Mike Hosking grills outgoing Watercare chief executive Raveen Jaduram

Outgoing Watercare chief executive Raveen Jaduram has defended the company's grant to take on an extra 100 million litres of water daily from the Waikato River.

It comes amid fears of a severe water shortage following Auckland's worst recorded drought and the prospect of looming water restrictions this summer.

With the river currently above median flow, Watercare already has consents to take 175 million litres a day (MLD) from the river, which is the maximum its Waikato Water Treatment Plant in Tūākau can currently treat and deliver.

An application Watercare lodged in May for an additional 100 MLD has now been granted by Waikato Regional Council. It enables Watercare to take the extra water between May and September (inclusive), and at other times of the year when the river is above median flow.

Waikato Regional Council has also granted consent for Watercare to use the 25 MLD shared by Hamilton City Council.

When asked by Newstalk ZB host Mike Hosking who was going to fund the extra water, Jaduram said it was the Government's position that Watercare need not have to.

"We are not paying for water at all. We have never paid for water.

"Another 100 million litres of water is a substantial volume of water. Currently we are taking in 175 million litres a day and the demand at the moment in Auckland is just under 400 million a day.

"Given that we have been in a drought, and we don't know how long this will continue, this 100 million litres a day will see us through if we had another drought similar to what we have again next year."

Hosking called Jaduram and Watercare's efforts to minimise the risk of drought "useless", and asked why Auckland still don't have a drought-proof water system.

"That's a very good question, and that's a question we would like to answer now given the standard we are using was set by the council after the '93-'94 drought and we haven't had restrictions since then," Jaduram said.

"We have been building the infrastructure in Auckland to meet the demand. You and many, many other Aucklanders want a higher reliability than what we have got at the moment.

"We haven't been useless and we haven't mismanaged the situation. There is always going to be an earthquake that's going to cause a building to collapse, or if you put in stormwater systems, they're always going to be a flood that will cause flooding.

"This drought is potentially worse than the drought than our standard is able to cope with.

"We need a higher level of security for Auckland and that is a decision we need Auckland Council to make for us. We haven't been banging on anyone's desk, and that is something in hindsight we needed.

"We are not in the fault game."

Jaduram leaves Watercare on October 31, having been with the company since 2014. He has had to endure flak over the water crisis, brought about by the worst drought in the city's history.

This led to emergency spending of $224 million to bolster the city's water supply, restrictions on using hoses and water blasters outdoors and a four-minute limit on showers.