Closing the Loop: Attributing Water Quality Improvement to On-Farm Action

Surface and groundwater quality is influenced by contaminant losses from the farm, and variation caused by climate and time lags caused by the pathways that contaminants take from farms to waterbodies. Using data from 50 years of national and international studies, we find clear evidence that after controlling for variation, we can attribute a degree of confidence in water quality improvements across New Zealand to actions taken on farm designed to mitigate contaminant losses from farms. The degree of confidence varies, depending on how, when and where data have been collected and is subsequently analysed. As a result, the evidence base spans a wide spectrum, from robust, well-funded farm- and catchment-scale studies that monitor water quality and actions across time and space, to well-intentioned but poorly designed studies that collect limited data at few sites over short periods, making it difficult to attribute observed changes to specific farm actions.

To maximise the likelihood of implementing the right actions to improve water quality a five-step framework has been implemented. The framework is designed for farmers, industry bodies, regulators and the community to use as part of a collaborative catchment process focused on action. The process begins with the establishment of a water quality target (Step 1), which requires a plan to reduce contaminant losses—typically by a specified percentage of current levels. The second step sees the land manager identifying mitigation actions for their farm plan. These actions are selected to mitigate the target contaminants, based on the suitability of actions for their farm. The third step ensures actions are implemented in the right place at the right time. This is determined by understanding the current catchment context and risk of contaminant loss, identifying hotspots of risk (e.g., critical source areas) within the farm, and applying suitable and cost-effective actions to maximise outcomes. The fourth step sees appropriate monitoring put in place to connect what's being done on farms with changes in the receiving water body. The final step assesses the level of confidence that improvements in water quality can be attributed to the implemented actions, after accounting for potential confounding factors such as climate variability and changing production. Where well implemented, this framework is able to manage stakeholder expectations about where and when water quality will improve under both voluntary and regulatory regimes.