The Great Barrier Reef (GBR) is arguably Australia’s most iconic natural asset. But virtually all of the relevant science indicates that the GBR is in decline. While there has been a significant increase in resources dedicated to the protection of the GBR in recent years, particularly in addressing rural runoff with voluntary practice change programs, it is recognised that these alone will not be enough to meet the water quality targets. Therefore, there is an urgent need to better understand the broad magnitude of investment required and the actions and approaches that are most likely to be cost effective, in order to inform changes to the long-term management of the GBR.

The purpose of the project was to estimate the range of costs of achieving two key regional water quality targets for GBR catchments. This has been done through an assessment of seven policy solution sets, their abatement contributions in meeting the regional targets, and their associated costs. The targets selected were: 

• A 20 per cent reduction in anthropogenic end-of-catchment fine sediment loads for Mackay Whitsunday and Burnett Mary with a 50 per cent reduction in the Fitzroy, Burdekin and Wet Tropics catchment by 2025.
• A 50 per cent reduction in anthropogenic end-of-catchment DIN for Mackay Whitsunday and Burnett Mary catchments and an 80 per cent reduction in the Burdekin and Wet Tropics catchments by 2025. 

In addition, this report also estimates the costs of achieving a number of interim targets (i.e. 50% and 75% of the stated targets). 

The seven policy solution sets for investigation were:

1. land management practice change,
2. improved irrigation practices,
3. gully remediation,
4. streambank repair,
5. wetland construction,
6. changes to land use (including conversion to conservation uses) and
7. improvements in urban stormwater management. 

A consistent process has been used across GBR catchments to evaluate the cost effectiveness of alternative investments for delivering specific regional water quality targets.