by Chris McLeod
Spring has arrived early this year. As I write this article, I’m sitting out in the food forest writing on a warm, late winter’s evening, supervising the chickens and pondering the future summer season. You see, water is a critical system at the farm here, so it is often on my mind.
The surrounding tall eucalyptus forest doesn’t need watering during summer. Neither do the well-established fruit trees in the food forest. As the top soil deepens, the trees in the food forest age and their root systems become both more extensive and deeper. They don’t need additional watering during the summer as they can access the groundwater.
Now that they are well established and tested, swales on the farm here direct rainwater into the ground water table, without further effort on my part. If the fruit trees’ root systems can access the water table, they’ll have plenty to drink during the long hot summer.
But, what about those plants whose root systems can’t reach the water table? These are mostly the fast-growing vegetable crops. But, it also includes the potentially long-lived fruit trees that are in their first year or two and haven’t yet developed the extensive root systems that enable them to thrive and survive, as well as their companion plants. New garden beds are also thirsty during summer. All those plants require water to either grow or become well established. So, not only do you need to be able to store rainwater in the water table for the food forest, but you also need to have access to a reliable water supply for watering purposes.
Many rural areas do not have a town water supply connection and this is certainly the case at the farm here. To add further complexity, the volcanic loam soil here makes it very difficult to hold water above ground in a farm dam (pond) without an expensive plastic liner, which I’ve noticed are subject to splits and leaks.
Many countries and cultures favour the use of wells from which a person can pump water for their own use from the water table. In theory, it is a good idea, but if everyone around you is also following this strategy, then it is probably a bad idea, because that activity has a dirty little secret: groundwater is not an infinite resource and water tables do actually fall.
Often people aren’t even aware that the water table is falling until the well runs dry. A neighbour of mine who has a well (known as a water bore in Australia), told me that during the drought of the summer of 2008/09, the water bore ran dry after seven minutes of use.
In Australia, there is a preference towards storing rainwater for later use in water tanks that sit above ground. The rainwater is collected on roof tops and is channeled into the water tanks using gravity. The other advantage with these types of water storages is that because the water is at ground level already, it takes very little energy to pump the water to where it is required.
At the farm here there are three separate water storage systems:
- Chicken enclosure. This is a small system with a single water tank and tap, but no pump. In fact this water storage system does not require any ongoing energy at all to supply the chickens all of the water they require for the year as the water moves through the system using gravity;
- Shed. This is a mid-sized system with two connected water tanks, multiple taps, a bush fire sprinkler and a small 12V DC pump; and
- House. This is a large system with three tanks, multiple taps, multiple bush fire sprinklers and two types of mains powered pumps.
A wise man once told me that, when a person considers systems, a good rule of thumb is that: a difference in size is not a difference in kind. That rule of thumb can be seen clearly in the three separate water storage systems because whilst they may vary in size and some of the details, they are essentially all the same system.
The following three videos explain each of the systems in more detail and provides commentary. Feel free to ask questions.