August 2015 Update Kamarooka Saltland Reclamation Project

 

Dear People, 

It has been some time since I last wrote with news of Kamarooka. Just because you have not heard from me it does not mean you are no longer loved. I have just been a bit busy with some other things including the day job. I did, however, manage to get out to Kamarooka ('Kamo' as the locals call it) last month for another bore run. I have read the bores 92 times since October 2004 and I am building high expectations in terms of bottles of red wine etc. when we hit the 'tonne'!  Don't worry, you probably have a couple of years to prepare. 

So what is happening out there?  The first thing to note is that, once again, it has stopped raining. After the big floods of 2010 and 2011 we have fallen back into that same pattern we saw throughout the late 1990s and most of the noughties. In fact this year the rainfall is marching along the average for that period. I have given you a graph of Bendigo rainfall to demonstrate all of this (below).     

The 'dry' conditions do not support groundwater recharge. That is there is simply not enough rain to wet up the soil to the point where water will drain to the underlying groundwater.  Faced with this lack of replenishment the watertable continues to fall as water is removed by evaporation from the capillary zone, by transpiration from vegetation, and through a little bit of flow further out into the plains to the north and west.

There are a few interesting things happening out there. We have spoken a lot in the past about how the 2004 plantation has pulled down the watertable. This is self-evident from the hydrograph/s (below) and I will  not go over that story again, at least not in this update. The thing that interests me the most in this last set of readings is the impact that the deepening watertable depression under the trees is beginning to have on groundwater in the adjacent land immediately south of the 2004 plantation (in the region of Fort Kamarooka). 

As the watertable depression beneath the trees continues to deepen groundwater flows into it at a rate that is increasing over time, and in consequence the watertable peripheral to the plantation is falling.  This is what we always hoped for, but very difficult to achieve under a rainfall regime that promotes recharge in cleared land in most years.  

The last time I read the bores, a few months ago, I could see the depression under the trees growing into the adjacent land.  Bore 6, about twenty metres from the plantation was much lower than I anticipated, and bore 5, about 50 metres from the plantation also seemed to record a level a little lower than anticipated. If you look very carefully at the hydrograph (below) you will see that this trend is now very clear. Bore 5 & 6 have 'left the pack' and are almost 5 metres below the land surface. Over the last few months they have fallen much faster than we might have otherwise expected. 

Note: I have included my little cross section (below) to help in understanding the above.

 

 I still have a bit of work to do to get our monitoring back on track. Firstly, bore 7 under the plantation is still blocked with tree roots 5 or 6 metres below the land surface and good old bore 8 is dry (down to 7 metres).  I need to cut the roots in bore 7 and get all the paperwork completed to re-drill bore 8 to a greater depth.  I have the driller organised, I just need to get myself organised to sort out the permit from the water authority. 

The coming year will be interesting in that it is hard to see that we will get sufficient rain to recharge the groundwater and bring the watertable back closer to the surface. The only way that might happen is with a large storm similar to the one we experienced in 2007.

You would have to be brave to predict the weather from here on.  On the one hand we have predictions of a 'Godzilla' El Nino, and on the other we have record temps in the Indian Ocean.  A little over half way through September we have received a little over haf the long term average annual rainfall for that month. Too hard to call?

Regards Phil D