Territory Stories

Water Quality of the Roper River 2012 - 2016



Water Quality of the Roper River 2012 - 2016


Schult, Julia; Novak, Peter


E-Publications; E-Books; PublicationNT; 02/2017




Roper River


The aim of this report is to summarise the water quality data collected under four different monitoring programs that have been conducted within the Roper river catchment between 2012 and 2016. A detailed description of the programs is provided in section 3. In particular, the report aims to explore 1. Longitudinal (downstream) changes in dry season water quality 2. Temporal changes in dry season water quality between the early to late dry season 3. Inter-annual differences in dry season water quality 4. Spatial and temporal variations in diurnal patterns of water quality over the dry season 5. Relationship of water quality and discharge over one wet season; Made available via the Publications (Legal Deposit) Act 2004 (NT).

Table of contents

1 Acknowledgments -- 2 Background and Study Aims -- 3 Catchment Description -- 4 Data sources and sampling methods -- 4.1 Data Sources -- 4.2 Sample collection and analysis methods -- 5 Water types -- 5.1 Introduction and Methods -- 5.2 Results and Discussion -- 6 Longitudinal variation in dry season water quality -- 6.1 Introduction and Methods -- 6.2 Results and Discussion -- 6.2.1 Physico-chemical parameters -- 6.2.2 Nutrients -- 7 Seasonal and interannual changes in water quality -- 7.1 Introduction and Methods -- 7.2 Results and Discussion -- 7.2.1 Physico-chemical parameters -- 7.2.2 Nutrients -- 8 Nutrient Loads -- 8.1 Introduction and Methods -- 8.2 Results and Discussion -- 9 Diurnal patterns of dissolved oxygen, pH and temperature -- 9.1 Introduction -- 9.2 Methods -- 9.3 Results -- 9.4 Discussion -- 10 Wet season Water Quality -- 10.1.1 Introduction and Methods -- 10.1.2 Results and Discussion -- 11 Conclusion -- 12 References




Water Quality; Roper River

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Department of Natural Resources Environment and the Arts

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63 page : colour maps ; 32 cm.

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Water Quality of the Roper River 2012-2016 36 8.2 Methods Continuous diurnal measurements of dissolved oxygen, temperature and pH were collected for periods of 24-48 hours from 4 Roper River sites in 2014 and 2015 (project 4), and from 3 different habitats at one site in 2013. In 2014, diurnal data were collected monthly between August and October from Elsey National Park (Site 13, ENP), Flying Fox Station (Site 29, FFS) and Mt McMinn Station (Site 34, MM), in the upper, middle and lower reaches of the Roper River. Additional data from Moroak Station (Site 16, MK) was collected in August 2014 only. In 2015 data was collected monthly from May to November from only the two sites furthest upstream and downstream respectively (ENP and MM). Sondes were positioned in areas with flowing water. Diurnal measurements were recorded at 6 minute intervals using an EXO 2 multi-parameter data sonde (YSI Inc., USA) In 2013 diurnal water quality measurements were collected from three different habitats at Flying Fox station (Site 29, FFS): 1. the main channel, where flow was moderately fast, 2. a large pool upstream of Site FFS with slow flowing water, and 3. within a backwater pool with no visible flow. Patterns of diurnal variation in oxygen concentration are compared between sites and monthly changes in the range of oxygen concentration are examined within sites over the dry season. Single station diel oxygen curves can be used to estimate whole reach rates of photosynthesis (P), respiration (R) and re-aeration (K) (e.g. Odum 1956, Chapra and Di Toro 1991, Webster et al. 2005, Townsend et al. 2011) using a model fitting procedure to derive estimates of P, R and K. Such determinations rely on the assumption that the upstream environment is more or less homogenous in the distribution of primary producers and hydraulic conditions. However, model fitting and parameter estimation for P, R and K were beyond the scope of this report and were not attempted here. Furthermore, these model fitting techniques are only valid for sinusoidal curves with gas transfer velocities of <0.5 m h -1 (Demars et al. 2015) and cannot be applied to some of the sites monitored. 8.3 Results Figure 17 shows typical examples of the diurnal curves of dissolved oxygen saturation, temperature and pH for each of the sites as measured in August 2014. The complete set of monthly figures for 2014 and 2015 is provided in Appendix 4. The dissolved oxygen levels at Elsey National Park and Flying Fox Station followed a typical diurnal pattern with DO minima occurring in the early morning, rising DO during the day, maximum oxygen saturation at approximately 3pm and minimum before sunrise. At Mt McMinn station maximum DO

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