Swales Saving Water

Every now and then I borrow The Earth Garden Water Book from the library and dream about the things I could do if I had a block of land. A few months ago I did this and came across swales. I loved the sound of the word and decided I wanted a swale. Unfortunately I read a bit further and discovered a swale is a ditch that follows a contour and catches water which would otherwise just run down the contour and be lost [1]. My small, flat garden won’t be getting a swale any time soon.

Kirsten and Nick at Planting Milkwood have got past the dreaming stage and have designed water into the landscape of their property. This week Geoff Lawton is teaching a three day earthworks course at Milkwood to construct the necessary dams, swales, etc. in order to

harvest that water and divert it across the landscape so that it seeps in gently and slowly, creating places for things to grow, rather than have the water pelting down the cleared gullies on either side of Milkwood, to swell the eroded creek and rush off downstream before the land and the soil has had a chance to benefit from it.

gravity-fed irrigation system in Kenya In 2005 Nadia and Geoff Lawton constructed swales to harvest winter rain in a very arid, saline 10 acres in the Dead Sea Valley, Jordan. Combined with mulching and planting of specifically chosen species, the land was transformed from desert to lush growth. I saw a video of their work at Environment Solutions who found it at Willem van Cotthem’s Desertification blog. The mulch allowed the soil to retain moisture in winter and fungi (mushrooms) began growing where they never had before. Soil micro-organisms were also able to flourish in this moist environment.

The fungi net that is underneath the mulch is putting off a waxy substance which is repelling the salt away from the area and the decomposition [facilitated by the soil micro-organisms] is locking the salt up. The salt is not gone, it’s become inert and insoluble. [2]

The gravity-fed irrigation system in Kenya (pictured above) is similar to a swale and is making previously barren fields flourish with growth. Improved farming techniques, such as how to harvest water using gravity-fed irrigation, are taught to farmers through World Vision’s Farmer Field School [3].

Salinity is a big problem in Australia because farming has replaced deep-rooted original vegetation with shallow-rooted crops and pastures. This causes the water table to rise, bringing dissolved salts up to the surface and making some land too saline to grow anything. The Western Australian Department of Agriculture monitors groundwater levels. In 2006 their monitoring

indicated that groundwater levels (and hence the risk of salinity) are continuing to climb in most agricultural areas.

When it comes to salinity, prevention is the best solution. Once salinity occurs it can be hard to fix. If the salt levels are not too high, salt tolerant species may be planted and over time they may help to lower the water table – the first vegetation planted by the Lawtons in Jordan were salt tolerant species [2]. Implementing rainwater harvesting through swales, as is happening at Milkwood, helps prevent salinity and other problems associated with high water run-off, such as topsoil erosion.

The other thing being planned for Milkwood is strawbale construction for their studio – my favourite building method. There should be more strawbale construction in the world!

=^.^=

References

  1. The Earth Garden Water Book (2004) Trentham, Vic: Earth Garden Books.
  2. Lawton, Geoff & Nadia (2005) Greening the Desert .
  3. “Daniel’s world turns green” (2007) World Vision supporter magazine, Sept, p.18-19.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s