"We submit that it is unusual to find a catchment that supports such a wide range of high quality and co-existing characteristics," Eveleigh said.
"That is a product of its pristine upper waters, the structure and changeable nature of the braiding in its lower reaches, its high water quality from source to sea, the absence of dams, and the rendition of sufficient in stream flow to support those valued characteristics.
"It is indeed unusual and...nationally outstanding."
She said the rivers had a number of outstanding characteristics, including environmental, cultural, spiritual and tikanga Maori values, and tourism uses, including jet boating.
"The applicants have sought that the habitat afforded by the Ngaruroro be recognised as outstanding for indigenous fish and birds."
She said many submitters appeared to not understand what a WCO would do.
She said a WCO cannot affect existing consents, or activates currently allowed under the councils long term plan. However, new consents would be assessed by both the LTP and the WCO, and when a regional plan is changed it cannot be inconsistent with the WCO.
"The time of authorising further degradation of New Zealand rivers, particularly those highly valued for their ecological and recreation features, has passed."
She said some people thought the applicants were an unusual group of people, including people promoting habitat protection, fishers, whitewater recreation, jet boating and cultural values.
The WCO is opposed by various groups, including Horticulture New Zealand, Federated Farmers, winegrowers and Hawke's Bay Regional Council.
Presentations from those opposing the WCO will begin on Thursday, February 28.
Six organisations have made an application to the EPA asking for a WCO on the two rivers. They are: Forest and Bird, New Zealand Fish and Game Council, Hawke's Bay Fish and Game Council, Operation Patiki Ngāti Hori ki Kohupatiki, Whitewater NZ Incorporated and Jet Boating New Zealand.
The case is being heard in front of a special tribunal, chaired by Richard Fowler.
A hearing for a WCO on the upper Ngaruroro River was held in 2017, but a decision deferred until the hearing for the lower Ngaruroro had been held.