When Drought Hits

Reviewed 25th December 2023

Drought.

• Melbourne is no stranger to drought.  It hits us periodically, but the last one which broke in 2010, lasted 13 years, and we were scraping the proverbial barrel of our usually ample reserves of water (metropolitan reservoirs) towards the end of that period.
• I had taken measures such as installing rainwater tanks to capture run off from my roof, and installed drip line irrigation throughout my garden.  They helped the garden survive, but it was a close run thing.  Water restrictions had been gradually tightened as the drought progressed and eventually personal use was restricted to 155 litres per day.

Low water use techniques.

• Drip line irrigation conserves water by supplying the plant's root zone directly.  To control evaporation a generous layer of straw mulch is placed over the soil and the drip lines.
• Biologically active soil retains water and plant nutrients especially in the root zones of plants, and to maintain this activity, I keep my soil well fed with good quality homemade compost.
• Drip irrigation's only shortcoming is that surplus water drains into the subsoil where shallow rooted annuals, especially short lived vegetables, cannot reach.  I still use drip line irrigation for my perennial plants, including my lawn, and it works really well for them because they have time to develop long roots and can tap into the subsoil's water and mineral resources.
• Vegetables need a better system than drip irrigation when grown in a climate like Melbourne's.  Colin Austin's Wicking Beds have been very successful preserving scarce water resources in Australia and other hot dry regions of the world, and I have used Colin's concept to develop my own version called the Garden Ecobed.

The Garden Ecobed.

• Ecobeds are self watering raised beds containing rich organic soil kept moist using water from a subsoil tank. They provide ideal growing conditions for most annual vegetables and waste very little water.  Only a little gets past mulch covering the soil's surface to evaporate into the atmosphere.  The rest is used by the plants for transpiration and growth.
• Ecobeds need to be watered much less frequently than conventional garden beds in warm and hot weather, and I can keep them supplied with captured rainwater all year round providing I get at least 35mm of rain each month in summer.

Water Supply

• In the warmer months I keep my drip line irrigated plants supplied with mains water and usually set the timers for 2 hours once a week, but in extremely hot and dry conditions, I may need to increase that to 2 days a week or more.
• Mains water, which I use in my drip line irrigated beds, is not ideal for plants since the treatment chemicals contain chlorine and fluorine salts.  They are toxic to the soil biology, and I have to use more compost to compensate.
• Many people in Australia including my wife and I filter our water supplies for drinking and food preparation to remove these chemicals from our diet. 
• After a long hot and dry summer in 2016/2017 my rainwater tanks were dry, and I had to switch to treated mains water.

 

• However, I rigged up a small domestic filter system (above), good enough to remove chlorine from the water, but only delivering about 6500 litres before replacement filter cartridges are required.  
• That's not a lot of water, but if I can get through summer till autumn harvest using my rainwater reserves (as I did in 2016/2017), the Ecobed's water demand drops dramatically.
• It drops because transpiration rates fall as high water demanding crops like climbing beans, pumpkins, cucumbers and tomatoes are harvested, and as the weather begins to cool.
• The 6500 litres of filtered water should more than cover water demand through winter and I only need a small amount of rain to recharge my rainwater tanks ready for the next season.
• However, if I need more than 6500 litres, the decision has to be made whether to shut down the Ecobeds (remove the crops), or pay for expensive replacement filter cartridges.
• Note.....The inline pressure reducer slows the rate of water deliver, but I get a perfectly adequate 2000 litres of filtered water in 10 hours.  This is enough to recharge all 4 of my Ecobed tanks (lasting about 7 days in autumn).