CHANGES TO THE MANAGEMENT OF WATER ON GUNNINGRAH
The variability we face on our southern Monaro property is the factor which drove us to make substantial changes to the way we manage water. This applies to both the rain which falls, and the runoff which flows through our land.
The impact of rainfall, and the resulting season’s growth, has a great bearing on our cost of production, and as a result our profitability.
As an example, between two consecutive years, one with good rain and the next with very low recordings, our cost of production doubled for our sheep enterprise, and tripled for the cattle.
Our rainfall records go back to 1918, and a neighbour’s records back to the 1858. As the place where the neighbour’s records are taken is less than 2km from our boundary, I will use them for this exercise.
How variable is the rainfall?
In our area, the annual precipitation over the last 160 years has an average just over 600mm. The range within which the average comprises goes from a low of 250mm to a high of 1200mm.
It is this variability, both within and between years, which causes the problems for farmers planning ahead.
It is very hard to find either annual or monthly patterns. The standard deviations for all data, both monthly and yearly, is very high.
The number of years with rainfall falling within +\-10% of the average is only 33, or less than 20% of the 160 years recorded! The only thing which is noticeable about the data, is that the number of years with above average rainfall are half that of those with below average figures.
DSE* days / hectare / 100 mm of rain, and try to keep this figure in the 300 to 350 range. This enables us to better match the stocking rate with the carrying capacity of the land.
…and through water management
While run off events became rarer due to the grazing management changes, when at times it did happen, damage to streams still occurred. This was firstly, erosion in the stream bed, and secondly, sediment transfer downstream.
To overcome this, we also made changes within the streams on our property, to slow down the rate of flow during such heavy rainfall events.
Along the lines of the Natural Sequence Farming principles, we placed weirs in the upper sections of some streams, with the aim to slow the flow, trap the sediment, and improve the water quality.
The weirs were made from a variety of materials. Ranging from rocks and earth ( the majority ), and others out of old logs, old fence posts, old rolls of fencing materials… whatever suited the spot and was available.
The cost of doing these stream works was really very low. The first stream we tackled was not overly incised, and 20 structures were built at an average cost of just $200. These weirs were all earth and rock, built using an excavator.
Some of the later streams we worked on had much greater incisions, and while costs varied, some structures were up to around $1200, with an average cost of about $500 to $600.
Weir construction in 2006 (left) and the same gully showing significant improvement in 2008 (right).
While it is almost impossible to evaluate a cost / benefit value on the weirs, there are many observable benefits. For the grazing changes, there are observable benefits like the weirs, but also some very quantifiable advantages…
We hope you enjoyed reading Charlie’s story. Tune in next week when he’ll outline the many benefits and advantages he’s received as a result of adopting these regenerative practices.
The Soils for Life Team