Monday, 26 November 2012

Keeping soil and water on the land

Dehydrated land around a gully system (C. Osborn)
I was recently invited to attend a Landscape Literacy course based on Ecosystem Management Understanding (EMU™).  The course was run by Ecologist Dr Hugh Pringle and hosted by the Department of Primary Industries and Fisheries (DPIF) at their property Old Man Plains near Alice Springs.  

Participants were introduced to drainage system ecology, in particular the key patterns and processes that optimise rainfall infiltration and primary productivity, and how these pattern and processes can be damaged.

The course started with an understanding of how important local knowledge is and the value of recording information and issues onto aerial photography to see how they interact with landscape processes. We then went onto the ground and followed a drainage system, sketching where water was coming from, why it was concentrating, where it was going and what damage it was doing. Then we flew over the drainage system to get another perspective.

A key concept of the course was the identification of ‘nick points’ in the landscape. These are places where the landscape has been lowered and therefore attract water. Nick points can be caused by many things including cattle pads, tracks, fence lines and culverts. Because water will always take the path of least resistance it flows to these lowered points. The water no longer spreads slowly over the surface infiltrating to feed grasses. Instead its velocity slowly increases as the nick point becomes a gully that eats back upslope in the direction of water flow. This can dehydrate country around the gully as it effectively drains the surrounding land.

Hugh explained that to properly understand a problem you need to look at it from a variety of scales, including from the top of catchment to the bottom where the plug has been pulled, prioritise action to protect valuable country under threat from approaching gullies and dehydration, and make sure the plug is put back in so the problem doesn’t reoccur.  

Thanks to Centralian Land Management Association (CLMA) and Territory NRM for organising and sponsoring the course.

Acknowledgement: Camilla Osborn, CLMA

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