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| Coastal imaging |
The coastal zone is under ever-increasing pressure due to development. There is a significant lack of understanding of the interface between tidally varying ocean levels and fresh groundwater that discharges at the coast. This zone is one of the very significant biological diversity and of great importance for fisheries and for many urban populations.
The hydrochemical changes that occur due to incursion of sea water into fresh water are complex and little understood. A very fine balance exists between the pressure of discharging fresh groundwater and the saline ocean water - complicated by the difference in density between the two. This balance is disturbed by floods and high tides and will be impacted in a major way by sea-level rise. The movement of saline interface up river, in response to either sea-level rise or due to surface water abstraction, could also result in significant impacts in this complex system.
Studies by the CWI and the Water Research Laboratory are revealing new processes in coastal zone groundwater connectivity. The CWI and WRL are currently investigating three main issues in coastal zone groundwater connectivity:
1. Overtopping of beach dunes by rising sea levels will increasingly cause contamination of coastal groundwater by higher density salt water. The movement of this density-dependent plume is highly dependent on hydraulic conductivity distribution in the coastal sediments. Fingering of seawater downwards into the fresh water aquifer has been observed but little is understood about the process or the chemical reactions caused by mixing sea water and fresh water. For example, Dr Martin Andersen has been working with a team in Europe to map the impact of flooding of coastal land during a storm event that led to salinisation of a fresh water aquifer (Andersen et al., 2006). Investigations of the potential impact of sea-level rise on Australian coastal aquifers are now being initiated.
2. Coastal sand aquifers can also act as useful natural filters for seawater feed to desalination plants. Recent WRL consulting work (Timms, 2006; Anderson et al. 2005) have provided detailed conceptual designs for a variety of filtered seawater intakes for temporary (1-4 ML/day) and permanent (50 ML/day) desalination plants. Natural filtration of seawater through a suitable sandy aquifer can reduce the impact of construction work in the coastal zone, and decrease operational costs and environmental impacts of desalination plants by providing better quality feedwater.
3. Significant advances have been made in understanding the effect of waves and tides on coastal groundwater levels and flow directions below the beach face. Papers by Turner and Acworth (2004) and Turner (2003) detail groundwater levels can be increased beneath a beach, causing groundwater to flow away from the coastal zone. Water fluxes through beach sands can have significant impacts on coastal erosion processes, currently under investigation by Dr Ian Turner's Coastal imaging @ UNSW team.
Further information: Coastal imaging @ UNSW team.
The hydrochemical changes that occur due to incursion of sea water into fresh water are complex and little understood. A very fine balance exists between the pressure of discharging fresh groundwater and the saline ocean water - complicated by the difference in density between the two. This balance is disturbed by floods and high tides and will be impacted in a major way by sea-level rise. The movement of saline interface up river, in response to either sea-level rise or due to surface water abstraction, could also result in significant impacts in this complex system.
Studies by the CWI and the Water Research Laboratory are revealing new processes in coastal zone groundwater connectivity. The CWI and WRL are currently investigating three main issues in coastal zone groundwater connectivity:
1. Overtopping of beach dunes by rising sea levels will increasingly cause contamination of coastal groundwater by higher density salt water. The movement of this density-dependent plume is highly dependent on hydraulic conductivity distribution in the coastal sediments. Fingering of seawater downwards into the fresh water aquifer has been observed but little is understood about the process or the chemical reactions caused by mixing sea water and fresh water. For example, Dr Martin Andersen has been working with a team in Europe to map the impact of flooding of coastal land during a storm event that led to salinisation of a fresh water aquifer (Andersen et al., 2006). Investigations of the potential impact of sea-level rise on Australian coastal aquifers are now being initiated.
2. Coastal sand aquifers can also act as useful natural filters for seawater feed to desalination plants. Recent WRL consulting work (Timms, 2006; Anderson et al. 2005) have provided detailed conceptual designs for a variety of filtered seawater intakes for temporary (1-4 ML/day) and permanent (50 ML/day) desalination plants. Natural filtration of seawater through a suitable sandy aquifer can reduce the impact of construction work in the coastal zone, and decrease operational costs and environmental impacts of desalination plants by providing better quality feedwater.
3. Significant advances have been made in understanding the effect of waves and tides on coastal groundwater levels and flow directions below the beach face. Papers by Turner and Acworth (2004) and Turner (2003) detail groundwater levels can be increased beneath a beach, causing groundwater to flow away from the coastal zone. Water fluxes through beach sands can have significant impacts on coastal erosion processes, currently under investigation by Dr Ian Turner's Coastal imaging @ UNSW team.
Further information: Coastal imaging @ UNSW team.