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The Importance of Surface Water- Groundwater Interaction in Australia by Dr Richard Evans May 2010

The Importance of Surface Water- Groundwater Interaction in Australia by Dr Richard Evans May 2010. i/wcms/110/01/papers/LWA GW SW Interaction 17052010. Groundwater- The Major Water Resource of the World. Approximate Use 50% Groundwater 50% Surface water

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The Importance of Surface Water- Groundwater Interaction in Australia by Dr Richard Evans May 2010

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  1. The Importance of Surface Water- Groundwater Interaction in Australia by Dr Richard Evans May 2010 i/wcms/110/01/papers/LWA GW SW Interaction 17052010

  2. Groundwater-The Major Water Resource of the World Approximate Use • 50% Groundwater • 50% Surface water But about half of surface water is actually Groundwater i/wcms/110/01/papers/LWA GW SW Interaction 17052010

  3. The World’s Fresh Water i/wcms/110/01/papers/LWA GW SW Interaction 17052010

  4. LWRRDC- GroundwaterProgram What has the LWRRDC/LWA Groundwater Program Achieved? • A very small investment • Dryland salinity • Impact of grassed leguminous pastures on groundwater quality • Diffuse sources on groundwater quality • Introduced GDE’s • Raised profile of SW-GW interaction • Groundwater balances of Australia • Vegetation water use • Initial investment in the Centre for Groundwater Studies i/wcms/110/01/papers/LWA GW SW Interaction 17052010

  5. Types of GDEs i/wcms/110/01/papers/LWA GW SW Interaction 17052010

  6. i/wcms/110/01/papers/LWA GW SW Interaction 17052010

  7. Response of Ecosystem Health to Water Regime i/wcms/110/01/papers/LWA GW SW Interaction 17052010

  8. Groundwater-Surface Water Interaction i/wcms/110/01/papers/LWA GW SW Interaction 17052010

  9. General Principles of SW-GW Interaction • Groundwater and surface water are usually interconnected and interchangeable • GW becomes SW, and SW becomes GW • Not recognised • Results in double accounting and double allocation • Not recognised because of long time lag • Commonly decades 4. In some parts of Australia we have capped SW, but still drill a bore near a river and call it GW and get it licensed i/wcms/110/01/papers/LWA GW SW Interaction 17052010

  10. i/wcms/110/01/papers/LWA GW SW Interaction 17052010

  11. Significance of Double Accounting in Australia 08/09: • Estimated use is 10,000 GL/yr (2,000 GL in MDB) • Double accounting is estimated at 25 to 50% of this use i/wcms/110/01/papers/LWA GW SW Interaction 17052010

  12. When is Double Accounting Important? • Relative to mean annual stream flow, double accounting is usually very small • However double accounting is often important during the flow times of the year and during drought • Hence it is important for low flow planning- ie. environmental flow, drought water supply and security of supply to surface water users i/wcms/110/01/papers/LWA GW SW Interaction 17052010

  13. Surface Water/ Ground Water Interaction-Where is Australia at? • Fundamental concepts still not grasped by key people eg. general denial • Drought has disguised effects of groundwater pumping on stream flow • Virtual complete absence of integral surface water and groundwater management across Australia • National Water Plan (announced January 2007) proposes groundwater to be included in new MDB Cap -silence, and a surge in new licence applications i/wcms/110/01/papers/LWA GW SW Interaction 17052010

  14. Impact of the Fellowship Influential in: • National Policy- NWC Second Bi Annual Assessment • MDB SDL • State Water Resource Assessments • Local licensing approvals and conditions But • Still challenged by many farmers, politicians • Sceptics alive and fighting i/wcms/110/01/papers/LWA GW SW Interaction 17052010

  15. The Future Big Questions in GroundwaterR&D in Australia Energy/Water Nexus in groundwater – honest economies of groundwater compared to the alternatives Aquitard Behaviour- Kv and storage- focus not on aquifers, but more on the limiting factor, the aquitards Recharge change due to climate change– complex and counter intuitive Managed aquifer recharge i/wcms/110/01/papers/LWA GW SW Interaction 17052010

  16. Urban Groundwater Ignored Broad Range of Issues:- • Excessive recharge • Flooding basements • Brackish groundwater intrusion into sewers • Managed aquifer recharge • Urban stormwater harvesting – no allocation ? Or prioritise • Lack of Bank storage schemes • Honest economies – including externalities • S & D use ignored • Over exploited coastal systems and sea water intrusion i/wcms/110/01/papers/LWA GW SW Interaction 17025010

  17. The Overriding Process is Evapotranspiration • Controls GDE, SW-GW Interactions, recharge and discharge change • Ultimately water management in the world will become ET management (Consumption based, not supply based) i/wcms/110/01/papers/LWA GW SW Interaction 17052010

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