Ecological and environmental impacts of large-scale groundwater

development in the Table Mountain Group (TMG) aquifer system

Research context

WRC and DWAF research programme: “The hydrogeology of the TMG aquifers”

1) Understanding occurrence, attributes and dynamics of the TMG aquifer systems

2) Understanding environmental impacts of exploitation from TMG aquifer systems

3) Integration of groundwater in broader water management framework

Objectives for eco-impacts project

• Develop predictive tools, innovative techniques and indicators to assess impact of groundwater abstraction on the environment

• Improve understanding of GDEs in TMG & sensitivity to groundwater fluctuations

• Improve understanding of impact of changing low flows on freshwater ecosystems

Approach

Phase 1: Scoping – inception study, data collation and field study planning (started June 2002)

Phase 2: Field data collection (one year)Phase 3: Analysis of results and assessment

of dependencies of ecosystems on groundwater

Phase 4: Recommendations for the application of current knowledge and critical future research

Determining the study area

Considerations:• Practical/logistical aspects• Existing data and infrastructure• Range of GDEs represented• City of Cape Town project target areas

catchments of the Berg, Breede and Riviersonderend, focusing on the CCT area (Kogelberg to Witzenberg)

Purpose of scoping workshop

• Scope the full range and types of potential ecological impacts of large scale groundwater abstraction from the TMG aquifer

• Identify geographical areas and ecosystems considered likely to be dependent on groundwater

• Prioritise areas for future monitoring and research

Team and potential themes

• Southern Waters

• Umvoto

• CSIR

• Ninham Shand

• UCT

• UWC

• US

• GEOSS

• WCNCB

• DWAF

• Groundwater flow in TMG system

• Determining groundwater contribution to baseflow

• Groundwater use by terrestrial ecosystems

• Ecological role of hydro-geochemistry

• Dependency of wetlands on groundwater

• Knowledge management and spatial databases

Links to CCT pilot study on feasibility for extracting

groundwater from the TMG for

municipal supplies • WRC project wet (July-Aug 2003) and

dry (March-April 2004) season baseline monitoring, including control sites

• WRC project limited monitoring areas• WRC project establish monitoring

protocol that can be continued by CCT project