Water and Wellbeing. Groundwater as a key driver of freshwater water ecosystem responses to drought. Institute for Applied Ecology.

Transcription

1 Water and Wellbeing Groundwater as a key driver of freshwater water ecosystem responses to drought Institute for Applied Ecology Dr Jarrod Kath

2 Drought and environmental condition The need to balance water between between social, economic and environmental values acute in drought Need to understand drought responses well to make informed trade-offs Groundwater critical component of drought responses, but not well understood

3 Floodplains and riparian forests Highly valued, often degraded In drought thought to be particularly dependent on groundwater BUT groundwater resources also important for socio-economic values

4 Declining groundwater High GF/A A ratio indicates stress on groundwater and dependent ecosystems From: Gleeson et al Water balance of global aquifers revealed by groundwater footprint. Nature, 488,

5 Three big stressors on forests 1. Groundwater decline increasing 2. Drought frequency increasing in many parts of the world (Dai 2011) 3. Groundwater salinization also an issue important in many parts of the world and parts of southern Murray-Darling Basin General question: What role does groundwater play in forest drought responses?

6 We investigated the importance of groundwater during the millennium drought ( ) at 2 sites in the MDB Condamine Campaspe

7 Condamine Condamine Catchment - poor tree condition and significant GW decline (up to 25m since 1960) 118 sites for river red gum and poplar box Surveyed in 2005, 2008, 2009 and 2012 Tree dieback in the Condamine

8 Ecological response Are there linear or threshold responses to groundwater decline? Declining groundwater depth gradient

9 Tree canopy cover (%) Mean tree canopy condition (%) Results Distinct threshold response m for red gum (90% confidence interval) m for poplar box (90% confidence interval) Consistent finding regardless of method used Groundwater depth (m) Groundwater depth (m)

10 Tree condition Threshold response in tree condition to groundwater depth Declining groundwater depth gradient

11 Campaspe Trends in remotely sensed vegetation across long term drought (2000 to 2009) 475 sites with an average 1 scene every 16 days)

12 Does groundwater influence drought impacts? Expect that drought impacts are worse when forests don t have access to groundwater when groundwater is of poor quality (ie high in salinity) Dead red gum floodplain forests and salinised and acidified creek, Bottle Bend NSW, April Copyright Murray Wetlands Working Group

13 Decline in drought period 2 Decline in drought period 1 Results Access to groundwater does not reduce drought impacts Groundwater depth (m) Groundwater not buffering as expected Groundwater depth (m)

14 Decline in dry period 2 Decline in dry period 1 Results Higher groundwater salinity = intensified drought impacts Groundwater salinity ( (µs/cm) )

15 Forest condition in drought Summary (1) Canopy cover thresholds in areas of deep groundwater Declining groundwater (2) Groundwater salinity intensified drought impacts low high Groundwater salinity

16 Groundwater and drought Different water use trade-offs in drought depending on likelihood of thresholds and diversity of groundwater conditions Preventive measures may be needed if forests are sensitive to thresholds in drought recovery may be difficult More water may be needed in areas where groundwater quality is poor (e.g. saline areas)

17 Water and Wellbeing Groundwater as a key driver of freshwater water ecosystem responses to drought Institute for Applied Ecology Contact Dr Jarrod Kath for more information at jarrod.kath@canberra.edu.au or phone (02)