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A longitudinal survey of the water quality of the Katherine and Daly Rivers, May/June 2016



A longitudinal survey of the water quality of the Katherine and Daly Rivers, May/June 2016


Shult, J


Long, C

Issued by

Northern Territory. Department of Environment, Parks and Water Security. Water Resources Division


E-Publications; E-Books; PublicationNT; DEPWS Technical Report No. 43/2020




Katherine River; Daly River; Daly River Catchment


In May and June 2016, a longitudinal survey of almost the entire length of the Katherine and Daly Rivers was undertaken. The primary purpose of the survey was to map the thalweg of the river for hydrodynamic modelling and to collect mesohabitat data. This survey presented an opportunity to also obtain a comprehensive snapshot of the longitudinal variability of water quality, which is presented in this report.


Made available by via Publications (Legal Deposit) Act 2004 (NT).

Table of contents

1. Introduction; 2. Methods; 3. Results; 4. Discussion; 5. Conclusion; 6. References; Appendix 1; Appendix 2.




water quality; groundwater; longitudinal survey; water samples; water monitoring

Publisher name

Northern Territory Government

Place of publication





DEPWS Technical Report No. 43/2020


39 pages : colour maps and diagrams; 30 cm

File type





Attribution International 4.0 (CC BY 4.0)

Copyright owner

Northern Territory Government



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Page content

A longitudinal survey of the water quality of the Katherine and Daly Rivers, May/June 2016 Department of Environment, Parks and Water Security 5 October 2020 Page 27 of 39 NO3 0.00 0.05 0.10 0.15 0.20 0.25 0.30 NH 3 0.00 0.01 0.02 0.03 0.04 0.05 Figure 12. Correlation of NO3 and NH3 concentrations in the Daly River catchment Flora River outlier (NH3 = 176 g/L) not shown. 4 Discussion 4.1 Effects of groundwater inputs on spatial WQ variability The longitudinal variability in water quality observed in the Katherine and Daly Rivers during this survey is predominantly determined by groundwater inputs. Water temperature, pH and conductivity in particular are affected by spring inflows, especially in the middle reaches of the Daly River where the river intersects the Oolloo aquifer and spring inputs lead to sudden increases in temperature and EC and a decrease in pH. While water temperature is influenced by a number of factors that affect the heat budget of the river, including solar radiation, shading, air temperature, wind and evaporation, the effect of the thermal springs is significant, especially during the cooler dry season months. The observed sudden and persistent temperature increase in the middle reaches of the Daly River is likely to be due mainly to thermal spring inputs in the area. Groundwater temperatures in the Oolloo aquifer are stable all year round, ranging from 30-37oC with a median temperature of 32oC (Schult 2018). The area of major groundwater inflow from the Oolloo aquifer to the Daly River extends for some 50 km downstream from the Oolloo Hill Spring (Tickell 2002; 2008; Tickell 2011) where groundwater enters the river continuously through bank springs and river bed seepages. Longer term temperature data collected at a large number of sites in the same reach in 2018/19 confirmed the observed pattern of consistently higher temperatures in the groundwater-affected reaches of the river over the dry season (Dostine, unpublished data). Other factors are less likely to have significantly influenced the observed temperature patterns. Shading by riparian vegetation is minimal in the Daly River which has a consistent width of 50-60 m throughout the study reach. Ambient temperatures and weather conditions were similar throughout the June survey period and are therefore not likely to have been responsible for the observed variability in water temperature in the middle reaches of the river.

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