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 12 Table 2. Measurement and analysis methods for water quality parameters Sample Type Parameter Method Laboratory Field parameters Temperature In-situ, variable resistance thermistor Field method pH In situ, glass electrode Field method Dissolved oxygen In situ, Clark cell or Luminescent DO Field method Electrical conductivity In situ, graphite electrodes Field method Turbidity In-situ, 4-beam turbidity sensor Field method Nutrients NO2 APHA 4500 NO2 I NTEL NO3 APHA 4500 NO3 I NTEL NH3 APHA 4500 NH3 H I NTEL FRP APHA 4500 P G NTEL TN APHA 4500 N C NTEL TP APHA 4500 P B3 G NTEL Major ions Alkalinity APHA 2320 B NTEL Cations (Ca + , Mg 2+ , Na + ) APHA 3120 B NTEL Anions ( Cl , SO4 ,F) APHA 4500-Cl G/B; 3120 B, 4500-F C NTEL pH APHA 4500-H + B NTEL EC APHA 2510 B NTEL TDS APHA 2540 C NTEL Hardness APHA 2340 B NTEL Chlorophyll Chlorophyll a In-house fluorometry method based on APHA standard method CDU 4 Water types 4.1 Introduction and Methods The origin of natural waters is reflected in the ions that are dissolved in the water. For instance, as water passes through an aquifer some of the minerals contained in the rock are dissolved and carried to the surface with groundwater flows. Water from limestone aquifers is typically high in magnesium, calcium and bicarbonate ions, while rainwater contains very low amounts of all major ions. Other rock formations can contain higher proportions of sulphate (e.g. from gypsum deposits) or sodium chloride. Therefore different water types can be identified by comparing the ionic composition of waters. Due to its groundwater origins, the dry season surface water quality of the rivers is strongly related to groundwater quality, which is typically divided into three groups in the region (Karp 2008): Groundwater typical of the Tindall limestone aquifer in the Daly Basin, with low total dissolved solids (TDS), low sodium, chloride and sulphate content. Groundwater with elevated TDS, sodium , chloride and sulphate dominated by Georgina Basin water Groundwater that shows mixing between the two groups. Most of the groundwater in the Mataranka area is from the latter group. To identify different water types, all available dry season major ions samples (n=39) were displayed in a Piper diagram. The Piper diagram plots water quality data according to the proportions of major ions found in each sample. Similar water types plot close together, while those that differ in their composition plot further away from each other.

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