Specialist New Zealand Defence Force staff will be checking Tonga's shipping lanes are passable and the wharf is safe so desperately needed humanitarian supplies can get through.
Three deaths have been confirmed after Saturday's massive volcanic eruption. There are reports of significant injuries, but no details yet.
UN officials said 84,000 people - more than 80 percent of Tonga's population - had been impacted by tsunami and the ashfall that followed the eruption.
New Zealand Defence Force Rear Admiral Jim Gilmour said there were fears for food security, with reports ash was killing crops.
Ash and sea water have also contaminated water supplies.
Offshore patrol vessel HMNZS Wellington, which is carrying a helicopter, technical gear, and teams, has arrived in Tongan waters.
"They commenced clearing the outer part of the Nuku'alofa harbour and they'll be working in towards the wharf area and terminal area," Gilmour told Morning Report.
It will scope the shipping channels and wharves at the main port to see if they safe enough to use to drop off supplies, in time for HMNZS Aotearoa due today, which is carrying a range of stores including water, long life non-perishable foods, hygiene kits and shelter.
"Water is among the highest priorities for Tonga, and the Aotearoa can carry 250,000 litres, and produce 70,000 litres per day through a desalination plant," Gilmour said.
"I feel that the most value that she's going to provide today is bring able to discharge fresh water into water tanks for distribution around Tongatapu."
Gilmour said staff did not need to set foot on Tonga at all, in an effort to avoid spreading Covid-19 to the currently coronavirus-free country.
Sanitised containers will be moved by crane from the ship onto the dock or hauled by personnel in full PPE.
They will then withdraw and Tongans will pick up the goods.
Hundreds of people, including the Tongan Armed Forces, cleared ash off the international runway allowing a Defence Force Hercules to land yesterday afternoon.
It carried the most urgently needed supplies including water containers, temporary shelters, generators, and communications equipment.
It was expected to be on the ground for about 90 minutes before returning to New Zealand.
The Hercules will be decontaminated today with a plan to head out again tomorrow, Gilmour said.
He said ash that was moved off the runway was sitting nearby and in a fine powder form. Some of this was picked up in the wind.
'I'm 100 percent confident that none of our deployed forces have Covid' - New Zealand Defence Force Rear Admiral Jim Gilmour
HMNZS Aotearoa was due to arrive in Tonga on Friday with water supplies. Photo: Supplied / NZDF
A Royal Australian Air Force C-17 also landed on Thursday.
A third New Zealand Defence Force vessel, HMNZS Canterbury, is being prepared to be deployed this evening or on Saturday to arrive on Tuesday.
It is carrying two helicopters which can be used to distribute supplies and survey Tonga's outer islands.
The Defence Force intends to be self sufficient to not put pressure on Tonga's food, water and fuel supply.
It has enough stores to stay at sea for at least 30 days without any external assistance. If it stays that long plans will be made to resupply.
"We're very mindful of the sensitivities about Covid and its transmission. I'm 100 percent confident that none of our deployed forces have Covid, they've all been PCR tested, at least double jabbed, some, if not many triple jabbed," Gilmour said.
He said the NZDF respects Tonga's decision whether or not to allow troops on the ground.
"If Tonga decides that they would like boots on the ground and our operators will be operating ashore, then will will do that and obviously still maintain a contactless approach delivering any assistance that is required."
Australia's high commissioner to Tonga Rachael Moore has described the loss of property as "catastrophic".
Tonga's Prime Minister Siaosi Sovaleni (right) joined by Australia's High Commissioner to Tonga Rachael Moore (left) to witness the arrival of the first Royal Australian Air Force C-17A Globemaster III aircraft from Australia delivering humanitarian assistance on January 20, 2022. Photo: Handout / Australian Defence Force / AFP
"Along the western beaches there is a moonscape where once beautiful resorts and many, many homes stood," Moore said.
Tonga has only just begun to re-establish global contact after five days cut off from the rest of the world.
Mobile phone company Digicel has confirmed re-establishing communications between Tonga and the rest of the world, but lines have been clogged with heavy traffic, leaving many still unable to get through to loved ones.
Work to improve the satellite capacity and improve communications at the New Zealand High Commission in Nuku'alofa was being done Thursday evening.
Food and water woes
MP for Panmure-Ōtāhuhu and the co-chairperson of the Aotearoa-Tonga Relief Committee Jenny Salesa said Tongans in New Zealand were hearing from their families back home for food and bottled water.
"We're also told by some of our relatives that the ash from the volcano is everywhere. A lot of the ash has now hardened like cement on some of the surfaces and cleaning up is a challenging task.
"Some of the worry is that it would also affect the crops and the traditional food sources that a lot of our Tongan people back home rely on."
The relief committee is asking families from the most effected islands to head to the appeal at Mt Smart Stadium today. People from the rest of Tonga are asked to come from Sunday.
Each family being allocated a 44-gallon drum to send supplies to Tonga and eight containers have been given to the relief committee.
- RNZ / ABC / BBC / Reuters