The importance of riparian vegetation in improving water quality

This is the second of a report series about designing a market based instrument to address water quality issues in the Fitzroy Basin, Central Queensland. There are significant exports of sediment and nutrients from the Fitzroy River each year, with potential impacts on waterways, the estuary, and the Great Barrier Reef lagoon. The bulk of those exports come from non-point sources, principally agricultural land used for grazing, farming and irrigation purposes. Key mechanisms to reduce those exports are to protect riparian areas and to improve ground cover in grazing and farming areas. The focus of this report is the protection of riparian areas and buffer zones as the key strategy to achieve improved water quality outcomes. The key ecological benefits of this strategy would come from three main sources: reduced nutrients directly associated with livestock in riparian areas, reduction in streambank and gully erosion, and increased trapping of sediments and nutrients from overland flows. The extent of ecological benefits from riparian vegetation will vary from site to site, and modelling tools such as Sednet may be useful to predict such outcomes. The opportunity costs of establishing riparian strips fall into two main categories; capital costs (fencing and water) and recurrent costs (production loss and management effort). There are substantial variations according to industry, enterprise and location. When opportunity costs are assessed for different ecological outcomes, the variations will be cumulative, meaning that there will be large variations in opportunity costs to achieve water quality improvements, even between enterprises in the same industry and catchment. Evidence about the benefits of improved water quality in the Fitzroy Basin has been assessed from a number of choice modelling studies that have been performed. The results of those studies show significant values for attributes such as waterway health and estuary health, where water quality is likely to be a key contributor to attribute levels. By association, there are high levels of community value for improving water quality in the Fitzroy Basin. Regulation is one possible approach to improving water quality through better provision of riparian strips. The regulatory approach has been increasingly used since the 1990s to protect remnant vegetation in the catchment. However, it is much more difficult to use regulatory tools to set management actions. Devolved grants and market based instruments offer more flexible means of achieving these outcomes.