Nitrogen and phosphorus loads may need to be cut by 50%-70% throughout Otago, where 64% of monitoring sites did not meet one or more national bottom lines, including parts of Clutha, according to the reports.
E. coli loads in the same areas may need to be cut by 40%-80% to reach standards suitable for swimming or fishing, and 70% of Otago estuaries suffer from high or very high levels of eutrophication such as toxic algal blooms.
The ORC reports indicated even significant changes in agricultural practice may not achieve the suggested standards and found land use change to be the most significant mitigation in many cases.
"ORC has done a great job in identifying the problems and now they need in turn to do a great job in helping us find solutions," Otago Fish & Game environmental officer Nigel Paragreen said.
"The work is showing a disconnect between what we can achieve under the current system and what we need to achieve to meet national minimum standard ... We are going to have to think about health and social and cultural impacts, it affects all of us and we collectively need to find ways to fix it. What we do to fix it in the agricultural space is good management practice ... From here I think ORC needs to map out a pathway to resolve the issue."
The Resource Management Act requires regional councils to sustainably manage water, but central government has recommended delay due to a commitment to changing the national policy statement for freshwater management.
"Regional councils are saying they have issues they need to address now, and different councils have different views, but to date they’ve voted that they want to move ahead," Mr Paragreen said.
