Map of the Namoi catchment showing waterways, wetlands and locations of water for the environment deliveries made in 2020-21.

As identified in the Namoi catchment: Annual environmental watering priorities 2020–21, the focus of water managers was to support, where possible, native fish populations through:

  • replenishment of water levels in refuge pools
  • providing opportunities for small-scale movement into new habitat
  • improved water quality in river pools.

With no available water for the environment, this outcome relied on natural flow events in tributaries below Keepit, Split Rock and Chaffey dams. To help guide the sharing of natural flow events, water managers provided advice on critical environmental water needs within the NSW drought management response framework.

When water security improved in the Namoi and Peel rivers, environmental flows were used to continue drought recovery.

In autumn, a portion of water for the environment was used to provide a base flow along the 7.5-kilometre length of the Peel River between Chaffey Dam and Woolomin village. The aim of this release was to increase access to food and habitat, and improve the health of native fish and riverine mammals, such as platypus and rakali (native water rat), and enhance opportunities for successful breeding in spring.  

This bar chart and table provide a summary of 1565 megalitres of environmental water delivered in the Namoi catchment during the 2020–21 watering year. Volumes are indicative only. The watering event number on the bar chart and in the table relates to the location number marked on the map.

Bar chart showing water delivery to the Namoi catchment in the 2020-21 water year. 
Watering event number Location Outcomes Start
date
Finish
date
1
Peel Environmental Contingency Allowance
Native fish icon 24 May 2021 03 Jun 2021
Notes: CEW = Commonwealth licensed environmental water; EWA = Environmental water allowance.

The Department of Planning, Industry and Environment, in collaboration with the Department of Primary Industries – Fisheries identified the 7.5-kilometre section of the Peel River immediately downstream of Chaffey Dam to have significant drought refuge value. The absence of base flows and fresh flows in the river for more than 18 months had reduced the availability of food and habitat.

This section is the only refuge in the regulated Peel River that can be supported during prolonged droughts. The limited water available for environmental use during droughts highlights the value of this section of the river for refuge and system recovery. This section of the river supports platypus, rakali (native water rat), turtles and threatened fish species such as silver perch and Murray cod. It also supports other native fish species such as gudgeons, Australian smelt and river blackfish.

A total of 1565 megalitres of water for the environment was released in autumn over a period of 17 days. The joint release with the Commonwealth Environmental Water Holder (CEWH) used 1170 megalitres of Chaffey Dam planned Environmental Contingency Allowance and 395 megalitres of CEWH general security entitlement. This volume represented approximately 31% of the available water for the environment for the 2020–21 water year.

The managed release allowed native fish and platypus to move throughout the river system and find more suitable habitat, including deeper pools, logs and vegetation. The flow improved riverine productivity by flushing carbon and other nutrients off low in-channel sediment bars. This much needed flow replenished food supplies and helped improve the health and condition of native fish before winter. The healthier native fish are when they emerge from winter, the more likely they are to successfully breed during spring.

An improvement in dissolved oxygen levels was also recorded in the largest refuge pool in the regulated Peel River located immediately below Chaffey Dam.

Chaffey Dam to Dungowan water supply pipeline Stage 2

Peel River before environmental water flow shows no water in river.

Peel River during environmental water flow.

After years of drought and cease-to-flow conditions in the Peel River downstream of Chaffey Dam, the river had retreated to a series of disconnected pools.

As a drought response to secure town water supply for Tamworth, the minimum daily flow rule from Chaffey Dam had been suspended since November 2019 and authorisation given to WaterNSW to deliver water to Tamworth via a pipeline. This authorisation was subject to conditions that:

  • allow the pipeline to be used when Chaffey Dam storage is less than 20% of full supply capacity. When the dam is below this threshold, water can be supplied to Tamworth Reginal Council using the pipeline and releases from Chaffey Dam into the Peel River cease.
  • establish a small volume of water accrued daily as an Environmental Contingency Allowance to support habitat for fish and platypus when releases stop from Chaffey Dam. This allowance volume was managed by the Peel Environmental Water Technical Advisory Group.

Using expert and local knowledge, the Peel Environmental Water Technical Advisory Group recommended release of the available accrued 61.5 megalitres over 4 days from 30 July 2020 to reconnect pools. The release was successful. It restored flow along the 7.5-kilometre section of river and replenished river pools that provided important drought refuge for local populations of platypus, rakali, turtles and threatened fish species such as silver perch and Murray cod.