The CSIRO/Bureau of Meteorology 2012 State of the Climate report highlights a trend for “increased spring and summer monsoonal rainfall across Australia’s north; higher than normal rainfall across the centre, and decreased late autumn and winter rainfall across the south.” It also notes that despite higher than average rainfall totals across 2010 and 2011, southwest Western Australia received lower rainfalls and has experienced long-term reductions in rainfall during the winter half of the year.
With rainfall patterns changing, how each drop received is conserved and used is critical.
As discussed in earlier posts the structure of soil is imperative to maximise efficient infiltration and capture of water. This is important not only to sustain vegetation during periods of low rainfall and extreme heat like we’re currently experiencing, but also to better absorb water during high rainfall events. (Remember the “inland sea” floods last year? What difference could properly structured soils founded on optimum organic carbon levels have made?)
Conserving water where it falls
The greatest potential for improvements in conserving water and using it intelligently can be found in increasing infiltration and reducing the current high evaporation rates.
On average, 86% of rainfall initially falls on Australian soils, but around 50% – 25 times the quantity held in all dams – is currently being lost to evaporation.
Consider, that of a typical 100 drops of rainfall that currently fall on the Australian landscape, approximately 12 of these flow into streams and rivers, with only 2 ending up being stored in dams for agricultural, industrial, urban and domestic use. 86 drops fall onto soil, and, on average, 6 of these go into groundwater and 30 into vegetation. The remaining 50 drops are lost to evaporation .
By applying regenerative landscape management practices, our case study farmers have shown that rainfall infiltration can be improved. As a result, any rainfall received is better initially captured and then retained for longer, providing sustained supply to plants and livestock. These regenerative practices have also been demonstrated to help reduce erosion and increase available productive land.
Our case studies show that by managing landscapes to improve the soil and maximise rainfall infiltration and retention, production can be maintained – or even increased – despite variable rainfall.
Next week we’ll look at a couple of these stories in detail, and see the techniques they have applied to achieve these results.
The Soils for Life Team
1. Chatres, C. and Varma, S., 2011, Out of Water: from abundance to scarcity and how to solve the world’s water problems, Pearson Education, p8
2. Foran, B. 2007, ‘Who uses all the water?’, presentation at Water, population and Australia’s urban future: 2007 Fenner Conference On The Environment.