Fish & Game and the Environmental Defence Society (EDS) took Horizons to the Environment Court because they did not believe the regional council was implementing the One Plan in a lawful manner, Fish & Game chief executive Bryce Johnson said.
"Consent examples we had reviewed showed Horizons was issuing multiple consents for intensive farming with N [nitrogen] leaching figures significantly over those identified as necessary to achieve the plan's water quality outcomes.
"The court found Horizons' implementation has been unlawful and its decisions fundamentally deficient and that raises questions about what it is going to do about it," Mr Johnson said.
The Environment Court's focus was on the implementation of rules which reduced leaching of nutrients from farms and Mr Gordon said the regional council would need some time to read the court's 81-page findings so that they could fully understand the outcome.
"In order to ensure consent applications are in line with the decision, and to give Horizons time to consider if they would like to respond, new applications will be suspended for the next 12 weeks.
"This includes those currently in the system for processing," he said.
"Through regulatory and non-regulatory measures, farmers have been making good progress in nutrient management and environmental outcomes.
"We respect farmers will be looking for certainty as we move forward and staff will continue to be in contact with them as we work through this next phase.
"The One Plan was New Zealand's first regulatory plan applied at this scale.
"We respect we may not have got it completely right, however no one has said that we're not on the right path when it comes to water quality improvement. Some groups have simply indicated that they would like to see faster implementation.
"Based on the decisions as they currently stand, we foresee a longer, more involved and costly consent application process.
"It is unclear what this will achieve in terms of water quality, which is disappointing given we were on track for reducing in excess of 200 tonnes of nitrogen once all of the estimated 400 consents for dairy farms had been processed.
"Horizons has a significant monitoring programme across the region, with 10 years of water quality trends [January 2006-December 2015], 58 per cent of the 36 sites monitored for total oxidised nitrogen [TON] show improvement.
"None are in decline. In the Manawatu Catchment, 16 sites have improving trends for TON and none are declining.
"In the Manawatu there are also no declining trends for E.coli, sediment, and dissolved reactive phosphorus."
Horizons strategy and regulation manager Nic Peet said the court's decision would be useful for clarifying relationships between different sections of the Resource Management Act (RMA) and how Horizons' One Plan intersected with them.
"What the court judgment does do is clearly set out the legal requirements for consent applicants and council in considering those consents.
"The judgment very specifically did not question the legality of the consents already issued by Horizons. It identifies process steps for future consents," Dr Peet said.
"Importantly, the judgment did not attempt to translate policy in the plans as rules and it also did not, as the parties had contended, say animals that urinate and defecate directly on to paddocks were to be considered as discharges under the Plan or Resource Management Act.
This decision will create some uncertainty for farmers, but first we must fully understand it and the implications.
"At all times, the regional council has sought to appropriately apply its plan in line with the RMA. Like any new piece of legislation, it's met some challenges along the way. The court process will help inform these challenges," Dr Peet said.
Fish & Game and the EDS want Horizons to stick to its original One Plan rules limiting leaching of nitrogen, but in 2013 the Tararua Community Economic Impact Society, at a heated public meeting in Dannevirke, presented figures showing the plan in its original form would create a $60 million hit on the district's economy.
The Economic Impact Society, headed by Te Rehunga dairy farmer Russell Phillips, worked to ensure changes in the plan, especially nutrient budgeting, would steer the district away from this potentially disastrous economic blow. Mr Phillips said at the time the One Plan as it stood put at risk the bankability of farms and main-street businesses.
Gary Taylor, chief executive of Environmental Defence Society, said they believed resource consents were being issued with no assessment of environmental effects, no assessment against the relevant One Plan or National Policy Statement on Freshwater Management, and instead applied an approach where consent had to be granted because of a council resolution.
"The Environment Court has agreed with our concerns and its findings, in issuing the declarations, confirm Horizons has not been interpreting and implementing its One Plan in conformity with the law," Mr Taylor said. The regional council had not been working within freshwater limits.
"The court's decision has significant ramifications for regional councils across the country. It has confirmed that simply because managing within freshwater limits has its difficulties, it doesn't mean councils can make up alternative approaches," he said. "We are relying on regional councils to do their job properly in implementing the freshwater reforms."