Developing a reef water quality management plan — case study

What do we know about the threats to the Great Barrier Reef and how to manage them?

We developed conceptual models to assist in showing the key reef components and processes, how the threats impact on them and how we are managing those threats.

To do this, we used existing data and scientific information contributed by research institutions, government agencies, universities, commercial companies and consultants, stakeholders, traditional owners and community members.

We documented our current understanding of the issues facing the reef in the Scientific Consensus Statement 2008 (PDF 1.9 KB). This built on the first scientific consensus published by Baker et al. (2003), and synthesised more than 500 papers reporting on the science behind the reef, including outcomes from environmental research programs. We articulated how we had been managing those issues in the 5-year Reef Water Quality Protection Plan 2003 (PDF 1.8 MB).

In the Great Barrier Reef Outlook Report 2009 (PDF 20 MB), we reported on the status of the reef and its management, and identified the 4 greatest risks to the reef as:

• catchment runoff
• climate change
• development of coastal land
• direct use, including fishing and tourism.

We knew that 95% of the water quality problems in the reef lagoon came from agricultural runoff, particularly:

• nutrients and pesticides from cane-growing properties and other farms
• sediments and attached nutrients from grazing properties.

The scope of Reef Plan 2009 was therefore to address non-point (diffuse) source pollution (different sources that cannot be attributed to one point of dispersal) from broad-scale land use. This included agriculture (cropping, grazing, horticulture and forestry) and other tenures of public land (national parks and reserves).

The water quality in the reef lagoon is mainly impacted by runoff events, which happen more regularly in the tropical wet season than the tropical dry season, and the diffuse source pollutants they carry.

A runoff event during the wet season (Figure 1a) results in loads of nutrients, pesticides and sediments (mainly due to bank, gully and hillslope erosion in cropping and grazing systems) being delivered to the reef lagoon.

Most of the sediments drop out near the coast but finer sediments can travel longer distances and influence light conditions in some areas further offshore. Where light availability improves after the sediment drops out, the more available nutrients encourage the growth of algae in the reef lagoon. Then the water quality gradually improves further away from the coast, towards the mid and outer shelf areas. So the water quality issues associated with catchment runoff are mainly coastal (inshore marine environment).

During the dry season (Figure 1b) when catchments receive little or no rainfall, we observe reworking of the finer sediments in the system by the actions of wind waves and tides.

Looking at the impacts of wet season runoff events in more detail (Figure 2), we can see why poor water quality can slow the recovery of coral reefs and seagrasses from increased catchment loads and other disturbances:

• turbid waters reduce light for photosynthesis in corals and seagrasses
• sediment can smother seagrass, and smother and kill some corals
• herbicides can inhibit photosynthesis
• fungicides and insecticides can impact coral early life cycle stages
• nutrient-related phytoplankton blooms may promote juvenile crown-of-thorn starfish, resulting in adult population outbreaks that can rapidly reduce coral cover
• nutrients and particulate organic matter may result in a dominance of macroalgae over coral
• lack of productive marine herbivores can result in algae-dominated reefs
• turbid waters reduce the depth that coral can grow, and reduce coral photosynthesis and recruitment
• bleaching events and cyclones can rapidly reduce coral cover.

Key concepts:

• Conceptual models
• Stakeholder involvement

See also:

• Developing a water quality management plan — Step 1

What types of specific management goals did we set to protect the aquatic ecosystems (our key community value) in the Great Barrier Reef lagoon?

The Great Barrier Reef is World Heritage listed and has an ecosystem condition of high conservation value, which requires the highest level of protection. It’s very important that we work to protect the coral reefs and areas of seagrasses, which provide habitats for lots of marine species. Figure 3 shows the extensive network of reefs that comprise the Great Barrier Reef and the spatial extent of the shallow and deep water seagrass beds.

Community values

The highly valued aquatic ecosystems in the coral reefs and the lagoon and sea-floor environments represent a key community value for the region. The Great Barrier Reef waters also have high recreational, commercial fishing and cultural and spiritual values, which are not the focus of Reef Plan.

Management goals

Reflecting on the ecological significance of the region, the key management goal is to protect and improve the ecosystems of the Great Barrier Reef waters, with specific goals to protect and improve the identified areas of coral reefs and seagrasses.

Key concepts:

• Community values
• Level of protection
• Management goals
• Stakeholder involvement

See also:

• Developing a water quality management plan — Step 2

Which indicators did we select to protect the aquatic ecosystems in the reef lagoon from loads of nutrients, pesticides and sediments coming from the catchment areas?

From our conceptual models, we obtained multiple lines of evidence for the causes of high loads of nutrients, pesticides and sediments coming from important land uses in the catchment through to their impact on reef water quality and health (Table 1).

Table 1. Relevant indicators selected for Great Barrier Reef to assess and monitor inshore marine condition

We measured each of these indicators in the Paddock to Reef Integrated Monitoring, Modelling and Reporting Program, to evaluate and report on the effectiveness of Reef Plan.

To implement, integrate and report on these indicators, we undertook (Figure 4):

• paddock-scale water quality and economic monitoring and modelling via
• surveying adoption of improved land management practices
• plot-scale rainfall simulations
• water quality monitoring of key pollutants under improved management practices
• catchment-scale water quality monitoring and modelling via
• water flow and water quality monitoring of key pollutants at subcatchment and end-of-catchment sites (to calibrate the catchment models)
• wetland mapping
• remote sensing of groundcover and riparian areas
• marine-scale water quality monitoring and modelling via
• remote sensing of water quality in pollutant flood plumes
• grab sampling of water quality during flood events
• water quality loggers and passive samplers
• seagrass abundance and health monitoring
• coral reef health monitoring.

Key concepts:

• Indicator selection
• Monitoring
• Weight of evidence — multiple lines of evidence
• Weight of evidence

See also:

• Developing a water quality management plan — Step 3

How did we determine water quality guideline values for each of the water quality indicators we selected for the reef lagoon?
We were fortunate that the Great Barrier Reef Marine Park Authority (GBRMPA) had already developed the Water Quality Guidelines for the Great Barrier Reef Marine Park. These guidelines describe the concentrations or guideline values (trigger values) for sediments, nutrients and pesticides necessary for the protection and maintenance of marine species and ecosystem health in the Great Barrier Reef.

To develop the guideline values, the GBRMPA-commissioned study used existing site-specific information for chlorophyll a and turbidity (including consideration of biological effects data and reference site water quality data; refer to De’ath & Fabricius 2008), as well as methods for developing pesticide guideline values in the ANZECC & ARMCANZ (2000) guidelines.

Key concepts:

• Guideline values
• Monitoring

See also:

• Developing a water quality management plan — Step 4

Guideline values were selected for relevant indicators to protect the aquatic ecosystem community value.

Other community values were not the focus of the management plan but in most cases they will be protected by the guideline values selected for aquatic ecosystems because these values will be the most stringent.

At this point, the guideline values became draft water quality objectives with an aim to be met by 2020.

Noting that the longer term ‘goal’ of Reef Plan 2009 was to ensure that by 2020 the quality of water entering the reef from adjacent catchments has no detrimental impact on the health and resilience of the Great Barrier Reef.

In Step 8, these water quality guideline values helped us to derive what the pollutant load levels and management practices should be to meet our water quality objective.

Key concept:

• Water quality objectives

See also:

• Developing a water quality management plan — Step 5

What did the monitoring data show about where our draft water quality objectives were met or not?

Depending on the outcome of this assessment, we had different options:

• if they were met — continue management and monitoring to ensure protection of the marine environment
• if they were not met — ramp up management actions to improve water quality.

We were fortunate to have good monitoring data for some of the key indicators across multiple lines of evidence in the reef lagoon, such as levels of chlorophyll a (an indicator for algal growth; Figure 5) and secchi disc depth (an indicator for water clarity; refer to De’ath & Fabricius 2008).

Some areas in the northern region of the Great Barrier Reef were in close to pristine conditions and the chlorophyll a monitoring data showed that we were maintaining them below the guideline value of 0.45 µg/L associated with this ecosystem of high ecological value.

In some areas of the reef lagoon, the guideline value for chlorophyll a had been exceeded and we did not meet the draft water quality objective. This meant that we needed to improve current conditions to achieve the water quality objective, or to at least start the improvement process back towards the water quality objective by setting, for example, a 5-year management goal for Reef Plan 2009 (refer to Steps 8 and 9).

Key concepts:

• Monitoring
• Weight of evidence

See also:

• Developing a water quality management plan — Step 6

A catchment-scale water quality management plan like this is typically based on current understanding and monitoring and updated every 5 to 7 years. We would not invest in refining the water quality objectives or coming up with additional indicators at this step.

This step is more relevant to management decisions about specific major new discharges (e.g. industrial or mining developments) in areas where relevant understanding and monitoring is not available.

Instead, we looked at improving any information we needed during the life of the plan. We would revise or add indicators, as required, or improve the water quality guideline values as part of the next planning cycle.

Key concepts:

• Monitoring
• Weight of evidence

See also:

• Developing a water quality management plan — Step 7

What could have been done differently to increase the chance of achieving the water quality objectives?

Before we could answer this, we needed to review our existing management strategies and continue with those that were working (e.g. preventing problems from future development).

We used our existing communication mechanisms to engage with our stakeholders (Figure 6) about possible future management strategies or scenarios for the next 5 years and assess their cultural, economic, social and water quality implications. Out of that stakeholder involvement process, we assessed a range of scenarios, and negotiated and prioritised agreed management actions for the next Reef Plan.

As indicated in Step 5, the water quality objectives/guideline values (i.e. the Reef Plan ‘goal’) helped us to derive what the water quality ‘load’ levels and management practices should be to meet our water quality objectives.

Reef Plan 2009 targets for water quality:

• a minimum 50% reduction in annual average total nitrogen loads at the end of catchments by 2013
• a minimum 20% reduction in annual average total sediment loads at the end of catchments by 2020
• a minimum 50% reduction in annual average pesticide loads at the end of catchments by 2013.

Reef Plan 2009 targets for land and catchment management:

• 80% of sugarcane growers will have adopted improved management practices by 2013
• 80% of horticulture producers will have adopted improved management by 2013
• 50% of landholders in the grazing sector will have adopted improved management practices by 2013
• a minimum 50% late dry season groundcover on grazing lands.

Modelling used to compare scenarios

To help assess the water quality implications of our management practice scenarios we undertook paddock and catchment modelling to determine load reductions from improved management practices. For example, if all land managers moved from current poorer practices (D, C and B classes) to best practices (A class). This allowed us to estimate the water quality (load) improvement for each scenario.

Then we determined potential water quality (concentration) improvements in the reef lagoon for each scenario and compared those concentrations with the water quality guideline values. For Reef Plan 2009, we used empirical relationships to convert water quality catchment loads (e.g. dissolved inorganic nitrogen) into water quality concentrations (e.g. chlorophyll a) to compare against the water quality guideline values and calculate the required load reductions.

Typically in this assessment and negotiation process, a range of scenarios are run to cover strategies from current management practices to all ‘A class’ practices, as well as changing existing land uses to less polluting land uses. This allows stakeholders to see and discuss the range of water quality (load) improvements across the scenarios at the same time as discussing the cultural, economic and social implications — supported by any such complementary assessments — of each scenario.

Our negotiations resulted in an agreed set of management actions to improve water quality loads, and hence reef lagoon concentrations, to either meet the water quality objectives or move towards achieving them.

At the same time, our paddock monitoring trials and models allowed us to estimate the most effective management practices and help set management practice targets aimed at achieving the agreed water quality load targets.

Key concepts:

• Monitoring
• Predictive models
• Quadruple bottom line
• Stakeholder involvement

See also:

• Developing a water quality management plan — Step 8

For a catchment-scale water quality management plan, this step is typically done in conjunction with Step 8.

The cultural, economic, social and water quality assessments of all alternative management scenarios were done together and presented to and discussed with stakeholders. This helped us to make a collective decision about what management strategies would be implemented over the life of the plan to achieve or work towards achieving the water quality objectives.

If the assessments showed that the water quality objectives could be achieved and the cultural and spiritual, economic and social impacts were acceptable to stakeholders, then we could continue to Step 10 and implement the management strategy. For Reef Plan 2009, this was achieved in some spatial areas.

For the inshore areas affected by river plumes, we expected a gradual improvement over time. This meant that we had to accept incremental improvements in water quality towards the desired ‘management goals’ (from Step 2) over time by implementing agreed actions in the next 5 years of the plan that were affordable, and culturally and socially acceptable.

Key concept:

• Stakeholder involvement

See also:

• Developing a water quality management plan — Step 9

Over time, we continue to improve the way we develop and implement Reef Plan.

In the first years of Reef Plan 2003, we developed and implemented 10 broad strategies with 65 management actions based on what people were doing at the time. For the second and third reef plans, and continuing on into the next 5 years, we’ve been operating within 3 strategic work areas to implement the plan.

• Prioritising investment and knowledge — using the best science to prioritise where we implement management actions and which are the most cost-effective actions to implement, as well as ongoing research, and prioritising, collaborating, funding, evaluation and synthesising research and monitoring programs, including producing the 5-yearly scientific consensus statement to inform each Reef Plan review.
• Responding to challenge — where the bulk of the work occurs, implementing actions to achieve improvements in water quality and eventually reef health, and working with key stakeholders (farmers and graziers) to help them improve management practices.
• Evaluating performance — measuring our success using the Paddock to Reef Integrated Monitoring, Modelling and Reporting Program.

Our annual report card to stakeholders reports on progress towards our management practice and water quality load targets, as well as reef water quality and health.

As expected, we see improvements in management practices first, then improvements in loads, and then improvements in reef water quality and health.

For nutrient and sediment impacts, these improvements will take 10 years or more because of the historical loads still in the system.

However, reductions in pesticide loads should result in water quality improvements in the receiving waters over the short term.

Great Barrier Reef regional water quality improvement plans

Reef Plan is an example of a well-funded adaptive management strategy to protect one of Australia’s World Heritage sites.

In the same way that Reef Plan is a good example of a catchment-based water quality management plan, it is supported by 6 ‘regional’ water quality management (improvement) plans that are also good examples:

• Burnett–Mary Water Quality Improvement Plan
• Fitzroy Water Quality Improvement Plan
• Mackay–Whitsunday Water Quality Improvement Plan
• Burdekin Water Quality Improvement Plan — including Black–Ross basins (Townsville; mainly urban issues)
• Wet Tropics Water Quality Improvement Plan
• Eastern Cape York Water Quality Improvement Plan.

These 6 plans provide more regionally specific strategies, using Reef Plan as the overarching plan to provide context and address reef-wide issues. These regional plans were first developed between 2002 and 2009 and were updated between 2014 and 2016.

Key concepts:

• Adaptive management
• Monitoring — reporting
• Monitoring
• Stakeholder involvement

See also:

• Developing a water quality management plan — Step 10
• Reef Water Quality Protection Plan