Groundwater Dependent Vegetation (GDV) Community Under Threat from Salinity
Located in the Shire of York, Dell Conservation Reserve is home to beautiful Paperbarks, Flooded Gums and extensive sedgelands as well as fantastic Banksia woodlands and dense Kunzea thickets. Situated around these native flora areas are classic Wandoo and Marri woodlands including a small stand of Jarrah trees. All this is growing in a reserve that is less than 50 hectares in size.
However, once you walk into the heart of the reserve the picture is vastly different. Dead flooded gums and paper barks stand silently due to salt affected soils.
In 2011 The River Conservation Society began a project, funded by Lottery West, to investigate the causes of this salinity and what can be done about it.
The project had a number of aims:
• Describe the GDV occurring on the Dell Conservation Reserve.
• Describe the shallow groundwater hydrology of the reserve.
• Identify the relationship of GDV with depth to groundwater.
• Examine temporal and spatial patterns in shallow ground water quality.
• Discuss the threatening processes for the GDV and identify potential management options for the reserve.
The project has completed to date:
• The establishment of 8 bores across the reserve to monitor water quality.
• Vegetation surveys in different vegetation units that can be used to examine changes in vegetation structure and composition over time.
• Mapping of main vegetation types across the reserve.
• Collection of data measuring groundwater levels, salinity and pH.
Bore data has shown that the depth to groundwater varies greatly across the reserve, from consistently being at the surface to depths of 4 metres. Salinity levels in the groundwater were also highly variable across the reserve, with most occurring in the ‘brackish’ range. pH ranged between 5 (mildly acid) and 7 (neutral) for most sites but dropped to only 3.2 (acid) at one site.
The project’s aim was to establish a baseline of data against which we can assess future changes in hydrology and vegetation to help understand if the salinity issues facing the reserve are stable or worsening. Monitoring of the bores and regular vegetation surveys to detect changes, as well as examining the data collected so far, will help determine the vulnerability of different vegetation types to potential groundwater changes.