Development of indicators and framework for assessing river health in peri-urban landscapes : a case study of the Hawkesbury-Nepean River system

The main objectives of this thesis are to: (i) examine the concept of river health through views and expectations of stakeholders; (ii) identify and evaluate the key river health indicators related to the main functions and uses of the river system and, (iii) develop a flexible river health assessment framework which can be adapted to other river systems. The Hawkesbury-Nepean River system (HNR), a complex river in peri-urban landscape in south-eastern Australia, is used as a case study to achieve the objectives of this thesis. The first three chapters of this thesis are dedicated to understanding the social implications of river health including its meaning while the remaining chapters progressively explore the key indicators of river health assessment and attempt to develop a simple framework and tools for sustainable management of river health. The analysis of the primary and secondary data collected in this study indicated that water temperature has an important influence on phytoplankton community structure and downstream prawn harvesting (M. macleayi). The community patterns of benthic macroinvertebrates were influenced by water pH. The historical records revealed how the water temperature has significantly increased since the 1980s and it is expected that future rising temperatures due to climate change may have a significant influence on the phytoplanktons and commercially viable fisheries industry in the river system. Aphanocapsa holsatica and Chironomid larvae appeared as the important indicators for upstream and downstream site differences in water quality. A seasonal succession of phytoplanktons indicated that summer, autumn and winter samples were dominated by Cyanophyta, Chlorophyta and a mix of species respectively. As the final stage of this study, a four-step framework (understand, identify, develop and apply) was proposed to assess river systems based on the key findings of this study. The framework starts by understanding the social and environment aspects related to river health. This is further evaluated in conjunction with multivariate statistical methods to identify key indicators to assess river health. Particular attention is given to retain variables that are cost effective, easy to measure and less labour intensive for routine monitoring purposes while providing valuable information on the condition of the river system. Finally, this information is utilised to develop reach specific river health assessment tools addressing the key services of the river system (i.e., irrigation, recreation). The framework developed in this thesis indicates a higher degree of flexibility, as it does not advocate a single method of assessment for rivers in different landscapes, considers local knowledge in great detail and attempts to develop tools for key river uses. Overall, the river water quality data analysed during this study helped in identifying a number of key indicators for routine and rapid monitoring purposes. In particular, selected key indicators were incorporated into a framework and predictive tools for assessing eutrophication and microbial risk for recreational activities