Hawkesbury-Nepean River Environmental Monitoring Program

Figure 3.1: Conceptual model for the Hawkesbury-Nepean: schematic representation of
likely impacts of Water Plan Initiatives
• excessive plant growth is an outcome of high levels of nutrient input, exacerbated
by low river flow leading to longer retention times for nutrients, floating
macrophytes and algae; and of reduced physical stress on introduced attached
submerged macrophytes (e.g. Taylor-Wood 2003)
• algal growth and sediment runoff reduce light levels for native attached
macrophytes below critical levels for photosynthesis (Roberts et al. 1999)
• barriers to migration, reduced flows, sedimentation, loss of native in-stream and
riparian vegetation and excessive plant growth reduce habitats for native fish
shelter and reproduction and can favour introduced fish species
• reduced flows, poor water quality, sedimentation, loss of native in-stream and
riparian vegetation and excessive plant growth reduce the habitats available for
food-chain fundamentals such as macro-invertebrates.
Allocation of river zones and relevance to management
For discussion purposes, the catchment has been grouped into six broad zones (see
Figure 3.2), including South Creek, on the basis of river morphology, physical
characteristics (e.g. salinity), biota and the locations of natural and artificial features
such as weirs and tributary inflows. By using Table A1.1 (Appendix 1) the zones can
be related back to the Reaches identified in the Hawkesbury-Nepean Management
Forum (2004) Report.
• Zone 1 represents the saline-dominated areas of the Lower Hawkesbury, from
Wisemans Ferry to the Broken Bay entrance.
• Zone 2 represents the largely tidal (but freshwater) section of the river from
Wisemans Ferry to the junction with the Grose River. This includes areas around
4 Hawkesbury Nepean River Environmental Monitoring Program: Final Technical Report