Murray Irrigation Area Aquatic Ecosystem Monitoring project - M/BUS/86
MDFRC Technical report
60 pages. 1 of 5 reports associated with project see (Murray Irrigation Region Aquatic Ecosystem Monitoring Program; Annual Report for 2006), (Murray Irrigation Region Aquatic Ecosystem Monitoring Program: Annual Report for 2007), (Murray Irrigation Region Aquatic Ecosystem Monitoring Program: 2008 Annual Report) and (Murray Irrigation Region Aquatic Ecosystem Monitoring Program: 2009 Annual Report).
Water quality and river health are integral components of water supply management for the future. If changes in river management operations are to be assessed as part of an adaptive management strategy then a monitoring program that incorporates realistic timeframes is essential. Changes in water quality and river health may be not be easily detected over the short term; it is the longer term, cumulative incremental changes that will shape our river management issues in the years to come. Murray Irrigation Limited (Murray Irrigation) and the Murray- Darling Freshwater Research Centre (MDFRC) have developed a long term joint monitoring project to assess the health of rivers in or adjacent to the Murray Irrigation’s area of operation (Murray Irrigation Region). Pilot Study and Protocol Development The aims of the pilot study were to: Trial the logistics of the proposed sampling program for 20 sites throughout the Murray Irrigation Region; Refine methods for assessing aquatic ecosystem health at sites typical of the area focussing on macroinvertebrates, fish and vegetation. Sustainable Rivers Audit (SRA) recommendations (MDBC 2004) were used, where possible, as minimum guidelines. The outcomes of the pilot study documented in this report are highlighted in eleven recommendations and are the rationale behind the development of the accompanying protocols handbook (Murray Irrigation Region Aquatic Ecosystem Monitoring Program: Protocols Handbook (Gigney et al. 2007)) which details the recommended sites and methods for implementation of the long term monitoring program. Costs and human resource issues prevented sampling at all 20 sites and a revised list of 10 sampling sites selected in consultation with Murray Irrigation. The sites included a reduced number of locations from the Murray, Edward, Wakool, and Niemur Rivers as well as Billabong and Tuppal Creeks. Recommendation: 1. Use the methods described in the protocols handbook (Gigney et al. 2007) to implement a long term aquatic ecosystem monitoring program at ten sites within the Murray Irrigation Region. Physical Attributes Images from photo points were useful for recording gross morphology and condition of each site. They can provide supplementary information to assist with the interpretation of survey data from other components of the program. Reach morphology, site observation and substrate sections of the Australian River Assessment System (AUSRIVAS) habitat assessments (EPA Victoria 2003) were completed for the sites. However, additional surveys measuring depth, current velocity and sediment type would provide valuable supporting data for the water quality, fish and macroinvertebrate components of the program. Flow regimes for each site can be assessed for each field trip using daily discharge data from gauges on the waterways maintained by the NSW Department of Natural Resources (DNR). Recommendations: 2. Establish permanent photo points at each site and record images twice a year in autumn and spring. 3. Establish a permanent transect at each end of the reach and survey depth, current velocity and sediment type twice a year in autumn and spring. 4. Use daily discharge data from the closest DNR gauges to assess site flow regimes. Riparian and Aquatic Vegetation The most effective techniques for assessing large areas of canopy vegetation involve remote sensing, using for example, colour infra red aerial photography or satellite images. However, these techniques are expensive and would require some ground truthing so they have not been included in the current protocols, however their use should be reviewed during the term of the monitoring program Three assessment measures for riparian vegetation were considered; the riparian vegetation assessment component of the Index of Stream Condition (ISC) (White and Ladson 1999), AUSRIVAS (EPA Victoria 2003), and Rapid Assessment of Riparian Condition (RARC) (Jansen et al. 2004). None of these methods by themselves appeared adequate for assessing riparian vegetation within this program. A combination of methods using indicators that reflect the functional aspects of the ecology of the riparian zone would be most appropriate for the requirements of this long term project (that is, using AUSRIVAS guidelines for width, structural composition, exotic vegetation and longitudinal continuity supplemented by RARC guidelines for the assessment of forest debris (leaf litter), regeneration and grazing (Jansen et al. 2004)). Surveys of aquatic macrophyte beds, including emergent and submerged taxa, were conducted in autumn and spring, but submerged taxa were not visible in spring. Recommendations: 5. Establish permanent transects and conduct detailed riparian vegetation surveys every 5 years and consider remote sensing during the term of the program. 6. Describe the composition and map the distribution of the aquatic macrophyte beds each year in autumn. Water Quality Water quality was measured in autumn and spring by diurnal logging of dissolved oxygen (DO), pH and temperature, as well as taking in-situ readings of temperature, DO, pH, electrical conductivity (EC) and turbidity. Differences in in-situ readings of turbidity and EC were useful in describing the water quality of the sites. However, in-situ readings of DO, temperature and pH were influenced by the time of day. There was significant diurnal variation in dissolved oxygen measurements at some sites, particularly in shallow and very slow flowing sites in spring. Diurnal logging of dissolved oxygen, pH and temperature ensures that these parameters can be compared between sites independent of the time of day that the sites are visited. Recommendation: 7. Measure in-situ EC and turbidity, as well as diurnal fluctuations in dissolved oxygen, pH and temperature each year in autumn and spring. Fish Fish surveys were conducted using SRA protocols in winter and spring, but not in conjunction with the other components of the study, and there were inconsistencies in the sites surveyed and the timing of surveys. The winter surveys produced greater catches overall, but Silver Perch, Golden Perch and Murray Cod were under represented. These larger native taxa were caught in greater numbers and at more sites in spring. Recommendation: 8. Conduct fish surveys according to SRA protocols in conjunction with other components of the program twice each year, in autumn and spring. Macroinvertebrates The pilot study focussed on two published methods considered appropriate for use in lowland rivers; 1) AUSRIVAS style sweep sampling (EPA Victoria 2003, Turak et al. 2004), 2) snag-bag sampling (Growns et al.1999). Sampling trials were conducted in all three major in-stream habitats, snags, macrophytes and bare edges to determine the optimum strategy for sampling macroinvertebrates in a consistent manner across all sites and over time. Trials were also conducted to determine the required number of sample replicates to be taken in the field, the efficacy of live sorting versus laboratory sorting, and the percentage of sub-sampling required to optimise sample accuracy within cost limits. Macroinvertebrate identifications were conducted at the family level, where possible. Littoral habitats of rivers in the Murray Irrigation Region are diverse and may include a variety of vegetation (at some sites) and differences in the complexity of edges. Sweep sampling from major habitat types according to their proportional distribution captures the best representation of macroinvertebrate biodiversity at each site. Collecting from a total distance of 12 m ensures that the majority of taxa are collected. Sweep sampling, with laboratory sorting, provides semiquantitative data that can be used to identify shifts in community structure across time. The snag (large woody debris) dwelling macroinvertebrate community is discreet from the littoral community and valuable information would be lost if it were not sampled. Samples of snag fauna collected from a measured area provided quantitative data that can be used to identify changes in community densities across time. To adequately and efficiently capture the biodiversity in these samples, four snags (replicates) were required. Sorting preserved samples in the laboratory will increase the quality and consistency of the data obtained. Although some rarer taxa may be missed with a 300 animal count, it provides a balance between cost and information. Recommendations: 9. Conduct sweep net sampling over a distance of 12 m in the littoral zone - including bare edges and macrophytes in the proportion by which they occur in the sampling reach. 10. Collect snag samples from four snags and treat each sample as a replicate. 11. Preserve all samples in the field and sort in the laboratory in 25% increments until a greater than 300 cumulative animal count is reached.