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North-west flows in early 2020

Distribution flows and water quality

Read about water balance, supplementary water and water quality.

Water balance

We have prepared a simplified water balance for the period 1 February to 28 April 2020 as shown in the table below. We used measured flow data and estimated the unmeasured inflows for each regulated water source (downstream of the major dams) and in the unregulated Barwon-Darling water source.

This water balance below shows estimated inflows, licenced extractions, system replenishments and flows out from each river system to the downstream water sources. System replenishment includes evapotranspiration, groundwater seepage, instream and wetland replenishment, as well as any measurement error. We also corrected measurements of the end of system outflows if they were affected by water backing up into the tributaries from the high flows in the Barwon-Darling River.

Table 1. Estimated inflows, licenced extractions, system replenishments and flows out from each river system.
Water balanceSystem inflows (GL)1Licensed extractions (GL)2Licensed extractions (% of inflow)2System Replenishment (GL)System Replenishment (% of inflow)System outflows (GL)System outflows (% of inflow)
Border Rivers20110
(QLD: 27)3
Lower Namoi133118%2619%9672%
Macquarie Unregulated     905
Barwon Darling8777Not available 8-Not available 8 491956%

1 Estimated total inflow to the regulated river systems downstream of major storages, 1st February to April 28th.

2 Provides consumptive extraction volumes from the rivers including supplementary water take. Held environmental water usage was 3.7 GL in Gwydir and 4.6 GL in the Macquarie and is included in the system replenishments. The water balance excludes floodplain harvesting activities. That is, any water that was captured on-farm or on the floodplain and did not flow into a river.

3 Queensland extractions for the period 14th to 24th February 2020.

4 Inflows and direct outflows to the Barwon Darling are for the regulated river downstream of Burrendong Dam. The system replenishments presented for the regulated balance are inclusive of flows in Gunningbar Creek (8 GL) and Duck Creek (6 GL) which connect to the unregulated Bogan River system.

5 Marthaguy Creek cumulative flows recorded at Carinda 421011.

6 Bogan River cumulative flows recorded at Gongolgon 421023.

7 Barwon-Darling River inflow estimate includes the outflows from the regulated Border Rivers, Gwydir, Namoi, Macquarie Rivers together with an estimate of the contribution from all other unregulated inflow sources such as the Culgoa, Warrego, Castlereagh, Paroo and Bogan Rivers. The estimate will be refined when further information on extraction volumes is available.

8 The final extraction volumes for the Barwon-Darling were not available at time of publication, due to A class extractions continuing, and the timing of meter reads being scheduled for the end of the water year. The preliminary extraction volume is 230 GL. This table will be updated and republished when the final information is available.

9 Barwon Darling River water balance outflows at Wilcannia Main Channel 425008. This volume will be refined as the Wilcannia and upstream gauges are checked in the field.

Supplementary water

Supplementary water licence holders in the Border Rivers, Gwydir and Lower Namoi valleys had limited periods during February when access was allowed. For more information on each supplementary flow announcements visit the WaterNSW website. The table below shows the impact of the pumping restrictions applied in February, comparing the actual supplementary event extractions against an estimate of what could have been made available for supplementary extractions under standard water sharing plan rule operation.

Table 2. Impact of the pumping restrictions applied in February.
Water sourceFebruary event access (ML)WSP rules potential (ML)% of potential
Border Rivers8,70035,00025%
Lower Namoi2,40057,0004%

1 Includes 3,448 ML held environmental water

2 Includes 1,375 ML held environmental water


A satellite imagery derived assessment of take and water protected in the Northern Basin first flush flows of February 2020.

Download the report (PDF. 1,496KB)

Water quality

Flows that fill remnant river pools and break down pool stratification effects, including low oxygen, provide immediate and long-term water quality benefits. These flows move salt (salinity) and debris (particulate matter and dissolved organic carbon) through the system as well as breaking up algal blooms that may have developed in stagnant water bodies. Flows also provide food (nutrients) for aquatic animal and plant life cycles.

Rain may cause short term water quality problems following drought or bushfire. Sediment, ash and debris washed into waterways can cause rapid drops in oxygen levels and smother habitats. Continuing flows are needed to flush the system, transporting and diluting material, which leads to improved longer-term water quality.

Our Lower Darling releases fact sheets and water quality updates provided regular information as the flows progressed down the Lower Darling River. Before the flows arrived, salinity in the Lower Darling River was high. The flows flushed and diluted poor quality water from isolated remnant pools and significantly reduced salinity levels. Water quality was monitored prior to and during the release to avoid fish deaths in the Lower Darling River. Our key water quality findings for the Lower Darling River release discusses the resumption of flow and water quality in more detail.

Similarly, catchments in the Northern Basin have shown improvements in water quality. Initial data shows that salinity levels along the Barwon-Darling River have improved. For example, salinity dropped from 650 mS/cm at Bourke in early February to 150 mS/cm in late February. The flows also disrupted stratification and resulted in increased dissolved oxygen levels throughout the water column. Flows also dispersed a number of algal blooms that were present in the system.