2016-02-02 P&O Committee - Item 3 - Attachment 4 - Mary River Environmental Values and Water Quality Objectives

            Mary River environmental values and water quality objectives



                applied as absolute lower limit objectives for DO. – see also section 4.2 of the QWQG. Very high DO
                (supersaturation) values can be toxic to some fish as they cause gas bubble disease.
            5.  DO values for freshwaters should only be applied to flowing waters. Stagnant pools in intermittent streams
                naturally experience values of DO below 50% saturation.
            6.  Wallum/tannin-stained waters contain naturally high levels of humic acids (and have a characteristic brown ti-tree
                stain). In these types of waters, natural pH values may range from 3.6 to 6.
            7.  During flood events or nil flow periods, pH values should not fall below 5.5 (except in wallum/tannin waters) or
                exceed 9.
            8.  Nutrient objectives do not apply during high flow events. See QWQG Section 5 and Appendix D for more
                information on applying guidelines under high flow conditions.
            9.  During periods of low flow and particularly in smaller creeks, build up of organic matter derived from natural sources
                (e.g. leaf litter) can result in increased organic N levels (generally in the range of 400 to 800µg/L). This may lead to
                total N values exceeding the WQOs. Provided that levels of inorganic N (i.e. NH3 + oxidised N) remain low, then
                the elevated levels of organic N should not be seen as a breach of the WQOs, provided this is due to natural
                causes.
            10. Conductivity. Under natural conditions, conductivity is highly dependent on local geology and soil types. The
                Queensland Water Quality Guidelines 2009 (Appendix G) provides information on conductivity values in a set of 18
                defined salinity zones throughout Queensland. For each zone, the Queensland Water Quality Guidelines 2009
                provide a range of percentile values based on data from all the sites within that zone. This provides a useful first
                estimate of background conductivity within a zone. However, even within zones there is a degree of variation
                between streams and therefore the values for the zone would still need to be ground truthed against local values.
            11. Temperature varies both daily and seasonally, it is depth dependent and is also highly site specific. It is therefore
                not possible to provide simple generic water quality objectives (WQOs) for this indicator. The recommended
                approach is that local WQOs be developed. Thus, WQOs for potentially impacted streams should be based on
                measurements from nearby stream that have similar morphology and which are thought not to be impacted by
                anthropogenic thermal influences.
                From an ecological effects perspective, the most important aspects of temperature are the daily maximum
                temperature and the daily variation in temperature. Therefore measurements of temperature should be designed to
                collect information on these indicators of temperature and, similarly, local WQOs should be expressed in terms of
                these indicators. Clearly, there will be an annual cycle in the values of these indicators and therefore a full
                seasonal cycle of measurements is required to develop guideline values.

            Sources:
            The water quality objectives were determined from a combination of documents (and supporting data), including:
            •   Queensland Water Quality Guidelines (2009);
            •   Australian Water Quality Guidelines (2000);
            •   Code of Practice for Antifouling and In-water Hull Cleaning and Maintenance, Australian and New Zealand
                Environment and Conservation Council (1997); and
            •   Transport Operations (Marine Pollution) Act 1995 and Regulations 2008, Queensland Transport.




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Document Set ID: 20002123
Version: 1, Version Date: 21/12/2015