Gisborne's Cameron Road groundwater monitoring bores and surface water ponding is visible due to high water levels in the shallow Te Hapara Sand aquifer. Photo: Facebook / Tairāwhiti Civil Defence
The significant rainfall that has already fallen in Gisborne this year has left the region vulnerable and its aquifer at, or even above, ground level.
According to the Gisborne District Council, aquifers are "porous geological formations, often gravel and sand which act like a sponge, soaking up and storing water".
The council's environmental monitoring team leader Peter Hancock told Morning Report successive rain events had filled up its aquifer, leaving the region much more vulnerable to surface flooding.
"The water levels are just so high." Gisborne District Council's Peter Hancock
Some sites had received over a metre and a half of rain so far this year, and while the aquifer could hold a lot of water, Hancock said rain events since Cyclone Gabrielle had been "the straw that broke the camels back".
If the city was to get a significant rainfall event, Hancock said that water does not have the opportunity to drain through the soil and into the aquifer.
"The aquifer levels are so high that those puddles that you might see accumulating during these rain events are actually sitting right on top of the aquifer so they don't get a lot of time to seep lower.
"The water levels are just so high."
Hancock said they were seeing some unusual things around town such as water ponding where it never had before and springs people had not seen before.
The aquifer's water levels were dropping at a rate of about 6 centimetres a day, and it could take until May for it to get back to normal.
But Hancock said it was "like two steps forward, one step back" as any rainfall caused it to rise again.
"Probably needless to say, I am sure we have all heard this quite often, we are looking forward to a dry spell and we have had enough rain and we could do with a break."
He said it would reduce the risk load.