Slips have cut off the water supply to Pohara Valley in Golden Bay, while the main water pipeline to Nelson has been threatened by more than half a dozen slips.
Nelson Tasman Civil Defence controller Jim Frater said more than 300 slips were being monitored, particularly those in built-up areas, with some still moving.
"We're keeping an eye on the weather and towards the end of the week it looks like we could have some more bad weather, and while the land is in that position, there is still a potential for further slipping,'' he told Radio New Zealand today.
The Pohara Valley water supply had been almost completely wiped out, but was expected to be up and running again by Wednesday.
"It won't necessarily be a potable water supply, which means they'll have to boil, but there will definitely be a water supply there.''
The No.1 priority was the Maitai Valley pipeline that service Nelson, which had suffered damage from several slips.
"It's particularly important because we've got a holiday season coming through and the last thing we want to have is to be water rationing.
"We have asked people to conserve water in the Richmond area because there has been a pump that has electrical problems, and that's affecting our ability to pump to other areas.''
If the Maitai pipeline did fail, water would be have to be pumped from Richmond.
Nelson Mayor Aldo Miccio told Radio New Zealand this morning the water situation was still precarious.
A helicopter flight over the weekend found there has been about eight slips under the Maitai pipeline.
"We've had engineers walk the entire length of the actual pipeline and there has been a couple of spots that are a threat if there are further slips, but the rest is stable and we are getting workers up there to stabilise weak spots.''
Mr Miccio said there were contingencies in place, with secondary dams stocked with water just in case the pipeline is broken.
"There will be water but it would be rationed if the pipeline was to go.''
Another 30 homes were evacuated from Grenville Terrace above Rocks Road in Nelson yesterday, as the ground continues to move days after the deluge.
About 100 residents remain cut off following a slip at Cable Bay. Supplies are being airlifted in, while Civil Defence is hoping access can be opened up to the settlement within a week.
The state of emergency is in place until at least midnight Tuesday, although it is likely to be extended a further seven days.
State Highway 60 between Takaka and Collingwood is now open to one lane at Birds Hill, allowing milk tankers to get through to Golden Bay and holiday parks to reopen.
Abel Tasman Drive is open with some restrictions.
Rocks Rd remained closed, with Mr Miccio describing it as "quite a major problem''.
