In March 2021 we started the first of a three-stage process to build several raingardens to treat and filter stormwater runoff before it enters the Lake Te Koo Utu. This project aims to reduce the pollution entering the lake and improve the water quality.
A raingarden looks like any other traditional garden on the surface, but under the soil, there are layers of various media and plant roots that act as natural filters for surface runoff. Pooled water will slowly pass through allowing the plant roots and different media layers to filter out fine particles, hydrocarbons and other pollutants before they enter the environment.
The gardens help provide a place for stormwater runoff (rain) to soak into the ground allowing a natural filtration process to remove contaminants such as oil, petrol, zinc, and rubber from cars which are collected in stormwater runoff and eventually make their way into the lake.
Installing raingardens is one of our early approaches to begin improving water quality over the next 20 years as a part of the Lake Te Koo Utu concept plan. Funds for the design and installation costs were allocated within the 2021-31 Long Term Plan.
Raingardens are an inexpensive, simple and environmentally sound solution to urban stormwater runoff. They can also help play an important role in protecting habitat and helping with climate resiliency.
Plants used
A combination of native, perennial and flowering plants work best for it to functional well.
The plants used will often have deep roots and be able to tolerate extended dry periods and heavy rains. Planting a raingarden helps to reduce local flooding, recharge groundwater sources and remove runoff pollutants.
