Continuous Water Quality Data
How MHL Collects DataThe Water Quality Baseline Data is centred around a network of sites located along the New South Wales coast. These sites either telemeter information to the MHL central computer or are stand-alone sites that log data internally and the data is down-loaded to the computer centre when the instrument is returned to MHL. Telemetered data has the advantage that the client may view the data when required through the internet, without waiting for the instrument being retrieved from the field.
The program started around 1990 when suitable instrumentation became available to record water quality parameters. The number of sites increased, generally with instruments being deployed for a 12 month period. Some sites are operated for shorter (or occasionally longer periods of time) when a specific project requires such a deployment.
Instrument CalibrationMHL uses Hydrolab instruments which record either internally (data down-loaded when instrument recovered from the deployment) or through a Mace 2000 logger which is telemetered to the MHL central computer system. The stand-alone deployments (internal logging) usually record at 60 minute intervals whilst the telemetered sites record at 15 minute intervals. The parameters recorded by the instruments include:
- conductivity / salinity (derived)
- dissolved oxygen concentration
- dissolved oxygen % saturation
- water level
Water Quality DeploymentThe instruments are left in place for typically a four week deployment. The length of the deployment is determined by the data requirements and the amount of instrument sensor fouling at the site. The instruments are deployed and retrieved by experienced field officers. During the instrument changeovers profiling of the water column is also conducted.
The data is downloaded and processed on MHLs central computer. The telemetered sites are checked regularly during the instrument deployments. The processed data is checked, quality controlled and stored as part of MHLs water quality database.