Healthy Waterways Report – we need to invest in our waterways to fix our bay

Healthy Waterways Report – we need to invest in our waterways to fix our bay.

The overall grade for Moreton Bay declined from a C to C-. This is the third consecutive year that Moreton Bay has fallen below its long-term average of a B grade.  < click here to go to the report >

Moreton Bay has been struggling to recover since the drought breaking rain in 2009 caused increased sediment and nutrients to enter the bay from degraded catchments. As a result, the overall grade for Moreton Bay in 2009 declined from a B- to a D.

Most of the pollution transported by the flood was deposited on the western side of the bay, north of the Brisbane River, causing a grade decline in Bramble Bay (D+ to D-). Other zones impacted by the flood plume also declined in grade including Eastern Bay (B to B-) and Eastern Banks (A to A-).

Some zones in Moreton Bay that were not significantly impacted by the flood plume improved in grade. For example, Pumicestone Passage had the greatest improvement (D+ to C+) reversing its decline in 2010 (C+ to D+).  Healthy systems were reslient to the impacts of the flood while those that were unhealthy were not.

Unfortunately despite current efforts by the community, the non-government and government sectors, the condition of SEQ waterways and Moreton Bay continues to decline. Under a business as usual scenario (i.e. we don’t change our ways), loads of key pollutants are expected to grow in the coming decades, particularly as a result of urban development. (see the below diagram that projects the future)  However, rural diffuse loads still significantly dominate the sediment entering the bay.

The problem with diffuse loads was brought into sharp focus during the extreme weather events observed from the 6th to the 16th of January. At that time approximately 1,040,000 tonnes of sediment (equivalent to 30,000 dump trucks of sediment) was discharged into Moreton Bay. Comparisons with recent catchment modelling estimates (from WBM Oceanics) of total mean annual loads of sediment runoff from non-urban areas into the bay indicate that just over 3 times the average annual sediment loads were discharged in this week of wet weather (with a mean annual load of 333,776 tonnes per year) 

Preliminary sediment load estimates for the some of the major catchments are:

344,931 tonnes for the Logan/ Albert system or 10,000 dump trucks of sediment. The average annual loads for the past 10 years in the Logan/ Albert Rivers was 30,000 tonnes. This means that over ten times the average annual sediment average load was discharged in the Logan/ Albert during this week.

676,469 tonnes or 19,000 dump trucks of sediment was generated from the Lockyer Valley.

18,159 tonnes or 520 dump trucks of sediment was generated from the Caboolture catchment.  Source < click here >

A continuation in the decline in the condition of our waterways and Moreton Bay has widespread environmental, economic and social consequences.

Environmental problems are economic, social and cultural problems, particularly for sectors reliant on resource condition to maintain competitiveness and market share. Significant impacts in the longer term could be expected for primary industries, nature-based tourism, the recreational sector, water supply costs, and housing values in some areas. For example: if turnover in nature-based tourism was 20% lower in 2031 because of a decline in resource condition (broadly consistent with studies undertaken elsewhere), the reduction in turnover would be almost $8 billion over the next 21 years; while a 10-20% increase in turbidity (expected change), water treatment costs could increase by in excess of $32 million per annum by 2031. In addition, declining water quality poses potential risks to human health.

The social values alone could justify significant investments in waterway and Bay enhancement. Estimates put social values at almost $4.9 billion over the period to 2031 (present value over $2.0 billion).

We know 70% of the unwanted sediment load is coming from 30% of the catchment. We know gully and stream bank erosion generate 75% of the sediment entering the Brisbane and Logan River.

A Business Case has been put together by state agencies and key stakeholders that contains a suite of actions with a total resource requirement of around $78 million over a three years period. Importantly, it provides a meaningful strategy to manage the major negative consequence of growth in the region (i.e. declining waterway health). Based on the current understanding of the costs of load reductions, the total long-term efficient resourcing requirements are likely to be around $570-620 million over the next 20 years. Based on the values at risk there is a clear economic case for this kind of investment.

All we need to do is make a meaningful investment to fix these problems up. To date the necessary investment required has not been made.




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