One of the principles that guides permaculture design is to catch and store energy. Water is looked at as a form of energy, for example by storing water high on a slope or above ground to build pressure downstream, or the required necessity to grow plants. Below are four aspects of water wise gardens:
1. Catch and store rain water.
There are many creative options to catching rainwater - analyze your site, use roof tops, decks, driveways, sidewalks, and more. Rain tanks are a handy way to catch water from a roof, however with the large and infrequent rainfall we get in Calgary designing a secondary catchment will help maximize your rainfall as small tanks can fill up quickly. Here are a few things to consider:
Knowing the potential amount of water you can catch allows you to design to maximize the water storage and create an area for excess water to leave if your limited by space. This can be done with the simple calculation below:
**Given that Calgary receives 330 cm of rain each year, how much rain falls on your roof?
_______square feet of roof area x 30 litres per square foot = _______________ litres per year
Using first flush systems are the best practice for capturing water off of roofs. These allow the few millimetres of rain event to be diverted from food gardening to a separate area, such as a a flower garden or fuel growing area.
Designing in-ground water storage may allow you to greatly increase the amount of water you can catch instead of a rain tank depending on your site. This can be done through cistern or by modifying the ground to store water in large rain beds or swales. These work by catching and storing water and getting it in the soil. It is critical that you ensure there is plants around these raingardens to be able to use the water, otherwise you can create stagnant water and a happy home for mosquitos.
Rain Garden: http://www.calgary.ca/UEP/Water/Documents/Water-Documents/Yard_Smart_Rain_Garden.pdf
Rain tank: http://www.basixcertificatecentre.com.au/Rainwater-tank.htm
Wicking Beds: http://www.leafninjas.ca/yasmin_raised_beds.
2. Increase the capacity of your soil to hold water.
By increasing the organic matter in your soil it allows your soil to act as a sponge - further storing more water when it rains and saving it for your plants! Not only does this help catch and store rainwater, it also helps to offset CO2 emissions, providing a win-win for the environment!
There are a variety of techniques for this including green manure/cover crops, mulching, compost and compost tea spray, and avoiding walking all over your garden.
Type of soil and water retention: http://www.noble.org/ag/soils/soilwaterrelationships/
3. Reduce water evaporation from the soil.
Protecting your soil from direct sun and wind will help reduce water evaporation - this can be achieved by a variety of means including wind breaks, mulch, cover crops, ground cover (squash makes an excellent sprawling ground cover!), plant guilds around large trees, even if in desperate times using plastic sheeting (use caution as your soil is unable to breathe then!)
4. Right plants in the right place.
Too many times plants are placed according to their looks and not their function, creating extra thirsty gardens or plants that just won't flourish. Ensure your thirsty plants are located where you have access to plenty of water, and if you do not have that water access choose a plant more tolerant of dryer conditions.
We often hear native plants are always better - however you still need to take into consideration water needs! Birch, blueberries and cranberries need plenty of moisture while roses, sorrel and rhubarb are tolerant or drier conditions.
But what about xeriscaping? These low water designs incorporate plants that require minimal water and can create lovely landscapes. In Calgary, these designs are best placed in areas with minimal access to catching rainwater, potentially near the top of a slope or close to the foundation of a building. However these gardens are not fit for everywhere. Xeriscaping does not catch and store water during large rainfalls - instead the majority of the water runs off, entering our storm water system and adding to the problem of plenty of pavement and buildings in the city. Combine this and Calgary's often infrequent rain (but sometimes quite the amount in a short period) these landscapes do not function well when it comes to really creating a water wise garden - one that catches, stores, and allows water to flourish the plant life.
Water Wise Gardening: http://www.calhort.org/calgary-horticultural-society/resources/waterwise-gardening.aspx
Water harvesting in a permaculture garden: http://permaculturenews.org/2010/03/31/zaytuna-farm-yields/
So what is the moral of the story?
Permaculture principles can help guide you on which type of water catchment to use, where to place it, and how to use it for the greatest advantage to you and your plants. As most gardeners are wrapping up their growing season, they are already thinking about what they will improve on for next year. What type of water wise gardening techniques will you implement for next year?
We would love to see pictures or hear stories of your water catchment techniques at school or home--post them below!