WATER QUALITY MONITORING AND INFRASTRUCTURE PROJECT

The Water Quality Monitoring and Infrastructure Project's primary objective was to prepare and then implement a strategy to establish a water quality monitoring program for the coastal catchment of the Peel-Harvey estuarine system that can measure nutrient loads from a monitoring network.

The project concentrates specifically on the on the coastal portion of the whole Peel-Harvey catchment although recognised that any coastal catchment water quality monitoring program must also compliment and support a holistic approach to water quality issues that affect the total catchment.

The WQMP has a strong nutrient focus (predominantly Phosphorus) because nutrient enrichment has a long history in the region and has been recognised as the major environmental issue affecting the ecology of the Peel-Harvey Estuarine System. However, a robust load measuring network will be able to be adapted to measuring other water quality parameters in the future, if need arises.

Funding from the CCI has allowed the Department of Environment to establish a simple modern relatively inexpensive load measuring network located at strategic sites on the Peel-Harvey Coastal Catchment.  A multi-criteria assessment identified and selected monitoring sites based on whether they were at the bottom end of problematic nutrient contributing sub-catchments particularly for phosphorus, have planned or existing restoration works, have existing infrastructure or history of measurement and practically located for access and safety.

Monitoring sites consist of an auto sampler and logger (AS) connected to a floatwell house (FW) with a water level recording logger.  Intake pipes for sample runs from the drain/river bank near a flow control structure e.g. weir or riffle.  The auto sampler takes nutrient samples at programmed intervals based on water level signals from the floatwell which in turn are controlled by a PlaNet derived control files in loggers with tailor-made hydrographs for each drain/waterway.  Each infrastructure coupling of AS-FW is known as a load measuring unit (LMU).  Eleven LMU sites have been established with three major LMUs on the Serpentine, Murray and Harvey Rivers and eight strategically located on secondary sites.

Tightly coupled flow and nutrient sample measurements helps reduce the error and variability in load estimates (Load = flow x nutrient concentration).  Historical load estimates for the Peel-Harvey catchment have been compromised by this error.  Consequently questions regarding nutrient load trends and whether loads are increasing or decreasing cannot be adequately answered.  The improved system will also assist in assessing whether nutrient loads have decreased following restoration activities or improved catchment management practices.  The Water Quality Monitoring network is the backbone to the CCI Decision Support System Model developed providing critical flow, nutrient, and suspended sediment data.  It is also adaptable and will be able to measure a range of future water quality parameters such as metals, salts and other contaminants of concern with a known level of error.

For further details contact the Aquatic Science Branch, Department of Water on (08) 6364 6500.

Text adapted from the abstract submission (Rose, Firth and Fowley, 2005) Development of a new nutrient load monitoring network for the coastal Peel-Harvey Catchment: Understanding the past to chase the future.)