Hawkesbury-Nepean River Environmental Monitoring Program

Figure 5.9: Chlorophyll-a levels over time at North Richmond, showing GLM and GAM
predicted values. Records of flow for the Grose River commenced on 19/11/87, so
earlier records for chlorophyll-a could not be modelled when this co-variable was
included in the model.
General conclusions
• GLM and GAM modelling were generally in agreement with the results of
comparisons with ANZECC/ARMCANZ guideline levels (see Comparison of
Water Quality with ANZECC/ARMCANZ (2000) Guidelines above).
• Phosphorus levels (both total and filterable) have generally been declining
throughout most of the river system (with perhaps the exception of the uppermost
site considered: Maldon Weir — site N92). Phosphorus levels downstream of
Penrith STP (e.g. at N53) remain elevated compared with those in many other
areas in the system.
• Nitrogen levels have declined at many sites throughout the river system.
Exceptions to this are Sharpes Weir (downstream of West Camden STP) and
Wallacia Bridge (sites N75 and N67), where nitrogen levels (particularly inorganic
nitrogen levels) appear to be increasing (e.g. see Figure 5.10). Despite many
decreasing trends in nitrogen levels, nitrogen levels often remain above
ANZECC/ARMCANZ guideline levels throughout the river system.
Hawkesbury Nepean River Environmental Monitoring Program: Final Technical Report 21