orchard and leading into the veggie garden, since each area has differing water needs, and shut off valves are placed at the major forks to allow us to manually open or close each section.

The drip system was fairly straight forwards to install after a lesson from islander John Eckfeldt who supplied us with the system.  It is fairly flexible and configurations are easy to adapt for year to year changes.  It works well with a gravity feed, although it is usually affixed to a pressurized system.  Our large tanks are uphill from the gardens by a small degree, so we did some drip tests to see if the volume of water coming from one drip hole was the same as the product indicated, as well as testing out a length of drip line to see if the drip rate was the same after 20 feet.  The timers we bought are also intended to work with less pressure such as gravity provides.

 

 

 

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