April Update for the NUFG Kamarooka Project
On April 21 I measured all of the Kamarooka bores for the ninetieth time since we first started the project the NUFG saltland reclamation project a little over 10 years ago. It is amazing how different the Kamarooka landscape is now compared with when we first started in 2003. The stark salt-affected land that existed in those days is now covered trees ten metre high. The forest we planted back then is now the stand-out feature in the area, and easily seen from several kilometres distant.
What can we glean from this latest set of results (above)? Firstly, we need to look at the latest numbers in the context of the climate because they reflect the ongoing dry conditions we have experienced over the last few years. Not enough rainfall has fallen to recharge the groundwater system and with continuing evaporation from the capillary fringe, and a little transpiration from the vegetation the watertable continue to fall. The current levels have now surpassed the lowest we previously recorded back in 2009 after 13 years of low rainfall/drought before the record floods of 2010 and 2011.
Watertable fluctuations under the Kamarooka Saltland Reclamation Project
The level of the saline groundwater in the centre of the 2004 plantation has fallen to the point where the bore (bore 8) is now dry. The watertable is now deeper than six metres. The other monitoring bore in the plantation (bore 7) located about 100 metres south of bore 8 is blocked by tree roots growing into the bore screen at a depth of 5 to 6 metres.It too appears to be dry.
The watertable under the plantation was very shallow in 2003 when we started, around a metre below the natural surface and so with levels now deeper than 6 metres the impact of the young forest is very evident. The plantation trees show no signs of stress from the high salinity they experience in their root zone. They continue to produce flourish, producing fresh new growth as they grow taller. The Health of these trees supports our assertion that it is not salt that kills the trees but a combination of salt and waterlogging. With ample leaf area and tree density our plantations stand a very good of avoiding the latter when not inundated for long periods.
Bore 6 is worthy of a mention. It is located on saline land about 20 metres south of the 2004 plantation. The water level within this bore continues to fall in sympathy with groundwater under the plantation. As groundwater flows from the cleared saline landscape into the large watertable depression under the forest it drains groundwater from the surrounding land and lowers the watertable immediately adjacent the plantation. The impact is not readily apparent beyond about 50 metres from the forest boundary, however, it seems the de-watered zone is expanding as the dry conditions prevail.
Dry conditions over the past couple of years have also allowed the remnant native vegetation to re-establish control of the watertable, and the old trees are now out of the danger zone. The shallow watertable at bore 9 in the northern remnants has, once again, been pulled down by the old trees and groundwater in the shallow system is once again about 0.4 metres below the level of the deeper system. The same has occurred under the southern remnants near Hoggs
Road has where the watertable is now a little over 4 metres below the natural surface.
Groundwater levels under the most saline land occur around 3.2 metres below the land surface. Again, the only other time we have seen this was in 2009 after 13 years of below average rainfall conditions.
The southerly regions appear quite stark as the salt affected land appears as a sea of dead saltbush. The biggest rainfall events and flooding in recorded history occurred in 2010 and 2011, and the Old Man Saltbush simply did not survive. It was not inundation that killed them, it was elevated watertables close to the land surface for several months after the floods. Not all of the saltbush are dead, however, in some areas we (Andy) rolled them in an attempt to promote new growth young stems now emerging from the base of the old plants (attached image).
The next thing on the agenda at Kamarooka is to get a drilling rig on site to establish a deeper well adjacent bore 8 in the centre of the 2004 plantation. I have organised this with the driller, but I have not yet completed the paperwork for the water authority. I will try to do this soon. I also want to have a go at clearing the roots from bore 7 (also in the 2004 plantation). How about an enterprising farmer building me a bore root remover? I need about 2 metres of galvanised pipe that will fit within a 50 mm PVC pipe. One end needs to have a bevel ground on it sharp enough to cut the roots. The other needs to have an internal means of securing a rope without increasing the diameter beyond that which will fit down the bore casing. Any takers?
Saltbush death resulting
from extended periods shallow saline groundwater
following record rainfall and flooding in 2010/2011
Young saltbush regenerating after rolling