			Home About us Contact

River Health (river + health)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

Can macroinvertebrate rapid bioassessment methods be used to assess river health during drought in south eastern Australian streams?

FRESHWATER BIOLOGY, Issue 12 2008
PETER ROSE
Summary 1Despite significant concern about drought impacts in Australia, there have been no broad-scale studies of drought effects on river health. A severe and prolonged drought has been acting on many streams in south eastern Australia over the past decade. EPA Victoria has undertaken rapid bioassessment (RBA) of over 250 stream reference sites since 1990, providing an opportunity for a before-after-control-impact investigation of drought related changes to macroinvertebrate indices and water quality. This study uses data from 1990 to 2004 to critically evaluate the effectiveness of using RBA methods and indices, which were designed for assessment of human impacts, for monitoring streams during drought. 2Reference stream sites across Victoria (those with minimal anthropogenic disturbances and repeatedly sampled) were classified as being ,in drought' or ,not in drought' using the Bureau of Meteorology's rainfall deficiency definition. Four biological indices (SIGNAL, EPT, Family Richness and AUSRIVAS) were calculated for combined autumn and spring samples for edge and riffle habitats for the selected sites. 3General linear models and paired t -tests were used to detect drought related changes to index and water quality values at state-wide and bioregional scales. Changes in taxa constancy were examined to determine which taxa were sensitive to or benefited from drought conditions. Frequency of site failure against biological objectives specified in the State Environment Protection Policy (Waters of Victoria) (herein termed ,SEPP WoV') before and during drought was also examined to detect changes in a management context. 4Few significant changes in index values were detected for riffle habitat samples. Rates of failure against biological objectives were similar before and during drought for riffle samples. In contrast, edge habitat AUSRIVAS and SIGNAL scores were significantly reduced at the state-wide scale and most indices showed significant declines in the lower altitude forests, and foothills and coastal plains bioregions. 5Generally, more pollution tolerant, lentic taxa replaced sensitive and flow-requiring taxa in edge samples during drought. In contrast, there were few reductions in the taxa of riffle samples during drought. However, many pool preferring, but pollution sensitive taxa occurred more frequently in riffle areas. Hence, the riffle community began to resemble that of pools and edges. This was attributed to decreased flow and increased ,lentic' habitat opportunities in riffles. 6Detection of a drought effect was confined to the edge habitat and site failure could be assigned to drought and anthropogenic impacts, in conjunction or alone. The riffle sampling protocol was resistant to detection of drought effects as samples were only taken when sufficient water was present within this habitat. Therefore, biological changes at sites not meeting policy objectives for riffle habitats can be attributed to anthropogenic rather than drought impacts. [source]

Predicting potential impacts of environmental flows on weedy riparian vegetation of the Hawkesbury,Nepean River, south-eastern Australia

AUSTRAL ECOLOGY, Issue 5 2000
Jocelyn Howell
Abstract Remnants of native riparian vegetation on the floodplain of the Hawkesbury,Nepean River near Sydney, have significant conservation value, but contain a large component of weeds (i.e. exotic species that have become naturalized). A proposal for the introduction of environmental flows required an assessment of potential impacts on 242 native and 128 exotic species recorded along 215 km of the river. The likely effects of frequency, season, depth and duration of inundation were considered in relation to habitat, dispersal season and tolerance to waterlogging. Overseas studies provided only limited information applicable to the study area; however, comparisons with similarly highly modified riparian habitats in New Zealand were instructive. Depth and season of inundation appear to be the variables with the greatest potential for differential effects on weeds and native plants. Because of likely spread of propagules and enhancement of growth under the present nutrient-enriched conditions, environmental flows that would cause more frequent flooding to higher levels of the riparian zone were judged to be of more benefit to weed species than native species, unless supported by bushland management including weeding. Predictions were limited by incomplete data on Hawkesbury,Nepean species, but two types of environmental flow were judged to be potentially beneficial for native water-edge plants, and worth testing and monitoring: first, flows that maintain continuous low-level flow in the river, and second, higher level environmental flows restricted to the river-edge habitat in autumn (the season in which a greater proportion of native species than weed species are known to disperse propagules). In summary, the presence of environmental weeds in riparian vegetation constrain the potential for environmental flows to improve river health. However, with ongoing monitoring, careful choice of water level and season of flow may lead to environmental flows that add to our knowledge, and benefit riparian vegetation along with other river system components. [source]

Valuing New South Wales rivers for use in benefit transfer

AUSTRALIAN JOURNAL OF AGRICULTURAL & RESOURCE ECONOMICS, Issue 4 2004
Mark Morrison
The results from seven choice modelling applications designed to value improved river health in New South Wales are reported. These applications were designed to provide value estimates that could be used, through benefit transfer, to value improvements in the health of other rivers within the state. Because of limitations on the number of rivers that could be valued and populations sampled, a pooled model for use in benefit transfer was also estimated. The results indicate that both use and non-use values were found to exist for all catchments. In addition, value estimates were found to differ across catchments when populations resident within catchments were sampled. However, when populations resident outside catchments were sampled for two of these catchments, value estimates were found to be statistically similar. This indicates the importance of valuing improved river health in specific catchments by sampling populations within catchments. Yet, it also indicates that it is less critical to conduct multiple surveys of residents outside catchments to value improved river health. [source]