Development of a Framework for the Sustainable Rivers Audit: A report to the Murray Darling Basin Commission

"August 2001".

Project Number: Development of a Framework for the Sustainable Rivers Audit - Project R2004.

MDFRC item.

Preamble The Sustainable Rivers Audit (Audit) is being established to overcome the lack of consistent and detailed information on the health of the Murray-Darling Basin’s rivers. At the Basin scale this lack of information has made it difficult to identify the effectiveness of land and water management or justify major policy initiatives aimed at improving the riverine environment. With water becoming an increasingly scarce and valuable resource, the Basin community seeks assurance that water is being managed according to the principles of ecologically sustainable development. The Audit is being designed to be an annual and comprehensive five-yearly review of the condition of waterways, to inform debate among the Basin community. The Audit will assist the setting and monitoring of valley targets for catchment and river health and provide a trigger to review threats to the rivers of the Basin and, where appropriate, review management actions required to address these threats. Approach Key challenges for the Audit are to assess the existing health of the Basin’s rivers, to detect trends in health through time and predict the long-term ecological consequences of these changes. To meet these challenges, the assessment framework recognises the critical elements and processes that contribute to river health, and develops indices to describe them. Conceptual models of river function have been developed to identify these elements and processes and to assist with the development of indicators. These functional models are based on geomorphic divisions of the river valleys. To detect long-term changes ongoing funding must be committed to the Audit for sampling and reporting repeatedly over a long time-scale. The Audit framework recommends river health be synonymous with ecological integrity, and that river health be measured as the degree to which aquatic ecosystems sustain processes and communities of organisms and habitats relative to the species composition, diversity, and functional organisation of natural habitats within a region. Therefore, the framework has adopted a referential approach for assessing river health for all indicators, where existing site condition is assessed relative to the expected natural condition at that site. The use of a referential approach does not equate with the objective of returning rivers to a pristine condition. It is up to the community to choose both an acceptable level of condition and an appropriate target for river condition. Targets for river health are being developed for the Murray-Darling Basin as part of the Ministerial Council’s ICM Strategy, 'ICM in the Murray-Darling Basin 2001–2010 -Delivering a Sustainable Future’ (MDBMC 2001). There are several State and national programs that report river health in the Murray- Darling Basin. However, existing programs do not fully satisfy the information and reporting requirements of the proposed Audit. A lack of uniformity in assessments and reporting between jurisdictions does not generally allow Basin-wide inter-valley comparisons. Very few programs have on-going funding commitment. Many of the sites in existing programs were selected for monitoring the impacts of specific operations and so cannot be used to provide an unbiased assessment of river health at the valley scale. Consequently, while the Audit attempts to build on available data, the collection and analyses of appropriate data will require significant investment in new sites. The Audit framework recognises biota (fish and macroinvertebrates) and biological processes as the fundamental measures of river health and has developed indices for these. The hierarchical model of river health adopted in the proposed framework predicts that the biota are influenced by the condition of landscape and local features within the catchment. Hydrological, habitat and water quality indices have been developed to assess the condition of the landscape and local features that influence the biotic indices. Environmental Themes Protocols have been developed for the following environmental themes; all are based on a referential approach where existing condition is expressed as a difference from natural condition. The environmental themes for which indicators were to be developed were specified in the Project Brief. --Macroinvertebrate Index - it is proposed that AUSRIVAS O/E taxa, using existing models, be used in the first year of sampling and that a more robust form of SIGNAL be developed. After that, scores for both AUSRIVAS O/E taxa and SIGNAL can be used to derive the macroinvertebrate score. To report at the river valley scale it is recommended that the macroinvertebrate index be assessed annually at 30 sites per river valley. --Fish Index - it is proposed that a fish bioassessment protocol be developed as an integral part of the Audit. Much of the background work required to develop a standardised methodology has been done. However, several aspects still require completion and evaluation. This will require dedicated funding and ongoing coordination during the first five-year term. This development can be done as part of the proposed Pilot Audit. --Water Quality Index - it is recommended that two types of physical and chemical water quality indicators of river health be measured: potential modifiers of ecological processes (flow, temperature, SS, nutrients (TP, TN), salinity) and indicators of outcomes of ecological processes (TOC and composition, DO, pH and chlorophyll 'a', alkalinity, residual nutrients (NOx, NH4, DRP)). Reference condition would be based on flow duration condition comparable to that prevailing at the test site at the time of sampling. To report at the river-valley scale it is recommended that the water quality index be assessed annually with 4–6 sampling occasions per year at 18 sites per river valley. --Hydrology Index - it is recommended that a hydrological index be defined in terms of four sub-indices: Mean Annual Flow, Flow Duration Curve Difference Index, Seasonal Amplitude Index, and Seasonal Period. The hydrology index would then be defined as the Euclidean Distance between unimpacted hydrology condition and the condition defined by the four sub-indices in a four-dimensional space. It would be expressed on a scale of 0–1, with 1 being unimpacted. It is recommended that the hydrological index be calculated at least once in each five-year period, with significant events (e.g. significant new infrastructure or environmental releases) triggering a new assessment of the hydrology index. --Physical Habitat Index - it is recommended that physical habitat be assessed at three spatial scales: floodplain (km), channel feature (100 m) and in-channel patches (1 m). The assessment protocol uses a combination of remote sensing and field data collection. The major habitat categories include the vegetation and the geomorphological, and hydraulic characteristics of each habitat type. The protocol includes a separate assessment of processes that either maintain or degrade physical habitat, such as erosion or isolation. An O/E score will be generated for each spatial scale using the E-Ball technique, which requires development. To report at the river valley scale it is proposed that physical habitat be assessed once every five years at 20 sites per river valley. Reporting Scales Natural resource management at the Basin scale requires information on resource condition to be measured and reported at a commensurate scale. The Audit framework is designed to report health at the river-valley scale; Cap compliance is reported at a similar scale. The Audit framework is also designed to report river health within river-valley scales. These reporting scales are defined by areas along a river with similar geomorphology and hydrology. For example, the Valley Process Zone scale reports river health for the upper, mid-slopes and the lowland parts of the river separately. The study design developed for the Audit does not report river condition at a site. Site Selection It is recommended that the Audit should be based on a stratified random sampling design, stratified by geomorphological characteristics (Valley Process Zones). The allocation of sites to Valley Process Zones will be catchment area weighted, which will result in approximately 70% of sites occurring in the lowland parts of the Basin’s rivers. It is recommended that reference sites for each environmental theme be selected (where possible) from the existing pool of 300 reference sites identified for the First National Assessment of River Health (FNARH). The study design described in this report is efficient with respect to the total number of sites sampled; however, it is acknowledged that it will often not be possible to reconcile existing monitoring stations with this approach. There will inevitably be pressure to compromise on the 'randomness’ of sites to include existing sampling stations, and indeed this may be a sensible approach. However, this will impact to varying levels on the precision of the assessment. This report recommends that the Independent Sustainable Rivers Audit Group (ISRAG) review the site selection process undertaken by the jurisdictions as part of the Pilot (and prior to sampling) to ensure a workable compromise between the recommended study design and existing monitoring stations. Sampling Intensity The number of samples required and the frequency of sampling are driven by a number of factors including the magnitude of the desired detectable change, the confidence in detecting that change, the initial condition score, the variability in the indicator and the reporting scale. Existing data sets, augmented with modelled data, have been used to determine the number of samples required to detect a recommended change of 10% for habitat (20 sites per river valley) and mac