Very‐broad‐scale assessment of human impacts on river condition

Abstract

1. Management of whole rivers and river catchments requires a comprehensive set of information about river condition and use, both existing and historical, and the links between them at regional, state or national scales. This paper outlines a new approach to the assessment of river condition, using a small team was able to assess 210 000 km of rivers across more than 3 million km 2 of Australia in little more than a year. 2. The approach was driven by a hierarchical model of river function, which assumed that broad-scale catchment characteristics affect local hydrology, habitat features, water quality and, ultimately, aquatic biota. The model provided the basis for selecting important ecologically relevant features that indices should represent. For each reach of each river we derived a biological index and an environmental index based on measures quantifying catchment and hydrological condition, and habitat and water quality condition. Data came from existing state and national databases, satellite images, site measurements and process models. 3. All indices were calculated as deviation from a reference condition, were rangestandardised and were divided into equivalent bands of condition. Amalgamation of index components and of sub-indices was determined by consideration of their ecological effects; for example, general degradation might be additive, but toxic effects of one component would override all others. 4. Several internal and external validation methods were employed, with the all-important validation of the final assessments undertaken by comparison with a similar index based on locally measured data. 5. The environmental assessment classified 14% of reaches as largely unmodified, 67% as moderately modified and 19% as substantially modified by human impacts. The biological assessment based on site assessments and modelled data using invertebrates indicated that 70% of reaches were equivalent to reference condition and that 30% were significantly impaired. Catchment disturbance, elevated sediment and nutrient loads, and habitat degradation all contributed to these results. These impacts have all occurred during the last 200 years (post-European settlement). 6. Partly as a result of the assessments of this study the Australian Government has begun to adopt a more environmentally sustainable approach to broad-scale water management.

Biological changes along the continuum of an agricultural stream: influence of a small terrestrial preserve and use of adult caddisflies in biomonitoring

“…That is, the conditions at a stream site reflect the watershed conditions upstream of that site, and changes in watershed conditions will be accompanied by corresponding changes in stream physicochemistry and invertebrate composition. Many recent studies have supported this assumption (Snelder and Biggs 2002;Townsend et al 2003;Houghton 2007;Norris et al 2007;Paulsen et al 2008). The bases for this assumption, however, are the predictable responses of natural stream conditions to a disturbance, not the responses of a disturbed stream to a small natural habitat.…”

Linking Flow Regime and Water Quality in Rivers: a Challenge to Adaptive Catchment Management

“…Such changes started early, but their effects have become especially profound since the industrial era (cf. Norris et al 2007). …”

Use of the BEAST model for biomonitoring water quality in a neotropical basin

“…However, a methodology, capable of classifying degradation levels and distinguishing a gradient of anthropogenic alterations has long been sought in studies monitoring human impacts on waterbodies (Norris et al, 2007). This study indicates that the BEAST approach may have considerable potential for doing so in tropical waters.…”