Evaluation of the Decision Version of the Proposed Plan Change 1 policy mix

Report: TR 2020/11

Author: Femi Olubode-Awosola

The Collaborative Stakeholder Group (CSG) conceived the initial version of the Proposed Waikato Regional Plan Change 1 (PC1) as a policy mix intending to achieve short term1 water quality target attribute states (the targets) in the Waikato and Waipā catchments.

The policy mix was simulated using scenario modelling by the Technical Leaders Group (TLG) who provided advice for the CSG deliberation. The policy mix included information on the types and extent of mitigations required to meet the water quality target attribute states. It also provided information on the economic and production impacts of those mitigations and policy.

After PC1 was notified, Waikato Regional Council (WRC) received submissions that were heard by an independent Hearings Panel who then made changes to the policy mix, in the ‘decision version’ reported in Hill et. al. (2020). Using the modelling framework developed by the TLG, an evaluation of the decision version of PC1 was completed and is presented in this report.

Implications for policy implementation and monitoring, as well as possible on farm responses to the policy, were also considered. The aim of this evaluation and report is to contribute to the understanding of various contaminant sources, the mitigation options and the extent to which they can help achieve the water quality target attribute states to meet the objectives of Te Ture Whaimana (the Vision and Strategy for the Waikato and Waipā rivers).

The key finding of this modelling of the decision version is that in both the long term (80-year) and short term (now 20% of 80-year target attribute states in the first 10 years) scenarios, more target attribute states are met than breached. The results suggest the impact is specific to nitrogen (N), and localised in two sub-catchments, Upper Waikato and Waipā Freshwater Management Units (FMUs).

To arrive at the level of achievements reported above, the main assumptions are that some mitigations are adopted among the rural sectors such that some farm types are not expected to remain at their baseline level of nutrient loss profiles. This, together with further mitigation options are reflected in the sectors’ profits and productions. Overall, there is potential loss of about 18% of catchment-level income in the long term scenario, and about 16% in the short term scenario. The difference is not much because most of the targets are achieved and or exceeded even at the short term scenario based on the modelling assumptions.

An on-farm implication is that options to mitigate contaminant losses could be more effective and efficient with advancements in technology that would maintain or improve productivity and profitability. The results of the long term scenario show possible localised increases in concentrations of specific contaminants (“hot spots”) in the catchment. For policy implementation, this suggests that mitigation options should be specific and targeted.

Although time affects the difference between on-farm contaminant loads and concentrations in the rivers, it has not been explicitly incorporated into either this modelling of the decisions version or the original modelling for PC1. Therefore, it is important that WRC’s implementation efforts are focused on monitoring the adoption of the mitigation activities along with monitoring of contaminant concentrations in the river. This has the potential to inform updates to, and/or future reviews, of the plan.