The ecosystem health of the Noosa estuary was graded “B+” in the 2009 Report Card, a slight decrease from the previous year (“A-”), largely due to an increase in turbidity in the system.  This was likely because of a major increase in the amount of freshwater runoff that entered the estuary in 2009 which also caused median salinity to decrease throughout most of the estuary, sometimes to levels half that of previous years.

Since the inception of the EHMP in 2001, fluctuations of total nitrogen (TN) and dissolved inorganic nitrogen (DIN) in the Noosa estuary have been an important driver behind changes to ecosystem health.  The sources of TN fluctuations in the Noosa system were the subject of a project instigated by Noosa Council and Noosa & District Landcare Group in collaboration with the University of the Sunshine Coast, DERM and the University of Queensland. The project findings were reported in 2008/2009, which identified that wind generated re-suspension of nutrient laden sediments and low flushing rates in Lake Cootharaba resulted in the release of nitrogen into upper reaches of the Noosa, the nitrogen inputs from re-suspension far outweighed all other sources.  While a large component of this TN is organic in origin, it is the DIN component that fluctuates in the upper reaches of the estuary.  It was found that sequestered nutrients in Lake Cootharaba sediments are resuspended and incorporated by phytoplankton, thus elevating the measure for the biomass of this parameter; chlorophyll-a (Chl-a).  Despite this, the Noosa estuary remained 100% compliant with Queensland Water Quality (QWQ) guidelines for TN, total phosphorous (TP) and Chl-a in 2007, 2008 and 2009.  

A riparian assessment forms part of the Biological Health Rating (BHR) used in formulating the Report Card grade for estuaries.  83% of the Noosa estuary contains unmodified habitat predominantly found in the upper reaches and on the northern bank. The lower reaches of the estuary are heavily impacted by urban development, especially on the southern side.

Abbreviations glossary | Indicators and methods

ECOSYSTEM HEALTH INDEX (EHI)

The EHI is a measure of the proportion of a reporting zone that complied with the water quality objectives for key indicators monitored as part of the Ecosystem Health Monitoring Program. The water quality objectives are defined in the South East Queensland Regional Water Quality Management Strategy (2001).

• EHI 1 = 100% of area complies with the environmental objectives.
• EHI 0 = 0% of the area complies with the environmental objectives.

BIOLOGICAL HEALTH RATING (BHR)

The Partnership's Scientific Expert Panel has endorsed a change to the BHR in 2006-07 which increase the BHR from 20% to 30% of the Report Card Grade.

The reason for the change is the implementation of the Riparian Assessment Program (RAP) which will comprise 15% of the total grade (half of the BHR). The other BHR indicators will make up the last 15%

The data from the riparian assessment is available as PDF document.