Information on surface water and groundwater quantity and quality for the Namoi subregion is documented in this product. The information was captured in November 2015 and used in the evaluation of the potential impact of coal seam gas and coal mining development on water and water-dependent assets.
The Namoi subregion sits within the larger Namoi river basin. The eastern part of the river basin includes three large dams – Keepit, Split Rock and Chaffey. The Namoi River is the primary surface water resource in the subregion.
As of November 2015 coal and coal seam gas development and exploration that may impact water resources are primarily located in the central and eastern parts of the subregion. Detailed information on coal and coal seam gas development is provided in the Namoi subregion coal and coal seam gas resource assessment.
The three large dams in the Namoi river basin have a combined storage volume of 882 gigalitres. The mean water volume stored between 2004-05 and 2011-12 was 233 gigalitres. Water from these dams is used primarily for irrigated agriculture.
The long-term mean annual flow in the Namoi River downstream of Keepit Dam is about 620 gigalitres.
Groundwater accounts show that between 2006 and 2014, there were approximately 10,300 licensed bores across the subregion. The volume of licensed extraction in 2013–14 was 327 gigalitres. However, this includes extraction from sources that sit outside the subregion.
The mean annual groundwater usage from 2006-07 to 2013-14 was 165 gigalitres. The most heavily utilised groundwater sources are in the Lower Namoi and the Upper Namoi.
Groundwater management across the Namoi subregion is undertaken through six water sharing plans prepared by the New South Wales government.
Surface water quality is monitored at 22 gauging stations located across the Namoi river basin. Managed by the New South Wales Office of Water these stations monitor some or all of the following: salinity, turbidity and temperature. Of these gauges there is one (Goangra) with long-term monitoring of salinity and temperature. It is located on the Namoi River below current and potential coal and coal seam gas development.
Between 2002 and 2007, the Namoi Water Quality Project found that the water quality in the Namoi River and its tributaries was generally acceptable for irrigation and other farming activities, although salinity and turbidity values exceeded the trigger set for the protection of aquatic ecosystems by the Australian Drinking Water Guidelines and the National Water Quality Management Strategy .
Based on the salinity of groundwater in the Namoi subregion, groundwater is generally suitable for drinking and irrigation purposes, with small pockets of higher salinity groundwater.