How do we know we need a 50% reduction in nutrients to our waterways?
Analysis based on the best available information on nutrient loss in catchments has been compiled in the Water Quality Improvement Plans (WQIPs) for the key estuaries and waterways of the Swan and Scott Coastal Plains. These show that the level of nutrients (phosphorus and nitrogen) going into waterways need to be reduced by 30-90% for most catchments. Major estuaries like the Swan-Canning and Peel-Harvey and waterways like the Vasse-Wonnerup and Geographe Bay require at least a 50% reduction in nutrients.
See Water Quality Improvement Plans for more information.
How will we measure progress against the objectives, especially the objective of 50% reduction into waterways?
Measuring progress against water quality objectives is a worldwide challenge. This is because the extent of change in water quality depends on many factors, including the uptake of management practices of different types. Additionally, a large uptake of suitable management practices will not lead to immediate changes in water quality. In other words, there are lags in water quality changes as catchments equilibrate to management changes, and these lags can last many years. It is likely therefore that in the short to medium term, progress will have to be measured using surrogate indicators such as the level of uptake of various management practices, or the exceedance of surrogate indicators such as soil test targets.