Background

In recent years, a great deal of effort has been made by governments and the community to enhance the quality of water flowing out to the Great Barrier Reef (GBR).

Regional Water Quality Improvement Plans (WQIPs) are part of the Queensland and Australian Government’s Reef 2050 Long

Term Sustainability Plan. Their purpose is to bring together the latest science, and identify targeted approaches to tackling water quality issues at a regional level.Reef 2050 states that its long term goal is: “Over successive decades the quality of the water entering the Reef from all sources has no detrimental impact on the health and resilience of the Great Barrier Reef.”

The Wet Tropics landscape has been heavily modified since European settlement, which has caused changes to hydrological connectivity and ecological functions such as material trapping, filtering and diversion. Modifications include large scale land use changes. These have resulted in the generation of greater pollutant loads than would have occurred naturally, particularly in coastal areas.

One of the main consequences of these changes is degraded water quality which poses a significant threat to the health of the Wet Tropics catchment waterways, coastal and marine ecosystems, and the Great Barrier Reef.

The Wet Tropics WQIP adopts two main management strategies:
1. Directly reduce pollutant runoff through farm management practice improvements
2. Restore the ecological function of waterways through ‘system repair’ actions

Water quality issues in the Wet Tropics region

Water supports people, agriculture, animals and plants, and is central to the health of the whole ecosystem as well as our economies and lifestyles.

In the Wet Tropics there are many highly valuable ecological systems, including the internationally recognised Great Barrier Reef World Heritage Area (GBRWHA) and Wet Tropics World Heritage Area (WTWHA). The protection and improvement of water quality sustains economic and social activities and ensures ecological health for present and future generations.

The Wet Tropics WQIP identifies the main issues impacting water quality, waterways and the coastal and marine environment from land-based activities, and prioritises management actions to halt or reverse the trend of declining water quality.

Specifically, the plan:

• Describes which pollutants pose the greatest risk to key assets
• Identifies primary pollutant sources and hotspots for pollutant generation and delivery
• Highlights the importance of the region in the crown of thorns starfish phenomenon, one of the major causes of GBR coral mortality
• Defines for the first time, end of catchment pollutant load targets to maintain the coastal and marine values of the region (ecologically relevant targets)
• Identifies catchment waterways of greatest ecological value in the region
• Establishes priority areas for improving or rehabilitating the ecological function and health of these ecosystems
• Identifies the priorities and actions for achieving the proposed targets in the most cost effective manner

The Wet Tropics WQIP is underpinned by a suite of supporting scientific studies.

Priority pollutants and targets

The largest sources of pollutants to the GBR are from agricultural land uses. However, other sources include activities and wastes associated with intensive animal production, manufacturing and industry, mining, rural and urban residential, transport and communication, waste treatment and disposal, ports, harbours and shipping.

The pollutants of greatest concern to water quality in the GBR are sediments, dissolved inorganic nitrogen and photosystem II inhibiting herbicides. Dissolved inorganic phosphorus, particulate nitrogen and particulate phosphorus are also of concern but less is known about the effects they have on the ecosystems in the region. The modelling indicates that a large proportion of the total load in the region is derived from human changes to land use.

Ecologically relevant targets (ERTs) attempt to define acceptable levels of these pollutants to safeguard the reef and to achieve the long-term Reef Plan goal. Based on current evidence, a feasible timeframe for achieving the ERTs is approximately 20 years from now. Beyond this period, other drivers of GBR health such as climate change make gains in water quality improvement difficult to predict.

Management practice options to meet the targets

Modelling of land-use adoption scenarios across the entire GBR has shown that it will be challenging to meet Reef 2050 Long Term Sustainability Plan and the longer-term ERTs with the current suite of agricultural management practices.

Accordingly, research and development to investigate innovative practices as well as extension and incentive programs are critical for implementation of the WQIP over the next 5 to 10 years. Restoration of ecological functions in the floodplain and coastal ecosystems are also expected to be important, although the benefits of these restoration activities are yet to be quantified and have been highlighted as a knowledge gap.

Priorities are also identified among the basins/catchments. Six of the Wet Tropics nine basins have been recognised as very high priority for action to reduce pollutant loads to the GBR, these are the Johnstone, Tully/Murray, Herbert and Russell/Mulgrave.

Social and economic characteristics influence the feasibility of reducing pollutant load reductions in each basin.

Restoring ecological function of catchment waterways and coastal ecosystems

Healthy catchments deliver quality water to the GBR basin as well as build the resilience of the coastal and inshore ecosystems to other pressures such as a changing climate and increased development. Increasing our knowledge about techniques for restoring the function of our waterways and coastal systems is a priority for future research.

The WQIP includes preliminary results of a region-wide assessment of the values and threats to freshwater ecosystems and coastal ecological function and connectivity. The approach provides a spatial planning framework and includes a set of management objectives and responses.

Adopting a holistic approach to water quality management in the Wet Tropics

Implementation Plans have been drafted for each basin in the Wet Tropics region. These contain management outcome targets, management actions, estimated costs, identification of the lead agency or partners, and identification of relative priorities within each basin. Click here to view them.

Implementation of the WQIP will require actions across a range of land uses and the WQIP recommends a combination of:

• Financial incentives
• Extension programs
• Technology change
• Appropriate regulation and policy instruments

In addition it recommends implementation of system repair actions in several phases:

• Planning and consultation
• Implementation of a set of short term (1 to 2 year) ‘no regrets’ system repair projects
• Development of a regional system repair strategy
• Implementation of larger scale priority projects

A monitoring and evaluation strategy has been developed to support the implementation of the WQIP and facilitate an adaptive management approach to the delivery.

On-going revision of the knowledge underpinning the WQIP and the most appropriate management approaches will be critical to ensure that optimal water quality outcomes can be achieved for the region.