Surface water

This section summarises surface water quality information in the Hunter river basin only. No water quality information was available for the Macquarie-Tuggerah lakes basin.

Surface water quality can be affected by most changes in land cover or land use. The removal of vegetation and creation of bare areas (e.g. for agriculture, roads, quarries, urban development) can lead to soil erosion and changes in suspended sediments, turbidity, phosphorus (P) and nitrogen (N) within waterways. The use of fertilisers and pesticides in agriculture can contribute to elevated N, P and other pollutant levels in runoff. Point-source runoff from intensive animal production and industrial discharge of waste directly to streams impact stream water quality. Stratification of water stored in large reservoirs can alter water temperatures. Draining of low-lying land to reduce water-logging can lead to the development of acid sulfate soils and highly acidic discharges to streams, affecting stream pH.

Coal resource development can impact water quality through changes to runoff following vegetation removal (e.g. areas cleared of vegetation, service roads, and site processing facilities), discharge of mine waters into waterways and leaking of hydrocarbons. Changes in streamflow from coal mining induced groundwater drawdown may also impact surface water quality. Salinity, turbidity, suspended solids, pH, heavy metal and hydrocarbon concentrations are all potentially affected. Key aims of mine water management are containment of runoff on-site and restrictions on mine water discharges to periods when off-site impacts are minimised.

Salinity is measured by the ability of soluble salts to transmit an electric current (electrical conductivity or EC) quantified in microsiemens per centimetre (µS/cm). The focus of this section is EC data because salinity is a significant water quality issue for the region. Coal mines in the Hunter subregion have been identified as potentially significant exporters of salt because the salinity of groundwater pumped from aquifers intercepted by mining excavations can significantly exceed that of the rivers to which it is discharged.

Since 2007, DPI Water has been routinely monitoring ambient water quality across the Hunter river basin as part of the State Water Quality Assessment and Monitoring Program (SWAMP). Monthly monitoring of temperature, dissolved oxygen (DO), EC, pH, turbidity, total nitrogen (TN) and total phosphorus (TP) is undertaken at nine stream gauging locations in the Hunter river basin. DPI Water does not undertake any monitoring in the Macquarie-Tuggerah lakes basin, but is supplied with water quality data (including EC, pH, turbidity, TP, ortho-P and total oxidised N) collected by Wyong Council at one of its monitoring sites (gauging station number 211009, Wyong River at Gracemere).

Water quality data are collected or held by other organisations. Section provides details of some of the water quality variables that have been collected in the Hunter subregion by different agencies. Analyses of these data are not presented here because the number and frequency of samples and details about the data collection programme are not sufficient to provide meaningful assessments of water quality for these parameters.

Last updated:
18 January 2019