|Ginger beer, passionfruit drink, Watermelon, and a place to enjoy it all|
|Wicking bed design: Dr. Ross Mars. Artwork: Cecilia|
|Curving, 3D garden for children to clamber in. Click to enlarge.|
I nearly cried, I was so happy.
The following ideas solely examine the use of rainfall as a method of irrigation of annual vegetables, small herbs and other shallow rooted crops.
The following data was used in the design process:
• Yasothon in NE Thailand has the annual rainfall of 1350 mm, much of this in the ‘wet’ (winter months).
• There are two extremes – drought in the ‘dry’ from November to March (worst in December and January) and floods in the rainy season April to September.
• Pan evaporation is high in some months. e.g. April, the hottest month, has a daily evaporation of 7mm (220 mm for the month).
• Daily rainfall events typically are less than 10 mm. (If this amount fell in April then only 30% of the water is available as 70% evaporates away).
• The monthly rainfall patterns are in table below.
• There is a high degree of variation in rainfall – both what falls each month and yearly. • There are about 68 rainy days and 297 non-rainy days (historical data since 1952).
Conclusions from data
It is essential to capture rainfall and store it. As evaporation can be high, rainfall events are infrequent and precipitation typically low when it does rain, trapping water in a reservoir that allows plants to pull some of the water as required is an important strategy for irrigation of food plants.
Some variation of a wicking bed is proposed. Essentially, this is:
• Garden bed, with water reservoir built above-ground or below-ground, is lined with water-proof plastic sheeting to hold water. Capillary action enables water to slowly move towards the surface where plant roots can absorb and use effectively.
• A piece of plastic pipe, or other, enables a person to examine water level and top-up as necessary (assuming some water is available from elsewhere).
• Bed retaining by timber or rocks, which ever is available.
• Large stone used to direct rainwater into reservoir, and prevent splash against building walls.
• Small stone placed on bottom of bed to enable spread of water quickly across to all bed. Slotted piping would also help.
• An overflow pipe (or more for large beds) is required to allow excess water to move from the reservoir. Water could be directed by piping or channel to a sump elsewhere where it could be used by other plants.
• Bed will naturally fill with rainfall, as well as from the roof.