Impacts of high groundwater
Next up in our closer look at groundwater, we breakdown the impacts of record rainfall over the last year causing significantly elevated groundwater levels across our district.
Average annual rainfall at the Paraparaumu Aerodrome is 1030 millimetres, but between August 2021 and August 2022, 1432 millimetres was recorded – the third highest annual total on record in over 80 years. Our water table is approximately 1 metre higher than it was at this time in 2021.
If you’ve looked out the window and seen ponding in your backyard during or after rain, you’re not alone. Current groundwater levels are impacting our land, infrastructure, and work programmes, as well as private property.
Roads and footpaths are degrading faster, pipes are being corroded, stormwater networks have diminished capacity and functionality, septic tanks are being infiltrated, and trees that can’t tolerate extended saturation are dying.
High groundwater levels are preventing or delaying access for maintenance, repairs, renewal works and capital works projects.
What can we do about it?
Unfortunately, there are no easy fixes but levels will drop given time. You can’t pump groundwater in the same way you can pump stormwater – there’s nowhere to pump it to, as it'll only return to the lowest lying areas.
We estimate we need 8–10 months without significant weather events to return to normal groundwater levels.
We’re working on a number of things to improve our stormwater network that will help the situation, too. This includes renewal and repairs, and continuing to work on our stormwater capital works programme.
Out of the 110 kilometres of open waterways in our district, we manage approximately 40 kilometres; Greater Wellington Regional Council is responsible for managing the rest. As part of our planned asset maintenance, we clear waterways regularly, so there's no flow restrictions during flooding. We also check our piped network using CCTV cameras, and clear blockages and carry out necessary repairs.
If you experience standing water on your property, please be patient while it recedes. You can call a plumber or drainlayer for more advice.