Hawkesbury-Nepean River Environmental Monitoring Program

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Figure 6.21: Multidimensional scaling ordination of fish communities at Wallacia (light blue), Windsor (orange), Sackville (purple), Mangrove Mountain (dark blue), Penrith Weir Pool (pink), Jackson’s Lane (green) and Devlin’s Lane (red); Hawkesbury-Nepean River Figure 6.22: Multidimensional scaling ordination of fish communities, comparing differences among decades [green = 1990s; blue = 2000s]; Hawkesbury-Nepean River 50 Hawkesbury Nepean River Environmental Monitoring Program: Final Technical Report
Figure 6.23: Length frequencies of bass (left) and carp (right) caught at Wallacia over time; Hawkesbury-Nepean River Trends in algae and cyanobacteria Algae are present in creeks, rivers and wetlands at all times. However, when the environmental conditions for the algae become optimal, the algae grow rapidly and blooms can form. Although many species of freshwater algae proliferate quite intensively in eutrophic waters, they do not accumulate to form dense surface scums of extremely high cell density, as do some cyanobacteria. The toxins that freshwater algae may contain are therefore not accumulated to concentrations likely to become hazardous to human health or livestock (Chorus and Bartram 1999). Cyanobacteria are, however, recognised as a serious water quality problem with regard to both drinking water supply and recreational water use in Australia. The conditions that favour the growth of cyanobacteria and lead to blooms are nutrient enrichment, warm temperatures, and calm, stable water conditions such as those occurring in slowly flowing rivers and thermally stratified lakes. These conditions are often caused by human actions and activities, but they can also be associated with natural climatic cycles that prevail over wide geographical areas. In temperate climates, cyanobacterial dominance is most pronounced during the summer months, which coincide with the period when the demand for recreational water use is highest. Highly variable river flows have always been a regular cyclical feature of the hydrology in a continent with regular droughts, but the regulation of large rivers has led to an overall reduction in flow and flow-duration characteristics (Walker and Thoms 1993; Maheshwari et al. 1995). Prolonged low flows have previously been associated with blue-green algal blooms in the Hawkesbury River between Windsor and Wisemans Ferry. It is believed that prolonged low flows, coupled with point- and diffuse-source nutrient discharges, water temperatures and the associated light Hawkesbury Nepean River Environmental Monitoring Program: Final Technical Report 51
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Hawkesbury-Nepean River Environment
Page 3 and 4:
CONTENTS: BOOKLET Summary..........
Page 5 and 6: Summary Adaptive management require
Page 7 and 8: 1. Introduction The Hawkesbury-Nepe
Page 9 and 10: • local government • other stak
Page 11 and 12: Sackville that have been the site o
Page 13 and 14: Long-term monitoring sites A review
Page 15 and 16: including algal blooms. This presen
Page 17 and 18: Figure 5.1: Long-term sampling site
Page 19 and 20: General observations from these gra
Page 21 and 22: Figure 5.4: Smoothed trend lines fo
Page 23 and 24: are also highly variable in terms o
Page 25 and 26: Water quality trends using statisti
Page 27 and 28: Figure 5.9: Chlorophyll-a levels ov
Page 29 and 30: al. (1999, 2004). Sydney Water rout
Page 31 and 32: N95 Edge Samples N95 Riffle Samples
Page 33 and 34: quality and macroinvertebrate commu
Page 35 and 36: Figure 6.6: Principal components an
Page 37 and 38: Figure 6.8: Average SIGNAL-SG score
Page 39 and 40: Sites upstream and downstream of da
Page 41 and 42: Figure 6.10: Multidimensional scali
Page 43 and 44: Temporal trends in AusRIVAS-based a
Page 45 and 46: Trends in periphytic diatom communi
Page 47 and 48: species did not appear in searches
Page 49 and 50: the average percentage abundances (
Page 53 and 54: . Figure 6.18: Sampling sites for f
Page 55: Hypseleotris were caught only much
Page 59 and 60: Figure 6.24: Chlorophyll-a, total c
Page 61 and 62: Figure 6.26: Temporal differences i
Page 65 and 66: Figure 6.30: Temporal differences i
Page 67 and 68: (e.g. Merismopedia, Phormidium) hav
Page 69 and 70: Macrophytes Large aquatic plants pl
Page 71 and 72: • Two species of weeds, Gymnocoro
Page 73 and 74: ecord for the unregulated Colo Rive
Page 75 and 76: River has changed in the recent pas
Page 77 and 78: Maheshwari B.L., Walker K.F. and Mc
Page 79 and 80: Department of Environment and Clima
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Hawkesbury-Nepean River Environmental Monitoring Program

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