End of Wet Season Stream Flow Measurements, Roper River, May 2014
Kerle, Errol; Waugh, Peter; Northern Territory. Department of Land Resource Management
E-Publications; E-Books; PublicationNT; Aug-14
Early dry season snapshot measurements were taken on the Roper River to establish water quality and quantity conditions at commencement of baseflow conditions. The snapshot measurements are used to: 1. Refine and calibrate the hydrological model used to assess resource availability and allocations. 2. Better define aquifer recharge/discharge zones along the river, and 3. Provide a dataset of comparable flow and water quality measurements at identical periods in the annual water cycle.
Made available via the Publications (Legal Deposit) Act 2004 (NT)
Summary -- Aim -- Introduction -- Observations -- Discussion -- Conclusion -- Recommendations -- References
End of Wet Season Stream Flow Measurement
Northern Territory Government
24 pages : illustrations, colour maps ; 30 cm.
Attribution International 4.0 (CC BY 4.0)
Northern Territory Government
11 Table 1.2 Aquifer Catchment Flows (m3/s) Total Flow (m3/s) Tindall Limestone Little Roper 1.8 3.707 Waterhouse 0.455 Thermal Springs 0.373 Salt Creek 0.006 (approx.) Elsey Creek 1.073 Total Upper Catchment 7.91 A strong correlation is observed between wet season rainfall and early dry season baseflow discharging from the aquifer. High rainfall totals recorded over the 2011 wet season resulted in much higher than average stream flows throughout the 2011 dry season. Lower rainfalls since 2011 has seen a reduction in observed dry season baseflow. Very low rainfall during the 2012/13 wet season did not manifest in very low stream flow probably due to groundwater levels within the aquifer remaining high as a legacy of previous wet season rainfall recharge attenuated within the aquifer. The small amount of recharge from the 2012/13 wet season has possibly contributed to the below average stream flows observed during the May 2014 snapshot measurement, despite rainfall totals recorded over the 2013/14 wet season trending towards average. External factors such as extraction from the aquifer and river may have contributed to the below average flows currently experienced in the Roper River, however consideration of these factors is beyond the scope of this report. Water Quality Electrical Conductivity (EC) Electrical conductivity results vary significantly between discharge points in the Tindall Limestone Aquifer (Figure 6). Within the aquifer there are two main regional groundwater flow regimes that discharge to the river, low Electrical Conductivity (EC) waters (average 800 S/cm) flowing from the North-West and higher EC waters (average 1600 S/cm) flowing from the south. A third localised groundwater source is associated with spring waters emerging from wetland areas along John Hauser Dve, with EC in the 2000 to 5000 S/cm range (G9035200, G9035399). These wetland areas emerge from a localised shallow watertable and groundwater salinity has probably increased due to evaporative concentration (Wagener et al, 2013). As with the October 2013 snapshot measurements, conductivity increased gradually downstream as discharge from the north-west diminishes, and discharge from the South becomes progressively dominant. Also common to the October 2013 measurements, EC peaked around site G9035294 before gradually dropping off throughout the rest of the catchment. Mapping of the aquifer indicates discharge in the vicinity of Red Lily Lagoon (G9030022, G9030023), the last part of the river to receive groundwater discharge from the aquifer, is again from the north-west. This is supported by a dilution of EC levels observed at these points.