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A riffle and pool in Warra Creek, summer. |
Image: Sven Meyer |
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Project summary:
Montreal Indicator 4.1.f involves testing stream biological diversity, through the Australian River Assessment Scheme (AUSRIVAS). This project tested the indicator within Warra and adjacent forests.
The project aims were to assess a range of water quality parameters and to appraise these against various factors relating to forest management. Factors evaluated were roading (stream crossings), logging, inherent stream colour, stream size and stream flow. Turbidity, conductivity, pH and stream temperature were measured fortnightly at a total of 27 sites.
Additional stream water chemical analyses were also determined for summer and winter baseflows and highflow periods. At low and moderate flows, some streams were naturally clear (about 20 CU) while others were highly coloured (about 120 CU). The clear streams have lower turbidity, higher pH, lower conductivity, chloride and sulphate and lower total N and total P than coloured streams. As flow increased, apparent colour changed little in the coloured streams but in the clear and intermediate streams apparent colour approached the levels found in the coloured stream. No significant differences in water quality parameters were detected in comparison of five above- and below-road paired samples, indicating that well constructed roads are effective in minimising detrimental effects on water quality.
Logging impact was considered in relation to time since regeneration. Turbidity levels in recently logged coupes were generally higher than in coupes where regeneration was longer established. Coupes with regeneration greater than three years old were generally at normal levels. High mean and peak turbidity levels were identified in a number of streams.
These were found to be associated with either natural characteristics, or operational practices not consistent with the Forest Practices Code 2000 recommendations. The main causes of adverse turbidity readings were fireline, landing and dam construction. Increased turbidity associated with logging operations is generally short term, limited to the first couple of years after harvesting. Rainfall induces changes in stream flow, resulting in changes to the water chemistry of the stream.
The streamwater concentrations of most ions analysed increased to a peak with the rising water and fell according to discharge. Comparisons of water quality with invertebrate diversity are in progress.
Methodology: Factors evaluated were roading (stream crossings), logging, inherent stream colour, stream size and stream flow.
Turbidity, conductivity, pH and stream temperature were measured fortnightly at a total of 27 sites.
Additional stream water chemical analyses (chloride, sulphate, total N and total P) were also determined for summer and winter baseflows and highflow periods.
Water quality was also compared with invertebrate diversity.
Datasets: None available.
Publications: Meyer, S., Ringrose, C. & Neilsen, W.A. (2002). Testing and refinement of AUSRIVAS for the detection, assessment and interpretation of changes in stream biodiversity associated with forestry operations. Report on water quality at the Warra LTER site and adjacent areas, Rep. No. 05-2002. Forestry Tasmania, Hobart.
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