There was also the first appearance from those involved in a high profile, local campaign against the WCO - Bruce Mackay of Heinz Watties.
The agronomist told the tribunal he had lived and worked in Hawke's Bay's horticultural industry his entire life, and had attended every meeting of the Hawke's Bay Regional Council- led TANK project since 2012.
TANK was functioning very well, was a process which reflected the Hawke's Bay community, and addressed matters which the WCO did not. He argued the WCO was a "blunt instrument" which was not future focused, and offered no opportunity for changes.
"I'm perplexed as to why the applicants are so concerned about the time TANK consultation may take to achieve positive outcomes for all when the imposition of the [WCO] is locking the resource for all eternity.
"Surely time spent now regardless of how long, developing the best possible outcomes is better than closing the door forever."
He was heavily questioned by the tribunal on whether TANK was on track to report back on its findings in May next year, the public knowledge about a WCO, and on water storage.
When asked, Mr Mackay said there were parts of the WCO he agreed with - particularly relating to the upper river which flowed through a national park - but he had an issue with the WCOs prohibitions and restrictions.
"They're just untenable for Hawke's Bay".
Yesterday, Hastings District Council became the first local authority to speak at the hearing, with representation by Matthew Casey, who said the council had a "relatively neutral" stance on the hearing's first stage.
When asked, he agreed it was possible the WCO "could" sit alongside regional planning processes, however there were key concerns the council had about a WCO's impact.
This included that an order could limit water storage options, and that it was still unknown what hydraulic linkages the river had with the Heretaunga aquifer - which supplies all water on the Heretaunga Plains -and what this could mean.
Concern over the aquifer was echoed by local advocacy group Guardians of the Aquifer. Representative Pauline Doyle told the special tribunal they supported the WCO as it offered an "enduring life of protection", unlike the short term of a regional plan.
"[The Ngaruroro] has major social and cultural significance for Hawke's Bay, especially when you take into its account its underground river systems which feed into the Heretaunga aquifer, the lifeblood of our region."
The tribunal also heard from Massey University Associate Professor Christine Cheyne, who supported the application as a way to protect the ecological, and recreational values of the Ngaruroro, arguing "we must not compromise future generations needs".
The Hasting resident said a WCO would help improve the river ecosystem and aquifer on which the region's current, and future populations health, and economy were dependant.
The professor of planning also argued it should be seen as supporting the regional council in their efforts to protect the water resource.
